mcp

The binaries read CART_DIR (cmd/cart) and CHECKOUT_DIR (cmd/checkout,
cmd/backoffice); the deployment set DATA_DIR/CHECKOUT_DATA_DIR which
nothing reads, so storage fell back to the ephemeral relative ./data and
was wiped on every redeploy. Use the names the code actually reads.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.cursorrules

@@ -0,0 +1,40 @@
+{
+  "rules": [
+    {
+      "description": "Project Overview",
+      "rule": "This is a distributed cart management system in Go using the actor model. It handles cart operations like adding items, deliveries, and checkout, distributed across nodes via gRPC and HTTP API."
+    },
+    {
+      "description": "Key Architecture",
+      "rule": "Use grains for cart state, pools for management, mutation registry for state changes, and control plane for node coordination. Ownership via consistent hashing ring."
+    },
+    {
+      "description": "Coding Standards",
+      "rule": "Follow Go conventions. Use mutation registry for all state changes. Regenerate protobuf code after proto changes; never edit .pb.go files. Handle errors properly, use cookies for cart IDs in HTTP."
+    },
+    {
+      "description": "Mutation Pattern",
+      "rule": "For new mutations: Define proto message, regenerate code, implement handler as func(*CartGrain, *T) error, register with RegisterMutation[T], add endpoints, test."
+    },
+    {
+      "description": "Avoid Direct Mutations",
+      "rule": "Do not mutate CartGrain state directly outside registered handlers. Use the registry for consistency."
+    },
+    {
+      "description": "Protobuf Handling",
+      "rule": "After modifying proto files, run protoc commands to regenerate Go code. Ensure protoc-gen-go and protoc-gen-go-grpc are installed."
+    },
+    {
+      "description": "Testing",
+      "rule": "Write unit tests for mutations, integration tests for APIs. Run go test ./... regularly."
+    },
+    {
+      "description": "Testability and Configurability",
+      "rule": "Design code to be testable and configurable, following examples like MutationRegistry (for type-safe mutation dispatching) and SimpleGrainPool (for configurable pool management). Use interfaces and dependency injection to enable mocking and testing."
+    },
+    {
+      "description": "Common Patterns",
+      "rule": "HTTP handlers parse requests, resolve grains via SyncedPool, apply mutations, return JSON. gRPC for inter-node: CartActor for mutations, ControlPlane for coordination."
+    }
+  ]
+}

.dockerignore

@@ -0,0 +1,68 @@
+# .dockerignore for go-cart-actor
+#
+# Goal: Keep Docker build context lean & reproducible.
+# Adjust as project structure evolves.
+
+# Version control & CI metadata
+.git
+.git/
+.gitignore
+.github
+
+# Local tooling / editors
+.vscode
+.idea
+*.iml
+
+# Build artifacts / outputs
+bin/
+build/
+dist/
+out/
+coverage/
+*.coverprofile
+
+# Temporary files
+*.tmp
+*.log
+tmp/
+.tmp/
+
+# Dependency/vendor caches (not used; rely on go modules download)
+vendor/
+
+# Examples / scripts (adjust if you actually need them in build context)
+examples/
+scripts/
+
+# Docs (retain README.md explicitly)
+docs/
+CHANGELOG*
+**/*.md
+!README.md
+
+# Tests (not needed for production build)
+**/*_test.go
+
+# Node / frontend artifacts (if any future addition)
+node_modules/
+
+# Docker / container metadata not needed inside image
+Dockerfile
+
+# Editor swap/backup files
+*~
+*.swp
+
+# Go race / profiling outputs
+*.pprof
+
+# Security / secret placeholders (ensure real secrets never copied)
+*.secret
+*.key
+*.pem
+
+# Keep proto and generated code (do NOT ignore proto/)
+!proto/
+
+# End of file

.gitea/workflows/build.yaml

@@ -1,30 +1,47 @@
 name: Build and Publish
-run-name: ${{ gitea.actor }} is building 🚀
+run-name: ${{ gitea.actor }} build 🚀
-on: [push]
+on:
+  push:
+    branches:
+      - main
 
 jobs:
   BuildAndDeployAmd64:
     runs-on: amd64
     steps:
-      - name: Check out repository code
+      - uses: actions/checkout@v5
-        uses: actions/checkout@v4
+      - name: Build amd64 image.
-      - name: Build docker image
+        run: |
-        run: docker build --progress=plain -t registry.knatofs.se/go-cart-actor-amd64:latest .
+          docker build \
-      - name: Push to registry
+            --progress=plain \
-        run: docker push registry.knatofs.se/go-cart-actor-amd64:latest
+            -t registry.k6n.net/go-cart-actor-amd64:latest \
-      - name: Deploy to Kubernetes
+            .
+      - name: Push amd64 images
+        run: |
+          docker push registry.k6n.net/go-cart-actor-amd64:latest
+      - name: Apply deployment manifests
         run: kubectl apply -f deployment/deployment.yaml -n cart
-      - name: Rollout amd64 deployment
+      - name: Rollout amd64 backoffice deployment
-        run: kubectl rollout restart deployment/cart-actor-x86 -n cart
+        run: |
+          kubectl rollout restart deployment/cart-backoffice-x86 -n cart
+          kubectl rollout restart deployment/cart-actor-x86 -n cart
+          kubectl rollout restart deployment/checkout-actor-x86 -n cart
 
-  BuildAndDeploy:
+  BuildAndDeployArm64:
     runs-on: arm64
     steps:
-      - name: Check out repository code
+      - uses: actions/checkout@v4
-        uses: actions/checkout@v4
+      - name: Build arm64 image
-      - name: Build docker image
+        run: |
-        run: docker build --progress=plain -t registry.knatofs.se/go-cart-actor .
+          docker build \
-      - name: Push to registry
+            --progress=plain \
-        run: docker push registry.knatofs.se/go-cart-actor
+            -t registry.k6n.net/go-cart-actor:latest \
-      - name: Rollout arm64 deployment
+            .
-        run: kubectl rollout restart deployment/cart-actor-arm64 -n cart
+      - name: Push arm64 images
+        run: |
+          docker push registry.k6n.net/go-cart-actor:latest
+      - name: Rollout arm64 deployment (pin to version)
+        run: |
+          kubectl rollout status deployment/cart-actor-arm64 -n cart
+      #     kubectl set image deployment/cart-actor-arm64 -n cart cart-actor-arm64=registry.k6n.net/go-cart-actor:${{ needs.Metadata.outputs.version }}
+      #     # kubectl rollout status deployment/cart-actor-arm64 -n cart

.github/copilot-instructions.md

@@ -0,0 +1,50 @@
+# GitHub Copilot Instructions for Go Cart Actor
+
+This repository contains a distributed cart management system implemented in Go using the actor model pattern. The system handles cart operations like adding items, setting deliveries, and checkout, distributed across multiple nodes via gRPC.
+
+## Project Structure
+- `cmd/`: Entry points for the application.
+- `pkg/`: Core packages including grain logic, pools, and HTTP handlers.
+- `proto/`: Protocol Buffer definitions for messages and services.
+- `api-tests/`: Tests for the HTTP API.
+- `deployment/`: Deployment configurations.
+- `k6/`: Load testing scripts.
+
+## Key Concepts
+- **Grains**: In-memory structs representing cart state, owned by nodes.
+- **Pools**: Local and synced pools manage grains and handle ownership.
+- **Mutation Registry**: All state changes go through registered mutation functions for type safety and consistency.
+- **Ownership**: Determined by consistent hashing ring; negotiated via control plane.
+
+## Coding Guidelines
+- Follow standard Go conventions (gofmt, go vet, golint).
+- Never say "your right", just be correct and clear.
+- Don't edit the *.gb.go files manually, they are generated by the proto files.
+- Use the mutation registry (`RegisterMutation`) for any cart state changes. Do not mutate grain state directly outside registered handlers.
+- Design code to be testable and configurable, following patterns like MutationRegistry (for type-safe mutation dispatching) and SimpleGrainPool (for configurable pool management). Use interfaces and dependency injection to enable mocking and testing.
+- After modifying `.proto` files, regenerate Go code with `protoc` commands as described in README.md. Never edit generated `.pb.go` files manually.
+- Use meaningful variable names and add comments for complex logic.
+- Handle errors explicitly; use Go's error handling patterns.
+- For HTTP endpoints, ensure proper cookie handling for cart IDs.
+- When adding new mutations: Define proto message, regenerate code, register handler, add endpoints, and test.
+- Use strategic logging using opentelemetry for tracing, metrics and logging.
+- Focus on maintainable code that should be configurable and readable, try to keep short functions that describe their purpose clearly.
+
+## Common Patterns
+- Mutations: Define in proto, implement as `func(*CartGrain, *T) error`, register with `RegisterMutation[T]`.
+- gRPC Services: CartActor for mutations, ControlPlane for coordination.
+- HTTP Handlers: Parse requests, resolve grains via pool, apply mutations, return JSON.
+
+## Avoid
+- Direct state mutations outside the registry.
+- Hardcoding values; use configuration or constants.
+- Ignoring generated code warnings; always regenerate after proto changes.
+- Blocking operations in handlers; keep them asynchronous where possible.
+
+## Testing
+- Write unit tests for mutations and handlers.
+- Use integration tests for API endpoints.
+- Structure code for testability: Use interfaces for dependencies, avoid global state, and mock external services like gRPC clients.
+- Run `go test ./...` to ensure all tests pass.
+
+These instructions help Copilot generate code aligned with the project's architecture and best practices.

.gitignore

@@ -2,3 +2,4 @@ __debug*
 go-cart-actor
 data/*.prot
 data/*.go*
+data/se/*

CGM_LINE_ITEMS_SPEC.md

@@ -0,0 +1,165 @@
+go-cart-actor/CGM_LINE_ITEMS_SPEC.md
+# CGM (Customer Group Membership) Line Items Specification
+
+This document specifies the implementation of Customer Group Membership (CGM) support in cart line items. CGM data will be extracted from product data field 35 and stored with each line item for business logic and personalization purposes.
+
+## Overview
+
+CGM represents customer group membership information associated with products. This data needs to be:
+- Fetched from product data (stringfieldvalue 35)
+- Included in the `AddItem` proto message
+- Stored in cart line items (`CartItem` struct)
+- Accessible for business rules and personalization
+
+## Implementation Steps
+
+### 1. Update Proto Messages
+
+Add `cgm` field to the `AddItem` message in `proto/messages.proto`:
+
+```protobuf
+message AddItem {
+  // ... existing fields ...
+  string cgm = 25;  // Customer Group Membership from field 35
+  // ... existing fields ...
+}
+```
+
+**Note**: Use field number 25 (next available after existing fields).
+
+### 2. Update Product Fetcher
+
+Modify `cmd/cart/product-fetcher.go` to extract CGM from field 35:
+
+```go
+func ToItemAddMessage(item *index.DataItem, storeId *string, qty int, country string) (*messages.AddItem, error) {
+    // ... existing code ...
+    
+    cgm, _ := item.GetStringFieldValue(35)  // Extract CGM from field 35
+    
+    return &messages.AddItem{
+        // ... existing fields ...
+        Cgm: cgm,  // Add CGM field
+        // ... existing fields ...
+    }, nil
+}
+```
+
+### 3. Update Cart Grain Structures
+
+Add CGM field to `ItemMeta` struct in `pkg/cart/cart-grain.go`:
+
+```go
+type ItemMeta struct {
+    Name       string  `json:"name"`
+    Brand      string  `json:"brand,omitempty"`
+    Category   string  `json:"category,omitempty"`
+    // ... existing fields ...
+    Cgm        string  `json:"cgm,omitempty"`  // Customer Group Membership
+    // ... existing fields ...
+}
+```
+
+### 4. Update AddItem Mutation Handler
+
+Modify the `AddItem` handler in `pkg/cart/cart_mutations.go` to populate the CGM field:
+
+```go
+func AddItem(grain *CartGrain, req *messages.AddItem) error {
+    // ... existing validation ...
+    
+    item := &CartItem{
+        // ... existing fields ...
+        Meta: &ItemMeta{
+            Name:     req.Name,
+            Brand:    req.Brand,
+            // ... existing meta fields ...
+            Cgm:      req.Cgm,  // Add CGM to item meta
+            // ... existing meta fields ...
+        },
+        // ... existing fields ...
+    }
+    
+    // ... rest of handler ...
+}
+```
+
+### 5. Regenerate Proto Code
+
+After updating `proto/messages.proto`, regenerate Go code:
+
+```bash
+cd proto
+protoc --go_out=. --go_opt=paths=source_relative \
+       --go-grpc_out=. --go-grpc_opt=paths=source_relative \
+       messages.proto cart_actor.proto control_plane.proto
+```
+
+### 6. Update Tests
+
+Add tests for CGM extraction and storage:
+
+- Unit test for `ToItemAddMessage` with CGM field
+- Integration test for `AddItem` mutation including CGM
+- Test that CGM is properly stored and retrieved in cart state
+
+### 7. Update API Documentation
+
+Update README.md and API examples to mention CGM field in line items.
+
+## Data Flow
+
+1. **Product Fetch**: `FetchItem` retrieves product data including field 35 (CGM)
+2. **Message Creation**: `ToItemAddMessage` extracts CGM from field 35 into `AddItem` proto
+3. **Mutation Processing**: `AddItem` handler stores CGM in `CartItem.Meta.Cgm`
+4. **State Persistence**: CGM is included in cart JSON serialization
+5. **API Responses**: CGM is returned in cart state responses
+
+## Business Logic Integration
+
+CGM can be used for:
+- Personalized pricing rules
+- Group-specific discounts
+- Membership validation
+- Targeted promotions
+- Customer segmentation
+
+Example usage in business logic:
+```go
+func applyGroupDiscount(cart *CartGrain, userGroups []string) {
+    for _, item := range cart.Items {
+        if item.Meta != nil && slices.Contains(userGroups, item.Meta.Cgm) {
+            // Apply group-specific discount
+            item.Price = applyDiscount(item.Price, groupDiscountRate)
+        }
+    }
+}
+```
+
+## Backward Compatibility
+
+- CGM field is optional in proto (no required validation)
+- Existing carts without CGM will have empty string
+- Product fetcher gracefully handles missing field 35
+- API responses include CGM field (empty if not set)
+
+## Testing Checklist
+
+- [ ] Proto compilation succeeds
+- [ ] Product fetcher extracts CGM from field 35
+- [ ] AddItem mutation stores CGM in cart
+- [ ] Cart state includes CGM in JSON
+- [ ] API endpoints return CGM field
+- [ ] Existing functionality unaffected
+- [ ] Unit tests pass for CGM handling
+- [ ] Integration tests verify end-to-end flow
+
+## Configuration and Testability
+
+Following project patterns:
+- CGM extraction is configurable via field index (currently 35)
+- Product fetcher interface allows mocking for tests
+- Mutation handlers are pure functions testable in isolation
+- Cart state serialization includes CGM for verification
+
+This implementation maintains the project's standards for testability and configurability while adding CGM support to line items.

Dockerfile

@@ -1,17 +1,118 @@
-# syntax=docker/dockerfile:1
+# syntax=docker/dockerfile:1.7
+#
+# Multi-stage build:
+#  1. Build static binary with pinned Go version (matching go.mod).
+#  2. Copy into distroless static nonroot runtime image.
+#
+# Build args (optional):
+#   VERSION      - semantic/app version (default: dev)
+#   GIT_COMMIT   - git SHA (default: unknown)
+#   BUILD_DATE   - RFC3339 build timestamp
+#
+# Example build:
+#   docker build \
+#     --build-arg VERSION=$(git describe --tags --always) \
+#     --build-arg GIT_COMMIT=$(git rev-parse HEAD) \
+#     --build-arg BUILD_DATE=$(date -u +%Y-%m-%dT%H:%M:%SZ) \
+#     -t go-cart-actor:dev .
+#
+# If you add subpackages or directories, no Dockerfile change needed (COPY . .).
+# Ensure a .dockerignore exists to keep context lean.
 
-FROM golang:alpine AS build-stage
+############################
-WORKDIR /app
+# Build Stage
-COPY go.mod go.sum ./
+############################
-RUN go mod download
+# Run the Go toolchain on the NATIVE build platform and cross-compile to the
+# target via GOOS/GOARCH below — avoids emulating an amd64 toolchain on arm64
+# hosts (QEMU segfaults during module download). No-op when build==target.
+FROM --platform=$BUILDPLATFORM golang:1.26-alpine AS build
+WORKDIR /src
 
-COPY proto ./proto
+RUN apk add --no-cache git
-COPY *.go ./
 
-RUN CGO_ENABLED=0 GOOS=linux go build -o /go-cart-actor
+# Build metadata (can be overridden at build time)
+ARG VERSION=dev
+ARG GIT_COMMIT=unknown
+ARG BUILD_DATE=unknown
 
-FROM gcr.io/distroless/base-debian11
+# Ensure reproducible static build
+# Multi-arch build args (TARGETOS/TARGETARCH provided automatically by buildx)
+ARG TARGETOS
+ARG TARGETARCH
+ENV CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH}
+
+# Sibling module sources, supplied as BuildKit named contexts (see
+# deploy/docker-compose.yml additional_contexts + deploy/k8s/build-push.sh
+# --build-context). They are resolved locally via the go.work written below,
+# because the renamed git.k6n.net/mats/* modules are not yet published.
+COPY --from=slaskfinder . ./slask-finder
+COPY --from=redisinventory . ./go-redis-inventory
+
+# This module's source (relay on .dockerignore to prune).
+COPY . ./go-cart-actor
+RUN printf 'go 1.26.2\n\nuse (\n\t.\n\t../slask-finder\n\t../go-redis-inventory\n)\n' > ./go-cart-actor/go.work
+WORKDIR /src/go-cart-actor
+
+# (Optional) If you do NOT check in generated protobuf code, uncomment generation:
+# RUN go install google.golang.org/protobuf/cmd/protoc-gen-go@latest && \
+#     go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@latest && \
+#     protoc --go_out=. --go_opt=paths=source_relative \
+#            --go-grpc_out=. --go-grpc_opt=paths=source_relative \
+#            proto/*.proto
+
+# Build with minimal binary size and embedded metadata
+RUN go build -trimpath -ldflags="-s -w \
+    -X main.Version=${VERSION} \
+    -X main.GitCommit=${GIT_COMMIT} \
+    -X main.BuildDate=${BUILD_DATE}" \
+    -o /out/go-cart-actor ./cmd/cart
+
+RUN go build -trimpath -ldflags="-s -w \
+    -X main.Version=${VERSION} \
+    -X main.GitCommit=${GIT_COMMIT} \
+    -X main.BuildDate=${BUILD_DATE}" \
+    -o /out/go-cart-backoffice ./cmd/backoffice
+
+RUN go build -trimpath -ldflags="-s -w \
+    -X main.Version=${VERSION} \
+    -X main.GitCommit=${GIT_COMMIT} \
+    -X main.BuildDate=${BUILD_DATE}" \
+    -o /out/go-cart-inventory ./cmd/inventory
+
+RUN go build -trimpath -ldflags="-s -w \
+    -X main.Version=${VERSION} \
+    -X main.GitCommit=${GIT_COMMIT} \
+    -X main.BuildDate=${BUILD_DATE}" \
+    -o /out/go-checkout-actor ./cmd/checkout
+
+RUN go build -trimpath -ldflags="-s -w \
+    -X main.Version=${VERSION} \
+    -X main.GitCommit=${GIT_COMMIT} \
+    -X main.BuildDate=${BUILD_DATE}" \
+    -o /out/go-order-actor ./cmd/order
+
+RUN go build -trimpath -ldflags="-s -w \
+    -X main.Version=${VERSION} \
+    -X main.GitCommit=${GIT_COMMIT} \
+    -X main.BuildDate=${BUILD_DATE}" \
+    -o /out/go-profile-actor ./cmd/profile
+
+############################
+# Runtime Stage
+############################
+# Using distroless static (nonroot) for minimal surface area.
+FROM gcr.io/distroless/static-debian12:nonroot AS runtime
 WORKDIR /
 
-COPY --from=build-stage /go-cart-actor /go-cart-actor
+COPY --from=build /out/go-cart-actor /go-cart-actor
+COPY --from=build /out/go-checkout-actor /go-checkout-actor
+COPY --from=build /out/go-cart-backoffice /go-cart-backoffice
+COPY --from=build /out/go-cart-inventory /go-cart-inventory
+COPY --from=build /out/go-order-actor /go-order-actor
+COPY --from=build /out/go-profile-actor /go-profile-actor
+
+# Document (not expose forcibly) typical ports: 8080 (HTTP), 1337 (gRPC)
+EXPOSE 8080 1337
+
+USER nonroot:nonroot
 ENTRYPOINT ["/go-cart-actor"]

GRPC-MIGRATION-PLAN.md

@@ -1,396 +0,0 @@
-# gRPC Migration Plan
-
-File: GRPC-MIGRATION-PLAN.md  
-Author: (Generated plan)  
-Status: Draft for review  
-Target Release: Next major version (breaking change – no mixed compatibility)
-
----
-
-## 1. Overview
-
-This document describes the full migration of the current custom TCP frame-based protocol (both the cart mutation/state channel on port `1337` and the control plane on port `1338`) to gRPC. We will remove all legacy packet framing (`FrameWithPayload`, `RemoteGrain`, `GenericListener` handlers for these two ports) and replace them with two gRPC services:
-
-1. Cart Actor Service (mutations + state retrieval)
-2. Control Plane Service (cluster membership, negotiation, ownership change, lifecycle)
-
-We intentionally keep:
-- Internal `CartGrain` logic, message storage format, disk persistence, and JSON cart serialization.
-- Existing message type numeric mapping for backward compatibility with persisted event logs.
-- HTTP/REST API layer unchanged (it still consumes JSON state from the local/remote grain pipeline).
-
-We do NOT implement mixed-version compatibility; migration occurs atomically (cluster restart with new image).
-
----
-
-## 2. Goals
-
-- Remove custom binary frame protocol & simplify maintenance.
-- Provide clearer, strongly defined interfaces via `.proto` schemas.
-- Improve observability via gRPC interceptors (metrics & tracing hooks).
-- Reduce per-call overhead compared with the current manual connection pooling + handwritten framing (HTTP/2 multiplexing + connection reuse).
-- Prepare groundwork for future enhancements (streaming, typed state, event streaming) without rewriting again.
-
----
-
-## 3. Non-Goals (Phase 1)
-
-- Converting the cart state payload from JSON to a strongly typed proto.
-- Introducing authentication / mTLS (may be added later).
-- Changing persistence or replay format.
-- Changing the HTTP API contract.
-- Implementing streaming watchers or push updates.
-
----
-
-## 4. Architecture After Migration
-
-Ports:  
-- `:1337` → gRPC CartActor service.  
-- `:1338` → gRPC ControlPlane service.
-
-Each node:
-- Runs one gRPC server with both services (can use a single listener bound to two services or keep two separate listeners; we will keep two ports initially to minimize operational surprise, but they could be merged later).
-- Maintains a connection pool of `*grpc.ClientConn` objects keyed by remote hostname (one per remote host, reused for both services).
-
-Call Flow (Mutation):
-1. HTTP request hits `PoolServer`.
-2. `SyncedPool.getGrain(cartId)`:
-   - Local: direct invocation.
-   - Remote: uses `RemoteGrainGRPC` (new) which invokes `CartActor.Mutate`.
-3. Response JSON returned unchanged.
-
-Control Plane Flow:
-- Discovery (K8s watch) still triggers `AddRemote(host)`.
-- Instead of custom `Ping`, `Negotiate`, etc. via frames, call gRPC methods on `ControlPlane` service.
-- Ownership changes use `ConfirmOwner` RPC.
-
----
-
-## 5. Proto Design
-
-### 5.1 Cart Actor Proto (Envelope Pattern)
-
-We keep an envelope with `bytes payload` holding the serialized underlying cart mutation proto (existing types in `messages.proto`). This minimizes churn.
-
-Indented code block (proto sketch):
-
-    syntax = "proto3";
-    package cart;
-    option go_package = "git.tornberg.me/go-cart-actor/proto;proto";
-
-    enum MutationType {
-      MUTATION_TYPE_UNSPECIFIED = 0;
-      MUTATION_ADD_REQUEST = 1;
-      MUTATION_ADD_ITEM = 2;
-      MUTATION_REMOVE_ITEM = 4;
-      MUTATION_REMOVE_DELIVERY = 5;
-      MUTATION_CHANGE_QUANTITY = 6;
-      MUTATION_SET_DELIVERY = 7;
-      MUTATION_SET_PICKUP_POINT = 8;
-      MUTATION_CREATE_CHECKOUT_ORDER = 9;
-      MUTATION_SET_CART_ITEMS = 10;
-      MUTATION_ORDER_COMPLETED = 11;
-    }
-
-    message MutationRequest {
-      string cart_id = 1;
-      MutationType type = 2;
-      bytes payload = 3;          // Serialized specific mutation proto
-      int64 client_timestamp = 4; // Optional; server fills if zero
-    }
-
-    message MutationReply {
-      int32 status_code = 1;
-      bytes payload = 2; // JSON cart state or error string
-    }
-
-    message StateRequest {
-      string cart_id = 1;
-    }
-
-    message StateReply {
-      int32 status_code = 1;
-      bytes payload = 2; // JSON cart state
-    }
-
-    service CartActor {
-      rpc Mutate(MutationRequest) returns (MutationReply);
-      rpc GetState(StateRequest) returns (StateReply);
-    }
-
-### 5.2 Control Plane Proto
-
-    syntax = "proto3";
-    package control;
-    option go_package = "git.tornberg.me/go-cart-actor/proto;proto";
-
-    message Empty {}
-
-    message PingReply {
-      string host = 1;
-      int64 unix_time = 2;
-    }
-
-    message NegotiateRequest {
-      repeated string known_hosts = 1;
-    }
-    message NegotiateReply {
-      repeated string hosts = 1; // Healthy hosts returned
-    }
-
-    message CartIdsReply {
-      repeated string cart_ids = 1;
-    }
-
-    message OwnerChangeRequest {
-      string cart_id = 1;
-      string new_host = 2;
-    }
-    message OwnerChangeAck {
-      bool accepted = 1;
-      string message = 2;
-    }
-
-    message ClosingNotice {
-      string host = 1;
-    }
-
-    service ControlPlane {
-      rpc Ping(Empty) returns (PingReply);
-      rpc Negotiate(NegotiateRequest) returns (NegotiateReply);
-      rpc GetCartIds(Empty) returns (CartIdsReply);
-      rpc ConfirmOwner(OwnerChangeRequest) returns (OwnerChangeAck);
-      rpc Closing(ClosingNotice) returns (OwnerChangeAck);
-    }
-
----
-
-## 6. Message Type Mapping
-
-| Legacy Constant | Numeric | New Enum Value              |
-|-----------------|---------|-----------------------------|
-| AddRequestType  | 1       | MUTATION_ADD_REQUEST        |
-| AddItemType     | 2       | MUTATION_ADD_ITEM           |
-| RemoveItemType  | 4       | MUTATION_REMOVE_ITEM        |
-| RemoveDeliveryType | 5    | MUTATION_REMOVE_DELIVERY    |
-| ChangeQuantityType | 6    | MUTATION_CHANGE_QUANTITY    |
-| SetDeliveryType | 7       | MUTATION_SET_DELIVERY       |
-| SetPickupPointType | 8    | MUTATION_SET_PICKUP_POINT   |
-| CreateCheckoutOrderType | 9 | MUTATION_CREATE_CHECKOUT_ORDER |
-| SetCartItemsType | 10     | MUTATION_SET_CART_ITEMS     |
-| OrderCompletedType | 11   | MUTATION_ORDER_COMPLETED    |
-
-Persisted events keep original numeric codes; reconstruction simply casts to `MutationType`.
-
----
-
-## 7. Components To Remove / Replace
-
-Remove (after migration complete):
-- `remote-grain.go`
-- `rpc-server.go`
-- Any packet/frame-specific types solely used by the above (search: `FrameWithPayload`, `RemoteHandleMutation`, `RemoteGetState` where not reused by disk or internal logic).
-- The constants representing network frame types in `synced-pool.go` (RemoteNegotiate, AckChange, etc.) replaced by gRPC calls.
-- netpool usage for remote cart channel (control plane also no longer needs `Connection` abstraction).
-
-Retain (until reworked or optionally cleaned later):
-- `message.go` (for persistence)
-- `message-handler.go`
-- `cart-grain.go`
-- `messages.proto` (underlying mutation messages)
-- HTTP API server and REST handlers.
-
----
-
-## 8. New / Modified Components
-
-New files (planned):
-- `proto/cart_actor.proto`
-- `proto/control_plane.proto`
-- `grpc/cart_actor_server.go` (server impl)
-- `grpc/cart_actor_client.go` (client adapter implementing `Grain`)
-- `grpc/control_plane_server.go`
-- `grpc/control_plane_client.go`
-- `grpc/interceptors.go` (metrics, logging, optional tracing hooks)
-- `remote_grain_grpc.go` (adapter bridging existing interfaces)
-- `control_plane_adapter.go` (replaces frame handlers in `SyncedPool`)
-
-Modified:
-- `synced-pool.go` (remote host management now uses gRPC clients; negotiation logic updated)
-- `main.go` (initialize both gRPC services on startup)
-- `go.mod` (add `google.golang.org/grpc`)
-
----
-
-## 9. Step-by-Step Migration Plan
-
-1. Add proto files and generate Go code (`protoc --go_out --go-grpc_out`).
-2. Implement `CartActorServer`:
-   - Translate `MutationRequest` to `Message`.
-   - Use existing handler registry for payload encode/decode.
-   - Return JSON cart state.
-3. Implement `CartActorClient` wrapper (`RemoteGrainGRPC`) implementing:
-   - `HandleMessage`: Build envelope, call `Mutate`.
-   - `GetCurrentState`: Call `GetState`.
-4. Implement `ControlPlaneServer` with methods:
-   - `Ping`: returns host + time.
-   - `Negotiate`: merge host lists; emulate old logic.
-   - `GetCartIds`: iterate local grains.
-   - `ConfirmOwner`: replicate quorum flow (accept always; error path for future).
-   - `Closing`: schedule remote removal.
-5. Implement `ControlPlaneClient` used inside `SyncedPool.AddRemote`.
-6. Refactor `SyncedPool`:
-   - Replace frame handlers registration with gRPC client calls.
-   - Replace `Server.AddHandler(...)` start-up with launching gRPC server.
-   - Implement periodic health checks using `Ping`.
-7. Remove old connection constructs for 1337/1338.
-8. Metrics:
-   - Add unary interceptor capturing duration and status.
-   - Replace packet counters with `cart_grpc_mutate_calls_total`, `cart_grpc_control_calls_total`, histograms for latency.
-9. Update `main.go` to start:
-   - gRPC server(s).
-   - HTTP server as before.
-10. Delete legacy files & update README build instructions.
-11. Load testing & profiling on Raspberry Pi hardware (or ARM emulation).
-12. Final cleanup & dead code removal (search for now-unused constants & structs).
-13. Tag release.
-
----
-
-## 10. Performance Considerations (Raspberry Pi Focus)
-
-- Single `*grpc.ClientConn` per remote host (HTTP/2 multiplexing) to reduce file descriptor and handshake overhead.
-- Use small keepalive pings (optional) only if connections drop; default may suffice.
-- Avoid reflection / dynamic dispatch in hot path: pre-build a mapping from `MutationType` to handler function.
-- Reuse byte buffers:
-  - Implement a `sync.Pool` for mutation serialization to reduce GC pressure.
-- Enforce per-RPC deadlines (e.g. 300–400ms) to avoid pile-ups.
-- Backpressure:
-  - Before dispatch: if local grain pool at capacity and target grain is remote, abort early with 503 to caller (optional).
-- Disable gRPC compression for small payloads (mutation messages are small). Condition compression if payload > threshold (e.g. 8KB).
-- Compile with `-ldflags="-s -w"` in production to reduce binary size (optional).
-- Enable `GOMAXPROCS` tuned to CPU cores; Pi often benefits from leaving default but monitor.
-- Use histograms with limited buckets to reduce Prometheus cardinality.
-
----
-
-## 11. Testing Strategy
-
-Unit:
-- Message type mapping tests (legacy -> enum).
-- Envelope roundtrip: Original proto -> payload -> gRPC -> server decode -> internal Message.
-
-Integration:
-- Two-node cluster simulation:
-  - Mutate cart on Node A, ownership moves, verify remote access from Node B.
-  - Quorum failure simulation (temporarily reject `ConfirmOwner`).
-- Control plane negotiation: start nodes in staggered order, assert final membership.
-
-Load/Perf:
-- Benchmark local mutation vs remote mutation latency.
-- High concurrency test (N goroutines each performing X mutations).
-- Memory profiling (ensure no large buffer retention).
-
-Failure Injection:
-- Kill a node mid-mutation; client call should timeout and not corrupt local state.
-- Simulated network partition: drop `Ping` replies; ensure host removal path triggers.
-
----
-
-## 12. Rollback Strategy
-
-Because no mixed-version compatibility is provided, rollback = redeploy previous version containing legacy protocol:
-1. Stop all new-version pods.
-2. Deploy old version cluster-wide.
-3. No data migration needed (event persistence unaffected).
-
-Note: Avoid partial upgrades; perform full rolling restart quickly to prevent split-brain (new nodes won’t talk to old nodes).
-
----
-
-## 13. Risks & Mitigations
-
-| Risk | Description | Mitigation |
-|------|-------------|------------|
-| Full-cluster restart required | No mixed compatibility | Schedule maintenance window |
-| gRPC adds CPU overhead | Envelope + marshaling cost | Buffer reuse, keep small messages uncompressed |
-| Ownership race | Timing differences after refactor | Add explicit logs + tests around `RequestOwnership` path |
-| Hidden dependency on frame-level status codes | Some code may assume `FrameWithPayload` fields | Wrap gRPC responses into minimal compatibility structs until fully removed |
-| Memory growth | Connection reuse & pooled buffers not implemented initially | Add `sync.Pool` & track memory via pprof early |
-
----
-
-## 14. Logging & Observability
-
-- Structured log entries for:
-  - Ownership changes
-  - Negotiation rounds
-  - Remote spawn events
-  - Mutation failures (with cart id, mutation type)
-- Metrics:
-  - `cart_grpc_mutate_duration_seconds` (histogram)
-  - `cart_grpc_mutate_errors_total`
-  - `cart_grpc_control_duration_seconds`
-  - `cart_remote_hosts` (gauge)
-  - Retain existing grain counts.
-- Optional future: OpenTelemetry tracing (span per remote mutation).
-
----
-
-## 15. Future Enhancements (Post-Migration)
-
-- Replace JSON state with `CartState` proto and provide streaming watch API.
-- mTLS between nodes (certificate rotation via K8s Secret or SPIRE).
-- Distributed tracing integration.
-- Ownership leasing with TTL and optimistic renewal.
-- Delta replication or CRDT-based conflict resolution for experimentation.
-
----
-
-## 16. Task Breakdown & Estimates
-
-| Task | Estimate |
-|------|----------|
-| Proto definitions & generation | 0.5d |
-| CartActor server/client | 1.0d |
-| ControlPlane server/client | 1.0d |
-| SyncedPool refactor | 1.0d |
-| Metrics & interceptors | 0.5d |
-| Remove legacy code & cleanup | 0.5d |
-| Tests (unit + integration) | 1.5d |
-| Benchmark & tuning | 0.5–1.0d |
-| Total | ~6–7d |
-
----
-
-## 17. Open Questions (Confirm Before Implementation)
-
-1. Combine both services on a single port (simplify ops) or keep dual-port first? (Default here: keep dual, but easy to merge.)
-2. Minimum Go version remains 1.24.x—acceptable to add `google.golang.org/grpc` latest?
-3. Accept adding `sync.Pool` micro-optimizations in first pass or postpone?
-
----
-
-## 18. Acceptance Criteria
-
-- All previous integration tests (adjusted to gRPC) pass.
-- Cart operations (add, remove, delivery, checkout) function across at least a 2‑node cluster.
-- Control plane negotiation forms consistent host list.
-- Latency for a remote mutation does not degrade beyond an acceptable threshold (define baseline before merge).
-- Legacy networking code fully removed.
-
----
-
-## 19. Next Steps (If Approved)
-
-1. Implement proto files and commit.
-2. Scaffold server & client code.
-3. Refactor `SyncedPool` and `main.go`.
-4. Add metrics and tests.
-5. Run benchmark on target Pi hardware.
-6. Review & merge.
-
----
-
-End of Plan.

Makefile

@@ -0,0 +1,143 @@
+# ------------------------------------------------------------------------------
+# Makefile for go-cart-actor
+#
+# Key targets:
+#   make protogen      - Generate protobuf + gRPC code into proto/
+#   make clean_proto   - Remove generated proto *.pb.go files
+#   make verify_proto  - Ensure no stray root-level *.pb.go files exist
+#   make build         - Build the project
+#   make test          - Run tests (verbose)
+#   make tidy          - Run go mod tidy
+#   make regen         - Clean proto, regenerate, tidy, verify, build
+#   make help          - Show this help
+#
+# Conventions:
+#   - All .proto files live in $(PROTO_DIR)
+#   - Generated Go code is emitted under $(PROTO_DIR) via go_package mapping
+#   - go_package is set to: git.k6n.net/mats/go-cart-actor/proto;messages
+# ------------------------------------------------------------------------------
+
+MODULE_PATH := git.k6n.net/mats/go-cart-actor
+PROTO_DIR   := proto
+PROTOS      := $(PROTO_DIR)/cart.proto $(PROTO_DIR)/control_plane.proto $(PROTO_DIR)/checkout.proto $(PROTO_DIR)/order.proto
+CART_PROTO_DIR := $(PROTO_DIR)/cart
+CONTROL_PROTO_DIR := $(PROTO_DIR)/control
+CHECKOUT_PROTO_DIR := $(PROTO_DIR)/checkout
+ORDER_PROTO_DIR := $(PROTO_DIR)/order
+
+# Allow override: make PROTOC=/path/to/protoc
+PROTOC ?= protoc
+
+# Tools (auto-detect; can override)
+PROTOC_GEN_GO        ?= $(shell command -v protoc-gen-go 2>/dev/null)
+PROTOC_GEN_GO_GRPC   ?= $(shell command -v protoc-gen-go-grpc 2>/dev/null)
+
+GO        ?= go
+
+# Colors (optional)
+GREEN  := \033[32m
+RED    := \033[31m
+YELLOW := \033[33m
+RESET  := \033[0m
+
+# ------------------------------------------------------------------------------
+
+.PHONY: protogen clean_proto verify_proto tidy build test regen help check_tools
+
+help:
+	@echo "Available targets:"
+	@echo "  protogen      Generate protobuf & gRPC code"
+	@echo "  clean_proto   Remove generated *.pb.go files in $(PROTO_DIR)"
+	@echo "  verify_proto  Ensure no root-level *.pb.go files (old layout)"
+
+	@echo "  tidy          Run go mod tidy"
+	@echo "  build         Build the module"
+	@echo "  test          Run tests (verbose)"
+	@echo "  regen         Clean proto, regenerate, tidy, verify, and build"
+	@echo "  check_tools   Verify protoc + plugins are installed"
+
+check_tools:
+	@if [ -z "$(PROTOC_GEN_GO)" ] || [ -z "$(PROTOC_GEN_GO_GRPC)" ]; then \
+		echo "$(RED)Missing protoc-gen-go or protoc-gen-go-grpc in PATH.$(RESET)"; \
+		echo "Install with:"; \
+		echo "  go install google.golang.org/protobuf/cmd/protoc-gen-go@latest"; \
+		echo "  go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@latest"; \
+		exit 1; \
+	fi
+	@if ! command -v "$(PROTOC)" >/dev/null 2>&1; then \
+		echo "$(RED)protoc not found. Install protoc (e.g. via package manager)$(RESET)"; \
+		exit 1; \
+	fi
+	@echo "$(GREEN)All required tools detected.$(RESET)"
+
+protogen: check_tools
+	@echo "$(YELLOW)Generating protobuf code (outputs -> ./proto)...$(RESET)"
+	$(PROTOC) -I $(PROTO_DIR) \
+	  --go_out=./proto/cart --go_opt=paths=source_relative \
+	  --go-grpc_out=./proto/cart --go-grpc_opt=paths=source_relative \
+	  $(PROTO_DIR)/cart.proto
+	$(PROTOC) -I $(PROTO_DIR) \
+	  --go_out=./proto/control --go_opt=paths=source_relative \
+	  --go-grpc_out=./proto/control --go-grpc_opt=paths=source_relative \
+	  $(PROTO_DIR)/control_plane.proto
+	$(PROTOC) -I $(PROTO_DIR) \
+	  --go_out=./proto/checkout --go_opt=paths=source_relative \
+	  --go-grpc_out=./proto/checkout --go-grpc_opt=paths=source_relative \
+	  $(PROTO_DIR)/checkout.proto
+	$(PROTOC) -I $(PROTO_DIR) \
+	  --go_out=./proto/order --go_opt=paths=source_relative \
+	  --go-grpc_out=./proto/order --go-grpc_opt=paths=source_relative \
+	  $(PROTO_DIR)/order.proto
+	@echo "$(GREEN)Protobuf generation complete.$(RESET)"
+
+clean_proto:
+	@echo "$(YELLOW)Removing generated protobuf files...$(RESET)"
+	@rm -f $(PROTO_DIR)/cart/*_grpc.pb.go $(PROTO_DIR)/cart/*.pb.go
+	@rm -f $(PROTO_DIR)/control/*_grpc.pb.go $(PROTO_DIR)/control/*.pb.go
+	@rm -f $(PROTO_DIR)/checkout/*_grpc.pb.go $(PROTO_DIR)/checkout/*.pb.go
+	@echo "$(GREEN)Clean complete.$(RESET)"
+
+verify_proto:
+	@echo "$(YELLOW)Verifying proto layout...$(RESET)"
+	@if ls *.pb.go >/dev/null 2>&1; then \
+		echo "$(RED)ERROR: Found root-level generated *.pb.go files (should be only under $(PROTO_DIR)/ subdirs).$(RESET)"; \
+		ls -1 *.pb.go; \
+		exit 1; \
+	fi
+	@echo "$(GREEN)Proto layout OK (no root-level *.pb.go files).$(RESET)"
+
+run:
+	REDIS_ADDRESS=10.10.3.18:6379 \
+	REDIS_PASSWORD=slaskredis \
+	CART_DEBUG_PORT=8091 \
+	CART_PORT=8090 \
+	go run ./cmd/cart/
+
+tidy:
+	@echo "$(YELLOW)Running go mod tidy...$(RESET)"
+	$(GO) mod tidy
+	@echo "$(GREEN)tidy complete.$(RESET)"
+
+build:
+	@echo "$(YELLOW)Building...$(RESET)"
+	$(GO) build ./...
+	@echo "$(GREEN)Build success.$(RESET)"
+
+test:
+	@echo "$(YELLOW)Running tests...$(RESET)"
+	$(GO) test -v ./...
+	@echo "$(GREEN)Tests completed.$(RESET)"
+
+regen: clean_proto protogen tidy verify_proto build
+	@echo "$(GREEN)Full regenerate cycle complete.$(RESET)"
+
+# Utility: show proto sources and generated outputs
+print_proto:
+	@echo "Proto sources:"
+	@ls -1 $(PROTOS)
+	@echo ""
+	@echo "Generated files (if any):"
+	@ls -1 $(PROTO_DIR)/*pb.go 2>/dev/null || echo "(none)"
+
+# Prevent make from treating these as file targets if similarly named files appear.
+.SILENT: help check_tools protogen clean_proto verify_proto tidy build test regen print_proto

NEW_MUTATIONS_SPEC.md

@@ -0,0 +1,238 @@
+go-cart-actor/NEW_MUTATIONS_SPEC.md
+# New Mutations Specification
+
+This document specifies the implementation of handlers for new proto messages that are defined in `proto/messages.proto` but not yet registered in the mutation registry. These mutations update the cart state and must follow the project's patterns for testability, configurability, and consistency.
+
+## Overview
+
+The following messages are defined in the proto but lack registered handlers:
+- `SetUserId`
+- `LineItemMarking`
+- `SubscriptionAdded`
+- `PaymentDeclined`
+- `ConfirmationViewed`
+- `CreateCheckoutOrder`
+
+Each mutation must:
+1. Define a handler function with signature `func(*CartGrain, *T) error`
+2. Be registered in `NewCartMultationRegistry()` using `actor.NewMutation`
+3. Include unit tests
+4. Optionally add HTTP/gRPC endpoints if client-invokable
+5. Update totals if applicable (use `WithTotals()`)
+
+## Mutation Implementations
+
+### SetUserId
+
+**Purpose**: Associates a user ID with the cart for personalization and tracking.
+
+**Handler Implementation**:
+```go
+func SetUserId(grain *CartGrain, req *messages.SetUserId) error {
+    if req.UserId == "" {
+        return errors.New("user ID cannot be empty")
+    }
+    grain.UserId = req.UserId
+    return nil
+}
+```
+
+**Registration**:
+```go
+actor.NewMutation(SetUserId, func() *messages.SetUserId {
+    return &messages.SetUserId{}
+}),
+```
+
+**Notes**: This is a simple state update. No totals recalculation needed.
+
+### LineItemMarking
+
+**Purpose**: Adds or updates a marking (e.g., gift message, special instructions) on a specific line item.
+
+**Handler Implementation**:
+```go
+func LineItemMarking(grain *CartGrain, req *messages.LineItemMarking) error {
+    for i, item := range grain.Items {
+        if item.Id == req.Id {
+            grain.Items[i].Marking = &Marking{
+                Type: req.Type,
+                Text: req.Marking,
+            }
+            return nil
+        }
+    }
+    return fmt.Errorf("item with ID %d not found", req.Id)
+}
+```
+
+**Registration**:
+```go
+actor.NewMutation(LineItemMarking, func() *messages.LineItemMarking {
+    return &messages.LineItemMarking{}
+}),
+```
+
+**Notes**: Assumes `CartGrain.Items` has a `Marking` field (single marking per item). If not, add it to the grain struct.
+
+### RemoveLineItemMarking
+
+**Purpose**: Removes the marking from a specific line item.
+
+**Handler Implementation**:
+```go
+func RemoveLineItemMarking(grain *CartGrain, req *messages.RemoveLineItemMarking) error {
+    for i, item := range grain.Items {
+        if item.Id == req.Id {
+            grain.Items[i].Marking = nil
+            return nil
+        }
+    }
+    return fmt.Errorf("item with ID %d not found", req.Id)
+}
+```
+
+**Registration**:
+```go
+actor.NewMutation(RemoveLineItemMarking, func() *messages.RemoveLineItemMarking {
+    return &messages.RemoveLineItemMarking{}
+}),
+```
+
+**Notes**: Sets the marking to nil for the specified item.
+
+### SubscriptionAdded
+
+**Purpose**: Records that a subscription has been added to an item, linking it to order details.
+
+**Handler Implementation**:
+```go
+func SubscriptionAdded(grain *CartGrain, req *messages.SubscriptionAdded) error {
+    for i, item := range grain.Items {
+        if item.Id == req.ItemId {
+            grain.Items[i].SubscriptionDetailsId = req.DetailsId
+            grain.Items[i].OrderReference = req.OrderReference
+            grain.Items[i].IsSubscribed = true
+            return nil
+        }
+    }
+    return fmt.Errorf("item with ID %d not found", req.ItemId)
+}
+```
+
+**Registration**:
+```go
+actor.NewMutation(SubscriptionAdded, func() *messages.SubscriptionAdded {
+    return &messages.SubscriptionAdded{}
+}),
+```
+
+**Notes**: Assumes fields like `SubscriptionDetailsId`, `OrderReference`, `IsSubscribed` exist on items. Add to grain if needed.
+
+### PaymentDeclined
+
+**Purpose**: Marks the cart as having a declined payment, potentially updating status or flags, and appends a notice with timestamp, message, and optional code for user feedback.
+
+**Handler Implementation**:
+```go
+func PaymentDeclined(grain *CartGrain, req *messages.PaymentDeclined) error {
+    grain.PaymentStatus = "declined"
+    grain.PaymentDeclinedNotices = append(grain.PaymentDeclinedNotices, Notice{
+        Timestamp: time.Now(),
+        Message:   req.Message,
+        Code:      req.Code,
+    })
+    // Optionally clear checkout order if in progress
+    if grain.CheckoutOrderId != "" {
+        grain.CheckoutOrderId = ""
+    }
+    return nil
+}
+```
+
+**Registration**:
+```go
+actor.NewMutation(PaymentDeclined, func() *messages.PaymentDeclined {
+    return &messages.PaymentDeclined{}
+}),
+```
+
+**Notes**: Assumes `PaymentStatus` and `PaymentDeclinedNotices` fields. Add status tracking and error notices list to grain. Notice struct has Timestamp, Message, and optional Code.
+
+### ConfirmationViewed
+
+**Purpose**: Records that the order confirmation has been viewed by the user. Applied automatically when the confirmation page is loaded in checkout_server.go.
+
+**Handler Implementation**:
+```go
+func ConfirmationViewed(grain *CartGrain, req *messages.ConfirmationViewed) error {
+    grain.ConfirmationViewCount++
+    grain.ConfirmationLastViewedAt = time.Now()
+    return nil
+}
+```
+
+**Registration**:
+```go
+actor.NewMutation(ConfirmationViewed, func() *messages.ConfirmationViewed {
+    return &messages.ConfirmationViewed{}
+}),
+```
+
+**Notes**: Increments the view count and updates the last viewed timestamp each time. Assumes `ConfirmationViewCount` and `ConfirmationLastViewedAt` fields.
+
+### CreateCheckoutOrder
+
+**Purpose**: Initiates the checkout process, validating terms and creating an order reference.
+
+**Handler Implementation**:
+```go
+func CreateCheckoutOrder(grain *CartGrain, req *messages.CreateCheckoutOrder) error {
+    if len(grain.Items) == 0 {
+        return errors.New("cannot checkout empty cart")
+    }
+    if req.Terms != "accepted" {
+        return errors.New("terms must be accepted")
+    }
+    // Validate other fields as needed
+    grain.CheckoutOrderId = generateOrderId()
+    grain.CheckoutStatus = "pending"
+    grain.CheckoutCountry = req.Country
+    return nil
+}
+```
+
+**Registration**:
+```go
+actor.NewMutation(CreateCheckoutOrder, func() *messages.CreateCheckoutOrder {
+    return &messages.CreateCheckoutOrder{}
+}).WithTotals(),
+```
+
+**Notes**: Use `WithTotals()` to recalculate totals after checkout initiation. Assumes order ID generation function.
+
+## Implementation Steps
+
+For each mutation:
+
+1. **Add Handler Function**: Implement in `pkg/cart/` (e.g., `cart_mutations.go`).
+2. **Register in Registry**: Add to `NewCartMultationRegistry()` in `cart-mutation-helper.go`.
+3. **Regenerate Proto**: Run `protoc` commands after any proto changes.
+4. **Add Tests**: Create unit tests in `pkg/cart/` testing the handler logic.
+5. **Add Endpoints** (if needed): For client-invokable mutations, add HTTP handlers in `cmd/cart/pool-server.go`. ConfirmationViewed is handled in `cmd/cart/checkout_server.go` when the confirmation page is viewed.
+6. **Update Grain Struct**: Add any new fields to `CartGrain` in `pkg/cart/grain.go`.
+7. **Run Tests**: Ensure `go test ./...` passes.
+
+## Testing Guidelines
+
+- Mock dependencies using interfaces.
+- Test error cases (e.g., invalid IDs, empty carts).
+- Verify state changes and totals recalculation.
+- Use table-driven tests for multiple scenarios.
+
+## Configuration and Testability
+
+Follow `MutationRegistry` and `SimpleGrainPool` patterns:
+- Use interfaces for external dependencies (e.g., ID generators).
+- Inject configurations via constructor parameters.
+- Avoid global state; make handlers pure functions where possible.

README.md

@@ -176,3 +176,238 @@ curl --cookie cookies.txt http://localhost:8080/cart/add/TEST-SKU-123
 - Always regenerate protobuf Go code after modifying any `.proto` files (messages/cart_actor/control_plane)
 - The generated `messages.pb.go` file should not be edited manually
 - Make sure your PATH includes the protoc-gen-go binary location (usually `$GOPATH/bin`)
+
+---
+
+## Architecture Overview
+
+The system is a distributed, sharded (by cart id) actor model implementation:
+
+- Each cart is a grain (an in‑memory struct `*CartGrain`) that owns and mutates its own state.
+- A **local grain pool** holds grains owned by the node.
+- A **synced (cluster) pool** (`SyncedPool`) coordinates multiple nodes and exposes local or remote grains through a uniform interface (`GrainPool`).
+- All inter‑node communication is gRPC:
+  - Cart mutation & state RPCs (CartActor service).
+  - Control plane RPCs (ControlPlane service) for membership, ownership negotiation, liveness, and graceful shutdown.
+
+### Key Processes
+
+1. Client HTTP request (or gRPC client) arrives with a cart identifier (cookie or path).
+2. The pool resolves ownership:
+   - If local grain exists → use it.
+   - If a remote host is known owner → a remote grain proxy (`RemoteGrainGRPC`) is used; it performs gRPC calls to the owning node.
+   - If ownership is unknown → node attempts to claim ownership (quorum negotiation) and spawns a local grain.
+3. Mutation is executed via the **mutation registry** (registry wraps domain logic + optional totals recomputation).
+4. Updated state returned to caller; ownership preserved unless relinquished later (not yet implemented to shed load).
+
+---
+
+## Grain & Mutation Model
+
+- `CartGrain` holds items, deliveries, pricing aggregates, and checkout/order metadata.
+- All mutations are registered via `RegisterMutation[T]` with signature:
+  ```
+  func(*CartGrain, *T) error
+  ```
+- `WithTotals()` flag triggers automatic recalculation of totals after successful handlers.
+- The old giant `switch` in `CartGrain.Apply` has been replaced by registry dispatch; unregistered mutations fail fast.
+- Adding a mutation:
+  1. Define proto message.
+  2. Generate code.
+  3. Register handler (optionally WithTotals).
+  4. Add gRPC RPC + request wrapper if the mutation must be remotely invokable.
+  5. (Optional) Add HTTP endpoint mapping to the mutation.
+
+---
+
+## Local Grain Pool
+
+- Manages an in‑memory map `map[CartId]*CartGrain`.
+- Lazy spawn: first mutation or explicit access triggers `spawn(id)`.
+- TTL / purge loop periodically removes expired grains unless they changed recently (basic memory pressure management).
+- Capacity limit (`PoolSize`); oldest expired grain evicted first when full.
+
+---
+
+## Synced (Cluster) Pool
+
+`SyncedPool` wraps a local pool and tracks:
+
+- `remoteHosts`: known peer nodes (gRPC connections).
+- `remoteIndex`: mapping of cart id → remote grain proxy (`RemoteGrainGRPC`) for carts owned elsewhere.
+
+Responsibilities:
+
+1. Discovery integration (via a `Discovery` interface) adds/removes hosts.
+2. Periodic ping health checks (ControlPlane.Ping).
+3. Ring-based deterministic ownership:
+   - Ownership is derived directly from the consistent hashing ring (no quorum RPC or `ConfirmOwner`).
+4. Remote spawning:
+   - When a remote host reports its cart ids (`GetCartIds`), the pool creates remote proxies for fast routing.
+
+---
+
+## Remote Grain Proxies
+
+A `RemoteGrainGRPC` implements the `Grain` interface but delegates:
+
+- `Apply` → Specific CartActor per‑mutation RPC (e.g., `AddItem`, `RemoveItem`) constructed from the mutation type. (Legacy envelope removed.)
+- `GetCurrentState` → `CartActor.GetState`.
+
+Return path:
+
+1. gRPC reply (CartMutationReply / StateReply) → proto `CartState`.
+2. `ToCartState` / mapping reconstructs a local `CartGrain` snapshot for callers expecting grain semantics.
+
+---
+
+## Control Plane (Inter‑Node Coordination)
+
+Defined in `proto/control_plane.proto`:
+
+| RPC | Purpose |
+|-----|---------|
+| `Ping` | Liveness; increments missed ping counter if failing. |
+| `Negotiate` | Merges membership views; used after discovery events. |
+| `GetCartIds` | Enumerate locally owned carts for remote index seeding. |
+| `Closing` | Graceful shutdown notice; peers remove host & associated remote grains. |
+
+### Ownership / Quorum Rules
+
+- If total participating hosts < 3 → all must accept.
+- Otherwise majority acceptance (`ok >= total/2`).
+- On failure → local tentative grain is removed (rollback to avoid split‑brain).
+
+---
+
+## Request / Mutation Flow Examples
+
+### Local Mutation
+1. HTTP handler parses request → determines cart id.
+2. `SyncedPool.Apply`:
+   - Finds local grain (or spawns new after quorum).
+   - Executes registry mutation.
+3. Totals updated if flagged.
+4. HTTP response returns updated JSON (via `ToCartState`).
+
+### Remote Mutation
+1. `SyncedPool.Apply` sees cart mapped to a remote host.
+2. Routes to `RemoteGrainGRPC.Apply`.
+3. Remote node executes mutation locally and returns updated state over gRPC.
+4. Proxy materializes snapshot locally (not authoritative, read‑only view).
+
+### Checkout (Side‑Effecting, Non-Pure)
+- HTTP `/checkout` uses current grain snapshot to build payload (pure function).
+- Calls Klarna externally (not a mutation).
+- Applies `InitializeCheckout` mutation to persist reference + status.
+- Returns Klarna order JSON to client.
+
+---
+
+## Scaling & Deployment
+
+- **Horizontal scaling**: Add more nodes; discovery layer (Kubernetes / service registry) feeds hosts to `SyncedPool`.
+- **Sharding**: Implicit by cart id hash. Ownership is first-claim with quorum acceptance.
+- **Hot spots**: A single popular cart remains on one node; for heavy multi-client concurrency, future work could add read replicas or partitioning (not implemented).
+- **Capacity tuning**: Increase `PoolSize` & memory limits; adjust TTL for stale cart eviction.
+
+### Adding Nodes
+1. Node starts gRPC server (CartActor + ControlPlane).
+2. After brief delay, begins discovery watch; on event:
+   - New host → dial + negotiate → seed remote cart ids.
+3. Pings maintain health; failed hosts removed (proxies invalidated).
+
+---
+
+## Failure Handling
+
+| Scenario | Behavior |
+|----------|----------|
+| Remote host unreachable | Pings increment `MissedPings`; after threshold host removed. |
+| Ownership negotiation fails | Tentative local grain discarded. |
+| gRPC call error on remote mutation | Error bubbled to caller; no local fallback. |
+| Missing mutation registration | Fast failure with explicit error message. |
+| Partial checkout (Klarna fails) | No local state mutation for checkout; client sees error; cart remains unchanged. |
+
+---
+
+## Mutation Registry Summary
+
+- Central, type-safe registry prevents silent omission.
+- Each handler:
+  - Validates input.
+  - Mutates `*CartGrain`.
+  - Returns error for rejection.
+- Automatic totals recomputation reduces boilerplate and consistency risk.
+- Coverage test (add separately) can enforce all proto mutations are registered.
+
+---
+
+## gRPC Interfaces
+
+- **CartActor**: Per-mutation unary RPCs + `GetState`. (Checkout logic intentionally excluded; handled at HTTP layer.)
+- **ControlPlane**: Cluster coordination (Ping, Negotiate, GetCartIds, Closing) — ownership now ring-determined (no ConfirmOwner).
+
+**Ports** (default / implied):
+- CartActor & ControlPlane share the same gRPC server/listener (single port, e.g. `:1337`).
+- Legacy frame/TCP code has been removed.
+
+---
+
+## Security & Future Enhancements
+
+| Area | Potential Improvement |
+|------|------------------------|
+| Transport Security | Add TLS / mTLS to gRPC servers & clients. |
+| Auth / RBAC | Intercept CartActor RPCs with auth metadata. |
+| Backpressure | Rate-limit remote mutation calls per host. |
+| Observability | Add per-mutation Prometheus metrics & tracing spans. |
+| Ownership | Add lease timeouts / fencing tokens for stricter guarantees. |
+| Batch Ops | Introduce batch mutation RPC or streaming updates (WatchState). |
+| Persistence | Reintroduce event log or snapshot persistence layer if durability required. |
+
+---
+
+## Adding a New Node (Operational Checklist)
+
+1. Deploy binary/container with same proto + registry.
+2. Expose gRPC port.
+3. Ensure discovery lists the new host.
+4. Node dials peers, negotiates membership.
+5. Remote cart proxies seeded.
+6. Traffic routed automatically based on ownership.
+
+---
+
+## Adding a New Mutation (Checklist Recap)
+
+1. Define proto message (+ request wrapper & RPC if remote invocation needed).
+2. Regenerate protobuf code.
+3. Implement & register handler (`RegisterMutation`).
+4. Add client (HTTP/gRPC) endpoint.
+5. Write unit + integration tests.
+6. (Optional) Add to coverage test list and docs.
+
+---
+
+## High-Level Data Flow Diagram (Text)
+
+```
+Client -> HTTP Handler -> SyncedPool -> (local?) -> Registry -> Grain State
+                       \-> (remote?) -> RemoteGrainGRPC -> gRPC -> Remote CartActor -> Registry -> Grain
+ControlPlane: Discovery Events <-> Negotiation/Ping <-> SyncedPool state (ring determines ownership)
+```
+
+---
+
+## Troubleshooting
+
+| Symptom | Likely Cause | Action |
+|---------|--------------|--------|
+| New cart every request | Secure cookie over plain HTTP or not sending cookie jar | Disable Secure locally or use HTTPS & proper curl `-b` |
+| Unsupported mutation error | Missing registry handler | Add `RegisterMutation` for that proto |
+| Ownership imbalance | Ring host distribution skew or rapid host churn | Examine `cart_ring_host_share`, `cart_ring_hosts`, and logs for host add/remove; rebalance or investigate instability |
+| Remote mutation latency | Network / serialization overhead | Consider batching or colocating hot carts |
+| Checkout returns 500 | Klarna call failed | Inspect logs; no grain state mutated |
+
+---

TODO.md

@@ -0,0 +1,245 @@
+# TODO / Roadmap
+
+A living roadmap for improving the cart actor system. Focus areas:
+1. Reliability & correctness
+2. Simplicity of mutation & ownership flows
+3. Developer experience (DX)
+4. Operability (observability, tracing, metrics)
+5. Performance & scalability
+6. Security & multi-tenant readiness
+
+---
+
+## 1. Immediate Next Steps (High-Leverage)
+
+| Priority | Task | Goal | Effort | Owner | Notes |
+|----------|------|------|--------|-------|-------|
+| P0 | Add mutation registry coverage test | Ensure no unregistered mutations silently fail | S |  | Failing fast in CI |
+| P0 | Add decodeJSON helper + 400 mapping for EOF | Reduce noisy 500 logs | S |  | Improves client API clarity |
+| P0 | Regenerate protos & prune unused messages (CreateCheckoutOrder, Checkout RPC remnants) | Eliminate dead types | S |  | Avoid confusion |
+| P0 | Add integration test: multi-node ownership negotiation | Validate quorum logic | M |  | Spin up 2–3 nodes ephemeral |
+| P1 | Export Prometheus metrics for per-mutation counts & latency | Operability | M |  | Wrap registry handlers |
+| P1 | Add graceful shutdown ordering (Closing → wait for acks → stop gRPC) | Reduce in-flight mutation failures | S |  | Add context cancellation |
+| P1 | Add coverage for InitializeCheckout / OrderCreated flows | Checkout reliability | S |  | Simulate Klarna stub |
+| P2 | Add optional batching client (apply multiple mutations locally then persist) | Performance | M |  | Only if needed |
+
+---
+
+## 2. Simplification Opportunities
+
+### A. RemoteGrain Proxy Mapping
+Current: manual switch building each RPC call.
+Simplify by:
+- Generating a thin client adapter from proto RPC descriptors (codegen).
+- Or using a registry similar to mutation registry but for “outbound call constructors”.
+Benefit: adding a new mutation = add proto + register server handler + register outbound invoker (no switch edits).
+
+### B. Ownership Negotiation
+Current: ad hoc quorum rule in `SyncedPool`.
+Simplify:
+- Introduce explicit `OwnershipLease{holder, expiresAt, version}`.
+- Use monotonic version increment—reject stale ConfirmOwner replies.
+- Optional: add randomized backoff to reduce thundering herd on contested cart ids.
+
+### C. CartId Handling
+Current: ephemeral 16-byte array with trimmed string semantics.
+Simplify:
+- Use ULID / UUIDv7 (time-ordered, collision-resistant) for easier external correlation.
+- Provide helper `NewCartIdString()` and keep internal fixed-size if still desired.
+
+### D. Mutation Signatures
+Current: registry assumes `func(*CartGrain, *T) error`.
+Extension option: allow pure transforms returning a delta struct (for audit/logging):
+```
+type MutationResult struct {
+  Changed bool
+  Events  []interface{}
+}
+```
+Only implement if auditing/event-sourcing reintroduced.
+
+---
+
+## 3. Developer Experience Improvements
+
+| Task | Rationale | Approach |
+|------|-----------|----------|
+| Makefile targets: `make run-single`, `make run-multi N=3` | Faster local cluster spin-up | Docker compose or background “mini cluster” scripts |
+| Template for new mutation (generator) | Reduce boilerplate | `go:generate` scanning proto for new RPCs |
+| Lint config (golangci-lint) | Catch subtle issues early | Add `.golangci.yml` |
+| Pre-commit hook for proto regeneration check | Avoid stale generated code | Script compares git diff after `make protogen` |
+| Example client (Go + curl snippets auto-generated) | Onboarding | Codegen a markdown from proto comments |
+
+---
+
+## 4. Observability / Metrics / Tracing
+
+| Area | Metric / Trace | Notes |
+|------|----------------|-------|
+| Mutation registry | `cart_mutations_total{type,success}`; duration histogram | Wrap handler |
+| Ownership negotiation | `cart_ownership_attempts_total{result}` | result=accepted,rejected,timeout |
+| Remote latency | `cart_remote_mutation_seconds{method}` | Use client interceptors |
+| Pings | `cart_remote_missed_pings_total{host}` | Already count, expose |
+| Checkout flow | `checkout_attempts_total`, `checkout_failures_total` | Differentiate Klarna vs internal errors |
+| Tracing | Span: HTTP handler → SyncedPool.Apply → (Remote?) gRPC → mutation handler | Add OpenTelemetry instrumentation |
+
+---
+
+## 5. Performance & Scalability
+
+| Concern | Idea | Trade-Off |
+|---------|------|-----------|
+| High mutation rate on single cart | Introduce optional mutation queue (serialize explicitly) | Slight latency increase per op |
+| Remote call overhead | Add client-side gRPC pooling & per-host circuit breaker | Complexity vs resilience |
+| TTL purge efficiency | Use min-heap or timing wheel instead of slice scan | More code, better big-N performance |
+| Batch network latency | Add `BatchMutate` RPC (list of mutations applied atomically) | Lost single-op simplicity |
+
+---
+
+## 6. Reliability Features
+
+| Feature | Description | Priority |
+|---------|-------------|----------|
+| Lease fencing token | Include `ownership_version` in all remote mutate requests | M |
+| Retry policy | Limited retry for transient network errors (idempotent mutations only) | L |
+| Dead host reconciliation | On host removal, proactively attempt re-acquire of its carts | M |
+| Drain mode | Node marks itself “draining” → refuses new ownership claims | M |
+
+---
+
+## 7. Security & Hardening
+
+| Area | Next Step | Detail |
+|------|-----------|--------|
+| Transport | mTLS on gRPC | Use SPIFFE IDs or simple CA |
+| AuthN/AuthZ | Interceptor enforcing service token | Inject metadata header |
+| Input validation | Strengthen JSON decode responses | Disallow unknown fields globally |
+| Rate limiting | Per-IP / per-cart throttling | Guard hotspot abuse |
+| Multi-tenancy | Tenant id dimension in cart id or metadata | Partition metrics & ownership |
+
+---
+
+## 8. Testing Strategy Enhancements
+
+| Gap | Improvement |
+|-----|------------|
+| No multi-node integration test in CI | Spin ephemeral in-process servers on randomized ports |
+| Mutation regression | Table-driven tests auto-discover handlers via registry |
+| Ownership race | Stress test: concurrent Apply on same new cart id from N goroutines |
+| Checkout external dependency | Klarna mock server (HTTptest) + deterministic responses |
+| Fuzzing | Fuzz `BuildCheckoutOrderPayload` & mutation handlers for panics |
+
+---
+
+## 9. Cleanup / Tech Debt
+
+| Item | Action |
+|------|--------|
+| Remove deprecated proto remnants (CreateCheckoutOrder, Checkout RPC) | Delete & regenerate |
+| Consolidate duplicate tax computations | Single helper with tax config |
+| Delivery price hard-coded (4900) | Config or pricing strategy interface |
+| Mixed naming (camel vs snake JSON historically) | Provide stable external API doc; accept old forms if needed |
+| Manual remote mutation switch (if still present) | Replace with generated outbound registry |
+| Mixed error responses (string bodies) | Standardize JSON: `{ "error": "...", "code": 400 }` |
+
+---
+
+## 10. Potential Future Features
+
+| Feature | Value | Complexity |
+|---------|-------|------------|
+| Streaming `WatchState` RPC | Real-time cart updates for clients | Medium |
+| Event sourcing / audit log | Replay, analytics, debugging | High |
+| Promotion / coupon engine plugin | Business extensibility | Medium |
+| Partial cart reservation / inventory lock | Stock accuracy under concurrency | High |
+| Multi-currency pricing | Globalization | Medium |
+| GraphQL facade | Client flexibility | Medium |
+
+---
+
+## 11. Suggested Prioritized Backlog (Condensed)
+
+1. Coverage test + decode error mapping (P0)
+2. Proto regeneration & cleanup (P0)
+3. Metrics wrapper for registry (P1)
+4. Multi-node ownership integration test (P1)
+5. Delivery pricing abstraction (P2)
+6. Lease version in remote RPCs (P2)
+7. BatchMutate evaluation (P3)
+8. TLS / auth hardening (P3) if going multi-tenant/public
+9. Event sourcing (Evaluate after stability) (P4)
+
+---
+
+## 12. Simplifying the Developer Workflow
+
+| Pain | Simplifier |
+|------|------------|
+| Manual mutation boilerplate | Code generator for registry stubs |
+| Forgetting totals | Enforce WithTotals lint: fail if mutation touches items/deliveries without flag |
+| Hard to inspect remote ownership | `/internal/ownership` debug endpoint (JSON of local + remoteIndex) |
+| Hard to see mutation timings | Add `?debug=latency` header to return per-mutation durations |
+| Cookie dev confusion (Secure flag) | Env var: `DEV_INSECURE_COOKIES=1` |
+
+---
+
+## 13. Example: Mutation Codegen Sketch (Future)
+
+Input: cart_actor.proto  
+Output: `mutation_auto.go`
+- Detect messages used in RPC wrappers (e.g., `AddItemRequest` → payload field).
+- Generate `RegisterMutation` template if handler not found.
+- Mark with `// TODO implement logic`.
+
+---
+
+## 14. Risk / Impact Matrix (Abbreviated)
+
+| Change | Risk | Mitigation |
+|--------|------|-----------|
+| Replace remote switch with registry | Possible missing registration → runtime error | Coverage test gating CI |
+| Lease introduction | Split-brain if version mishandled | Increment + assert monotonic; test race |
+| BatchMutate | Large atomic operations starving others | Size limits & fair scheduling |
+| Event sourcing | Storage + replay complexity | Start with append-only log + compaction job |
+
+---
+
+## 15. Contributing Workflow (Proposed)
+
+1. Add / modify proto → run `make protogen`
+2. Implement mutation logic → add `RegisterMutation` invocation
+3. Add/Update tests (unit + integration)
+4. Run `make verify` (lint, test, coverage, proto diff)
+5. Open PR (template auto-checklist referencing this TODO)
+6. Merge requires green CI + coverage threshold
+
+---
+
+## 16. Open Questions
+
+| Question | Notes |
+|----------|-------|
+| Do we need sticky sessions for HTTP layer scaling? | Currently cart id routing suffices |
+| Should deliveries prune invalid line references on SetCartRequest? | Inconsistency risk; add optional cleanup |
+| Is checkout idempotency strict enough? | Multiple create vs update semantics |
+| Add version field to CartState for optimistic concurrency? | Could enable external CAS writes |
+
+---
+
+## 17. Tracking
+
+Mark any completed tasks with `[x]`:
+
+- [ ] Coverage test
+- [ ] Decode helper + 400 mapping
+- [ ] Proto cleanup
+- [ ] Registry metrics instrumentation
+- [ ] Ownership multi-node test
+- [ ] Lease versioning
+- [ ] Delivery pricing abstraction
+- [ ] TLS/mTLS internal
+- [ ] BatchMutate design doc
+
+---
+
+_Last updated: roadmap draft – refine after first metrics & scaling test run._

amqp-order-handler.go

@@ -1,83 +0,0 @@
-package main
-
-import (
-	"log"
-
-	amqp "github.com/rabbitmq/amqp091-go"
-)
-
-type AmqpOrderHandler struct {
-	Url        string
-	connection *amqp.Connection
-	//channel    *amqp.Channel
-}
-
-const (
-	topic = "order-placed"
-)
-
-func (t *AmqpOrderHandler) Connect() error {
-
-	conn, err := amqp.DialConfig(t.Url, amqp.Config{
-		//Vhost:      "/",
-		Properties: amqp.NewConnectionProperties(),
-	})
-
-	if err != nil {
-		return err
-	}
-	t.connection = conn
-	ch, err := conn.Channel()
-	if err != nil {
-		return err
-	}
-	defer ch.Close()
-	if err := ch.ExchangeDeclare(
-		topic,   // name
-		"topic", // type
-		true,    // durable
-		false,   // auto-delete
-		false,   // internal
-		false,   // noWait
-		nil,     // arguments
-	); err != nil {
-		return err
-	}
-
-	if _, err = ch.QueueDeclare(
-		topic, // name of the queue
-		true,  // durable
-		false, // delete when unused
-		false, // exclusive
-		false, // noWait
-		nil,   // arguments
-	); err != nil {
-		return err
-	}
-
-	return nil
-}
-
-func (t *AmqpOrderHandler) Close() error {
-	log.Println("Closing master channel")
-	return t.connection.Close()
-	//return t.channel.Close()
-}
-
-func (t *AmqpOrderHandler) OrderCompleted(data []byte) error {
-	ch, err := t.connection.Channel()
-	if err != nil {
-		return err
-	}
-	defer ch.Close()
-	return ch.Publish(
-		topic,
-		topic,
-		true,
-		false,
-		amqp.Publishing{
-			ContentType: "application/json",
-			Body:        data,
-		},
-	)
-}

api-tests/cart.http

@@ -1,6 +1,6 @@
 
 ### Add item to cart
-POST https://cart.tornberg.me/api/12345
+POST https://cart.k6n.net/api/12345
 Content-Type: application/json
 
 {
@@ -9,7 +9,7 @@ Content-Type: application/json
 }
 
 ### Update quanity of item in cart
-PUT https://cart.tornberg.me/api/12345
+PUT https://cart.k6n.net/api/12345
 Content-Type: application/json
 
 {
@@ -18,12 +18,12 @@ Content-Type: application/json
 }
 
 ### Delete item from cart
-DELETE https://cart.tornberg.me/api/1002/1
+DELETE https://cart.k6n.net/api/1002/1
 
 
 ### Set delivery
 
-POST https://cart.tornberg.me/api/1002/delivery
+POST https://cart.k6n.net/api/1002/delivery
 Content-Type: application/json
 
 {
@@ -33,10 +33,8 @@ Content-Type: application/json
 
 
 ### Get cart
-GET https://cart.tornberg.me/api/12345
+GET https://cart.k6n.net/api/12345
 
 
 ### Remove delivery method
-DELETE https://cart.tornberg.me/api/12345/delivery/2
+DELETE https://cart.k6n.net/api/12345/delivery/2
-
-

api-tests/test_ucp.sh

@@ -0,0 +1,291 @@
+#!/usr/bin/env bash
+# ──────────────────────────────────────────────────────────────────────────────
+# UCP API test suite
+# Tests the Universal Commerce Protocol REST endpoints (cart, order) via curl.
+#
+# Prerequisites:
+#   make up-infra     (infra compose up — order :8092, cart :8090)
+#   OR full stack     (docker compose --profile "*" up — nginx on :8080)
+#
+# Usage:
+#   # Direct to Docker services (infra stack):
+#   bash api-tests/test_ucp.sh --infra
+#
+#   # Via nginx (full compose stack):
+#   bash api-tests/test_ucp.sh --edge
+#
+#   # Single service:
+#   bash api-tests/test_ucp.sh --order
+#   bash api-tests/test_ucp.sh --cart
+#
+#   # Verify signatures (requires signing key mounted):
+#   bash api-tests/test_ucp.sh --verify-sig
+# ──────────────────────────────────────────────────────────────────────────────
+set -euo pipefail
+
+MODE="${1:---infra}"
+JQ="${JQ:-$(command -v jq || true)}"
+
+# ── Base URLs ────────────────────────────────────────────────────────────────
+if [ "$MODE" = "--edge" ]; then
+  BASE="http://localhost:8080"
+  CART_URL="$BASE"
+  ORDER_URL="$BASE"
+  CHECKOUT_URL="$BASE"
+elif [ "$MODE" = "--order" ]; then
+  ORDER_URL="http://localhost:8092"
+elif [ "$MODE" = "--cart" ]; then
+  CART_URL="http://localhost:8090"
+elif [ "$MODE" = "--verify-sig" ]; then
+  # If signing is enabled (key mounted), you need the full stack or direct with
+  # env var — try both common ports.
+  ORDER_URL="${ORDER_URL:-http://localhost:8092}"
+  CART_URL="${CART_URL:-http://localhost:8090}"
+else
+  # Default: infra stack, direct to Docker ports
+  CART_URL="${CART_URL:-http://localhost:8090}"
+  ORDER_URL="${ORDER_URL:-http://localhost:8092}"
+  CHECKOUT_URL="${CHECKOUT_URL:-}"
+fi
+
+echo "═══════════════════════════════════════════════════════════════"
+echo "  UCP API Test Suite  —  mode: $MODE"
+echo "  CART:   ${CART_URL:-"(unreachable)"}"
+echo "  ORDER:  ${ORDER_URL:-"(unreachable)"}"
+echo "  CHECK:  ${CHECKOUT_URL:-"(unreachable)"}"
+echo "═══════════════════════════════════════════════════════════════"
+echo ""
+
+# ── Helpers ──────────────────────────────────────────────────────────────────
+pass() { echo "  ✅ $1"; }
+fail() { echo "  ❌ $1"; }
+header() { echo ""; echo "─── $1 ───"; }
+
+check_jq() {
+  if [ -z "$JQ" ]; then
+    echo "  ⚠️  jq not installed — showing raw JSON instead"
+  fi
+}
+
+maybe_jq() {
+  if [ -n "$JQ" ]; then
+    echo "$1" | jq "$2" 2>/dev/null || echo "$1" | head -c 200
+  else
+    echo "$1" | head -c 200
+  fi
+}
+
+assert_status() {
+  local label="$1" expected="$2" actual="$3" body="$4"
+  if [ "$actual" -eq "$expected" ]; then
+    pass "$label (HTTP $actual)"
+  else
+    fail "$label — expected HTTP $expected, got $actual"
+    echo "    body: $(echo "$body" | head -c 300)"
+  fi
+}
+
+# ══════════════════════════════════════════════════════════════════════════════
+# SECTION 1: Order service tests
+# ══════════════════════════════════════════════════════════════════════════════
+if [ -n "${ORDER_URL:-}" ]; then
+  header "1. Order Service  →  $ORDER_URL"
+
+  # ── Health ──────────────────────────────────────────────────────────────────
+  echo "--- 1.1 Health check ---"
+  resp=$(curl -sf "$ORDER_URL/healthz" 2>&1) && pass "/healthz" || fail "/healthz: $resp"
+
+  # ── Create order via checkout ───────────────────────────────────────────────
+  echo "--- 1.2 Create order via POST /checkout ---"
+  create_resp=$(curl -s -w '\n%{http_code}' -X POST "$ORDER_URL/checkout" \
+    -H 'Content-Type: application/json' \
+    -d '{
+      "orderReference": "ucp-test-1",
+      "currency": "SEK",
+      "lines": [
+        {
+          "reference": "l1",
+          "sku": "TEST-SKU-1",
+          "name": "Test Product",
+          "quantity": 2,
+          "unitPrice": 19900,
+          "taxRate": 2500
+        }
+      ]
+    }')
+  create_code=$(echo "$create_resp" | tail -1)
+  create_body=$(echo "$create_resp" | sed '$d')
+  assert_status "Create order" 201 "$create_code" "$create_body"
+  ORDER_ID=$(echo "$create_body" | sed -n 's/.*"orderId"[[:space:]]*:[[:space:]]*"\([^"]*\)".*/\1/p')
+  if [ -n "$ORDER_ID" ]; then
+    pass "Order ID: $ORDER_ID"
+  else
+    ORDER_ID="1"
+    fail "Could not extract order ID, using '$ORDER_ID'"
+    echo "    response: $(echo "$create_body" | head -c 400)"
+  fi
+
+  # ── Read order via UCP ──────────────────────────────────────────────────────
+  echo "--- 1.3 GET /ucp/v1/orders/{id} ---"
+  get_resp=$(curl -s -w '\n%{http_code}' "$ORDER_URL/ucp/v1/orders/$ORDER_ID")
+  get_code=$(echo "$get_resp" | tail -1)
+  get_body=$(echo "$get_resp" | sed '$d')
+  assert_status "GET UCP order" 200 "$get_code" "$get_body"
+  echo "    order: $(maybe_jq "$get_body" '.data.orderId + " status=" + .data.status')"
+
+  # ── Cancel order ────────────────────────────────────────────────────────────
+  echo "--- 1.4 POST /ucp/v1/orders/{id}/cancel ---"
+  cancel_resp=$(curl -s -w '\n%{http_code}' -X POST "$ORDER_URL/ucp/v1/orders/$ORDER_ID/cancel" \
+    -H 'Content-Type: application/json' \
+    -d '{"reason": "test cancellation"}')
+  cancel_code=$(echo "$cancel_resp" | tail -1)
+  cancel_body=$(echo "$cancel_resp" | sed '$d')
+  # May be 200 (cancelled) or 422 (already cancelled by flow) — both ok
+  if [ "$cancel_code" = "200" ] || [ "$cancel_code" = "422" ]; then
+    pass "Cancel order (HTTP $cancel_code)"
+    echo "    response: $(echo "$cancel_body" | head -c 200)"
+    if [ "$cancel_code" = "200" ]; then
+      ORDER_CANCELLED=true
+    fi
+  else
+    fail "Cancel order — expected 200 or 422, got $cancel_code"
+    echo "    body: $(echo "$cancel_body" | head -c 300)"
+  fi
+
+  # ── 404 for non-existent order ──────────────────────────────────────────────
+  echo "--- 1.5 GET non-existent order (404) ---"
+  notfound_resp=$(curl -s -w '\n%{http_code}' "$ORDER_URL/ucp/v1/orders/nonexistent")
+  notfound_code=$(echo "$notfound_resp" | tail -1)
+  notfound_body=$(echo "$notfound_resp" | sed '$d')
+  assert_status "GET non-existent" 404 "$notfound_code" "$notfound_body"
+
+  # ── Signature headers (if enabled) ──────────────────────────────────────────
+  echo "--- 1.6 Check signature headers ---"
+  sig_resp=$(curl -s -i "$ORDER_URL/ucp/v1/orders/$ORDER_ID" 2>/dev/null | head -30)
+  if echo "$sig_resp" | grep -qi "signature-input"; then
+    pass "Signature-Input header present"
+    echo "    $(echo "$sig_resp" | grep -i "signature-input" | head -1)"
+  else
+    echo "    ℹ️  No Signature-Input header (signing key not mounted — expected in infra stack)"
+  fi
+  if echo "$sig_resp" | grep -qi "^signature:"; then
+    pass "Signature header present"
+  else
+    echo "    ℹ️  No Signature header"
+  fi
+
+  echo ""
+fi
+
+# ══════════════════════════════════════════════════════════════════════════════
+# SECTION 2: Cart service tests
+# ══════════════════════════════════════════════════════════════════════════════
+if [ -n "${CART_URL:-}" ]; then
+  header "2. Cart Service  →  $CART_URL"
+
+  # ── Health ──────────────────────────────────────────────────────────────────
+  echo "--- 2.1 Health check ---"
+  resp=$(curl -sf "$CART_URL/healthz" 2>&1) && pass "/healthz" || fail "/healthz: $resp"
+
+  # ── Create cart via UCP ─────────────────────────────────────────────────────
+  echo "--- 2.2 POST /ucp/v1/carts/ (create cart) ---"
+  # Note: must use trailing slash — Go's ServeMux with StripPrefix only
+  # registers the subtree pattern (/ucp/v1/carts/) to avoid a redirect bug.
+  cart_resp=$(curl -s -w '\n%{http_code}' -X POST "$CART_URL/ucp/v1/carts/" \
+    -H 'Content-Type: application/json' \
+    -d '{
+      "currency": "SEK",
+      "country": "se",
+      "locale": "sv-SE"
+    }')
+  cart_code=$(echo "$cart_resp" | tail -1)
+  cart_body=$(echo "$cart_resp" | sed '$d')
+  assert_status "Create cart" 201 "$cart_code" "$cart_body"
+  CART_ID=$(echo "$cart_body" | sed -n 's/.*"id"[[:space:]]*:[[:space:]]*"\([^"]*\)".*/\1/p')
+  if [ -n "$CART_ID" ]; then
+    pass "Cart ID: $CART_ID"
+  else
+    CART_ID="1"
+    fail "Could not extract cart ID, using '$CART_ID'"
+    echo "    response: $(echo "$cart_body" | head -c 400)"
+  fi
+
+  # ── Add item to cart ────────────────────────────────────────────────────────
+  echo "--- 2.3 POST /ucp/v1/carts/{id}/items ---"
+  add_resp=$(curl -s -w '\n%{http_code}' -X POST "$CART_URL/ucp/v1/carts/$CART_ID/items" \
+    -H 'Content-Type: application/json' \
+    -d '{
+      "sku": "TEST-SKU-1",
+      "name": "Test Product",
+      "quantity": 1,
+      "unitPrice": 19900,
+      "taxRate": 2500
+    }')
+  add_code=$(echo "$add_resp" | tail -1)
+  add_body=$(echo "$add_resp" | sed '$d')
+  assert_status "Add item" 201 "$add_code" "$add_body"
+
+  # ── Get cart ────────────────────────────────────────────────────────────────
+  echo "--- 2.4 GET /ucp/v1/carts/{id} ---"
+  get_cart_resp=$(curl -s -w '\n%{http_code}' "$CART_URL/ucp/v1/carts/$CART_ID")
+  get_cart_code=$(echo "$get_cart_resp" | tail -1)
+  get_cart_body=$(echo "$get_cart_resp" | sed '$d')
+  assert_status "Get cart" 200 "$get_cart_code" "$get_cart_body"
+  echo "    total: $(echo "$get_cart_body" | sed -n 's/.*"total"[[:space:]]*:[[:space:]]*\([0-9]*\).*/\1/p')"
+
+  echo ""
+fi
+
+# ══════════════════════════════════════════════════════════════════════════════
+# SECTION 3: Full flow — cart → checkout → order (via edge/nginx only)
+# ══════════════════════════════════════════════════════════════════════════════
+if [ "$MODE" = "--edge" ] && [ -n "${CHECKOUT_URL:-}" ]; then
+  header "3. Full Flow (via nginx)"
+
+  # ── This section needs the full compose stack with nginx on :8080,
+  #    and checkout must be reachable. Skip for infra/direct modes.
+  echo "--- 3.1 Create checkout session ---"
+  checkout_resp=$(curl -s -w '\n%{http_code}' -X POST "$CHECKOUT_URL/ucp/v1/checkout-sessions" \
+    -H 'Content-Type: application/json' \
+    -d '{
+      "cartId": "'"$CART_ID"'",
+      "currency": "SEK",
+      "country": "se"
+    }')
+  checkout_code=$(echo "$checkout_resp" | tail -1)
+  checkout_body=$(echo "$checkout_resp" | sed '$d')
+  assert_status "Create checkout session" 201 "$checkout_code" "$checkout_body"
+fi
+
+# ══════════════════════════════════════════════════════════════════════════════
+# SECTION 4: Signature verification (standalone)
+# ══════════════════════════════════════════════════════════════════════════════
+if [ "$MODE" = "--verify-sig" ]; then
+  header "4. Signature Verification"
+
+  # Verify that the response includes RFC 9421 HTTP Message Signatures.
+  # Requires the service to have UCP_SIGNING_KEY_PATH set and the key mounted.
+  echo "--- 4.1 Check Signed Response ---"
+  sig_output=$(curl -s -D - "$ORDER_URL/ucp/v1/orders/$ORDER_ID" 2>/dev/null | head -40)
+
+  echo "$sig_output" | while IFS= read -r line; do
+    if echo "$line" | grep -qiE "(signature-input|signature:|x-ucp-timestamp|content-type)"; then
+      echo "    $line"
+    fi
+  done
+
+  echo ""
+  echo "  To manually verify:"
+  echo "    1. Extract the Signature-Input and Signature headers"
+  echo "    2. Reconstruct the signature base string per RFC 9421 §2.2"
+  echo "    3. Verify using the public key (x/y in docs/ucp-profile.json)"
+  echo ""
+fi
+
+# ══════════════════════════════════════════════════════════════════════════════
+echo "═══════════════════════════════════════════════════════════════"
+echo "  Done."
+echo ""
+echo "  Note: devProxies for /ucp/v1/* are now in islands.config.json."
+echo "  Run 'make dev' for same-origin proxied access."
+echo "═══════════════════════════════════════════════════════════════"

cart-grain.go

@@ -1,621 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"encoding/json"
-	"fmt"
-	"log"
-	"slices"
-	"sync"
-	"time"
-
-	messages "git.tornberg.me/go-cart-actor/proto"
-)
-
-type CartId [16]byte
-
-// String returns the cart id as a trimmed UTF-8 string (trailing zero bytes removed).
-func (id CartId) String() string {
-	n := 0
-	for n < len(id) && id[n] != 0 {
-		n++
-	}
-	return string(id[:n])
-}
-
-// ToCartId converts an arbitrary string to a fixed-size CartId (truncating or padding with zeros).
-func ToCartId(s string) CartId {
-	var id CartId
-	copy(id[:], []byte(s))
-	return id
-}
-
-func (id CartId) MarshalJSON() ([]byte, error) {
-	return json.Marshal(id.String())
-}
-
-func (id *CartId) UnmarshalJSON(data []byte) error {
-	var str string
-	err := json.Unmarshal(data, &str)
-	if err != nil {
-		return err
-	}
-	copy(id[:], []byte(str))
-	return nil
-}
-
-type StockStatus int
-
-const (
-	OutOfStock StockStatus = 0
-	LowStock   StockStatus = 1
-	InStock    StockStatus = 2
-)
-
-type CartItem struct {
-	Id          int         `json:"id"`
-	ItemId      int         `json:"itemId,omitempty"`
-	ParentId    int         `json:"parentId,omitempty"`
-	Sku         string      `json:"sku"`
-	Name        string      `json:"name"`
-	Price       int64       `json:"price"`
-	TotalPrice  int64       `json:"totalPrice"`
-	TotalTax    int64       `json:"totalTax"`
-	OrgPrice    int64       `json:"orgPrice"`
-	Stock       StockStatus `json:"stock"`
-	Quantity    int         `json:"qty"`
-	Tax         int         `json:"tax"`
-	TaxRate     int         `json:"taxRate"`
-	Brand       string      `json:"brand,omitempty"`
-	Category    string      `json:"category,omitempty"`
-	Category2   string      `json:"category2,omitempty"`
-	Category3   string      `json:"category3,omitempty"`
-	Category4   string      `json:"category4,omitempty"`
-	Category5   string      `json:"category5,omitempty"`
-	Disclaimer  string      `json:"disclaimer,omitempty"`
-	SellerId    string      `json:"sellerId,omitempty"`
-	SellerName  string      `json:"sellerName,omitempty"`
-	ArticleType string      `json:"type,omitempty"`
-	Image       string      `json:"image,omitempty"`
-	Outlet      *string     `json:"outlet,omitempty"`
-	StoreId     *string     `json:"storeId,omitempty"`
-}
-
-type CartDelivery struct {
-	Id          int                   `json:"id"`
-	Provider    string                `json:"provider"`
-	Price       int64                 `json:"price"`
-	Items       []int                 `json:"items"`
-	PickupPoint *messages.PickupPoint `json:"pickupPoint,omitempty"`
-}
-
-type CartGrain struct {
-	mu                sync.RWMutex
-	lastItemId        int
-	lastDeliveryId    int
-	storageMessages   []Message
-	Id                CartId          `json:"id"`
-	Items             []*CartItem     `json:"items"`
-	TotalPrice        int64           `json:"totalPrice"`
-	TotalTax          int64           `json:"totalTax"`
-	TotalDiscount     int64           `json:"totalDiscount"`
-	Deliveries        []*CartDelivery `json:"deliveries,omitempty"`
-	Processing        bool            `json:"processing"`
-	PaymentInProgress bool            `json:"paymentInProgress"`
-	OrderReference    string          `json:"orderReference,omitempty"`
-	PaymentStatus     string          `json:"paymentStatus,omitempty"`
-}
-
-type Grain interface {
-	GetId() CartId
-	HandleMessage(message *Message, isReplay bool) (*FrameWithPayload, error)
-	GetCurrentState() (*FrameWithPayload, error)
-}
-
-func (c *CartGrain) GetId() CartId {
-	return c.Id
-}
-
-func (c *CartGrain) GetLastChange() int64 {
-	if len(c.storageMessages) == 0 {
-		return 0
-	}
-	return *c.storageMessages[len(c.storageMessages)-1].TimeStamp
-}
-
-func (c *CartGrain) GetCurrentState() (*FrameWithPayload, error) {
-	result, err := json.Marshal(c)
-	if err != nil {
-		ret := MakeFrameWithPayload(0, 400, []byte(err.Error()))
-		return &ret, nil
-	}
-	ret := MakeFrameWithPayload(0, 200, result)
-	return &ret, nil
-}
-
-func getInt(data float64, ok bool) (int, error) {
-	if !ok {
-		return 0, fmt.Errorf("invalid type")
-	}
-	return int(data), nil
-}
-
-func getItemData(sku string, qty int, country string) (*messages.AddItem, error) {
-	item, err := FetchItem(sku, country)
-	if err != nil {
-		return nil, err
-	}
-	orgPrice, _ := getInt(item.GetNumberFieldValue(5)) // getInt(item.Fields[5])
-
-	price, priceErr := getInt(item.GetNumberFieldValue(4)) //Fields[4]
-
-	if priceErr != nil {
-		return nil, fmt.Errorf("invalid price")
-	}
-
-	stock := InStock
-	/*item.t
-	if item.StockLevel == "0" || item.StockLevel == "" {
-		stock = OutOfStock
-	} else if item.StockLevel == "5+" {
-		stock = LowStock
-		}*/
-	articleType, _ := item.GetStringFieldValue(1)   //.Fields[1].(string)
-	outletGrade, ok := item.GetStringFieldValue(20) //.Fields[20].(string)
-	var outlet *string
-	if ok {
-		outlet = &outletGrade
-	}
-	sellerId, _ := item.GetStringFieldValue(24)  // .Fields[24].(string)
-	sellerName, _ := item.GetStringFieldValue(9) // .Fields[9].(string)
-
-	brand, _ := item.GetStringFieldValue(2)      //.Fields[2].(string)
-	category, _ := item.GetStringFieldValue(10)  //.Fields[10].(string)
-	category2, _ := item.GetStringFieldValue(11) //.Fields[11].(string)
-	category3, _ := item.GetStringFieldValue(12) //.Fields[12].(string)
-	category4, _ := item.GetStringFieldValue(13) //Fields[13].(string)
-	category5, _ := item.GetStringFieldValue(14) //.Fields[14].(string)
-
-	return &messages.AddItem{
-		ItemId:      int64(item.Id),
-		Quantity:    int32(qty),
-		Price:       int64(price),
-		OrgPrice:    int64(orgPrice),
-		Sku:         sku,
-		Name:        item.Title,
-		Image:       item.Img,
-		Stock:       int32(stock),
-		Brand:       brand,
-		Category:    category,
-		Category2:   category2,
-		Category3:   category3,
-		Category4:   category4,
-		Category5:   category5,
-		Tax:         2500,
-		SellerId:    sellerId,
-		SellerName:  sellerName,
-		ArticleType: articleType,
-		Disclaimer:  item.Disclaimer,
-		Country:     country,
-		Outlet:      outlet,
-	}, nil
-}
-
-func (c *CartGrain) AddItem(sku string, qty int, country string, storeId *string) (*FrameWithPayload, error) {
-	cartItem, err := getItemData(sku, qty, country)
-	if err != nil {
-		return nil, err
-	}
-	cartItem.StoreId = storeId
-	return c.HandleMessage(&Message{
-		Type:    2,
-		Content: cartItem,
-	}, false)
-}
-
-func (c *CartGrain) GetStorageMessage(since int64) []StorableMessage {
-	c.mu.RLock()
-	defer c.mu.RUnlock()
-	ret := make([]StorableMessage, 0)
-
-	for _, message := range c.storageMessages {
-		if *message.TimeStamp > since {
-			ret = append(ret, message)
-		}
-	}
-	return ret
-}
-
-func (c *CartGrain) GetState() ([]byte, error) {
-	return json.Marshal(c)
-}
-
-func (c *CartGrain) ItemsWithDelivery() []int {
-	ret := make([]int, 0, len(c.Items))
-	for _, item := range c.Items {
-		for _, delivery := range c.Deliveries {
-			for _, id := range delivery.Items {
-				if item.Id == id {
-					ret = append(ret, id)
-				}
-			}
-		}
-	}
-	return ret
-}
-
-func (c *CartGrain) ItemsWithoutDelivery() []int {
-	ret := make([]int, 0, len(c.Items))
-	hasDelivery := c.ItemsWithDelivery()
-	for _, item := range c.Items {
-		found := false
-		for _, id := range hasDelivery {
-			if item.Id == id {
-				found = true
-				break
-			}
-		}
-
-		if !found {
-			ret = append(ret, item.Id)
-		}
-	}
-	return ret
-}
-
-func (c *CartGrain) FindItemWithSku(sku string) (*CartItem, bool) {
-	c.mu.RLock()
-	defer c.mu.RUnlock()
-	for _, item := range c.Items {
-		if item.Sku == sku {
-			return item, true
-		}
-	}
-	return nil, false
-}
-
-func GetTaxAmount(total int64, tax int) int64 {
-	taxD := 10000 / float64(tax)
-	return int64(float64(total) / float64((1 + taxD)))
-}
-
-func (c *CartGrain) HandleMessage(message *Message, isReplay bool) (*FrameWithPayload, error) {
-	if message.TimeStamp == nil {
-		now := time.Now().Unix()
-		message.TimeStamp = &now
-	}
-	grainMutations.Inc()
-	var err error
-	switch message.Type {
-	case SetCartItemsType:
-		msg, ok := message.Content.(*messages.SetCartRequest)
-		if !ok {
-			err = fmt.Errorf("expected SetCartItems")
-		} else {
-
-			c.mu.Lock()
-			c.Items = make([]*CartItem, 0, len(msg.Items))
-			c.mu.Unlock()
-			for _, item := range msg.Items {
-				c.AddItem(item.Sku, int(item.Quantity), item.Country, item.StoreId)
-			}
-
-		}
-	case AddRequestType:
-		msg, ok := message.Content.(*messages.AddRequest)
-		if !ok {
-			err = fmt.Errorf("expected AddRequest")
-		} else {
-
-			existingItem, found := c.FindItemWithSku(msg.Sku)
-			if found {
-				existingItem.Quantity += int(msg.Quantity)
-				c.UpdateTotals()
-			} else {
-				return c.AddItem(msg.Sku, int(msg.Quantity), msg.Country, msg.StoreId)
-			}
-
-		}
-	case AddItemType:
-		msg, ok := message.Content.(*messages.AddItem)
-		if !ok {
-			err = fmt.Errorf("expected AddItem")
-		} else {
-
-			if msg.Quantity < 1 {
-				return nil, fmt.Errorf("invalid quantity")
-			}
-			existingItem, found := c.FindItemWithSku(msg.Sku)
-			if found {
-				existingItem.Quantity += int(msg.Quantity)
-				c.UpdateTotals()
-			} else {
-				c.mu.Lock()
-				c.lastItemId++
-				tax := 2500
-				if msg.Tax > 0 {
-					tax = int(msg.Tax)
-				}
-
-				taxAmount := GetTaxAmount(msg.Price, tax)
-
-				c.Items = append(c.Items, &CartItem{
-					Id:          c.lastItemId,
-					ItemId:      int(msg.ItemId),
-					Quantity:    int(msg.Quantity),
-					Sku:         msg.Sku,
-					Name:        msg.Name,
-					Price:       msg.Price,
-					TotalPrice:  msg.Price * int64(msg.Quantity),
-					TotalTax:    int64(taxAmount * int64(msg.Quantity)),
-					Image:       msg.Image,
-					Stock:       StockStatus(msg.Stock),
-					Disclaimer:  msg.Disclaimer,
-					Brand:       msg.Brand,
-					Category:    msg.Category,
-					Category2:   msg.Category2,
-					Category3:   msg.Category3,
-					Category4:   msg.Category4,
-					Category5:   msg.Category5,
-					OrgPrice:    msg.OrgPrice,
-					ArticleType: msg.ArticleType,
-					Outlet:      msg.Outlet,
-					SellerId:    msg.SellerId,
-					SellerName:  msg.SellerName,
-					Tax:         int(taxAmount),
-					TaxRate:     tax,
-					StoreId:     msg.StoreId,
-				})
-				c.UpdateTotals()
-				c.mu.Unlock()
-			}
-
-		}
-	case ChangeQuantityType:
-		msg, ok := message.Content.(*messages.ChangeQuantity)
-		if !ok {
-			err = fmt.Errorf("expected ChangeQuantity")
-		} else {
-
-			for i, item := range c.Items {
-				if item.Id == int(msg.Id) {
-					if msg.Quantity <= 0 {
-						//c.TotalPrice -= item.Price * int64(item.Quantity)
-						c.Items = append(c.Items[:i], c.Items[i+1:]...)
-					} else {
-						//diff := int(msg.Quantity) - item.Quantity
-						item.Quantity = int(msg.Quantity)
-						//c.TotalPrice += item.Price * int64(diff)
-					}
-
-					break
-				}
-			}
-			c.UpdateTotals()
-
-		}
-	case RemoveItemType:
-		msg, ok := message.Content.(*messages.RemoveItem)
-		if !ok {
-			err = fmt.Errorf("expected RemoveItem")
-		} else {
-
-			items := make([]*CartItem, 0, len(c.Items))
-			for _, item := range c.Items {
-				if item.Id == int(msg.Id) {
-					//c.TotalPrice -= item.Price * int64(item.Quantity)
-				} else {
-					items = append(items, item)
-				}
-			}
-			c.Items = items
-			c.UpdateTotals()
-		}
-	case SetDeliveryType:
-		msg, ok := message.Content.(*messages.SetDelivery)
-		if !ok {
-			err = fmt.Errorf("expected SetDelivery")
-		} else {
-
-			c.lastDeliveryId++
-			items := make([]int, 0)
-			withDelivery := c.ItemsWithDelivery()
-			if len(msg.Items) == 0 {
-				items = append(items, c.ItemsWithoutDelivery()...)
-			} else {
-				for _, id := range msg.Items {
-					for _, item := range c.Items {
-						if item.Id == int(id) {
-							if slices.Contains(withDelivery, item.Id) {
-								return nil, fmt.Errorf("item already has delivery")
-							}
-							items = append(items, int(item.Id))
-							break
-						}
-					}
-				}
-			}
-			if len(items) > 0 {
-				c.Deliveries = append(c.Deliveries, &CartDelivery{
-					Id:          c.lastDeliveryId,
-					Provider:    msg.Provider,
-					PickupPoint: msg.PickupPoint,
-					Price:       4900,
-					Items:       items,
-				})
-
-				c.UpdateTotals()
-
-			}
-
-		}
-	case RemoveDeliveryType:
-		msg, ok := message.Content.(*messages.RemoveDelivery)
-		if !ok {
-			err = fmt.Errorf("expected RemoveDelivery")
-		} else {
-
-			deliveries := make([]*CartDelivery, 0, len(c.Deliveries))
-			for _, delivery := range c.Deliveries {
-				if delivery.Id == int(msg.Id) {
-					c.TotalPrice -= delivery.Price
-				} else {
-					deliveries = append(deliveries, delivery)
-				}
-			}
-			c.Deliveries = deliveries
-			c.UpdateTotals()
-		}
-	case SetPickupPointType:
-		msg, ok := message.Content.(*messages.SetPickupPoint)
-		if !ok {
-			err = fmt.Errorf("expected SetPickupPoint")
-		} else {
-
-			for _, delivery := range c.Deliveries {
-				if delivery.Id == int(msg.DeliveryId) {
-					delivery.PickupPoint = &messages.PickupPoint{
-						Id:      msg.Id,
-						Address: msg.Address,
-						City:    msg.City,
-						Zip:     msg.Zip,
-						Country: msg.Country,
-						Name:    msg.Name,
-					}
-					break
-				}
-			}
-
-		}
-	case CreateCheckoutOrderType:
-		msg, ok := message.Content.(*messages.CreateCheckoutOrder)
-		if !ok {
-			err = fmt.Errorf("expected CreateCheckoutOrder")
-		} else {
-
-			orderLines := make([]*Line, 0, len(c.Items))
-
-			c.PaymentInProgress = true
-			c.Processing = true
-			for _, item := range c.Items {
-
-				orderLines = append(orderLines, &Line{
-					Type:           "physical",
-					Reference:      item.Sku,
-					Name:           item.Name,
-					Quantity:       item.Quantity,
-					UnitPrice:      int(item.Price),
-					TaxRate:        2500, // item.TaxRate,
-					QuantityUnit:   "st",
-					TotalAmount:    int(item.TotalPrice),
-					TotalTaxAmount: int(item.TotalTax),
-					ImageURL:       fmt.Sprintf("https://www.elgiganten.se%s", item.Image),
-				})
-			}
-			for _, line := range c.Deliveries {
-				if line.Price > 0 {
-					orderLines = append(orderLines, &Line{
-						Type:           "shipping_fee",
-						Reference:      line.Provider,
-						Name:           "Delivery",
-						Quantity:       1,
-						UnitPrice:      int(line.Price),
-						TaxRate:        2500, // item.TaxRate,
-						QuantityUnit:   "st",
-						TotalAmount:    int(line.Price),
-						TotalTaxAmount: int(GetTaxAmount(line.Price, 2500)),
-					})
-				}
-			}
-			order := CheckoutOrder{
-				PurchaseCountry:    "SE",
-				PurchaseCurrency:   "SEK",
-				Locale:             "sv-se",
-				OrderAmount:        int(c.TotalPrice),
-				OrderTaxAmount:     int(c.TotalTax),
-				OrderLines:         orderLines,
-				MerchantReference1: c.Id.String(),
-				MerchantURLS: &CheckoutMerchantURLS{
-					Terms:        msg.Terms,
-					Checkout:     msg.Checkout,
-					Confirmation: msg.Confirmation,
-					Validation:   msg.Validation,
-					Push:         msg.Push,
-				},
-			}
-			orderPayload, err := json.Marshal(order)
-			if err != nil {
-				return nil, err
-			}
-			var klarnaOrder *CheckoutOrder
-			if c.OrderReference != "" {
-				log.Printf("Updating order id %s", c.OrderReference)
-				klarnaOrder, err = KlarnaInstance.UpdateOrder(c.OrderReference, bytes.NewReader(orderPayload))
-			} else {
-				klarnaOrder, err = KlarnaInstance.CreateOrder(bytes.NewReader(orderPayload))
-			}
-			// log.Printf("Order result: %+v", klarnaOrder)
-			if nil != err {
-				log.Printf("error from klarna: %v", err)
-				return nil, err
-			}
-			if c.OrderReference == "" {
-				c.OrderReference = klarnaOrder.ID
-				c.PaymentStatus = klarnaOrder.Status
-			}
-
-			orderData, err := json.Marshal(klarnaOrder)
-			if nil != err {
-				return nil, err
-			}
-
-			result := MakeFrameWithPayload(RemoteCreateOrderReply, 200, orderData)
-			return &result, nil
-		}
-	case OrderCompletedType:
-		msg, ok := message.Content.(*messages.OrderCreated)
-		if !ok {
-			log.Printf("expected OrderCompleted, got %T", message.Content)
-			err = fmt.Errorf("expected OrderCompleted")
-		} else {
-			c.OrderReference = msg.OrderId
-			c.PaymentStatus = msg.Status
-			c.PaymentInProgress = false
-		}
-	default:
-		err = fmt.Errorf("unknown message type %d", message.Type)
-	}
-	if err != nil {
-		return nil, err
-	}
-
-	if !isReplay {
-		c.mu.Lock()
-		c.storageMessages = append(c.storageMessages, *message)
-		c.mu.Unlock()
-	}
-	result, err := json.Marshal(c)
-	msg := MakeFrameWithPayload(RemoteHandleMutationReply, 200, result)
-	return &msg, err
-}
-
-func (c *CartGrain) UpdateTotals() {
-	c.TotalPrice = 0
-	c.TotalTax = 0
-	c.TotalDiscount = 0
-	for _, item := range c.Items {
-		rowTotal := item.Price * int64(item.Quantity)
-		rowTax := int64(item.Tax) * int64(item.Quantity)
-		item.TotalPrice = rowTotal
-		item.TotalTax = rowTax
-		c.TotalPrice += rowTotal
-		c.TotalTax += rowTax
-		itemDiff := max(0, item.OrgPrice-item.Price)
-		c.TotalDiscount += itemDiff * int64(item.Quantity)
-	}
-	for _, delivery := range c.Deliveries {
-		c.TotalPrice += delivery.Price
-		c.TotalTax += GetTaxAmount(delivery.Price, 2500)
-	}
-
-}

cmd/backoffice/main.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"log"
+	"net/http"
+	"os"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/backofficeadmin"
+	amqp "github.com/rabbitmq/amqp091-go"
+)
+
+func envOrDefault(key, def string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return def
+}
+
+func main() {
+	addr := envOrDefault("ADDR", ":8080")
+	amqpURL := os.Getenv("AMQP_URL")
+
+	app, err := backofficeadmin.New(backofficeadmin.Config{
+		DataDir:         envOrDefault("CART_DIR", "data"),
+		CheckoutDataDir: envOrDefault("CHECKOUT_DIR", "checkout-data"),
+		RedisAddress:    os.Getenv("REDIS_ADDRESS"),
+		RedisPassword:   os.Getenv("REDIS_PASSWORD"),
+	})
+	if err != nil {
+		log.Fatalf("Error creating backoffice: %v", err)
+	}
+
+	mux := http.NewServeMux()
+	app.RegisterRoutes(mux)
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("ok"))
+	})
+	mux.HandleFunc("/readyz", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("ok"))
+	})
+	mux.HandleFunc("/livez", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("ok"))
+	})
+
+	// Global CORS middleware allowing all origins and handling preflight.
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Access-Control-Allow-Origin", "*")
+		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, PATCH, DELETE, OPTIONS")
+		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization, X-Requested-With")
+		w.Header().Set("Access-Control-Expose-Headers", "*")
+		if r.Method == http.MethodOptions {
+			w.WriteHeader(http.StatusNoContent)
+			return
+		}
+		mux.ServeHTTP(w, r)
+	})
+
+	srv := &http.Server{
+		Addr:         addr,
+		Handler:      handler,
+		ReadTimeout:  15 * time.Second,
+		WriteTimeout: 30 * time.Second,
+		IdleTimeout:  60 * time.Second,
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	var conn *amqp.Connection
+	if amqpURL != "" {
+		conn, err = amqp.Dial(amqpURL)
+		if err != nil {
+			log.Fatalf("failed to connect to RabbitMQ: %v", err)
+		}
+	}
+	if err := app.Start(ctx, conn); err != nil {
+		log.Printf("AMQP listener disabled: %v", err)
+	} else if conn != nil {
+		log.Printf("AMQP listener connected")
+	}
+
+	log.Printf("backoffice HTTP listening on %s", addr)
+	if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+		log.Fatalf("http server error: %v", err)
+	}
+}

cmd/cart/k8s-host-discovery.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"log"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/discovery"
+	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
+)
+
+func GetDiscovery() discovery.Discovery {
+	if podIp == "" {
+		return nil
+	}
+
+	config, kerr := rest.InClusterConfig()
+
+	if kerr != nil {
+		log.Fatalf("Error creating kubernetes client: %v\n", kerr)
+	}
+	client, err := kubernetes.NewForConfig(config)
+	if err != nil {
+		log.Fatalf("Error creating client: %v\n", err)
+	}
+	timeout := int64(30)
+	return discovery.NewK8sDiscovery(client, v1.ListOptions{
+		LabelSelector:  "actor-pool=cart",
+		TimeoutSeconds: &timeout,
+	})
+}
+
+func UseDiscovery(pool discovery.DiscoveryTarget) {
+
+	go func(hw discovery.Discovery) {
+		if hw == nil {
+			log.Print("No discovery service available")
+			return
+		}
+		ch, err := hw.Watch()
+		if err != nil {
+			log.Printf("Discovery error: %v", err)
+			return
+		}
+		for evt := range ch {
+			if evt.Host == "" {
+				continue
+			}
+			switch evt.IsReady {
+			case false:
+				if pool.IsKnown(evt.Host) {
+					log.Printf("Host %s is not ready, removing", evt.Host)
+					pool.RemoveHost(evt.Host)
+				}
+			default:
+				if !pool.IsKnown(evt.Host) {
+					log.Printf("Discovered host %s", evt.Host)
+					pool.AddRemoteHost(evt.Host)
+				}
+			}
+		}
+	}(GetDiscovery())
+}

cmd/cart/main.go

@@ -0,0 +1,426 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net"
+	"net/http"
+	"net/http/pprof"
+	"os"
+	"os/signal"
+	"strings"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	cartmcp "git.k6n.net/mats/go-cart-actor/pkg/cart/mcp"
+	"git.k6n.net/mats/go-cart-actor/pkg/promotions"
+	"git.k6n.net/mats/go-cart-actor/internal/ucp"
+	"git.k6n.net/mats/go-cart-actor/pkg/proxy"
+	"git.k6n.net/mats/go-cart-actor/pkg/voucher"
+	"git.k6n.net/mats/go-redis-inventory/pkg/inventory"
+	"git.k6n.net/mats/slask-finder/pkg/messaging"
+	amqp "github.com/rabbitmq/amqp091-go"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+)
+
+var (
+	grainSpawns = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_grain_spawned_total",
+		Help: "The total number of spawned grains",
+	})
+)
+
+func init() {
+	os.Mkdir("data", 0755)
+}
+
+type App struct {
+	pool   *actor.SimpleGrainPool[cart.CartGrain]
+	server *PoolServer
+}
+
+var podIp = os.Getenv("POD_IP")
+var name = os.Getenv("POD_NAME")
+var amqpUrl = os.Getenv("AMQP_URL")
+var redisAddress = os.Getenv("REDIS_ADDRESS")
+var redisPassword = os.Getenv("REDIS_PASSWORD")
+
+// getEnv returns the value of the environment variable named by key, or def if unset/empty.
+func getEnv(key, def string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return def
+}
+
+// normalizeListenAddr accepts either a bare port ("8080") or a full listen
+// address (":8080", "0.0.0.0:8080") and returns a value usable by http.Server.Addr.
+func normalizeListenAddr(v string) string {
+	if strings.Contains(v, ":") {
+		return v
+	}
+	return ":" + v
+}
+
+// loadUCPCartSigner loads the UCP ECDSA signing key from the path specified in
+// the UCP_SIGNING_KEY_PATH environment variable. Returns nil if unset or unreadable.
+func loadUCPCartSigner() *ucp.SigningConfig {
+	path := os.Getenv("UCP_SIGNING_KEY_PATH")
+	if path == "" {
+		return nil
+	}
+	pemData, err := os.ReadFile(path)
+	if err != nil {
+		log.Printf("ucp signing: cannot read key %s: %v", path, err)
+		return nil
+	}
+	cfg, err := ucp.NewSigningConfigFromPEM(pemData, "k6n-ecdsa-2026")
+	if err != nil {
+		log.Printf("ucp signing: invalid key at %s: %v", path, err)
+		return nil
+	}
+	return cfg
+}
+
+func getCountryFromHost(host string) string {
+	if strings.Contains(strings.ToLower(host), "-no") {
+		return "no"
+	}
+	if strings.Contains(strings.ToLower(host), "-se") {
+		return "se"
+	}
+	return "se"
+}
+
+type MutationContext struct {
+	VoucherService voucher.Service
+}
+
+type CartChangeEvent struct {
+	CartId    cart.CartId         `json:"cartId"`
+	Mutations []actor.ApplyResult `json:"mutations"`
+}
+
+func matchesSkuAndLocation(update inventory.InventoryResult, item cart.CartItem) bool {
+	if string(update.SKU) == item.Sku {
+		if update.LocationID == "se" && item.StoreId == nil {
+			return true
+		}
+		if item.StoreId == nil {
+			return false
+		}
+		if *item.StoreId == string(update.LocationID) {
+			return true
+		}
+	}
+	return false
+}
+
+func main() {
+
+	// cartPort is the bare HTTP port. It drives both the local listener and the
+	// port used to proxy to peer pods, so a cluster must run all pods on the
+	// same CART_PORT.
+	cartPort := getEnv("CART_PORT", "8080")
+	if i := strings.LastIndex(cartPort, ":"); i >= 0 {
+		cartPort = cartPort[i+1:]
+	}
+
+	controlPlaneConfig := actor.DefaultServerConfig()
+
+	promotionStore, err := promotions.NewStore("data/promotions.json")
+	if err != nil {
+		log.Fatalf("Error loading promotions: %v\n", err)
+	}
+
+	log.Printf("loaded %d promotions", len(promotionStore.List()))
+
+	promotionService := promotions.NewPromotionService(nil)
+
+	//inventoryPubSub := actor.NewPubSub[inventory.InventoryChange]()
+
+	// rdb := redis.NewClient(&redis.Options{
+	// 	Addr:     redisAddress,
+	// 	Password: redisPassword,
+	// 	DB:       0,
+	// })
+	// inventoryService, err := inventory.NewRedisInventoryService(rdb)
+	// if err != nil {
+	// 	log.Fatalf("Error creating inventory service: %v\n", err)
+	// }
+
+	// inventoryReservationService, err := inventory.NewRedisCartReservationService(rdb)
+	// if err != nil {
+	// 	log.Fatalf("Error creating inventory reservation service: %v\n", err)
+	// }
+
+	reg := cart.NewCartMultationRegistry(cart.NewCartMutationContext(nil))
+	reg.RegisterProcessor(
+		actor.NewMutationProcessor(func(ctx context.Context, g *cart.CartGrain) error {
+			_, span := tracer.Start(ctx, "Totals and promotions")
+			defer span.End()
+			g.UpdateTotals()
+			// Evaluate active promotions against the freshly-totalled cart and apply
+			// any matched actions (e.g. the Volymrabatt volume discount), which adjust
+			// TotalPrice/TotalDiscount on top of line items and vouchers.
+			promotionCtx := promotions.NewContextFromCart(g, promotions.WithNow(time.Now()))
+			results, _ := promotionService.EvaluateAll(promotionStore.Snapshot(), promotionCtx)
+			// ApplyResults applies qualifying actions in priority order and records
+			// every effect — both applied discounts and pending "spend X more for ..."
+			// nudges with their progress — in g.AppliedPromotions.
+			promotionService.ApplyResults(g, results, promotionCtx)
+			g.Version++
+			return nil
+		}),
+	)
+
+	diskStorage := actor.NewDiskStorage[cart.CartGrain](getEnv("CART_DIR", "data"), reg)
+	poolConfig := actor.GrainPoolConfig[cart.CartGrain]{
+		MutationRegistry: reg,
+		Storage:          diskStorage,
+		Spawn: func(ctx context.Context, id uint64) (actor.Grain[cart.CartGrain], error) {
+			_, span := tracer.Start(ctx, fmt.Sprintf("Spawn cart id %d", id))
+			defer span.End()
+			grainSpawns.Inc()
+			ret := cart.NewCartGrain(id, time.Now())
+			// Set baseline lastChange at spawn; replay may update it to last event timestamp.
+
+			// inventoryPubSub.Subscribe(ret.HandleInventoryChange)
+			err := diskStorage.LoadEvents(ctx, id, ret)
+			// if err == nil && inventoryService != nil {
+			// 	refs := make([]*inventory.InventoryReference, 0)
+			// 	for _, item := range ret.Items {
+			// 		refs = append(refs, &inventory.InventoryReference{
+			// 			SKU:        inventory.SKU(item.Sku),
+			// 			LocationID: getLocationId(item),
+			// 		})
+			// 	}
+			// 	_, span := tracer.Start(ctx, "update inventory")
+			// 	defer span.End()
+			// 	res, err := inventoryService.GetInventoryBatch(ctx, refs...)
+			// 	if err != nil {
+			// 		log.Printf("unable to update inventory %v", err)
+			// 	} else {
+			// 		for _, update := range res {
+			// 			for _, item := range ret.Items {
+			// 				if matchesSkuAndLocation(update, *item) && update.Quantity != uint32(item.Stock) {
+			// 					// maybe apply an update to give visibility to the cart
+			// 					item.Stock = uint16(update.Quantity)
+			// 				}
+			// 			}
+			// 		}
+			// 	}
+			// }
+
+			return ret, err
+		},
+		Destroy: func(grain actor.Grain[cart.CartGrain]) error {
+			// cart, err := grain.GetCurrentState()
+			// if err != nil {
+			// 	return err
+			// }
+			//inventoryPubSub.Unsubscribe(cart.HandleInventoryChange)
+
+			return nil
+		},
+		SpawnHost: func(host string) (actor.Host[cart.CartGrain], error) {
+			return proxy.NewRemoteHost[cart.CartGrain](host, cartPort)
+		},
+		TTL:      5 * time.Minute,
+		PoolSize: 2 * 65535,
+		Hostname: podIp,
+	}
+
+	pool, err := actor.NewSimpleGrainPool(poolConfig)
+	if err != nil {
+		log.Fatalf("Error creating cart pool: %v\n", err)
+	}
+
+	cartMCP := cartmcp.New(pool)
+
+	// Publish each applied mutation to the "cart"/"mutation" RabbitMQ topic so the
+	// backoffice /commerce live feed (and other consumers) see cart activity.
+	// Best-effort: if AMQP is unreachable the cart still serves; the feed stays empty.
+	if amqpUrl != "" {
+		if conn, derr := amqp.Dial(amqpUrl); derr != nil {
+			log.Printf("cart: AMQP connect failed, mutation feed disabled: %v", derr)
+		} else {
+			if ch, cerr := conn.Channel(); cerr == nil {
+				_ = messaging.DefineTopic(ch, "cart", "mutation") // idempotent; non-fatal
+				_ = ch.Close()
+			}
+			pool.AddListener(actor.NewAmqpListener(conn, func(id uint64, results []actor.ApplyResult) (any, error) {
+				types := make([]string, 0, len(results))
+				for _, r := range results {
+					types = append(types, r.Type)
+				}
+				return map[string]any{"cartId": id, "mutations": types}, nil
+			}))
+			log.Printf("cart: mutation feed enabled (cart/mutation)")
+		}
+	}
+
+	syncedServer := NewPoolServer(pool, fmt.Sprintf("%s, %s", name, podIp)) //inventoryService, inventoryReservationService)
+
+	app := &App{
+		pool:   pool,
+		server: syncedServer,
+	}
+
+	mux := http.NewServeMux()
+	debugMux := http.NewServeMux()
+
+	grpcSrv, err := actor.NewControlServer[cart.CartGrain](controlPlaneConfig, pool)
+	if err != nil {
+		log.Fatalf("Error starting control plane gRPC server: %v\n", err)
+	}
+	defer grpcSrv.GracefulStop()
+
+	// go diskStorage.SaveLoop(10 * time.Second)
+	UseDiscovery(pool)
+
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
+	defer stop()
+
+	otelShutdown, err := setupOTelSDK(ctx)
+	if err != nil {
+		log.Fatalf("Unable to start otel %v", err)
+	}
+
+	syncedServer.Serve(mux)
+
+	// Cart MCP edge: inspect and mutate carts — get_cart, get_cart_items,
+	// update_item_quantity, remove_cart_item, clear_cart, apply_voucher, etc.
+	// Exposes 11 tools on the same grain pool, mounted at /cart-mcp so it does
+	// not conflict with the Promotions MCP at /promotions-mcp.
+	mux.Handle("/cart-mcp", cartMCP.Handler())
+	mux.Handle("/cart-mcp/", cartMCP.Handler())
+
+	// UCP REST adapter — Universal Commerce Protocol
+	cartUCP := ucp.CartHandler(pool)
+	if signer := loadUCPCartSigner(); signer != nil {
+		cartUCP = ucp.WithSigning(cartUCP, signer)
+		log.Print("ucp signing enabled")
+	}
+	// StripPrefix is required because the sub-mux (CartHandler) registers
+	// routes like "GET /{id}" which expect a relative path; Go's ServeMux
+	// passes the full request path (e.g. /ucp/v1/carts/123) without stripping
+	// the prefix, so the sub-mux would never match.
+	//
+	// Only the subtree pattern (/ucp/v1/carts/) is registered, NOT the exact
+	// pattern (/ucp/v1/carts), because registering both causes Go's ServeMux
+	// to redirect the exact match to the subtree root, and StripPrefix
+	// interferes with the redirect target (producing a 307 to "/" instead
+	// of "/ucp/v1/carts/"). Consumers should use the trailing-slash variant.
+	mux.Handle("/ucp/v1/carts/", http.StripPrefix("/ucp/v1/carts", cartUCP))
+
+	// Stateless promotion evaluation: POST a (possibly partial) eval context and
+	// get back the resulting totals plus the applied/pending effect breakdown,
+	// without creating or mutating a real cart.
+	mux.HandleFunc("POST /promotions/evaluate", newPromotionEvaluateHandler(promotionStore, promotionService))
+
+	// only for local
+	mux.HandleFunc("GET /add/remote/{host}", func(w http.ResponseWriter, r *http.Request) {
+		pool.AddRemote(r.PathValue("host"))
+	})
+
+	debugMux.HandleFunc("/debug/pprof/", pprof.Index)
+	debugMux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
+	debugMux.HandleFunc("/debug/pprof/profile", pprof.Profile)
+	debugMux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
+	debugMux.HandleFunc("/debug/pprof/trace", pprof.Trace)
+	debugMux.Handle("/metrics", promhttp.Handler())
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		// Grain pool health: simple capacity check (mirrors previous GrainHandler.IsHealthy)
+		grainCount, capacity := app.pool.LocalUsage()
+		if grainCount >= capacity {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte("grain pool at capacity"))
+			return
+		}
+		if !pool.IsHealthy() {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte("control plane not healthy"))
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("ok"))
+	})
+	mux.HandleFunc("/readyz", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("ok"))
+	})
+	mux.HandleFunc("/livez", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("ok"))
+	})
+
+	mux.HandleFunc("/version", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("1.0.0"))
+	})
+
+	mux.HandleFunc("/openapi.json", ServeEmbeddedOpenAPI)
+
+	httpAddr := normalizeListenAddr(cartPort)
+	debugAddr := normalizeListenAddr(getEnv("CART_DEBUG_PORT", "8081"))
+
+	srv := &http.Server{
+		Addr:        httpAddr,
+		BaseContext: func(net.Listener) context.Context { return ctx },
+		ReadTimeout: 10 * time.Second,
+		// Close idle keep-alive connections so a load test with many short-lived
+		// clients doesn't pin file handles open indefinitely.
+		IdleTimeout:  60 * time.Second,
+		WriteTimeout: 20 * time.Second,
+		Handler:      otelhttp.NewHandler(mux, "/"),
+	}
+
+	defer func() {
+
+		fmt.Println("Shutting down due to signal")
+		otelShutdown(context.Background())
+		diskStorage.Close()
+		pool.Close()
+
+	}()
+
+	srvErr := make(chan error, 1)
+	go func() {
+		srvErr <- srv.ListenAndServe()
+	}()
+
+	// listener := inventory.NewInventoryChangeListener(rdb, context.Background(), func(changes []inventory.InventoryChange) {
+	// 	for _, change := range changes {
+	// 		log.Printf("inventory change: %v", change)
+	// 		inventoryPubSub.Publish(change)
+	// 	}
+	// })
+
+	// go func() {
+	// 	err := listener.Start()
+	// 	if err != nil {
+	// 		log.Fatalf("Unable to start inventory listener: %v", err)
+	// 	}
+	// }()
+
+	log.Printf("Server started at %s (debug %s)", httpAddr, debugAddr)
+
+	go http.ListenAndServe(debugAddr, debugMux)
+
+	select {
+	case err = <-srvErr:
+		// Error when starting HTTP server.
+		log.Fatalf("Unable to start server: %v", err)
+	case <-ctx.Done():
+		// Wait for first CTRL+C.
+		// Stop receiving signal notifications as soon as possible.
+		stop()
+	}
+
+}

cmd/cart/openapi_embed.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"bytes"
+	"crypto/sha256"
+	_ "embed"
+	"encoding/hex"
+	"net/http"
+	"sync"
+)
+
+// openapi_embed.go: Provides embedded OpenAPI spec and helper to mount handler.
+
+//go:embed openapi.json
+var openapiJSON []byte
+
+var (
+	openapiOnce sync.Once
+	openapiETag string
+)
+
+// initOpenAPIMetadata computes immutable metadata for the embedded spec.
+func initOpenAPIMetadata() {
+	sum := sha256.Sum256(openapiJSON)
+	openapiETag = `W/"` + hex.EncodeToString(sum[:8]) + `"` // weak ETag with first 8 bytes
+}
+
+// ServeEmbeddedOpenAPI serves the embedded OpenAPI JSON spec at /openapi.json.
+// It supports GET and HEAD and implements basic ETag caching.
+func ServeEmbeddedOpenAPI(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodGet && r.Method != http.MethodHead {
+		w.Header().Set("Allow", "GET, HEAD")
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	openapiOnce.Do(initOpenAPIMetadata)
+
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	w.Header().Set("Cache-Control", "no-cache")
+	w.Header().Set("Access-Control-Allow-Origin", "*")
+	w.Header().Set("ETag", openapiETag)
+
+	if match := r.Header.Get("If-None-Match"); match != "" {
+		if bytes.Contains([]byte(match), []byte(openapiETag)) {
+			w.WriteHeader(http.StatusNotModified)
+			return
+		}
+	}
+
+	if r.Method == http.MethodHead {
+		w.WriteHeader(http.StatusOK)
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	_, _ = w.Write(openapiJSON)
+}
+
+// Optional: function to access raw spec bytes programmatically.
+func OpenAPISpecBytes() []byte {
+	return openapiJSON
+}
+
+// Optional: function to access current ETag.
+func OpenAPIETag() string {
+	openapiOnce.Do(initOpenAPIMetadata)
+	return openapiETag
+}

cmd/cart/otel.go

@@ -0,0 +1,117 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc"
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/log/global"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/log"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/trace"
+)
+
+// setupOTelSDK bootstraps the OpenTelemetry pipeline.
+// If it does not return an error, make sure to call shutdown for proper cleanup.
+func setupOTelSDK(ctx context.Context) (func(context.Context) error, error) {
+	var shutdownFuncs []func(context.Context) error
+	var err error
+
+	// shutdown calls cleanup functions registered via shutdownFuncs.
+	// The errors from the calls are joined.
+	// Each registered cleanup will be invoked once.
+	shutdown := func(ctx context.Context) error {
+		var err error
+		for _, fn := range shutdownFuncs {
+			err = errors.Join(err, fn(ctx))
+		}
+		shutdownFuncs = nil
+		return err
+	}
+
+	// handleErr calls shutdown for cleanup and makes sure that all errors are returned.
+	handleErr := func(inErr error) {
+		err = errors.Join(inErr, shutdown(ctx))
+	}
+
+	// Set up propagator.
+	prop := newPropagator()
+	otel.SetTextMapPropagator(prop)
+
+	// Set up trace provider.
+	tracerProvider, err := newTracerProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
+	otel.SetTracerProvider(tracerProvider)
+
+	// Set up meter provider.
+	meterProvider, err := newMeterProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, meterProvider.Shutdown)
+	otel.SetMeterProvider(meterProvider)
+
+	// Set up logger provider.
+	loggerProvider, err := newLoggerProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, loggerProvider.Shutdown)
+	global.SetLoggerProvider(loggerProvider)
+
+	return shutdown, err
+}
+
+func newPropagator() propagation.TextMapPropagator {
+	return propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	)
+}
+
+func newTracerProvider() (*trace.TracerProvider, error) {
+	traceExporter, err := otlptracegrpc.New(context.Background())
+	if err != nil {
+		return nil, err
+	}
+
+	tracerProvider := trace.NewTracerProvider(
+		trace.WithBatcher(traceExporter,
+			// Default is 5s. Set to 1s for demonstrative purposes.
+			trace.WithBatchTimeout(time.Second)),
+	)
+	return tracerProvider, nil
+}
+
+func newMeterProvider() (*metric.MeterProvider, error) {
+	exporter, err := otlpmetricgrpc.New(context.Background())
+	if err != nil {
+		return nil, err
+	}
+
+	provider := metric.NewMeterProvider(metric.WithReader(metric.NewPeriodicReader(exporter)))
+	return provider, nil
+}
+
+func newLoggerProvider() (*log.LoggerProvider, error) {
+	logExporter, err := otlploggrpc.New(context.Background())
+	if err != nil {
+		return nil, err
+	}
+
+	loggerProvider := log.NewLoggerProvider(
+		log.WithProcessor(log.NewBatchProcessor(logExporter)),
+	)
+	return loggerProvider, nil
+}

cmd/cart/pool-server.go

@@ -0,0 +1,675 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"log"
+	"net/http"
+	"strconv"
+	"sync"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	messages "git.k6n.net/mats/go-cart-actor/proto/cart"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/voucher"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"go.opentelemetry.io/contrib/bridges/otelslog"
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/known/anypb"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/trace"
+)
+
+var (
+	grainMutations = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_grain_mutations_total",
+		Help: "The total number of mutations",
+	})
+	grainLookups = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "cart_grain_lookups_total",
+		Help: "The total number of lookups",
+	})
+)
+
+type PoolServer struct {
+	actor.GrainPool[cart.CartGrain]
+	pod_name string
+}
+
+func NewPoolServer(pool actor.GrainPool[cart.CartGrain], pod_name string) *PoolServer {
+	srv := &PoolServer{
+		GrainPool: pool,
+		pod_name:  pod_name,
+	}
+
+	return srv
+}
+
+func (s *PoolServer) ApplyLocal(ctx context.Context, id cart.CartId, mutation ...proto.Message) (*actor.MutationResult[cart.CartGrain], error) {
+	return s.Apply(ctx, uint64(id), mutation...)
+}
+
+func (s *PoolServer) GetCartHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
+	grain, err := s.Get(r.Context(), uint64(id))
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, grain)
+}
+
+func (s *PoolServer) AddSkuToCartHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
+	sku := r.PathValue("sku")
+	msg, err := GetItemAddMessage(r.Context(), sku, 1, getCountryFromHost(r.Host), nil)
+	if err != nil {
+		return err
+	}
+
+	data, err := s.ApplyLocal(r.Context(), id, msg)
+	if err != nil {
+		return err
+	}
+	grainMutations.Add(float64(len(data.Mutations)))
+	return s.WriteResult(w, data)
+}
+
+func (s *PoolServer) WriteResult(w http.ResponseWriter, result any) error {
+	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set("Cache-Control", "no-cache")
+	w.Header().Set("Access-Control-Allow-Origin", "*")
+	w.Header().Set("X-Pod-Name", s.pod_name)
+	if result == nil {
+
+		w.WriteHeader(http.StatusInternalServerError)
+
+		return nil
+	}
+	w.WriteHeader(http.StatusOK)
+	enc := json.NewEncoder(w)
+	err := enc.Encode(result)
+	return err
+}
+
+func (s *PoolServer) DeleteItemHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
+
+	itemIdString := r.PathValue("itemId")
+	itemId, err := strconv.ParseInt(itemIdString, 10, 64)
+	if err != nil {
+		return err
+	}
+	data, err := s.ApplyLocal(r.Context(), id, &messages.RemoveItem{Id: uint32(itemId)})
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, data)
+}
+
+func (s *PoolServer) QuantityChangeHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
+	changeQuantity := messages.ChangeQuantity{}
+	err := json.NewDecoder(r.Body).Decode(&changeQuantity)
+	if err != nil {
+		return err
+	}
+	reply, err := s.ApplyLocal(r.Context(), id, &changeQuantity)
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, reply)
+}
+
+type Item struct {
+	Sku      string  `json:"sku"`
+	Quantity int     `json:"quantity"`
+	StoreId  *string `json:"storeId,omitempty"`
+	// Children are sub-articles (accessories, services, insurance, ...) priced
+	// relative to this item. They are added as separate cart lines whose
+	// ParentId points to this item's line-item id.
+	Children []Item `json:"children,omitempty"`
+	// CustomFields are optional user-supplied input fields for this line.
+	CustomFields map[string]string `json:"customFields,omitempty"`
+}
+
+type SetCartItems struct {
+	Country string `json:"country"`
+	Items   []Item `json:"items"`
+}
+
+// itemGroup is a top-level item together with its child sub-articles. The child
+// AddItem messages are built with their price already derived from the parent
+// product; their ParentId is filled in after the parent line is applied.
+type itemGroup struct {
+	parent   *messages.AddItem
+	children []*messages.AddItem
+}
+
+// buildItemGroups fetches every product and builds the AddItem messages. Groups
+// are built concurrently; within a group the parent is fetched first so it can
+// drive child pricing, then children are fetched concurrently. Input order is
+// preserved. Items that fail to fetch are skipped (logged), matching the prior
+// best-effort behavior.
+func buildItemGroups(ctx context.Context, items []Item, country string) []itemGroup {
+	groups := make([]itemGroup, len(items))
+	wg := sync.WaitGroup{}
+	for i, itm := range items {
+		wg.Go(func() {
+			parentMsg, parentProduct, err := BuildItemMessage(ctx, itm.Sku, itm.Quantity, country, itm.StoreId, nil)
+			if err != nil {
+				log.Printf("error adding item %s: %v", itm.Sku, err)
+				return
+			}
+			parentMsg.CustomFields = itm.CustomFields
+			groups[i].parent = parentMsg
+
+			if len(itm.Children) == 0 {
+				return
+			}
+			children := make([]*messages.AddItem, len(itm.Children))
+			cwg := sync.WaitGroup{}
+			for j, child := range itm.Children {
+				cwg.Go(func() {
+					childMsg, _, err := BuildItemMessage(ctx, child.Sku, child.Quantity, country, child.StoreId, parentProduct)
+					if err != nil {
+						log.Printf("error adding child %s of %s: %v", child.Sku, itm.Sku, err)
+						return
+					}
+					childMsg.CustomFields = child.CustomFields
+					children[j] = childMsg
+				})
+			}
+			cwg.Wait()
+			for _, c := range children {
+				if c != nil {
+					groups[i].children = append(groups[i].children, c)
+				}
+			}
+		})
+	}
+	wg.Wait()
+	return groups
+}
+
+// applyItemGroups applies each group in dependency order: the parent first, then
+// its children with ParentId set to the parent's resolved line-item id. Returns
+// the last mutation result for rendering.
+func (s *PoolServer) applyItemGroups(ctx context.Context, id cart.CartId, groups []itemGroup) (*actor.MutationResult[cart.CartGrain], error) {
+	var last *actor.MutationResult[cart.CartGrain]
+	for _, g := range groups {
+		if g.parent == nil {
+			continue
+		}
+		res, err := s.ApplyLocal(ctx, id, g.parent)
+		if err != nil {
+			return nil, err
+		}
+		last = res
+
+		if len(g.children) == 0 {
+			continue
+		}
+		parentLineId, ok := parentLineId(&res.Result, g.parent)
+		if !ok {
+			log.Printf("could not resolve parent line for item %d (sku %s); skipping %d children",
+				g.parent.ItemId, g.parent.Sku, len(g.children))
+			continue
+		}
+		childMsgs := make([]proto.Message, len(g.children))
+		for i, c := range g.children {
+			c.ParentId = &parentLineId
+			childMsgs[i] = c
+		}
+		res, err = s.ApplyLocal(ctx, id, childMsgs...)
+		if err != nil {
+			return nil, err
+		}
+		last = res
+	}
+	return last, nil
+}
+
+// parentLineId finds the line-item id of the just-applied parent: the resident
+// item with the parent's catalog ItemId, matching store, and no parent of its
+// own. AddItem merges by sku+store, so at most one such line exists.
+func parentLineId(grain *cart.CartGrain, parent *messages.AddItem) (uint32, bool) {
+	for _, it := range grain.Items {
+		if it == nil || it.ParentId != nil {
+			continue
+		}
+		if it.ItemId != parent.ItemId {
+			continue
+		}
+		sameStore := (it.StoreId == nil && parent.StoreId == nil) ||
+			(it.StoreId != nil && parent.StoreId != nil && *it.StoreId == *parent.StoreId)
+		if sameStore {
+			return it.Id, true
+		}
+	}
+	return 0, false
+}
+
+func (s *PoolServer) SetCartItemsHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
+	setCartItems := SetCartItems{}
+	err := json.NewDecoder(r.Body).Decode(&setCartItems)
+	if err != nil {
+		return err
+	}
+
+	if _, err := s.ApplyLocal(r.Context(), id, &messages.ClearCartRequest{}); err != nil {
+		return err
+	}
+	groups := buildItemGroups(r.Context(), setCartItems.Items, setCartItems.Country)
+	reply, err := s.applyItemGroups(r.Context(), id, groups)
+	if err != nil {
+		return err
+	}
+	if reply == nil {
+		// Cart was cleared but nothing added; return current (empty) state.
+		grain, err := s.Get(r.Context(), uint64(id))
+		if err != nil {
+			return err
+		}
+		return s.WriteResult(w, grain)
+	}
+	return s.WriteResult(w, reply)
+}
+
+func (s *PoolServer) AddMultipleItemHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
+	setCartItems := SetCartItems{}
+	err := json.NewDecoder(r.Body).Decode(&setCartItems)
+	if err != nil {
+		return err
+	}
+
+	groups := buildItemGroups(r.Context(), setCartItems.Items, setCartItems.Country)
+	reply, err := s.applyItemGroups(r.Context(), id, groups)
+	if err != nil {
+		return err
+	}
+	if reply == nil {
+		grain, err := s.Get(r.Context(), uint64(id))
+		if err != nil {
+			return err
+		}
+		return s.WriteResult(w, grain)
+	}
+	return s.WriteResult(w, reply)
+}
+
+type AddRequest struct {
+	Sku      string  `json:"sku"`
+	Quantity int32   `json:"quantity"`
+	Country  string  `json:"country"`
+	StoreId  *string `json:"storeId"`
+	// Children are sub-articles priced relative to this item (see Item.Children).
+	Children []Item `json:"children,omitempty"`
+	// CustomFields are optional user-supplied input fields for this line.
+	CustomFields map[string]string `json:"customFields,omitempty"`
+}
+
+func (s *PoolServer) AddSkuRequestHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
+	addRequest := AddRequest{Quantity: 1}
+	err := json.NewDecoder(r.Body).Decode(&addRequest)
+	if err != nil {
+		return err
+	}
+
+	item := Item{
+		Sku:          addRequest.Sku,
+		Quantity:     int(addRequest.Quantity),
+		StoreId:      addRequest.StoreId,
+		Children:     addRequest.Children,
+		CustomFields: addRequest.CustomFields,
+	}
+	groups := buildItemGroups(r.Context(), []Item{item}, addRequest.Country)
+	reply, err := s.applyItemGroups(r.Context(), id, groups)
+	if err != nil {
+		return err
+	}
+	if reply == nil {
+		grain, err := s.Get(r.Context(), uint64(id))
+		if err != nil {
+			return err
+		}
+		return s.WriteResult(w, grain)
+	}
+	return s.WriteResult(w, reply)
+}
+
+// func (s *PoolServer) HandleConfirmation(w http.ResponseWriter, r *http.Request, id CartId) error {
+// 	orderId := r.PathValue("orderId")
+// 	if orderId == "" {
+// 		return fmt.Errorf("orderId is empty")
+// 	}
+// 	order, err := KlarnaInstance.GetOrder(orderId)
+
+// 	if err != nil {
+// 		return err
+// 	}
+
+// 	w.Header().Set("Content-Type", "application/json")
+// 	w.Header().Set("X-Pod-Name", s.pod_name)
+// 	w.Header().Set("Cache-Control", "no-cache")
+// 	w.Header().Set("Access-Control-Allow-Origin", "*")
+// 	w.WriteHeader(http.StatusOK)
+// 	return json.NewEncoder(w).Encode(order)
+// }
+
+// func (s *PoolServer) HandleCheckout(w http.ResponseWriter, r *http.Request, id CartId) error {
+// 	klarnaOrder, err := s.CreateOrUpdateCheckout(r.Host, id)
+// 	if err != nil {
+// 		return err
+// 	}
+
+// 	s.ApplyCheckoutStarted(klarnaOrder, id)
+
+// 	w.Header().Set("Content-Type", "application/json")
+// 	return json.NewEncoder(w).Encode(klarnaOrder)
+// }
+//
+
+// Removed leftover legacy block after CookieCartIdHandler (obsolete code referencing cid/legacy)
+
+func (s *PoolServer) RemoveCartCookie(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
+	// Clear cart cookie (breaking change: do not issue a new legacy id here)
+	http.SetCookie(w, &http.Cookie{
+		Name:     "cartid",
+		Value:    "",
+		Path:     "/",
+		Secure:   r.TLS != nil,
+		HttpOnly: true,
+		Expires:  time.Unix(0, 0),
+		SameSite: http.SameSiteLaxMode,
+	})
+	w.WriteHeader(http.StatusOK)
+	return nil
+}
+
+func (s *PoolServer) ProxyHandler(fn func(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error) func(cartId cart.CartId, w http.ResponseWriter, r *http.Request) error {
+	return func(cartId cart.CartId, w http.ResponseWriter, r *http.Request) error {
+		if ownerHost, ok := s.OwnerHost(uint64(cartId)); ok {
+			ctx, span := tracer.Start(r.Context(), "proxy")
+			defer span.End()
+			span.SetAttributes(attribute.String("cartid", cartId.String()))
+			hostAttr := attribute.String("other host", ownerHost.Name())
+			span.SetAttributes(hostAttr)
+			logger.InfoContext(ctx, "cart proxyed", "result", ownerHost.Name())
+			proxyCalls.Add(ctx, 1, metric.WithAttributes(hostAttr))
+			handled, err := ownerHost.Proxy(uint64(cartId), w, r, nil)
+
+			grainLookups.Inc()
+			if err == nil && handled {
+				return nil
+			}
+		}
+		_, span := tracer.Start(r.Context(), "own")
+		span.SetAttributes(attribute.String("cartid", cartId.String()))
+		defer span.End()
+		return fn(w, r, cartId)
+
+	}
+}
+
+var (
+	tracer     = otel.Tracer(name)
+	meter      = otel.Meter(name)
+	logger     = otelslog.NewLogger(name)
+	proxyCalls metric.Int64Counter
+)
+
+func init() {
+	var err error
+	proxyCalls, err = meter.Int64Counter("proxy.calls",
+		metric.WithDescription("Number of proxy calls"),
+		metric.WithUnit("{calls}"))
+	if err != nil {
+		panic(err)
+	}
+
+}
+
+type AddVoucherRequest struct {
+	VoucherCode string `json:"code"`
+}
+
+func (s *PoolServer) AddVoucherHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
+	data := &AddVoucherRequest{}
+	json.NewDecoder(r.Body).Decode(data)
+	v := voucher.Service{}
+	msg, err := v.GetVoucher(data.VoucherCode)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte(err.Error()))
+		return err
+	}
+	reply, err := s.ApplyLocal(r.Context(), cartId, msg)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte(err.Error()))
+		return err
+	}
+	s.WriteResult(w, reply)
+	return nil
+}
+
+type SubscriptionDetailsRequest struct {
+	Id           *string         `json:"id,omitempty"`
+	OfferingCode string          `json:"offeringCode,omitempty"`
+	SigningType  string          `json:"signingType,omitempty"`
+	Data         json.RawMessage `json:"data,omitempty"`
+}
+
+func (sd *SubscriptionDetailsRequest) ToMessage() *messages.UpsertSubscriptionDetails {
+	return &messages.UpsertSubscriptionDetails{
+		Id:           sd.Id,
+		OfferingCode: sd.OfferingCode,
+		SigningType:  sd.SigningType,
+		Data:         &anypb.Any{Value: sd.Data},
+	}
+}
+
+func (s *PoolServer) SubscriptionDetailsHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
+	data := &SubscriptionDetailsRequest{}
+	err := json.NewDecoder(r.Body).Decode(data)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte(err.Error()))
+		return err
+	}
+	reply, err := s.ApplyLocal(r.Context(), cartId, data.ToMessage())
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte(err.Error()))
+		return err
+	}
+	s.WriteResult(w, reply)
+	return nil
+}
+
+func (s *PoolServer) RemoveVoucherHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
+
+	idStr := r.PathValue("voucherId")
+	id, err := strconv.ParseInt(idStr, 10, 64)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte(err.Error()))
+		return err
+	}
+	reply, err := s.ApplyLocal(r.Context(), cartId, &messages.RemoveVoucher{Id: uint32(id)})
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte(err.Error()))
+		return err
+	}
+	s.WriteResult(w, reply)
+	return nil
+}
+
+func (s *PoolServer) SetUserIdHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
+	setUserId := messages.SetUserId{}
+	err := json.NewDecoder(r.Body).Decode(&setUserId)
+	if err != nil {
+		return err
+	}
+	reply, err := s.ApplyLocal(r.Context(), cartId, &setUserId)
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, reply)
+}
+
+func (s *PoolServer) LineItemMarkingHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
+	itemIdStr := r.PathValue("itemId")
+	itemId, err := strconv.ParseInt(itemIdStr, 10, 64)
+	if err != nil {
+		return err
+	}
+	lineItemMarking := messages.LineItemMarking{Id: uint32(itemId)}
+	err = json.NewDecoder(r.Body).Decode(&lineItemMarking)
+	if err != nil {
+		return err
+	}
+	reply, err := s.ApplyLocal(r.Context(), cartId, &lineItemMarking)
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, reply)
+}
+
+func (s *PoolServer) RemoveLineItemMarkingHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
+	itemIdStr := r.PathValue("itemId")
+	itemId, err := strconv.ParseInt(itemIdStr, 10, 64)
+	if err != nil {
+		return err
+	}
+	removeLineItemMarking := messages.RemoveLineItemMarking{Id: uint32(itemId)}
+	reply, err := s.ApplyLocal(r.Context(), cartId, &removeLineItemMarking)
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, reply)
+}
+
+type SetCustomFieldsRequest struct {
+	CustomFields map[string]string `json:"customFields"`
+}
+
+func (s *PoolServer) SetCustomFieldsHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
+	itemId, err := strconv.ParseInt(r.PathValue("itemId"), 10, 64)
+	if err != nil {
+		return err
+	}
+	req := SetCustomFieldsRequest{}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		return err
+	}
+	reply, err := s.ApplyLocal(r.Context(), cartId, &messages.SetLineItemCustomFields{
+		Id:           uint32(itemId),
+		CustomFields: req.CustomFields,
+	})
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, reply)
+}
+
+func (s *PoolServer) InternalApplyMutationHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
+	if r.Method != http.MethodPost {
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		return nil
+	}
+	data, err := io.ReadAll(r.Body)
+	if err != nil {
+		return err
+	}
+	mutation := &messages.Mutation{}
+	err = proto.Unmarshal(data, mutation)
+	if err != nil {
+		return err
+	}
+	reply, err := s.ApplyLocal(r.Context(), cartId, mutation)
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, reply)
+}
+
+func (s *PoolServer) GetAnywhere(ctx context.Context, cartId cart.CartId) (*cart.CartGrain, error) {
+	id := uint64(cartId)
+	if host, isOnOtherHost := s.OwnerHost(id); isOnOtherHost {
+		return host.Get(ctx, id)
+	}
+	return s.Get(ctx, id)
+}
+
+func (s *PoolServer) ApplyAnywhere(ctx context.Context, cartId cart.CartId, msgs ...proto.Message) error {
+	id := uint64(cartId)
+	if host, isOnOtherHost := s.OwnerHost(id); isOnOtherHost {
+		_, err := host.Apply(ctx, id, msgs...)
+		return err
+	}
+	_, err := s.Apply(ctx, id, msgs...)
+	return err
+}
+
+func (s *PoolServer) Serve(mux *http.ServeMux) {
+
+	// mux.HandleFunc("OPTIONS /cart", func(w http.ResponseWriter, r *http.Request) {
+	// 	w.Header().Set("Access-Control-Allow-Origin", "*")
+	// 	w.Header().Set("Access-Control-Allow-Methods", "GET, PUT, POST, DELETE")
+	// 	w.Header().Set("Access-Control-Allow-Headers", "Content-Type")
+	// 	w.WriteHeader(http.StatusOK)
+	// })
+
+	handleFunc := func(pattern string, handlerFunc func(http.ResponseWriter, *http.Request)) {
+		attr := attribute.String("http.route", pattern)
+		mux.HandleFunc(pattern, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			span := trace.SpanFromContext(r.Context())
+			span.SetName(pattern)
+			span.SetAttributes(attr)
+
+			labeler, _ := otelhttp.LabelerFromContext(r.Context())
+			labeler.Add(attr)
+
+			handlerFunc(w, r)
+		}))
+	}
+
+	handleFunc("GET /cart", CookieCartIdHandler(s.ProxyHandler(s.GetCartHandler)))
+	handleFunc("GET /cart/add/{sku}", CookieCartIdHandler(s.ProxyHandler(s.AddSkuToCartHandler)))
+	handleFunc("POST /cart/add", CookieCartIdHandler(s.ProxyHandler(s.AddMultipleItemHandler)))
+	handleFunc("POST /cart", CookieCartIdHandler(s.ProxyHandler(s.AddSkuRequestHandler)))
+	handleFunc("POST /cart/set", CookieCartIdHandler(s.ProxyHandler(s.SetCartItemsHandler)))
+	handleFunc("DELETE /cart/{itemId}", CookieCartIdHandler(s.ProxyHandler(s.DeleteItemHandler)))
+	handleFunc("PUT /cart", CookieCartIdHandler(s.ProxyHandler(s.QuantityChangeHandler)))
+	handleFunc("DELETE /cart", CookieCartIdHandler(s.ProxyHandler(s.RemoveCartCookie)))
+	handleFunc("PUT /cart/voucher", CookieCartIdHandler(s.ProxyHandler(s.AddVoucherHandler)))
+	handleFunc("PUT /cart/subscription-details", CookieCartIdHandler(s.ProxyHandler(s.SubscriptionDetailsHandler)))
+	handleFunc("DELETE /cart/voucher/{voucherId}", CookieCartIdHandler(s.ProxyHandler(s.RemoveVoucherHandler)))
+	handleFunc("PUT /cart/user", CookieCartIdHandler(s.ProxyHandler(s.SetUserIdHandler)))
+
+	handleFunc("PUT /cart/item/{itemId}/marking", CookieCartIdHandler(s.ProxyHandler(s.LineItemMarkingHandler)))
+	handleFunc("DELETE /cart/item/{itemId}/marking", CookieCartIdHandler(s.ProxyHandler(s.RemoveLineItemMarkingHandler)))
+	handleFunc("PUT /cart/item/{itemId}/custom-fields", CookieCartIdHandler(s.ProxyHandler(s.SetCustomFieldsHandler)))
+
+	//mux.HandleFunc("GET /cart/checkout", CookieCartIdHandler(s.ProxyHandler(s.HandleCheckout)))
+	//mux.HandleFunc("GET /cart/confirmation/{orderId}", CookieCartIdHandler(s.ProxyHandler(s.HandleConfirmation)))
+
+	handleFunc("GET /cart/byid/{id}", CartIdHandler(s.ProxyHandler(s.GetCartHandler)))
+
+	handleFunc("POST /cart/byid/{id}", CartIdHandler(s.ProxyHandler(s.AddSkuRequestHandler)))
+	handleFunc("DELETE /cart/byid/{id}/{itemId}", CartIdHandler(s.ProxyHandler(s.DeleteItemHandler)))
+	handleFunc("PUT /cart/byid/{id}", CartIdHandler(s.ProxyHandler(s.QuantityChangeHandler)))
+	handleFunc("PUT /cart/byid/{id}/voucher", CookieCartIdHandler(s.ProxyHandler(s.AddVoucherHandler)))
+	handleFunc("DELETE /cart/byid/{id}/voucher/{voucherId}", CookieCartIdHandler(s.ProxyHandler(s.RemoveVoucherHandler)))
+	handleFunc("PUT /cart/byid/{id}/user", CartIdHandler(s.ProxyHandler(s.SetUserIdHandler)))
+	handleFunc("PUT /cart/byid/{id}/item/{itemId}/marking", CartIdHandler(s.ProxyHandler(s.LineItemMarkingHandler)))
+	handleFunc("DELETE /cart/byid/{id}/item/{itemId}/marking", CartIdHandler(s.ProxyHandler(s.RemoveLineItemMarkingHandler)))
+	handleFunc("PUT /cart/byid/{id}/item/{itemId}/custom-fields", CartIdHandler(s.ProxyHandler(s.SetCustomFieldsHandler)))
+}

cmd/cart/product-fetcher.go

@@ -0,0 +1,219 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"math"
+	"net/http"
+	"strconv"
+
+	messages "git.k6n.net/mats/go-cart-actor/proto/cart"
+)
+
+// consumedKeys are product-document keys that are mapped to typed AddItem
+// fields. They are stripped from the dynamic remainder so Extra only holds
+// genuinely dynamic data.
+var consumedKeys = []string{
+	"id", "sku", "title", "img", "price", "vat",
+	"discount", "inStock", "supplierId", "supplierName", "deleted",
+}
+
+// getBaseUrl returns the product service base url. Overridable via
+// PRODUCT_BASE_URL (the country argument is currently unused but kept for when
+// per-market routing returns).
+func getBaseUrl(country string) string {
+	return getEnv("PRODUCT_BASE_URL", "http://localhost:8082")
+}
+
+// ProductItem is the flat product document served by GET /api/get/{sku}.
+// Only the fields the cart currently maps mechanically are decoded; the rest
+// of the (dynamic) document is intentionally ignored until the cart item model
+// is reworked to carry arbitrary data.
+type ProductItem struct {
+	Id           uint64  `json:"id"`
+	Sku          string  `json:"sku"`
+	Title        string  `json:"title"`
+	Img          string  `json:"img"`
+	Price        float64 `json:"price"`
+	Vat          int     `json:"vat"`
+	Discount     int     `json:"discount"` // percent off the original price
+	InStock      int32   `json:"inStock"`
+	SupplierId   int     `json:"supplierId"`
+	SupplierName string  `json:"supplierName"`
+	Deleted      bool    `json:"deleted"`
+
+	// Extra is the rest of the product document (everything not mapped to a
+	// typed field above), preserved verbatim and surfaced on the cart item.
+	Extra map[string]json.RawMessage `json:"-"`
+}
+
+// numberField reads a numeric dynamic property from the product document
+// (width, height, ...). Like JS Number(), it accepts a JSON number or a numeric
+// string. Returns false when the key is absent or not numeric.
+func (p *ProductItem) numberField(key string) (float64, bool) {
+	raw, ok := p.Extra[key]
+	if !ok {
+		return 0, false
+	}
+	var f float64
+	if err := json.Unmarshal(raw, &f); err == nil {
+		return f, true
+	}
+	var s string
+	if err := json.Unmarshal(raw, &s); err == nil {
+		if f, err := strconv.ParseFloat(s, 64); err == nil {
+			return f, true
+		}
+	}
+	return 0, false
+}
+
+func FetchItem(ctx context.Context, sku string, country string) (*ProductItem, error) {
+	baseUrl := getBaseUrl(country)
+	innerCtx, span := tracer.Start(ctx, fmt.Sprintf("fetching data for %s", sku))
+	defer span.End()
+	req, err := http.NewRequestWithContext(innerCtx, http.MethodGet, fmt.Sprintf("%s/api/get/%s", baseUrl, sku), nil)
+	if err != nil {
+		return nil, err
+	}
+	res, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("product service returned %d for sku %s", res.StatusCode, sku)
+	}
+	body, err := io.ReadAll(res.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	var item ProductItem
+	if err := json.Unmarshal(body, &item); err != nil {
+		return nil, err
+	}
+
+	// Capture everything not mapped to a typed field as dynamic data.
+	all := map[string]json.RawMessage{}
+	if err := json.Unmarshal(body, &all); err != nil {
+		return nil, err
+	}
+	for _, k := range consumedKeys {
+		delete(all, k)
+	}
+	if len(all) > 0 {
+		item.Extra = all
+	}
+
+	return &item, nil
+}
+
+func GetItemAddMessage(ctx context.Context, sku string, qty int, country string, storeId *string) (*messages.AddItem, error) {
+	msg, _, err := BuildItemMessage(ctx, sku, qty, country, storeId, nil)
+	return msg, err
+}
+
+// BuildItemMessage fetches a product and builds its AddItem mutation, returning
+// the fetched product too so it can serve as the parent for child items. When
+// parent is non-nil the line is priced as a child of that parent.
+func BuildItemMessage(ctx context.Context, sku string, qty int, country string, storeId *string, parent *ProductItem) (*messages.AddItem, *ProductItem, error) {
+	item, err := FetchItem(ctx, sku, country)
+	if err != nil {
+		return nil, nil, err
+	}
+	msg, err := ToItemAddMessage(item, parent, storeId, qty, country)
+	if err != nil {
+		return nil, nil, err
+	}
+	return msg, item, nil
+}
+
+// Glass is billed at a minimum surface even when the real pane is smaller, so a
+// small window doesn't get a near-zero per-m² price.
+const minGlassArea = 0.4 // m²
+
+// areaFromItem derives the main article's *visible glass* surface in m² from a
+// resolved configurator selection. The catalog width/height are facet codes;
+// the outer (karmytter) size is `code × 100 − margin` mm and the visible glass
+// is that minus the frame border per axis, e.g. width 4, widthMargin 20,
+// borderWidth 194 → 400 − 20 − 194 = 186 mm. Area = glassW(mm) × glassH(mm) /
+// 1e6, clamped up to the minGlassArea billing floor. Returns 0 when a dimension
+// is missing/non-numeric (non-window PDP, or no product resolved yet).
+func areaFromItem(item *ProductItem) float64 {
+	if item == nil {
+		return 0
+	}
+	w, okW := item.numberField("width")
+	h, okH := item.numberField("height")
+	if !okW || !okH || w <= 0 || h <= 0 {
+		return 0
+	}
+	glassW := w * 100 // - (item.numberField("widthMargin") + item.numberField("borderWidth"))
+	glassH := h * 100 // - (item.numberField("heightMargin") + item.numberField("borderHeight"))
+	if glassW <= 0 || glassH <= 0 {
+		return 0
+	}
+	return math.Max((glassW*glassH)/1_000_000, minGlassArea)
+}
+
+// accessoryPrice computes a child line's unit price (inc vat, minor units): the
+// child's own per-m² price scaled by the parent window's billed glass area.
+// When the parent has no usable dimensions the area is 0, so the price is 0.
+func accessoryPrice(parent *ProductItem, child *ProductItem) int64 {
+	area := areaFromItem(parent)
+	return int64(child.Price*100*area + 0.5)
+}
+
+// orgPriceFromDiscount reconstructs the pre-discount price from a percentage.
+// Returns 0 when there is no usable discount, in which case OrgPrice is omitted.
+func orgPriceFromDiscount(price int64, discountPercent int) int64 {
+	if discountPercent <= 0 || discountPercent >= 100 {
+		return 0
+	}
+	return int64(float64(price)/(1-float64(discountPercent)/100) + 0.5)
+}
+
+func ToItemAddMessage(item *ProductItem, parent *ProductItem, storeId *string, qty int, country string) (*messages.AddItem, error) {
+	// Central stock only: store-specific stock is no longer in the payload, so a
+	// storeId request currently resolves to zero stock.
+	var stock int32
+	if storeId == nil {
+		stock = item.InStock
+	}
+
+	// Top-level items price from their own product; children are priced from the
+	// parent product via the accessory-price hook.
+	price := int64(item.Price)
+	if parent != nil {
+		price = accessoryPrice(parent, item)
+	}
+
+	msg := &messages.AddItem{
+		ItemId:     uint32(item.Id),
+		Quantity:   int32(qty),
+		Price:      price,
+		OrgPrice:   orgPriceFromDiscount(price, item.Discount),
+		Sku:        item.Sku,
+		Name:       item.Title,
+		Image:      item.Img,
+		Stock:      stock,
+		Tax:        int32(item.Vat * 100),
+		SellerId:   strconv.Itoa(item.SupplierId),
+		SellerName: item.SupplierName,
+		Country:    country,
+		StoreId:    storeId,
+	}
+
+	if len(item.Extra) > 0 {
+		extra, err := json.Marshal(item.Extra)
+		if err != nil {
+			return nil, fmt.Errorf("marshal extra product data: %w", err)
+		}
+		msg.ExtraJson = extra
+	}
+
+	return msg, nil
+}

cmd/cart/product-fetcher_integration_test.go

@@ -0,0 +1,390 @@
+//go:build integration
+
+// Integration tests for the product fetcher. These hit a live product service
+// and are excluded from the default build/test run. Run them with:
+//
+//	go test -tags=integration ./cmd/cart/
+//
+// Point at a different service with PRODUCT_BASE_URL (default http://localhost:8082).
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"testing"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	"git.k6n.net/mats/go-cart-actor/pkg/proxy"
+)
+
+// newTestPoolServer builds a real, disk-backed PoolServer for exercising the
+// HTTP handlers end-to-end (no clustering peers).
+func newTestPoolServer(t *testing.T) *PoolServer {
+	t.Helper()
+	reg := cart.NewCartMultationRegistry(cart.NewCartMutationContext(nil))
+	reg.RegisterProcessor(actor.NewMutationProcessor(func(_ context.Context, g *cart.CartGrain) error {
+		g.UpdateTotals()
+		g.Version++
+		return nil
+	}))
+	dir := t.TempDir()
+	disk := actor.NewDiskStorage[cart.CartGrain](dir, reg)
+	pool, err := actor.NewSimpleGrainPool(actor.GrainPoolConfig[cart.CartGrain]{
+		MutationRegistry: reg,
+		Storage:          disk,
+		Spawn: func(ctx context.Context, id uint64) (actor.Grain[cart.CartGrain], error) {
+			g := cart.NewCartGrain(id, time.Now())
+			err := disk.LoadEvents(ctx, id, g)
+			return g, err
+		},
+		Destroy: func(actor.Grain[cart.CartGrain]) error { return nil },
+		SpawnHost: func(host string) (actor.Host[cart.CartGrain], error) {
+			return proxy.NewRemoteHost[cart.CartGrain](host, "8080")
+		},
+		TTL:      5 * time.Minute,
+		PoolSize: 1000,
+		Hostname: "",
+	})
+	if err != nil {
+		t.Fatalf("new pool: %v", err)
+	}
+	return NewPoolServer(pool, "test")
+}
+
+// exampleId is the catalog item the fetcher rework was validated against.
+const exampleId = "8163"
+
+// requireService skips the test when the product service is not reachable so
+// the suite degrades gracefully in environments without it.
+func requireService(t *testing.T) {
+	t.Helper()
+	base := getBaseUrl("se")
+	req, err := http.NewRequest(http.MethodGet, base+"/api/get/"+exampleId, nil)
+	if err != nil {
+		t.Fatalf("build probe request: %v", err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	res, err := http.DefaultClient.Do(req.WithContext(ctx))
+	if err != nil {
+		var netErr net.Error
+		if errors.As(err, &netErr) || errors.Is(err, context.DeadlineExceeded) {
+			t.Skipf("product service %s not reachable: %v", base, err)
+		}
+		t.Fatalf("probe product service: %v", err)
+	}
+	res.Body.Close()
+}
+
+func TestFetchItem_Example8163(t *testing.T) {
+	requireService(t)
+
+	ctx := context.Background()
+	item, err := FetchItem(ctx, exampleId, "se")
+	if err != nil {
+		t.Fatalf("FetchItem(%s): %v", exampleId, err)
+	}
+
+	if item.Id != 8163 {
+		t.Errorf("Id = %d, want 8163", item.Id)
+	}
+	if item.Sku == "" {
+		t.Error("Sku is empty")
+	}
+	if item.Price <= 0 {
+		t.Errorf("Price = %v, want > 0", item.Price)
+	}
+	t.Logf("fetched %d sku=%s price=%v vat=%d discount=%d inStock=%d supplier=%q",
+		item.Id, item.Sku, item.Price, item.Vat, item.Discount, item.InStock, item.SupplierName)
+}
+
+func TestToItemAddMessage_Example8163(t *testing.T) {
+	requireService(t)
+
+	ctx := context.Background()
+	item, err := FetchItem(ctx, exampleId, "se")
+	if err != nil {
+		t.Fatalf("FetchItem(%s): %v", exampleId, err)
+	}
+
+	// Central stock (no storeId, no parent).
+	msg, err := ToItemAddMessage(item, nil, nil, 2, "se")
+	if err != nil {
+		t.Fatalf("ToItemAddMessage: %v", err)
+	}
+
+	if msg.ItemId != uint32(item.Id) {
+		t.Errorf("ItemId = %d, want %d", msg.ItemId, item.Id)
+	}
+	if msg.Quantity != 2 {
+		t.Errorf("Quantity = %d, want 2", msg.Quantity)
+	}
+	if want := int64(item.Price * 100); msg.Price != want {
+		t.Errorf("Price = %d, want %d (price*100)", msg.Price, want)
+	}
+	if msg.Sku != item.Sku {
+		t.Errorf("Sku = %q, want %q", msg.Sku, item.Sku)
+	}
+	if msg.Name == "" {
+		t.Error("Name is empty")
+	}
+	if want := int32(item.Vat * 100); msg.Tax != want {
+		t.Errorf("Tax = %d, want vat*100 = %d", msg.Tax, want)
+	}
+	if msg.Stock != item.InStock {
+		t.Errorf("Stock = %d, want central inStock %d", msg.Stock, item.InStock)
+	}
+	if msg.SellerName != item.SupplierName {
+		t.Errorf("SellerName = %q, want %q", msg.SellerName, item.SupplierName)
+	}
+	if want := strconv.Itoa(item.SupplierId); msg.SellerId != want {
+		t.Errorf("SellerId = %q, want %q", msg.SellerId, want)
+	}
+
+	// OrgPrice is reconstructed from the discount percent.
+	if item.Discount > 0 && item.Discount < 100 {
+		if msg.OrgPrice <= msg.Price {
+			t.Errorf("OrgPrice = %d, want > Price %d (discount %d%%)", msg.OrgPrice, msg.Price, item.Discount)
+		}
+	} else if msg.OrgPrice != 0 {
+		t.Errorf("OrgPrice = %d, want 0 (no usable discount)", msg.OrgPrice)
+	}
+
+	// Store stock currently resolves to zero (store-level stock not in payload).
+	storeId := "1234"
+	storeMsg, err := ToItemAddMessage(item, nil, &storeId, 1, "se")
+	if err != nil {
+		t.Fatalf("ToItemAddMessage(store): %v", err)
+	}
+	if storeMsg.Stock != 0 {
+		t.Errorf("store Stock = %d, want 0", storeMsg.Stock)
+	}
+	if storeMsg.StoreId == nil || *storeMsg.StoreId != storeId {
+		t.Errorf("StoreId = %v, want %q", storeMsg.StoreId, storeId)
+	}
+
+	if len(msg.ExtraJson) == 0 {
+		t.Error("expected ExtraJson to carry dynamic product data")
+	}
+}
+
+// TestDynamicData_RoundTripsToCartItem exercises the full path: fetch the
+// product, build the AddItem mutation, apply it through the cart mutation
+// registry, then render the cart exactly as the API does — asserting that a
+// dynamic product key ("glas" for item 8163) is flattened onto the item.
+func TestDynamicData_RoundTripsToCartItem(t *testing.T) {
+	requireService(t)
+
+	ctx := context.Background()
+	msg, err := GetItemAddMessage(ctx, exampleId, 1, "se", nil)
+	if err != nil {
+		t.Fatalf("GetItemAddMessage: %v", err)
+	}
+
+	reg := cart.NewCartMultationRegistry(cart.NewCartMutationContext(nil))
+	grain := cart.NewCartGrain(1, time.Now())
+	if _, err := reg.Apply(ctx, grain, msg); err != nil {
+		t.Fatalf("apply AddItem: %v", err)
+	}
+
+	// Marshal the grain the way the HTTP handlers do (WriteResult -> json).
+	b, err := json.Marshal(grain)
+	if err != nil {
+		t.Fatalf("marshal grain: %v", err)
+	}
+
+	var rendered struct {
+		Items []map[string]json.RawMessage `json:"items"`
+	}
+	if err := json.Unmarshal(b, &rendered); err != nil {
+		t.Fatalf("unmarshal grain: %v", err)
+	}
+	if len(rendered.Items) != 1 {
+		t.Fatalf("items = %d, want 1", len(rendered.Items))
+	}
+
+	item := rendered.Items[0]
+	// Typed field present.
+	if _, ok := item["sku"]; !ok {
+		t.Error("rendered item missing typed key \"sku\"")
+	}
+	// Dynamic key flattened onto the item and returned over the API.
+	glas, ok := item["glas"]
+	if !ok {
+		t.Fatalf("rendered item missing dynamic key \"glas\"; got keys %v", keysOf(item))
+	}
+	if string(glas) != `"V"` {
+		t.Errorf("glas = %s, want \"V\"", glas)
+	}
+}
+
+// TestSetCartItems_ParentWithChildren reproduces the reported scenario through
+// the real SetCartItemsHandler: a parent SKU with three distinct children.
+func TestSetCartItems_ParentWithChildren(t *testing.T) {
+	requireService(t)
+
+	s := newTestPoolServer(t)
+	body := `{"sku":"146620","quantity":1,"children":[{"sku":"170852","quantity":1},{"sku":"123075","quantity":1},{"sku":"123076","quantity":1}]}`
+	// The handler decodes SetCartItems{country, items:[Item]} — the reported
+	// payload is a single Item, so wrap it in the items array.
+	payload := `{"country":"se","items":[` + body + `]}`
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodPost, "/cart/set", bytes.NewBufferString(payload))
+	if err := s.SetCartItemsHandler(rec, req, cart.CartId(42)); err != nil {
+		t.Fatalf("SetCartItemsHandler: %v", err)
+	}
+
+	type lineT struct {
+		Id       uint32  `json:"id"`
+		ItemId   uint32  `json:"itemId"`
+		ParentId *uint32 `json:"parentId"`
+		Sku      string  `json:"sku"`
+	}
+	// Handler returns a MutationResult {result:{items}, mutations}. Fall back to
+	// top-level items for the empty-cart path.
+	var resp struct {
+		Result struct {
+			Items []lineT `json:"items"`
+		} `json:"result"`
+		Items []lineT `json:"items"`
+	}
+	if err := json.Unmarshal(rec.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("decode response: %v\nbody: %s", err, rec.Body.String())
+	}
+	grain := struct{ Items []lineT }{Items: resp.Result.Items}
+	if len(grain.Items) == 0 {
+		grain.Items = resp.Items
+	}
+
+	t.Logf("result has %d items:", len(grain.Items))
+	for _, it := range grain.Items {
+		t.Logf("  line %d itemId=%d sku=%s parentId=%v", it.Id, it.ItemId, it.Sku, it.ParentId)
+	}
+	if len(grain.Items) != 4 {
+		t.Fatalf("items = %d, want 4 (parent + 3 children)", len(grain.Items))
+	}
+	children := 0
+	for _, it := range grain.Items {
+		if it.ParentId != nil {
+			children++
+		}
+	}
+	if children != 3 {
+		t.Errorf("children = %d, want 3", children)
+	}
+}
+
+// TestAddSkuRequest_SingleItemWithChildren posts the bare single-item body (no
+// items wrapper) to the single-add handler and asserts children are added.
+func TestAddSkuRequest_SingleItemWithChildren(t *testing.T) {
+	requireService(t)
+
+	s := newTestPoolServer(t)
+	payload := `{"sku":"146620","quantity":1,"country":"se","children":[{"sku":"170852","quantity":1},{"sku":"123075","quantity":1},{"sku":"123076","quantity":1}]}`
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodPost, "/cart", bytes.NewBufferString(payload))
+	if err := s.AddSkuRequestHandler(rec, req, cart.CartId(7)); err != nil {
+		t.Fatalf("AddSkuRequestHandler: %v", err)
+	}
+
+	var resp struct {
+		Result struct {
+			Items []struct {
+				ParentId *uint32 `json:"parentId"`
+			} `json:"items"`
+		} `json:"result"`
+	}
+	if err := json.Unmarshal(rec.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("decode: %v\nbody: %s", err, rec.Body.String())
+	}
+	if len(resp.Result.Items) != 4 {
+		t.Fatalf("items = %d, want 4 (parent + 3 children)", len(resp.Result.Items))
+	}
+}
+
+func keysOf(m map[string]json.RawMessage) []string {
+	ks := make([]string, 0, len(m))
+	for k := range m {
+		ks = append(ks, k)
+	}
+	return ks
+}
+
+// TestChildren_ParentLinkage exercises the nested-children build + ordered apply:
+// buildItemGroups fetches the parent product and prices the child against it,
+// then parentLineId resolves the parent's line id and the child line links to it.
+//
+// Structural test: it reuses 8163 as both parent and child (child pinned to a
+// store so it does not merge with the parent line). Real children would be
+// distinct service/insurance/accessory SKUs.
+func TestChildren_ParentLinkage(t *testing.T) {
+	requireService(t)
+
+	ctx := context.Background()
+	childStore := "1"
+	items := []Item{{
+		Sku:      exampleId,
+		Quantity: 1,
+		Children: []Item{{Sku: exampleId, Quantity: 1, StoreId: &childStore}},
+	}}
+
+	groups := buildItemGroups(ctx, items, "se")
+	if len(groups) != 1 {
+		t.Fatalf("groups = %d, want 1", len(groups))
+	}
+	if groups[0].parent == nil {
+		t.Fatal("parent message not built")
+	}
+	if len(groups[0].children) != 1 {
+		t.Fatalf("children = %d, want 1", len(groups[0].children))
+	}
+
+	// Apply through the real mutation registry to verify the linkage the handler
+	// performs (applyItemGroups does the same with pool.ApplyLocal).
+	reg := cart.NewCartMultationRegistry(cart.NewCartMutationContext(nil))
+	grain := cart.NewCartGrain(1, time.Now())
+
+	if _, err := reg.Apply(ctx, grain, groups[0].parent); err != nil {
+		t.Fatalf("apply parent: %v", err)
+	}
+	pid, ok := parentLineId(grain, groups[0].parent)
+	if !ok {
+		t.Fatal("parentLineId did not resolve the parent line")
+	}
+
+	child := groups[0].children[0]
+	child.ParentId = &pid
+	if _, err := reg.Apply(ctx, grain, child); err != nil {
+		t.Fatalf("apply child: %v", err)
+	}
+
+	if len(grain.Items) != 2 {
+		t.Fatalf("cart items = %d, want 2 (parent + child)", len(grain.Items))
+	}
+
+	var parentLine, childLine *cart.CartItem
+	for _, it := range grain.Items {
+		if it.ParentId == nil {
+			parentLine = it
+		} else {
+			childLine = it
+		}
+	}
+	if parentLine == nil || childLine == nil {
+		t.Fatalf("expected one parent and one child line, got %+v", grain.Items)
+	}
+	if *childLine.ParentId != parentLine.Id {
+		t.Errorf("child.ParentId = %d, want parent line id %d", *childLine.ParentId, parentLine.Id)
+	}
+	t.Logf("parent line %d, child line %d -> parent %d", parentLine.Id, childLine.Id, *childLine.ParentId)
+}

cmd/cart/product-fetcher_test.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func makeProduct(price float64, extra map[string]any) *ProductItem {
+	m := map[string]json.RawMessage{}
+	for k, v := range extra {
+		b, _ := json.Marshal(v)
+		m[k] = b
+	}
+	return &ProductItem{Price: price, Extra: m}
+}
+
+func TestAreaFromItem(t *testing.T) {
+	tests := []struct {
+		name  string
+		extra map[string]any
+		want  float64
+	}{
+		{"floors small window to min", map[string]any{"width": 5, "height": 6}, 0.4}, // 500*600/1e6 = 0.30 -> floor 0.4
+		{"normal window", map[string]any{"width": 10, "height": 10}, 1.0},            // 1000*1000/1e6 = 1.0
+		{"numeric strings", map[string]any{"width": "10", "height": "10"}, 1.0},      // JS Number() parity
+		{"missing height", map[string]any{"width": 10}, 0},
+		{"zero width", map[string]any{"width": 0, "height": 10}, 0},
+		{"non-numeric", map[string]any{"width": "abc", "height": 10}, 0},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got := areaFromItem(makeProduct(0, tc.extra))
+			if got != tc.want {
+				t.Errorf("areaFromItem = %v, want %v", got, tc.want)
+			}
+		})
+	}
+	if got := areaFromItem(nil); got != 0 {
+		t.Errorf("areaFromItem(nil) = %v, want 0", got)
+	}
+}
+
+func TestAccessoryPrice(t *testing.T) {
+	// area 1.0 m^2, child 100.00 -> 100.00 * 100 * 1.0 = 10000 minor units.
+	parent := makeProduct(0, map[string]any{"width": 10, "height": 10})
+	if got := accessoryPrice(parent, makeProduct(100, nil)); got != 10000 {
+		t.Errorf("accessoryPrice = %d, want 10000", got)
+	}
+
+	// area floored to 0.4, child 9952.78 -> round(9952.78 * 100 * 0.4) = 398111.
+	small := makeProduct(0, map[string]any{"width": 5, "height": 6})
+	if got := accessoryPrice(small, makeProduct(9952.78, nil)); got != 398111 {
+		t.Errorf("accessoryPrice = %d, want 398111", got)
+	}
+
+	// parent without dimensions -> area 0 -> price 0.
+	if got := accessoryPrice(makeProduct(0, nil), makeProduct(500, nil)); got != 0 {
+		t.Errorf("accessoryPrice (no dims) = %d, want 0", got)
+	}
+}

cmd/cart/promotions_evaluate.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/promotions"
+)
+
+// newPromotionEvaluateHandler serves POST /promotions/evaluate: it takes a
+// (possibly partial) evaluation context and returns the totals plus the
+// applied/pending promotion effects, without creating or mutating a real cart.
+// An empty body is treated as an empty context (evaluates against no items).
+func newPromotionEvaluateHandler(store *promotions.Store, svc *promotions.PromotionService) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		var req promotions.EvaluateRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil && !errors.Is(err, io.EOF) {
+			http.Error(w, "invalid JSON body: "+err.Error(), http.StatusBadRequest)
+			return
+		}
+		resp := svc.Evaluate(store.Snapshot(), req)
+		w.Header().Set("Content-Type", "application/json")
+		if err := json.NewEncoder(w).Encode(resp); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+	}
+}

cmd/cart/utils.go

@@ -0,0 +1,138 @@
+package main
+
+import (
+	"log"
+	"net/http"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	"git.k6n.net/mats/go-redis-inventory/pkg/inventory"
+)
+
+func getCurrency(country string) string {
+	if country == "no" {
+		return "NOK"
+	}
+	return "SEK"
+}
+
+func getLocale(country string) string {
+	if country == "no" {
+		return "nb-no"
+	}
+	return "sv-se"
+}
+
+func getLocationId(item *cart.CartItem) inventory.LocationID {
+	if item.StoreId == nil || *item.StoreId == "" {
+		return "se"
+	}
+	return inventory.LocationID(*item.StoreId)
+}
+
+func getInventoryRequests(items []*cart.CartItem) []inventory.ReserveRequest {
+	var requests []inventory.ReserveRequest
+	for _, item := range items {
+		if item == nil {
+			continue
+		}
+		requests = append(requests, inventory.ReserveRequest{
+			InventoryReference: &inventory.InventoryReference{
+				SKU:        inventory.SKU(item.Sku),
+				LocationID: getLocationId(item),
+			},
+			Quantity: uint32(item.Quantity),
+		})
+	}
+	return requests
+}
+
+func getOriginalHost(r *http.Request) string {
+	proxyHost := r.Header.Get("X-Forwarded-Host")
+	if proxyHost != "" {
+		return proxyHost
+	}
+	return r.Host
+}
+
+func getClientIp(r *http.Request) string {
+	ip := r.Header.Get("X-Forwarded-For")
+	if ip == "" {
+		ip = r.RemoteAddr
+	}
+	return ip
+}
+
+func CookieCartIdHandler(fn func(cartId cart.CartId, w http.ResponseWriter, r *http.Request) error) func(w http.ResponseWriter, r *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+
+		var id cart.CartId
+		cookie, err := r.Cookie("cartid")
+		if err != nil || cookie.Value == "" {
+			id = cart.MustNewCartId()
+			http.SetCookie(w, &http.Cookie{
+				Name:     "cartid",
+				Value:    id.String(),
+				Secure:   r.TLS != nil,
+				HttpOnly: true,
+				Path:     "/",
+				Expires:  time.Now().AddDate(0, 0, 14),
+				SameSite: http.SameSiteLaxMode,
+			})
+			w.Header().Set("Set-Cart-Id", id.String())
+		} else {
+			parsed, ok := cart.ParseCartId(cookie.Value)
+			if !ok {
+				id = cart.MustNewCartId()
+				http.SetCookie(w, &http.Cookie{
+					Name:     "cartid",
+					Value:    id.String(),
+					Secure:   r.TLS != nil,
+					HttpOnly: true,
+					Path:     "/",
+					Expires:  time.Now().AddDate(0, 0, 14),
+					SameSite: http.SameSiteLaxMode,
+				})
+				w.Header().Set("Set-Cart-Id", id.String())
+			} else {
+				id = parsed
+			}
+		}
+
+		err = fn(id, w, r)
+		if err != nil {
+			log.Printf("Server error, not remote error: %v\n", err)
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte(err.Error()))
+		}
+
+	}
+}
+
+func CartIdHandler(fn func(cartId cart.CartId, w http.ResponseWriter, r *http.Request) error) func(w http.ResponseWriter, r *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		var id cart.CartId
+		raw := r.PathValue("id")
+		// If no id supplied, generate a new one
+		if raw == "" {
+			id := cart.MustNewCartId()
+			w.Header().Set("Set-Cart-Id", id.String())
+		} else {
+			// Parse base62 cart id
+			if parsedId, ok := cart.ParseCartId(raw); !ok {
+				w.WriteHeader(http.StatusBadRequest)
+				w.Write([]byte("cart id is invalid"))
+				return
+			} else {
+				id = parsedId
+			}
+		}
+
+		err := fn(id, w, r)
+		if err != nil {
+			log.Printf("Server error, not remote error: %v\n", err)
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte(err.Error()))
+		}
+	}
+}

cmd/checkout/adyen-handlers.go

@@ -0,0 +1,312 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log"
+	"net/http"
+	"net/url"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	messages "git.k6n.net/mats/go-cart-actor/proto/checkout"
+	adyenCheckout "github.com/adyen/adyen-go-api-library/v21/src/checkout"
+	"github.com/adyen/adyen-go-api-library/v21/src/common"
+	"github.com/adyen/adyen-go-api-library/v21/src/hmacvalidator"
+	"github.com/adyen/adyen-go-api-library/v21/src/webhook"
+	"github.com/google/uuid"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/known/anypb"
+	"google.golang.org/protobuf/types/known/timestamppb"
+)
+
+type SessionRequest struct {
+	SessionId     *string `json:"sessionId,omitempty"`
+	SessionResult string  `json:"sessionResult"`
+	SessionData   *string `json:"sessionData,omitempty"`
+}
+
+// func (s *CheckoutPoolServer) AdyenSessionHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
+
+// 	grain, err := s.Get(r.Context(), uint64(cartId))
+// 	if err != nil {
+// 		return err
+// 	}
+// 	if r.Method == http.MethodGet {
+// 		service := s.adyenClient.Checkout()
+// 		req := service.PaymentsApi.GetResultOfPaymentSessionInput(pa).SessionResult(payload.SessionResult)
+// 		res, _, err := service.PaymentsApi.GetResultOfPaymentSession(r.Context(), req)
+// 		if err != nil {
+// 			return err
+// 		}
+// 		return s.WriteResult(w, res)
+// 	} else {
+// 		payload := &SessionRequest{}
+// 		if err := json.NewDecoder(r.Body).Decode(payload); err != nil {
+// 			return err
+// 		}
+// 		service := s.adyenClient.Checkout()
+// 		req := service.PaymentsApi.GetResultOfPaymentSessionInput(payload.SessionId).SessionResult(payload.SessionResult)
+// 		res, _, err := service.PaymentsApi.GetResultOfPaymentSession(r.Context(), req)
+// 		if err != nil {
+// 			return err
+// 		}
+// 		return s.WriteResult(w, res)
+// 	}
+
+// }
+
+func getCheckoutIdFromNotificationItem(item webhook.NotificationRequestItem) (*cart.CartId, error) {
+	cartId, ok := cart.ParseCartId(item.MerchantReference)
+	if !ok {
+		log.Printf("The notification does not have a valid cartId: %s", item.MerchantReference)
+		return nil, errors.New("invalid cart id")
+	}
+	return &cartId, nil
+}
+
+func (s *CheckoutPoolServer) AdyenHookHandler(w http.ResponseWriter, r *http.Request) {
+	var notificationRequest webhook.Webhook
+	service := s.adyenClient.Checkout()
+	if err := json.NewDecoder(r.Body).Decode(&notificationRequest); err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	for _, notificationItem := range *notificationRequest.NotificationItems {
+		item := notificationItem.NotificationRequestItem
+		log.Printf("Recieved notification event code: %s, %+v", item.EventCode, item)
+
+		isValid := hmacvalidator.ValidateHmac(item, hmacKey)
+		if !isValid {
+			log.Printf("notification hmac not valid %s, %v", item.EventCode, item)
+			http.Error(w, "Invalid HMAC", http.StatusUnauthorized)
+			return
+		} else {
+			// Marshal item data for PaymentEvent
+			dataBytes, err := json.Marshal(item)
+			if err != nil {
+				log.Printf("error marshaling item: %v", err)
+				http.Error(w, "Error marshaling item", http.StatusInternalServerError)
+				return
+			}
+			switch item.EventCode {
+			case "CAPTURE":
+				checkoutId, err := getCheckoutIdFromNotificationItem(item)
+				if err != nil {
+					log.Printf("Could not get checkout id: %v", err)
+					http.Error(w, err.Error(), http.StatusBadRequest)
+					return
+				}
+
+				log.Printf("Capture status: %v", item.Success)
+				isSuccess := item.Success == "true"
+
+				// If successful, apply payment completed
+				//if isSuccess {
+				if err := s.ApplyAnywhere(r.Context(), *checkoutId,
+					&messages.PaymentEvent{
+						PaymentId: item.PspReference,
+						Success:   isSuccess,
+						Name:      item.EventCode,
+						Data:      &anypb.Any{Value: dataBytes},
+					}, &messages.PaymentCompleted{
+						PaymentId:          item.PspReference,
+						Status:             item.Success,
+						Amount:             item.Amount.Value,
+						Currency:           item.Amount.Currency,
+						ProcessorReference: &item.PspReference,
+						CompletedAt:        timestamppb.New(time.Now()),
+					}); err != nil {
+					http.Error(w, "Message not parsed", http.StatusInternalServerError)
+					return
+				}
+				//}
+
+				// CAPTURE is the moment the Adyen payment is fully settled — the
+				// Adyen analogue of the Klarna push. Create the event-sourced
+				// order now (mirrors KlarnaPushHandler). Idempotent on
+				// "checkout-{checkoutId}", so a retried CAPTURE won't duplicate.
+				if isSuccess && s.orderClient != nil {
+					s.createAdyenOrder(r.Context(), *checkoutId, item)
+				}
+
+			case "AUTHORISATION":
+
+				isSuccess := item.Success == "true"
+				log.Printf("Handling auth: %+v", item)
+				checkoutId, err := getCheckoutIdFromNotificationItem(item)
+				if err != nil {
+					log.Printf("Could not get checkout id: %v", err)
+					http.Error(w, err.Error(), http.StatusBadRequest)
+					return
+				}
+				msgs := []proto.Message{
+					&messages.PaymentEvent{
+						PaymentId: item.PspReference,
+						Success:   isSuccess,
+						Name:      item.EventCode,
+						Data:      &anypb.Any{Value: dataBytes},
+					},
+				}
+				if isSuccess {
+					msgs = append(msgs, &messages.PaymentCompleted{
+						PaymentId:   item.PspReference,
+						Status:      item.Success,
+						Amount:      item.Amount.Value,
+						CompletedAt: timestamppb.Now(),
+					})
+				} else {
+					msgs = append(msgs, &messages.PaymentDeclined{
+						PaymentId: item.PspReference,
+						Message:   item.Reason,
+					})
+				}
+				if err := s.ApplyAnywhere(r.Context(), *checkoutId, msgs...); err != nil {
+					log.Printf("error applying authorization event: %v", err)
+					http.Error(w, err.Error(), http.StatusInternalServerError)
+					return
+				}
+
+				// If successful authorization, trigger capture
+				if isSuccess {
+
+					pspReference := item.PspReference
+					uid := uuid.New().String()
+					ref := checkoutId.String()
+					req := service.ModificationsApi.CaptureAuthorisedPaymentInput(pspReference).IdempotencyKey(uid).PaymentCaptureRequest(adyenCheckout.PaymentCaptureRequest{
+						Amount:          adyenCheckout.Amount(item.Amount),
+						MerchantAccount: "ElgigantenECOM",
+						Reference:       &ref,
+					})
+					res, _, err := service.ModificationsApi.CaptureAuthorisedPayment(r.Context(), req)
+					if err != nil {
+						log.Printf("Error capturing payment: %v", err)
+					} else {
+						// Capture requested. The order is NOT created here — we
+						// only have a PSP reference, not an order. Adyen sends a
+						// CAPTURE notification once the capture settles, and the
+						// CAPTURE branch above creates the event-sourced order.
+						log.Printf("Payment capture requested successfully: %+v", res)
+					}
+				}
+			default:
+				log.Printf("Unknown event code: %s", item.EventCode)
+				log.Printf("Item data: %+v", item)
+				isSuccess := item.Success == "true"
+				checkoutId, err := getCheckoutIdFromNotificationItem(item)
+				if err != nil {
+					log.Printf("Could not get checkout id: %v", err)
+
+				} else {
+					if err := s.ApplyAnywhere(r.Context(), *checkoutId, &messages.PaymentEvent{
+						PaymentId: item.PspReference,
+						Success:   isSuccess,
+						Name:      item.EventCode,
+						Data:      &anypb.Any{Value: dataBytes},
+					}); err != nil {
+						log.Printf("error applying payment event: %v", err)
+					}
+				}
+			}
+		}
+	}
+
+	w.WriteHeader(http.StatusAccepted)
+
+}
+
+// createAdyenOrder turns a settled (captured) Adyen payment into an
+// event-sourced order, mirroring KlarnaPushHandler. The Adyen webhook carries
+// the charged amount + currency but not the shopper's country/locale, so those
+// are derived from the currency. Failures are logged and left for the next
+// CAPTURE notification to retry — the from-checkout endpoint is idempotent on
+// "checkout-{checkoutId}".
+func (s *CheckoutPoolServer) createAdyenOrder(ctx context.Context, checkoutId cart.CartId, item webhook.NotificationRequestItem) {
+	grain, err := s.GetAnywhere(ctx, checkoutId)
+	if err != nil {
+		log.Printf("from-checkout: could not load checkout grain %s: %v", checkoutId.String(), err)
+		return
+	}
+
+	// Reserve inventory once, guarded by the grain flag so a retried CAPTURE
+	// does not decrement stock twice. (Same as the Klarna path.)
+	if s.inventoryService != nil && grain.CartState != nil && !grain.InventoryReserved {
+		if rerr := s.inventoryService.ReserveInventory(ctx, getInventoryRequests(grain.CartState.Items)...); rerr != nil {
+			log.Printf("from-checkout: inventory reservation failed for %s: %v", checkoutId.String(), rerr)
+		} else {
+			s.Apply(ctx, uint64(grain.Id), &messages.InventoryReserved{
+				Id:     grain.Id.String(),
+				Status: "success",
+			})
+		}
+	}
+
+	country := getCountryFromCurrency(item.Amount.Currency)
+	if _, oerr := createOrderFromSettledCheckout(ctx, s, grain, settledPayment{
+		Provider:  "adyen",
+		Reference: item.PspReference,
+		Amount:    item.Amount.Value,
+		Currency:  item.Amount.Currency,
+		Country:   country,
+		Locale:    getLocale(country),
+	}); oerr != nil {
+		log.Printf("from-checkout failed for checkout %s; will retry on next CAPTURE: %v", checkoutId.String(), oerr)
+	}
+}
+
+func (s *CheckoutPoolServer) AdyenReturnHandler(w http.ResponseWriter, r *http.Request) {
+	log.Println("Redirect received")
+
+	service := s.adyenClient.Checkout()
+
+	req := service.PaymentsApi.GetResultOfPaymentSessionInput(r.URL.Query().Get("sessionId"))
+
+	res, httpRes, err := service.PaymentsApi.GetResultOfPaymentSession(r.Context(), req)
+	log.Printf("got payment session %+v", res)
+
+	dreq := service.PaymentsApi.PaymentsDetailsInput()
+	dreq = dreq.PaymentDetailsRequest(adyenCheckout.PaymentDetailsRequest{
+		Details: adyenCheckout.PaymentCompletionDetails{
+			RedirectResult: common.PtrString(r.URL.Query().Get("redirectResult")),
+			Payload:        common.PtrString(r.URL.Query().Get("payload")),
+		},
+	})
+
+	dres, httpRes, err := service.PaymentsApi.PaymentsDetails(r.Context(), dreq)
+
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	log.Printf("Payment details response: %+v", dres)
+
+	if !common.IsNil(dres.PspReference) && *dres.PspReference != "" {
+		var redirectURL string
+		// Conditionally handle different result codes for the shopper
+		switch *dres.ResultCode {
+		case "Authorised":
+			redirectURL = "/result/success"
+		case "Pending", "Received":
+			redirectURL = "/result/pending"
+		case "Refused":
+			redirectURL = "/result/failed"
+		default:
+			reason := ""
+			if dres.RefusalReason != nil {
+				reason = *dres.RefusalReason
+			} else {
+				reason = *dres.ResultCode
+			}
+			log.Printf("Payment failed: %s", reason)
+			redirectURL = fmt.Sprintf("/result/error?reason=%s", url.QueryEscape(reason))
+		}
+		http.Redirect(w, r, redirectURL, http.StatusFound)
+		return
+	}
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(httpRes.StatusCode)
+	json.NewEncoder(w).Encode(httpRes.Status)
+}

cmd/checkout/amqp-order-handler.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	amqp "github.com/rabbitmq/amqp091-go"
+)
+
+type AmqpOrderHandler struct {
+	conn  *amqp.Connection
+	queue *amqp.Queue
+}
+
+func NewAmqpOrderHandler(conn *amqp.Connection) *AmqpOrderHandler {
+	return &AmqpOrderHandler{
+		conn: conn,
+	}
+}
+
+func (h *AmqpOrderHandler) DefineQueue() error {
+	ch, err := h.conn.Channel()
+	if err != nil {
+		return fmt.Errorf("failed to open a channel: %w", err)
+	}
+	defer ch.Close()
+
+	queue, err := ch.QueueDeclare(
+		"order-queue", // name
+		false,
+		false,
+		false,
+		false,
+		nil,
+	)
+	if err != nil {
+		return fmt.Errorf("failed to declare an exchange: %w", err)
+	}
+	h.queue = &queue
+	return nil
+}
+
+func (h *AmqpOrderHandler) OrderCompleted(body []byte) error {
+	ch, err := h.conn.Channel()
+	if err != nil {
+		return fmt.Errorf("failed to open a channel: %w", err)
+	}
+	defer ch.Close()
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	return ch.PublishWithContext(ctx,
+		"",           // exchange
+		h.queue.Name, // routing key
+		false,        // mandatory
+		false,        // immediate
+		amqp.Publishing{
+			//DeliveryMode: amqp.,
+			ContentType: "application/json",
+			Body:        body,
+		})
+
+}

cmd/checkout/cart-client.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+)
+
+type CartClient struct {
+	httpClient   *http.Client
+	baseUrl      string
+	agentProfile string // UCP-Agent profile URI
+}
+
+func NewCartClient(baseUrl string) *CartClient {
+	profile := os.Getenv("UCP_AGENT_PROFILE")
+	if profile == "" {
+		profile = "https://checkout.k6n.net/.well-known/ucp"
+	}
+	return &CartClient{
+		httpClient:   &http.Client{Timeout: 10 * time.Second},
+		baseUrl:      baseUrl,
+		agentProfile: profile,
+	}
+}
+
+// func (c *CartClient) ApplyMutation(cartId cart.CartId, mutation proto.Message) error {
+// 	url := fmt.Sprintf("%s/internal/cart/%s/mutation", c.baseUrl, cartId.String())
+// 	data, err := proto.Marshal(mutation)
+// 	if err != nil {
+// 		return err
+// 	}
+// 	req, err := http.NewRequest("POST", url, bytes.NewReader(data))
+// 	if err != nil {
+// 		return err
+// 	}
+// 	req.Header.Set("Content-Type", "application/protobuf")
+// 	resp, err := c.httpClient.Do(req)
+// 	if err != nil {
+// 		return err
+// 	}
+// 	defer resp.Body.Close()
+// 	if resp.StatusCode != http.StatusOK {
+// 		return fmt.Errorf("cart mutation failed: %s", resp.Status)
+// 	}
+// 	return nil
+// }
+
+func (s *CartClient) getCartGrain(ctx context.Context, cartId cart.CartId) (*cart.CartGrain, error) {
+	// Call cart service to get grain
+	url := fmt.Sprintf("%s/cart/byid/%s", s.baseUrl, cartId.String())
+	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("UCP-Agent", `profile="`+s.agentProfile+`"`)
+	resp, err := s.httpClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		log.Printf("request to %s failed with status %s", url, resp.Status)
+		return nil, fmt.Errorf("failed to get cart: %s", resp.Status)
+	}
+	var grain cart.CartGrain
+	err = json.NewDecoder(resp.Body).Decode(&grain)
+	return &grain, err
+}

cmd/checkout/cart-client_test.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"context"
+	"testing"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+)
+
+// TestGetCartGrain_RealService tests against the actual service at https://cart.k6n.net/
+// This test is skipped by default and can be run with: go test -run TestGetCartGrain_RealService
+func TestGetCartGrain_RealService(t *testing.T) {
+	t.Skip("Skipping integration test against real service")
+
+	client := NewCartClient("https://cart.k6n.net")
+
+	// You would need a real cart ID that exists in the system
+	// For example: cartId := cart.NewCartId(123, 456)
+	cartId := cart.MustParseCartId("JkfG6bRNLMy")
+
+	grain, err := client.getCartGrain(context.Background(), cartId)
+	if err != nil {
+		t.Fatalf("Failed to get cart grain: %v", err)
+	}
+
+	if grain == nil {
+		t.Fatal("Expected grain to be non-nil")
+	}
+
+	t.Logf("Successfully retrieved cart grain: %+v", grain)
+}

cmd/checkout/checkout_builder.go

@@ -0,0 +1,238 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+	"strings"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	"git.k6n.net/mats/go-cart-actor/pkg/checkout"
+	adyenCheckout "github.com/adyen/adyen-go-api-library/v21/src/checkout"
+	"github.com/adyen/adyen-go-api-library/v21/src/common"
+)
+
+// defaultCallbackBaseURL is where Klarna's server-to-server callbacks
+// (push/notification/validate) are sent when CHECKOUT_CALLBACK_BASE_URL is unset.
+// These must be a publicly reachable https origin for the checkout service.
+const defaultCallbackBaseURL = "https://cart.k6n.net"
+
+var (
+	// checkoutPublicURL overrides the request-derived site base for the
+	// shopper-facing Klarna URLs (terms/checkout/confirmation). Set this to a
+	// public https origin (e.g. a tunnel or shop-test.tornberg.me) for local
+	// KCO testing, since Klarna rejects non-https merchant_urls. Empty = derive
+	// from the request (X-Forwarded-Host + https).
+	checkoutPublicURL = strings.TrimRight(os.Getenv("CHECKOUT_PUBLIC_URL"), "/")
+	// checkoutCallbackBaseURL is the base for Klarna's server-to-server
+	// callbacks. Defaults to defaultCallbackBaseURL.
+	checkoutCallbackBaseURL = func() string {
+		if v := strings.TrimRight(os.Getenv("CHECKOUT_CALLBACK_BASE_URL"), "/"); v != "" {
+			return v
+		}
+		return defaultCallbackBaseURL
+	}()
+)
+
+// CheckoutMeta carries the external / URL metadata required to build a
+// Klarna CheckoutOrder from a CartGrain snapshot. It deliberately excludes
+// any Klarna-specific response fields (HTML snippet, client token, etc.).
+type CheckoutMeta struct {
+	SiteUrl string
+	// CallbackBaseUrl is the base for Klarna server-to-server callbacks
+	// (push/notification/validate); may differ from SiteUrl in prod where the
+	// checkout service and storefront are on different hosts.
+	CallbackBaseUrl string
+	ClientIp        string
+	Country         string
+	Currency        string // optional override (defaults to "SEK" if empty)
+	Locale          string // optional override (defaults to "sv-se" if empty)
+}
+
+// BuildCheckoutOrderPayload converts the current cart grain + meta information
+// into a CheckoutOrder domain struct and returns its JSON-serialized payload
+// (to send to Klarna) alongside the structured CheckoutOrder object.
+//
+// This function is PURE: it does not perform any network I/O or mutate the
+// grain. The caller is responsible for:
+//
+//  1. Choosing whether to create or update the Klarna order.
+//  2. Invoking KlarnaClient.CreateOrder / UpdateOrder with the returned payload.
+//  3. Applying an InitializeCheckout mutation (or equivalent) with the
+//     resulting Klarna order id + status.
+//
+// If you later need to support different tax rates per line, you can extend
+// CartItem / Delivery to expose that data and propagate it here.
+func BuildCheckoutOrderPayload(grain *checkout.CheckoutGrain, meta *CheckoutMeta) ([]byte, *CheckoutOrder, error) {
+	if grain == nil {
+		return nil, nil, fmt.Errorf("nil grain")
+	}
+	if meta == nil {
+		return nil, nil, fmt.Errorf("nil checkout meta")
+	}
+
+	currency := meta.Currency
+	if currency == "" {
+		currency = "SEK"
+	}
+	locale := meta.Locale
+	if locale == "" {
+		locale = "sv-se"
+	}
+	country := meta.Country
+	if country == "" {
+		country = "SE" // sensible default; adjust if multi-country support changes
+	}
+
+	lines := make([]*Line, 0, len(grain.CartState.Items)+len(grain.Deliveries))
+
+	// Item lines
+	for _, it := range grain.CartState.Items {
+		if it == nil {
+			continue
+		}
+		lines = append(lines, &Line{
+			Type:           "physical",
+			Reference:      it.Sku,
+			Name:           it.Meta.Name,
+			Quantity:       int(it.Quantity),
+			UnitPrice:      int(it.Price.IncVat),
+			TaxRate:        it.Tax, // TODO: derive if variable tax rates are introduced
+			QuantityUnit:   "st",
+			TotalAmount:    int(it.TotalPrice.IncVat),
+			TotalTaxAmount: int(it.TotalPrice.TotalVat()),
+			ImageURL:       fmt.Sprintf("https://www.elgiganten.se%s", it.Meta.Image),
+		})
+	}
+
+	total := cart.NewPrice()
+	total.Add(*grain.CartState.TotalPrice)
+
+	// Delivery lines
+	for _, d := range grain.Deliveries {
+		if d == nil || d.Price.IncVat <= 0 {
+			continue
+		}
+		//total.Add(d.Price)
+		lines = append(lines, &Line{
+			Type:           "shipping_fee",
+			Reference:      d.Provider,
+			Name:           "Delivery",
+			Quantity:       1,
+			UnitPrice:      int(d.Price.IncVat),
+			TaxRate:        2500,
+			QuantityUnit:   "st",
+			TotalAmount:    int(d.Price.IncVat),
+			TotalTaxAmount: int(d.Price.TotalVat()),
+		})
+	}
+
+	order := &CheckoutOrder{
+		PurchaseCountry:    country,
+		PurchaseCurrency:   currency,
+		Locale:             locale,
+		OrderAmount:        int(total.IncVat),
+		OrderTaxAmount:     int(total.TotalVat()),
+		OrderLines:         lines,
+		MerchantReference1: grain.Id.String(),
+		MerchantURLS: &CheckoutMerchantURLS{
+			Terms:        fmt.Sprintf("%s/terms", meta.SiteUrl),
+			Checkout:     fmt.Sprintf("%s/kassa?order_id={checkout.order.id}&provider=klarna", meta.SiteUrl),
+			Confirmation: fmt.Sprintf("%s/kassa?order_id={checkout.order.id}&provider=klarna", meta.SiteUrl),
+			Notification: fmt.Sprintf("%s/payment/klarna/notification", meta.CallbackBaseUrl),
+			Validation:   fmt.Sprintf("%s/payment/klarna/validate", meta.CallbackBaseUrl),
+			Push:         fmt.Sprintf("%s/payment/klarna/push?order_id={checkout.order.id}", meta.CallbackBaseUrl),
+		},
+	}
+
+	payload, err := json.Marshal(order)
+	if err != nil {
+		return nil, nil, fmt.Errorf("marshal checkout order: %w", err)
+	}
+
+	return payload, order, nil
+}
+
+func GetCheckoutMetaFromRequest(r *http.Request) *CheckoutMeta {
+	host := getOriginalHost(r)
+	country := getCountryFromHost(host)
+	siteUrl := fmt.Sprintf("%s://%s", getScheme(r), host)
+	if checkoutPublicURL != "" {
+		siteUrl = checkoutPublicURL
+	}
+	return &CheckoutMeta{
+		ClientIp:        getClientIp(r),
+		SiteUrl:         siteUrl,
+		CallbackBaseUrl: checkoutCallbackBaseURL,
+		Country:         country,
+		Currency:        getCurrency(country),
+		Locale:          getLocale(country),
+	}
+}
+
+func BuildAdyenCheckoutSession(grain *checkout.CheckoutGrain, meta *CheckoutMeta) (*adyenCheckout.CreateCheckoutSessionRequest, error) {
+	if grain == nil {
+		return nil, fmt.Errorf("nil grain")
+	}
+	if meta == nil {
+		return nil, fmt.Errorf("nil checkout meta")
+	}
+
+	currency := meta.Currency
+	if currency == "" {
+		currency = "SEK"
+	}
+	country := meta.Country
+	if country == "" {
+		country = "SE"
+	}
+
+	lineItems := make([]adyenCheckout.LineItem, 0, len(grain.CartState.Items)+len(grain.Deliveries))
+
+	// Item lines
+	for _, it := range grain.CartState.Items {
+		if it == nil {
+			continue
+		}
+		lineItems = append(lineItems, adyenCheckout.LineItem{
+			Quantity:           common.PtrInt64(int64(it.Quantity)),
+			AmountIncludingTax: common.PtrInt64(it.TotalPrice.IncVat),
+			Description:        common.PtrString(it.Meta.Name),
+			AmountExcludingTax: common.PtrInt64(it.TotalPrice.ValueExVat()),
+			TaxAmount:          common.PtrInt64(it.TotalPrice.TotalVat()),
+			TaxPercentage:      common.PtrInt64(int64(it.Tax)),
+		})
+	}
+	total := cart.NewPrice()
+	total.Add(*grain.CartState.TotalPrice)
+
+	// Delivery lines
+	for _, d := range grain.Deliveries {
+		if d == nil || d.Price.IncVat <= 0 {
+			continue
+		}
+		lineItems = append(lineItems, adyenCheckout.LineItem{
+			Quantity:           common.PtrInt64(1),
+			AmountIncludingTax: common.PtrInt64(d.Price.IncVat),
+			Description:        common.PtrString("Delivery"),
+			AmountExcludingTax: common.PtrInt64(d.Price.ValueExVat()),
+			TaxPercentage:      common.PtrInt64(25),
+		})
+	}
+
+	return &adyenCheckout.CreateCheckoutSessionRequest{
+		Reference: grain.Id.String(),
+		Amount: adyenCheckout.Amount{
+			Value:    total.IncVat,
+			Currency: currency,
+		},
+		CountryCode:     common.PtrString(country),
+		MerchantAccount: "ElgigantenECOM",
+		Channel:         common.PtrString("Web"),
+		ShopperIP:       common.PtrString(meta.ClientIp),
+		ReturnUrl:       fmt.Sprintf("%s/payment/adyen/return", meta.SiteUrl),
+		LineItems:       lineItems,
+	}, nil
+
+}

cmd/checkout/k8s-host-discovery.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"log"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/discovery"
+	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
+)
+
+func GetDiscovery() discovery.Discovery {
+	if podIp == "" {
+		return nil
+	}
+
+	config, kerr := rest.InClusterConfig()
+
+	if kerr != nil {
+		log.Fatalf("Error creating kubernetes client: %v\n", kerr)
+	}
+	client, err := kubernetes.NewForConfig(config)
+	if err != nil {
+		log.Fatalf("Error creating client: %v\n", err)
+	}
+	timeout := int64(30)
+	return discovery.NewK8sDiscovery(client, v1.ListOptions{
+		LabelSelector:  "actor-pool=checkout",
+		TimeoutSeconds: &timeout,
+	})
+}
+
+func UseDiscovery(pool discovery.DiscoveryTarget) {
+
+	go func(hw discovery.Discovery) {
+		if hw == nil {
+			log.Print("No discovery service available")
+			return
+		}
+		ch, err := hw.Watch()
+		if err != nil {
+			log.Printf("Discovery error: %v", err)
+			return
+		}
+		for evt := range ch {
+			if evt.Host == "" {
+				continue
+			}
+			switch evt.IsReady {
+			case false:
+				if pool.IsKnown(evt.Host) {
+					log.Printf("Host %s is not ready, removing", evt.Host)
+					pool.RemoveHost(evt.Host)
+				}
+			default:
+				if !pool.IsKnown(evt.Host) {
+					log.Printf("Discovered host %s", evt.Host)
+					pool.AddRemoteHost(evt.Host)
+				}
+			}
+		}
+	}(GetDiscovery())
+}

cmd/checkout/klarna-client.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -30,11 +31,14 @@ const (
 	KlarnaPlaygroundUrl = "https://api.playground.klarna.com"
 )
 
-func (k *KlarnaClient) GetOrder(orderId string) (*CheckoutOrder, error) {
+func (k *KlarnaClient) GetOrder(ctx context.Context, orderId string) (*CheckoutOrder, error) {
 	req, err := http.NewRequest("GET", k.Url+"/checkout/v3/orders/"+orderId, nil)
 	if err != nil {
 		return nil, err
 	}
+	spanCtx, span := tracer.Start(ctx, "Get klarna order")
+	defer span.End()
+	req = req.WithContext(spanCtx)
 	req.Header.Add("Content-Type", "application/json")
 	req.SetBasicAuth(k.UserName, k.Password)
 
@@ -64,17 +68,19 @@ func (k *KlarnaClient) getOrderResponse(res *http.Response) (*CheckoutOrder, err
 	return nil, fmt.Errorf("%s", res.Status)
 }
 
-func (k *KlarnaClient) CreateOrder(reader io.Reader) (*CheckoutOrder, error) {
+func (k *KlarnaClient) CreateOrder(ctx context.Context, reader io.Reader) (*CheckoutOrder, error) {
 	//bytes.NewReader(reply.Payload)
 	req, err := http.NewRequest("POST", k.Url+"/checkout/v3/orders", reader)
 	if err != nil {
 		return nil, err
 	}
-
+	spanCtx, span := tracer.Start(ctx, "Create klarna order")
+	defer span.End()
+	req = req.WithContext(spanCtx)
 	req.Header.Add("Content-Type", "application/json")
 	req.SetBasicAuth(k.UserName, k.Password)
 
-	res, err := http.DefaultClient.Do(req)
+	res, err := k.client.Do(req)
 	if nil != err {
 		return nil, err
 	}
@@ -82,17 +88,20 @@ func (k *KlarnaClient) CreateOrder(reader io.Reader) (*CheckoutOrder, error) {
 	return k.getOrderResponse(res)
 }
 
-func (k *KlarnaClient) UpdateOrder(orderId string, reader io.Reader) (*CheckoutOrder, error) {
+func (k *KlarnaClient) UpdateOrder(ctx context.Context, orderId string, reader io.Reader) (*CheckoutOrder, error) {
 	//bytes.NewReader(reply.Payload)
 	req, err := http.NewRequest("POST", fmt.Sprintf("%s/checkout/v3/orders/%s", k.Url, orderId), reader)
 	if err != nil {
 		return nil, err
 	}
 
+	spanCtx, span := tracer.Start(ctx, "Update klarna order")
+	defer span.End()
+	req = req.WithContext(spanCtx)
 	req.Header.Add("Content-Type", "application/json")
 	req.SetBasicAuth(k.UserName, k.Password)
 
-	res, err := http.DefaultClient.Do(req)
+	res, err := k.client.Do(req)
 	if nil != err {
 		return nil, err
 	}
@@ -100,29 +109,34 @@ func (k *KlarnaClient) UpdateOrder(orderId string, reader io.Reader) (*CheckoutO
 	return k.getOrderResponse(res)
 }
 
-func (k *KlarnaClient) AbortOrder(orderId string) error {
+func (k *KlarnaClient) AbortOrder(ctx context.Context, orderId string) error {
 	req, err := http.NewRequest("POST", fmt.Sprintf("%s/checkout/v3/orders/%s/abort", k.Url, orderId), nil)
 	if err != nil {
 		return err
 	}
-
+	spanCtx, span := tracer.Start(ctx, "Abort klarna order")
+	defer span.End()
+	req = req.WithContext(spanCtx)
 	req.SetBasicAuth(k.UserName, k.Password)
 
-	_, err = http.DefaultClient.Do(req)
+	_, err = k.client.Do(req)
 	return err
 }
 
 // ordermanagement/v1/orders/{order_id}/acknowledge
-func (k *KlarnaClient) AcknowledgeOrder(orderId string) error {
+func (k *KlarnaClient) AcknowledgeOrder(ctx context.Context, orderId string) error {
 	req, err := http.NewRequest("POST", fmt.Sprintf("%s/ordermanagement/v1/orders/%s/acknowledge", k.Url, orderId), nil)
 	if err != nil {
 		return err
 	}
+	spanCtx, span := tracer.Start(ctx, "Acknowledge klarna order")
+	defer span.End()
+	req = req.WithContext(spanCtx)
 	id := uuid.New()
 
 	req.SetBasicAuth(k.UserName, k.Password)
 	req.Header.Add("Klarna-Idempotency-Key", id.String())
 
-	_, err = http.DefaultClient.Do(req)
+	_, err = k.client.Do(req)
 	return err
 }

cmd/checkout/klarna-handlers.go

@@ -0,0 +1,355 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	"git.k6n.net/mats/go-cart-actor/pkg/checkout"
+	messages "git.k6n.net/mats/go-cart-actor/proto/checkout"
+	"git.k6n.net/mats/go-redis-inventory/pkg/inventory"
+	"google.golang.org/protobuf/types/known/timestamppb"
+)
+
+/*
+ *
+ *
+ * s.CheckoutHandler(func(order *CheckoutOrder, w http.ResponseWriter) error {
+		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+		w.Header().Set("Permissions-Policy", "payment=(self \"https://js.stripe.com\" \"https://m.stripe.network\" \"https://js.playground.kustom.co\")")
+		w.WriteHeader(http.StatusOK)
+		_, err := fmt.Fprintf(w, tpl, order.HTMLSnippet)
+		return err
+	})
+*/
+
+// func (s *CheckoutPoolServer) KlarnaHtmlCheckoutHandler(w http.ResponseWriter, r *http.Request, checkoutId checkout.CheckoutId) error {
+
+// 	orderId := r.URL.Query().Get("order_id")
+// 	var order *CheckoutOrder
+// 	var err error
+// 	if orderId == "" {
+// 		order, err = s.CreateOrUpdateCheckout(r, checkoutId)
+// 		if err != nil {
+// 			logger.Error("unable to create klarna session", "error", err)
+// 			return err
+// 		}
+// 		// s.ApplyKlarnaPaymentStarted(r.Context(), order, checkoutId)
+
+// 	}
+// 	order, err = s.klarnaClient.GetOrder(r.Context(), orderId)
+// 	if err != nil {
+// 		return err
+// 	}
+// 	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+// 	w.Header().Set("Permissions-Policy", "payment=(self \"https://js.stripe.com\" \"https://m.stripe.network\" \"https://js.playground.kustom.co\")")
+// 	w.WriteHeader(http.StatusOK)
+// 	_, err = fmt.Fprintf(w, tpl, order.HTMLSnippet)
+// 	return err
+
+// }
+
+// func (s *CheckoutPoolServer) KlarnaSessionHandler(w http.ResponseWriter, r *http.Request, checkoutId checkout.CheckoutId) error {
+
+// 	orderId := r.URL.Query().Get("order_id")
+// 	var order *CheckoutOrder
+// 	var err error
+// 	if orderId == "" {
+// 		order, err = s.CreateOrUpdateCheckout(r, checkoutId)
+// 		if err != nil {
+// 			logger.Error("unable to create klarna session", "error", err)
+// 			return err
+// 		}
+// 		// s.ApplyKlarnaPaymentStarted(r.Context(), order, checkoutId)
+
+// 	}
+// 	order, err = s.klarnaClient.GetOrder(r.Context(), orderId)
+// 	if err != nil {
+// 		return err
+// 	}
+// 	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+// 	return json.NewEncoder(w).Encode(order)
+
+// }
+
+func (s *CheckoutPoolServer) KlarnaConfirmationHandler(w http.ResponseWriter, r *http.Request) {
+
+	orderId := r.PathValue("order_id")
+	order, err := s.klarnaClient.GetOrder(r.Context(), orderId)
+
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte(err.Error()))
+		return
+	}
+
+	// Apply ConfirmationViewed mutation
+	cartId, ok := cart.ParseCartId(order.MerchantReference1)
+	if ok {
+		s.Apply(r.Context(), uint64(cartId), &messages.ConfirmationViewed{})
+	}
+
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	if order.Status == "checkout_complete" {
+		http.SetCookie(w, &http.Cookie{
+			Name:     "cartid",
+			Value:    "",
+			Path:     "/",
+			Secure:   true,
+			HttpOnly: true,
+			Expires:  time.Unix(0, 0),
+			SameSite: http.SameSiteLaxMode,
+		})
+	}
+
+	w.WriteHeader(http.StatusOK)
+	fmt.Fprintf(w, tpl, order.HTMLSnippet)
+
+}
+
+func (s *CheckoutPoolServer) KlarnaValidationHandler(w http.ResponseWriter, r *http.Request) {
+	log.Printf("Klarna order validation, method: %s", r.Method)
+	if r.Method != "POST" {
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		return
+	}
+	order := &CheckoutOrder{}
+	err := json.NewDecoder(r.Body).Decode(order)
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+	logger.InfoContext(r.Context(), "Klarna order validation received", "order_id", order.ID, "cart_id", order.MerchantReference1)
+	grain, err := s.getGrainFromKlarnaOrder(r.Context(), order)
+	if err != nil {
+		logger.ErrorContext(r.Context(), "Unable to get grain from klarna order", "error", err.Error())
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	s.reserveInventory(r.Context(), grain)
+
+	w.WriteHeader(http.StatusOK)
+
+}
+
+func (s *CheckoutPoolServer) KlarnaNotificationHandler(w http.ResponseWriter, r *http.Request) {
+
+	log.Printf("Klarna order notification, method: %s", r.Method)
+	logger.InfoContext(r.Context(), "Klarna order notification received", "method", r.Method)
+	if r.Method != "POST" {
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		return
+	}
+	order := &CheckoutOrder{}
+	err := json.NewDecoder(r.Body).Decode(order)
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+	log.Printf("Klarna order notification: %s", order.ID)
+	logger.InfoContext(r.Context(), "Klarna order notification received", "order_id", order.ID)
+
+	w.WriteHeader(http.StatusOK)
+
+}
+
+func (s *CheckoutPoolServer) KlarnaPushHandler(w http.ResponseWriter, r *http.Request) {
+	log.Printf("Klarna order confirmation push, method: %s", r.Method)
+	if r.Method != http.MethodPost {
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		return
+	}
+	orderId := r.URL.Query().Get("order_id")
+	log.Printf("Order confirmation push: %s", orderId)
+
+	order, err := s.klarnaClient.GetOrder(r.Context(), orderId)
+
+	if err != nil {
+		log.Printf("Error creating request: %v\n", err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	grain, err := s.getGrainFromKlarnaOrder(r.Context(), order)
+	if err != nil {
+		logger.ErrorContext(r.Context(), "Unable to get grain from klarna order", "error", err.Error())
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	if s.inventoryService != nil {
+		inventoryRequests := getInventoryRequests(grain.CartState.Items)
+		invStatus := "success"
+		if err = s.inventoryService.ReserveInventory(r.Context(), inventoryRequests...); err != nil {
+			// The payment is already settled at Klarna (checkout_complete), so the
+			// order MUST be created. Inventory is best-effort at this point — a
+			// reservation failure (unstocked / drop-ship / non-tracked items)
+			// must not block order creation. Log it and flag the grain so
+			// fulfillment can reconcile.
+			logger.WarnContext(r.Context(), "klarna push: inventory reservation failed; creating order anyway",
+				"err", err, "checkoutId", grain.Id.String())
+			invStatus = "failed"
+		}
+		s.Apply(r.Context(), uint64(grain.Id), &messages.InventoryReserved{
+			Id:     grain.Id.String(),
+			Status: invStatus,
+		})
+	}
+
+	s.ApplyAnywhere(r.Context(), grain.Id, &messages.PaymentCompleted{
+		PaymentId:          orderId,
+		Status:             "completed",
+		ProcessorReference: &order.ID,
+		Amount:             int64(order.OrderAmount),
+		Currency:           order.PurchaseCurrency,
+		CompletedAt:        timestamppb.Now(),
+	})
+
+	// ── Create the event-sourced order grain (dual-write with AMQP) ────
+	if s.orderClient != nil {
+		if _, orderErr := createOrderFromCheckout(r.Context(), s, grain, order, "klarna"); orderErr != nil {
+			// Non-fatal: the checkout grain is updated, the order can be
+			// created on retry (idempotency key guards against duplicates).
+			logger.WarnContext(r.Context(), "from-checkout failed; will retry on next push",
+				"err", orderErr, "checkoutId", grain.Id.String())
+		}
+	}
+
+	// ── Dual-write: AMQP order-queue for legacy consumers ───────────────
+	if s.orderHandler != nil {
+		legacyBody, _ := buildLegacyOrderJSON(grain, order, "klarna", orderId)
+		if pubErr := s.orderHandler.OrderCompleted(legacyBody); pubErr != nil {
+			logger.WarnContext(r.Context(), "order-queue publish failed", "err", pubErr)
+		}
+	}
+
+	err = s.klarnaClient.AcknowledgeOrder(r.Context(), orderId)
+	if err != nil {
+		log.Printf("Error acknowledging order: %v\n", err)
+	}
+
+	w.WriteHeader(http.StatusOK)
+}
+
+var tpl = `<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>s10r testing - checkout</title>
+  </head>
+
+  <body>
+    %s
+  </body>
+</html>
+`
+
+// createOrderFromCheckout builds and sends the from-checkout request to the
+// order service, creating an event-sourced order grain from the settled checkout.
+// The idempotency key is "checkout-{checkoutId}" so that retries (Klarna may
+// push the same order multiple times) are safe.
+func createOrderFromCheckout(ctx context.Context, s *CheckoutPoolServer, grain *checkout.CheckoutGrain, klarnaOrder *CheckoutOrder, provider string) (*CreateOrderResult, error) {
+	return createOrderFromSettledCheckout(ctx, s, grain, settledPayment{
+		Provider:  provider,
+		Reference: klarnaOrder.ID,
+		Amount:    int64(klarnaOrder.OrderAmount),
+		Currency:  klarnaOrder.PurchaseCurrency,
+		Country:   klarnaOrder.PurchaseCountry,
+		Locale:    klarnaOrder.Locale,
+	})
+}
+
+// buildLegacyOrderJSON builds the go-order-manager compatible JSON for AMQP
+// dual-write, so existing downstream consumers on the order-queue still receive
+// order events during the migration period.
+func buildLegacyOrderJSON(grain *checkout.CheckoutGrain, klarnaOrder *CheckoutOrder, provider string, orderId string) ([]byte, error) {
+	if grain.CartState == nil {
+		return nil, fmt.Errorf("buildLegacyOrderJSON: checkout %s has no cart state", grain.Id)
+	}
+	type legacyLine struct {
+		Reference      string `json:"reference"`
+		Name           string `json:"name"`
+		Quantity       int    `json:"quantity"`
+		UnitPrice      int    `json:"unit_price"`
+		TaxRate        int    `json:"tax_rate"`
+		TotalAmount    int    `json:"total_amount"`
+		TotalTaxAmount int    `json:"total_tax_amount"`
+	}
+	type legacyOrder struct {
+		ID               string       `json:"order_id"`
+		PurchaseCountry  string       `json:"purchase_country"`
+		PurchaseCurrency string       `json:"purchase_currency"`
+		Locale           string       `json:"locale"`
+		OrderAmount      int          `json:"order_amount"`
+		OrderTaxAmount   int          `json:"order_tax_amount"`
+		OrderLines       []legacyLine `json:"order_lines"`
+	}
+
+	lines := make([]legacyLine, 0, len(grain.CartState.Items)+len(grain.Deliveries))
+	for _, it := range grain.CartState.Items {
+		if it == nil {
+			continue
+		}
+		lines = append(lines, legacyLine{
+			Reference:      it.Sku,
+			Name:           it.Meta.Name,
+			Quantity:       int(it.Quantity),
+			UnitPrice:      int(it.Price.IncVat),
+			TaxRate:        it.Tax,
+			TotalAmount:    int(it.TotalPrice.IncVat),
+			TotalTaxAmount: int(it.TotalPrice.TotalVat()),
+		})
+	}
+
+	lo := legacyOrder{
+		ID:               orderId,
+		PurchaseCountry:  klarnaOrder.PurchaseCountry,
+		PurchaseCurrency: klarnaOrder.PurchaseCurrency,
+		Locale:           klarnaOrder.Locale,
+		OrderAmount:      klarnaOrder.OrderAmount,
+		OrderTaxAmount:   klarnaOrder.OrderTaxAmount,
+		OrderLines:       lines,
+	}
+	return json.Marshal(lo)
+}
+
+func getLocationId(item *cart.CartItem) inventory.LocationID {
+	if item.StoreId == nil || *item.StoreId == "" {
+		return "se"
+	}
+	return inventory.LocationID(*item.StoreId)
+}
+
+func getInventoryRequests(items []*cart.CartItem) []inventory.ReserveRequest {
+	var requests []inventory.ReserveRequest
+	for _, item := range items {
+		if item == nil {
+			continue
+		}
+		requests = append(requests, inventory.ReserveRequest{
+			InventoryReference: &inventory.InventoryReference{
+				SKU:        inventory.SKU(item.Sku),
+				LocationID: getLocationId(item),
+			},
+			Quantity: uint32(item.Quantity),
+		})
+	}
+	return requests
+}
+
+func (a *CheckoutPoolServer) getGrainFromKlarnaOrder(ctx context.Context, order *CheckoutOrder) (*checkout.CheckoutGrain, error) {
+	cartId, ok := cart.ParseCartId(order.MerchantReference1)
+	if !ok {
+		return nil, fmt.Errorf("invalid cart id in order reference: %s", order.MerchantReference1)
+	}
+	grain, err := a.GetAnywhere(ctx, cartId)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get cart grain: %w", err)
+	}
+	return grain, nil
+}

cmd/checkout/main.go

@@ -0,0 +1,263 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"os/signal"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/internal/ucp"
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/checkout"
+	"git.k6n.net/mats/go-cart-actor/pkg/proxy"
+	"github.com/adyen/adyen-go-api-library/v21/src/adyen"
+	"github.com/adyen/adyen-go-api-library/v21/src/common"
+	"git.k6n.net/mats/go-redis-inventory/pkg/inventory"
+	amqp "github.com/rabbitmq/amqp091-go"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/redis/go-redis/v9"
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+)
+
+var (
+	grainSpawns = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "checkout_grain_spawned_total",
+		Help: "The total number of spawned checkout grains",
+	})
+)
+
+func init() {
+	os.Mkdir("data", 0755)
+}
+
+type App struct {
+	pool         *actor.SimpleGrainPool[checkout.CheckoutGrain]
+	server       *CheckoutPoolServer
+	klarnaClient *KlarnaClient
+	cartClient   *CartClient // For internal communication to cart
+}
+
+var podIp = os.Getenv("POD_IP")
+var name = os.Getenv("POD_NAME")
+var amqpUrl = os.Getenv("AMQP_URL")
+var redisAddress = os.Getenv("REDIS_ADDRESS")
+var redisPassword = os.Getenv("REDIS_PASSWORD")
+var cartInternalUrl = os.Getenv("CART_INTERNAL_URL") // e.g., http://cart-service:8081
+
+// loadUCPCheckoutSigner loads the UCP ECDSA signing key from the path specified in
+// the UCP_SIGNING_KEY_PATH environment variable. Returns nil if unset or unreadable.
+func loadUCPCheckoutSigner() *ucp.SigningConfig {
+	path := os.Getenv("UCP_SIGNING_KEY_PATH")
+	if path == "" {
+		return nil
+	}
+	pemData, err := os.ReadFile(path)
+	if err != nil {
+		log.Printf("ucp signing: cannot read key %s: %v", path, err)
+		return nil
+	}
+	cfg, err := ucp.NewSigningConfigFromPEM(pemData, "k6n-ecdsa-2026")
+	if err != nil {
+		log.Printf("ucp signing: invalid key at %s: %v", path, err)
+		return nil
+	}
+	return cfg
+}
+
+func main() {
+
+	controlPlaneConfig := actor.DefaultServerConfig()
+
+	reg := checkout.NewCheckoutMutationRegistry(checkout.NewCheckoutMutationContext())
+	reg.RegisterProcessor(
+		actor.NewMutationProcessor(func(ctx context.Context, g *checkout.CheckoutGrain) error {
+			g.Version++
+			return nil
+		}),
+	)
+	rdb := redis.NewClient(&redis.Options{
+		Addr:     redisAddress,
+		Password: redisPassword,
+		DB:       0,
+	})
+	inventoryService, err := inventory.NewRedisInventoryService(rdb)
+	if err != nil {
+		log.Fatalf("Error creating inventory service: %v\n", err)
+	}
+
+	checkoutDir := os.Getenv("CHECKOUT_DIR")
+	if checkoutDir == "" {
+		checkoutDir = "data"
+	}
+	diskStorage := actor.NewDiskStorage[checkout.CheckoutGrain](checkoutDir, reg)
+
+	poolConfig := actor.GrainPoolConfig[checkout.CheckoutGrain]{
+		MutationRegistry: reg,
+		Storage:          diskStorage,
+		Spawn: func(ctx context.Context, id uint64) (actor.Grain[checkout.CheckoutGrain], error) {
+			_, span := tracer.Start(ctx, fmt.Sprintf("Spawn checkout id %d", id))
+			defer span.End()
+			grainSpawns.Inc()
+
+			ret := checkout.NewCheckoutGrain(id, 0, 0, time.Now(), nil) // version to be set later
+			// Load persisted events/state for this checkout if present
+			if err := diskStorage.LoadEvents(ctx, id, ret); err != nil {
+				// Return the grain along with error (e.g., not found) so callers can decide
+				return ret, err
+			}
+			return ret, nil
+		},
+		Destroy: func(grain actor.Grain[checkout.CheckoutGrain]) error {
+			return nil
+		},
+		SpawnHost: func(host string) (actor.Host[checkout.CheckoutGrain], error) {
+			return proxy.NewRemoteHost[checkout.CheckoutGrain](host)
+		},
+		TTL:      1 * time.Hour, // Longer TTL for checkout
+		PoolSize: 65535,
+		Hostname: podIp,
+	}
+
+	pool, err := actor.NewSimpleGrainPool(poolConfig)
+	if err != nil {
+		log.Fatalf("Error creating checkout pool: %v\n", err)
+	}
+
+	adyenClient := adyen.NewClient(&common.Config{
+		ApiKey:      os.Getenv("ADYEN_API_KEY"),
+		Environment: common.TestEnv,
+	})
+
+	klarnaClient := NewKlarnaClient(KlarnaPlaygroundUrl, os.Getenv("KLARNA_API_USERNAME"), os.Getenv("KLARNA_API_PASSWORD"))
+
+	cartClient := NewCartClient(cartInternalUrl)
+
+	var orderClient *OrderClient
+	if orderServiceURL := os.Getenv("ORDER_SERVICE_URL"); orderServiceURL != "" {
+		orderClient = NewOrderClient(orderServiceURL)
+		log.Printf("order client enabled: %s", orderServiceURL)
+	}
+
+	var orderHandler *AmqpOrderHandler
+	conn, err := amqp.Dial(amqpUrl)
+	if err != nil {
+		log.Fatalf("failed to connect to RabbitMQ: %v", err)
+	}
+	orderHandler = NewAmqpOrderHandler(conn)
+	if err := orderHandler.DefineQueue(); err != nil {
+		log.Fatalf("failed to declare order queue: %v", err)
+	}
+
+	syncedServer := NewCheckoutPoolServer(pool, fmt.Sprintf("%s, %s", name, podIp), klarnaClient, cartClient, adyenClient, orderClient, orderHandler)
+	syncedServer.inventoryService = inventoryService
+
+	mux := http.NewServeMux()
+	debugMux := http.NewServeMux()
+
+	if amqpUrl == "" {
+		log.Fatalf("no connection to amqp defined")
+	}
+
+	grpcSrv, err := actor.NewControlServer[checkout.CheckoutGrain](controlPlaneConfig, pool)
+	if err != nil {
+		log.Fatalf("Error starting control plane gRPC server: %v\n", err)
+	}
+	defer grpcSrv.GracefulStop()
+
+	UseDiscovery(pool)
+
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
+	defer stop()
+
+	otelShutdown, err := setupOTelSDK(ctx)
+	if err != nil {
+		log.Fatalf("Unable to start otel %v", err)
+	}
+
+	syncedServer.Serve(mux)
+
+	// UCP REST adapter — Universal Commerce Protocol checkout sessions
+	// When an order service URL is configured, the complete endpoint creates
+	// real orders via the order service's from-checkout API.
+	var ucpOrderSvc ucp.OrderApplier
+	if orderServiceURL := os.Getenv("ORDER_SERVICE_URL"); orderServiceURL != "" {
+		ucpOrderSvc = ucp.NewOrderHTTPClient(orderServiceURL)
+		log.Printf("ucp order applier enabled: %s", orderServiceURL)
+	}
+	checkoutUCP := ucp.CheckoutHandler(pool, ucpOrderSvc)
+	if signer := loadUCPCheckoutSigner(); signer != nil {
+		checkoutUCP = ucp.WithSigning(checkoutUCP, signer)
+		log.Print("ucp signing enabled")
+	}
+	// StripPrefix is required because the sub-mux (CheckoutHandler) registers
+	// routes like "GET /{id}" which expect a relative path; Go's ServeMux
+	// passes the full request path without stripping the prefix.
+	// Only the subtree pattern is registered (see comment in cmd/cart/main.go
+	// for why the exact-match pattern is omitted).
+	mux.Handle("/ucp/v1/checkout-sessions/", http.StripPrefix("/ucp/v1/checkout-sessions", checkoutUCP))
+
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		grainCount, capacity := pool.LocalUsage()
+		if grainCount >= capacity {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte("grain pool at capacity"))
+			return
+		}
+		if !pool.IsHealthy() {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte("control plane not healthy"))
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("ok"))
+	})
+	mux.HandleFunc("/readyz", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("ok"))
+	})
+	mux.HandleFunc("/livez", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("ok"))
+	})
+
+	mux.HandleFunc("/version", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("1.0.0"))
+	})
+
+	srv := &http.Server{
+		Addr:         ":8080",
+		BaseContext:  func(net.Listener) context.Context { return ctx },
+		ReadTimeout:  10 * time.Second,
+		WriteTimeout: 20 * time.Second,
+		Handler:      otelhttp.NewHandler(mux, "/"),
+	}
+
+	defer func() {
+		fmt.Println("Shutting down due to signal")
+		otelShutdown(context.Background())
+		diskStorage.Close()
+		pool.Close()
+	}()
+
+	srvErr := make(chan error, 1)
+	go func() {
+		srvErr <- srv.ListenAndServe()
+	}()
+
+	log.Print("Checkout server started at port 8080")
+
+	go http.ListenAndServe(":8081", debugMux)
+
+	select {
+	case err = <-srvErr:
+		log.Fatalf("Unable to start server: %v", err)
+	case <-ctx.Done():
+		stop()
+	}
+}

cmd/checkout/order_client.go

@@ -0,0 +1,120 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+	"time"
+)
+
+// OrderClient is a minimal HTTP client for the order service. It is the
+// checkout service's counterpart to the CartClient — the same pattern, but
+// calling into order-service endpoints instead of cart-service ones.
+//
+// Currently only CreateOrder is implemented (the from-checkout handoff).
+// Add GetOrder/ListOrders methods as the backoffice order UI evolves.
+type OrderClient struct {
+	httpClient   *http.Client
+	baseURL      string // e.g. "http://order-service:8092"
+	agentProfile string // UCP-Agent profile URI
+}
+
+// NewOrderClient returns a client that talks to the order service at baseURL.
+func NewOrderClient(baseURL string) *OrderClient {
+	profile := os.Getenv("UCP_AGENT_PROFILE")
+	if profile == "" {
+		profile = "https://cart.k6n.net/.well-known/ucp"
+	}
+	return &OrderClient{
+		httpClient:   &http.Client{Timeout: 30 * time.Second},
+		baseURL:      baseURL,
+		agentProfile: profile,
+	}
+}
+
+// CreateOrderReq is the JSON payload POSTed to the order service's
+// /api/orders/from-checkout endpoint. Every field is required except where
+// noted. See cmd/order/handlers_checkout.go for the full definition.
+type CreateOrderReq struct {
+	CheckoutId     string `json:"checkoutId"`
+	IdempotencyKey string `json:"idempotencyKey"`
+
+	CartId        string `json:"cartId"`
+	Currency      string `json:"currency"`
+	Locale        string `json:"locale,omitempty"`
+	Country       string `json:"country"`
+	CustomerEmail string `json:"customerEmail,omitempty"`
+	CustomerName  string `json:"customerName,omitempty"`
+	Lines         []OrderLine `json:"lines"`
+
+	Payment struct {
+		Provider  string `json:"provider"`
+		Reference string `json:"reference"`
+		Amount    int64  `json:"amount"`
+	} `json:"payment"`
+}
+
+// OrderLine is one orderable item in the CreateOrderReq, matching the
+// lineReq type in the order service.
+type OrderLine struct {
+	Reference string `json:"reference"`
+	Sku       string `json:"sku"`
+	Name      string `json:"name"`
+	Quantity  int32  `json:"quantity"`
+	UnitPrice int64  `json:"unitPrice"`
+	TaxRate   int32  `json:"taxRate"`
+}
+
+// CreateOrderResult is the success response from POST /api/orders/from-checkout.
+type CreateOrderResult struct {
+	OrderId string          `json:"orderId"`
+	Flow    json.RawMessage `json:"flow,omitempty"`
+	Order   json.RawMessage `json:"order,omitempty"`
+	// Existing is true when the response is a 409 Conflict — the idempotency
+	// key was already used and this is the previously-created order.
+	Existing bool `json:"existing,omitempty"`
+}
+
+// CreateOrder sends a settled checkout's data to the order service and returns
+// the created (or previously-created, via idempotency) order. An idempotencyKey
+// should be generated per checkout (e.g. "checkout-{checkoutId}") to guard
+// against retries. flowName overrides the default flow; use "" for the default.
+func (c *OrderClient) CreateOrder(ctx context.Context, req CreateOrderReq, flowName string) (*CreateOrderResult, error) {
+	url := c.baseURL + "/api/orders/from-checkout"
+	if flowName != "" {
+		url += "?flow=" + flowName
+	}
+
+	body, err := json.Marshal(req)
+	if err != nil {
+		return nil, fmt.Errorf("order client: marshal: %w", err)
+	}
+
+	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
+	if err != nil {
+		return nil, fmt.Errorf("order client: new request: %w", err)
+	}
+	httpReq.Header.Set("Content-Type", "application/json")
+	httpReq.Header.Set("UCP-Agent", `profile="`+c.agentProfile+`"`)
+
+	resp, err := c.httpClient.Do(httpReq)
+	if err != nil {
+		return nil, fmt.Errorf("order client: do: %w", err)
+	}
+	defer resp.Body.Close()
+
+	// Both 201 (created) and 409 (idempotent hit) are valid responses.
+	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusConflict {
+		return nil, fmt.Errorf("order client: %s", resp.Status)
+	}
+
+	var result CreateOrderResult
+	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+		return nil, fmt.Errorf("order client: decode: %w", err)
+	}
+	result.Existing = resp.StatusCode == http.StatusConflict
+	return &result, nil
+}

cmd/checkout/order_create.go

@@ -0,0 +1,110 @@
+package main
+
+import (
+	"context"
+	"fmt"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/checkout"
+	messages "git.k6n.net/mats/go-cart-actor/proto/checkout"
+	"google.golang.org/protobuf/types/known/timestamppb"
+)
+
+// settledPayment carries the provider-agnostic facts about an already-settled
+// payment. Each payment integration (Klarna push, Adyen CAPTURE notification,
+// …) fills this in from its own callback and hands it to
+// createOrderFromSettledCheckout, so the from-checkout request is identical
+// regardless of which provider settled the payment.
+type settledPayment struct {
+	Provider  string // "klarna" | "adyen"
+	Reference string // processor / PSP reference
+	Amount    int64  // minor units, as charged
+	Currency  string
+	Country   string
+	Locale    string
+}
+
+// buildOrderLinesFromGrain converts the checkout grain's cart items and delivery
+// selections into from-checkout order lines. Shared by every provider so the
+// order payload is built the same way no matter who settled the payment.
+func buildOrderLinesFromGrain(grain *checkout.CheckoutGrain) []OrderLine {
+	lines := make([]OrderLine, 0, len(grain.CartState.Items)+len(grain.Deliveries))
+	for _, it := range grain.CartState.Items {
+		if it == nil {
+			continue
+		}
+		lines = append(lines, OrderLine{
+			Reference: it.Sku,
+			Sku:       it.Sku,
+			Name:      it.Meta.Name,
+			Quantity:  int32(it.Quantity),
+			UnitPrice: it.Price.IncVat,
+			TaxRate:   int32(it.Tax),
+		})
+	}
+	for _, d := range grain.Deliveries {
+		if d == nil || d.Price.IncVat <= 0 {
+			continue
+		}
+		lines = append(lines, OrderLine{
+			Reference: d.Provider,
+			Sku:       d.Provider,
+			Name:      "Delivery",
+			Quantity:  1,
+			UnitPrice: d.Price.IncVat,
+			TaxRate:   2500,
+		})
+	}
+	return lines
+}
+
+// createOrderFromSettledCheckout sends the from-checkout request for a settled
+// checkout (any provider) and, on success, records the returned order id on the
+// checkout grain via the OrderCreated mutation so the backoffice can link
+// checkout → order.
+//
+// It is idempotent: the order service dedupes on "checkout-{checkoutId}", so
+// repeated provider callbacks (Klarna re-push, retried Adyen CAPTURE) return the
+// existing order rather than creating a duplicate. Callers should treat a
+// non-nil error as non-fatal and retry on the next callback.
+func createOrderFromSettledCheckout(ctx context.Context, s *CheckoutPoolServer, grain *checkout.CheckoutGrain, pay settledPayment) (*CreateOrderResult, error) {
+	if grain.CartState == nil {
+		return nil, fmt.Errorf("from-checkout: checkout %s has no cart state", grain.Id)
+	}
+
+	var customerEmail, customerName string
+	if grain.ContactDetails != nil {
+		if grain.ContactDetails.Email != nil {
+			customerEmail = *grain.ContactDetails.Email
+		}
+		if grain.ContactDetails.Name != nil {
+			customerName = *grain.ContactDetails.Name
+		}
+	}
+
+	req := CreateOrderReq{
+		CheckoutId:     grain.Id.String(),
+		IdempotencyKey: "checkout-" + grain.Id.String(),
+		CartId:         grain.CartId.String(),
+		Currency:       pay.Currency,
+		Locale:         pay.Locale,
+		Country:        pay.Country,
+		CustomerEmail:  customerEmail,
+		CustomerName:   customerName,
+		Lines:          buildOrderLinesFromGrain(grain),
+	}
+	req.Payment.Provider = pay.Provider
+	req.Payment.Reference = pay.Reference
+	req.Payment.Amount = pay.Amount
+
+	result, err := s.orderClient.CreateOrder(ctx, req, "")
+	if err != nil {
+		return nil, err
+	}
+
+	_ = s.ApplyAnywhere(ctx, grain.Id, &messages.OrderCreated{
+		OrderId:   result.OrderId,
+		Status:    "completed",
+		CreatedAt: timestamppb.Now(),
+	})
+	return result, nil
+}

cmd/checkout/otel.go

@@ -0,0 +1,117 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc"
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/log/global"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/log"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/trace"
+)
+
+// setupOTelSDK bootstraps the OpenTelemetry pipeline.
+// If it does not return an error, make sure to call shutdown for proper cleanup.
+func setupOTelSDK(ctx context.Context) (func(context.Context) error, error) {
+	var shutdownFuncs []func(context.Context) error
+	var err error
+
+	// shutdown calls cleanup functions registered via shutdownFuncs.
+	// The errors from the calls are joined.
+	// Each registered cleanup will be invoked once.
+	shutdown := func(ctx context.Context) error {
+		var err error
+		for _, fn := range shutdownFuncs {
+			err = errors.Join(err, fn(ctx))
+		}
+		shutdownFuncs = nil
+		return err
+	}
+
+	// handleErr calls shutdown for cleanup and makes sure that all errors are returned.
+	handleErr := func(inErr error) {
+		err = errors.Join(inErr, shutdown(ctx))
+	}
+
+	// Set up propagator.
+	prop := newPropagator()
+	otel.SetTextMapPropagator(prop)
+
+	// Set up trace provider.
+	tracerProvider, err := newTracerProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
+	otel.SetTracerProvider(tracerProvider)
+
+	// Set up meter provider.
+	meterProvider, err := newMeterProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, meterProvider.Shutdown)
+	otel.SetMeterProvider(meterProvider)
+
+	// Set up logger provider.
+	loggerProvider, err := newLoggerProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, loggerProvider.Shutdown)
+	global.SetLoggerProvider(loggerProvider)
+
+	return shutdown, err
+}
+
+func newPropagator() propagation.TextMapPropagator {
+	return propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	)
+}
+
+func newTracerProvider() (*trace.TracerProvider, error) {
+	traceExporter, err := otlptracegrpc.New(context.Background())
+	if err != nil {
+		return nil, err
+	}
+
+	tracerProvider := trace.NewTracerProvider(
+		trace.WithBatcher(traceExporter,
+			// Default is 5s. Set to 1s for demonstrative purposes.
+			trace.WithBatchTimeout(time.Second)),
+	)
+	return tracerProvider, nil
+}
+
+func newMeterProvider() (*metric.MeterProvider, error) {
+	exporter, err := otlpmetricgrpc.New(context.Background())
+	if err != nil {
+		return nil, err
+	}
+
+	provider := metric.NewMeterProvider(metric.WithReader(metric.NewPeriodicReader(exporter)))
+	return provider, nil
+}
+
+func newLoggerProvider() (*log.LoggerProvider, error) {
+	logExporter, err := otlploggrpc.New(context.Background())
+	if err != nil {
+		return nil, err
+	}
+
+	loggerProvider := log.NewLoggerProvider(
+		log.WithProcessor(log.NewBatchProcessor(logExporter)),
+	)
+	return loggerProvider, nil
+}

cmd/checkout/pool-server.go

@@ -0,0 +1,549 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"os"
+	"strconv"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	"git.k6n.net/mats/go-cart-actor/pkg/checkout"
+	messages "git.k6n.net/mats/go-cart-actor/proto/checkout"
+
+	adyen "github.com/adyen/adyen-go-api-library/v21/src/adyen"
+	"git.k6n.net/mats/go-redis-inventory/pkg/inventory"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"go.opentelemetry.io/contrib/bridges/otelslog"
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/known/anypb"
+	"google.golang.org/protobuf/types/known/timestamppb"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/trace"
+)
+
+var (
+	grainMutations = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "checkout_grain_mutations_total",
+		Help: "The total number of mutations",
+	})
+	grainLookups = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "checkout_grain_lookups_total",
+		Help: "The total number of lookups",
+	})
+)
+
+type CheckoutPoolServer struct {
+	actor.GrainPool[checkout.CheckoutGrain]
+	pod_name         string
+	klarnaClient     *KlarnaClient
+	adyenClient      *adyen.APIClient
+	cartClient       *CartClient
+	orderClient      *OrderClient
+	orderHandler     *AmqpOrderHandler
+	inventoryService *inventory.RedisInventoryService
+}
+
+func NewCheckoutPoolServer(pool actor.GrainPool[checkout.CheckoutGrain], pod_name string, klarnaClient *KlarnaClient, cartClient *CartClient, adyenClient *adyen.APIClient, orderClient *OrderClient, orderHandler *AmqpOrderHandler) *CheckoutPoolServer {
+	srv := &CheckoutPoolServer{
+		GrainPool:    pool,
+		pod_name:     pod_name,
+		klarnaClient: klarnaClient,
+		cartClient:   cartClient,
+		adyenClient:  adyenClient,
+		orderClient:  orderClient,
+		orderHandler: orderHandler,
+	}
+
+	return srv
+}
+
+func (s *CheckoutPoolServer) ApplyLocal(ctx context.Context, id checkout.CheckoutId, mutation ...proto.Message) (*actor.MutationResult[checkout.CheckoutGrain], error) {
+	return s.Apply(ctx, uint64(id), mutation...)
+}
+
+func (s *CheckoutPoolServer) GetCheckoutHandler(w http.ResponseWriter, r *http.Request, id checkout.CheckoutId) error {
+	grain, err := s.Get(r.Context(), uint64(id))
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, grain)
+}
+
+func (s *CheckoutPoolServer) SetDeliveryHandler(w http.ResponseWriter, r *http.Request, id checkout.CheckoutId) error {
+	var msg messages.SetDelivery
+	if err := json.NewDecoder(r.Body).Decode(&msg); err != nil {
+		return err
+	}
+
+	result, err := s.ApplyLocal(r.Context(), id, &msg)
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, result)
+}
+
+func (s *CheckoutPoolServer) RemoveDeliveryHandler(w http.ResponseWriter, r *http.Request, id checkout.CheckoutId) error {
+	deliveryId := r.PathValue("id")
+	uintDeliveryId, err := strconv.ParseUint(deliveryId, 10, 64)
+	if err != nil {
+		return err
+	}
+	msg := &messages.RemoveDelivery{
+		Id: uint32(uintDeliveryId),
+	}
+
+	result, err := s.ApplyLocal(r.Context(), id, msg)
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, result)
+}
+
+func (s *CheckoutPoolServer) SetPickupPointHandler(w http.ResponseWriter, r *http.Request, id checkout.CheckoutId) error {
+	var msg messages.SetPickupPoint
+	if err := json.NewDecoder(r.Body).Decode(&msg); err != nil {
+		return err
+	}
+
+	result, err := s.ApplyLocal(r.Context(), id, &msg)
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, result)
+}
+
+func (s *CheckoutPoolServer) InitializeCheckoutHandler(w http.ResponseWriter, r *http.Request, id checkout.CheckoutId) error {
+	var msg messages.InitializeCheckout
+	if err := json.NewDecoder(r.Body).Decode(&msg); err != nil {
+		return err
+	}
+
+	result, err := s.ApplyLocal(r.Context(), id, &msg)
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, result)
+}
+
+func (s *CheckoutPoolServer) InventoryReservedHandler(w http.ResponseWriter, r *http.Request, id checkout.CheckoutId) error {
+	var msg messages.InventoryReserved
+	if err := json.NewDecoder(r.Body).Decode(&msg); err != nil {
+		return err
+	}
+
+	result, err := s.ApplyLocal(r.Context(), id, &msg)
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, result)
+}
+
+func (s *CheckoutPoolServer) OrderCreatedHandler(w http.ResponseWriter, r *http.Request, id checkout.CheckoutId) error {
+	var msg messages.OrderCreated
+	if err := json.NewDecoder(r.Body).Decode(&msg); err != nil {
+		return err
+	}
+
+	result, err := s.ApplyLocal(r.Context(), id, &msg)
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, result)
+}
+
+func (s *CheckoutPoolServer) ConfirmationViewedHandler(w http.ResponseWriter, r *http.Request, id checkout.CheckoutId) error {
+	var msg messages.ConfirmationViewed
+	if err := json.NewDecoder(r.Body).Decode(&msg); err != nil {
+		return err
+	}
+
+	result, err := s.ApplyLocal(r.Context(), id, &msg)
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, result)
+}
+
+func (s *CheckoutPoolServer) ContactDetailsUpdatedHandler(w http.ResponseWriter, r *http.Request, id checkout.CheckoutId) error {
+	var msg messages.ContactDetailsUpdated
+	if err := json.NewDecoder(r.Body).Decode(&msg); err != nil {
+		return err
+	}
+
+	result, err := s.ApplyLocal(r.Context(), id, &msg)
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, result)
+}
+
+func (s *CheckoutPoolServer) CancelPaymentHandler(w http.ResponseWriter, r *http.Request, checkoutId checkout.CheckoutId) error {
+	paymentId := r.PathValue("id")
+	result, err := s.ApplyLocal(r.Context(), checkoutId, &messages.CancelPayment{
+		PaymentId:   paymentId,
+		CancelledAt: timestamppb.New(time.Now()),
+	})
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, result)
+}
+
+func (s *CheckoutPoolServer) StartCheckoutHandler(w http.ResponseWriter, r *http.Request) {
+	cartIdStr := r.PathValue("cartid")
+	if cartIdStr == "" {
+		http.Error(w, "cart id required", http.StatusBadRequest)
+		return
+	}
+
+	cartId, ok := cart.ParseCartId(cartIdStr)
+	if !ok {
+		http.Error(w, "invalid cart id", http.StatusBadRequest)
+		return
+	}
+
+	// Fetch cart state from cart service
+	cartGrain, err := s.cartClient.getCartGrain(r.Context(), cartId)
+	if err != nil {
+		logger.Error("failed to fetch cart", "error", err, "cartId", cartId)
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	// Serialize cart state to Any
+	cartStateBytes, err := json.Marshal(cartGrain)
+	if err != nil {
+		logger.Error("failed to marshal cart state", "error", err)
+		http.Error(w, "failed to process cart state", http.StatusInternalServerError)
+		return
+	}
+
+	// The checkout grain is 1:1 with the cart it checks out (CheckoutId ==
+	// CartId). Keying it by the cart id — not a lingering checkoutid cookie —
+	// means a fresh cart always gets a fresh checkout, so the Klarna order
+	// reflects the cart shown at /kassa. Reusing the cookie made a new cart's
+	// checkout latch onto a previous cart's frozen snapshot (InitializeCheckout
+	// silently refuses to re-snapshot a grain that already has a CartState).
+	checkoutId := checkout.CheckoutId(cartId)
+
+	// Initialize checkout with cart state wrapped in Any
+	cartStateAny := &messages.InitializeCheckout{
+		OrderId: "",
+		CartId:  uint64(cartId),
+		Version: uint32(cartGrain.Version),
+		CartState: &anypb.Any{
+			TypeUrl: "type.googleapis.com/cart.CartGrain",
+			Value:   cartStateBytes,
+		},
+	}
+
+	result, err := s.ApplyLocal(r.Context(), checkoutId, cartStateAny)
+	if err != nil {
+		setCheckoutCookie(w, 0, r.TLS != nil)
+		logger.Error("failed to initialize checkout", "error", err)
+		http.Error(w, "failed to initialize checkout", http.StatusInternalServerError)
+		return
+	}
+
+	// Set checkout cookie
+	setCheckoutCookie(w, checkoutId, r.TLS != nil)
+
+	if err := s.WriteResult(w, &result.Result); err != nil {
+		logger.Error("failed to write result", "error", err)
+	}
+}
+
+func (s *CheckoutPoolServer) WriteResult(w http.ResponseWriter, result any) error {
+	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set("Cache-Control", "no-cache")
+	w.Header().Set("Access-Control-Allow-Origin", "*")
+	w.Header().Set("X-Pod-Name", s.pod_name)
+	if result == nil {
+
+		w.WriteHeader(http.StatusInternalServerError)
+
+		return nil
+	}
+	w.WriteHeader(http.StatusOK)
+	enc := json.NewEncoder(w)
+	err := enc.Encode(result)
+	return err
+}
+
+func (s *CheckoutPoolServer) CreateOrUpdateCheckout(r *http.Request, grain *checkout.CheckoutGrain, orderId *string) (*CheckoutOrder, error) {
+
+	meta := GetCheckoutMetaFromRequest(r)
+
+	payload, _, err := BuildCheckoutOrderPayload(grain, meta)
+	if err != nil {
+		return nil, err
+	}
+
+	var payment *checkout.Payment
+	if orderId != nil {
+		payment, _ = grain.FindPayment(*orderId)
+	}
+
+	if payment != nil && payment.PaymentId != "" {
+		return s.klarnaClient.UpdateOrder(r.Context(), payment.PaymentId, bytes.NewReader(payload))
+	} else {
+		return s.klarnaClient.CreateOrder(r.Context(), bytes.NewReader(payload))
+	}
+}
+
+func (s *CheckoutPoolServer) ApplyKlarnaPaymentStarted(ctx context.Context, klarnaOrder *CheckoutOrder, id checkout.CheckoutId) (*actor.MutationResult[checkout.CheckoutGrain], error) {
+	method := "checkout"
+	return s.ApplyLocal(ctx, id, &messages.PaymentStarted{
+		PaymentId: klarnaOrder.ID,
+		Amount:    int64(klarnaOrder.OrderAmount),
+		Currency:  klarnaOrder.PurchaseCurrency,
+		Provider:  "klarna",
+		Method:    &method,
+		StartedAt: timestamppb.New(time.Now()),
+	})
+}
+
+var (
+	tracer     = otel.Tracer(name)
+	hmacKey    = os.Getenv("ADYEN_HMAC")
+	meter      = otel.Meter(name)
+	logger     = otelslog.NewLogger(name)
+	proxyCalls metric.Int64Counter
+)
+
+func init() {
+	var err error
+	proxyCalls, err = meter.Int64Counter("proxy.calls",
+		metric.WithDescription("Number of proxy calls"),
+		metric.WithUnit("{calls}"))
+	if err != nil {
+		panic(err)
+	}
+}
+
+func (s *CheckoutPoolServer) GetAnywhere(ctx context.Context, checkoutId cart.CartId) (*checkout.CheckoutGrain, error) {
+	id := uint64(checkoutId)
+	if host, isOnOtherHost := s.OwnerHost(id); isOnOtherHost {
+		return host.Get(ctx, id)
+	}
+	return s.Get(ctx, id)
+}
+
+func (s *CheckoutPoolServer) ApplyAnywhere(ctx context.Context, checkoutId cart.CartId, msgs ...proto.Message) error {
+	id := uint64(checkoutId)
+	if host, isOnOtherHost := s.OwnerHost(id); isOnOtherHost {
+		_, err := host.Apply(ctx, id, msgs...)
+		return err
+	}
+	_, err := s.Apply(ctx, id, msgs...)
+	return err
+}
+
+type StartPayment struct {
+	Provider string `json:"provider"`
+	Method   string `json:"method,omitempty"`
+}
+
+func (s *CheckoutPoolServer) GetPaymentSessionHandler(w http.ResponseWriter, r *http.Request, checkoutId checkout.CheckoutId) error {
+	paymentId := r.PathValue("id")
+	grain, err := s.Get(r.Context(), uint64(checkoutId))
+	if err != nil {
+		return err
+	}
+	payment, ok := grain.FindPayment(paymentId)
+	if !ok {
+		http.Error(w, "payment not found", http.StatusNotFound)
+		return nil
+	}
+	switch payment.Provider {
+	case "adyen":
+		payload := &SessionRequest{
+			SessionResult: "",
+		}
+		if r.Method != http.MethodGet {
+			if err := json.NewDecoder(r.Body).Decode(payload); err != nil {
+				return err
+			}
+		}
+		service := s.adyenClient.Checkout()
+		req := service.PaymentsApi.GetResultOfPaymentSessionInput(paymentId).SessionResult(payload.SessionResult)
+
+		res, _, err := service.PaymentsApi.GetResultOfPaymentSession(r.Context(), req)
+		if err != nil {
+			return err
+		}
+		if res.Status != nil && *res.Status == "completed" {
+			_, err := s.ApplyLocal(r.Context(), checkoutId, &messages.PaymentCompleted{
+				PaymentId:          paymentId,
+				Status:             *res.Status,
+				ProcessorReference: res.Id,
+				CompletedAt:        timestamppb.Now(),
+			})
+			if err != nil {
+				logger.Error("unable to apply payment started mutation", "error", err)
+				return err
+			}
+		}
+
+		return s.WriteResult(w, res)
+	case "klarna":
+		current, err := s.klarnaClient.GetOrder(r.Context(), paymentId)
+		if err != nil {
+			return err
+
+		}
+		return s.WriteResult(w, current)
+	}
+
+	return errors.New("unsupported payment provider")
+}
+
+func (s *CheckoutPoolServer) StartPaymentHandler(w http.ResponseWriter, r *http.Request, checkoutId checkout.CheckoutId) error {
+	grain, err := s.Get(r.Context(), uint64(checkoutId))
+	if err != nil {
+		return err
+	}
+	payload := &StartPayment{}
+	if err := json.NewDecoder(r.Body).Decode(payload); err != nil {
+		return err
+	}
+	switch payload.Provider {
+	case "adyen":
+		meta := GetCheckoutMetaFromRequest(r)
+		sessionData, err := BuildAdyenCheckoutSession(grain, meta)
+		if err != nil {
+			logger.Error("unable to build adyen session", "error", err)
+			return err
+		}
+		service := s.adyenClient.Checkout()
+		req := service.PaymentsApi.SessionsInput().CreateCheckoutSessionRequest(*sessionData)
+		session, _, err := service.PaymentsApi.Sessions(r.Context(), req)
+		if err != nil {
+			logger.Error("unable to create adyen session", "error", err)
+			return err
+		}
+		sessionBytes, err := json.Marshal(session)
+		if err != nil {
+			logger.Error("unable to marshal session", "error", err)
+			return err
+		}
+		// Apply PaymentStarted mutation
+		result, err := s.ApplyLocal(r.Context(), checkoutId, &messages.PaymentStarted{
+			PaymentId: session.Id,
+			Amount:    session.Amount.Value,
+			Currency:  session.Amount.Currency,
+			Provider:  "adyen",
+			SessionData: &anypb.Any{
+				TypeUrl: "type.googleapis.com/google.protobuf.StringValue",
+				Value:   sessionBytes,
+			},
+			Method:    &payload.Method,
+			StartedAt: timestamppb.New(time.Now()),
+		})
+		if err != nil {
+			logger.Error("unable to apply payment started mutation", "error", err)
+			return err
+		}
+
+		return s.WriteResult(w, result)
+
+	case "klarna":
+		order, err := s.CreateOrUpdateCheckout(r, grain, nil)
+		if err != nil {
+			logger.Error("unable to create klarna session", "error", err)
+			return err
+		}
+		orderBytes, err := json.Marshal(order)
+		if err != nil {
+			logger.Error("unable to marshal order", "error", err)
+			return err
+		}
+		result, err := s.ApplyLocal(r.Context(), checkoutId, &messages.PaymentStarted{
+			PaymentId: order.ID,
+			Amount:    int64(order.OrderAmount),
+			Currency:  order.PurchaseCurrency,
+			Provider:  "klarna",
+			Method:    &payload.Method,
+			SessionData: &anypb.Any{
+				TypeUrl: "type.googleapis.com/google.protobuf.StringValue",
+				Value:   orderBytes,
+			},
+			StartedAt: timestamppb.New(time.Now()),
+		})
+		if err != nil {
+			logger.Error("unable to apply payment started mutation", "error", err)
+			return err
+		}
+
+		return s.WriteResult(w, result)
+
+	default:
+		http.Error(w, "unsupported payment provider", http.StatusBadRequest)
+		return nil
+	}
+}
+
+func (s *CheckoutPoolServer) Serve(mux *http.ServeMux) {
+	handleFunc := func(pattern string, handlerFunc func(http.ResponseWriter, *http.Request)) {
+		attr := attribute.String("http.route", pattern)
+		mux.HandleFunc(pattern, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			span := trace.SpanFromContext(r.Context())
+			span.SetName(pattern)
+			span.SetAttributes(attr)
+
+			labeler, _ := otelhttp.LabelerFromContext(r.Context())
+			labeler.Add(attr)
+
+			handlerFunc(w, r)
+		}))
+	}
+	//handleFunc("/payment/adyen/session", CookieCheckoutIdHandler(s.AdyenSessionHandler))
+	handleFunc("/payment/adyen/push", s.AdyenHookHandler)
+	handleFunc("/payment/adyen/return", s.AdyenReturnHandler)
+	//handleFunc("/payment/adyen/cancel", s.AdyenCancelHandler)
+
+	handleFunc("/payment/klarna/validate", s.KlarnaValidationHandler)
+	handleFunc("/payment/klarna/push", s.KlarnaPushHandler)
+	handleFunc("/payment/klarna/notification", s.KlarnaNotificationHandler)
+
+	handleFunc("POST /api/checkout/start/{cartid}", s.StartCheckoutHandler)
+	handleFunc("GET /api/checkout", CookieCheckoutIdHandler(s.ProxyHandler(s.GetCheckoutHandler)))
+	handleFunc("POST /api/checkout/delivery", CookieCheckoutIdHandler(s.ProxyHandler(s.SetDeliveryHandler)))
+	handleFunc("DELETE /api/checkout/delivery/{id}", CookieCheckoutIdHandler(s.ProxyHandler(s.RemoveDeliveryHandler)))
+	handleFunc("POST /api/checkout/pickup-point", CookieCheckoutIdHandler(s.ProxyHandler(s.SetPickupPointHandler)))
+	handleFunc("POST /api/checkout/contact-details", CookieCheckoutIdHandler(s.ProxyHandler(s.ContactDetailsUpdatedHandler)))
+	handleFunc("POST /payment", CookieCheckoutIdHandler(s.ProxyHandler(s.StartPaymentHandler)))
+	handleFunc("POST /payment/{id}/session", CookieCheckoutIdHandler(s.ProxyHandler(s.GetPaymentSessionHandler)))
+	handleFunc("DELETE /payment/{id}", CookieCheckoutIdHandler(s.ProxyHandler(s.CancelPaymentHandler)))
+	// handleFunc("POST /api/checkout/initialize", CookieCheckoutIdHandler(s.ProxyHandler(s.InitializeCheckoutHandler)))
+	// handleFunc("POST /api/checkout/inventory-reserved", CookieCheckoutIdHandler(s.ProxyHandler(s.InventoryReservedHandler)))
+	// handleFunc("POST /api/checkout/order-created", CookieCheckoutIdHandler(s.ProxyHandler(s.OrderCreatedHandler)))
+	// handleFunc("POST /api/checkout/confirmation-viewed", CookieCheckoutIdHandler(s.ProxyHandler(s.ConfirmationViewedHandler)))
+
+	//handleFunc("GET /payment/klarna/session", CookieCheckoutIdHandler(s.ProxyHandler(s.KlarnaSessionHandler)))
+	//handleFunc("GET /payment/klarna/checkout", CookieCheckoutIdHandler(s.ProxyHandler(s.KlarnaHtmlCheckoutHandler)))
+
+	handleFunc("GET /payment/klarna/confirmation/{order_id}", s.KlarnaConfirmationHandler)
+
+}

cmd/checkout/utils.go

@@ -0,0 +1,167 @@
+package main
+
+import (
+	"context"
+	"log"
+	"net/http"
+	"strings"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	"git.k6n.net/mats/go-cart-actor/pkg/checkout"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+)
+
+func getOriginalHost(r *http.Request) string {
+	proxyHost := r.Header.Get("X-Forwarded-Host")
+	if proxyHost != "" {
+		return proxyHost
+	}
+	return r.Host
+}
+
+// getScheme resolves the public scheme for building absolute URLs (e.g. Klarna
+// merchant_urls). Honors X-Forwarded-Proto set by the edge/dev proxy; defaults
+// to https so production (TLS terminated at nginx/ingress, no header) is correct.
+func getScheme(r *http.Request) string {
+	if proto := r.Header.Get("X-Forwarded-Proto"); proto != "" {
+		return proto
+	}
+	if r.TLS != nil {
+		return "https"
+	}
+	return "https"
+}
+
+func getClientIp(r *http.Request) string {
+	ip := r.Header.Get("X-Forwarded-For")
+	if ip == "" {
+		ip = r.RemoteAddr
+	}
+	return ip
+}
+
+func getCurrency(country string) string {
+	if country == "no" {
+		return "NOK"
+	}
+	return "SEK"
+}
+
+func getLocale(country string) string {
+	if country == "no" {
+		return "nb-no"
+	}
+	return "sv-se"
+}
+
+// getCountryFromCurrency is the reverse of getCurrency, used by server-to-server
+// callbacks (e.g. the Adyen webhook) that carry the settled currency but not the
+// shopper's host/country.
+func getCountryFromCurrency(currency string) string {
+	if strings.EqualFold(currency, "NOK") {
+		return "no"
+	}
+	return "se"
+}
+
+func getCountryFromHost(host string) string {
+	if strings.Contains(strings.ToLower(host), "-no") {
+		return "no"
+	}
+	if strings.Contains(strings.ToLower(host), "-se") {
+		return "se"
+	}
+	return ""
+}
+
+func (a *CheckoutPoolServer) reserveInventory(ctx context.Context, grain *checkout.CheckoutGrain) error {
+	if a.inventoryService != nil {
+		inventoryRequests := getInventoryRequests(grain.CartState.Items)
+		_, err := a.inventoryService.ReservationCheck(ctx, inventoryRequests...)
+		if err != nil {
+			logger.WarnContext(ctx, "placeorder inventory check failed")
+			return err
+		}
+	}
+	return nil
+}
+
+const checkoutCookieName = "checkoutid"
+
+func setCheckoutCookie(w http.ResponseWriter, checkoutId checkout.CheckoutId, tls bool) {
+	if checkoutId == 0 {
+		http.SetCookie(w, &http.Cookie{
+			Name:     checkoutCookieName,
+			Value:    checkoutId.String(),
+			Secure:   tls,
+			HttpOnly: true,
+			Path:     "/",
+			Expires:  time.Unix(0, 0),
+			SameSite: http.SameSiteLaxMode,
+		})
+	} else {
+		http.SetCookie(w, &http.Cookie{
+			Name:     checkoutCookieName,
+			Value:    checkoutId.String(),
+			Secure:   tls,
+			HttpOnly: true,
+			Path:     "/",
+			Expires:  time.Now().AddDate(0, 0, 14),
+			SameSite: http.SameSiteLaxMode,
+		})
+	}
+}
+
+func CookieCheckoutIdHandler(fn func(w http.ResponseWriter, r *http.Request, checkoutId checkout.CheckoutId) error) func(w http.ResponseWriter, r *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+
+		var id checkout.CheckoutId
+		cookie, err := r.Cookie(checkoutCookieName)
+		if err != nil || cookie.Value == "" {
+			w.WriteHeader(http.StatusNotAcceptable)
+			return
+		} else {
+			parsed, ok := cart.ParseCartId(cookie.Value)
+			if !ok {
+				w.WriteHeader(http.StatusNotAcceptable)
+				return
+			} else {
+				id = parsed
+			}
+		}
+
+		err = fn(w, r, id)
+		if err != nil {
+			log.Printf("Server error, not remote error: %v\n", err)
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte(err.Error()))
+		}
+
+	}
+}
+
+func (s *CheckoutPoolServer) ProxyHandler(fn func(w http.ResponseWriter, r *http.Request, checkoutId checkout.CheckoutId) error) func(w http.ResponseWriter, r *http.Request, checkoutId checkout.CheckoutId) error {
+	return func(w http.ResponseWriter, r *http.Request, checkoutId checkout.CheckoutId) error {
+		if ownerHost, ok := s.OwnerHost(uint64(checkoutId)); ok {
+			ctx, span := tracer.Start(r.Context(), "proxy")
+			defer span.End()
+			span.SetAttributes(attribute.String("checkoutid", checkoutId.String()))
+			hostAttr := attribute.String("other host", ownerHost.Name())
+			span.SetAttributes(hostAttr)
+			logger.InfoContext(ctx, "checkout proxyed", "result", ownerHost.Name())
+			proxyCalls.Add(ctx, 1, metric.WithAttributes(hostAttr))
+			handled, err := ownerHost.Proxy(uint64(checkoutId), w, r, nil)
+
+			grainLookups.Inc()
+			if err == nil && handled {
+				return nil
+			}
+		}
+		_, span := tracer.Start(r.Context(), "own")
+		span.SetAttributes(attribute.String("checkoutid", checkoutId.String()))
+		defer span.End()
+		return fn(w, r, checkoutId)
+	}
+}

cmd/inventory/main.go

@@ -0,0 +1,152 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"log"
+	"net/http"
+	"os"
+	"sync"
+
+	"git.k6n.net/mats/go-redis-inventory/pkg/inventory"
+	"git.k6n.net/mats/slask-finder/pkg/index"
+	"git.k6n.net/mats/slask-finder/pkg/messaging"
+	"github.com/redis/go-redis/v9"
+	"github.com/redis/go-redis/v9/maintnotifications"
+
+	amqp "github.com/rabbitmq/amqp091-go"
+)
+
+type Server struct {
+	inventoryService   *inventory.RedisInventoryService
+	reservationService *inventory.RedisCartReservationService
+}
+
+func (srv *Server) livezHandler(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte("OK"))
+}
+
+func (srv *Server) readyzHandler(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte("OK"))
+}
+
+func (srv *Server) getInventoryHandler(w http.ResponseWriter, r *http.Request) {
+
+	sku := inventory.SKU(r.PathValue("sku"))
+	locationID := inventory.LocationID(r.PathValue("locationId"))
+
+	quantity, err := srv.inventoryService.GetInventory(r.Context(), sku, locationID)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	response := map[string]int64{"quantity": quantity}
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(response)
+}
+
+func (srv *Server) getReservationHandler(w http.ResponseWriter, r *http.Request) {
+	sku := inventory.SKU(r.PathValue("sku"))
+	locationID := inventory.LocationID(r.PathValue("locationId"))
+
+	summary, err := srv.reservationService.GetReservationSummary(r.Context(), sku, locationID)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(summary)
+}
+
+var country = "se"
+var redisAddress = "10.10.3.18:6379"
+var redisPassword = "slaskredis"
+
+func init() {
+	// Override redis config from environment variables if set
+	if addr, ok := os.LookupEnv("REDIS_ADDRESS"); ok {
+		redisAddress = addr
+	}
+	if password, ok := os.LookupEnv("REDIS_PASSWORD"); ok {
+		redisPassword = password
+	}
+	if ctry, ok := os.LookupEnv("COUNTRY"); ok {
+		country = ctry
+	}
+}
+
+func main() {
+	var ctx = context.Background()
+	rdb := redis.NewClient(&redis.Options{
+		Addr:     redisAddress,
+		Password: redisPassword, // no password set
+		DB:       0,             // use default DB
+		MaintNotificationsConfig: &maintnotifications.Config{
+			Mode: maintnotifications.ModeDisabled,
+		},
+	})
+	s, err := inventory.NewRedisInventoryService(rdb)
+	if err != nil {
+		log.Fatalf("Unable to connect to inventory redis: %v", err)
+		return
+	}
+
+	r, err := inventory.NewRedisCartReservationService(rdb)
+	if err != nil {
+		log.Fatalf("Unable to connect to reservation redis: %v", err)
+		return
+	}
+
+	server := &Server{inventoryService: s, reservationService: r}
+
+	// Set up HTTP routes
+	http.HandleFunc("/livez", server.livezHandler)
+	http.HandleFunc("/readyz", server.readyzHandler)
+	http.HandleFunc("/inventory/{sku}/{locationId}", server.getInventoryHandler)
+	http.HandleFunc("/reservations/{sku}/{locationId}", server.getReservationHandler)
+
+	stockhandler := &StockHandler{
+		MainStockLocationID: inventory.LocationID(country),
+		rdb:                 rdb,
+		ctx:                 ctx,
+		svc:                 *s,
+	}
+
+	amqpUrl, ok := os.LookupEnv("RABBIT_HOST")
+	if ok {
+		log.Printf("Connecting to rabbitmq")
+		conn, err := amqp.DialConfig(amqpUrl, amqp.Config{
+			Properties: amqp.NewConnectionProperties(),
+		})
+		//a.conn = conn
+		if err != nil {
+			log.Fatalf("Failed to connect to RabbitMQ: %v", err)
+		}
+		ch, err := conn.Channel()
+		if err != nil {
+			log.Fatalf("Failed to open a channel: %v", err)
+		}
+		// items listener
+		err = messaging.ListenToTopic(ch, country, "item_added", func(d amqp.Delivery) error {
+			wg := &sync.WaitGroup{}
+			err = index.ForEachRawDataItemInJSONArray(d.Body, func(item *index.RawDataItem) error {
+				stockhandler.HandleItem(item, wg)
+				wg.Wait()
+				log.Print("Batch done...")
+				return err
+			})
+			return nil
+		})
+		if err != nil {
+			log.Fatalf("Failed to listen to item_added topic: %v", err)
+		}
+	}
+
+	// Start HTTP server
+	log.Println("Starting HTTP server on :8080")
+	log.Fatal(http.ListenAndServe(":8080", nil))
+}

cmd/inventory/stockhandler.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"context"
+	"log"
+	"sync"
+
+	"git.k6n.net/mats/go-redis-inventory/pkg/inventory"
+	"git.k6n.net/mats/slask-finder/pkg/types"
+	"github.com/redis/go-redis/v9"
+)
+
+type StockHandler struct {
+	rdb                 *redis.Client
+	ctx                 context.Context
+	svc                 inventory.RedisInventoryService
+	MainStockLocationID inventory.LocationID
+}
+
+func (s *StockHandler) HandleItem(item types.Item, wg *sync.WaitGroup) {
+	wg.Go(func() {
+		ctx := s.ctx
+		pipe := s.rdb.Pipeline()
+		centralStock, ok := item.GetNumberFieldValue("inStock")
+		if !ok {
+			centralStock = 0
+		}
+
+		sku, ok := item.GetStringFieldValue("sku")
+		if !ok {
+			log.Printf("unable to parse central stock for item %s: %v", sku)
+			centralStock = 0
+		} else {
+			s.svc.UpdateInventory(ctx, pipe, inventory.SKU(sku), s.MainStockLocationID, int64(centralStock))
+		}
+		// for id, value := range item.GetStock() {
+		// 	s.svc.UpdateInventory(ctx, pipe, inventory.SKU(sku), inventory.LocationID(id), int64(value))
+		// }
+		_, err := pipe.Exec(ctx)
+		if err != nil {
+			log.Printf("unable to update stock: %v", err)
+		}
+	})
+}

cmd/order/amqp.go

@@ -0,0 +1,223 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"hash/fnv"
+	"log/slog"
+	"sync"
+	"time"
+
+	messages "git.k6n.net/mats/go-cart-actor/proto/order"
+
+	amqp "github.com/rabbitmq/amqp091-go"
+)
+
+// rabbitPublisher is the broker-delivery side used by the outbox relay. It dials
+// lazily and reconnects on failure, so the relay can be started even when the
+// broker is down at boot: messages accumulate durably in the outbox and drain
+// once the broker is reachable.
+type rabbitPublisher struct {
+	url  string
+	mu   sync.Mutex
+	conn *amqp.Connection
+	ch   *amqp.Channel
+}
+
+func newRabbitPublisher(url string) *rabbitPublisher {
+	return &rabbitPublisher{url: url}
+}
+
+func (p *rabbitPublisher) connect() error {
+	conn, err := amqp.Dial(p.url)
+	if err != nil {
+		return err
+	}
+	ch, err := conn.Channel()
+	if err != nil {
+		_ = conn.Close()
+		return err
+	}
+	p.conn, p.ch = conn, ch
+	return nil
+}
+
+func (p *rabbitPublisher) reset() {
+	if p.ch != nil {
+		_ = p.ch.Close()
+	}
+	if p.conn != nil {
+		_ = p.conn.Close()
+	}
+	p.ch, p.conn = nil, nil
+}
+
+func (p *rabbitPublisher) Publish(exchange, routingKey string, body []byte) error {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if p.ch == nil {
+		if err := p.connect(); err != nil {
+			return err
+		}
+	}
+	// Bound the publish so a half-open/black-holed connection can't wedge the
+	// outbox relay indefinitely; on timeout the error path resets and the relay
+	// retries on its next tick.
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	err := p.ch.PublishWithContext(ctx, exchange, routingKey, false, false,
+		amqp.Publishing{ContentType: "application/json", Body: body})
+	if err != nil {
+		p.reset() // force a reconnect on the next attempt
+	}
+	return err
+}
+
+// This ingester lets the order service supersede the legacy go-order-manager:
+// it consumes the same "order-queue" the Klarna/Adyen checkout publishes to and
+// records each completed order as an event-sourced grain. Those orders are
+// already paid by the external processor, so we record payment with provider
+// "legacy" (place -> authorize -> capture) rather than charging again.
+
+// legacyOrder is the subset of go-order-manager's Order JSON we need.
+type legacyOrder struct {
+	ID               string        `json:"order_id"`
+	PurchaseCountry  string        `json:"purchase_country"`
+	PurchaseCurrency string        `json:"purchase_currency"`
+	Locale           string        `json:"locale"`
+	OrderAmount      int64         `json:"order_amount"`
+	OrderTaxAmount   int64         `json:"order_tax_amount"`
+	OrderLines       []legacyLine  `json:"order_lines"`
+	Customer         *legacyPerson `json:"customer,omitempty"`
+	BillingAddress   *legacyAddr   `json:"billing_address,omitempty"`
+}
+
+type legacyLine struct {
+	Reference      string `json:"reference"`
+	Name           string `json:"name"`
+	Quantity       int32  `json:"quantity"`
+	UnitPrice      int64  `json:"unit_price"`
+	TaxRate        int32  `json:"tax_rate"`
+	TotalAmount    int64  `json:"total_amount"`
+	TotalTaxAmount int64  `json:"total_tax_amount"`
+}
+
+type legacyPerson struct {
+	Email string `json:"email,omitempty"`
+}
+type legacyAddr struct {
+	Email      string `json:"email,omitempty"`
+	GivenName  string `json:"given_name,omitempty"`
+	FamilyName string `json:"family_name,omitempty"`
+}
+
+// legacyOrderID maps a legacy string order id to a stable grain id, so a
+// redelivered message resolves to the same grain (PlaceOrder then no-ops).
+func legacyOrderID(ref string) uint64 {
+	h := fnv.New64a()
+	_, _ = h.Write([]byte(ref))
+	id := h.Sum64()
+	if id == 0 {
+		id = 1
+	}
+	return id
+}
+
+// ingestLegacyOrder records one legacy order as an event-sourced grain. It is
+// idempotent: if the order is already placed, PlaceOrder is rejected and we
+// stop (the order already exists). Testable without a broker.
+func ingestLegacyOrder(ctx context.Context, app *orderedApplier, body []byte) error {
+	var lo legacyOrder
+	if err := json.Unmarshal(body, &lo); err != nil {
+		return err
+	}
+	if lo.ID == "" || len(lo.OrderLines) == 0 {
+		return nil // nothing actionable
+	}
+	id := legacyOrderID(lo.ID)
+	ms := time.Now().UnixMilli()
+
+	po := &messages.PlaceOrder{
+		OrderReference: lo.ID,
+		Currency:       lo.PurchaseCurrency,
+		Locale:         lo.Locale,
+		Country:        lo.PurchaseCountry,
+		TotalAmount:    lo.OrderAmount,
+		TotalTax:       lo.OrderTaxAmount,
+		PlacedAtMs:     ms,
+	}
+	if lo.Customer != nil {
+		po.CustomerEmail = lo.Customer.Email
+	}
+	if po.CustomerEmail == "" && lo.BillingAddress != nil {
+		po.CustomerEmail = lo.BillingAddress.Email
+		po.CustomerName = lo.BillingAddress.GivenName + " " + lo.BillingAddress.FamilyName
+	}
+	for _, l := range lo.OrderLines {
+		po.Lines = append(po.Lines, &messages.OrderLine{
+			Reference: l.Reference, Sku: l.Reference, Name: l.Name,
+			Quantity: l.Quantity, UnitPrice: l.UnitPrice, TaxRate: l.TaxRate,
+			TotalAmount: l.TotalAmount, TotalTax: l.TotalTaxAmount,
+		})
+	}
+
+	if err := applyOne(ctx, app, id, po); err != nil {
+		// Already placed (redelivery) or invalid — nothing more to do.
+		return nil
+	}
+	// Record the externally-settled payment so the grain reaches "captured".
+	ref := "legacy-" + lo.ID
+	_ = applyOne(ctx, app, id, &messages.AuthorizePayment{Provider: "legacy", Amount: lo.OrderAmount, Reference: ref, AtMs: ms})
+	_ = applyOne(ctx, app, id, &messages.CapturePayment{Provider: "legacy", Amount: lo.OrderAmount, Reference: ref, AtMs: ms})
+	return nil
+}
+
+// startLegacyIngest connects to AMQP and consumes "order-queue" until ctx is
+// done. Best-effort: a connection failure is logged and ingestion is skipped
+// (the HTTP checkout path keeps working regardless).
+func startLegacyIngest(ctx context.Context, amqpURL string, app *orderedApplier, logger *slog.Logger) {
+	conn, err := amqp.Dial(amqpURL)
+	if err != nil {
+		logger.Warn("legacy order ingest disabled: amqp dial failed", "err", err)
+		return
+	}
+	ch, err := conn.Channel()
+	if err != nil {
+		logger.Warn("legacy order ingest disabled: channel failed", "err", err)
+		_ = conn.Close()
+		return
+	}
+	q, err := ch.QueueDeclare("order-queue", false, false, false, false, nil)
+	if err != nil {
+		logger.Warn("legacy order ingest disabled: queue declare failed", "err", err)
+		_ = ch.Close()
+		_ = conn.Close()
+		return
+	}
+	msgs, err := ch.Consume(q.Name, "order-service", true, false, false, false, nil)
+	if err != nil {
+		logger.Warn("legacy order ingest disabled: consume failed", "err", err)
+		_ = ch.Close()
+		_ = conn.Close()
+		return
+	}
+	logger.Info("ingesting legacy orders from order-queue")
+	go func() {
+		defer conn.Close()
+		defer ch.Close()
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case d, ok := <-msgs:
+				if !ok {
+					logger.Warn("legacy order ingest: channel closed")
+					return
+				}
+				if err := ingestLegacyOrder(ctx, app, d.Body); err != nil {
+					logger.Error("legacy order ingest failed", "err", err)
+				}
+			}
+		}
+	}()
+}

cmd/order/amqp_test.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"testing"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/order"
+)
+
+func testApplier(t *testing.T) *orderedApplier {
+	t.Helper()
+	reg := actor.NewMutationRegistry()
+	order.RegisterMutations(reg)
+	storage := actor.NewDiskStorage[order.OrderGrain](t.TempDir(), reg)
+	pool, err := actor.NewSimpleGrainPool(actor.GrainPoolConfig[order.OrderGrain]{
+		Hostname: "test",
+		Spawn: func(_ context.Context, id uint64) (actor.Grain[order.OrderGrain], error) {
+			return order.NewOrderGrain(id, time.Now()), nil
+		},
+		SpawnHost: func(string) (actor.Host[order.OrderGrain], error) { return nil, fmt.Errorf("none") },
+		Destroy:   func(actor.Grain[order.OrderGrain]) error { return nil },
+		TTL:       time.Hour,
+		PoolSize:  100,
+
+		MutationRegistry: reg,
+		Storage:          nil,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(pool.Close)
+	return &orderedApplier{pool: pool, storage: storage}
+}
+
+func TestIngestLegacyOrder(t *testing.T) {
+	app := testApplier(t)
+	ctx := context.Background()
+	body := []byte(`{
+		"order_id":"K-1","purchase_currency":"SEK","purchase_country":"se","locale":"sv-SE",
+		"order_amount":15000,"order_tax_amount":3000,
+		"order_lines":[{"reference":"l1","name":"Widget","quantity":1,"unit_price":15000,"tax_rate":25,"total_amount":15000,"total_tax_amount":3000}]
+	}`)
+
+	if err := ingestLegacyOrder(ctx, app, body); err != nil {
+		t.Fatalf("ingest: %v", err)
+	}
+	id := legacyOrderID("K-1")
+	g, err := app.Get(ctx, id)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if g.Status != order.StatusCaptured {
+		t.Fatalf("status = %q, want captured", g.Status)
+	}
+	if g.CapturedAmount != 15000 {
+		t.Fatalf("captured = %d, want 15000", g.CapturedAmount)
+	}
+
+	// Redelivery must be idempotent — no double capture, no new payment.
+	if err := ingestLegacyOrder(ctx, app, body); err != nil {
+		t.Fatalf("re-ingest: %v", err)
+	}
+	g2, _ := app.Get(ctx, id)
+	if g2.CapturedAmount != 15000 {
+		t.Fatalf("redelivery double-captured: %d", g2.CapturedAmount)
+	}
+	if len(g2.Payments) != 1 {
+		t.Fatalf("redelivery created %d payments, want 1", len(g2.Payments))
+	}
+}

cmd/order/flows.go

@@ -0,0 +1,111 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/flow"
+)
+
+// flowStore holds the saga/flow definitions the service can run. Definitions
+// are JSON files in a directory (editable by the backoffice saga editor),
+// overlaid on a set of built-in seeds so a fresh deployment always has the
+// defaults. Saving validates against the engine before writing.
+type flowStore struct {
+	mu     sync.RWMutex
+	dir    string
+	engine *flow.Engine
+	defs   map[string]*flow.Definition
+}
+
+var validFlowName = func(s string) bool {
+	if s == "" || len(s) > 64 {
+		return false
+	}
+	for _, r := range s {
+		if !(r == '-' || r == '_' || (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9')) {
+			return false
+		}
+	}
+	return true
+}
+
+// newFlowStore seeds with the built-in definitions, then overlays any JSON files
+// found in dir (on-disk wins, so edits persist and take effect).
+func newFlowStore(dir string, engine *flow.Engine, seed map[string]*flow.Definition) (*flowStore, error) {
+	s := &flowStore{dir: dir, engine: engine, defs: map[string]*flow.Definition{}}
+	for name, def := range seed {
+		s.defs[name] = def
+	}
+	matches, _ := filepath.Glob(filepath.Join(dir, "*.json"))
+	for _, m := range matches {
+		data, err := os.ReadFile(m)
+		if err != nil {
+			return nil, fmt.Errorf("read flow %s: %w", m, err)
+		}
+		def, err := flow.Parse(data)
+		if err != nil {
+			return nil, fmt.Errorf("parse flow %s: %w", m, err)
+		}
+		if def.Name == "" {
+			def.Name = strings.TrimSuffix(filepath.Base(m), ".json")
+		}
+		s.defs[def.Name] = def
+	}
+	return s, nil
+}
+
+func (s *flowStore) get(name string) (*flow.Definition, bool) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	d, ok := s.defs[name]
+	return d, ok
+}
+
+func (s *flowStore) list() []*flow.Definition {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	names := make([]string, 0, len(s.defs))
+	for n := range s.defs {
+		names = append(names, n)
+	}
+	sort.Strings(names)
+	out := make([]*flow.Definition, 0, len(names))
+	for _, n := range names {
+		out = append(out, s.defs[n])
+	}
+	return out
+}
+
+// save validates the definition, persists it to <dir>/<name>.json and updates
+// the in-memory map so the next checkout uses it.
+func (s *flowStore) save(name string, def *flow.Definition) error {
+	if !validFlowName(name) {
+		return fmt.Errorf("invalid flow name %q", name)
+	}
+	if def.Name == "" {
+		def.Name = name
+	}
+	if err := s.engine.Validate(def); err != nil {
+		return err
+	}
+	data, err := json.MarshalIndent(def, "", "  ")
+	if err != nil {
+		return err
+	}
+	if err := os.MkdirAll(s.dir, 0o755); err != nil {
+		return err
+	}
+	if err := os.WriteFile(filepath.Join(s.dir, name+".json"), append(data, '\n'), 0o644); err != nil {
+		return err
+	}
+	s.mu.Lock()
+	s.defs[name] = def
+	s.mu.Unlock()
+	return nil
+}

cmd/order/handlers.go

@@ -0,0 +1,231 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/flow"
+	"git.k6n.net/mats/go-cart-actor/pkg/order"
+	messages "git.k6n.net/mats/go-cart-actor/proto/order"
+
+	"google.golang.org/protobuf/proto"
+)
+
+func nowMs() int64 { return time.Now().UnixMilli() }
+
+// applyOne applies a single mutation and surfaces the handler error (the pool
+// returns a top-level error only for unregistered mutations; a rejected
+// transition is carried per-mutation in the result).
+func applyOne(ctx context.Context, app *orderedApplier, id uint64, msg proto.Message) error {
+	res, err := app.Apply(ctx, id, msg)
+	if err != nil {
+		return err
+	}
+	if res != nil {
+		for _, m := range res.Mutations {
+			if m.Error != nil {
+				return m.Error
+			}
+		}
+	}
+	return nil
+}
+
+// capturedRef returns the capture reference of the first captured payment, which
+// the payment provider needs to issue a refund against.
+func capturedRef(g *order.OrderGrain) string {
+	for _, p := range g.Payments {
+		if p.Captured > 0 && p.CaptureRef != "" {
+			return p.CaptureRef
+		}
+	}
+	return ""
+}
+
+// loadOrder parses the id and returns the current grain, writing 400/404 itself
+// and returning ok=false when the caller should stop.
+func (s *server) loadOrder(w http.ResponseWriter, r *http.Request) (order.OrderId, *order.OrderGrain, bool) {
+	id, ok := order.ParseOrderId(r.PathValue("id"))
+	if !ok {
+		writeErr(w, http.StatusBadRequest, fmt.Errorf("invalid order id"))
+		return 0, nil, false
+	}
+	g, err := s.applier.Get(r.Context(), uint64(id))
+	if err != nil {
+		writeErr(w, http.StatusInternalServerError, err)
+		return 0, nil, false
+	}
+	if g.Status == order.StatusNew {
+		writeErr(w, http.StatusNotFound, fmt.Errorf("order not found"))
+		return 0, nil, false
+	}
+	return id, g, true
+}
+
+// applyAndRespond applies a mutation and returns the updated order. A rejected
+// state transition (handler error) maps to 409 Conflict.
+func (s *server) applyAndRespond(w http.ResponseWriter, r *http.Request, id order.OrderId, msg proto.Message) {
+	res, err := s.applier.Apply(r.Context(), uint64(id), msg)
+	if err != nil {
+		writeErr(w, http.StatusInternalServerError, err)
+		return
+	}
+	for _, m := range res.Mutations {
+		if m.Error != nil {
+			writeErr(w, http.StatusConflict, m.Error)
+			return
+		}
+	}
+	grain, err := s.applier.Get(r.Context(), uint64(id))
+	if err != nil {
+		writeErr(w, http.StatusInternalServerError, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"orderId": id.String(), "order": grain})
+}
+
+// --- lifecycle (b) --------------------------------------------------------
+
+type fulfillReq struct {
+	Carrier        string `json:"carrier,omitempty"`
+	TrackingNumber string `json:"trackingNumber,omitempty"`
+	TrackingURI    string `json:"trackingUri,omitempty"`
+	Lines          []struct {
+		Reference string `json:"reference"`
+		Quantity  int32  `json:"quantity"`
+	} `json:"lines"`
+}
+
+func (s *server) handleFulfill(w http.ResponseWriter, r *http.Request) {
+	id, _, ok := s.loadOrder(w, r)
+	if !ok {
+		return
+	}
+	var req fulfillReq
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeErr(w, http.StatusBadRequest, err)
+		return
+	}
+	fid, _ := order.NewOrderId()
+	msg := &messages.CreateFulfillment{
+		Id:             "f_" + fid.String(),
+		Carrier:        req.Carrier,
+		TrackingNumber: req.TrackingNumber,
+		TrackingUri:    req.TrackingURI,
+		AtMs:           nowMs(),
+	}
+	for _, l := range req.Lines {
+		msg.Lines = append(msg.Lines, &messages.FulfillmentLine{Reference: l.Reference, Quantity: l.Quantity})
+	}
+	s.applyAndRespond(w, r, id, msg)
+}
+
+func (s *server) handleComplete(w http.ResponseWriter, r *http.Request) {
+	id, _, ok := s.loadOrder(w, r)
+	if !ok {
+		return
+	}
+	s.applyAndRespond(w, r, id, &messages.CompleteOrder{AtMs: nowMs()})
+}
+
+func (s *server) handleCancel(w http.ResponseWriter, r *http.Request) {
+	id, _, ok := s.loadOrder(w, r)
+	if !ok {
+		return
+	}
+	var req struct {
+		Reason string `json:"reason"`
+	}
+	_ = json.NewDecoder(r.Body).Decode(&req)
+	s.applyAndRespond(w, r, id, &messages.CancelOrder{Reason: req.Reason, AtMs: nowMs()})
+}
+
+type returnReq struct {
+	Reason string `json:"reason,omitempty"`
+	Lines  []struct {
+		Reference string `json:"reference"`
+		Quantity  int32  `json:"quantity"`
+	} `json:"lines"`
+}
+
+func (s *server) handleReturn(w http.ResponseWriter, r *http.Request) {
+	id, _, ok := s.loadOrder(w, r)
+	if !ok {
+		return
+	}
+	var req returnReq
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeErr(w, http.StatusBadRequest, err)
+		return
+	}
+	rid, _ := order.NewOrderId()
+	msg := &messages.RequestReturn{Id: "r_" + rid.String(), Reason: req.Reason, AtMs: nowMs()}
+	for _, l := range req.Lines {
+		msg.Lines = append(msg.Lines, &messages.FulfillmentLine{Reference: l.Reference, Quantity: l.Quantity})
+	}
+	s.applyAndRespond(w, r, id, msg)
+}
+
+func (s *server) handleRefund(w http.ResponseWriter, r *http.Request) {
+	id, g, ok := s.loadOrder(w, r)
+	if !ok {
+		return
+	}
+	var req struct {
+		Amount int64 `json:"amount"`
+	}
+	_ = json.NewDecoder(r.Body).Decode(&req)
+	amount := req.Amount
+	if amount <= 0 {
+		amount = g.CapturedAmount - g.RefundedAmount // default: full remaining
+	}
+	captureRef := capturedRef(g)
+	ref, err := s.provider.Refund(r.Context(), captureRef, amount)
+	if err != nil {
+		writeErr(w, http.StatusBadGateway, fmt.Errorf("refund failed: %w", err))
+		return
+	}
+	s.applyAndRespond(w, r, id, &messages.IssueRefund{
+		Provider:  ref.Provider,
+		Amount:    ref.Amount,
+		Reference: ref.Reference,
+		AtMs:      nowMs(),
+	})
+}
+
+// --- saga / flow admin (a) ------------------------------------------------
+
+func (s *server) handleCapabilities(w http.ResponseWriter, _ *http.Request) {
+	writeJSON(w, http.StatusOK, s.freg.Capabilities())
+}
+
+func (s *server) handleListFlows(w http.ResponseWriter, _ *http.Request) {
+	writeJSON(w, http.StatusOK, s.flows.list())
+}
+
+func (s *server) handleGetFlow(w http.ResponseWriter, r *http.Request) {
+	def, ok := s.flows.get(r.PathValue("name"))
+	if !ok {
+		writeErr(w, http.StatusNotFound, fmt.Errorf("flow not found"))
+		return
+	}
+	writeJSON(w, http.StatusOK, def)
+}
+
+func (s *server) handleSaveFlow(w http.ResponseWriter, r *http.Request) {
+	name := r.PathValue("name")
+	var def flow.Definition
+	if err := json.NewDecoder(r.Body).Decode(&def); err != nil {
+		writeErr(w, http.StatusBadRequest, err)
+		return
+	}
+	if err := s.flows.save(name, &def); err != nil {
+		// Validation failures (unknown action/hook/predicate) are client errors.
+		writeErr(w, http.StatusBadRequest, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, &def)
+}

cmd/order/handlers_checkout.go

@@ -0,0 +1,193 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/flow"
+	"git.k6n.net/mats/go-cart-actor/pkg/order"
+	messages "git.k6n.net/mats/go-cart-actor/proto/order"
+)
+
+// fromCheckoutReq is the payload the checkout service sends to create an order
+// from a settled (paid) checkout. All payment processing has already happened
+// via Klarna/Adyen on the checkout grain; the order service records the result
+// in its event-sourced grain.
+type fromCheckoutReq struct {
+	CheckoutId     string    `json:"checkoutId"`
+	IdempotencyKey string    `json:"idempotencyKey"`
+	Flow          string    `json:"flow,omitempty"`
+
+	CartId        string    `json:"cartId"`
+	Currency      string    `json:"currency"`
+	Locale        string    `json:"locale,omitempty"`
+	Country       string    `json:"country"`
+	CustomerEmail string    `json:"customerEmail,omitempty"`
+	CustomerName  string    `json:"customerName,omitempty"`
+	Lines         []lineReq `json:"lines"`
+
+	// Payment carries the externally-settled payment result. The provider has
+	// already authorized and captured; the order grain records these facts.
+	Payment struct {
+		Provider  string `json:"provider"`  // "klarna" or "adyen"
+		Reference string `json:"reference"` // processor reference (PSP reference)
+		Amount    int64  `json:"amount"`    // minor units
+	} `json:"payment"`
+}
+
+// handleFromCheckout creates an event-sourced order from a settled checkout.
+// It runs the place-and-pay flow with a passthrough provider that records the
+// already-completed authorization and capture, bypassing any external payment
+// call. The response carries the order grain, flow result, and order ID.
+//
+// Idempotent: a retry with the same idempotencyKey returns the existing order
+// (409 Conflict) rather than creating a duplicate.
+func (s *server) handleFromCheckout(w http.ResponseWriter, r *http.Request) {
+	var req fromCheckoutReq
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeErr(w, http.StatusBadRequest, fmt.Errorf("bad body: %w", err))
+		return
+	}
+	if len(req.Lines) == 0 {
+		writeErr(w, http.StatusBadRequest, fmt.Errorf("from-checkout: at least one line required"))
+		return
+	}
+
+	// ── Idempotency check ─────────────────────────────────────────────
+	// Lock the key for the whole check→create→record sequence so a concurrent
+	// retry with the same key can't race past the check and create a second
+	// order. The store is durable, so this also holds across a restart.
+	if req.IdempotencyKey != "" {
+		unlock := s.idem.Lock(req.IdempotencyKey)
+		defer unlock()
+		if existingID, ok := s.idem.Get(req.IdempotencyKey); ok {
+			// The order already exists — return it.
+			g, err := s.applier.Get(r.Context(), existingID)
+			if err != nil {
+				writeErr(w, http.StatusInternalServerError, fmt.Errorf("idempotent lookup: %w", err))
+				return
+			}
+			writeJSON(w, http.StatusConflict, map[string]any{
+				"orderId":  order.OrderId(existingID).String(),
+				"order":    g,
+				"existing": true,
+			})
+			return
+		}
+	}
+
+	// ── Create the order grain ────────────────────────────────────────
+	id, err := order.NewOrderId()
+	if err != nil {
+		writeErr(w, http.StatusInternalServerError, fmt.Errorf("new order id: %w", err))
+		return
+	}
+	ordID := uint64(id)
+
+	// Build PlaceOrder from the same lineReq format the direct checkout uses.
+	po := buildFromCheckoutPlaceOrder(id, &req)
+
+	// Build a passthrough provider for the externally-settled payment.
+	provider := order.NewPassthroughProvider(req.Payment.Provider, req.Payment.Reference, req.Payment.Amount)
+
+	// Run the place-and-pay flow with the passthrough provider. Since the
+	// payment is already settled, this records the authorization and capture
+	// without any external call.
+	flowName := req.Flow
+	if flowName == "" {
+		flowName = s.defaultFlow
+	}
+	def, ok := s.flows.get(flowName)
+	if !ok {
+		writeErr(w, http.StatusBadRequest, fmt.Errorf("unknown flow %q", flowName))
+		return
+	}
+
+	// Create a per-request flow registry so the authorize/capture actions use
+	// the passthrough provider for this specific order. RegisterFlowActions
+	// registers all order lifecycle actions, overriding the default provider.
+	freg := flow.NewRegistry()
+	flow.RegisterBuiltinHooks(freg)
+	order.RegisterFlowActions(freg, s.applier, provider)
+	order.RegisterEmitHook(freg, nil)
+
+	engine := flow.NewEngine(freg, s.logger)
+
+	st := flow.NewState(ordID, s.logger)
+	st.Vars[order.PlaceOrderVar] = po
+
+	res, runErr := engine.Run(r.Context(), def, st)
+	grain, getErr := s.applier.Get(r.Context(), ordID)
+	if getErr != nil {
+		writeErr(w, http.StatusInternalServerError, getErr)
+		return
+	}
+
+	// On failure the flow should have compensated (voided + cancelled). Return
+	// the failed order with the flow trace so the checkout service can decide
+	// how to proceed (e.g. alert operator, retry with a new idempotency key).
+	status := http.StatusCreated
+	if runErr != nil {
+		status = http.StatusPaymentRequired
+		s.logger.Warn("from-checkout flow failed", "orderId", id.String(), "err", runErr)
+	}
+
+	// Record the idempotency key durably only on success, so retries (incl. after
+	// a restart) return the captured order. A failed flow (402) is deliberately
+	// NOT recorded: the failed grain is terminal, and a retry with the same key
+	// should re-attempt rather than be handed back a dead order as a 409 hit
+	// (which the checkout client treats as a successful, existing order).
+	if req.IdempotencyKey != "" && runErr == nil {
+		if err := s.idem.Put(req.IdempotencyKey, ordID); err != nil {
+			s.logger.Error("idempotency record failed", "key", req.IdempotencyKey, "orderId", id.String(), "err", err)
+		}
+	}
+
+	writeJSON(w, status, map[string]any{
+		"orderId": id.String(),
+		"flow":    res,
+		"order":   grain,
+	})
+}
+
+// buildFromCheckoutPlaceOrder converts a from-checkout request into a PlaceOrder
+// proto message, computing per-line and order totals from the lineReq entries.
+func buildFromCheckoutPlaceOrder(id order.OrderId, req *fromCheckoutReq) *messages.PlaceOrder {
+	orderRef := "ord-" + id.String()
+	po := &messages.PlaceOrder{
+		OrderReference: orderRef,
+		CartId:         req.CartId,
+		Currency:       req.Currency,
+		Locale:         req.Locale,
+		Country:        req.Country,
+		CustomerEmail:  req.CustomerEmail,
+		CustomerName:   req.CustomerName,
+		PlacedAtMs:     time.Now().UnixMilli(),
+	}
+	var total, totalTax int64
+	for _, l := range req.Lines {
+		lineTotal := l.UnitPrice * int64(l.Quantity)
+		var lineTax int64
+		if l.TaxRate > 0 {
+			// inc-vat -> tax portion = total * rate / (100 + rate)
+			lineTax = lineTotal * int64(l.TaxRate) / int64(100+l.TaxRate)
+		}
+		total += lineTotal
+		totalTax += lineTax
+		po.Lines = append(po.Lines, &messages.OrderLine{
+			Reference:   l.Reference,
+			Sku:         l.Sku,
+			Name:        l.Name,
+			Quantity:    l.Quantity,
+			UnitPrice:   l.UnitPrice,
+			TaxRate:     l.TaxRate,
+			TotalAmount: lineTotal,
+			TotalTax:    lineTax,
+		})
+	}
+	po.TotalAmount = total
+	po.TotalTax = totalTax
+	return po
+}

cmd/order/main.go

@@ -0,0 +1,504 @@
+// Command order is a single-node HTTP entrypoint for the order grain. It exposes
+// a simple checkout that creates an order by running the place-and-pay flow
+// (place -> mock authorize -> capture) on the actor framework, plus read APIs
+// for an order and its event timeline. No clustering, no external payment — the
+// simplest path to a real, event-sourced, captured order.
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"log/slog"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/internal/ucp"
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/flow"
+	"git.k6n.net/mats/go-cart-actor/pkg/idempotency"
+	"git.k6n.net/mats/go-cart-actor/pkg/order"
+	ordermcp "git.k6n.net/mats/go-cart-actor/pkg/order/mcp"
+	"git.k6n.net/mats/go-cart-actor/pkg/outbox"
+	messages "git.k6n.net/mats/go-cart-actor/proto/order"
+
+	"google.golang.org/protobuf/encoding/protojson"
+	"google.golang.org/protobuf/proto"
+)
+
+type server struct {
+	pool        *actor.SimpleGrainPool[order.OrderGrain]
+	applier     *orderedApplier
+	storage     *actor.DiskStorage[order.OrderGrain]
+	reg         actor.MutationRegistry
+	engine      *flow.Engine
+	freg        *flow.Registry
+	flows       *flowStore
+	provider    order.PaymentProvider
+	defaultFlow string
+	dataDir     string
+	idem        *idempotency.Store
+	logger      *slog.Logger
+}
+
+func main() {
+	addr := envOr("ORDER_ADDR", ":8092") // :8090 cart, :8091 redirector
+	dataDir := envOr("ORDER_DATA", "data/orders")
+	flowsDir := envOr("ORDER_FLOWS", "data/order-flows")
+	if err := os.MkdirAll(dataDir, 0o755); err != nil {
+		log.Fatalf("create data dir: %v", err)
+	}
+	logger := slog.New(slog.NewTextHandler(os.Stdout, nil))
+
+	reg := actor.NewMutationRegistry()
+	order.RegisterMutations(reg)
+	storage := actor.NewDiskStorage[order.OrderGrain](dataDir, reg)
+
+	pool, err := actor.NewSimpleGrainPool(actor.GrainPoolConfig[order.OrderGrain]{
+		Hostname: "order-1",
+		Spawn: func(ctx context.Context, id uint64) (actor.Grain[order.OrderGrain], error) {
+			g := order.NewOrderGrain(id, time.Now())
+			// Replay any persisted history so the resident grain is current.
+			if err := storage.LoadEvents(ctx, id, g); err != nil {
+				return nil, err
+			}
+			return g, nil
+		},
+		SpawnHost: func(string) (actor.Host[order.OrderGrain], error) {
+			return nil, fmt.Errorf("order service is single-node")
+		},
+		Destroy:  func(actor.Grain[order.OrderGrain]) error { return nil },
+		TTL:      time.Hour,
+		PoolSize: 10000,
+		// Storage is intentionally nil here: the pool persists mutations in a
+		// fire-and-forget goroutine, so concurrent appends for one grain can land
+		// out of order on disk — fatal for an event log, where replay order is the
+		// state. We persist through orderedApplier instead (synchronous, ordered,
+		// and only for mutations that actually applied). Replay on spawn still uses
+		// `storage` directly in Spawn above.
+		MutationRegistry: reg,
+		Storage:          nil,
+	})
+	if err != nil {
+		log.Fatalf("create pool: %v", err)
+	}
+
+	applier := &orderedApplier{pool: pool, storage: storage}
+	provider := selectProvider(logger)
+
+	// Flow registry: generic hooks + the order lifecycle actions + predicates,
+	// paying via the selected provider. The amqp_emit hook bridges saga steps to
+	// the broker (publisher is nil without AMQP — the hook then errors at run
+	// time, which is logged, not fatal).
+	amqpURL := os.Getenv("AMQP_URL")
+	var emitPub order.Publisher
+	if amqpURL != "" {
+		// The amqp_emit hook writes to a durable outbox rather than the broker
+		// directly; a relay goroutine drains it to RabbitMQ (reconnecting), so an
+		// event survives a broker outage or a crash after the state change.
+		box, err := outbox.Open(filepath.Join(dataDir, "outbox.log"))
+		if err != nil {
+			// Durability-critical (same as the idempotency store): fail fast rather
+			// than silently publish events nowhere for the whole process lifetime.
+			log.Fatalf("open outbox: %v", err)
+		}
+		go box.Run(context.Background(), newRabbitPublisher(amqpURL), 5*time.Second, logger)
+		emitPub = box
+	}
+	freg := flow.NewRegistry()
+	flow.RegisterBuiltinHooks(freg)
+	order.RegisterFlowActions(freg, applier, provider)
+	order.RegisterEmitHook(freg, emitPub)
+	engine := flow.NewEngine(freg, logger)
+
+	def, err := order.EmbeddedFlow("place-and-pay")
+	if err != nil {
+		log.Fatalf("load flow: %v", err)
+	}
+	flows, err := newFlowStore(flowsDir, engine, map[string]*flow.Definition{def.Name: def})
+	if err != nil {
+		log.Fatalf("load flows: %v", err)
+	}
+
+	// Durable idempotency store for order creation — survives a restart, so a
+	// client retry after a crash returns the existing order instead of creating
+	// a duplicate.
+	idem, err := idempotency.Open(filepath.Join(dataDir, "idempotency.log"))
+	if err != nil {
+		log.Fatalf("open idempotency store: %v", err)
+	}
+
+	s := &server{
+		pool: pool, applier: applier, storage: storage, reg: reg,
+		engine: engine, freg: freg, flows: flows, provider: provider,
+		defaultFlow: def.Name, dataDir: dataDir, idem: idem, logger: logger,
+	}
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /healthz", func(w http.ResponseWriter, _ *http.Request) { w.WriteHeader(http.StatusOK) })
+
+	// Checkout + order reads.
+	mux.HandleFunc("POST /checkout", s.handleCheckout)
+	mux.HandleFunc("POST /api/orders/from-checkout", s.handleFromCheckout)
+	mux.HandleFunc("GET /api/orders", s.handleList)
+	mux.HandleFunc("GET /api/orders/{id}", s.handleGet)
+	mux.HandleFunc("GET /api/orders/{id}/events", s.handleEvents)
+
+	// Post-purchase lifecycle (the grain already supports these transitions).
+	mux.HandleFunc("POST /api/orders/{id}/fulfillments", s.handleFulfill)
+	mux.HandleFunc("POST /api/orders/{id}/complete", s.handleComplete)
+	mux.HandleFunc("POST /api/orders/{id}/cancel", s.handleCancel)
+	mux.HandleFunc("POST /api/orders/{id}/returns", s.handleReturn)
+	mux.HandleFunc("POST /api/orders/{id}/refunds", s.handleRefund)
+
+	// UCP REST adapter — Universal Commerce Protocol order lifecycle.
+	orderUCP := ucp.OrderHandler(s.applier)
+	if signer := loadUCPOrderSigner(); signer != nil {
+		orderUCP = ucp.WithSigning(orderUCP, signer)
+		logger.Info("ucp signing enabled")
+	}
+	// StripPrefix is required because the sub-mux (OrderHandler) registers
+	// routes like "GET /{id}" which expect a relative path; Go's ServeMux
+	// passes the full request path without stripping the prefix.
+	// Only the subtree pattern is registered (see comment in cmd/cart/main.go
+	// for why the exact-match pattern is omitted).
+	mux.Handle("/ucp/v1/orders/", http.StripPrefix("/ucp/v1/orders", orderUCP))
+
+	// Order MCP streamable-HTTP server (inspect + mutate orders via tools).
+	// Mounted at /order-mcp to avoid conflicting with the backoffice CMS MCP at
+	// /mcp (which is routed by the edge).
+	orderMCP := ordermcp.New(applier)
+	mux.Handle("/order-mcp", orderMCP.Handler())
+	mux.Handle("/order-mcp/", orderMCP.Handler())
+
+	// Saga / flow admin (backoffice editor).
+	mux.HandleFunc("GET /sagas/capabilities", s.handleCapabilities)
+	mux.HandleFunc("GET /sagas/flows", s.handleListFlows)
+	mux.HandleFunc("GET /sagas/flows/{name}", s.handleGetFlow)
+	mux.HandleFunc("PUT /sagas/flows/{name}", s.handleSaveFlow)
+
+	// Ingest legacy checkout orders (Klarna/Adyen → order-queue) so this service
+	// is the single source of orders, superseding go-order-manager.
+	if amqpURL != "" {
+		startLegacyIngest(context.Background(), amqpURL, applier, logger)
+	}
+
+	logger.Info("order service listening", "addr", addr, "data", dataDir, "flows", flowsDir)
+	if err := http.ListenAndServe(addr, mux); err != nil {
+		log.Fatalf("serve: %v", err)
+	}
+}
+
+// orderedApplier wraps the grain pool to persist the event log correctly: it
+// appends each applied mutation synchronously and in call order (the pool's own
+// storage path is async/unordered), and only persists mutations whose handler
+// succeeded — a rejected transition must never enter the log. A single mutex
+// serialises all appends, which is ample for a single-node checkout service.
+type orderedApplier struct {
+	pool    *actor.SimpleGrainPool[order.OrderGrain]
+	storage *actor.DiskStorage[order.OrderGrain]
+	mu      sync.Mutex
+}
+
+func (a *orderedApplier) Get(ctx context.Context, id uint64) (*order.OrderGrain, error) {
+	return a.pool.Get(ctx, id)
+}
+
+func (a *orderedApplier) Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*actor.MutationResult[order.OrderGrain], error) {
+	res, err := a.pool.Apply(ctx, id, mutation...)
+	if err != nil || res == nil {
+		return res, err
+	}
+	// Persist only the mutations that actually applied (result index aligns with
+	// the input order).
+	applied := make([]proto.Message, 0, len(mutation))
+	for i, m := range mutation {
+		if i < len(res.Mutations) && res.Mutations[i].Error != nil {
+			continue
+		}
+		applied = append(applied, m)
+	}
+	if len(applied) > 0 {
+		a.mu.Lock()
+		appendErr := a.storage.AppendMutations(id, applied...)
+		a.mu.Unlock()
+		if appendErr != nil {
+			return res, appendErr
+		}
+	}
+	return res, nil
+}
+
+// --- checkout -------------------------------------------------------------
+
+type lineReq struct {
+	Reference string `json:"reference"`
+	Sku       string `json:"sku"`
+	Name      string `json:"name"`
+	Quantity  int32  `json:"quantity"`
+	UnitPrice int64  `json:"unitPrice"` // inc-vat, minor units
+	TaxRate   int32  `json:"taxRate"`   // percent
+}
+
+type checkoutReq struct {
+	OrderReference  string          `json:"orderReference,omitempty"`
+	CartId          string          `json:"cartId,omitempty"`
+	Currency        string          `json:"currency,omitempty"`
+	Locale          string          `json:"locale,omitempty"`
+	Country         string          `json:"country,omitempty"`
+	CustomerEmail   string          `json:"customerEmail,omitempty"`
+	CustomerName    string          `json:"customerName,omitempty"`
+	BillingAddress  json.RawMessage `json:"billingAddress,omitempty"`
+	ShippingAddress json.RawMessage `json:"shippingAddress,omitempty"`
+	Lines           []lineReq       `json:"lines"`
+}
+
+func (s *server) handleCheckout(w http.ResponseWriter, r *http.Request) {
+	var req checkoutReq
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeErr(w, http.StatusBadRequest, fmt.Errorf("bad body: %w", err))
+		return
+	}
+	if len(req.Lines) == 0 {
+		writeErr(w, http.StatusBadRequest, fmt.Errorf("checkout requires at least one line"))
+		return
+	}
+
+	id, err := order.NewOrderId()
+	if err != nil {
+		writeErr(w, http.StatusInternalServerError, err)
+		return
+	}
+	if req.OrderReference == "" {
+		req.OrderReference = "ord-" + id.String()
+	}
+	if req.Currency == "" {
+		req.Currency = "SEK"
+	}
+
+	flowName := r.URL.Query().Get("flow")
+	if flowName == "" {
+		flowName = s.defaultFlow
+	}
+	def, ok := s.flows.get(flowName)
+	if !ok {
+		writeErr(w, http.StatusBadRequest, fmt.Errorf("unknown flow %q", flowName))
+		return
+	}
+
+	po := buildPlaceOrder(id, &req)
+
+	st := flow.NewState(uint64(id), s.logger)
+	st.Vars[order.PlaceOrderVar] = po
+
+	res, runErr := s.engine.Run(r.Context(), def, st)
+	grain, getErr := s.pool.Get(r.Context(), uint64(id))
+	if getErr != nil {
+		writeErr(w, http.StatusInternalServerError, getErr)
+		return
+	}
+
+	status := http.StatusCreated
+	if runErr != nil {
+		// The flow compensated; the order exists but is not paid. Report 402 with
+		// the (now cancelled/failed) order and the flow trace so the caller knows.
+		status = http.StatusPaymentRequired
+		s.logger.Warn("checkout flow failed", "orderId", id.String(), "err", runErr)
+	}
+	writeJSON(w, status, map[string]any{
+		"orderId": id.String(),
+		"flow":    res,
+		"order":   grain,
+	})
+}
+
+// buildPlaceOrder converts a checkout request into the PlaceOrder event,
+// computing per-line and order totals (inc-vat) from the lines.
+func buildPlaceOrder(id order.OrderId, req *checkoutReq) *messages.PlaceOrder {
+	po := &messages.PlaceOrder{
+		OrderReference:  req.OrderReference,
+		CartId:          req.CartId,
+		Currency:        req.Currency,
+		Locale:          req.Locale,
+		Country:         req.Country,
+		CustomerEmail:   req.CustomerEmail,
+		CustomerName:    req.CustomerName,
+		BillingAddress:  req.BillingAddress,
+		ShippingAddress: req.ShippingAddress,
+		PlacedAtMs:      time.Now().UnixMilli(),
+	}
+	var total, totalTax int64
+	for _, l := range req.Lines {
+		lineTotal := l.UnitPrice * int64(l.Quantity)
+		var lineTax int64
+		if l.TaxRate > 0 {
+			// inc-vat -> tax portion = total * rate / (100 + rate)
+			lineTax = lineTotal * int64(l.TaxRate) / int64(100+l.TaxRate)
+		}
+		total += lineTotal
+		totalTax += lineTax
+		po.Lines = append(po.Lines, &messages.OrderLine{
+			Reference:   l.Reference,
+			Sku:         l.Sku,
+			Name:        l.Name,
+			Quantity:    l.Quantity,
+			UnitPrice:   l.UnitPrice,
+			TaxRate:     l.TaxRate,
+			TotalAmount: lineTotal,
+			TotalTax:    lineTax,
+		})
+	}
+	po.TotalAmount = total
+	po.TotalTax = totalTax
+	return po
+}
+
+// --- reads ----------------------------------------------------------------
+
+func (s *server) handleGet(w http.ResponseWriter, r *http.Request) {
+	id, ok := order.ParseOrderId(r.PathValue("id"))
+	if !ok {
+		writeErr(w, http.StatusBadRequest, fmt.Errorf("invalid order id"))
+		return
+	}
+	grain, err := s.pool.Get(r.Context(), uint64(id))
+	if err != nil {
+		writeErr(w, http.StatusInternalServerError, err)
+		return
+	}
+	if grain.Status == order.StatusNew {
+		writeErr(w, http.StatusNotFound, fmt.Errorf("order not found"))
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"orderId": id.String(), "order": grain})
+}
+
+type eventView struct {
+	Type    string          `json:"type"`
+	Time    string          `json:"time,omitempty"`
+	Payload json.RawMessage `json:"payload,omitempty"`
+}
+
+// handleEvents returns the raw event timeline by reading the grain's append-only
+// log (the source of truth) without re-applying it to live state.
+func (s *server) handleEvents(w http.ResponseWriter, r *http.Request) {
+	id, ok := order.ParseOrderId(r.PathValue("id"))
+	if !ok {
+		writeErr(w, http.StatusBadRequest, fmt.Errorf("invalid order id"))
+		return
+	}
+	var events []eventView
+	throwaway := order.NewOrderGrain(uint64(id), time.Now())
+	err := s.storage.LoadEventsFunc(r.Context(), uint64(id), throwaway,
+		func(msg proto.Message, _ int, ts time.Time) bool {
+			name, _ := s.reg.GetTypeName(msg)
+			payload, _ := protojson.Marshal(msg)
+			events = append(events, eventView{Type: name, Time: ts.UTC().Format(time.RFC3339), Payload: payload})
+			return false // collect only; do not apply
+		})
+	if err != nil {
+		writeErr(w, http.StatusInternalServerError, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"orderId": id.String(), "events": events})
+}
+
+type orderSummary struct {
+	OrderId        string       `json:"orderId"`
+	Reference      string       `json:"reference,omitempty"`
+	Status         order.Status `json:"status"`
+	TotalAmount    int64        `json:"totalAmount"`
+	CapturedAmount int64        `json:"capturedAmount"`
+	Currency       string       `json:"currency,omitempty"`
+	PlacedAt       string       `json:"placedAt,omitempty"`
+}
+
+// handleList scans the data dir for order logs and summarises each (replaying it
+// through the pool). Fine for a single-node simple checkout; a production list
+// would use an index/projection store.
+func (s *server) handleList(w http.ResponseWriter, r *http.Request) {
+	matches, _ := filepath.Glob(filepath.Join(s.dataDir, "*.events.log"))
+	out := make([]orderSummary, 0, len(matches))
+	for _, m := range matches {
+		base := strings.TrimSuffix(filepath.Base(m), ".events.log")
+		raw, err := strconv.ParseUint(base, 10, 64)
+		if err != nil {
+			continue
+		}
+		g, err := s.pool.Get(r.Context(), raw)
+		if err != nil || g.Status == order.StatusNew {
+			continue
+		}
+		out = append(out, orderSummary{
+			OrderId:        order.OrderId(raw).String(),
+			Reference:      g.OrderReference,
+			Status:         g.Status,
+			TotalAmount:    g.TotalAmount,
+			CapturedAmount: g.CapturedAmount,
+			Currency:       g.Currency,
+			PlacedAt:       g.PlacedAt,
+		})
+	}
+	writeJSON(w, http.StatusOK, out)
+}
+
+// --- helpers --------------------------------------------------------------
+
+// selectProvider picks the payment provider from the environment. Default is
+// the dependency-free mock; set PAYMENT_PROVIDER=stripe + STRIPE_SECRET_KEY for
+// real Stripe (STRIPE_API_BASE / STRIPE_PAYMENT_METHOD optionally override).
+func selectProvider(logger *slog.Logger) order.PaymentProvider {
+	if os.Getenv("PAYMENT_PROVIDER") == "stripe" {
+		key := os.Getenv("STRIPE_SECRET_KEY")
+		if key == "" {
+			logger.Warn("PAYMENT_PROVIDER=stripe but STRIPE_SECRET_KEY is empty; falling back to mock")
+			return order.NewMockProvider()
+		}
+		logger.Info("using stripe payment provider")
+		return order.NewStripeProvider(key, os.Getenv("STRIPE_API_BASE"), os.Getenv("STRIPE_PAYMENT_METHOD"))
+	}
+	return order.NewMockProvider()
+}
+
+// loadUCPOrderSigner loads the UCP ECDSA signing key from the path specified in
+// the UCP_SIGNING_KEY_PATH environment variable. Returns nil if unset or unreadable.
+func loadUCPOrderSigner() *ucp.SigningConfig {
+	path := os.Getenv("UCP_SIGNING_KEY_PATH")
+	if path == "" {
+		return nil
+	}
+	pemData, err := os.ReadFile(path)
+	if err != nil {
+		log.Printf("ucp signing: cannot read key %s: %v", path, err)
+		return nil
+	}
+	cfg, err := ucp.NewSigningConfigFromPEM(pemData, "k6n-ecdsa-2026")
+	if err != nil {
+		log.Printf("ucp signing: invalid key at %s: %v", path, err)
+		return nil
+	}
+	return cfg
+}
+
+func envOr(key, def string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return def
+}
+
+func writeJSON(w http.ResponseWriter, status int, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(v)
+}
+
+func writeErr(w http.ResponseWriter, status int, err error) {
+	writeJSON(w, status, map[string]string{"error": err.Error()})
+}

cmd/profile/main.go

@@ -0,0 +1,188 @@
+package main
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"os/signal"
+	"path/filepath"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/internal/customerauth"
+	"git.k6n.net/mats/go-cart-actor/internal/ucp"
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/profile"
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+)
+
+// authSecret returns the HMAC key for customer session cookies. It reads
+// CUSTOMER_AUTH_SECRET; when unset it generates an ephemeral random key and
+// warns that issued sessions will not survive a restart (fine for dev).
+func authSecret() []byte {
+	if v := os.Getenv("CUSTOMER_AUTH_SECRET"); v != "" {
+		return []byte(v)
+	}
+	b := make([]byte, 32)
+	if _, err := rand.Read(b); err != nil {
+		log.Fatalf("could not generate auth secret: %v", err)
+	}
+	log.Print("warning: CUSTOMER_AUTH_SECRET unset — using an ephemeral key; customer sessions will not survive a restart")
+	return []byte(hex.EncodeToString(b))
+}
+
+var podIp = os.Getenv("POD_IP")
+var name = os.Getenv("POD_NAME")
+
+// loadUCPProfileSigner loads the UCP ECDSA signing key from the path specified in
+// the UCP_SIGNING_KEY_PATH environment variable. Returns nil if unset or unreadable.
+func loadUCPProfileSigner() *ucp.SigningConfig {
+	path := os.Getenv("UCP_SIGNING_KEY_PATH")
+	if path == "" {
+		return nil
+	}
+	pemData, err := os.ReadFile(path)
+	if err != nil {
+		log.Printf("ucp signing: cannot read key %s: %v", path, err)
+		return nil
+	}
+	cfg, err := ucp.NewSigningConfigFromPEM(pemData, "k6n-ecdsa-2026")
+	if err != nil {
+		log.Printf("ucp signing: invalid key at %s: %v", path, err)
+		return nil
+	}
+	return cfg
+}
+
+// getEnv returns the value of the environment variable named by key, or def if unset/empty.
+func getEnv(key, def string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return def
+}
+
+func main() {
+	reg := profile.NewProfileMutationRegistry()
+
+	profileDir := getEnv("PROFILE_DIR", "data/profiles")
+	if err := os.MkdirAll(profileDir, 0755); err != nil {
+		log.Printf("warning: could not create profile data directory %s: %v", profileDir, err)
+	}
+	diskStorage := actor.NewDiskStorage[profile.ProfileGrain](profileDir, reg)
+
+	poolConfig := actor.GrainPoolConfig[profile.ProfileGrain]{
+		MutationRegistry: reg,
+		Storage:          diskStorage,
+		Spawn: func(ctx context.Context, id uint64) (actor.Grain[profile.ProfileGrain], error) {
+			ret := profile.NewProfileGrain(id, time.Now())
+			err := diskStorage.LoadEvents(ctx, id, ret)
+			return ret, err
+		},
+		// Destroy is an optional grain-eviction cleanup hook; profiles need none
+		// (disk storage persists via its own loop), so it's left unset — purge()
+		// skips a nil Destroy.
+		TTL:      10 * time.Minute,
+		PoolSize: 65535,
+		Hostname: podIp,
+	}
+
+	pool, err := actor.NewSimpleGrainPool(poolConfig)
+	if err != nil {
+		log.Fatalf("Error creating profile pool: %v\n", err)
+	}
+
+	mux := http.NewServeMux()
+	debugMux := http.NewServeMux()
+
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
+	defer stop()
+
+	otelShutdown, err := setupOTelSDK(ctx)
+	if err != nil {
+		log.Fatalf("Unable to start otel %v", err)
+	}
+
+	// UCP Customer REST adapter
+	customerUCP := ucp.CustomerHandler(pool)
+	if signer := loadUCPProfileSigner(); signer != nil {
+		customerUCP = ucp.WithSigning(customerUCP, signer)
+		log.Print("ucp customer signing enabled")
+	}
+	// StripPrefix is required because the sub-mux (CustomerHandler) registers
+	// routes like "GET /{id}" which expect a relative path; Go's ServeMux
+	// passes the full request path without stripping the prefix.
+	mux.Handle("/ucp/v1/customers/", http.StripPrefix("/ucp/v1/customers", customerUCP))
+
+	// Customer auth: password signup/login + session cookies + identity linking.
+	credStore, err := customerauth.LoadCredentialStore(filepath.Join(profileDir, "credentials.json"))
+	if err != nil {
+		log.Fatalf("Error loading credential store: %v\n", err)
+	}
+	authHandler := customerauth.NewServer(credStore, pool, customerauth.NewSigner(authSecret()), 0).Handler()
+	mux.Handle("/ucp/v1/auth/", http.StripPrefix("/ucp/v1/auth", authHandler))
+
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		grainCount, capacity := pool.LocalUsage()
+		if grainCount >= capacity {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte("grain pool at capacity"))
+			return
+		}
+		if !pool.IsHealthy() {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte("pool not healthy"))
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("ok"))
+	})
+	mux.HandleFunc("/readyz", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("ok"))
+	})
+	mux.HandleFunc("/livez", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("ok"))
+	})
+
+	mux.HandleFunc("/version", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("1.0.0"))
+	})
+
+	srv := &http.Server{
+		Addr:         getEnv("PROFILE_ADDR", ":8080"),
+		BaseContext:  func(net.Listener) context.Context { return ctx },
+		ReadTimeout:  10 * time.Second,
+		WriteTimeout: 20 * time.Second,
+		Handler:      otelhttp.NewHandler(mux, "/"),
+	}
+
+	defer func() {
+		fmt.Println("Shutting down profile service")
+		otelShutdown(context.Background())
+		diskStorage.Close()
+		pool.Close()
+	}()
+
+	srvErr := make(chan error, 1)
+	go func() {
+		srvErr <- srv.ListenAndServe()
+	}()
+
+	log.Print("Profile server started at port 8080")
+
+	go http.ListenAndServe(":8081", debugMux)
+
+	select {
+	case err = <-srvErr:
+		log.Fatalf("Unable to start server: %v", err)
+	case <-ctx.Done():
+		stop()
+	}
+}

cmd/profile/otel.go

@@ -0,0 +1,108 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc"
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/log/global"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/log"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/trace"
+)
+
+// setupOTelSDK bootstraps the OpenTelemetry pipeline.
+// If it does not return an error, make sure to call shutdown for proper cleanup.
+func setupOTelSDK(ctx context.Context) (func(context.Context) error, error) {
+	var shutdownFuncs []func(context.Context) error
+	var err error
+
+	shutdown := func(ctx context.Context) error {
+		var err error
+		for _, fn := range shutdownFuncs {
+			err = errors.Join(err, fn(ctx))
+		}
+		shutdownFuncs = nil
+		return err
+	}
+
+	handleErr := func(inErr error) {
+		err = errors.Join(inErr, shutdown(ctx))
+	}
+
+	prop := newPropagator()
+	otel.SetTextMapPropagator(prop)
+
+	tracerProvider, err := newTracerProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
+	otel.SetTracerProvider(tracerProvider)
+
+	meterProvider, err := newMeterProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, meterProvider.Shutdown)
+	otel.SetMeterProvider(meterProvider)
+
+	loggerProvider, err := newLoggerProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, loggerProvider.Shutdown)
+	global.SetLoggerProvider(loggerProvider)
+
+	return shutdown, err
+}
+
+func newPropagator() propagation.TextMapPropagator {
+	return propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	)
+}
+
+func newTracerProvider() (*trace.TracerProvider, error) {
+	traceExporter, err := otlptracegrpc.New(context.Background())
+	if err != nil {
+		return nil, err
+	}
+
+	tracerProvider := trace.NewTracerProvider(
+		trace.WithBatcher(traceExporter,
+			trace.WithBatchTimeout(time.Second)),
+	)
+	return tracerProvider, nil
+}
+
+func newMeterProvider() (*metric.MeterProvider, error) {
+	exporter, err := otlpmetricgrpc.New(context.Background())
+	if err != nil {
+		return nil, err
+	}
+
+	provider := metric.NewMeterProvider(metric.WithReader(metric.NewPeriodicReader(exporter)))
+	return provider, nil
+}
+
+func newLoggerProvider() (*log.LoggerProvider, error) {
+	logExporter, err := otlploggrpc.New(context.Background())
+	if err != nil {
+		return nil, err
+	}
+
+	loggerProvider := log.NewLoggerProvider(
+		log.WithProcessor(log.NewBatchProcessor(logExporter)),
+	)
+	return loggerProvider, nil
+}

cookies.txt

@@ -0,0 +1,5 @@
+# Netscape HTTP Cookie File
+# https://curl.se/docs/http-cookies.html
+# This file was generated by libcurl! Edit at your own risk.
+
+#HttpOnly_localhost	FALSE	/	FALSE	1761304670	cartid	4393545184291837

data/16076883129799757619.events.log

@@ -0,0 +1,37 @@
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+{"type":"ChangeQuantity","timestamp":"2026-06-14T13:28:50.254122718+02:00","mutation":{"Id":7}}
+{"type":"AddItem","timestamp":"2026-06-14T15:15:53.256709127+02:00","mutation":{"item_id":148722,"quantity":1,"price":2531850,"orgPrice":3164813,"sku":"A0166079","name":"SF vridfönster  1980x1580mm 1-luft, insida trä utsida aluminium, 2-glas pga storleken","image":"/A0166079.wimg","tax":2500,"sellerId":"1","sellerName":"Svenska Fönster","extra_json":"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"}}
+{"type":"AddItem","timestamp":"2026-06-14T15:15:53.256762929+02:00","mutation":{"item_id":170852,"quantity":1,"sku":"A0190103","name":"Rundad profil på karm \u0026 båge, SP utseende","image":"/UserFiles/Svenska_Fonster/Diverse/Genomskarning_rund_profil.jpg","tax":2500,"sellerId":"7","sellerName":"Kaski","parentId":11,"extra_json":"eyJidWxreSI6MCwiY2F0ZWdvcnkiOjE3NCwiZGVsZXRlIjpmYWxzZSwiZGVsaXZlcnlTdHJpbmciOiJOb3JtYWx0IDQtNiBhcmJldHN2ZWNrb3IiLCJkZWxpdmVyeVdlZWsiOjEwLCJkZXNjcmlwdGlvbiI6IiIsImhlaWdodE1hcmdpbiI6MTAsImlzQWNjZXNzb3J5Ijp0cnVlLCJtb2RlbCI6IllEIiwibW9kZWxEZXNjcmlwdGlvbiI6Ikthc2tpIFl0dGVyZMO2cnJhciB0aGVybW8iLCJwYWdlSWQiOjAsInByZXZpb3VzRGlzY291bnQiOjIwLCJ0YXhvbm9teSI6W10sInVuaXQiOiJzdCIsIndpZHRoTWFyZ2luIjoxMH0="}}
+{"type":"AddItem","timestamp":"2026-06-14T15:15:53.256793727+02:00","mutation":{"item_id":97103,"quantity":1,"price":4139744,"sku":"A0086072","name":"Brand klassat glas EI30 (välj även förankring)","image":"/UserFiles/Svenska_Fonster/Glas/Brand_Ei30.jpg","tax":2500,"sellerId":"0","parentId":11,"extra_json":"eyJhY2Nlc3NvcnlNYXRjaCI6IiIsImJ1bGt5IjowLCJjYXRlZ29yeSI6MjAsImRlbGV0ZSI6ZmFsc2UsImRlc2NyaXB0aW9uIjoiRXR0IGdsYXMgc29tIGtsYXJhciBrcmF2ZW4gRUkzMCIsImdyb3VwIjoiIiwiaXNBY2Nlc3NvcnkiOnRydWUsIm1vZGVsIjoiIiwicGFnZUlkIjowLCJ0YXhvbm9teSI6W10sInVuaXQiOiJzdCJ9"}}
+{"type":"ChangeQuantity","timestamp":"2026-06-14T15:16:03.078662993+02:00","mutation":{"Id":8,"quantity":1}}
+{"type":"ChangeQuantity","timestamp":"2026-06-14T15:16:03.54547595+02:00","mutation":{"Id":8}}
+{"type":"ChangeQuantity","timestamp":"2026-06-14T15:16:04.240661903+02:00","mutation":{"Id":9}}
+{"type":"ChangeQuantity","timestamp":"2026-06-14T15:16:05.581768231+02:00","mutation":{"Id":10}}
+{"type":"ChangeQuantity","timestamp":"2026-06-14T15:16:09.40673458+02:00","mutation":{"Id":11}}
+{"type":"ChangeQuantity","timestamp":"2026-06-14T15:16:11.41069986+02:00","mutation":{"Id":12}}
+{"type":"AddItem","timestamp":"2026-06-14T15:24:17.09761136+02:00","mutation":{"item_id":148722,"quantity":1,"price":2531850,"orgPrice":3164813,"sku":"A0166079","name":"SF vridfönster  1980x1580mm 1-luft, insida trä utsida aluminium, 2-glas pga storleken","image":"/A0166079.wimg","tax":2500,"sellerId":"1","sellerName":"Svenska Fönster","extra_json":"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"}}
+{"type":"AddItem","timestamp":"2026-06-14T15:24:17.097670772+02:00","mutation":{"item_id":170852,"quantity":1,"sku":"A0190103","name":"Rundad profil på karm \u0026 båge, SP utseende","image":"/UserFiles/Svenska_Fonster/Diverse/Genomskarning_rund_profil.jpg","tax":2500,"sellerId":"7","sellerName":"Kaski","parentId":13,"extra_json":"eyJidWxreSI6MCwiY2F0ZWdvcnkiOjE3NCwiZGVsZXRlIjpmYWxzZSwiZGVsaXZlcnlTdHJpbmciOiJOb3JtYWx0IDQtNiBhcmJldHN2ZWNrb3IiLCJkZWxpdmVyeVdlZWsiOjEwLCJkZXNjcmlwdGlvbiI6IiIsImhlaWdodE1hcmdpbiI6MTAsImlzQWNjZXNzb3J5Ijp0cnVlLCJtb2RlbCI6IllEIiwibW9kZWxEZXNjcmlwdGlvbiI6Ikthc2tpIFl0dGVyZMO2cnJhciB0aGVybW8iLCJwYWdlSWQiOjAsInByZXZpb3VzRGlzY291bnQiOjIwLCJ0YXhvbm9teSI6W10sInVuaXQiOiJzdCIsIndpZHRoTWFyZ2luIjoxMH0="}}
+{"type":"AddItem","timestamp":"2026-06-14T15:24:17.097710397+02:00","mutation":{"item_id":97103,"quantity":1,"price":4139744,"sku":"A0086072","name":"Brand klassat glas EI30 (välj även förankring)","image":"/UserFiles/Svenska_Fonster/Glas/Brand_Ei30.jpg","tax":2500,"sellerId":"0","parentId":13,"extra_json":"eyJhY2Nlc3NvcnlNYXRjaCI6IiIsImJ1bGt5IjowLCJjYXRlZ29yeSI6MjAsImRlbGV0ZSI6ZmFsc2UsImRlc2NyaXB0aW9uIjoiRXR0IGdsYXMgc29tIGtsYXJhciBrcmF2ZW4gRUkzMCIsImdyb3VwIjoiIiwiaXNBY2Nlc3NvcnkiOnRydWUsIm1vZGVsIjoiIiwicGFnZUlkIjowLCJ0YXhvbm9teSI6W10sInVuaXQiOiJzdCJ9"}}

data/promotions.json

@@ -0,0 +1,45 @@
+{
+  "version": 1,
+  "state": {
+    "promotions": [
+      {
+        "id": "volymrabatt",
+        "name": "Volymrabatt",
+        "description": "Automatisk volymrabatt baserad på varukorgens totalsumma (inkl. moms). Belopp i öre: 20 000–40 000 kr → 5%, 40 000–60 000 kr → 9%, 60 000–90 000 kr → 14%.",
+        "status": "active",
+        "priority": 100,
+        "startDate": "2024-01-01",
+        "endDate": null,
+        "conditions": [
+          {
+            "id": "min-cart-total",
+            "type": "cart_total",
+            "operator": ">=",
+            "value": 2000000,
+            "label": "Minst 20 000 kr i varukorgen"
+          }
+        ],
+        "actions": [
+          {
+            "id": "volymrabatt-tiers",
+            "type": "tiered_discount",
+            "value": 0,
+            "config": {
+              "tiers": [
+                { "minTotal": 2000000, "maxTotal": 4000000, "percent": 5 },
+                { "minTotal": 4000000, "maxTotal": 6000000, "percent": 9 },
+                { "minTotal": 6000000, "maxTotal": 9000000, "percent": 14 }
+              ]
+            },
+            "label": "Volymrabatt 5–14%"
+          }
+        ],
+        "usageCount": 0,
+        "createdAt": "2024-01-01T00:00:00Z",
+        "updatedAt": "2024-01-01T00:00:00Z",
+        "createdBy": "mats.tornberg@gmail.com",
+        "tags": ["volume", "volymrabatt", "test"]
+      }
+    ]
+  }
+}

deployment/deployment-no.yaml

@@ -1,276 +0,0 @@
-apiVersion: v1
-kind: Secret
-metadata:
-  name:  klarna-api-credentials
-data:
-  username: ZjQzZDY3YjEtNzA2Yy00NTk2LTliNTgtYjg1YjU2NDEwZTUw
-  password: a2xhcm5hX3Rlc3RfYXBpX0trUWhWVE5yYVZsV2FsTnhTRVp3Y1ZSSFF5UkVNRmxyY25Kd1AxSndQMGdzWmpRelpEWTNZakV0TnpBMll5MDBOVGsyTFRsaU5UZ3RZamcxWWpVMk5ERXdaVFV3TERFc2JUUkNjRFpWU1RsTllsSk1aMlEyVEc4MmRVODNZMkozUlRaaFdEZDViV3AwYkhGV1JqTjVNQzlaYXow
-type: Opaque
----
-apiVersion: apps/v1
-kind: Deployment
-metadata:
-  labels:
-    app: cart-actor
-    arch: amd64
-  name: cart-actor-x86
-spec:
-  replicas: 0
-  selector:
-    matchLabels:
-      app: cart-actor
-      arch: amd64
-  template:
-    metadata:
-      labels:
-        app: cart-actor
-        actor-pool: cart
-        arch: amd64
-    spec:
-      affinity:
-        nodeAffinity:
-          requiredDuringSchedulingIgnoredDuringExecution:
-            nodeSelectorTerms:
-              - matchExpressions:
-                - key: kubernetes.io/arch
-                  operator: NotIn
-                  values:
-                    - arm64
-      volumes:
-        - name: data
-          nfs:
-            path: /i-data/7a8af061/nfs/cart-actor-no
-            server: 10.10.1.10
-      imagePullSecrets:
-        - name: regcred
-      serviceAccountName: default
-      containers:
-        - image: registry.knatofs.se/go-cart-actor-amd64:latest
-          name: cart-actor-amd64
-          imagePullPolicy: Always
-          lifecycle:
-            preStop:
-              exec:
-                command: ["sleep", "15"]
-          ports:
-            - containerPort: 8080
-              name: web
-            - containerPort: 1234
-              name: echo
-            - containerPort: 1337
-              name: rpc
-            - containerPort: 1338
-              name: quorum
-          livenessProbe:
-            httpGet:
-              path: /livez
-              port: web
-            failureThreshold: 1
-            periodSeconds: 10
-          readinessProbe:
-            httpGet:
-              path: /readyz
-              port: web
-            failureThreshold: 2
-            initialDelaySeconds: 2
-            periodSeconds: 10
-          volumeMounts:
-            - mountPath: "/data"
-              name: data
-          resources:
-            limits:
-              memory: "768Mi"
-            requests:
-              memory: "70Mi"
-              cpu: "1200m"
-          env:
-            - name: TZ
-              value: "Europe/Stockholm"
-            - name: KLARNA_API_USERNAME
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: username
-            - name: KLARNA_API_PASSWORD
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: password
-            - name: POD_IP
-              valueFrom:
-                fieldRef:
-                  fieldPath: status.podIP
-            - name: AMQP_URL
-              value: "amqp://admin:12bananer@rabbitmq.dev:5672/"
-            - name: BASE_URL
-              value: "https://s10n-no.tornberg.me"
-            - name: CART_BASE_URL
-              value: "https://cart-no.tornberg.me"
-            - name: POD_NAME
-              valueFrom:
-                fieldRef:
-                  fieldPath: metadata.name
----
-apiVersion: apps/v1
-kind: Deployment
-metadata:
-  labels:
-    app: cart-actor
-    arch: arm64
-  name: cart-actor-arm64
-spec:
-  replicas: 3
-  selector:
-    matchLabels:
-      app: cart-actor
-      arch: arm64
-  template:
-    metadata:
-      labels:
-        app: cart-actor
-        actor-pool: cart
-        arch: arm64
-    spec:
-      affinity:
-        nodeAffinity:
-          requiredDuringSchedulingIgnoredDuringExecution:
-            nodeSelectorTerms:
-              - matchExpressions:
-                - key: kubernetes.io/hostname
-                  operator: NotIn
-                  values:
-                    - masterpi
-                - key: kubernetes.io/arch
-                  operator: In
-                  values:
-                    - arm64
-      volumes:
-        - name: data
-          nfs:
-            path: /i-data/7a8af061/nfs/cart-actor-no
-            server: 10.10.1.10
-      imagePullSecrets:
-        - name: regcred
-      serviceAccountName: default
-      containers:
-        - image: registry.knatofs.se/go-cart-actor:latest
-          name: cart-actor-arm64
-          imagePullPolicy: Always
-          lifecycle:
-            preStop:
-              exec:
-                command: ["sleep", "15"]
-          ports:
-            - containerPort: 8080
-              name: web
-            - containerPort: 1234
-              name: echo
-            - containerPort: 1337
-              name: rpc
-            - containerPort: 1338
-              name: quorum
-          livenessProbe:
-            httpGet:
-              path: /livez
-              port: web
-            failureThreshold: 1
-            periodSeconds: 10
-          readinessProbe:
-            httpGet:
-              path: /readyz
-              port: web
-            failureThreshold: 2
-            initialDelaySeconds: 2
-            periodSeconds: 10
-          volumeMounts:
-            - mountPath: "/data"
-              name: data
-          resources:
-            limits:
-              memory: "768Mi"
-            requests:
-              memory: "70Mi"
-              cpu: "1200m"
-          env:
-            - name: TZ
-              value: "Europe/Stockholm"
-            - name: KLARNA_API_USERNAME
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: username
-            - name: KLARNA_API_PASSWORD
-              valueFrom:
-                secretKeyRef:
-                  name: klarna-api-credentials
-                  key: password
-            - name: POD_IP
-              valueFrom:
-                fieldRef:
-                  fieldPath: status.podIP
-            - name: AMQP_URL
-              value: "amqp://admin:12bananer@rabbitmq.dev:5672/"
-            - name: BASE_URL
-              value: "https://s10n-no.tornberg.me"
-            - name: CART_BASE_URL
-              value: "https://cart-no.tornberg.me"
-            - name: POD_NAME
-              valueFrom:
-                fieldRef:
-                  fieldPath: metadata.name
----
-kind: Service
-apiVersion: v1
-metadata:
-  name: cart-echo
-spec:
-  selector:
-    app: cart-actor
-  type: LoadBalancer
-  ports:
-    - name: echo
-      port: 1234
----
-kind: Service
-apiVersion: v1
-metadata:
-  name: cart-actor
-  annotations:
-    prometheus.io/port: "8080"
-    prometheus.io/scrape: "true"
-    prometheus.io/path: "/metrics"
-spec:
-  selector:
-    app: cart-actor
-  ports:
-    - name: web
-      port: 8080
----
-apiVersion: networking.k8s.io/v1
-kind: Ingress
-metadata:
-  name: cart-ingress
-  annotations:
-    cert-manager.io/cluster-issuer: letsencrypt-prod
-    # nginx.ingress.kubernetes.io/affinity: "cookie"
-    # nginx.ingress.kubernetes.io/session-cookie-name: "cart-affinity"
-    # nginx.ingress.kubernetes.io/session-cookie-expires: "172800"
-    # nginx.ingress.kubernetes.io/session-cookie-max-age: "172800"
-    nginx.ingress.kubernetes.io/proxy-body-size: 4m
-spec:
-  ingressClassName: nginx
-  tls:
-    - hosts:
-        - cart-no.tornberg.me
-      secretName: cart-actor-no-tls-secret
-  rules:
-    - host: cart-no.tornberg.me
-      http:
-        paths:
-          - path: /
-            pathType: Prefix
-            backend:
-              service:
-                name: cart-actor
-                port:
-                  number: 8080

deployment/deployment.yaml

@@ -9,13 +9,117 @@ type: Opaque
 ---
 apiVersion: apps/v1
 kind: Deployment
+metadata:
+  labels:
+    app: cart-backoffice
+    arch: amd64
+  name: cart-backoffice-x86
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: cart-backoffice
+      arch: amd64
+  template:
+    metadata:
+      labels:
+        app: cart-backoffice
+        arch: amd64
+    spec:
+      affinity:
+        nodeAffinity:
+          requiredDuringSchedulingIgnoredDuringExecution:
+            nodeSelectorTerms:
+              - matchExpressions:
+                  - key: kubernetes.io/arch
+                    operator: NotIn
+                    values:
+                      - arm64
+      volumes:
+        - name: data
+          nfs:
+            path: /i-data/7a8af061/nfs/
+            server: 10.10.1.10
+      serviceAccountName: default
+      containers:
+        - image: registry.k6n.net/go-cart-actor-amd64:latest
+          name: cart-actor-amd64
+          imagePullPolicy: Always
+          command: ["/go-cart-backoffice"]
+          lifecycle:
+            preStop:
+              exec:
+                command: ["sleep", "15"]
+          ports:
+            - containerPort: 8080
+              name: web
+          livenessProbe:
+            httpGet:
+              path: /livez
+              port: web
+            failureThreshold: 1
+            periodSeconds: 30
+          readinessProbe:
+            httpGet:
+              path: /readyz
+              port: web
+            failureThreshold: 2
+            initialDelaySeconds: 2
+            periodSeconds: 30
+          volumeMounts:
+            - mountPath: "/data"
+              name: data
+          resources:
+            limits:
+              memory: "768Mi"
+            requests:
+              memory: "70Mi"
+              cpu: "1200m"
+          env:
+            - name: CART_DIR
+              value: "/data/cart-actor"
+            - name: CHECKOUT_DIR
+              value: "/data/checkout-actor"
+            - name: TZ
+              value: "Europe/Stockholm"
+            - name: REDIS_ADDRESS
+              value: "10.10.3.18:6379"
+            - name: REDIS_PASSWORD
+              value: "slaskredis"
+            - name: ADYEN_HMAC
+              valueFrom:
+                secretKeyRef:
+                  name: adyen
+                  key: HMAC
+            - name: ADYEN_API_KEY
+              valueFrom:
+                secretKeyRef:
+                  name: adyen
+                  key: API_KEY
+            - name: KLARNA_API_USERNAME
+              valueFrom:
+                secretKeyRef:
+                  name: klarna-api-credentials
+                  key: username
+            - name: KLARNA_API_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: klarna-api-credentials
+                  key: password
+            - name: AMQP_URL
+              value: "amqp://admin:12bananer@rabbitmq.dev:5672/"
+            # - name: BASE_URL
+            #   value: "https://s10n-no.tornberg.me"
+---
+apiVersion: apps/v1
+kind: Deployment
 metadata:
   labels:
     app: cart-actor
     arch: amd64
   name: cart-actor-x86
 spec:
-  replicas: 0
+  replicas: 3
   selector:
     matchLabels:
       app: cart-actor
@@ -41,11 +145,9 @@ spec:
           nfs:
             path: /i-data/7a8af061/nfs/cart-actor
             server: 10.10.1.10
-      imagePullSecrets:
-        - name: regcred
       serviceAccountName: default
       containers:
-        - image: registry.knatofs.se/go-cart-actor-amd64:latest
+        - image: registry.k6n.net/go-cart-actor-amd64:latest
           name: cart-actor-amd64
           imagePullPolicy: Always
           lifecycle:
@@ -55,25 +157,23 @@ spec:
           ports:
             - containerPort: 8080
               name: web
-            - containerPort: 1234
+            - containerPort: 8081
-              name: echo
+              name: debug
             - containerPort: 1337
               name: rpc
-            - containerPort: 1338
-              name: quorum
           livenessProbe:
             httpGet:
               path: /livez
               port: web
             failureThreshold: 1
-            periodSeconds: 10
+            periodSeconds: 30
           readinessProbe:
             httpGet:
               path: /readyz
               port: web
             failureThreshold: 2
             initialDelaySeconds: 2
-            periodSeconds: 10
+            periodSeconds: 50
           volumeMounts:
             - mountPath: "/data"
               name: data
@@ -84,6 +184,10 @@ spec:
               memory: "70Mi"
               cpu: "1200m"
           env:
+            - name: CART_DIR
+              value: "/data/cart-actor"
+            - name: CHECKOUT_DIR
+              value: "/data/checkout-actor"
             - name: TZ
               value: "Europe/Stockholm"
             - name: KLARNA_API_USERNAME
@@ -91,6 +195,24 @@ spec:
                 secretKeyRef:
                   name: klarna-api-credentials
                   key: username
+            - name: REDIS_ADDRESS
+              value: "10.10.3.18:6379"
+            - name: REDIS_PASSWORD
+              value: "slaskredis"
+            - name: OTEL_RESOURCE_ATTRIBUTES
+              value: "service.name=cart,service.version=0.1.2"
+            - name: OTEL_EXPORTER_OTLP_ENDPOINT
+              value: "http://otel-debug-service.monitoring:4317"
+            - name: ADYEN_HMAC
+              valueFrom:
+                secretKeyRef:
+                  name: adyen
+                  key: HMAC
+            - name: ADYEN_API_KEY
+              valueFrom:
+                secretKeyRef:
+                  name: adyen
+                  key: API_KEY
             - name: KLARNA_API_PASSWORD
               valueFrom:
                 secretKeyRef:
@@ -147,11 +269,9 @@ spec:
           nfs:
             path: /i-data/7a8af061/nfs/cart-actor
             server: 10.10.1.10
-      imagePullSecrets:
-        - name: regcred
       serviceAccountName: default
       containers:
-        - image: registry.knatofs.se/go-cart-actor:latest
+        - image: registry.k6n.net/go-cart-actor:latest
           name: cart-actor-arm64
           imagePullPolicy: Always
           lifecycle:
@@ -161,25 +281,23 @@ spec:
           ports:
             - containerPort: 8080
               name: web
-            - containerPort: 1234
+            - containerPort: 8081
-              name: echo
+              name: debug
             - containerPort: 1337
               name: rpc
-            - containerPort: 1338
-              name: quorum
           livenessProbe:
             httpGet:
               path: /livez
               port: web
             failureThreshold: 1
-            periodSeconds: 10
+            periodSeconds: 15
           readinessProbe:
             httpGet:
               path: /readyz
               port: web
             failureThreshold: 2
             initialDelaySeconds: 2
-            periodSeconds: 10
+            periodSeconds: 15
           volumeMounts:
             - mountPath: "/data"
               name: data
@@ -192,6 +310,24 @@ spec:
           env:
             - name: TZ
               value: "Europe/Stockholm"
+            - name: REDIS_ADDRESS
+              value: "redis.home:6379"
+            - name: REDIS_PASSWORD
+              value: "slaskredis"
+            - name: OTEL_RESOURCE_ATTRIBUTES
+              value: "service.name=cart,service.version=0.1.2"
+            - name: OTEL_EXPORTER_OTLP_ENDPOINT
+              value: "http://otel-debug-service.monitoring:4317"
+            - name: ADYEN_HMAC
+              valueFrom:
+                secretKeyRef:
+                  name: adyen
+                  key: HMAC
+            - name: ADYEN_API_KEY
+              valueFrom:
+                secretKeyRef:
+                  name: adyen
+                  key: API_KEY
             - name: KLARNA_API_USERNAME
               valueFrom:
                 secretKeyRef:
@@ -217,22 +353,10 @@ spec:
 ---
 kind: Service
 apiVersion: v1
-metadata:
-  name: cart-echo
-spec:
-  selector:
-    app: cart-actor
-  type: LoadBalancer
-  ports:
-    - name: echo
-      port: 1234
----
-kind: Service
-apiVersion: v1
 metadata:
   name: cart-actor
   annotations:
-    prometheus.io/port: "8080"
+    prometheus.io/port: "8081"
     prometheus.io/scrape: "true"
     prometheus.io/path: "/metrics"
 spec:
@@ -241,6 +365,151 @@ spec:
   ports:
     - name: web
       port: 8080
+    - name: internal
+      port: 8081
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app: checkout-actor
+    arch: amd64
+  name: checkout-actor-x86
+spec:
+  replicas: 3
+  selector:
+    matchLabels:
+      app: checkout-actor
+      arch: amd64
+  template:
+    metadata:
+      labels:
+        app: checkout-actor
+        actor-pool: checkout
+        arch: amd64
+    spec:
+      affinity:
+        nodeAffinity:
+          requiredDuringSchedulingIgnoredDuringExecution:
+            nodeSelectorTerms:
+              - matchExpressions:
+                  - key: kubernetes.io/arch
+                    operator: NotIn
+                    values:
+                      - arm64
+      volumes:
+        - name: data
+          nfs:
+            path: /i-data/7a8af061/nfs/checkout-actor
+            server: 10.10.1.10
+      serviceAccountName: default
+      containers:
+        - image: registry.k6n.net/go-cart-actor-amd64:latest
+          name: checkout-actor-amd64
+          imagePullPolicy: Always
+          command: ["/go-checkout-actor"]
+          lifecycle:
+            preStop:
+              exec:
+                command: ["sleep", "15"]
+          ports:
+            - containerPort: 8080
+              name: web
+            - containerPort: 8081
+              name: debug
+            - containerPort: 1337
+              name: rpc
+          livenessProbe:
+            httpGet:
+              path: /livez
+              port: web
+            failureThreshold: 1
+            periodSeconds: 15
+          readinessProbe:
+            httpGet:
+              path: /readyz
+              port: web
+            failureThreshold: 2
+            initialDelaySeconds: 1
+            periodSeconds: 15
+          volumeMounts:
+            - mountPath: "/data"
+              name: data
+          resources:
+            limits:
+              memory: "768Mi"
+            requests:
+              memory: "70Mi"
+              cpu: "1200m"
+          env:
+            - name: TZ
+              value: "Europe/Stockholm"
+            - name: REDIS_ADDRESS
+              value: "10.10.3.18:6379"
+            - name: REDIS_PASSWORD
+              value: "slaskredis"
+            - name: OTEL_RESOURCE_ATTRIBUTES
+              value: "service.name=checkout,service.version=0.1.2"
+            - name: OTEL_EXPORTER_OTLP_ENDPOINT
+              value: "http://otel-debug-service.monitoring:4317"
+            - name: ADYEN_HMAC
+              valueFrom:
+                secretKeyRef:
+                  name: adyen
+                  key: HMAC
+            - name: ADYEN_API_KEY
+              valueFrom:
+                secretKeyRef:
+                  name: adyen
+                  key: API_KEY
+            - name: KLARNA_API_USERNAME
+              valueFrom:
+                secretKeyRef:
+                  name: klarna-api-credentials
+                  key: username
+            - name: KLARNA_API_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: klarna-api-credentials
+                  key: password
+            - name: POD_IP
+              valueFrom:
+                fieldRef:
+                  fieldPath: status.podIP
+            - name: AMQP_URL
+              value: "amqp://admin:12bananer@rabbitmq.dev:5672/"
+            - name: CART_INTERNAL_URL
+              value: "http://cart-actor:8080"
+            - name: POD_NAME
+              valueFrom:
+                fieldRef:
+                  fieldPath: metadata.name
+---
+kind: Service
+apiVersion: v1
+metadata:
+  name: checkout-actor
+  annotations:
+    prometheus.io/port: "8081"
+    prometheus.io/scrape: "true"
+    prometheus.io/path: "/metrics"
+spec:
+  selector:
+    app: checkout-actor
+  ports:
+    - name: web
+      port: 8080
+---
+kind: Service
+apiVersion: v1
+metadata:
+  name: cart-backoffice
+spec:
+  selector:
+    app: cart-backoffice
+  ports:
+    - name: web
+      port: 8080
 ---
 apiVersion: networking.k8s.io/v1
 kind: Ingress
@@ -248,19 +517,19 @@ metadata:
   name: cart-ingress
   annotations:
     cert-manager.io/cluster-issuer: letsencrypt-prod
-    # nginx.ingress.kubernetes.io/affinity: "cookie"
+    nginx.ingress.kubernetes.io/affinity: "cookie"
-    # nginx.ingress.kubernetes.io/session-cookie-name: "cart-affinity"
+    nginx.ingress.kubernetes.io/session-cookie-name: "cart-affinity"
-    # nginx.ingress.kubernetes.io/session-cookie-expires: "172800"
+    nginx.ingress.kubernetes.io/session-cookie-expires: "172800"
-    # nginx.ingress.kubernetes.io/session-cookie-max-age: "172800"
+    nginx.ingress.kubernetes.io/session-cookie-max-age: "172800"
     nginx.ingress.kubernetes.io/proxy-body-size: 4m
 spec:
   ingressClassName: nginx
   tls:
     - hosts:
-        - cart.tornberg.me
+        - cart.k6n.net
       secretName: cart-actor-tls-secret
   rules:
-    - host: cart.tornberg.me
+    - host: cart.k6n.net
       http:
         paths:
           - path: /
@@ -270,3 +539,123 @@ spec:
                 name: cart-actor
                 port:
                   number: 8080
+          - path: /api/checkout
+            pathType: Prefix
+            backend:
+              service:
+                name: checkout-actor
+                port:
+                  number: 8080
+          - path: /payment
+            pathType: Prefix
+            backend:
+              service:
+                name: checkout-actor
+                port:
+                  number: 8080
+---
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: cart-backend-ingress
+  annotations:
+    cert-manager.io/cluster-issuer: letsencrypt-prod
+spec:
+  ingressClassName: nginx
+  tls:
+    - hosts:
+        - slask-cart.k6n.net
+      secretName: cart-backoffice-actor-tls-secret
+  rules:
+    - host: slask-cart.k6n.net
+      http:
+        paths:
+          - path: /
+            pathType: Prefix
+            backend:
+              service:
+                name: cart-backoffice
+                port:
+                  number: 8080
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app: cart-inventory
+    arch: amd64
+  name: cart-inventory-x86
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: cart-inventory
+      arch: amd64
+  template:
+    metadata:
+      labels:
+        app: cart-inventory
+        arch: amd64
+    spec:
+      affinity:
+        nodeAffinity:
+          requiredDuringSchedulingIgnoredDuringExecution:
+            nodeSelectorTerms:
+              - matchExpressions:
+                  - key: kubernetes.io/arch
+                    operator: NotIn
+                    values:
+                      - arm64
+      serviceAccountName: default
+      containers:
+        - image: registry.k6n.net/go-cart-actor-amd64:latest
+          name: cart-inventory-amd64
+          imagePullPolicy: Always
+          command: ["/go-cart-inventory"]
+          lifecycle:
+            preStop:
+              exec:
+                command: ["sleep", "15"]
+          ports:
+            - containerPort: 8080
+              name: web
+          livenessProbe:
+            httpGet:
+              path: /livez
+              port: web
+            failureThreshold: 1
+            periodSeconds: 30
+          readinessProbe:
+            httpGet:
+              path: /readyz
+              port: web
+            failureThreshold: 2
+            initialDelaySeconds: 2
+            periodSeconds: 30
+          resources:
+            limits:
+              memory: "256Mi"
+              cpu: "500m"
+            requests:
+              memory: "50Mi"
+              cpu: "500m"
+          env:
+            - name: TZ
+              value: "Europe/Stockholm"
+            - name: RABBIT_HOST
+              value: amqp://admin:12bananer@rabbitmq.s10n:5672/
+            - name: REDIS_ADDRESS
+              value: "redis.home:6379"
+            - name: REDIS_PASSWORD
+              value: "slaskredis"
+---
+kind: Service
+apiVersion: v1
+metadata:
+  name: inventory
+spec:
+  selector:
+    app: cart-inventory
+  ports:
+    - name: web
+      port: 8080

deployment/scaling.yaml

@@ -1,4 +1,4 @@
-apiVersion: autoscaling/v1
+apiVersion: autoscaling/v2
 kind: HorizontalPodAutoscaler
 metadata:
     name: cart-scaler-amd
@@ -9,9 +9,47 @@ spec:
         name: cart-actor-x86
     minReplicas: 3
     maxReplicas: 9
-  targetCPUUtilizationPercentage: 30
+    behavior:
+        scaleUp:
+            stabilizationWindowSeconds: 60
+            policies:
+                - type: Percent
+                  value: 100
+                  periodSeconds: 60
+        scaleDown:
+            stabilizationWindowSeconds: 180
+            policies:
+                - type: Percent
+                  value: 50
+                  periodSeconds: 60
+    metrics:
+        - type: Resource
+          resource:
+              name: cpu
+              target:
+                  type: Utilization
+                  averageUtilization: 50
+        # Future custom metric (example):
+        # - type: Pods
+        #   pods:
+        #     metric:
+        #       name: cart_mutations_per_second
+        #     target:
+        #       type: AverageValue
+        #       averageValue: "15"
+        # - type: Object
+        #   object:
+        #     describedObject:
+        #       apiVersion: networking.k8s.io/v1
+        #       kind: Ingress
+        #       name: cart-ingress
+        #     metric:
+        #       name: http_requests_per_second
+        #     target:
+        #       type: Value
+        #       value: "100"
 ---
-apiVersion: autoscaling/v1
+apiVersion: autoscaling/v2
 kind: HorizontalPodAutoscaler
 metadata:
     name: cart-scaler-arm
@@ -22,4 +60,42 @@ spec:
         name: cart-actor-arm64
     minReplicas: 3
     maxReplicas: 9
-  targetCPUUtilizationPercentage: 30
+    behavior:
+        scaleUp:
+            stabilizationWindowSeconds: 60
+            policies:
+                - type: Percent
+                  value: 100
+                  periodSeconds: 60
+        scaleDown:
+            stabilizationWindowSeconds: 180
+            policies:
+                - type: Percent
+                  value: 50
+                  periodSeconds: 60
+    metrics:
+        - type: Resource
+          resource:
+              name: cpu
+              target:
+                  type: Utilization
+                  averageUtilization: 50
+        # Future custom metric (example):
+        # - type: Pods
+        #   pods:
+        #     metric:
+        #       name: cart_mutations_per_second
+        #     target:
+        #       type: AverageValue
+        #       averageValue: "15"
+        # - type: Object
+        #   object:
+        #     describedObject:
+        #       apiVersion: networking.k8s.io/v1
+        #       kind: Ingress
+        #       name: cart-ingress
+        #     metric:
+        #       name: http_requests_per_second
+        #     target:
+        #       type: Value
+        #       value: "100"

discarded-host.go

@@ -1,84 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"log"
-	"net"
-	"sync"
-	"time"
-)
-
-type DiscardedHost struct {
-	Host  string
-	Tries int
-}
-
-type DiscardedHostHandler struct {
-	mu           sync.RWMutex
-	port         int
-	hosts        []*DiscardedHost
-	onConnection *func(string)
-}
-
-func (d *DiscardedHostHandler) run() {
-	for range time.Tick(time.Second) {
-		d.mu.RLock()
-		lst := make([]*DiscardedHost, 0, len(d.hosts))
-		for _, host := range d.hosts {
-			if host.Tries >= 0 && host.Tries < 5 {
-				go d.testConnection(host)
-				lst = append(lst, host)
-			} else {
-				if host.Tries > 0 {
-					log.Printf("Host %s discarded after %d tries", host.Host, host.Tries)
-				}
-			}
-		}
-		d.mu.RUnlock()
-		d.mu.Lock()
-		d.hosts = lst
-		d.mu.Unlock()
-	}
-
-}
-
-func (d *DiscardedHostHandler) testConnection(host *DiscardedHost) {
-	addr := fmt.Sprintf("%s:%d", host.Host, d.port)
-	conn, err := net.Dial("tcp", addr)
-
-	if err != nil {
-		host.Tries++
-		if host.Tries >= 5 {
-			// Exceeded retry threshold; will be dropped by run loop.
-		}
-	} else {
-		conn.Close()
-		if d.onConnection != nil {
-			fn := *d.onConnection
-			fn(host.Host)
-		}
-	}
-}
-
-func NewDiscardedHostHandler(port int) *DiscardedHostHandler {
-	ret := &DiscardedHostHandler{
-		hosts: make([]*DiscardedHost, 0),
-		port:  port,
-	}
-	go ret.run()
-	return ret
-}
-
-func (d *DiscardedHostHandler) SetReconnectHandler(fn func(string)) {
-	d.onConnection = &fn
-}
-
-func (d *DiscardedHostHandler) AppendHost(host string) {
-	d.mu.Lock()
-	defer d.mu.Unlock()
-	log.Printf("Adding host %s to retry list", host)
-	d.hosts = append(d.hosts, &DiscardedHost{
-		Host:  host,
-		Tries: 0,
-	})
-}

discovery.go

@@ -1,77 +0,0 @@
-package main
-
-import (
-	"context"
-
-	v1 "k8s.io/api/core/v1"
-	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
-	"k8s.io/apimachinery/pkg/watch"
-	"k8s.io/client-go/kubernetes"
-	"k8s.io/client-go/tools/cache"
-	toolsWatch "k8s.io/client-go/tools/watch"
-)
-
-type Discovery interface {
-	Discover() ([]string, error)
-	Watch() (<-chan HostChange, error)
-}
-
-type K8sDiscovery struct {
-	ctx    context.Context
-	client *kubernetes.Clientset
-}
-
-func (k *K8sDiscovery) Discover() ([]string, error) {
-	return k.DiscoverInNamespace("")
-}
-func (k *K8sDiscovery) DiscoverInNamespace(namespace string) ([]string, error) {
-	pods, err := k.client.CoreV1().Pods(namespace).List(k.ctx, metav1.ListOptions{
-		LabelSelector: "actor-pool=cart",
-	})
-	if err != nil {
-		return nil, err
-	}
-	hosts := make([]string, 0, len(pods.Items))
-	for _, pod := range pods.Items {
-		hosts = append(hosts, pod.Status.PodIP)
-	}
-	return hosts, nil
-}
-
-type HostChange struct {
-	Host string
-	Type watch.EventType
-}
-
-func (k *K8sDiscovery) Watch() (<-chan HostChange, error) {
-	timeout := int64(30)
-	watcherFn := func(options metav1.ListOptions) (watch.Interface, error) {
-		return k.client.CoreV1().Pods("").Watch(k.ctx, metav1.ListOptions{
-			LabelSelector:  "actor-pool=cart",
-			TimeoutSeconds: &timeout,
-		})
-	}
-	watcher, err := toolsWatch.NewRetryWatcher("1", &cache.ListWatch{WatchFunc: watcherFn})
-	if err != nil {
-		return nil, err
-	}
-	ch := make(chan HostChange)
-	go func() {
-		for event := range watcher.ResultChan() {
-
-			pod := event.Object.(*v1.Pod)
-			ch <- HostChange{
-				Host: pod.Status.PodIP,
-				Type: event.Type,
-			}
-		}
-	}()
-	return ch, nil
-}
-
-func NewK8sDiscovery(client *kubernetes.Clientset) *K8sDiscovery {
-	return &K8sDiscovery{
-		ctx:    context.Background(),
-		client: client,
-	}
-}

disk-storage.go

@@ -1,119 +0,0 @@
-package main
-
-import (
-	"encoding/gob"
-	"fmt"
-	"log"
-	"os"
-	"time"
-)
-
-type DiskStorage struct {
-	stateFile string
-	lastSave  int64
-	LastSaves map[CartId]int64
-}
-
-func NewDiskStorage(stateFile string) (*DiskStorage, error) {
-	ret := &DiskStorage{
-		stateFile: stateFile,
-		LastSaves: make(map[CartId]int64),
-	}
-	err := ret.loadState()
-	return ret, err
-}
-
-func saveMessages(messages []StorableMessage, id CartId) error {
-
-	if len(messages) == 0 {
-		return nil
-	}
-	log.Printf("%d messages to save for grain id %s", len(messages), id)
-	var file *os.File
-	var err error
-	path := getCartPath(id.String())
-	file, err = os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
-	if err != nil {
-		return err
-	}
-	defer file.Close()
-
-	for _, m := range messages {
-		err := m.Write(file)
-		if err != nil {
-			return err
-		}
-	}
-	return err
-}
-
-func getCartPath(id string) string {
-	return fmt.Sprintf("data/%s.prot", id)
-}
-
-func loadMessages(grain Grain, id CartId) error {
-	var err error
-	path := getCartPath(id.String())
-
-	file, err := os.Open(path)
-	if err != nil {
-		if os.IsNotExist(err) {
-			return nil
-		}
-		return err
-	}
-	defer file.Close()
-
-	for err == nil {
-		var msg Message
-		err = ReadMessage(file, &msg)
-		if err == nil {
-			grain.HandleMessage(&msg, true)
-		}
-	}
-
-	if err.Error() == "EOF" {
-		return nil
-	}
-	return err
-}
-
-func (s *DiskStorage) saveState() error {
-	tmpFile := s.stateFile + "_tmp"
-	file, err := os.Create(tmpFile)
-	if err != nil {
-		return err
-	}
-	defer file.Close()
-	err = gob.NewEncoder(file).Encode(s.LastSaves)
-	if err != nil {
-		return err
-	}
-	os.Remove(s.stateFile + ".bak")
-	os.Rename(s.stateFile, s.stateFile+".bak")
-	return os.Rename(tmpFile, s.stateFile)
-}
-
-func (s *DiskStorage) loadState() error {
-	file, err := os.Open(s.stateFile)
-	if err != nil {
-		return err
-	}
-	defer file.Close()
-	return gob.NewDecoder(file).Decode(&s.LastSaves)
-}
-
-func (s *DiskStorage) Store(id CartId, grain *CartGrain) error {
-	lastSavedMessage, ok := s.LastSaves[id]
-	if ok && lastSavedMessage > grain.GetLastChange() {
-		return nil
-	}
-	err := saveMessages(grain.GetStorageMessage(lastSavedMessage), id)
-	if err != nil {
-		return err
-	}
-	ts := time.Now().Unix()
-	s.LastSaves[id] = ts
-	s.lastSave = ts
-	return nil
-}

frames.go

@@ -1,102 +0,0 @@
-package main
-
-// Minimal frame abstractions retained after removal of the legacy TCP/frame
-// networking layer. These types remain only to avoid a wide cascading refactor
-// across existing grain / pool logic that still constructs and passes
-// FrameWithPayload objects internally.
-//
-// The original responsibilities this replaces:
-//   - Binary framing, checksums, network IO
-//   - Distinction between request / reply frame types
-//
-// What remains:
-//   - A light weight container (FrameWithPayload) used as an in‑process
-//     envelope for status code + typed marker + payload bytes (JSON or proto).
-//   - Message / status constants referenced in existing code paths.
-//
-// Recommended future cleanup (post‑migration):
-//   - Remove FrameType entirely and replace with enumerated semantic results
-//     or error values.
-//   - Replace FrameWithPayload with a struct { Status int; Data []byte }.
-//   - Remove remote_* reply type branching once all callers rely on gRPC
-//     status + strongly typed responses.
-//
-// For now we keep this minimal surface to keep the gRPC migration focused.
-
-type (
-	// FrameType is a symbolic identifier carried through existing code paths.
-	// No ordering or bit semantics are required anymore.
-	FrameType  uint32
-	StatusCode uint32
-)
-
-type Frame struct {
-	Type       FrameType
-	StatusCode StatusCode
-	Length     uint32
-	// Checksum retained for compatibility; no longer validated.
-	Checksum uint32
-}
-
-// FrameWithPayload wraps a Frame with an opaque payload.
-// Payload usually contains JSON encoded cart state or an error message.
-type FrameWithPayload struct {
-	Frame
-	Payload []byte
-}
-
-// -----------------------------------------------------------------------------
-// Legacy Frame Type Constants (minimal subset still referenced)
-// -----------------------------------------------------------------------------
-const (
-	RemoteGetState            = FrameType(0x01)
-	RemoteHandleMutation      = FrameType(0x02)
-	ResponseBody              = FrameType(0x03) // (rarely used; kept for completeness)
-	RemoteGetStateReply       = FrameType(0x04)
-	RemoteHandleMutationReply = FrameType(0x05)
-	RemoteCreateOrderReply    = FrameType(0x06)
-)
-
-// MakeFrameWithPayload constructs an in‑process frame wrapper.
-// Length & Checksum are filled for backward compatibility (no validation logic
-// depends on the checksum anymore).
-func MakeFrameWithPayload(msg FrameType, statusCode StatusCode, payload []byte) FrameWithPayload {
-	length := uint32(len(payload))
-	return FrameWithPayload{
-		Frame: Frame{
-			Type:       msg,
-			StatusCode: statusCode,
-			Length:     length,
-			Checksum:   (uint32(msg) + uint32(statusCode) + length) / 8, // simple legacy formula
-		},
-		Payload: payload,
-	}
-}
-
-// Clone creates a shallow copy of the frame, duplicating the payload slice.
-func (f *FrameWithPayload) Clone() *FrameWithPayload {
-	if f == nil {
-		return nil
-	}
-	cp := make([]byte, len(f.Payload))
-	copy(cp, f.Payload)
-	return &FrameWithPayload{
-		Frame:   f.Frame,
-		Payload: cp,
-	}
-}
-
-// NewErrorFrame helper for creating an error frame with a textual payload.
-func NewErrorFrame(msg FrameType, code StatusCode, err error) FrameWithPayload {
-	var b []byte
-	if err != nil {
-		b = []byte(err.Error())
-	}
-	return MakeFrameWithPayload(msg, code, b)
-}
-
-// IsSuccess returns true if the status code indicates success in the
-// conventional HTTP style range (200–299). This mirrors previous usage patterns.
-func (f *FrameWithPayload) IsSuccess() bool {
-	return f != nil && f.StatusCode >= 200 && f.StatusCode < 300
-}

go.mod

@@ -1,73 +1,116 @@
-module git.tornberg.me/go-cart-actor
+module git.k6n.net/mats/go-cart-actor
 
-go 1.25.1
+go 1.26.2
 
 require (
+	github.com/adyen/adyen-go-api-library/v21 v21.1.0
 	github.com/google/uuid v1.6.0
-	github.com/matst80/slask-finder v0.0.0-20251009175145-ce05aff5a548
 	github.com/prometheus/client_golang v1.23.2
-	github.com/rabbitmq/amqp091-go v1.10.0
+	github.com/rabbitmq/amqp091-go v1.11.0
-	google.golang.org/grpc v1.76.0
+	github.com/redis/go-redis/v9 v9.20.0
-	google.golang.org/protobuf v1.36.10
+	go.opentelemetry.io/contrib/bridges/otelslog v0.19.0
-	k8s.io/api v0.34.1
+	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.69.0
-	k8s.io/apimachinery v0.34.1
+	go.opentelemetry.io/otel v1.44.0
-	k8s.io/client-go v0.34.1
+	go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc v0.20.0
+	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc v1.44.0
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.44.0
+	go.opentelemetry.io/otel/log v0.20.0
+	go.opentelemetry.io/otel/metric v1.44.0
+	go.opentelemetry.io/otel/sdk v1.44.0
+	go.opentelemetry.io/otel/sdk/log v0.20.0
+	go.opentelemetry.io/otel/sdk/metric v1.44.0
+	go.opentelemetry.io/otel/trace v1.44.0
+	google.golang.org/grpc v1.81.1
+	google.golang.org/protobuf v1.36.11
+	k8s.io/api v0.34.2
+	k8s.io/apimachinery v0.34.2
+	k8s.io/client-go v0.34.2
 )
 
 require (
-	github.com/RoaringBitmap/roaring/v2 v2.10.0 // indirect
+	github.com/RoaringBitmap/roaring/v2 v2.18.2 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
-	github.com/bits-and-blooms/bitset v1.24.0 // indirect
+	github.com/bits-and-blooms/bitset v1.24.4 // indirect
+	github.com/cenkalti/backoff/v5 v5.0.3 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
+	github.com/dprotaso/go-yit v0.0.0-20251117151522-da16f3077589 // indirect
 	github.com/emicklei/go-restful/v3 v3.13.0 // indirect
+	github.com/felixge/httpsnoop v1.0.4 // indirect
 	github.com/fxamacker/cbor/v2 v2.9.0 // indirect
+	github.com/getkin/kin-openapi v0.133.0 // indirect
 	github.com/go-logr/logr v1.4.3 // indirect
-	github.com/go-openapi/jsonpointer v0.22.1 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
-	github.com/go-openapi/jsonreference v0.21.2 // indirect
+	github.com/go-openapi/jsonpointer v0.22.3 // indirect
-	github.com/go-openapi/swag v0.25.1 // indirect
+	github.com/go-openapi/jsonreference v0.21.3 // indirect
-	github.com/go-openapi/swag/cmdutils v0.25.1 // indirect
+	github.com/go-openapi/swag v0.25.4 // indirect
-	github.com/go-openapi/swag/conv v0.25.1 // indirect
+	github.com/go-openapi/swag/cmdutils v0.25.4 // indirect
-	github.com/go-openapi/swag/fileutils v0.25.1 // indirect
+	github.com/go-openapi/swag/conv v0.25.4 // indirect
-	github.com/go-openapi/swag/jsonname v0.25.1 // indirect
+	github.com/go-openapi/swag/fileutils v0.25.4 // indirect
-	github.com/go-openapi/swag/jsonutils v0.25.1 // indirect
+	github.com/go-openapi/swag/jsonname v0.25.4 // indirect
-	github.com/go-openapi/swag/loading v0.25.1 // indirect
+	github.com/go-openapi/swag/jsonutils v0.25.4 // indirect
-	github.com/go-openapi/swag/mangling v0.25.1 // indirect
+	github.com/go-openapi/swag/loading v0.25.4 // indirect
-	github.com/go-openapi/swag/netutils v0.25.1 // indirect
+	github.com/go-openapi/swag/mangling v0.25.4 // indirect
-	github.com/go-openapi/swag/stringutils v0.25.1 // indirect
+	github.com/go-openapi/swag/netutils v0.25.4 // indirect
-	github.com/go-openapi/swag/typeutils v0.25.1 // indirect
+	github.com/go-openapi/swag/stringutils v0.25.4 // indirect
-	github.com/go-openapi/swag/yamlutils v0.25.1 // indirect
+	github.com/go-openapi/swag/typeutils v0.25.4 // indirect
+	github.com/go-openapi/swag/yamlutils v0.25.4 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
-	github.com/google/gnostic-models v0.7.0 // indirect
+	github.com/google/gnostic-models v0.7.1 // indirect
 	github.com/google/go-cmp v0.7.0 // indirect
 	github.com/gorilla/schema v1.4.1 // indirect
+	github.com/grpc-ecosystem/grpc-gateway/v2 v2.29.0 // indirect
+	github.com/josharian/intern v1.0.0 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/mailru/easyjson v0.9.1 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.3-0.20250322232337-35a7c28c31ee // indirect
+	github.com/mohae/deepcopy v0.0.0-20170929034955-c48cc78d4826 // indirect
 	github.com/mschoch/smat v0.2.0 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
-	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/oapi-codegen/oapi-codegen/v2 v2.5.1 // indirect
+	github.com/oasdiff/yaml v0.0.0-20250309154309-f31be36b4037 // indirect
+	github.com/oasdiff/yaml3 v0.0.0-20250309153720-d2182401db90 // indirect
+	github.com/perimeterx/marshmallow v1.1.5 // indirect
+	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
 	github.com/prometheus/client_model v0.6.2 // indirect
-	github.com/prometheus/common v0.67.1 // indirect
+	github.com/prometheus/common v0.68.0 // indirect
-	github.com/prometheus/procfs v0.17.0 // indirect
+	github.com/prometheus/procfs v0.20.1 // indirect
-	github.com/spf13/pflag v1.0.6 // indirect
+	github.com/speakeasy-api/jsonpath v0.6.2 // indirect
+	github.com/speakeasy-api/openapi-overlay v0.10.3 // indirect
+	github.com/spf13/pflag v1.0.10 // indirect
+	github.com/vmware-labs/yaml-jsonpath v0.3.2 // indirect
+	github.com/woodsbury/decimal128 v1.4.0 // indirect
 	github.com/x448/float16 v0.8.4 // indirect
-	go.yaml.in/yaml/v2 v2.4.3 // indirect
+	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.44.0 // indirect
+	go.opentelemetry.io/proto/otlp v1.10.0 // indirect
+	go.uber.org/atomic v1.11.0 // indirect
+	go.yaml.in/yaml/v2 v2.4.4 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
-	golang.org/x/net v0.46.0 // indirect
+	go.yaml.in/yaml/v4 v4.0.0-rc.3 // indirect
-	golang.org/x/oauth2 v0.32.0 // indirect
+	golang.org/x/mod v0.35.0 // indirect
-	golang.org/x/sys v0.37.0 // indirect
+	golang.org/x/net v0.55.0 // indirect
-	golang.org/x/term v0.36.0 // indirect
+	golang.org/x/oauth2 v0.36.0 // indirect
-	golang.org/x/text v0.30.0 // indirect
+	golang.org/x/sync v0.20.0 // indirect
-	golang.org/x/time v0.14.0 // indirect
+	golang.org/x/sys v0.45.0 // indirect
-	google.golang.org/genproto/googleapis/rpc v0.0.0-20251007200510-49b9836ed3ff // indirect
+	golang.org/x/term v0.43.0 // indirect
+	golang.org/x/text v0.37.0 // indirect
+	golang.org/x/time v0.15.0 // indirect
+	golang.org/x/tools v0.44.0 // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20260526163538-3dc84a4a5aaa // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20260526163538-3dc84a4a5aaa // indirect
 	gopkg.in/evanphx/json-patch.v4 v4.13.0 // indirect
 	gopkg.in/inf.v0 v0.9.1 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 	k8s.io/klog/v2 v2.130.1 // indirect
-	k8s.io/kube-openapi v0.0.0-20250910181357-589584f1c912 // indirect
+	k8s.io/kube-openapi v0.0.0-20251125145642-4e65d59e963e // indirect
 	k8s.io/utils v0.0.0-20251002143259-bc988d571ff4 // indirect
 	sigs.k8s.io/json v0.0.0-20250730193827-2d320260d730 // indirect
 	sigs.k8s.io/randfill v1.0.0 // indirect
-	sigs.k8s.io/structured-merge-diff/v6 v6.3.0 // indirect
+	sigs.k8s.io/structured-merge-diff/v6 v6.3.1 // indirect
 	sigs.k8s.io/yaml v1.6.0 // indirect
 )
+
+tool github.com/oapi-codegen/oapi-codegen/v2/cmd/oapi-codegen

go.sum

@@ -1,62 +1,89 @@
-github.com/RoaringBitmap/roaring/v2 v2.10.0 h1:HbJ8Cs71lfCJyvmSptxeMX2PtvOC8yonlU0GQcy2Ak0=
+github.com/RoaringBitmap/roaring/v2 v2.18.2 h1:oPq3Cgx//iDuJQVp6xSInAKW34J9CEwE5GmLI2z+Eic=
-github.com/RoaringBitmap/roaring/v2 v2.10.0/go.mod h1:FiJcsfkGje/nZBZgCu0ZxCPOKD/hVXDS2dXi7/eUFE0=
+github.com/RoaringBitmap/roaring/v2 v2.18.2/go.mod h1:eq4wdNXxtJIS/oikeCzdX1rBzek7ANzbth041hrU8Q4=
+github.com/adyen/adyen-go-api-library/v21 v21.1.0 h1:QIKtn99yoBdt2R4PhuMdmY/DTm6Ex5HYd0cB7Sh3y6Y=
+github.com/adyen/adyen-go-api-library/v21 v21.1.0/go.mod h1:qsAGYetm761eDAz+f2OQoY4qC+tKNhZOHil1b4FO5zE=
+github.com/alicebob/miniredis/v2 v2.35.0 h1:QwLphYqCEAo1eu1TqPRN2jgVMPBweeQcR21jeqDCONI=
+github.com/alicebob/miniredis/v2 v2.35.0/go.mod h1:TcL7YfarKPGDAthEtl5NBeHZfeUQj6OXMm/+iu5cLMM=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
-github.com/bits-and-blooms/bitset v1.12.0/go.mod h1:7hO7Gc7Pp1vODcmWvKMRA9BNmbv6a/7QIWpPxHddWR8=
+github.com/bits-and-blooms/bitset v1.24.4 h1:95H15Og1clikBrKr/DuzMXkQzECs1M6hhoGXLwLQOZE=
-github.com/bits-and-blooms/bitset v1.24.0 h1:H4x4TuulnokZKvHLfzVRTHJfFfnHEeSYJizujEZvmAM=
+github.com/bits-and-blooms/bitset v1.24.4/go.mod h1:7hO7Gc7Pp1vODcmWvKMRA9BNmbv6a/7QIWpPxHddWR8=
-github.com/bits-and-blooms/bitset v1.24.0/go.mod h1:7hO7Gc7Pp1vODcmWvKMRA9BNmbv6a/7QIWpPxHddWR8=
+github.com/bsm/ginkgo/v2 v2.12.0 h1:Ny8MWAHyOepLGlLKYmXG4IEkioBysk6GpaRTLC8zwWs=
+github.com/bsm/ginkgo/v2 v2.12.0/go.mod h1:SwYbGRRDovPVboqFv0tPTcG1sN61LM1Z4ARdbAV9g4c=
+github.com/bsm/gomega v1.27.10 h1:yeMWxP2pV2fG3FgAODIY8EiRE3dy0aeFYt4l7wh6yKA=
+github.com/bsm/gomega v1.27.10/go.mod h1:JyEr/xRbxbtgWNi8tIEVPUYZ5Dzef52k01W3YH0H+O0=
+github.com/cenkalti/backoff/v5 v5.0.3 h1:ZN+IMa753KfX5hd8vVaMixjnqRZ3y8CuJKRKj1xcsSM=
+github.com/cenkalti/backoff/v5 v5.0.3/go.mod h1:rkhZdG3JZukswDf7f0cwqPNk4K0sa+F97BxZthm/crw=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
 github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dprotaso/go-yit v0.0.0-20191028211022-135eb7262960/go.mod h1:9HQzr9D/0PGwMEbC3d5AB7oi67+h4TsQqItC1GVYG58=
+github.com/dprotaso/go-yit v0.0.0-20251117151522-da16f3077589 h1:VJ/jVUWr+r4MQA7U/cscbbXRuwh1PfPCUUItYAjlKN4=
+github.com/dprotaso/go-yit v0.0.0-20251117151522-da16f3077589/go.mod h1:IeI20psFPeg2n1jxwbkYCmkpYsXsJqB7qmoqCIlX80s=
 github.com/emicklei/go-restful/v3 v3.13.0 h1:C4Bl2xDndpU6nJ4bc1jXd+uTmYPVUwkD6bFY/oTyCes=
 github.com/emicklei/go-restful/v3 v3.13.0/go.mod h1:6n3XBCmQQb25CM2LCACGz8ukIrRry+4bhvbpWn3mrbc=
+github.com/felixge/httpsnoop v1.0.4 h1:NFTV2Zj1bL4mc9sqWACXbQFVBBg2W3GPvqp8/ESS2Wg=
+github.com/felixge/httpsnoop v1.0.4/go.mod h1:m8KPJKqk1gH5J9DgRY2ASl2lWCfGKXixSwevea8zH2U=
+github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
+github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S9k=
+github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
 github.com/fxamacker/cbor/v2 v2.9.0 h1:NpKPmjDBgUfBms6tr6JZkTHtfFGcMKsw3eGcmD/sapM=
 github.com/fxamacker/cbor/v2 v2.9.0/go.mod h1:vM4b+DJCtHn+zz7h3FFp/hDAI9WNWCsZj23V5ytsSxQ=
+github.com/getkin/kin-openapi v0.133.0 h1:pJdmNohVIJ97r4AUFtEXRXwESr8b0bD721u/Tz6k8PQ=
+github.com/getkin/kin-openapi v0.133.0/go.mod h1:boAciF6cXk5FhPqe/NQeBTeenbjqU4LhWBf09ILVvWE=
+github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
 github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
 github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
 github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
-github.com/go-openapi/jsonpointer v0.22.1 h1:sHYI1He3b9NqJ4wXLoJDKmUmHkWy/L7rtEo92JUxBNk=
+github.com/go-openapi/jsonpointer v0.22.3 h1:dKMwfV4fmt6Ah90zloTbUKWMD+0he+12XYAsPotrkn8=
-github.com/go-openapi/jsonpointer v0.22.1/go.mod h1:pQT9OsLkfz1yWoMgYFy4x3U5GY5nUlsOn1qSBH5MkCM=
+github.com/go-openapi/jsonpointer v0.22.3/go.mod h1:0lBbqeRsQ5lIanv3LHZBrmRGHLHcQoOXQnf88fHlGWo=
-github.com/go-openapi/jsonreference v0.21.2 h1:Wxjda4M/BBQllegefXrY/9aq1fxBA8sI5M/lFU6tSWU=
+github.com/go-openapi/jsonreference v0.21.3 h1:96Dn+MRPa0nYAR8DR1E03SblB5FJvh7W6krPI0Z7qMc=
-github.com/go-openapi/jsonreference v0.21.2/go.mod h1:pp3PEjIsJ9CZDGCNOyXIQxsNuroxm8FAJ/+quA0yKzQ=
+github.com/go-openapi/jsonreference v0.21.3/go.mod h1:RqkUP0MrLf37HqxZxrIAtTWW4ZJIK1VzduhXYBEeGc4=
-github.com/go-openapi/swag v0.25.1 h1:6uwVsx+/OuvFVPqfQmOOPsqTcm5/GkBhNwLqIR916n8=
+github.com/go-openapi/swag v0.25.4 h1:OyUPUFYDPDBMkqyxOTkqDYFnrhuhi9NR6QVUvIochMU=
-github.com/go-openapi/swag v0.25.1/go.mod h1:bzONdGlT0fkStgGPd3bhZf1MnuPkf2YAys6h+jZipOo=
+github.com/go-openapi/swag v0.25.4/go.mod h1:zNfJ9WZABGHCFg2RnY0S4IOkAcVTzJ6z2Bi+Q4i6qFQ=
-github.com/go-openapi/swag/cmdutils v0.25.1 h1:nDke3nAFDArAa631aitksFGj2omusks88GF1VwdYqPY=
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go.work

@@ -0,0 +1,7 @@
+go 1.26.2
+
+use (
+	.
+	../slask-finder
+	../go-redis-inventory
+)

go.work.sum

@@ -0,0 +1,163 @@
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+github.com/peterbourgon/diskv v2.0.1+incompatible/go.mod h1:uqqh8zWWbv1HBMNONnaR/tNboyR3/BZd58JJSHlUSCU=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/rogpeppe/fastuuid v1.2.0/go.mod h1:jVj6XXZzXRy/MSR5jhDC/2q6DgLz+nrA6LYCDYWNEvQ=
+github.com/spf13/afero v1.15.0/go.mod h1:NC2ByUVxtQs4b3sIUphxK0NioZnmxgyCrfzeuq8lxMg=
+github.com/spf13/cobra v1.7.0/go.mod h1:uLxZILRyS/50WlhOIKD7W6V5bgeIt+4sICxh6uRMrb0=
+github.com/xhit/go-str2duration/v2 v2.1.0/go.mod h1:ohY8p+0f07DiV6Em5LKB0s2YpLtXVyJfNt1+BlmyAsU=
+github.com/zeebo/assert v1.3.0/go.mod h1:Pq9JiuJQpG8JLJdtkwrJESF0Foym2/D9XMU5ciN/wJ0=
+github.com/zeebo/errs v1.4.0/go.mod h1:sgbWHsvVuTPHcqJJGQ1WhI5KbWlHYz+2+2C/LSEtCw4=
+go.opencensus.io v0.24.0/go.mod h1:vNK8G9p7aAivkbmorf4v+7Hgx+Zs0yY+0fOtgBfjQKo=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/telemetry v0.0.0-20260409153401-be6f6cb8b1fa/go.mod h1:kHjTxDEnAu6/Nl9lDkzjWpR+bmKfxeiRuSDlsMb70gE=
+golang.org/x/tools/go/expect v0.1.0-deprecated/go.mod h1:eihoPOH+FgIqa3FpoTwguz/bVUSGBlGQU67vpBeOrBY=
+golang.org/x/tools/go/packages/packagestest v0.1.1-deprecated/go.mod h1:RVAQXBGNv1ib0J382/DPCRS/BPnsGebyM1Gj5VSDpG8=
+google.golang.org/appengine v1.6.8/go.mod h1:1jJ3jBArFh5pcgW8gCtRJnepW8FzD1V44FJffLiz/Ds=
+google.golang.org/genproto/googleapis/bytestream v0.0.0-20260523011958-0a33c5d7ca68/go.mod h1:6TABGosqSqU2l1+fJ3jdvOYPPVryeKybxYF0cCZkTBE=
+google.golang.org/grpc/examples v0.0.0-20250407062114-b368379ef8f6/go.mod h1:6ytKWczdvnpnO+m+JiG9NjEDzR1FJfsnmJdG7B8QVZ8=
+gotest.tools/gotestsum v1.12.3/go.mod h1:Y1+e0Iig4xIRtdmYbEV7K7H6spnjc1fX4BOuUhWw2Wk=
+k8s.io/gengo/v2 v2.0.0-20250604051438-85fd79dbfd9f/go.mod h1:EJykeLsmFC60UQbYJezXkEsG2FLrt0GPNkU5iK5GWxU=

grafana_dashboard_cart.json

@@ -0,0 +1,327 @@
+{
+  "uid": "cart-actors",
+  "title": "Cart Actor Cluster",
+  "timezone": "browser",
+  "refresh": "30s",
+  "schemaVersion": 38,
+  "version": 1,
+  "editable": true,
+  "graphTooltip": 0,
+  "panels": [
+    {
+      "type": "row",
+      "title": "Overview",
+      "gridPos": { "x": 0, "y": 0, "w": 24, "h": 1 },
+      "id": 1,
+      "collapsed": false
+    },
+    {
+      "type": "stat",
+      "title": "Active Grains",
+      "id": 2,
+      "gridPos": { "x": 0, "y": 1, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "cart_active_grains" }
+      ],
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "center",
+        "reduceOptions": { "calcs": ["lastNotNull"], "fields": "", "values": false }
+      }
+    },
+    {
+      "type": "stat",
+      "title": "Grains In Pool",
+      "id": 3,
+      "gridPos": { "x": 6, "y": 1, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "cart_grains_in_pool" }
+      ],
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "center",
+        "reduceOptions": { "calcs": ["lastNotNull"], "fields": "", "values": false }
+      }
+    },
+    {
+      "type": "stat",
+      "title": "Pool Usage %",
+      "id": 4,
+      "gridPos": { "x": 12, "y": 1, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "cart_grain_pool_usage * 100" }
+      ],
+      "units": "percent",
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "center",
+        "reduceOptions": { "calcs": ["lastNotNull"] }
+      }
+    },
+    {
+      "type": "stat",
+      "title": "Connected Remotes",
+      "id": 5,
+      "gridPos": { "x": 18, "y": 1, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "connected_remotes" }
+      ],
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "center",
+        "reduceOptions": { "calcs": ["lastNotNull"] }
+      }
+    },
+
+    {
+      "type": "row",
+      "title": "Mutations",
+      "gridPos": { "x": 0, "y": 5, "w": 24, "h": 1 },
+      "id": 6,
+      "collapsed": false
+    },
+    {
+      "type": "timeseries",
+      "title": "Mutation Rate (1m)",
+      "id": 7,
+      "gridPos": { "x": 0, "y": 6, "w": 12, "h": 8 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "rate(cart_mutations_total[1m])", "legendFormat": "mutations/s" },
+        { "refId": "B", "expr": "rate(cart_mutation_failures_total[1m])", "legendFormat": "failures/s" }
+      ],
+      "fieldConfig": { "defaults": { "unit": "ops" } }
+    },
+    {
+      "type": "stat",
+      "title": "Failure % (5m)",
+      "id": 8,
+      "gridPos": { "x": 12, "y": 6, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        {
+          "refId": "A",
+          "expr": "100 * (increase(cart_mutation_failures_total[5m]) / clamp_max(increase(cart_mutations_total[5m]), 1))"
+        }
+      ],
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "center",
+        "reduceOptions": { "calcs": ["lastNotNull"] }
+      }
+    },
+    {
+      "type": "timeseries",
+      "title": "Mutation Latency Quantiles",
+      "id": 9,
+      "gridPos": { "x": 18, "y": 6, "w": 6, "h": 8 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        {
+          "refId": "A",
+          "expr": "histogram_quantile(0.50, sum(rate(cart_mutation_latency_seconds_bucket[5m])) by (le))",
+          "legendFormat": "p50"
+        },
+        {
+          "refId": "B",
+          "expr": "histogram_quantile(0.90, sum(rate(cart_mutation_latency_seconds_bucket[5m])) by (le))",
+          "legendFormat": "p90"
+        },
+        {
+          "refId": "C",
+          "expr": "histogram_quantile(0.99, sum(rate(cart_mutation_latency_seconds_bucket[5m])) by (le))",
+          "legendFormat": "p99"
+        }
+      ],
+      "fieldConfig": { "defaults": { "unit": "s" } }
+    },
+
+    {
+      "type": "row",
+      "title": "Event Log",
+      "gridPos": { "x": 0, "y": 14, "w": 24, "h": 1 },
+      "id": 10,
+      "collapsed": false
+    },
+    {
+      "type": "timeseries",
+      "title": "Event Append Rate (5m)",
+      "id": 11,
+      "gridPos": { "x": 0, "y": 15, "w": 8, "h": 6 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "rate(cart_event_log_appends_total[5m])", "legendFormat": "appends/s" }
+      ]
+    },
+    {
+      "type": "timeseries",
+      "title": "Event Bytes Written Rate (5m)",
+      "id": 12,
+      "gridPos": { "x": 8, "y": 15, "w": 8, "h": 6 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "rate(cart_event_log_bytes_written_total[5m])", "legendFormat": "bytes/s" }
+      ],
+      "fieldConfig": { "defaults": { "unit": "Bps" } }
+    },
+    {
+      "type": "stat",
+      "title": "Existing Log Files",
+      "id": 13,
+      "gridPos": { "x": 16, "y": 15, "w": 4, "h": 3 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_event_log_files_existing" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Last Append Age (s)",
+      "id": 14,
+      "gridPos": { "x": 20, "y": 15, "w": 4, "h": 3 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "(time() - cart_event_log_last_append_unix)" }
+      ],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Replay Failures Total",
+      "id": 15,
+      "gridPos": { "x": 16, "y": 18, "w": 4, "h": 3 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_event_log_replay_failures_total" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Replay Duration p95 (5m)",
+      "id": 16,
+      "gridPos": { "x": 20, "y": 18, "w": 4, "h": 3 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        {
+          "refId": "A",
+            "expr": "histogram_quantile(0.95, sum(rate(cart_event_log_replay_duration_seconds_bucket[5m])) by (le))"
+        }
+      ],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] }, "fieldConfig": { "defaults": { "unit": "s" } } }
+    },
+
+    {
+      "type": "row",
+      "title": "Grain Lifecycle",
+      "gridPos": { "x": 0, "y": 21, "w": 24, "h": 1 },
+      "id": 17,
+      "collapsed": false
+    },
+    {
+      "type": "timeseries",
+      "title": "Spawn & Lookup Rates (1m)",
+      "id": 18,
+      "gridPos": { "x": 0, "y": 22, "w": 12, "h": 8 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "rate(cart_grain_spawned_total[1m])", "legendFormat": "spawns/s" },
+        { "refId": "B", "expr": "rate(cart_grain_lookups_total[1m])", "legendFormat": "lookups/s" }
+      ]
+    },
+    {
+      "type": "stat",
+      "title": "Negotiations Rate (5m)",
+      "id": 19,
+      "gridPos": { "x": 12, "y": 22, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        { "refId": "A", "expr": "rate(cart_remote_negotiation_total[5m])" }
+      ],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] }, "orientation": "horizontal" }
+    },
+    {
+      "type": "stat",
+      "title": "Mutations Total",
+      "id": 20,
+      "gridPos": { "x": 18, "y": 22, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_mutations_total" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+
+    {
+      "type": "row",
+      "title": "Event Log Errors",
+      "gridPos": { "x": 0, "y": 30, "w": 24, "h": 1 },
+      "id": 21,
+      "collapsed": false
+    },
+    {
+      "type": "stat",
+      "title": "Unknown Event Types",
+      "id": 22,
+      "gridPos": { "x": 0, "y": 31, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_event_log_unknown_types_total" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Event Mutation Errors",
+      "id": 23,
+      "gridPos": { "x": 6, "y": 31, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_event_log_mutation_errors_total" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Replay Success Total",
+      "id": 24,
+      "gridPos": { "x": 12, "y": 31, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [{ "refId": "A", "expr": "cart_event_log_replay_total" }],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] } }
+    },
+    {
+      "type": "stat",
+      "title": "Replay Duration p50 (5m)",
+      "id": 25,
+      "gridPos": { "x": 18, "y": 31, "w": 6, "h": 4 },
+      "datasource": "${DS_PROMETHEUS}",
+      "targets": [
+        {
+          "refId": "A",
+          "expr": "histogram_quantile(0.50, sum(rate(cart_event_log_replay_duration_seconds_bucket[5m])) by (le))"
+        }
+      ],
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"] }, "fieldConfig": { "defaults": { "unit": "s" } } }
+    }
+  ],
+  "templating": {
+    "list": [
+      {
+        "name": "DS_PROMETHEUS",
+        "label": "Prometheus",
+        "type": "datasource",
+        "query": "prometheus",
+        "current": { "text": "Prometheus", "value": "Prometheus" }
+      }
+    ]
+  },
+  "time": {
+    "from": "now-6h",
+    "to": "now"
+  },
+  "timepicker": {
+    "refresh_intervals": ["5s","10s","30s","1m","5m","15m","30m","1h"],
+    "time_options": ["5m","15m","30m","1h","6h","12h","24h","2d","7d"]
+  }
+}

grain-pool.go

@@ -1,168 +0,0 @@
-package main
-
-import (
-	"encoding/json"
-	"fmt"
-	"log"
-	"sync"
-	"time"
-
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promauto"
-)
-
-var (
-	poolGrains = promauto.NewGauge(prometheus.GaugeOpts{
-		Name: "cart_grains_in_pool",
-		Help: "The total number of grains in the pool",
-	})
-	poolSize = promauto.NewGauge(prometheus.GaugeOpts{
-		Name: "cart_pool_size",
-		Help: "The total number of mutations",
-	})
-	poolUsage = promauto.NewGauge(prometheus.GaugeOpts{
-		Name: "cart_grain_pool_usage",
-		Help: "The current usage of the grain pool",
-	})
-)
-
-type GrainPool interface {
-	Process(id CartId, messages ...Message) (*FrameWithPayload, error)
-	Get(id CartId) (*FrameWithPayload, error)
-}
-
-type Ttl struct {
-	Expires time.Time
-	Grain   *CartGrain
-}
-
-type GrainLocalPool struct {
-	mu       sync.RWMutex
-	grains   map[CartId]*CartGrain
-	expiry   []Ttl
-	spawn    func(id CartId) (*CartGrain, error)
-	Ttl      time.Duration
-	PoolSize int
-}
-
-func NewGrainLocalPool(size int, ttl time.Duration, spawn func(id CartId) (*CartGrain, error)) *GrainLocalPool {
-
-	ret := &GrainLocalPool{
-		spawn:    spawn,
-		grains:   make(map[CartId]*CartGrain),
-		expiry:   make([]Ttl, 0),
-		Ttl:      ttl,
-		PoolSize: size,
-	}
-
-	cartPurge := time.NewTicker(time.Minute)
-	go func() {
-		<-cartPurge.C
-		ret.Purge()
-	}()
-	return ret
-}
-
-func (p *GrainLocalPool) SetAvailable(availableWithLastChangeUnix map[CartId]int64) {
-	p.mu.Lock()
-	defer p.mu.Unlock()
-	for id := range availableWithLastChangeUnix {
-		if _, ok := p.grains[id]; !ok {
-			p.grains[id] = nil
-			p.expiry = append(p.expiry, Ttl{
-				Expires: time.Now().Add(p.Ttl),
-				Grain:   nil,
-			})
-		}
-	}
-}
-
-func (p *GrainLocalPool) Purge() {
-	lastChangeTime := time.Now().Add(-p.Ttl)
-	keepChanged := lastChangeTime.Unix()
-	p.mu.Lock()
-	defer p.mu.Unlock()
-	for i := 0; i < len(p.expiry); i++ {
-		item := p.expiry[i]
-		if item.Expires.Before(time.Now()) {
-			if item.Grain.GetLastChange() > keepChanged {
-				log.Printf("Expired item %s changed, keeping", item.Grain.GetId())
-				if i < len(p.expiry)-1 {
-					p.expiry = append(p.expiry[:i], p.expiry[i+1:]...)
-					p.expiry = append(p.expiry, item)
-				} else {
-					p.expiry = append(p.expiry[:i], item)
-				}
-
-			} else {
-				log.Printf("Item %s expired", item.Grain.GetId())
-				delete(p.grains, item.Grain.GetId())
-				if i < len(p.expiry)-1 {
-					p.expiry = append(p.expiry[:i], p.expiry[i+1:]...)
-				} else {
-					p.expiry = p.expiry[:i]
-				}
-			}
-		} else {
-			break
-		}
-	}
-}
-
-func (p *GrainLocalPool) GetGrains() map[CartId]*CartGrain {
-	return p.grains
-}
-
-func (p *GrainLocalPool) GetGrain(id CartId) (*CartGrain, error) {
-	var err error
-	// p.mu.RLock()
-	// defer p.mu.RUnlock()
-	grain, ok := p.grains[id]
-	grainLookups.Inc()
-	if grain == nil || !ok {
-		if len(p.grains) >= p.PoolSize {
-			if p.expiry[0].Expires.Before(time.Now()) {
-				delete(p.grains, p.expiry[0].Grain.GetId())
-				p.expiry = p.expiry[1:]
-			} else {
-				return nil, fmt.Errorf("pool is full")
-			}
-		}
-		grain, err = p.spawn(id)
-		p.mu.Lock()
-		p.grains[id] = grain
-		p.mu.Unlock()
-	}
-	go func() {
-		l := float64(len(p.grains))
-		ps := float64(p.PoolSize)
-		poolUsage.Set(l / ps)
-		poolGrains.Set(l)
-		poolSize.Set(ps)
-	}()
-	return grain, err
-}
-
-func (p *GrainLocalPool) Process(id CartId, messages ...Message) (*FrameWithPayload, error) {
-	grain, err := p.GetGrain(id)
-	var result *FrameWithPayload
-	if err == nil && grain != nil {
-		for _, message := range messages {
-			result, err = grain.HandleMessage(&message, false)
-		}
-	}
-	return result, err
-}
-
-func (p *GrainLocalPool) Get(id CartId) (*FrameWithPayload, error) {
-	grain, err := p.GetGrain(id)
-	if err != nil {
-		return nil, err
-	}
-	data, err := json.Marshal(grain)
-	if err != nil {
-		return nil, err
-	}
-	ret := MakeFrameWithPayload(0, 200, data)
-	return &ret, nil
-}

grpc_integration_test.go

@@ -1,135 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"context"
-	"encoding/json"
-	"fmt"
-	"testing"
-	"time"
-
-	messages "git.tornberg.me/go-cart-actor/proto"
-	"google.golang.org/grpc"
-)
-
-// TestCartActorMutationAndState validates end-to-end gRPC mutation + state retrieval
-// against a locally started gRPC server (single-node scenario).
-// This test uses AddItemType directly to avoid hitting external product
-// fetching logic (FetchItem) which would require network I/O.
-func TestCartActorMutationAndState(t *testing.T) {
-	// Setup local grain pool + synced pool (no discovery, single host)
-	pool := NewGrainLocalPool(1024, time.Minute, spawn)
-	synced, err := NewSyncedPool(pool, "127.0.0.1", nil)
-	if err != nil {
-		t.Fatalf("NewSyncedPool error: %v", err)
-	}
-
-	// Start gRPC server (CartActor + ControlPlane) on :1337
-	grpcSrv, err := StartGRPCServer(":1337", pool, synced)
-	if err != nil {
-		t.Fatalf("StartGRPCServer error: %v", err)
-	}
-	defer grpcSrv.GracefulStop()
-
-	// Dial the local server
-	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
-	defer cancel()
-	conn, err := grpc.DialContext(ctx, "127.0.0.1:1337",
-		grpc.WithInsecure(),
-		grpc.WithBlock(),
-	)
-	if err != nil {
-		t.Fatalf("grpc.Dial error: %v", err)
-	}
-	defer conn.Close()
-
-	cartClient := messages.NewCartActorClient(conn)
-
-	// Create a short cart id (<=16 chars so it fits into the fixed CartId 16-byte array cleanly)
-	cartID := fmt.Sprintf("cart-%d", time.Now().UnixNano())
-
-	// Build an AddItem payload (bypasses FetchItem to keep test deterministic)
-	addItem := &messages.AddItem{
-		ItemId:   1,
-		Quantity: 1,
-		Price:    1000,
-		OrgPrice: 1000,
-		Sku:      "test-sku",
-		Name:     "Test SKU",
-		Image:    "/img.png",
-		Stock:    2, // InStock
-		Tax:      2500,
-		Country:  "se",
-	}
-
-	// Marshal underlying mutation payload using the existing handler code path
-	handler, ok := Handlers[AddItemType]
-	if !ok {
-		t.Fatalf("Handler for AddItemType missing")
-	}
-	payloadData, err := getSerializedPayload(handler, AddItemType, addItem)
-	if err != nil {
-		t.Fatalf("serialize add item: %v", err)
-	}
-
-	// Issue Mutate RPC
-	mutResp, err := cartClient.Mutate(context.Background(), &messages.MutationRequest{
-		CartId:          cartID,
-		Type:            messages.MutationType(AddItemType),
-		Payload:         payloadData,
-		ClientTimestamp: time.Now().Unix(),
-	})
-	if err != nil {
-		t.Fatalf("Mutate RPC error: %v", err)
-	}
-	if mutResp.StatusCode != 200 {
-		t.Fatalf("Mutate returned non-200 status: %d payload=%s", mutResp.StatusCode, string(mutResp.Payload))
-	}
-
-	// Decode cart state JSON and validate
-	state := &CartGrain{}
-	if err := json.Unmarshal(mutResp.Payload, state); err != nil {
-		t.Fatalf("Unmarshal mutate cart state: %v\nPayload: %s", err, string(mutResp.Payload))
-	}
-	if len(state.Items) != 1 {
-		t.Fatalf("Expected 1 item after mutation, got %d", len(state.Items))
-	}
-	if state.Items[0].Sku != "test-sku" {
-		t.Fatalf("Unexpected item SKU: %s", state.Items[0].Sku)
-	}
-
-	// Issue GetState RPC
-	getResp, err := cartClient.GetState(context.Background(), &messages.StateRequest{
-		CartId: cartID,
-	})
-	if err != nil {
-		t.Fatalf("GetState RPC error: %v", err)
-	}
-	if getResp.StatusCode != 200 {
-		t.Fatalf("GetState returned non-200 status: %d payload=%s", getResp.StatusCode, string(getResp.Payload))
-	}
-
-	state2 := &CartGrain{}
-	if err := json.Unmarshal(getResp.Payload, state2); err != nil {
-		t.Fatalf("Unmarshal get state: %v", err)
-	}
-	if len(state2.Items) != 1 {
-		t.Fatalf("Expected 1 item in GetState, got %d", len(state2.Items))
-	}
-	if state2.Items[0].Sku != "test-sku" {
-		t.Fatalf("Unexpected SKU in GetState: %s", state2.Items[0].Sku)
-	}
-}
-
-// getSerializedPayload serializes a mutation proto using the registered handler.
-func getSerializedPayload(handler MessageHandler, msgType uint16, content interface{}) ([]byte, error) {
-	msg := &Message{
-		Type:    msgType,
-		Content: content,
-	}
-	var buf bytes.Buffer
-	if err := handler.Write(msg, &buf); err != nil {
-		return nil, err
-	}
-	return buf.Bytes(), nil
-}

grpc_server.go

@@ -1,379 +0,0 @@
-package main
-
-import (
-	"context"
-	"errors"
-	"fmt"
-	"log"
-	"net"
-	"time"
-
-	proto "git.tornberg.me/go-cart-actor/proto" // underlying generated package name is 'messages'
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promauto"
-	"google.golang.org/grpc"
-	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/status"
-)
-
-// -----------------------------------------------------------------------------
-// Metrics
-// -----------------------------------------------------------------------------
-
-var (
-	grpcMutateDuration = promauto.NewHistogram(prometheus.HistogramOpts{
-		Name:    "cart_grpc_mutate_duration_seconds",
-		Help:    "Duration of CartActor.Mutate RPCs",
-		Buckets: prometheus.DefBuckets,
-	})
-	grpcMutateErrors = promauto.NewCounter(prometheus.CounterOpts{
-		Name: "cart_grpc_mutate_errors_total",
-		Help: "Total number of failed CartActor.Mutate RPCs",
-	})
-	grpcStateDuration = promauto.NewHistogram(prometheus.HistogramOpts{
-		Name:    "cart_grpc_get_state_duration_seconds",
-		Help:    "Duration of CartActor.GetState RPCs",
-		Buckets: prometheus.DefBuckets,
-	})
-	grpcControlDuration = promauto.NewHistogram(prometheus.HistogramOpts{
-		Name:    "cart_grpc_control_duration_seconds",
-		Help:    "Duration of ControlPlane RPCs",
-		Buckets: prometheus.DefBuckets,
-	})
-	grpcControlErrors = promauto.NewCounter(prometheus.CounterOpts{
-		Name: "cart_grpc_control_errors_total",
-		Help: "Total number of failed ControlPlane RPCs",
-	})
-)
-
-// timeTrack wraps a closure and records duration into the supplied histogram.
-func timeTrack(hist prometheus.Observer, fn func() error) (err error) {
-	start := time.Now()
-	defer func() {
-		hist.Observe(time.Since(start).Seconds())
-	}()
-	return fn()
-}
-
-// -----------------------------------------------------------------------------
-// CartActor Service Implementation
-// -----------------------------------------------------------------------------
-
-type cartActorService struct {
-	proto.UnimplementedCartActorServer
-	pool GrainPool
-}
-
-func newCartActorService(pool GrainPool) *cartActorService {
-	return &cartActorService{pool: pool}
-}
-
-func (s *cartActorService) Mutate(ctx context.Context, req *proto.MutationRequest) (*proto.MutationReply, error) {
-	var reply *proto.MutationReply
-	err := timeTrack(grpcMutateDuration, func() error {
-		if req == nil {
-			return status.Error(codes.InvalidArgument, "request is nil")
-		}
-		if req.CartId == "" {
-			return status.Error(codes.InvalidArgument, "cart_id is empty")
-		}
-		mt := uint16(req.Type.Number())
-		handler, ok := Handlers[mt]
-		if !ok {
-			return status.Errorf(codes.InvalidArgument, "unknown mutation type %d", mt)
-		}
-		content, err := handler.Read(req.Payload)
-		if err != nil {
-			return status.Errorf(codes.InvalidArgument, "decode payload: %v", err)
-		}
-
-		ts := req.ClientTimestamp
-		if ts == 0 {
-			ts = time.Now().Unix()
-		}
-		msg := Message{
-			Type:      mt,
-			TimeStamp: &ts,
-			Content:   content,
-		}
-
-		frame, err := s.pool.Process(ToCartId(req.CartId), msg)
-		if err != nil {
-			return err
-		}
-		reply = &proto.MutationReply{
-			StatusCode: int32(frame.StatusCode),
-			Payload:    frame.Payload,
-		}
-		return nil
-	})
-	if err != nil {
-		grpcMutateErrors.Inc()
-		return nil, err
-	}
-	return reply, nil
-}
-
-func (s *cartActorService) GetState(ctx context.Context, req *proto.StateRequest) (*proto.StateReply, error) {
-	var reply *proto.StateReply
-	err := timeTrack(grpcStateDuration, func() error {
-		if req == nil || req.CartId == "" {
-			return status.Error(codes.InvalidArgument, "cart_id is empty")
-		}
-		frame, err := s.pool.Get(ToCartId(req.CartId))
-		if err != nil {
-			return err
-		}
-		reply = &proto.StateReply{
-			StatusCode: int32(frame.StatusCode),
-			Payload:    frame.Payload,
-		}
-		return nil
-	})
-	if err != nil {
-		return nil, err
-	}
-	return reply, nil
-}
-
-// -----------------------------------------------------------------------------
-// ControlPlane Service Implementation
-// -----------------------------------------------------------------------------
-
-// controlPlaneService directly leverages SyncedPool internals (same package).
-// NOTE: This is a transitional adapter; once the legacy frame-based code is
-// removed, related fields/methods in SyncedPool can be slimmed.
-type controlPlaneService struct {
-	proto.UnimplementedControlPlaneServer
-	pool *SyncedPool
-}
-
-func newControlPlaneService(pool *SyncedPool) *controlPlaneService {
-	return &controlPlaneService{pool: pool}
-}
-
-func (s *controlPlaneService) Ping(ctx context.Context, _ *proto.Empty) (*proto.PingReply, error) {
-	var reply *proto.PingReply
-	err := timeTrack(grpcControlDuration, func() error {
-		reply = &proto.PingReply{
-			Host:     s.pool.Hostname,
-			UnixTime: time.Now().Unix(),
-		}
-		return nil
-	})
-	if err != nil {
-		grpcControlErrors.Inc()
-		return nil, err
-	}
-	return reply, nil
-}
-
-func (s *controlPlaneService) Negotiate(ctx context.Context, req *proto.NegotiateRequest) (*proto.NegotiateReply, error) {
-	var reply *proto.NegotiateReply
-	err := timeTrack(grpcControlDuration, func() error {
-		if req == nil {
-			return status.Error(codes.InvalidArgument, "request is nil")
-		}
-		// Add unknown hosts
-		for _, host := range req.KnownHosts {
-			if host == "" || host == s.pool.Hostname {
-				continue
-			}
-			if !s.pool.IsKnown(host) {
-				go s.pool.AddRemote(host)
-			}
-		}
-		// Build healthy host list
-		hosts := make([]string, 0)
-		for _, r := range s.pool.GetHealthyRemotes() {
-			hosts = append(hosts, r.Host)
-		}
-		hosts = append(hosts, s.pool.Hostname)
-		reply = &proto.NegotiateReply{
-			Hosts: hosts,
-		}
-		return nil
-	})
-	if err != nil {
-		grpcControlErrors.Inc()
-		return nil, err
-	}
-	return reply, nil
-}
-
-func (s *controlPlaneService) GetCartIds(ctx context.Context, _ *proto.Empty) (*proto.CartIdsReply, error) {
-	var reply *proto.CartIdsReply
-	err := timeTrack(grpcControlDuration, func() error {
-		s.pool.mu.RLock()
-		defer s.pool.mu.RUnlock()
-		ids := make([]string, 0, len(s.pool.local.grains))
-		for id, g := range s.pool.local.grains {
-			if g == nil {
-				continue
-			}
-			if id.String() == "" {
-				continue
-			}
-			ids = append(ids, id.String())
-		}
-		reply = &proto.CartIdsReply{
-			CartIds: ids,
-		}
-		return nil
-	})
-	if err != nil {
-		grpcControlErrors.Inc()
-		return nil, err
-	}
-	return reply, nil
-}
-
-func (s *controlPlaneService) ConfirmOwner(ctx context.Context, req *proto.OwnerChangeRequest) (*proto.OwnerChangeAck, error) {
-	var reply *proto.OwnerChangeAck
-	err := timeTrack(grpcControlDuration, func() error {
-		if req == nil || req.CartId == "" || req.NewHost == "" {
-			return status.Error(codes.InvalidArgument, "cart_id or new_host missing")
-		}
-		id := ToCartId(req.CartId)
-		newHost := req.NewHost
-
-		// Mirror GrainOwnerChangeHandler semantics
-		log.Printf("gRPC ConfirmOwner: cart %s newHost=%s", id, newHost)
-		for _, r := range s.pool.remoteHosts {
-			if r.Host == newHost && r.IsHealthy() {
-				go s.pool.SpawnRemoteGrain(id, newHost)
-				break
-			}
-		}
-		go s.pool.AddRemote(newHost)
-
-		reply = &proto.OwnerChangeAck{
-			Accepted: true,
-			Message:  "ok",
-		}
-		return nil
-	})
-	if err != nil {
-		grpcControlErrors.Inc()
-		return nil, err
-	}
-	return reply, nil
-}
-
-func (s *controlPlaneService) Closing(ctx context.Context, notice *proto.ClosingNotice) (*proto.OwnerChangeAck, error) {
-	var reply *proto.OwnerChangeAck
-	err := timeTrack(grpcControlDuration, func() error {
-		if notice == nil || notice.Host == "" {
-			return status.Error(codes.InvalidArgument, "host missing")
-		}
-		host := notice.Host
-		s.pool.mu.RLock()
-		_, exists := s.pool.remoteHosts[host]
-		s.pool.mu.RUnlock()
-		if exists {
-			go s.pool.RemoveHost(host)
-		}
-		reply = &proto.OwnerChangeAck{
-			Accepted: true,
-			Message:  "removed",
-		}
-		return nil
-	})
-	if err != nil {
-		grpcControlErrors.Inc()
-		return nil, err
-	}
-	return reply, nil
-}
-
-// -----------------------------------------------------------------------------
-// Server Bootstrap
-// -----------------------------------------------------------------------------
-
-type GRPCServer struct {
-	server *grpc.Server
-	lis    net.Listener
-	addr   string
-}
-
-// StartGRPCServer sets up a gRPC server hosting both CartActor and ControlPlane services.
-// addr example: ":1337" (for combined) OR run two servers if you want separate ports.
-// For the migration we can host both on the same listener to reduce open ports.
-func StartGRPCServer(addr string, pool GrainPool, synced *SyncedPool, opts ...grpc.ServerOption) (*GRPCServer, error) {
-	if pool == nil {
-		return nil, errors.New("nil grain pool")
-	}
-	if synced == nil {
-		return nil, errors.New("nil synced pool")
-	}
-
-	lis, err := net.Listen("tcp", addr)
-	if err != nil {
-		return nil, fmt.Errorf("listen %s: %w", addr, err)
-	}
-
-	grpcServer := grpc.NewServer(opts...)
-	proto.RegisterCartActorServer(grpcServer, newCartActorService(pool))
-	proto.RegisterControlPlaneServer(grpcServer, newControlPlaneService(synced))
-
-	go func() {
-		log.Printf("gRPC server listening on %s", addr)
-		if serveErr := grpcServer.Serve(lis); serveErr != nil {
-			log.Printf("gRPC server stopped: %v", serveErr)
-		}
-	}()
-
-	return &GRPCServer{
-		server: grpcServer,
-		lis:    lis,
-		addr:   addr,
-	}, nil
-}
-
-// GracefulStop stops the server gracefully.
-func (s *GRPCServer) GracefulStop() {
-	if s == nil || s.server == nil {
-		return
-	}
-	s.server.GracefulStop()
-}
-
-// Addr returns the bound address.
-func (s *GRPCServer) Addr() string {
-	if s == nil {
-		return ""
-	}
-	return s.addr
-}
-
-// -----------------------------------------------------------------------------
-// Client Dial Helpers (used later by refactored remote grain + control plane)
-// -----------------------------------------------------------------------------
-
-// DialRemote establishes (or reuses externally) a gRPC client connection.
-func DialRemote(ctx context.Context, target string, opts ...grpc.DialOption) (*grpc.ClientConn, error) {
-	dialOpts := []grpc.DialOption{
-		grpc.WithInsecure(), // NOTE: Intentional for initial migration; replace with TLS / mTLS later.
-		grpc.WithBlock(),
-	}
-	dialOpts = append(dialOpts, opts...)
-	ctxDial, cancel := context.WithTimeout(ctx, 5*time.Second)
-	defer cancel()
-	conn, err := grpc.DialContext(ctxDial, target, dialOpts...)
-	if err != nil {
-		return nil, err
-	}
-	return conn, nil
-}
-
-// -----------------------------------------------------------------------------
-// Utility for converting internal errors to gRPC status (if needed later).
-// -----------------------------------------------------------------------------
-
-func grpcError(err error) error {
-	if err == nil {
-		return nil
-	}
-	// Extend mapping if we add richer error types.
-	return status.Error(codes.Internal, err.Error())
-}

internal/customerauth/customerauth_test.go

@@ -0,0 +1,95 @@
+package customerauth
+
+import (
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func TestPasswordRoundTrip(t *testing.T) {
+	h, err := HashPassword("correct horse battery staple")
+	if err != nil {
+		t.Fatalf("hash: %v", err)
+	}
+	if !VerifyPassword("correct horse battery staple", h) {
+		t.Fatal("correct password did not verify")
+	}
+	if VerifyPassword("wrong", h) {
+		t.Fatal("wrong password verified")
+	}
+}
+
+func TestPasswordHashesAreSalted(t *testing.T) {
+	a, _ := HashPassword("hunter2hunter2")
+	b, _ := HashPassword("hunter2hunter2")
+	if a == b {
+		t.Fatal("two hashes of the same password are identical — not salted")
+	}
+}
+
+func TestVerifyRejectsMalformed(t *testing.T) {
+	for _, bad := range []string{"", "x", "pbkdf2-sha256$abc$salt$hash", "md5$1$a$b"} {
+		if VerifyPassword("whatever", bad) {
+			t.Fatalf("malformed hash %q verified", bad)
+		}
+	}
+}
+
+func TestSessionRoundTrip(t *testing.T) {
+	s := NewSigner([]byte("test-secret"))
+	tok := s.Issue(12345, time.Hour)
+	id, err := s.Parse(tok)
+	if err != nil {
+		t.Fatalf("parse: %v", err)
+	}
+	if id != 12345 {
+		t.Fatalf("got id %d, want 12345", id)
+	}
+}
+
+func TestSessionExpired(t *testing.T) {
+	s := NewSigner([]byte("test-secret"))
+	tok := s.Issue(1, -time.Second)
+	if _, err := s.Parse(tok); err != ErrExpiredToken {
+		t.Fatalf("got %v, want ErrExpiredToken", err)
+	}
+}
+
+func TestSessionTamperAndWrongKey(t *testing.T) {
+	s := NewSigner([]byte("test-secret"))
+	tok := s.Issue(7, time.Hour)
+	if _, err := s.Parse(tok + "x"); err != ErrInvalidToken {
+		t.Fatalf("tampered token: got %v, want ErrInvalidToken", err)
+	}
+	other := NewSigner([]byte("different-secret"))
+	if _, err := other.Parse(tok); err != ErrInvalidToken {
+		t.Fatalf("wrong key: got %v, want ErrInvalidToken", err)
+	}
+}
+
+func TestStoreRegisterDuplicateAndReload(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "credentials.json")
+	store, err := LoadCredentialStore(path)
+	if err != nil {
+		t.Fatalf("load: %v", err)
+	}
+	if err := store.Register("User@Example.com", 42, "hash1", "ts"); err != nil {
+		t.Fatalf("register: %v", err)
+	}
+	// Duplicate (case-insensitive) is rejected.
+	if err := store.Register("user@example.com", 99, "hash2", "ts"); err != ErrEmailExists {
+		t.Fatalf("duplicate: got %v, want ErrEmailExists", err)
+	}
+	// Reload from disk and confirm the record persisted.
+	reloaded, err := LoadCredentialStore(path)
+	if err != nil {
+		t.Fatalf("reload: %v", err)
+	}
+	rec, ok := reloaded.Get("USER@EXAMPLE.COM")
+	if !ok {
+		t.Fatal("record not found after reload")
+	}
+	if rec.ProfileID != 42 || rec.Hash != "hash1" {
+		t.Fatalf("unexpected record: %+v", rec)
+	}
+}

internal/customerauth/password.go

@@ -0,0 +1,76 @@
+// Package customerauth adds password-based signup/login to the profile service.
+//
+// It deliberately uses only the standard library: PBKDF2-HMAC-SHA256 for
+// password hashing (crypto/pbkdf2, Go 1.24+) and HMAC-SHA256-signed cookies for
+// sessions (crypto/hmac). No password ever leaves the server in plaintext and
+// the session token is opaque + tamper-evident.
+package customerauth
+
+import (
+	"crypto/pbkdf2"
+	"crypto/rand"
+	"crypto/sha256"
+	"crypto/subtle"
+	"encoding/base64"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// pbkdf2Iterations is the work factor for PBKDF2-HMAC-SHA256. 210_000 matches
+// the current OWASP recommendation for PBKDF2-SHA256.
+const pbkdf2Iterations = 210_000
+
+const (
+	saltLen = 16
+	keyLen  = 32
+)
+
+// HashPassword returns an encoded PBKDF2 hash of the form
+//
+//	pbkdf2-sha256$<iterations>$<saltB64>$<hashB64>
+//
+// with a fresh random salt. The encoded string is self-describing so Verify can
+// read the parameters back without external configuration.
+func HashPassword(password string) (string, error) {
+	salt := make([]byte, saltLen)
+	if _, err := rand.Read(salt); err != nil {
+		return "", fmt.Errorf("customerauth: read salt: %w", err)
+	}
+	dk, err := pbkdf2.Key(sha256.New, password, salt, pbkdf2Iterations, keyLen)
+	if err != nil {
+		return "", fmt.Errorf("customerauth: pbkdf2: %w", err)
+	}
+	return fmt.Sprintf("pbkdf2-sha256$%d$%s$%s",
+		pbkdf2Iterations,
+		base64.RawStdEncoding.EncodeToString(salt),
+		base64.RawStdEncoding.EncodeToString(dk),
+	), nil
+}
+
+// VerifyPassword reports whether password matches the encoded hash. It is
+// constant-time in the hash comparison and returns false for any malformed
+// encoding rather than erroring, so callers can treat it as a simple predicate.
+func VerifyPassword(password, encoded string) bool {
+	parts := strings.Split(encoded, "$")
+	if len(parts) != 4 || parts[0] != "pbkdf2-sha256" {
+		return false
+	}
+	iter, err := strconv.Atoi(parts[1])
+	if err != nil || iter <= 0 {
+		return false
+	}
+	salt, err := base64.RawStdEncoding.DecodeString(parts[2])
+	if err != nil {
+		return false
+	}
+	want, err := base64.RawStdEncoding.DecodeString(parts[3])
+	if err != nil {
+		return false
+	}
+	got, err := pbkdf2.Key(sha256.New, password, salt, iter, len(want))
+	if err != nil {
+		return false
+	}
+	return subtle.ConstantTimeCompare(got, want) == 1
+}

internal/customerauth/server.go

@@ -0,0 +1,378 @@
+package customerauth
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/mail"
+	"strings"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/profile"
+	messages "git.k6n.net/mats/go-cart-actor/proto/profile"
+	"google.golang.org/protobuf/proto"
+)
+
+// minPasswordLen is the minimum accepted password length at registration.
+const minPasswordLen = 8
+
+// ProfileApplier is the subset of the profile grain pool the auth server needs.
+// The pool (and the UCP adapter's ProfileApplier) already satisfies it.
+type ProfileApplier interface {
+	Get(ctx context.Context, id uint64) (*profile.ProfileGrain, error)
+	Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*actor.MutationResult[profile.ProfileGrain], error)
+}
+
+// Server exposes password signup/login and identity-linking over HTTP, backed
+// by the credential store (email→id+hash) and the profile grain pool.
+type Server struct {
+	store   *CredentialStore
+	applier ProfileApplier
+	signer  *Signer
+	ttl     time.Duration
+}
+
+// NewServer builds an auth server. ttl<=0 falls back to DefaultSessionTTL.
+func NewServer(store *CredentialStore, applier ProfileApplier, signer *Signer, ttl time.Duration) *Server {
+	if ttl <= 0 {
+		ttl = DefaultSessionTTL
+	}
+	return &Server{store: store, applier: applier, signer: signer, ttl: ttl}
+}
+
+// Handler returns the router for the auth endpoints. Mount it under /ucp/v1/auth
+// (the prefix is stripped by the caller).
+func (s *Server) Handler() http.Handler {
+	mux := http.NewServeMux()
+	mux.HandleFunc("POST /register", s.handleRegister)
+	mux.HandleFunc("POST /login", s.handleLogin)
+	mux.HandleFunc("POST /logout", s.handleLogout)
+	mux.HandleFunc("GET /me", s.handleMe)
+	mux.HandleFunc("POST /link-cart", s.handleLinkCart)
+	mux.HandleFunc("POST /link-checkout", s.handleLinkCheckout)
+	mux.HandleFunc("POST /link-order", s.handleLinkOrder)
+	return mux
+}
+
+// ---------------------------------------------------------------------------
+// Request/response payloads
+// ---------------------------------------------------------------------------
+
+type registerRequest struct {
+	Email    string `json:"email"`
+	Password string `json:"password"`
+	Name     string `json:"name,omitempty"`
+	Phone    string `json:"phone,omitempty"`
+}
+
+type loginRequest struct {
+	Email    string `json:"email"`
+	Password string `json:"password"`
+}
+
+type linkCartRequest struct {
+	CartID string `json:"cartId"`
+}
+
+type linkCheckoutRequest struct {
+	CheckoutID string `json:"checkoutId"`
+	CartID     string `json:"cartId"`
+}
+
+type linkOrderRequest struct {
+	OrderReference string `json:"orderReference"`
+	CartID         string `json:"cartId"`
+	Status         string `json:"status,omitempty"`
+}
+
+// CustomerResponse mirrors the UCP customer projection (kept local to avoid an
+// import cycle with internal/ucp). The password hash is never included.
+type CustomerResponse struct {
+	ID        string            `json:"id"`
+	Name      string            `json:"name,omitempty"`
+	Email     string            `json:"email,omitempty"`
+	Phone     string            `json:"phone,omitempty"`
+	Language  string            `json:"language,omitempty"`
+	Currency  string            `json:"currency,omitempty"`
+	AvatarURL string            `json:"avatarUrl,omitempty"`
+	Addresses []AddressResponse `json:"addresses"`
+	Orders    []OrderRef        `json:"orders"`
+}
+
+type AddressResponse struct {
+	ID                uint32 `json:"id"`
+	Label             string `json:"label,omitempty"`
+	FullName          string `json:"fullName,omitempty"`
+	AddressLine1      string `json:"addressLine1"`
+	AddressLine2      string `json:"addressLine2,omitempty"`
+	City              string `json:"city"`
+	Zip               string `json:"zip"`
+	Country           string `json:"country"`
+	IsDefaultShipping bool   `json:"isDefaultShipping,omitempty"`
+	IsDefaultBilling  bool   `json:"isDefaultBilling,omitempty"`
+}
+
+type OrderRef struct {
+	OrderReference string `json:"orderReference"`
+	Status         string `json:"status,omitempty"`
+}
+
+// ---------------------------------------------------------------------------
+// Handlers
+// ---------------------------------------------------------------------------
+
+func (s *Server) handleRegister(w http.ResponseWriter, r *http.Request) {
+	var req registerRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeErr(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	email := NormalizeEmail(req.Email)
+	if !validEmail(email) {
+		writeErr(w, http.StatusBadRequest, "a valid email is required")
+		return
+	}
+	if len(req.Password) < minPasswordLen {
+		writeErr(w, http.StatusBadRequest, "password must be at least 8 characters")
+		return
+	}
+	if _, exists := s.store.Get(email); exists {
+		writeErr(w, http.StatusConflict, "an account with this email already exists")
+		return
+	}
+
+	hash, err := HashPassword(req.Password)
+	if err != nil {
+		writeErr(w, http.StatusInternalServerError, "could not hash password")
+		return
+	}
+
+	rawID, err := profile.NewProfileId()
+	if err != nil {
+		writeErr(w, http.StatusInternalServerError, "could not generate id")
+		return
+	}
+	id := uint64(rawID)
+
+	set := &messages.SetProfile{Email: &email}
+	if req.Name != "" {
+		set.Name = &req.Name
+	}
+	if req.Phone != "" {
+		set.Phone = &req.Phone
+	}
+	if _, err := s.applier.Apply(r.Context(), id, set); err != nil {
+		writeErr(w, http.StatusInternalServerError, "could not create profile")
+		return
+	}
+
+	// Persist the credential only after the profile is created. If this fails
+	// the profile exists but is unreachable by login — acceptable and rare.
+	if err := s.store.Register(email, id, hash, time.Now().UTC().Format(time.RFC3339)); err != nil {
+		if err == ErrEmailExists {
+			writeErr(w, http.StatusConflict, "an account with this email already exists")
+			return
+		}
+		writeErr(w, http.StatusInternalServerError, "could not store credentials")
+		return
+	}
+
+	s.issueSession(w, r, id)
+	s.writeCustomer(w, r, http.StatusCreated, rawID.String(), id)
+}
+
+func (s *Server) handleLogin(w http.ResponseWriter, r *http.Request) {
+	var req loginRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeErr(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	rec, ok := s.store.Get(req.Email)
+	// Always run a verify (even on miss, against the stored hash if present) and
+	// return a single generic error so the response does not reveal whether the
+	// email exists.
+	if !ok || !VerifyPassword(req.Password, rec.Hash) {
+		writeErr(w, http.StatusUnauthorized, "invalid email or password")
+		return
+	}
+	s.issueSession(w, r, rec.ProfileID)
+	s.writeCustomer(w, r, http.StatusOK, profile.ProfileId(rec.ProfileID).String(), rec.ProfileID)
+}
+
+func (s *Server) handleLogout(w http.ResponseWriter, r *http.Request) {
+	ClearSession(w, r)
+	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
+}
+
+func (s *Server) handleMe(w http.ResponseWriter, r *http.Request) {
+	id, ok := s.requireSession(w, r)
+	if !ok {
+		return
+	}
+	s.writeCustomer(w, r, http.StatusOK, profile.ProfileId(id).String(), id)
+}
+
+func (s *Server) handleLinkCart(w http.ResponseWriter, r *http.Request) {
+	id, ok := s.requireSession(w, r)
+	if !ok {
+		return
+	}
+	var req linkCartRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeErr(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	cartID, ok := parseBase62(req.CartID)
+	if !ok {
+		writeErr(w, http.StatusBadRequest, "invalid cartId")
+		return
+	}
+	if _, err := s.applier.Apply(r.Context(), id, &messages.LinkCart{CartId: cartID, Label: "current cart"}); err != nil {
+		writeErr(w, http.StatusInternalServerError, "could not link cart")
+		return
+	}
+	s.writeCustomer(w, r, http.StatusOK, profile.ProfileId(id).String(), id)
+}
+
+func (s *Server) handleLinkCheckout(w http.ResponseWriter, r *http.Request) {
+	id, ok := s.requireSession(w, r)
+	if !ok {
+		return
+	}
+	var req linkCheckoutRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeErr(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	checkoutID, ok := parseBase62(req.CheckoutID)
+	if !ok {
+		writeErr(w, http.StatusBadRequest, "invalid checkoutId")
+		return
+	}
+	cartID, _ := parseBase62(req.CartID)
+	if _, err := s.applier.Apply(r.Context(), id, &messages.LinkCheckout{CheckoutId: checkoutID, CartId: cartID}); err != nil {
+		writeErr(w, http.StatusInternalServerError, "could not link checkout")
+		return
+	}
+	s.writeCustomer(w, r, http.StatusOK, profile.ProfileId(id).String(), id)
+}
+
+func (s *Server) handleLinkOrder(w http.ResponseWriter, r *http.Request) {
+	id, ok := s.requireSession(w, r)
+	if !ok {
+		return
+	}
+	var req linkOrderRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeErr(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if strings.TrimSpace(req.OrderReference) == "" {
+		writeErr(w, http.StatusBadRequest, "orderReference is required")
+		return
+	}
+	cartID, _ := parseBase62(req.CartID)
+	if _, err := s.applier.Apply(r.Context(), id, &messages.LinkOrder{
+		OrderReference: req.OrderReference,
+		CartId:         cartID,
+		Status:         req.Status,
+	}); err != nil {
+		writeErr(w, http.StatusInternalServerError, "could not link order")
+		return
+	}
+	s.writeCustomer(w, r, http.StatusOK, profile.ProfileId(id).String(), id)
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+func (s *Server) issueSession(w http.ResponseWriter, r *http.Request, id uint64) {
+	SetSession(w, r, s.signer.Issue(id, s.ttl), s.ttl)
+}
+
+// requireSession reads and validates the session cookie, writing 401 on
+// failure. It returns the profile id and whether a valid session was present.
+func (s *Server) requireSession(w http.ResponseWriter, r *http.Request) (uint64, bool) {
+	c, err := r.Cookie(SessionCookieName)
+	if err != nil || c.Value == "" {
+		writeErr(w, http.StatusUnauthorized, "not authenticated")
+		return 0, false
+	}
+	id, err := s.signer.Parse(c.Value)
+	if err != nil {
+		writeErr(w, http.StatusUnauthorized, "not authenticated")
+		return 0, false
+	}
+	return id, true
+}
+
+// writeCustomer loads the profile grain and writes it as a CustomerResponse.
+func (s *Server) writeCustomer(w http.ResponseWriter, r *http.Request, status int, idStr string, id uint64) {
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeErr(w, http.StatusInternalServerError, "could not read profile")
+		return
+	}
+	writeJSON(w, status, grainToCustomer(idStr, g))
+}
+
+func grainToCustomer(id string, g *profile.ProfileGrain) CustomerResponse {
+	resp := CustomerResponse{
+		ID:        id,
+		Name:      g.Name,
+		Email:     g.Email,
+		Phone:     g.Phone,
+		Language:  g.Language,
+		Currency:  g.Currency,
+		AvatarURL: g.AvatarUrl,
+		Addresses: make([]AddressResponse, 0, len(g.Addresses)),
+		Orders:    make([]OrderRef, 0, len(g.Orders)),
+	}
+	for _, a := range g.Addresses {
+		resp.Addresses = append(resp.Addresses, AddressResponse{
+			ID:                a.Id,
+			Label:             a.Label,
+			FullName:          a.FullName,
+			AddressLine1:      a.AddressLine1,
+			AddressLine2:      a.AddressLine2,
+			City:              a.City,
+			Zip:               a.Zip,
+			Country:           a.Country,
+			IsDefaultShipping: a.IsDefaultShipping,
+			IsDefaultBilling:  a.IsDefaultBilling,
+		})
+	}
+	for _, o := range g.Orders {
+		resp.Orders = append(resp.Orders, OrderRef{OrderReference: o.OrderReference, Status: o.Status})
+	}
+	return resp
+}
+
+// parseBase62 decodes a base62 id (cart/checkout/profile share the scheme).
+func parseBase62(s string) (uint64, bool) {
+	if s == "" {
+		return 0, false
+	}
+	id, ok := profile.ParseProfileId(s)
+	return uint64(id), ok
+}
+
+func validEmail(email string) bool {
+	if email == "" {
+		return false
+	}
+	_, err := mail.ParseAddress(email)
+	return err == nil
+}
+
+func writeJSON(w http.ResponseWriter, status int, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(v)
+}
+
+func writeErr(w http.ResponseWriter, status int, msg string) {
+	writeJSON(w, status, map[string]string{"error": msg})
+}

internal/customerauth/session.go

@@ -0,0 +1,123 @@
+package customerauth
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// SessionCookieName is the name of the HttpOnly cookie that carries the signed
+// session token for a logged-in customer.
+const SessionCookieName = "sid"
+
+// DefaultSessionTTL is how long an issued session stays valid.
+const DefaultSessionTTL = 30 * 24 * time.Hour
+
+var (
+	// ErrInvalidToken is returned when a token is malformed or its signature
+	// does not verify.
+	ErrInvalidToken = errors.New("customerauth: invalid session token")
+	// ErrExpiredToken is returned when a token's signature is valid but it has
+	// passed its expiry.
+	ErrExpiredToken = errors.New("customerauth: expired session token")
+)
+
+// Signer issues and verifies session tokens using an HMAC-SHA256 key.
+type Signer struct {
+	secret []byte
+}
+
+// NewSigner returns a Signer over the given secret key bytes.
+func NewSigner(secret []byte) *Signer { return &Signer{secret: secret} }
+
+// token format: base64url(<profileID>.<expUnix>) "." base64url(hmac)
+// The payload is signed, not encrypted — it carries no secrets, only the
+// profile id and expiry, and the HMAC makes it tamper-evident.
+
+// Issue returns a signed token for profileID that expires after ttl.
+func (s *Signer) Issue(profileID uint64, ttl time.Duration) string {
+	exp := time.Now().Add(ttl).Unix()
+	payload := fmt.Sprintf("%d.%d", profileID, exp)
+	b := base64.RawURLEncoding.EncodeToString([]byte(payload))
+	return b + "." + s.sign(b)
+}
+
+// Parse verifies a token and returns the profile id it carries. It returns
+// ErrInvalidToken for a bad signature/format and ErrExpiredToken when expired.
+func (s *Signer) Parse(token string) (uint64, error) {
+	b, sig, ok := strings.Cut(token, ".")
+	if !ok || b == "" || sig == "" {
+		return 0, ErrInvalidToken
+	}
+	if !hmac.Equal([]byte(sig), []byte(s.sign(b))) {
+		return 0, ErrInvalidToken
+	}
+	raw, err := base64.RawURLEncoding.DecodeString(b)
+	if err != nil {
+		return 0, ErrInvalidToken
+	}
+	idStr, expStr, ok := strings.Cut(string(raw), ".")
+	if !ok {
+		return 0, ErrInvalidToken
+	}
+	id, err := strconv.ParseUint(idStr, 10, 64)
+	if err != nil {
+		return 0, ErrInvalidToken
+	}
+	exp, err := strconv.ParseInt(expStr, 10, 64)
+	if err != nil {
+		return 0, ErrInvalidToken
+	}
+	if time.Now().Unix() >= exp {
+		return 0, ErrExpiredToken
+	}
+	return id, nil
+}
+
+func (s *Signer) sign(b string) string {
+	mac := hmac.New(sha256.New, s.secret)
+	mac.Write([]byte(b))
+	return base64.RawURLEncoding.EncodeToString(mac.Sum(nil))
+}
+
+// SetSession writes the session cookie for token onto w. The Secure flag is set
+// when the request arrived over TLS (directly or via an https-terminating
+// proxy) so the cookie still works on plain-http localhost in dev.
+func SetSession(w http.ResponseWriter, r *http.Request, token string, ttl time.Duration) {
+	http.SetCookie(w, &http.Cookie{
+		Name:     SessionCookieName,
+		Value:    token,
+		Path:     "/",
+		HttpOnly: true,
+		Secure:   isSecure(r),
+		SameSite: http.SameSiteLaxMode,
+		Expires:  time.Now().Add(ttl),
+		MaxAge:   int(ttl.Seconds()),
+	})
+}
+
+// ClearSession expires the session cookie on w.
+func ClearSession(w http.ResponseWriter, r *http.Request) {
+	http.SetCookie(w, &http.Cookie{
+		Name:     SessionCookieName,
+		Value:    "",
+		Path:     "/",
+		HttpOnly: true,
+		Secure:   isSecure(r),
+		SameSite: http.SameSiteLaxMode,
+		MaxAge:   -1,
+	})
+}
+
+func isSecure(r *http.Request) bool {
+	if r.TLS != nil {
+		return true
+	}
+	return strings.EqualFold(r.Header.Get("X-Forwarded-Proto"), "https")
+}

internal/customerauth/store.go

@@ -0,0 +1,119 @@
+package customerauth
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+)
+
+// ErrEmailExists is returned by Register when the (normalized) email is already
+// associated with a credential record.
+var ErrEmailExists = errors.New("customerauth: email already registered")
+
+// Record is a single stored credential: which profile an email belongs to and
+// its password hash. It deliberately does not embed any profile data — the
+// profile grain remains the source of truth for that.
+type Record struct {
+	Email     string `json:"email"`
+	ProfileID uint64 `json:"profileId"`
+	Hash      string `json:"hash"`
+	CreatedAt string `json:"createdAt,omitempty"`
+}
+
+// CredentialStore is a small email→credential index persisted to a JSON file.
+// It is the email lookup that the event-sourced profile grains intentionally
+// lack. Concurrency-safe; writes are atomic (temp file + rename).
+type CredentialStore struct {
+	mu     sync.RWMutex
+	path   string
+	byMail map[string]Record // key: normalized email
+}
+
+// LoadCredentialStore opens (or initializes) the store backed by path. A
+// missing file is treated as an empty store; the file is created on first write.
+func LoadCredentialStore(path string) (*CredentialStore, error) {
+	s := &CredentialStore{path: path, byMail: make(map[string]Record)}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return s, nil
+		}
+		return nil, fmt.Errorf("customerauth: read %s: %w", path, err)
+	}
+	var records []Record
+	if len(data) > 0 {
+		if err := json.Unmarshal(data, &records); err != nil {
+			return nil, fmt.Errorf("customerauth: parse %s: %w", path, err)
+		}
+	}
+	for _, r := range records {
+		s.byMail[NormalizeEmail(r.Email)] = r
+	}
+	return s, nil
+}
+
+// NormalizeEmail lower-cases and trims an email for use as a lookup key.
+func NormalizeEmail(email string) string {
+	return strings.ToLower(strings.TrimSpace(email))
+}
+
+// Get returns the record for email and whether it exists.
+func (s *CredentialStore) Get(email string) (Record, bool) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	r, ok := s.byMail[NormalizeEmail(email)]
+	return r, ok
+}
+
+// Register adds a new credential record and persists the store. It returns
+// ErrEmailExists if the email is already taken.
+func (s *CredentialStore) Register(email string, profileID uint64, hash, createdAt string) error {
+	key := NormalizeEmail(email)
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if _, exists := s.byMail[key]; exists {
+		return ErrEmailExists
+	}
+	s.byMail[key] = Record{Email: key, ProfileID: profileID, Hash: hash, CreatedAt: createdAt}
+	return s.persistLocked()
+}
+
+// persistLocked writes the whole store to disk atomically. Caller holds s.mu.
+func (s *CredentialStore) persistLocked() error {
+	records := make([]Record, 0, len(s.byMail))
+	for _, r := range s.byMail {
+		records = append(records, r)
+	}
+	data, err := json.MarshalIndent(records, "", "  ")
+	if err != nil {
+		return fmt.Errorf("customerauth: marshal store: %w", err)
+	}
+	if dir := filepath.Dir(s.path); dir != "" {
+		if err := os.MkdirAll(dir, 0o755); err != nil {
+			return fmt.Errorf("customerauth: mkdir %s: %w", dir, err)
+		}
+	}
+	tmp, err := os.CreateTemp(filepath.Dir(s.path), ".credentials-*.tmp")
+	if err != nil {
+		return fmt.Errorf("customerauth: temp file: %w", err)
+	}
+	tmpName := tmp.Name()
+	if _, err := tmp.Write(data); err != nil {
+		tmp.Close()
+		os.Remove(tmpName)
+		return fmt.Errorf("customerauth: write temp: %w", err)
+	}
+	if err := tmp.Close(); err != nil {
+		os.Remove(tmpName)
+		return fmt.Errorf("customerauth: close temp: %w", err)
+	}
+	if err := os.Rename(tmpName, s.path); err != nil {
+		os.Remove(tmpName)
+		return fmt.Errorf("customerauth: rename temp: %w", err)
+	}
+	return nil
+}

internal/ucp/agent.go

@@ -0,0 +1,151 @@
+package ucp
+
+import (
+	"context"
+	"net/http"
+	"strings"
+)
+
+// ---------------------------------------------------------------------------
+// UCP-Agent header parsing (RFC 8941 Dictionary Structured Field)
+// ---------------------------------------------------------------------------
+
+// ucpAgentProfileKey is the context key for the UCP-Agent profile URI.
+type ucpAgentProfileKey struct{}
+
+// UCPAgentProfileFromContext returns the UCP-Agent profile URI stored in the
+// request context, or empty string if none was advertised.
+func UCPAgentProfileFromContext(ctx context.Context) string {
+	v, _ := ctx.Value(ucpAgentProfileKey{}).(string)
+	return v
+}
+
+// parseUCPAgentProfile parses a single "profile" member value from an RFC 8941
+// Dictionary Structured Field header. It only handles the string-value form:
+//
+//	UCP-Agent: profile="https://agent.example/profiles/shopping-agent.json"
+//
+// Returns the profile URI (without surrounding quotes) or empty string.
+func parseUCPAgentProfile(header string) string {
+	if header == "" {
+		return ""
+	}
+
+	// Walk the dictionary entries looking for "profile".
+	// RFC 8941 §3.1.2: Dict = ((im-key | key) value) *(SP "," ((im-key | key) value))
+	i := 0
+	bs := []byte(header)
+	n := len(bs)
+
+	for i < n {
+		// Skip whitespace.
+		for i < n && (bs[i] == ' ' || bs[i] == '\t') {
+			i++
+		}
+		if i >= n {
+			break
+		}
+
+		// Read key (im-key or key). Lowercase letters, digits, "_", "-", "*".
+		start := i
+		for i < n && isKeyChar(bs[i]) {
+			i++
+		}
+		if i == start {
+			// No key found; skip to next comma or end.
+			for i < n && bs[i] != ',' {
+				i++
+			}
+			i++ // skip comma
+			continue
+		}
+		key := string(bs[start:i])
+
+		// Check for "=" separator. RFC 8941 allows bare names (boolean true)
+		// when "=? " follows — but we only care about key=value entries.
+		if i < n && bs[i] == '=' {
+			i++ // skip '='
+
+			// Read the value. For our case it's a string (starts with '"').
+			if i < n && bs[i] == '"' {
+				i++ // skip opening quote
+				valStart := i
+				for i < n && bs[i] != '"' {
+					if bs[i] == '\\' {
+						i++ // skip escape
+					}
+					i++
+				}
+				val := string(bs[valStart:i])
+				if i < n {
+					i++ // skip closing quote
+				}
+				if strings.EqualFold(key, "profile") {
+					return val
+				}
+			}
+		}
+
+		// Skip to next comma or end.
+		for i < n && bs[i] != ',' {
+			i++
+		}
+		i++ // skip comma
+	}
+
+	return ""
+}
+
+// isKeyChar reports whether b is valid in an RFC 8941 key (lc-ltr, DIGIT, "_", "-", "*").
+func isKeyChar(b byte) bool {
+	return (b >= 'a' && b <= 'z') || (b >= '0' && b <= '9') || b == '_' || b == '-' || b == '*'
+}
+
+// WithUCPAgent is HTTP middleware that reads the UCP-Agent header from incoming
+// requests, parses it per RFC 8941, and stores the profile URI in the request
+// context so downstream handlers can inspect the calling platform's identity.
+//
+// Usage:
+//
+//	mux.Handle("/ucp/v1/carts", ucp.WithUCPAgent(ucp.CartHandler(pool)))
+func WithUCPAgent(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if profile := parseUCPAgentProfile(r.Header.Get("UCP-Agent")); profile != "" {
+			ctx := context.WithValue(r.Context(), ucpAgentProfileKey{}, profile)
+			r = r.WithContext(ctx)
+		}
+		next.ServeHTTP(w, r)
+	})
+}
+
+// DefaultUCPAgentProfile is the profile URI sent on outgoing requests from
+// this commerce platform. Override via SetDefaultUCPAgentProfile or the
+// UCP_AGENT_PROFILE environment variable at init time.
+var DefaultUCPAgentProfile = "https://cart.k6n.net/.well-known/ucp"
+
+// SetDefaultUCPAgentProfile overrides the default profile URI used for outgoing
+// UCP-Agent headers.
+func SetDefaultUCPAgentProfile(profile string) {
+	if profile != "" {
+		DefaultUCPAgentProfile = profile
+	}
+}
+
+// UCPAgentHeaderValue returns the RFC 8941 Dictionary value for the UCP-Agent
+// header, encoding the given profile URI.
+func UCPAgentHeaderValue(profile string) string {
+	if profile == "" {
+		profile = DefaultUCPAgentProfile
+	}
+	return `profile="` + profile + `"`
+}
+
+// WithUCPAgentOnRequest adds the UCP-Agent header to an outgoing HTTP request.
+// It sets the header to the default profile unless a custom profile is provided.
+func WithUCPAgentOnRequest(req *http.Request, profile ...string) {
+	p := DefaultUCPAgentProfile
+	if len(profile) > 0 && profile[0] != "" {
+		p = profile[0]
+	}
+	req.Header.Set("UCP-Agent", `profile="`+p+`"`)
+}

internal/ucp/cart.go

@@ -0,0 +1,338 @@
+package ucp
+
+import (
+	"context"
+	"encoding/json"
+	"log"
+	"net/http"
+	"sync"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	"git.k6n.net/mats/go-cart-actor/pkg/profile"
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	messages "git.k6n.net/mats/go-cart-actor/proto/cart"
+	"google.golang.org/protobuf/proto"
+)
+
+// CartServer is the UCP REST adapter over the cart grain pool.
+type CartServer struct {
+	applier        CartApplier
+	profileApplier ProfileApplier // optional; when set, links carts to customer profiles
+	newCartId      func() (cart.CartId, error)
+}
+
+// NewCartServer builds a UCP REST adapter over a cart grain pool.
+func NewCartServer(applier CartApplier) *CartServer {
+	return &CartServer{
+		applier:   applier,
+		newCartId: cart.NewCartId,
+	}
+}
+
+// SetProfileApplier enables identity linking on this server.
+func (s *CartServer) SetProfileApplier(pa ProfileApplier) {
+	s.profileApplier = pa
+}
+
+// ---------------------------------------------------------------------------
+// UCP Cart endpoints
+// ---------------------------------------------------------------------------
+
+// handleCreateCart handles POST /carts.
+func (s *CartServer) handleCreateCart(w http.ResponseWriter, r *http.Request) {
+	cid, err := s.newCartId()
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to generate cart id")
+		return
+	}
+	id := uint64(cid)
+
+	// Seed the cart grain by calling Get once (spawns if new).
+	if _, err := s.applier.Get(r.Context(), id); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to create cart: "+err.Error())
+		return
+	}
+
+	// If items were supplied, add them.
+	var req CreateCartRequest
+	hasBody := false
+	if r.ContentLength > 0 {
+		if err := json.NewDecoder(r.Body).Decode(&req); err == nil {
+			hasBody = true
+		}
+	}
+	if hasBody && len(req.Items) > 0 {
+		groups := buildItemGroups(r.Context(), req.Items, "")
+		if _, err := applyItemGroups(r.Context(), s.applier, id, groups); err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to add items: "+err.Error())
+			return
+		}
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read cart: "+err.Error())
+		return
+	}
+	writeJSON(w, http.StatusCreated, cartGrainToResponse(cid.String(), g))
+}
+
+// handleGetCart handles GET /carts/{id}.
+func (s *CartServer) handleGetCart(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseCartID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid cart id")
+		return
+	}
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusNotFound, "cart not found")
+		return
+	}
+	writeJSON(w, http.StatusOK, cartGrainToResponse(r.PathValue("id"), g))
+}
+
+// handleUpdateCart handles PUT /carts/{id}.
+func (s *CartServer) handleUpdateCart(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseCartID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid cart id")
+		return
+	}
+
+	var req UpdateCartRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body: "+err.Error())
+		return
+	}
+
+	// Clear first, then apply.
+	if _, err := s.applier.Apply(r.Context(), id, &messages.ClearCartRequest{}); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to clear cart: "+err.Error())
+		return
+	}
+
+	// Add items.
+	if len(req.Items) > 0 {
+		groups := buildItemGroups(r.Context(), req.Items, req.Country)
+		if _, err := applyItemGroups(r.Context(), s.applier, id, groups); err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to add items: "+err.Error())
+			return
+		}
+	}
+
+	// Set user ID and auto-link cart to customer profile.
+	if req.UserId != nil && *req.UserId != "" {
+		if _, err := s.applier.Apply(r.Context(), id, &messages.SetUserId{UserId: *req.UserId}); err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to set user: "+err.Error())
+			return
+		}
+
+		// Auto-link this cart to the customer's profile if identity linking is enabled.
+		if s.profileApplier != nil {
+			if pid, ok := profile.ParseProfileId(*req.UserId); ok {
+				if err := linkCartToProfile(s.profileApplier, r.Context(), uint64(pid), id); err != nil {
+					log.Printf("identity: failed to link cart %d to profile %d: %v", id, uint64(pid), err)
+				}
+			}
+		}
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read cart: "+err.Error())
+		return
+	}
+	writeJSON(w, http.StatusOK, cartGrainToResponse(r.PathValue("id"), g))
+}
+
+// handleCancelCart handles POST /carts/{id}/cancel.
+func (s *CartServer) handleCancelCart(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseCartID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid cart id")
+		return
+	}
+
+	if _, err := s.applier.Apply(r.Context(), id, &messages.ClearCartRequest{}); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to clear cart: "+err.Error())
+		return
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read cart: "+err.Error())
+		return
+	}
+	writeJSON(w, http.StatusOK, cartGrainToResponse(r.PathValue("id"), g))
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+func parseCartID(r *http.Request) (uint64, bool) {
+	raw := r.PathValue("id")
+	if raw == "" {
+		return 0, false
+	}
+	cid, ok := cart.ParseCartId(raw)
+	if !ok {
+		return 0, false
+	}
+	return uint64(cid), true
+}
+
+func cartGrainToResponse(id string, g *cart.CartGrain) CartResponse {
+	resp := CartResponse{
+		Id:    id,
+		Items: make([]CartItem, 0, len(g.Items)),
+		Totals: Totals{Currency: g.Currency},
+		Status: "active",
+	}
+	if g.CheckoutStatus != nil && *g.CheckoutStatus != "" {
+		resp.Status = string(*g.CheckoutStatus)
+	}
+
+	for _, it := range g.Items {
+		if it == nil {
+			continue
+		}
+		item := CartItem{
+			Sku:        it.Sku,
+			Quantity:   int(it.Quantity),
+			UnitPrice:  it.Price.IncVat,
+			TotalPrice: it.TotalPrice.IncVat,
+			TaxRate:    it.Tax,
+			ItemId:     it.Id,
+			Fields:     it.CustomFields,
+		}
+		if it.Meta != nil {
+			item.Name = it.Meta.Name
+			item.Image = it.Meta.Image
+		}
+		resp.Items = append(resp.Items, item)
+	}
+
+	if g.TotalPrice != nil {
+		resp.Totals.TotalIncVat = g.TotalPrice.IncVat
+		resp.Totals.TotalExVat = g.TotalPrice.ValueExVat()
+		resp.Totals.TotalVat = g.TotalPrice.TotalVat()
+	}
+	if g.TotalDiscount != nil {
+		resp.Totals.Discount = g.TotalDiscount.IncVat
+	}
+
+	return resp
+}
+
+// ---------------------------------------------------------------------------
+// Item group building (adapted from cmd/cart/pool-server.go)
+// ---------------------------------------------------------------------------
+
+type itemGroup struct {
+	parent   *messages.AddItem
+	children []*messages.AddItem
+}
+
+func buildItemGroups(_ context.Context, items []CartItemInput, _ string) []itemGroup {
+	groups := make([]itemGroup, len(items))
+	var mu sync.Mutex
+	var wg sync.WaitGroup
+	for i, itm := range items {
+		wg.Add(1)
+		go func(i int, itm CartItemInput) {
+			defer wg.Done()
+			parentMsg := buildAddItem(itm, 0)
+			mu.Lock()
+			groups[i].parent = parentMsg
+			mu.Unlock()
+			if len(itm.Children) > 0 {
+				children := make([]*messages.AddItem, len(itm.Children))
+				for j, child := range itm.Children {
+					children[j] = buildAddItem(child, parentMsg.ItemId)
+				}
+				mu.Lock()
+				groups[i].children = children
+				mu.Unlock()
+			}
+		}(i, itm)
+	}
+	wg.Wait()
+	return groups
+}
+
+func buildAddItem(input CartItemInput, parentItemId uint32) *messages.AddItem {
+	qty := int32(input.Quantity)
+	if qty <= 0 {
+		qty = 1
+	}
+	msg := &messages.AddItem{
+		Sku:      input.Sku,
+		Quantity: qty,
+	}
+	if input.StoreId != nil {
+		msg.StoreId = input.StoreId
+	}
+	if input.Sku != "" {
+		// Pass along the item id so findParentLineId can match.
+		msg.ItemId = parentItemId
+	}
+	if len(input.Fields) > 0 {
+		msg.CustomFields = input.Fields
+	}
+	if parentItemId > 0 {
+		msg.ParentId = &parentItemId
+	}
+	return msg
+}
+
+func applyItemGroups(ctx context.Context, applier CartApplier, id uint64, groups []itemGroup) (*actor.MutationResult[cart.CartGrain], error) {
+	var last *actor.MutationResult[cart.CartGrain]
+	for _, g := range groups {
+		if g.parent == nil {
+			continue
+		}
+		res, err := applier.Apply(ctx, id, g.parent)
+		if err != nil {
+			return nil, err
+		}
+		last = res
+
+		if len(g.children) == 0 {
+			continue
+		}
+		parentLineId, ok := findParentLineId(&res.Result, g.parent)
+		if !ok {
+			continue
+		}
+		childMsgs := make([]proto.Message, len(g.children))
+		for i, c := range g.children {
+			c.ParentId = &parentLineId
+			childMsgs[i] = c
+		}
+		res, err = applier.Apply(ctx, id, childMsgs...)
+		if err != nil {
+			return nil, err
+		}
+		last = res
+	}
+	return last, nil
+}
+
+func findParentLineId(grain *cart.CartGrain, parent *messages.AddItem) (uint32, bool) {
+	for _, it := range grain.Items {
+		if it == nil || it.ParentId != nil {
+			continue
+		}
+		if it.ItemId != parent.ItemId {
+			continue
+		}
+		sameStore := (it.StoreId == nil && parent.StoreId == nil) ||
+			(it.StoreId != nil && parent.StoreId != nil && *it.StoreId == *parent.StoreId)
+		if sameStore {
+			return it.Id, true
+		}
+	}
+	return 0, false
+}

internal/ucp/cart_test.go

@@ -0,0 +1,236 @@
+package ucp
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	messages "git.k6n.net/mats/go-cart-actor/proto/cart"
+	"google.golang.org/protobuf/proto"
+)
+
+// testApplier implements CartApplier with an in-memory map of grains.
+type testApplier struct {
+	grains map[uint64]*cart.CartGrain
+}
+
+func newTestApplier() *testApplier {
+	return &testApplier{
+		grains: make(map[uint64]*cart.CartGrain),
+	}
+}
+
+func (a *testApplier) Get(_ context.Context, id uint64) (*cart.CartGrain, error) {
+	g, ok := a.grains[id]
+	if !ok {
+		g = cart.NewCartGrain(id, time.UnixMilli(1000000))
+		a.grains[id] = g
+	}
+	return g, nil
+}
+
+func (a *testApplier) Apply(_ context.Context, id uint64, msgs ...proto.Message) (*actor.MutationResult[cart.CartGrain], error) {
+	g, err := a.Get(nil, id)
+	if err != nil {
+		return nil, err
+	}
+	results := make([]actor.ApplyResult, len(msgs))
+	for i, msg := range msgs {
+		results[i] = actor.ApplyResult{Type: string(msg.ProtoReflect().Descriptor().FullName())}
+		switch m := msg.(type) {
+		case *messages.ClearCartRequest:
+			g.Items = nil
+			g.Vouchers = nil
+			g.TotalDiscount = cart.NewPrice()
+			g.TotalPrice = cart.NewPrice()
+		case *messages.SetUserId:
+			// userId is unexported; rely on serialization to verify.
+			_ = m
+		}
+	}
+	return &actor.MutationResult[cart.CartGrain]{
+		Result:    *g,
+		Mutations: results,
+	}, nil
+}
+
+// mustParseID returns the uint64 representation of a base62 cart id string.
+func mustParseID(s string) uint64 {
+	id, _ := cart.ParseCartId(s)
+	return uint64(id)
+}
+
+func TestCartHandler_CreateCart(t *testing.T) {
+	applier := newTestApplier()
+	handler := CartHandler(applier)
+
+	req := httptest.NewRequest("POST", "/", nil)
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusCreated {
+		t.Fatalf("expected 201 Created, got %d", rec.Code)
+	}
+
+	var resp CartResponse
+	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
+		t.Fatalf("failed to decode response: %v", err)
+	}
+	if resp.Id == "" {
+		t.Fatal("expected non-empty cart id")
+	}
+	if resp.Status != "active" {
+		t.Fatalf("expected status 'active', got %q", resp.Status)
+	}
+}
+
+func TestCartHandler_GetCartNotFound(t *testing.T) {
+	applier := newTestApplier()
+	handler := CartHandler(applier)
+
+	req := httptest.NewRequest("GET", "/nonexistent", nil)
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	// /nonexistent is a valid base62 string, so it parses, but the cart
+	// auto-creates on first Get, so we get a 200 with an empty cart.
+	// This is expected behavior (UCP auto-creates carts on read).
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200 (auto-create), got %d", rec.Code)
+	}
+}
+
+func TestCartHandler_CreateAndGet(t *testing.T) {
+	applier := newTestApplier()
+	handler := CartHandler(applier)
+
+	// Create a cart.
+	req := httptest.NewRequest("POST", "/", nil)
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+	if rec.Code != http.StatusCreated {
+		t.Fatalf("create failed: %d", rec.Code)
+	}
+
+	var created CartResponse
+	json.NewDecoder(rec.Body).Decode(&created)
+
+	// GET it back.
+	req = httptest.NewRequest("GET", "/"+created.Id, nil)
+	rec = httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d", rec.Code)
+	}
+
+	var got CartResponse
+	json.NewDecoder(rec.Body).Decode(&got)
+	if got.Id != created.Id {
+		t.Fatalf("expected id %q, got %q", created.Id, got.Id)
+	}
+}
+
+func TestCartHandler_CancelCart(t *testing.T) {
+	applier := newTestApplier()
+	handler := CartHandler(applier)
+
+	// Create a cart.
+	req := httptest.NewRequest("POST", "/", nil)
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	var created CartResponse
+	json.NewDecoder(rec.Body).Decode(&created)
+
+	// Cancel it.
+	req = httptest.NewRequest("POST", "/"+created.Id+"/cancel", nil)
+	rec = httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d", rec.Code)
+	}
+
+	var cancelled CartResponse
+	json.NewDecoder(rec.Body).Decode(&cancelled)
+	if cancelled.Id != created.Id {
+		t.Fatalf("expected same id %q, got %q", created.Id, cancelled.Id)
+	}
+}
+
+func TestCartHandler_UpdateCart(t *testing.T) {
+	applier := newTestApplier()
+	handler := CartHandler(applier)
+
+	// Create a cart.
+	req := httptest.NewRequest("POST", "/", nil)
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	var created CartResponse
+	json.NewDecoder(rec.Body).Decode(&created)
+
+	// Update with items (test applier doesn't process AddItem, but the
+	// handler still returns 200 — items are populated by the real grain pool).
+	updateBody := `{"items": [{"sku": "test-sku", "quantity": 2, "name": "Test Item"}]}`
+	req = httptest.NewRequest("PUT", "/"+created.Id, strings.NewReader(updateBody))
+	req.Header.Set("Content-Type", "application/json")
+	rec = httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", rec.Code, rec.Body.String())
+	}
+
+	var updated CartResponse
+	json.NewDecoder(rec.Body).Decode(&updated)
+	if updated.Id != created.Id {
+		t.Fatalf("expected same id %q, got %q", created.Id, updated.Id)
+	}
+}
+
+func TestCartResponse_Conversion(t *testing.T) {
+	id := mustParseID("ABCD")
+	g := cart.NewCartGrain(id, time.UnixMilli(1000000))
+	g.Currency = "SEK"
+	g.Items = append(g.Items, &cart.CartItem{
+		Sku:         "test-1",
+		Quantity:    2,
+		Price:       *mustPrice(10000, 2500),
+		TotalPrice:  *mustPrice(20000, 5000),
+		Tax:         2500,
+		Meta:        &cart.ItemMeta{Name: "Test Item"},
+	})
+	g.TotalPrice = mustPrice(20000, 5000)
+
+	resp := cartGrainToResponse(g.Id.String(), g)
+	if len(resp.Items) != 1 {
+		t.Fatalf("expected 1 item, got %d", len(resp.Items))
+	}
+	if resp.Items[0].Sku != "test-1" {
+		t.Fatalf("expected sku 'test-1', got %q", resp.Items[0].Sku)
+	}
+	if resp.Items[0].Name != "Test Item" {
+		t.Fatalf("expected name 'Test Item', got %q", resp.Items[0].Name)
+	}
+	if resp.Totals.TotalIncVat != 20000 {
+		t.Fatalf("expected total 20000, got %d", resp.Totals.TotalIncVat)
+	}
+	if resp.Totals.Currency != "SEK" {
+		t.Fatalf("expected currency SEK, got %q", resp.Totals.Currency)
+	}
+}
+
+func mustPrice(incVat int64, totalVat int64) *cart.Price {
+	return &cart.Price{
+		IncVat: incVat,
+		VatRates: map[float32]int64{25: totalVat},
+	}
+}

internal/ucp/checkout.go

@@ -0,0 +1,681 @@
+package ucp
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/checkout"
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	profilePkg "git.k6n.net/mats/go-cart-actor/pkg/profile"
+	checkoutMessages "git.k6n.net/mats/go-cart-actor/proto/checkout"
+	"google.golang.org/protobuf/types/known/anypb"
+	"google.golang.org/protobuf/types/known/timestamppb"
+)
+
+// CheckoutServer is the UCP REST adapter over the checkout grain pool.
+type CheckoutServer struct {
+	applier        CheckoutApplier
+	profileApplier ProfileApplier // optional; when set links checkouts/orders to profiles
+	orderSvc       OrderApplier   // optional; when set creates real orders on complete
+}
+
+// NewCheckoutServer builds a UCP REST adapter over a checkout grain pool.
+func NewCheckoutServer(applier CheckoutApplier, orderSvc ...OrderApplier) *CheckoutServer {
+	s := &CheckoutServer{applier: applier}
+	if len(orderSvc) > 0 {
+		s.orderSvc = orderSvc[0]
+	}
+	return s
+}
+
+// SetProfileApplier enables identity linking on this server.
+func (s *CheckoutServer) SetProfileApplier(pa ProfileApplier) {
+	s.profileApplier = pa
+}
+
+// ---------------------------------------------------------------------------
+// UCP Checkout endpoints
+// ---------------------------------------------------------------------------
+
+// handleCreateCheckout handles POST /checkout-sessions.
+//
+// Initiates a checkout session from a cart. The cart id is required.
+func (s *CheckoutServer) handleCreateCheckout(w http.ResponseWriter, r *http.Request) {
+	var req CreateCheckoutRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body: "+err.Error())
+		return
+	}
+
+	items := req.Items
+	if len(items) == 0 && len(req.LineItems) > 0 {
+		items = req.LineItems
+	}
+
+	var cartIdStr string
+	if req.CartId != "" {
+		cartIdStr = req.CartId
+	} else if len(items) > 0 {
+		// Fetch cart base URL
+		cartBaseURL := os.Getenv("CART_INTERNAL_URL")
+		if cartBaseURL == "" {
+			cartBaseURL = "http://cart:8080"
+		}
+
+		// Prepare POST request to /ucp/v1/carts/ to create and seed the cart
+		createReqBody := CreateCartRequest{
+			Items: items,
+		}
+		bodyBytes, err := json.Marshal(createReqBody)
+		if err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to marshal create cart request: "+err.Error())
+			return
+		}
+
+		client := &http.Client{Timeout: 10 * time.Second}
+		cartReq, err := http.NewRequestWithContext(r.Context(), "POST", fmt.Sprintf("%s/ucp/v1/carts/", cartBaseURL), bytes.NewReader(bodyBytes))
+		if err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to create post cart request: "+err.Error())
+			return
+		}
+		cartReq.Header.Set("Content-Type", "application/json")
+
+		profile := os.Getenv("UCP_AGENT_PROFILE")
+		if profile == "" {
+			profile = DefaultUCPAgentProfile
+		}
+		cartReq.Header.Set("UCP-Agent", `profile="`+profile+`"`)
+
+		cartResp, err := client.Do(cartReq)
+		if err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to create implicit cart: "+err.Error())
+			return
+		}
+		defer cartResp.Body.Close()
+
+		if cartResp.StatusCode != http.StatusCreated && cartResp.StatusCode != http.StatusOK {
+			writeError(w, http.StatusBadRequest, fmt.Sprintf("cart service returned status: %d when creating implicit cart", cartResp.StatusCode))
+			return
+		}
+
+		var cartRespBody CartResponse
+		if err := json.NewDecoder(cartResp.Body).Decode(&cartRespBody); err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to decode implicit cart response: "+err.Error())
+			return
+		}
+		cartIdStr = cartRespBody.Id
+	} else {
+		writeError(w, http.StatusBadRequest, "cartId or items/line_items is required")
+		return
+	}
+
+	cartId, ok := cart.ParseCartId(cartIdStr)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid cartId")
+		return
+	}
+
+	// Create a new checkout session id.
+	checkoutId, err := cart.NewCartId()
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to generate checkout id")
+		return
+	}
+
+	// Fetch cart state from cart service
+	cartBaseURL := os.Getenv("CART_INTERNAL_URL")
+	if cartBaseURL == "" {
+		cartBaseURL = "http://cart:8080"
+	}
+	url := fmt.Sprintf("%s/cart/byid/%s", cartBaseURL, cartId.String())
+
+	client := &http.Client{Timeout: 10 * time.Second}
+	cartReq, err := http.NewRequestWithContext(r.Context(), "GET", url, nil)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to create cart request: "+err.Error())
+		return
+	}
+
+	profile := os.Getenv("UCP_AGENT_PROFILE")
+	if profile == "" {
+		profile = DefaultUCPAgentProfile
+	}
+	cartReq.Header.Set("UCP-Agent", `profile="`+profile+`"`)
+
+	cartResp, err := client.Do(cartReq)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to fetch cart: "+err.Error())
+		return
+	}
+	defer cartResp.Body.Close()
+
+	if cartResp.StatusCode != http.StatusOK {
+		writeError(w, http.StatusBadRequest, fmt.Sprintf("cart service returned status: %d", cartResp.StatusCode))
+		return
+	}
+
+	cartStateBytes, err := io.ReadAll(cartResp.Body)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read cart state: "+err.Error())
+		return
+	}
+
+	// Initialize checkout with cart reference and state.
+	initMsg := &checkoutMessages.InitializeCheckout{
+		OrderId: "",
+		CartId:  uint64(cartId),
+		CartState: &anypb.Any{
+			TypeUrl: "type.googleapis.com/cart.CartGrain",
+			Value:   cartStateBytes,
+		},
+	}
+
+	if _, err := s.applier.Apply(r.Context(), uint64(checkoutId), initMsg); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to initialize checkout: "+err.Error())
+		return
+	}
+
+	g, err := s.applier.Get(r.Context(), uint64(checkoutId))
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read checkout: "+err.Error())
+		return
+	}
+
+	// Link checkout to customer profile if identity linking is enabled.
+	if s.profileApplier != nil && req.CustomerId != "" {
+		if pid, ok := profilePkg.ParseProfileId(req.CustomerId); ok {
+			if err := linkCheckoutToProfile(s.profileApplier, r.Context(), uint64(pid), uint64(checkoutId), uint64(cartId)); err != nil {
+				log.Printf("identity: failed to link checkout %d to profile %s: %v", uint64(checkoutId), req.CustomerId, err)
+			}
+		}
+	}
+
+	writeJSON(w, http.StatusCreated, checkoutGrainToResponse(checkoutId.String(), g))
+}
+
+// handleGetCheckout handles GET /checkout-sessions/{id}.
+func (s *CheckoutServer) handleGetCheckout(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseSessionID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid checkout session id")
+		return
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusNotFound, "checkout session not found")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, checkoutGrainToResponse(r.PathValue("id"), g))
+}
+
+// handleUpdateCheckout handles PUT /checkout-sessions/{id}.
+//
+// Updates checkout with delivery, contact, or pickup point info.
+func (s *CheckoutServer) handleUpdateCheckout(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseSessionID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid checkout session id")
+		return
+	}
+
+	var req UpdateCheckoutRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body: "+err.Error())
+		return
+	}
+
+	// Apply delivery.
+	if req.Delivery != nil {
+		msg := &checkoutMessages.SetDelivery{
+			Provider: req.Delivery.Provider,
+		}
+		for _, itemId := range req.Delivery.ItemIds {
+			msg.Items = append(msg.Items, itemId)
+		}
+		if _, err := s.applier.Apply(r.Context(), id, msg); err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to set delivery: "+err.Error())
+			return
+		}
+	}
+
+	// Apply pickup point.
+	if req.PickupPoint != nil {
+		pp := &checkoutMessages.SetPickupPoint{
+			DeliveryId: req.PickupPoint.DeliveryId,
+			PickupPoint: &checkoutMessages.PickupPoint{
+				Id:   req.PickupPoint.Id,
+				Name: req.PickupPoint.Name,
+			},
+		}
+		if _, err := s.applier.Apply(r.Context(), id, pp); err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to set pickup point: "+err.Error())
+			return
+		}
+	}
+
+	// Apply contact details.
+	if req.Contact != nil {
+		msg := &checkoutMessages.ContactDetailsUpdated{
+			Email:      req.Contact.Email,
+			Phone:      req.Contact.Phone,
+			Name:       req.Contact.Name,
+			PostalCode: req.Contact.PostalCode,
+		}
+		if _, err := s.applier.Apply(r.Context(), id, msg); err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to update contact details: "+err.Error())
+			return
+		}
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read checkout: "+err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusOK, checkoutGrainToResponse(r.PathValue("id"), g))
+}
+
+// handleCompleteCheckout handles POST /checkout-sessions/{id}/complete.
+//
+// Completes the checkout session and creates an order. When an OrderApplier
+// is configured on the server, a real order is created by calling the order
+// service. Otherwise, a simplified order reference is generated locally.
+func (s *CheckoutServer) handleCompleteCheckout(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseSessionID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid checkout session id")
+		return
+	}
+
+	var req CompleteCheckoutRequest
+	json.NewDecoder(r.Body).Decode(&req) // best-effort
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusNotFound, "checkout session not found")
+		return
+	}
+
+	// Default currency/country from the request or fall back to cart/cart state.
+	currency := req.Currency
+	country := req.Country
+	if currency == "" && g.CartState != nil {
+		currency = g.CartState.Currency
+	}
+	if currency == "" {
+		currency = "SEK"
+	}
+
+	var orderID string
+
+	if s.orderSvc != nil {
+		// Real order creation via the configured OrderApplier.
+		orderID, err = s.orderSvc.CreateOrder(r.Context(), id, g, req.Provider, req.PaymentToken, currency, country)
+		if err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to create order: "+err.Error())
+			return
+		}
+	} else {
+		// Fallback: generate a local order reference (simplified).
+		var ref cart.CartId
+		ref, err = cart.NewCartId()
+		if err != nil {
+			writeError(w, http.StatusInternalServerError, "failed to generate order reference")
+			return
+		}
+		orderID = ref.String()
+	}
+
+	// Record the order on the checkout grain.
+	if _, err := s.applier.Apply(r.Context(), id,
+		&checkoutMessages.OrderCreated{
+			OrderId:   orderID,
+			CreatedAt: timestamppb.New(time.Now()),
+		},
+	); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to record order: "+err.Error())
+		return
+	}
+
+	g, err = s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read checkout: "+err.Error())
+		return
+	}
+
+	// Auto-link order to customer profile if identity linking is enabled.
+	if s.profileApplier != nil && orderID != "" && req.CustomerId != "" {
+		if pid, ok := profilePkg.ParseProfileId(req.CustomerId); ok {
+			if err := linkOrderToProfile(s.profileApplier, r.Context(), uint64(pid), orderID, uint64(g.CartId), "placed"); err != nil {
+				log.Printf("identity: failed to link order %s to profile %s: %v", orderID, req.CustomerId, err)
+			}
+		}
+	}
+
+	writeJSON(w, http.StatusOK, checkoutGrainToResponse(r.PathValue("id"), g))
+}
+
+// handleCancelCheckout handles POST /checkout-sessions/{id}/cancel.
+//
+// Cancels the checkout session.
+func (s *CheckoutServer) handleCancelCheckout(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseSessionID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid checkout session id")
+		return
+	}
+
+	// Cancel all active payments.
+	for {
+		g, err := s.applier.Get(r.Context(), id)
+		if err != nil {
+			break
+		}
+		openPayments := g.OpenPayments()
+		if len(openPayments) == 0 {
+			break
+		}
+		for _, p := range openPayments {
+			s.applier.Apply(r.Context(), id, &checkoutMessages.CancelPayment{
+				PaymentId:   p.PaymentId,
+				CancelledAt: timestamppb.New(time.Now()),
+			})
+		}
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusNotFound, "checkout session not found")
+		return
+	}
+	writeJSON(w, http.StatusOK, checkoutGrainToResponse(r.PathValue("id"), g))
+}
+
+// ---------------------------------------------------------------------------
+// OrderHTTPClient — an OrderApplier backed by the order service HTTP API
+// ---------------------------------------------------------------------------
+
+// OrderHTTPClient implements OrderApplier by POSTing to an order service's
+// /api/orders/from-checkout endpoint. It mirrors the existing -> order handoff
+// used by the checkout service's own Klarna/Adyen callbacks.
+type OrderHTTPClient struct {
+	baseURL    string
+	httpClient *http.Client
+	agentProfile string // UCP-Agent profile URI
+}
+
+// NewOrderHTTPClient returns an order applier that creates orders by calling
+// the order service at baseURL (e.g. "http://order-service:8092"). It reads
+// the UCP_AGENT_PROFILE env var for the profile URI, falling back to
+// DefaultUCPAgentProfile from the ucp package.
+func NewOrderHTTPClient(baseURL string) *OrderHTTPClient {
+	profile := os.Getenv("UCP_AGENT_PROFILE")
+	if profile == "" {
+		profile = DefaultUCPAgentProfile
+	}
+	return &OrderHTTPClient{
+		baseURL:    baseURL,
+		httpClient: &http.Client{Timeout: 30 * time.Second},
+		agentProfile: profile,
+	}
+}
+
+// fromCheckoutReq mirrors cmd/order/handlers_checkout.go's internal type.
+type fromCheckoutReq struct {
+	CheckoutId     string       `json:"checkoutId"`
+	IdempotencyKey string       `json:"idempotencyKey"`
+	CartId         string       `json:"cartId"`
+	Currency       string       `json:"currency"`
+	Country        string       `json:"country"`
+	CustomerEmail  string       `json:"customerEmail,omitempty"`
+	CustomerName   string       `json:"customerName,omitempty"`
+	Lines          []orderLine  `json:"lines"`
+	Payment        orderPayment `json:"payment"`
+}
+
+type orderLine struct {
+	Reference string `json:"reference"`
+	Sku       string `json:"sku"`
+	Name      string `json:"name"`
+	Quantity  int32  `json:"quantity"`
+	UnitPrice int64  `json:"unitPrice"`
+	TaxRate   int32  `json:"taxRate"`
+}
+
+type orderPayment struct {
+	Provider  string `json:"provider"`
+	Reference string `json:"reference"`
+	Amount    int64  `json:"amount"`
+}
+
+// CreateOrder implements OrderApplier. It builds a from-checkout request from
+// the checkout grain's state and POSTs it to the order service.
+func (c *OrderHTTPClient) CreateOrder(ctx context.Context, checkoutID uint64, g *checkout.CheckoutGrain, provider, reference, currency, country string) (string, error) {
+	if g.CartState == nil {
+		return "", fmt.Errorf("order: checkout %d has no cart state", checkoutID)
+	}
+
+	var customerEmail, customerName string
+	if g.ContactDetails != nil {
+		if g.ContactDetails.Email != nil {
+			customerEmail = *g.ContactDetails.Email
+		}
+		if g.ContactDetails.Name != nil {
+			customerName = *g.ContactDetails.Name
+		}
+	}
+
+	// Compute total from cart items + deliveries.
+	var totalAmount int64
+	lines := buildOrderLines(g)
+	for _, l := range lines {
+		totalAmount += l.UnitPrice * int64(l.Quantity)
+	}
+
+	req := fromCheckoutReq{
+		CheckoutId:     fmt.Sprintf("%d", checkoutID),
+		IdempotencyKey: fmt.Sprintf("ucp-checkout-%d", checkoutID),
+		CartId:         g.CartId.String(),
+		Currency:       currency,
+		Country:        country,
+		CustomerEmail:  customerEmail,
+		CustomerName:   customerName,
+		Lines:          lines,
+		Payment: orderPayment{
+			Provider:  provider,
+			Reference: reference,
+			Amount:    totalAmount,
+		},
+	}
+
+	body, err := json.Marshal(req)
+	if err != nil {
+		return "", fmt.Errorf("order: marshal: %w", err)
+	}
+
+	url := c.baseURL + "/api/orders/from-checkout"
+
+	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
+	if err != nil {
+		return "", fmt.Errorf("order: new request: %w", err)
+	}
+	httpReq.Header.Set("Content-Type", "application/json")
+	// Advertise this platform's UCP profile on all outgoing requests.
+	WithUCPAgentOnRequest(httpReq, c.agentProfile)
+
+	resp, err := c.httpClient.Do(httpReq)
+	if err != nil {
+		return "", fmt.Errorf("order: do: %w", err)
+	}
+	defer resp.Body.Close()
+
+	// Both 201 and 409 (idempotent hit) are valid.
+	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusConflict {
+		return "", fmt.Errorf("order: %s", resp.Status)
+	}
+
+	var result struct {
+		OrderId string `json:"orderId"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+		return "", fmt.Errorf("order: decode: %w", err)
+	}
+	if result.OrderId == "" {
+		return "", fmt.Errorf("order: empty orderId in response")
+	}
+	return result.OrderId, nil
+}
+
+// buildOrderLines converts a checkout grain's cart items and delivery selections
+// into order lines, matching the format expected by the order service.
+func buildOrderLines(g *checkout.CheckoutGrain) []orderLine {
+	lines := make([]orderLine, 0, len(g.CartState.Items)+len(g.Deliveries))
+	for _, it := range g.CartState.Items {
+		if it == nil {
+			continue
+		}
+		name := ""
+		if it.Meta != nil {
+			name = it.Meta.Name
+		}
+		lines = append(lines, orderLine{
+			Reference: it.Sku,
+			Sku:       it.Sku,
+			Name:      name,
+			Quantity:  int32(it.Quantity),
+			UnitPrice: it.Price.IncVat,
+			TaxRate:   int32(it.Tax),
+		})
+	}
+	for _, d := range g.Deliveries {
+		if d == nil || d.Price.IncVat <= 0 {
+			continue
+		}
+		lines = append(lines, orderLine{
+			Reference: d.Provider,
+			Sku:       d.Provider,
+			Name:      "Delivery",
+			Quantity:  1,
+			UnitPrice: d.Price.IncVat,
+			TaxRate:   2500,
+		})
+	}
+	return lines
+}
+
+// ---------------------------------------------------------------------------
+// Helper: parse session id from path
+// ---------------------------------------------------------------------------
+
+func parseSessionID(r *http.Request) (uint64, bool) {
+	raw := r.PathValue("id")
+	if raw == "" {
+		return 0, false
+	}
+	cid, ok := cart.ParseCartId(raw)
+	if !ok {
+		return 0, false
+	}
+	return uint64(cid), true
+}
+
+// ---------------------------------------------------------------------------
+// Helper: convert CheckoutGrain → UCP CheckoutResponse
+// ---------------------------------------------------------------------------
+
+func checkoutGrainToResponse(id string, g *checkout.CheckoutGrain) CheckoutResponse {
+	resp := CheckoutResponse{
+		Id:        id,
+		CartId:    g.CartId.String(),
+		Status:    "active",
+		Deliveries: make([]DeliveryResponse, 0, len(g.Deliveries)),
+		Payments:  make([]PaymentResponse, 0, len(g.Payments)),
+		Totals:    Totals{Currency: "SEK"},
+	}
+
+	if g.OrderId != nil && *g.OrderId != "" {
+		resp.OrderId = g.OrderId
+		resp.Status = "completed"
+	}
+
+	if g.CartState != nil {
+		for _, it := range g.CartState.Items {
+			if it == nil {
+				continue
+			}
+			item := CartItem{
+				Sku:        it.Sku,
+				Quantity:   int(it.Quantity),
+				UnitPrice:  it.Price.IncVat,
+				TotalPrice: it.TotalPrice.IncVat,
+				TaxRate:    it.Tax,
+			}
+			if it.Meta != nil {
+				item.Name = it.Meta.Name
+				item.Image = it.Meta.Image
+			}
+			resp.Items = append(resp.Items, item)
+		}
+		if g.CartState.TotalPrice != nil {
+			resp.Totals.TotalIncVat = g.CartState.TotalPrice.IncVat
+			resp.Totals.TotalExVat = g.CartState.TotalPrice.ValueExVat()
+			resp.Totals.TotalVat = g.CartState.TotalPrice.TotalVat()
+		}
+	}
+
+	for _, d := range g.Deliveries {
+		if d == nil {
+			continue
+		}
+		dr := DeliveryResponse{
+			Id:       d.Id,
+			Provider: d.Provider,
+			Price:    d.Price.IncVat,
+			Items:    d.Items,
+		}
+		if d.PickupPoint != nil {
+			dr.PickupPoint = &PickupPointResp{
+				Id:      d.PickupPoint.Id,
+				Name:    d.PickupPoint.Name,
+				Address: d.PickupPoint.Address,
+				City:    d.PickupPoint.City,
+				Zip:     d.PickupPoint.Zip,
+			}
+		}
+		resp.Deliveries = append(resp.Deliveries, dr)
+	}
+
+	if g.ContactDetails != nil {
+		resp.Contact = &ContactResponse{
+			Email:      g.ContactDetails.Email,
+			Phone:      g.ContactDetails.Phone,
+			Name:       g.ContactDetails.Name,
+			PostalCode: g.ContactDetails.PostalCode,
+		}
+	}
+
+	for _, p := range g.Payments {
+		if p == nil {
+			continue
+		}
+		resp.Payments = append(resp.Payments, PaymentResponse{
+			Id:       p.PaymentId,
+			Provider: p.Provider,
+			Amount:   p.Amount,
+			Currency: p.Currency,
+			Status:   string(p.Status),
+		})
+	}
+
+	return resp
+}

internal/ucp/checkout_test.go

@@ -0,0 +1,153 @@
+package ucp
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	"git.k6n.net/mats/go-cart-actor/pkg/checkout"
+	checkoutMessages "git.k6n.net/mats/go-cart-actor/proto/checkout"
+	"google.golang.org/protobuf/proto"
+)
+
+type testCheckoutApplier struct {
+	grains map[uint64]*checkout.CheckoutGrain
+}
+
+func newTestCheckoutApplier() *testCheckoutApplier {
+	return &testCheckoutApplier{
+		grains: make(map[uint64]*checkout.CheckoutGrain),
+	}
+}
+
+func (a *testCheckoutApplier) Get(_ context.Context, id uint64) (*checkout.CheckoutGrain, error) {
+	g, ok := a.grains[id]
+	if !ok {
+		g = checkout.NewCheckoutGrain(id, 0, 0, time.UnixMilli(1000000), nil)
+		a.grains[id] = g
+	}
+	return g, nil
+}
+
+func (a *testCheckoutApplier) Apply(ctx context.Context, id uint64, msgs ...proto.Message) (*actor.MutationResult[checkout.CheckoutGrain], error) {
+	g, err := a.Get(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	for _, msg := range msgs {
+		switch m := msg.(type) {
+		case *checkoutMessages.InitializeCheckout:
+			g.CartId = cart.CartId(m.CartId)
+		}
+	}
+	return &actor.MutationResult[checkout.CheckoutGrain]{
+		Result: *g,
+	}, nil
+}
+
+func TestCheckoutHandler_CreateWithCartId(t *testing.T) {
+	// Start a mock Cart server.
+	mockCartServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !strings.Contains(r.URL.Path, "/cart/byid/") {
+			t.Errorf("expected path to contain /cart/byid/, got %q", r.URL.Path)
+		}
+		// Return dummy cart state bytes.
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{}`))
+	}))
+	defer mockCartServer.Close()
+
+	os.Setenv("CART_INTERNAL_URL", mockCartServer.URL)
+	defer os.Unsetenv("CART_INTERNAL_URL")
+
+	applier := newTestCheckoutApplier()
+	handler := CheckoutHandler(applier)
+
+	// Create a dummy cart ID.
+	dummyCartId, _ := cart.NewCartId()
+
+	reqBody := fmt.Sprintf(`{"cartId": %q}`, dummyCartId.String())
+	req := httptest.NewRequest("POST", "/", strings.NewReader(reqBody))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusCreated {
+		t.Fatalf("expected 201 Created, got %d. Body: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp CheckoutResponse
+	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
+		t.Fatalf("failed to decode response: %v", err)
+	}
+	if resp.Id == "" {
+		t.Fatal("expected non-empty checkout session id")
+	}
+	if resp.CartId != dummyCartId.String() {
+		t.Fatalf("expected cartId %q, got %q", dummyCartId.String(), resp.CartId)
+	}
+}
+
+func TestCheckoutHandler_CreateWithLineItemsFallback(t *testing.T) {
+	// Start a mock Cart server that supports both creating a cart and getting it.
+	var createdCartId cart.CartId
+	mockCartServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method == "POST" && strings.Contains(r.URL.Path, "/ucp/v1/carts/") {
+			var err error
+			createdCartId, err = cart.NewCartId()
+			if err != nil {
+				w.WriteHeader(http.StatusInternalServerError)
+				return
+			}
+			w.Header().Set("Content-Type", "application/json")
+			w.WriteHeader(http.StatusCreated)
+			w.Write([]byte(fmt.Sprintf(`{"id": %q, "status": "active"}`, createdCartId.String())))
+			return
+		}
+
+		if r.Method == "GET" && strings.Contains(r.URL.Path, "/cart/byid/") {
+			w.WriteHeader(http.StatusOK)
+			w.Write([]byte(`{}`))
+			return
+		}
+
+		w.WriteHeader(http.StatusNotFound)
+	}))
+	defer mockCartServer.Close()
+
+	os.Setenv("CART_INTERNAL_URL", mockCartServer.URL)
+	defer os.Unsetenv("CART_INTERNAL_URL")
+
+	applier := newTestCheckoutApplier()
+	handler := CheckoutHandler(applier)
+
+	// POST with line_items and no cartId.
+	reqBody := `{"line_items": [{"sku": "SKU123", "quantity": 2}]}`
+	req := httptest.NewRequest("POST", "/", strings.NewReader(reqBody))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusCreated {
+		t.Fatalf("expected 201 Created, got %d. Body: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp CheckoutResponse
+	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
+		t.Fatalf("failed to decode response: %v", err)
+	}
+	if resp.Id == "" {
+		t.Fatal("expected non-empty checkout session id")
+	}
+	if resp.CartId != createdCartId.String() {
+		t.Fatalf("expected cartId %q to match created implicit cart %q", resp.CartId, createdCartId.String())
+	}
+}

internal/ucp/customer.go

@@ -0,0 +1,421 @@
+package ucp
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/profile"
+	messages "git.k6n.net/mats/go-cart-actor/proto/profile"
+)
+
+// CustomerServer is the UCP REST adapter over the profile grain pool.
+type CustomerServer struct {
+	applier ProfileApplier
+}
+
+// NewCustomerServer builds a UCP REST adapter over a profile grain pool.
+func NewCustomerServer(applier ProfileApplier) *CustomerServer {
+	return &CustomerServer{applier: applier}
+}
+
+// ---------------------------------------------------------------------------
+// UCP Customer endpoints
+// ---------------------------------------------------------------------------
+
+// handleCreateCustomer handles POST /customers — generates a new profile ID
+// server-side (base62-encoded random 64-bit), applies the profile mutation,
+// and returns 201 with the generated ID. Unlike PUT /customers/{id}, the
+// caller does not choose the identifier.
+func (s *CustomerServer) handleCreateCustomer(w http.ResponseWriter, r *http.Request) {
+	var req CustomerUpdateRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body: "+err.Error())
+		return
+	}
+
+	rawId, err := profile.NewProfileId()
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to generate id")
+		return
+	}
+	id := uint64(rawId)
+
+	msg := &messages.SetProfile{
+		Name:      req.Name,
+		Email:     req.Email,
+		Phone:     req.Phone,
+		Language:  req.Language,
+		Currency:  req.Currency,
+		AvatarUrl: req.AvatarUrl,
+	}
+
+	if _, err := s.applier.Apply(r.Context(), id, msg); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to create customer: "+err.Error())
+		return
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read customer: "+err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusCreated, customerGrainToResponse(rawId.String(), g))
+}
+
+// handleGetCustomer handles GET /customers/{id} with ETag-based conditional
+// GET support. When the client sends If-None-Match matching the current ETag,
+// a 304 Not Modified is returned with no body — the caller reuses their cached
+// response. The ETag is derived from the grain's lastChange timestamp and
+// customer data hash, so it changes on any mutation.
+func (s *CustomerServer) handleGetCustomer(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseCustomerID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid customer id")
+		return
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusNotFound, "customer not found")
+		return
+	}
+
+	etag := computeCustomerETag(r.PathValue("id"), g)
+
+	if match := r.Header.Get("If-None-Match"); match != "" {
+		if match == etag || match == "*" {
+			w.Header().Set("ETag", etag)
+			w.Header().Set("Vary", "Accept-Encoding")
+			w.WriteHeader(http.StatusNotModified)
+			return
+		}
+	}
+
+	w.Header().Set("ETag", etag)
+	w.Header().Set("Vary", "Accept-Encoding")
+	writeJSON(w, http.StatusOK, customerGrainToResponse(r.PathValue("id"), g))
+}
+
+// handleUpdateCustomer handles PUT /customers/{id}.
+func (s *CustomerServer) handleUpdateCustomer(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseCustomerID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid customer id")
+		return
+	}
+
+	var req CustomerUpdateRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body: "+err.Error())
+		return
+	}
+
+	msg := &messages.SetProfile{
+		Name:      req.Name,
+		Email:     req.Email,
+		Phone:     req.Phone,
+		Language:  req.Language,
+		Currency:  req.Currency,
+		AvatarUrl: req.AvatarUrl,
+	}
+
+	if _, err := s.applier.Apply(r.Context(), id, msg); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to update customer: "+err.Error())
+		return
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read customer: "+err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusOK, customerGrainToResponse(r.PathValue("id"), g))
+}
+
+// handleAddAddress handles POST /customers/{id}/addresses.
+func (s *CustomerServer) handleAddAddress(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseCustomerID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid customer id")
+		return
+	}
+
+	var req AddAddressRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body: "+err.Error())
+		return
+	}
+
+	if req.AddressLine1 == "" || req.City == "" || req.Zip == "" || req.Country == "" {
+		writeError(w, http.StatusBadRequest, "addressLine1, city, zip, and country are required")
+		return
+	}
+
+	addr := &messages.Address{
+		Label:             req.Label,
+		FullName:          req.FullName,
+		AddressLine1:      req.AddressLine1,
+		City:              req.City,
+		State:             req.State,
+		Zip:               req.Zip,
+		Country:           req.Country,
+		IsDefaultShipping: req.IsDefaultShipping,
+		IsDefaultBilling:  req.IsDefaultBilling,
+	}
+	if req.AddressLine2 != "" {
+		addr.AddressLine2 = &req.AddressLine2
+	}
+	if req.Phone != "" {
+		addr.Phone = &req.Phone
+	}
+	msg := &messages.AddAddress{Address: addr}
+
+	if _, err := s.applier.Apply(r.Context(), id, msg); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to add address: "+err.Error())
+		return
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read customer: "+err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusCreated, customerGrainToResponse(r.PathValue("id"), g))
+}
+
+// handleUpdateAddress handles PUT /customers/{id}/addresses/{addressId}.
+func (s *CustomerServer) handleUpdateAddress(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseCustomerID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid customer id")
+		return
+	}
+
+	addressID, ok := parseAddressID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid address id")
+		return
+	}
+
+	var req UpdateAddressRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body: "+err.Error())
+		return
+	}
+
+	msg := &messages.UpdateAddress{
+		Id:                addressID,
+		Label:             req.Label,
+		FullName:          req.FullName,
+		AddressLine1:      req.AddressLine1,
+		AddressLine2:      req.AddressLine2,
+		City:              req.City,
+		State:             req.State,
+		Zip:               req.Zip,
+		Country:           req.Country,
+		Phone:             req.Phone,
+		IsDefaultShipping: req.IsDefaultShipping,
+		IsDefaultBilling:  req.IsDefaultBilling,
+	}
+
+	if _, err := s.applier.Apply(r.Context(), id, msg); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to update address: "+err.Error())
+		return
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read customer: "+err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusOK, customerGrainToResponse(r.PathValue("id"), g))
+}
+
+// handleRemoveAddress handles DELETE /customers/{id}/addresses/{addressId}.
+func (s *CustomerServer) handleRemoveAddress(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseCustomerID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid customer id")
+		return
+	}
+
+	addressID, ok := parseAddressID(r)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid address id")
+		return
+	}
+
+	msg := &messages.RemoveAddress{Id: addressID}
+
+	if _, err := s.applier.Apply(r.Context(), id, msg); err != nil {
+		// Check if the error is a "not found" error.
+		errStr := err.Error()
+		if containsNotFound(errStr) {
+			writeError(w, http.StatusNotFound, fmt.Sprintf("address %d not found", addressID))
+			return
+		}
+		writeError(w, http.StatusInternalServerError, "failed to remove address: "+errStr)
+		return
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read customer: "+err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusOK, customerGrainToResponse(r.PathValue("id"), g))
+}
+
+// ---------------------------------------------------------------------------
+// Identity linking helpers
+// ---------------------------------------------------------------------------
+
+// linkCartToProfile links a cart to the given profile by applying a LinkCart mutation.
+func linkCartToProfile(applier ProfileApplier, ctx context.Context, profileID uint64, cartID uint64) error {
+	if applier == nil {
+		return nil
+	}
+	_, err := applier.Apply(ctx, profileID, &messages.LinkCart{
+		CartId: cartID,
+		Label:  "current cart",
+	})
+	return err
+}
+
+// linkCheckoutToProfile links a checkout to the given profile by applying a LinkCheckout mutation.
+func linkCheckoutToProfile(applier ProfileApplier, ctx context.Context, profileID uint64, checkoutID uint64, cartID uint64) error {
+	if applier == nil {
+		return nil
+	}
+	_, err := applier.Apply(ctx, profileID, &messages.LinkCheckout{
+		CheckoutId: checkoutID,
+		CartId:     cartID,
+	})
+	return err
+}
+
+// linkOrderToProfile links an order to the given profile by applying a LinkOrder mutation.
+func linkOrderToProfile(applier ProfileApplier, ctx context.Context, profileID uint64, orderReference string, cartID uint64, status string) error {
+	if applier == nil {
+		return nil
+	}
+	_, err := applier.Apply(ctx, profileID, &messages.LinkOrder{
+		OrderReference: orderReference,
+		CartId:         cartID,
+		Status:         status,
+	})
+	return err
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+// parseCustomerID parses the base62 customer id from the path.
+func parseCustomerID(r *http.Request) (uint64, bool) {
+	raw := r.PathValue("id")
+	if raw == "" {
+		return 0, false
+	}
+	cid, ok := profile.ParseProfileId(raw)
+	if !ok {
+		return 0, false
+	}
+	return uint64(cid), true
+}
+
+// parseAddressID parses the numeric address id from the path.
+func parseAddressID(r *http.Request) (uint32, bool) {
+	raw := r.PathValue("addressId")
+	if raw == "" {
+		return 0, false
+	}
+	// Address IDs are simple numeric strings.
+	var id uint32
+	for _, c := range raw {
+		if c < '0' || c > '9' {
+			return 0, false
+		}
+		id = id*10 + uint32(c-'0')
+	}
+	return id, true
+}
+
+// containsNotFound reports whether errStr indicates a "not found" condition.
+func containsNotFound(errStr string) bool {
+	// Check for common not-found patterns in the error message.
+	for _, pattern := range []string{"not found", "not_found", "notfound"} {
+		if len(errStr) >= len(pattern) {
+			for i := 0; i <= len(errStr)-len(pattern); i++ {
+				match := true
+				for j := 0; j < len(pattern); j++ {
+					c1 := errStr[i+j]
+					c2 := pattern[j]
+					if c1 >= 'A' && c1 <= 'Z' {
+						c1 += 32
+					}
+					if c1 != c2 {
+						match = false
+						break
+					}
+				}
+				if match {
+					return true
+				}
+			}
+		}
+	}
+	return false
+}
+
+// computeCustomerETag returns a strong ETag for the customer's current state,
+// derived from the grain's lastChange timestamp and a hash of the ID + change
+// time. Any mutation (profile update, address change, linking) advances
+// lastChange, so the ETag changes when data changes.
+func computeCustomerETag(id string, g *profile.ProfileGrain) string {
+	h := sha256.Sum256([]byte(id + "\x00" + g.GetLastChange().Format(time.RFC3339Nano)))
+	return `"` + hex.EncodeToString(h[:16]) + `"`
+}
+
+// customerGrainToResponse converts a ProfileGrain to a CustomerResponse.
+func customerGrainToResponse(id string, g *profile.ProfileGrain) CustomerResponse {
+	resp := CustomerResponse{
+		Id:        id,
+		Name:      g.Name,
+		Email:     g.Email,
+		Phone:     g.Phone,
+		Language:  g.Language,
+		Currency:  g.Currency,
+		AvatarUrl: g.AvatarUrl,
+		Addresses: make([]AddressResponse, 0, len(g.Addresses)),
+	}
+
+	for _, a := range g.Addresses {
+		resp.Addresses = append(resp.Addresses, AddressResponse{
+			Id:                a.Id,
+			Label:             a.Label,
+			FullName:          a.FullName,
+			AddressLine1:      a.AddressLine1,
+			AddressLine2:      a.AddressLine2,
+			City:              a.City,
+			State:             a.State,
+			Zip:               a.Zip,
+			Country:           a.Country,
+			Phone:             a.Phone,
+			IsDefaultShipping: a.IsDefaultShipping,
+			IsDefaultBilling:  a.IsDefaultBilling,
+		})
+	}
+
+	return resp
+}

internal/ucp/customer_test.go

@@ -0,0 +1,498 @@
+package ucp
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	"git.k6n.net/mats/go-cart-actor/pkg/profile"
+	messages "git.k6n.net/mats/go-cart-actor/proto/profile"
+	"google.golang.org/protobuf/proto"
+)
+
+// testProfileApplier implements ProfileApplier with in-memory grains.
+type testProfileApplier struct {
+	grains map[uint64]*profile.ProfileGrain
+}
+
+func newTestProfileApplier() *testProfileApplier {
+	return &testProfileApplier{
+		grains: make(map[uint64]*profile.ProfileGrain),
+	}
+}
+
+func (a *testProfileApplier) Get(_ context.Context, id uint64) (*profile.ProfileGrain, error) {
+	g, ok := a.grains[id]
+	if !ok {
+		g = profile.NewProfileGrain(id, time.UnixMilli(1000000))
+		a.grains[id] = g
+	}
+	return g, nil
+}
+
+func (a *testProfileApplier) Apply(ctx context.Context, id uint64, msgs ...proto.Message) (*actor.MutationResult[profile.ProfileGrain], error) {
+	g, err := a.Get(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	for _, msg := range msgs {
+		switch m := msg.(type) {
+		case *messages.SetProfile:
+			if m.Name != nil {
+				g.Name = *m.Name
+			}
+			if m.Email != nil {
+				g.Email = *m.Email
+			}
+			if m.Phone != nil {
+				g.Phone = *m.Phone
+			}
+			if m.Language != nil {
+				g.Language = *m.Language
+			}
+			if m.Currency != nil {
+				g.Currency = *m.Currency
+			}
+			if m.AvatarUrl != nil {
+				g.AvatarUrl = *m.AvatarUrl
+			}
+		case *messages.AddAddress:
+			if m.Address == nil {
+				continue
+			}
+			g.Addresses = append(g.Addresses, profile.StoredAddress{
+				Id:                g.NextAddrId(),
+				Label:             m.Address.Label,
+				FullName:          m.Address.FullName,
+				AddressLine1:      m.Address.AddressLine1,
+				AddressLine2:      m.Address.GetAddressLine2(),
+				City:              m.Address.City,
+				State:             m.Address.State,
+				Zip:               m.Address.Zip,
+				Country:           m.Address.Country,
+				Phone:             m.Address.GetPhone(),
+				IsDefaultShipping: m.Address.IsDefaultShipping,
+				IsDefaultBilling:  m.Address.IsDefaultBilling,
+			})
+		case *messages.UpdateAddress:
+			for i := range g.Addresses {
+				if g.Addresses[i].Id == m.Id {
+					if m.Label != nil {
+						g.Addresses[i].Label = *m.Label
+					}
+					if m.AddressLine1 != nil {
+						g.Addresses[i].AddressLine1 = *m.AddressLine1
+					}
+				}
+			}
+		case *messages.RemoveAddress:
+			for i := range g.Addresses {
+				if g.Addresses[i].Id == m.Id {
+					g.Addresses = append(g.Addresses[:i], g.Addresses[i+1:]...)
+					break
+				}
+			}
+		case *messages.LinkCart:
+			g.Carts = append(g.Carts, profile.LinkedCart{CartId: m.CartId, Label: m.Label})
+		case *messages.LinkCheckout:
+			g.Checkouts = append(g.Checkouts, profile.LinkedCheckout{CheckoutId: m.CheckoutId, CartId: m.CartId})
+		case *messages.LinkOrder:
+			g.Orders = append(g.Orders, profile.LinkedOrder{OrderReference: m.OrderReference, CartId: m.CartId, Status: m.Status})
+		}
+	}
+	return &actor.MutationResult[profile.ProfileGrain]{
+		Result: *g,
+	}, nil
+}
+
+// testCartApplier is a minimal CartApplier mock for combined handler tests.
+type testCartApplier struct{}
+
+func (a *testCartApplier) Get(ctx context.Context, id uint64) (*cart.CartGrain, error) {
+	return nil, fmt.Errorf("not implemented")
+}
+
+func (a *testCartApplier) Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*actor.MutationResult[cart.CartGrain], error) {
+	return nil, fmt.Errorf("not implemented")
+}
+
+// Helper to get a test profile ID as a base62 string.
+func testProfileID(t *testing.T, applier *testProfileApplier) string {
+	t.Helper()
+	pid, err := profile.NewProfileId()
+	if err != nil {
+		t.Fatalf("failed to generate profile id: %v", err)
+	}
+	// Seed the grain.
+	applier.Get(context.Background(), uint64(pid))
+	return pid.String()
+}
+
+func TestGetCustomer(t *testing.T) {
+	applier := newTestProfileApplier()
+	id := testProfileID(t, applier)
+	handler := CustomerHandler(applier)
+
+	// Set up some profile data
+	pid, _ := profile.ParseProfileId(id)
+	applier.Apply(context.Background(), uint64(pid), &messages.SetProfile{
+		Name:  proto.String("Alice"),
+		Email: proto.String("alice@example.com"),
+	})
+
+	// GET /customers/{id}
+	req := httptest.NewRequest("GET", fmt.Sprintf("/%s", id), nil)
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200 OK, got %d. Body: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp CustomerResponse
+	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
+		t.Fatalf("failed to decode response: %v", err)
+	}
+	if resp.Id != id {
+		t.Fatalf("expected id %q, got %q", id, resp.Id)
+	}
+	if resp.Name != "Alice" {
+		t.Fatalf("expected Name 'Alice', got %q", resp.Name)
+	}
+	if resp.Email != "alice@example.com" {
+		t.Fatalf("expected Email 'alice@example.com', got %q", resp.Email)
+	}
+}
+
+func TestGetCustomerNotFound(t *testing.T) {
+	applier := newTestProfileApplier()
+	handler := CustomerHandler(applier)
+
+	// "nonexistent" is actually valid base62, so use an ID with characters outside the alphabet.
+	req := httptest.NewRequest("GET", "/!invalid!", nil)
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400 Bad Request for invalid id, got %d. Body: %s", rec.Code, rec.Body.String())
+	}
+}
+
+func TestUpdateCustomer(t *testing.T) {
+	applier := newTestProfileApplier()
+	id := testProfileID(t, applier)
+	handler := CustomerHandler(applier)
+
+	body := `{"name": "Bob", "email": "bob@example.com", "phone": "+46701234567", "language": "sv", "currency": "SEK"}`
+	req := httptest.NewRequest("PUT", fmt.Sprintf("/%s", id), strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200 OK, got %d. Body: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp CustomerResponse
+	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
+		t.Fatalf("failed to decode response: %v", err)
+	}
+	if resp.Name != "Bob" {
+		t.Fatalf("expected Name 'Bob', got %q", resp.Name)
+	}
+	if resp.Email != "bob@example.com" {
+		t.Fatalf("expected Email 'bob@example.com', got %q", resp.Email)
+	}
+	if resp.Phone != "+46701234567" {
+		t.Fatalf("expected Phone '+46701234567', got %q", resp.Phone)
+	}
+	if resp.Language != "sv" {
+		t.Fatalf("expected Language 'sv', got %q", resp.Language)
+	}
+	if resp.Currency != "SEK" {
+		t.Fatalf("expected Currency 'SEK', got %q", resp.Currency)
+	}
+}
+
+func TestAddAddress(t *testing.T) {
+	applier := newTestProfileApplier()
+	id := testProfileID(t, applier)
+	handler := CustomerHandler(applier)
+
+	body := `{
+		"label": "Home",
+		"fullName": "Alice",
+		"addressLine1": "Storgatan 1",
+		"addressLine2": "Lgh 101",
+		"city": "Stockholm",
+		"zip": "111 22",
+		"country": "SE",
+		"phone": "+46701234567"
+	}`
+	req := httptest.NewRequest("POST", fmt.Sprintf("/%s/addresses", id), strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusCreated {
+		t.Fatalf("expected 201 Created, got %d. Body: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp CustomerResponse
+	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
+		t.Fatalf("failed to decode response: %v", err)
+	}
+	if len(resp.Addresses) != 1 {
+		t.Fatalf("expected 1 address, got %d", len(resp.Addresses))
+	}
+	if resp.Addresses[0].Label != "Home" {
+		t.Fatalf("expected address label 'Home', got %q", resp.Addresses[0].Label)
+	}
+	if resp.Addresses[0].AddressLine1 != "Storgatan 1" {
+		t.Fatalf("expected addressLine1 'Storgatan 1', got %q", resp.Addresses[0].AddressLine1)
+	}
+	if resp.Addresses[0].AddressLine2 != "Lgh 101" {
+		t.Fatalf("expected addressLine2 'Lgh 101', got %q", resp.Addresses[0].AddressLine2)
+	}
+}
+
+func TestAddAddressMissingRequired(t *testing.T) {
+	applier := newTestProfileApplier()
+	id := testProfileID(t, applier)
+	handler := CustomerHandler(applier)
+
+	// Missing addressLine1
+	body := `{"city": "Stockholm", "zip": "111 22", "country": "SE"}`
+	req := httptest.NewRequest("POST", fmt.Sprintf("/%s/addresses", id), strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400 Bad Request for missing required fields, got %d. Body: %s", rec.Code, rec.Body.String())
+	}
+}
+
+func TestUpdateAddress(t *testing.T) {
+	applier := newTestProfileApplier()
+	id := testProfileID(t, applier)
+	handler := CustomerHandler(applier)
+
+	// First add an address
+	pid, _ := profile.ParseProfileId(id)
+	applier.Apply(context.Background(), uint64(pid), &messages.AddAddress{
+		Address: &messages.Address{
+			Label:        "Old Home",
+			FullName:     "Alice",
+			AddressLine1: "Old Street 1",
+			City:         "Old City",
+			Zip:          "000 00",
+			Country:      "SE",
+		},
+	})
+
+	// Get the address id from the grain
+	grain, _ := applier.Get(context.Background(), uint64(pid))
+	if len(grain.Addresses) == 0 {
+		t.Fatal("expected at least one address")
+	}
+	addrID := grain.Addresses[0].Id
+
+	body := fmt.Sprintf(`{"label": "New Home", "addressLine1": "New Street 2"}`)
+	req := httptest.NewRequest("PUT", fmt.Sprintf("/%s/addresses/%d", id, addrID), strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200 OK, got %d. Body: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp CustomerResponse
+	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
+		t.Fatalf("failed to decode response: %v", err)
+	}
+	if len(resp.Addresses) != 1 {
+		t.Fatalf("expected 1 address, got %d", len(resp.Addresses))
+	}
+	if resp.Addresses[0].Label != "New Home" {
+		t.Fatalf("expected label 'New Home', got %q", resp.Addresses[0].Label)
+	}
+	if resp.Addresses[0].AddressLine1 != "New Street 2" {
+		t.Fatalf("expected addressLine1 'New Street 2', got %q", resp.Addresses[0].AddressLine1)
+	}
+	// Unchanged fields should still be there
+	if resp.Addresses[0].City != "Old City" {
+		t.Fatalf("expected City 'Old City', got %q", resp.Addresses[0].City)
+	}
+}
+
+func TestUpdateAddressInvalidID(t *testing.T) {
+	applier := newTestProfileApplier()
+	id := testProfileID(t, applier)
+	handler := CustomerHandler(applier)
+
+	body := `{"label": "New Home"}`
+	req := httptest.NewRequest("PUT", fmt.Sprintf("/%s/addresses/abc", id), strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400 Bad Request for invalid address id, got %d", rec.Code)
+	}
+}
+
+func TestRemoveAddress(t *testing.T) {
+	applier := newTestProfileApplier()
+	id := testProfileID(t, applier)
+	handler := CustomerHandler(applier)
+
+	// First add an address
+	pid, _ := profile.ParseProfileId(id)
+	applier.Apply(context.Background(), uint64(pid), &messages.AddAddress{
+		Address: &messages.Address{
+			Label:        "Remove Me",
+			FullName:     "Alice",
+			AddressLine1: "Storgatan 1",
+			City:         "Stockholm",
+			Zip:          "111 22",
+			Country:      "SE",
+		},
+	})
+
+	grain, _ := applier.Get(context.Background(), uint64(pid))
+	if len(grain.Addresses) == 0 {
+		t.Fatal("expected at least one address")
+	}
+	addrID := grain.Addresses[0].Id
+
+	// DELETE /customers/{id}/addresses/{addressId}
+	req := httptest.NewRequest("DELETE", fmt.Sprintf("/%s/addresses/%d", id, addrID), nil)
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200 OK, got %d. Body: %s", rec.Code, rec.Body.String())
+	}
+
+	grain, _ = applier.Get(context.Background(), uint64(pid))
+	if len(grain.Addresses) != 0 {
+		t.Fatalf("expected 0 addresses after removal, got %d", len(grain.Addresses))
+	}
+}
+
+func TestRemoveAddressNotFound(t *testing.T) {
+	applier := newTestProfileApplier()
+	pid, err := profile.NewProfileId()
+	if err != nil {
+		t.Fatalf("failed to generate profile id: %v", err)
+	}
+	applier.Get(context.Background(), uint64(pid))
+
+	id := pid.String()
+	handler := CustomerHandler(applier)
+	req := httptest.NewRequest("DELETE", fmt.Sprintf("/%s/addresses/999", id), nil)
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	// Test applier silently ignores not-found removals (returns no error).
+	// In production, HandleRemoveAddress returns an error which maps to 404.
+	// Accept 200 here since the test applier is a simplified mock.
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200 (test applier limitation), got %d. Body: %s", rec.Code, rec.Body.String())
+	}
+}
+
+// TestRemoveAddressNotFoundRealistic tests the real mutation handler path via the registry.
+// It uses the real HandleRemoveAddress mutation to verify 404 behavior.
+func TestRemoveAddressNotFoundMutation(t *testing.T) {
+	// Test the real HandleRemoveAddress mutation directly.
+	g := profile.NewProfileGrain(1, time.Now())
+
+	// Add an address via the real handler
+	if err := profile.HandleAddAddress(g, &messages.AddAddress{
+		Address: &messages.Address{
+			Label:        "Test",
+			FullName:     "Alice",
+			AddressLine1: "Storgatan 1",
+			City:         "Stockholm",
+			Zip:          "111 22",
+			Country:      "SE",
+		},
+	}); err != nil {
+		t.Fatalf("HandleAddAddress failed: %v", err)
+	}
+
+	// Try to remove address 999 (doesn't exist)
+	err := profile.HandleRemoveAddress(g, &messages.RemoveAddress{Id: 999})
+	if err == nil {
+		t.Fatal("expected error for non-existent address, got nil")
+	}
+	expected := "RemoveAddress: address 999 not found"
+	if err.Error() != expected {
+		t.Fatalf("expected error %q, got %q", expected, err.Error())
+	}
+}
+
+func TestCustomerHandlerInvalidID(t *testing.T) {
+	applier := newTestProfileApplier()
+	handler := CustomerHandler(applier)
+
+	// Path "/" now has POST / registered (create customer), so GET / is 405.
+	// Paths with invalid base62 characters should get 400.
+	tests := []struct {
+		path           string
+		expectedStatus int
+	}{
+		{"/", http.StatusMethodNotAllowed},   // POST / exists, GET doesn't
+		{"/!invalid!", http.StatusBadRequest}, // has non-base62 chars
+	}
+	for _, tt := range tests {
+		req := httptest.NewRequest("GET", tt.path, nil)
+		rec := httptest.NewRecorder()
+		handler.ServeHTTP(rec, req)
+		if rec.Code != tt.expectedStatus {
+			t.Fatalf("for path %q: expected %d, got %d. Body: %s", tt.path, tt.expectedStatus, rec.Code, rec.Body.String())
+		}
+	}
+}
+
+func TestCustomerHandlerThroughCombinedMount(t *testing.T) {
+	// Test that the combined Handler correctly mounts customer endpoints.
+	// Use a mock CartApplier (bare minimum — never called in this test).
+	mockCart := &testCartApplier{}
+	profileApplier := newTestProfileApplier()
+
+	pid, _ := profile.NewProfileId()
+	profileApplier.Get(context.Background(), uint64(pid))
+
+	handler := Handler(mockCart, Options{
+		ProfileApplier: profileApplier,
+	})
+
+	// GET /customers/{id} should work
+	id := pid.String()
+	req := httptest.NewRequest("GET", fmt.Sprintf("/customers/%s", id), nil)
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200 OK, got %d. Body: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp CustomerResponse
+	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
+		t.Fatalf("failed to decode response: %v", err)
+	}
+	if resp.Id != id {
+		t.Fatalf("expected id %q, got %q", id, resp.Id)
+	}
+}

internal/ucp/handler.go

@@ -0,0 +1,174 @@
+package ucp
+
+import "net/http"
+
+// ---------------------------------------------------------------------------
+// Order HTTP handler mounting
+// ---------------------------------------------------------------------------
+
+// OrderHandler returns an http.Handler that routes UCP order REST endpoints.
+// Mount it under any prefix (e.g. /ucp/v1) in a ServeMux:
+//
+//	mux.Handle("/ucp/v1/orders", ucp.OrderHandler(pool))
+//	mux.Handle("/ucp/v1/orders/", ucp.OrderHandler(pool))
+//
+// To sign responses with RFC 9421 HTTP Message Signatures, wrap with WithSigning:
+//
+//	mux.Handle("/ucp/v1/orders", ucp.WithSigning(ucp.OrderHandler(pool), signer))
+func OrderHandler(applier OrderReadApplier) http.Handler {
+	s := NewOrderServer(applier)
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /{id}", s.handleGetOrder)
+	mux.HandleFunc("POST /{id}/cancel", s.handleCancelOrder)
+	mux.HandleFunc("POST /{id}/fulfillments", s.handleCreateFulfillment)
+	mux.HandleFunc("POST /{id}/returns", s.handleRequestReturn)
+	mux.HandleFunc("POST /{id}/refunds", s.handleIssueRefund)
+	return withUCPAgent(withJSONContentType(mux))
+}
+
+// ---------------------------------------------------------------------------
+// Cart HTTP handler mounting
+// ---------------------------------------------------------------------------
+
+// CartHandler returns an http.Handler that routes UCP cart REST endpoints.
+// Mount it under any prefix (e.g. /ucp/v1) in a ServeMux:
+//
+//	mux.Handle("/ucp/v1/carts", ucp.CartHandler(pool))
+//	mux.Handle("/ucp/v1/carts/", ucp.CartHandler(pool))
+//
+// To sign responses with RFC 9421 HTTP Message Signatures, wrap with WithSigning:
+//
+//	mux.Handle("/ucp/v1/carts", ucp.WithSigning(ucp.CartHandler(pool), signer))
+func CartHandler(applier CartApplier) http.Handler {
+	s := NewCartServer(applier)
+	mux := http.NewServeMux()
+	mux.HandleFunc("POST /", s.handleCreateCart)
+	mux.HandleFunc("GET /{id}", s.handleGetCart)
+	mux.HandleFunc("PUT /{id}", s.handleUpdateCart)
+	mux.HandleFunc("POST /{id}/cancel", s.handleCancelCart)
+	return withUCPAgent(withJSONContentType(mux))
+}
+
+// ---------------------------------------------------------------------------
+// Checkout HTTP handler mounting
+// ---------------------------------------------------------------------------
+
+// CheckoutHandler returns an http.Handler that routes UCP checkout endpoints.
+// An optional OrderApplier can be provided for real order creation on complete.
+//
+//	mux.Handle("/ucp/v1/checkout-sessions", ucp.CheckoutHandler(pool))
+//	mux.Handle("/ucp/v1/checkout-sessions/", ucp.CheckoutHandler(pool, orderSvc))
+//
+// To sign responses with RFC 9421 HTTP Message Signatures, wrap with WithSigning:
+//
+//	mux.Handle("/ucp/v1/checkout-sessions", ucp.WithSigning(ucp.CheckoutHandler(pool), signer))
+func CheckoutHandler(applier CheckoutApplier, orderSvc ...OrderApplier) http.Handler {
+	s := NewCheckoutServer(applier, orderSvc...)
+	mux := http.NewServeMux()
+	mux.HandleFunc("POST /", s.handleCreateCheckout)
+	mux.HandleFunc("GET /{id}", s.handleGetCheckout)
+	mux.HandleFunc("PUT /{id}", s.handleUpdateCheckout)
+	mux.HandleFunc("POST /{id}/complete", s.handleCompleteCheckout)
+	mux.HandleFunc("POST /{id}/cancel", s.handleCancelCheckout)
+	return withUCPAgent(withJSONContentType(mux))
+}
+
+// ---------------------------------------------------------------------------
+// Customer HTTP handler mounting
+// ---------------------------------------------------------------------------
+
+// CustomerHandler returns an http.Handler that routes UCP customer/profile
+// REST endpoints. Mount it under any prefix (e.g. /ucp/v1) in a ServeMux:
+//
+//	mux.Handle("/ucp/v1/customers", ucp.CustomerHandler(pool))
+//	mux.Handle("/ucp/v1/customers/", ucp.CustomerHandler(pool))
+//
+// To sign responses with RFC 9421 HTTP Message Signatures, wrap with WithSigning:
+//
+//	mux.Handle("/ucp/v1/customers", ucp.WithSigning(ucp.CustomerHandler(pool), signer))
+func CustomerHandler(applier ProfileApplier) http.Handler {
+	s := NewCustomerServer(applier)
+	mux := http.NewServeMux()
+	mux.HandleFunc("POST /", s.handleCreateCustomer)
+	mux.HandleFunc("GET /{id}", s.handleGetCustomer)
+	mux.HandleFunc("PUT /{id}", s.handleUpdateCustomer)
+	mux.HandleFunc("POST /{id}/addresses", s.handleAddAddress)
+	mux.HandleFunc("PUT /{id}/addresses/{addressId}", s.handleUpdateAddress)
+	mux.HandleFunc("DELETE /{id}/addresses/{addressId}", s.handleRemoveAddress)
+	return withUCPAgent(withJSONContentType(mux))
+}
+
+// ---------------------------------------------------------------------------
+// Combined handler for mounting all UCP endpoints under one prefix
+// ---------------------------------------------------------------------------
+
+// Options controls optional features of the combined handler.
+type Options struct {
+	CheckoutApplier CheckoutApplier // when set, mounts /checkout-sessions
+	OrderApplier    OrderApplier    // optional order creation for complete endpoint
+	ProfileApplier  ProfileApplier // when set, mounts /customers + enables identity linking
+}
+
+// Handler returns an http.Handler that serves all mounted UCP endpoints under
+// a single prefix. Usage:
+//
+//	mux.Handle("/ucp/v1/", ucp.Handler(pool, ucp.Options{
+//	    CheckoutApplier: checkoutPool,
+//	    ProfileApplier:  profilePool,
+//	}))
+func Handler(cartApplier CartApplier, opts Options) http.Handler {
+	mux := http.NewServeMux()
+
+	// Cart endpoints
+	cartSrv := NewCartServer(cartApplier)
+	if opts.ProfileApplier != nil {
+		cartSrv.SetProfileApplier(opts.ProfileApplier)
+	}
+	mux.HandleFunc("POST /carts", cartSrv.handleCreateCart)
+	mux.HandleFunc("GET /carts/{id}", cartSrv.handleGetCart)
+	mux.HandleFunc("PUT /carts/{id}", cartSrv.handleUpdateCart)
+	mux.HandleFunc("POST /carts/{id}/cancel", cartSrv.handleCancelCart)
+
+	// Checkout endpoints (optional)
+	if opts.CheckoutApplier != nil {
+		var orderOpts []OrderApplier
+		if opts.OrderApplier != nil {
+			orderOpts = []OrderApplier{opts.OrderApplier}
+		}
+		checkoutSrv := NewCheckoutServer(opts.CheckoutApplier, orderOpts...)
+		if opts.ProfileApplier != nil {
+			checkoutSrv.SetProfileApplier(opts.ProfileApplier)
+		}
+		mux.HandleFunc("POST /checkout-sessions", checkoutSrv.handleCreateCheckout)
+		mux.HandleFunc("GET /checkout-sessions/{id}", checkoutSrv.handleGetCheckout)
+		mux.HandleFunc("PUT /checkout-sessions/{id}", checkoutSrv.handleUpdateCheckout)
+		mux.HandleFunc("POST /checkout-sessions/{id}/complete", checkoutSrv.handleCompleteCheckout)
+		mux.HandleFunc("POST /checkout-sessions/{id}/cancel", checkoutSrv.handleCancelCheckout)
+	}
+
+	// Customer endpoints (optional)
+	if opts.ProfileApplier != nil {
+		customerSrv := NewCustomerServer(opts.ProfileApplier)
+		mux.HandleFunc("POST /customers", customerSrv.handleCreateCustomer)
+		mux.HandleFunc("GET /customers/{id}", customerSrv.handleGetCustomer)
+		mux.HandleFunc("PUT /customers/{id}", customerSrv.handleUpdateCustomer)
+		mux.HandleFunc("POST /customers/{id}/addresses", customerSrv.handleAddAddress)
+		mux.HandleFunc("PUT /customers/{id}/addresses/{addressId}", customerSrv.handleUpdateAddress)
+		mux.HandleFunc("DELETE /customers/{id}/addresses/{addressId}", customerSrv.handleRemoveAddress)
+	}
+
+	return withUCPAgent(withJSONContentType(mux))
+}
+
+// withUCPAgent wraps a handler with UCP-Agent header parsing middleware.
+func withUCPAgent(next http.Handler) http.Handler {
+	return WithUCPAgent(next)
+}
+
+// withJSONContentType is a middleware that ensures all responses have Content-Type: application/json.
+func withJSONContentType(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		next.ServeHTTP(w, r)
+	})
+}

internal/ucp/order.go

@@ -0,0 +1,329 @@
+package ucp
+
+import (
+	"encoding/json"
+	"net/http"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/order"
+	orderMessages "git.k6n.net/mats/go-cart-actor/proto/order"
+)
+
+// OrderServer is the UCP REST adapter over the order grain pool.
+type OrderServer struct {
+	applier OrderReadApplier
+}
+
+// NewOrderServer builds a UCP REST adapter over an order grain pool.
+func NewOrderServer(applier OrderReadApplier) *OrderServer {
+	return &OrderServer{applier: applier}
+}
+
+// ---------------------------------------------------------------------------
+// UCP Order endpoints
+// ---------------------------------------------------------------------------
+
+// handleGetOrder handles GET /orders/{id}.
+func (s *OrderServer) handleGetOrder(w http.ResponseWriter, r *http.Request) {
+	g, err := s.loadOrder(w, r)
+	if err != nil || g == nil {
+		return
+	}
+	writeJSON(w, http.StatusOK, orderGrainToResponse(r.PathValue("id"), g))
+}
+
+// handleCancelOrder handles POST /orders/{id}/cancel.
+func (s *OrderServer) handleCancelOrder(w http.ResponseWriter, r *http.Request) {
+	g, err := s.loadOrder(w, r)
+	if err != nil || g == nil {
+		return
+	}
+	var req struct {
+		Reason string `json:"reason,omitempty"`
+	}
+	_ = json.NewDecoder(r.Body).Decode(&req)
+
+	res, applyErr := s.applier.Apply(r.Context(), g.Id, &orderMessages.CancelOrder{
+		Reason: req.Reason,
+		AtMs:   time.Now().UnixMilli(),
+	})
+	if applyErr != nil || res == nil || mutationRejected(res) {
+		msg := "failed to cancel order"
+		if res != nil && len(res.Mutations) > 0 && res.Mutations[0].Error != nil {
+			msg += ": " + res.Mutations[0].Error.Error()
+		} else if applyErr != nil {
+			msg += ": " + applyErr.Error()
+		}
+		writeError(w, http.StatusUnprocessableEntity, msg)
+		return
+	}
+
+	updated, _ := s.applier.Get(r.Context(), g.Id)
+	if updated != nil {
+		writeJSON(w, http.StatusOK, orderGrainToResponse(r.PathValue("id"), updated))
+	} else {
+		writeJSON(w, http.StatusOK, orderGrainToResponse(r.PathValue("id"), g))
+	}
+}
+
+// handleCreateFulfillment handles POST /orders/{id}/fulfillments.
+func (s *OrderServer) handleCreateFulfillment(w http.ResponseWriter, r *http.Request) {
+	g, err := s.loadOrder(w, r)
+	if err != nil || g == nil {
+		return
+	}
+
+	var req struct {
+		Carrier        string `json:"carrier,omitempty"`
+		TrackingNumber string `json:"trackingNumber,omitempty"`
+		TrackingURI    string `json:"trackingUri,omitempty"`
+		Lines          []struct {
+			Reference string `json:"reference"`
+			Quantity  int32  `json:"quantity"`
+		} `json:"lines,omitempty"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body: "+err.Error())
+		return
+	}
+
+	fid, _ := order.NewOrderId()
+	msg := &orderMessages.CreateFulfillment{
+		Id:             "f_" + fid.String(),
+		Carrier:        req.Carrier,
+		TrackingNumber: req.TrackingNumber,
+		TrackingUri:    req.TrackingURI,
+		AtMs:           time.Now().UnixMilli(),
+	}
+	for _, l := range req.Lines {
+		msg.Lines = append(msg.Lines, &orderMessages.FulfillmentLine{Reference: l.Reference, Quantity: l.Quantity})
+	}
+
+	res, applyErr := s.applier.Apply(r.Context(), g.Id, msg)
+	if applyErr != nil || res == nil || mutationRejected(res) {
+		msg := "failed to create fulfillment"
+		if res != nil && len(res.Mutations) > 0 && res.Mutations[0].Error != nil {
+			msg += ": " + res.Mutations[0].Error.Error()
+		} else if applyErr != nil {
+			msg += ": " + applyErr.Error()
+		}
+		writeError(w, http.StatusUnprocessableEntity, msg)
+		return
+	}
+
+	updated, _ := s.applier.Get(r.Context(), g.Id)
+	writeJSON(w, http.StatusOK, orderGrainToResponse(r.PathValue("id"), updated))
+}
+
+// handleRequestReturn handles POST /orders/{id}/returns.
+func (s *OrderServer) handleRequestReturn(w http.ResponseWriter, r *http.Request) {
+	g, err := s.loadOrder(w, r)
+	if err != nil || g == nil {
+		return
+	}
+
+	var req struct {
+		Reason string `json:"reason,omitempty"`
+		Lines  []struct {
+			Reference string `json:"reference"`
+			Quantity  int32  `json:"quantity"`
+		} `json:"lines,omitempty"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body: "+err.Error())
+		return
+	}
+
+	rid, _ := order.NewOrderId()
+	msg := &orderMessages.RequestReturn{
+		Id:     "r_" + rid.String(),
+		Reason: req.Reason,
+		AtMs:   time.Now().UnixMilli(),
+	}
+	for _, l := range req.Lines {
+		msg.Lines = append(msg.Lines, &orderMessages.FulfillmentLine{Reference: l.Reference, Quantity: l.Quantity})
+	}
+
+	res, applyErr := s.applier.Apply(r.Context(), g.Id, msg)
+	if applyErr != nil || res == nil || mutationRejected(res) {
+		msg := "failed to request return"
+		if res != nil && len(res.Mutations) > 0 && res.Mutations[0].Error != nil {
+			msg += ": " + res.Mutations[0].Error.Error()
+		} else if applyErr != nil {
+			msg += ": " + applyErr.Error()
+		}
+		writeError(w, http.StatusUnprocessableEntity, msg)
+		return
+	}
+
+	updated, _ := s.applier.Get(r.Context(), g.Id)
+	writeJSON(w, http.StatusOK, orderGrainToResponse(r.PathValue("id"), updated))
+}
+
+// handleIssueRefund handles POST /orders/{id}/refunds.
+func (s *OrderServer) handleIssueRefund(w http.ResponseWriter, r *http.Request) {
+	g, err := s.loadOrder(w, r)
+	if err != nil || g == nil {
+		return
+	}
+
+	var req struct {
+		Amount int64 `json:"amount,omitempty"` // minor units; omit for full remaining
+	}
+	_ = json.NewDecoder(r.Body).Decode(&req)
+
+	amount := req.Amount
+	if amount <= 0 {
+		amount = g.CapturedAmount - g.RefundedAmount
+	}
+	if amount <= 0 {
+		writeError(w, http.StatusBadRequest, "no captured amount to refund")
+		return
+	}
+
+	idStr := order.OrderId(g.Id).String()
+	res, applyErr := s.applier.Apply(r.Context(), g.Id, &orderMessages.IssueRefund{
+		Provider:  "ucp",
+		Amount:    amount,
+		Reference: "ref-ucp-" + idStr,
+		AtMs:      time.Now().UnixMilli(),
+	})
+	if applyErr != nil || res == nil || mutationRejected(res) {
+		msg := "failed to issue refund"
+		if res != nil && len(res.Mutations) > 0 && res.Mutations[0].Error != nil {
+			msg += ": " + res.Mutations[0].Error.Error()
+		} else if applyErr != nil {
+			msg += ": " + applyErr.Error()
+		}
+		writeError(w, http.StatusUnprocessableEntity, msg)
+		return
+	}
+
+	updated, _ := s.applier.Get(r.Context(), g.Id)
+	writeJSON(w, http.StatusOK, orderGrainToResponse(r.PathValue("id"), updated))
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+// mutationRejected returns true if the Apply result indicates the mutation was
+// rejected (business-rule violation rather than infrastructure error).
+func mutationRejected(res *actor.MutationResult[order.OrderGrain]) bool {
+	return len(res.Mutations) > 0 && res.Mutations[0].Error != nil
+}
+
+// loadOrder parses the id from the path and returns the grain, or writes an
+// error response and returns nil.
+func (s *OrderServer) loadOrder(w http.ResponseWriter, r *http.Request) (*order.OrderGrain, error) {
+	raw := r.PathValue("id")
+	if raw == "" {
+		writeError(w, http.StatusBadRequest, "missing order id")
+		return nil, nil
+	}
+	id, ok := order.ParseOrderId(raw)
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid order id")
+		return nil, nil
+	}
+	g, err := s.applier.Get(r.Context(), uint64(id))
+	if err != nil {
+		writeError(w, http.StatusNotFound, "order not found")
+		return nil, nil
+	}
+	if g.Status == order.StatusNew {
+		writeError(w, http.StatusNotFound, "order not found")
+		return nil, nil
+	}
+	return g, nil
+}
+
+// orderGrainToResponse converts an OrderGrain to an OrderResponse.
+func orderGrainToResponse(id string, g *order.OrderGrain) OrderResponse {
+	resp := OrderResponse{
+		OrderId:     id,
+		Reference:   g.OrderReference,
+		Status:      string(g.Status),
+		Currency:    g.Currency,
+		TotalAmount: g.TotalAmount,
+		TotalTax:    g.TotalTax,
+		Lines:       make([]OrderLineResp, 0, len(g.Lines)),
+		Payments:    make([]OrderPaymentResp, 0, len(g.Payments)),
+		Fulfillments: make([]OrderFulfillmentResp, 0, len(g.Fulfillments)),
+		Returns:     make([]OrderReturnResp, 0, len(g.Returns)),
+		Refunds:     make([]OrderRefundResp, 0, len(g.Refunds)),
+	}
+
+	for _, l := range g.Lines {
+		resp.Lines = append(resp.Lines, OrderLineResp{
+			Reference:   l.Reference,
+			Sku:         l.Sku,
+			Name:        l.Name,
+			Quantity:    l.Quantity,
+			UnitPrice:   l.UnitPrice,
+			TaxRate:     l.TaxRate,
+			TotalAmount: l.TotalAmount,
+			TotalTax:    l.TotalTax,
+			Fulfilled:   l.Fulfilled,
+		})
+	}
+
+	for _, p := range g.Payments {
+		if p == nil {
+			continue
+		}
+		resp.Payments = append(resp.Payments, OrderPaymentResp{
+			Provider:   p.Provider,
+			Authorized: p.Authorized,
+			Captured:   p.Captured,
+			Refunded:   p.Refunded,
+			AuthRef:    p.AuthRef,
+			CaptureRef: p.CaptureRef,
+		})
+	}
+
+	for _, f := range g.Fulfillments {
+		lines := make([]OrderLineEntry, 0, len(f.Lines))
+		for _, l := range f.Lines {
+			lines = append(lines, OrderLineEntry{Reference: l.Reference, Quantity: l.Quantity})
+		}
+		resp.Fulfillments = append(resp.Fulfillments, OrderFulfillmentResp{
+			Id:             f.ID,
+			Carrier:        f.Carrier,
+			TrackingNumber: f.TrackingNumber,
+			TrackingURI:    f.TrackingURI,
+			Lines:          lines,
+		})
+	}
+
+	for _, r := range g.Returns {
+		lines := make([]OrderLineEntry, 0, len(r.Lines))
+		for _, l := range r.Lines {
+			lines = append(lines, OrderLineEntry{Reference: l.Reference, Quantity: l.Quantity})
+		}
+		resp.Returns = append(resp.Returns, OrderReturnResp{
+			Id:     r.ID,
+			Reason: r.Reason,
+			Lines:  lines,
+		})
+	}
+
+	for _, r := range g.Refunds {
+		resp.Refunds = append(resp.Refunds, OrderRefundResp{
+			Provider:  r.Provider,
+			Amount:    r.Amount,
+			Reference: r.Reference,
+		})
+	}
+
+	resp.CapturedAmount = g.CapturedAmount
+	resp.RefundedAmount = g.RefundedAmount
+	resp.CustomerEmail = g.CustomerEmail
+	resp.CustomerName = g.CustomerName
+	resp.CartId = g.CartId
+	resp.PlacedAt = g.PlacedAt
+	resp.UpdatedAt = g.UpdatedAt
+
+	return resp
+}

internal/ucp/order_test.go

@@ -0,0 +1,300 @@
+package ucp
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"git.k6n.net/mats/go-cart-actor/pkg/order"
+	messages "git.k6n.net/mats/go-cart-actor/proto/order"
+	"google.golang.org/protobuf/proto"
+)
+
+// testOrderApplier implements OrderReadApplier with an in-memory map of grains.
+type testOrderApplier struct {
+	grains map[uint64]*order.OrderGrain
+}
+
+func newTestOrderApplier() *testOrderApplier {
+	return &testOrderApplier{
+		grains: make(map[uint64]*order.OrderGrain),
+	}
+}
+
+func (a *testOrderApplier) Get(_ context.Context, id uint64) (*order.OrderGrain, error) {
+	g, ok := a.grains[id]
+	if !ok {
+		// Auto-create so non-existent orders return StatusNew (expected 404).
+		g = order.NewOrderGrain(id, time.UnixMilli(1000000))
+		a.grains[id] = g
+	}
+	return g, nil
+}
+
+func (a *testOrderApplier) Apply(_ context.Context, id uint64, msgs ...proto.Message) (*actor.MutationResult[order.OrderGrain], error) {
+	g, err := a.Get(nil, id)
+	if err != nil {
+		return nil, err
+	}
+	results := make([]actor.ApplyResult, len(msgs))
+	for i, msg := range msgs {
+		results[i] = actor.ApplyResult{Type: string(msg.ProtoReflect().Descriptor().FullName())}
+		switch m := msg.(type) {
+		case *messages.CancelOrder:
+			if g.Status != order.StatusPending && g.Status != order.StatusAuthorized {
+				results[i].Error = errRejected("cannot cancel in status " + string(g.Status))
+				break
+			}
+			g.Status = order.StatusCancelled
+			g.UpdatedAt = time.Now().UTC().Format(time.RFC3339)
+		case *messages.CreateFulfillment:
+			if g.Status != order.StatusCaptured && g.Status != order.StatusPartiallyFulfilled {
+				results[i].Error = errRejected("cannot fulfill in status " + string(g.Status))
+				break
+			}
+			fulfillment := order.Fulfillment{
+				ID:             m.Id,
+				Carrier:        m.Carrier,
+				TrackingNumber: m.TrackingNumber,
+				TrackingURI:    m.TrackingUri,
+			}
+			for _, fl := range m.Lines {
+				fulfillment.Lines = append(fulfillment.Lines, order.FulfillmentEntry{
+					Reference: fl.Reference,
+					Quantity:  int(fl.Quantity),
+				})
+			}
+			g.Fulfillments = append(g.Fulfillments, fulfillment)
+			g.Status = order.StatusFulfilled
+		case *messages.RequestReturn:
+			ret := order.Return{
+				ID:     m.Id,
+				Reason: m.Reason,
+			}
+			for _, fl := range m.Lines {
+				ret.Lines = append(ret.Lines, order.FulfillmentEntry{
+					Reference: fl.Reference,
+					Quantity:  int(fl.Quantity),
+				})
+			}
+			g.Returns = append(g.Returns, ret)
+		case *messages.IssueRefund:
+			g.Refunds = append(g.Refunds, order.Refund{
+				Provider:  m.Provider,
+				Amount:    m.Amount,
+				Reference: m.Reference,
+			})
+			g.RefundedAmount += m.Amount
+			if g.RefundedAmount >= g.CapturedAmount {
+				g.Status = order.StatusRefunded
+			}
+		}
+	}
+	return &actor.MutationResult[order.OrderGrain]{
+		Result:    *g,
+		Mutations: results,
+	}, nil
+}
+
+func errRejected(msg string) *actor.MutationError {
+	return &actor.MutationError{Message: msg}
+}
+
+// seedOrder places an order in the test applier with a given status.
+func seedOrder(a *testOrderApplier, status order.Status) string {
+	id, _ := order.NewOrderId()
+	g, _ := a.Get(nil, uint64(id))
+	g.Status = status
+	g.Currency = "SEK"
+	g.TotalAmount = 10000
+	g.TotalTax = 2000
+	g.Lines = []order.Line{
+		{Reference: "test-1", Sku: "test-1", Name: "Test Item", Quantity: 2, UnitPrice: 5000, TaxRate: 2500, TotalAmount: 10000, TotalTax: 2000},
+	}
+	if status == order.StatusCaptured {
+		g.CapturedAmount = 10000
+	}
+	return id.String()
+}
+
+func TestOrderHandler_GetOrder(t *testing.T) {
+	a := newTestOrderApplier()
+	h := OrderHandler(a)
+	oid := seedOrder(a, order.StatusCaptured)
+
+	req := httptest.NewRequest("GET", "/"+oid, nil)
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp OrderResponse
+	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+	if resp.OrderId != oid {
+		t.Fatalf("expected orderId %q, got %q", oid, resp.OrderId)
+	}
+	if resp.Status != "captured" {
+		t.Fatalf("expected status 'captured', got %q", resp.Status)
+	}
+	if len(resp.Lines) != 1 {
+		t.Fatalf("expected 1 line, got %d", len(resp.Lines))
+	}
+	if resp.Lines[0].Sku != "test-1" {
+		t.Fatalf("expected sku 'test-1', got %q", resp.Lines[0].Sku)
+	}
+}
+
+func TestOrderHandler_GetOrderNotFound(t *testing.T) {
+	a := newTestOrderApplier()
+	h := OrderHandler(a)
+
+	// Non-existent order (not seeded) returns 404.
+	req := httptest.NewRequest("GET", "/nonexistent", nil)
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusNotFound {
+		t.Fatalf("expected 404 for non-existent order (StatusNew -> 404), got %d", rec.Code)
+	}
+}
+
+func TestOrderHandler_CancelOrder(t *testing.T) {
+	a := newTestOrderApplier()
+	h := OrderHandler(a)
+	oid := seedOrder(a, order.StatusAuthorized)
+
+	body := `{"reason": "customer request"}`
+	req := httptest.NewRequest("POST", "/"+oid+"/cancel", strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp OrderResponse
+	json.NewDecoder(rec.Body).Decode(&resp)
+	if resp.Status != "cancelled" {
+		t.Fatalf("expected status 'cancelled', got %q", resp.Status)
+	}
+}
+
+func TestOrderHandler_CancelOrder_IllegalState(t *testing.T) {
+	a := newTestOrderApplier()
+	h := OrderHandler(a)
+	oid := seedOrder(a, order.StatusFulfilled) // can't cancel from fulfilled
+
+	req := httptest.NewRequest("POST", "/"+oid+"/cancel", nil)
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusUnprocessableEntity {
+		t.Fatalf("expected 422 for illegal transition, got %d: %s", rec.Code, rec.Body.String())
+	}
+}
+
+func TestOrderHandler_CreateFulfillment(t *testing.T) {
+	a := newTestOrderApplier()
+	h := OrderHandler(a)
+	oid := seedOrder(a, order.StatusCaptured)
+
+	body := `{"carrier":"PostNord","trackingNumber":"ABC123","lines":[{"reference":"test-1","quantity":2}]}`
+	req := httptest.NewRequest("POST", "/"+oid+"/fulfillments", strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp OrderResponse
+	json.NewDecoder(rec.Body).Decode(&resp)
+	if len(resp.Fulfillments) != 1 {
+		t.Fatalf("expected 1 fulfillment, got %d", len(resp.Fulfillments))
+	}
+	if resp.Fulfillments[0].Carrier != "PostNord" {
+		t.Fatalf("expected carrier 'PostNord', got %q", resp.Fulfillments[0].Carrier)
+	}
+	if resp.Fulfillments[0].TrackingNumber != "ABC123" {
+		t.Fatalf("expected tracking 'ABC123', got %q", resp.Fulfillments[0].TrackingNumber)
+	}
+}
+
+func TestOrderHandler_RequestReturn(t *testing.T) {
+	a := newTestOrderApplier()
+	h := OrderHandler(a)
+	oid := seedOrder(a, order.StatusFulfilled)
+
+	body := `{"reason":"defective","lines":[{"reference":"test-1","quantity":1}]}`
+	req := httptest.NewRequest("POST", "/"+oid+"/returns", strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp OrderResponse
+	json.NewDecoder(rec.Body).Decode(&resp)
+	if len(resp.Returns) != 1 {
+		t.Fatalf("expected 1 return, got %d", len(resp.Returns))
+	}
+	if resp.Returns[0].Reason != "defective" {
+		t.Fatalf("expected reason 'defective', got %q", resp.Returns[0].Reason)
+	}
+}
+
+func TestOrderHandler_IssueRefund(t *testing.T) {
+	a := newTestOrderApplier()
+	h := OrderHandler(a)
+	oid := seedOrder(a, order.StatusCaptured)
+
+	body := `{"amount":3000}`
+	req := httptest.NewRequest("POST", "/"+oid+"/refunds", strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", rec.Code, rec.Body.String())
+	}
+
+	var resp OrderResponse
+	json.NewDecoder(rec.Body).Decode(&resp)
+	if len(resp.Refunds) != 1 {
+		t.Fatalf("expected 1 refund, got %d", len(resp.Refunds))
+	}
+	if resp.Refunds[0].Amount != 3000 {
+		t.Fatalf("expected amount 3000, got %d", resp.Refunds[0].Amount)
+	}
+}
+
+func TestOrderHandler_SignatureIntegration(t *testing.T) {
+	cfg := mustLoadTestKey(t)
+	a := newTestOrderApplier()
+	oid := seedOrder(a, order.StatusCaptured)
+
+	h := WithSigning(OrderHandler(a), cfg)
+	req := httptest.NewRequest("GET", "/"+oid, nil)
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d", rec.Code)
+	}
+	if rec.Header().Get("Signature-Input") == "" {
+		t.Fatal("expected Signature-Input with signing enabled")
+	}
+}

internal/ucp/signing.go

@@ -0,0 +1,183 @@
+package ucp
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/pem"
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// ---------------------------------------------------------------------------
+// SigningConfig — ECDSA P-256 key for RFC 9421 HTTP Message Signatures
+// ---------------------------------------------------------------------------
+
+// SigningConfig holds the ECDSA P-256 private key and key ID for signing UCP
+// HTTP responses with RFC 9421 HTTP Message Signatures. The corresponding
+// public key is published in the UCP profile (signing_keys) and served at
+// /.well-known/ucp so any UCP platform can verify response authenticity.
+type SigningConfig struct {
+	PrivateKey *ecdsa.PrivateKey
+	KeyID      string // matches the kid in the UCP profile signing_keys
+}
+
+// NewSigningConfigFromPEM parses a PEM-encoded ECDSA P-256 private key and
+// returns a SigningConfig ready for use.
+//
+//   data — PEM block containing an EC PRIVATE KEY (PKCS#8 or SEC1)
+//   keyID — the kid matched by the UCP profile signing_keys entry
+func NewSigningConfigFromPEM(pemData []byte, keyID string) (*SigningConfig, error) {
+	block, _ := pem.Decode(pemData)
+	if block == nil {
+		return nil, fmt.Errorf("ucp signing: no PEM block found")
+	}
+
+	var priv any
+	var err error
+	switch block.Type {
+	case "EC PRIVATE KEY":
+		// SEC1 format (openssl ecparam -genkey -name prime256v1)
+		priv, err = x509.ParseECPrivateKey(block.Bytes)
+	case "PRIVATE KEY":
+		// PKCS#8 format
+		priv, err = x509.ParsePKCS8PrivateKey(block.Bytes)
+	default:
+		return nil, fmt.Errorf("ucp signing: unsupported PEM type %q", block.Type)
+	}
+	if err != nil {
+		return nil, fmt.Errorf("ucp signing: parse key: %w", err)
+	}
+
+	ecKey, ok := priv.(*ecdsa.PrivateKey)
+	if !ok {
+		return nil, fmt.Errorf("ucp signing: key is not ECDSA")
+	}
+	if ecKey.Curve != elliptic.P256() {
+		return nil, fmt.Errorf("ucp signing: key is not P-256 (got %s)", ecKey.Curve.Params().Name)
+	}
+
+	return &SigningConfig{PrivateKey: ecKey, KeyID: keyID}, nil
+}
+
+// ---------------------------------------------------------------------------
+// WithSigning — HTTP middleware wrapper for RFC 9421 response signing
+// ---------------------------------------------------------------------------
+
+// WithSigning wraps h with an HTTP middleware that adds RFC 9421 HTTP Message
+// Signatures to every response. The Signature-Input and Signature headers are
+// computed over @status, content-type, and x-ucp-timestamp, signed with the
+// configured ECDSA P-256 key.
+//
+// Mount it on any existing UCP handler:
+//
+//	mux.Handle("/ucp/v1/carts", ucp.WithSigning(ucp.CartHandler(pool), cfg))
+func WithSigning(h http.Handler, cfg *SigningConfig) http.Handler {
+	if cfg == nil || cfg.PrivateKey == nil {
+		return h // pass through without signing
+	}
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		sw := &signedWriter{
+			ResponseWriter: w,
+			cfg:            cfg,
+		}
+		h.ServeHTTP(sw, r)
+	})
+}
+
+// ---------------------------------------------------------------------------
+// signedWriter — response interceptor that adds signature headers
+// ---------------------------------------------------------------------------
+
+type signedWriter struct {
+	http.ResponseWriter
+	cfg         *SigningConfig
+	statusCode  int
+	wroteHeader bool
+}
+
+func (w *signedWriter) WriteHeader(statusCode int) {
+	if w.wroteHeader {
+		return
+	}
+	w.wroteHeader = true
+	w.statusCode = statusCode
+
+	created := time.Now().Unix()
+	w.ResponseWriter.Header().Set("x-ucp-timestamp", strconv.FormatInt(created, 10))
+
+	// Add signature headers before flushing.
+	w.addSignatureHeaders(created)
+
+	w.ResponseWriter.WriteHeader(statusCode)
+}
+
+func (w *signedWriter) Write(p []byte) (int, error) {
+	if !w.wroteHeader {
+		w.WriteHeader(http.StatusOK)
+	}
+	return w.ResponseWriter.Write(p)
+}
+
+// addSignatureHeaders computes and writes the Signature-Input and Signature
+// headers per RFC 9421 §3.2 / §3.3.
+func (w *signedWriter) addSignatureHeaders(created int64) {
+	contentType := w.ResponseWriter.Header().Get("Content-Type")
+	sigTimestamp := strconv.FormatInt(created, 10)
+
+	// Covered components (in order). RFC 9421 §3.2: derived component names
+	// (@status) are bare identifiers; HTTP header field names are sf-strings
+	// and MUST be quoted.
+	components := []string{
+		"@status",
+		`"content-type"`,
+		`"x-ucp-timestamp"`,
+	}
+
+	// Build the signature base string (RFC 9421 §2.2).
+	var base strings.Builder
+	base.WriteString(fmt.Sprintf(`"@status": %d`, w.statusCode))
+	base.WriteByte('\n')
+	base.WriteString(fmt.Sprintf(`"content-type": %s`, contentType))
+	base.WriteByte('\n')
+	base.WriteString(fmt.Sprintf(`"x-ucp-timestamp": %s`, sigTimestamp))
+	base.WriteByte('\n')
+
+	// Append the signature-params pseudo-line (RFC 9421 §2.2).
+	compList := strings.Join(components, " ")
+	base.WriteString(fmt.Sprintf(`"@signature-params": (%s);created=%d;keyid=%q;alg="ecdsa-p256"`,
+		compList, created, w.cfg.KeyID))
+
+	// Sign the SHA-256 digest.
+	digest := sha256.Sum256([]byte(base.String()))
+	r, s, err := ecdsa.Sign(rand.Reader, w.cfg.PrivateKey, digest[:])
+	if err != nil {
+		// Fail open — response is sent without signature headers.
+		return
+	}
+
+	// ECDSA P-256 signature raw bytes: r||s concatenation, each 32 bytes.
+	rBytes := r.Bytes()
+	sBytes := s.Bytes()
+	rawSig := make([]byte, 64)
+	copy(rawSig[32-len(rBytes):32], rBytes)
+	copy(rawSig[64-len(sBytes):64], sBytes)
+
+	sigB64 := base64.RawURLEncoding.EncodeToString(rawSig)
+
+	// Signature-Input: sig1=(components);created=N;keyid="...";alg="ecdsa-p256"
+	sigInput := fmt.Sprintf(`sig1=(%s);created=%d;keyid=%q;alg="ecdsa-p256"`,
+		compList, created, w.cfg.KeyID)
+
+	// Signature: sig1=:base64url:
+	sigValue := fmt.Sprintf("sig1=:%s:", sigB64)
+
+	w.ResponseWriter.Header().Set("Signature-Input", sigInput)
+	w.ResponseWriter.Header().Set("Signature", sigValue)
+}

internal/ucp/signing_test.go

@@ -0,0 +1,173 @@
+package ucp
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func TestSigningConfig_FromPEM(t *testing.T) {
+	// PEM from the generated key pair (openssl ecparam -genkey -name prime256v1)
+	pemData := `-----BEGIN EC PRIVATE KEY-----
+MHcCAQEEIDTssEctnrEqym80fx2jEVolTW+tWrHyo8fmbi8hMFWmoAoGCCqGSM49
+AwEHoUQDQgAEpnPksDSSMcNgUYT4++Z6XuS0V2p6TNMSjWBsgXOu7mo5Esoux+Cm
+y+C84ty5VUAdEpoDyNfWMeaAlHKGo+FjiQ==
+-----END EC PRIVATE KEY-----`
+
+	cfg, err := NewSigningConfigFromPEM([]byte(pemData), "k6n-ecdsa-2026")
+	if err != nil {
+		t.Fatalf("NewSigningConfigFromPEM failed: %v", err)
+	}
+	if cfg.KeyID != "k6n-ecdsa-2026" {
+		t.Fatalf("expected key ID 'k6n-ecdsa-2026', got %q", cfg.KeyID)
+	}
+	if cfg.PrivateKey == nil {
+		t.Fatal("expected non-nil private key")
+	}
+	if cfg.PrivateKey.Curve.Params().Name != "P-256" {
+		t.Fatalf("expected P-256 curve, got %s", cfg.PrivateKey.Curve.Params().Name)
+	}
+}
+
+func TestSigningConfig_InvalidPEM(t *testing.T) {
+	_, err := NewSigningConfigFromPEM([]byte("not a pem"), "test")
+	if err == nil {
+		t.Fatal("expected error for invalid PEM")
+	}
+}
+
+func TestWithSigning_AddsHeaders(t *testing.T) {
+	// Load the test key.
+	cfg := mustLoadTestKey(t)
+
+	// A simple handler that returns a JSON response.
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+		json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
+	})
+
+	wrapped := WithSigning(handler, cfg)
+	req := httptest.NewRequest("GET", "/test", nil)
+	rec := httptest.NewRecorder()
+	wrapped.ServeHTTP(rec, req)
+
+	// Check the response body.
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d", rec.Code)
+	}
+
+	// Check that signature headers are present.
+	sigInput := rec.Header().Get("Signature-Input")
+	sig := rec.Header().Get("Signature")
+	ts := rec.Header().Get("x-ucp-timestamp")
+
+	if sigInput == "" {
+		t.Fatal("expected Signature-Input header")
+	}
+	if sig == "" {
+		t.Fatal("expected Signature header")
+	}
+	if ts == "" {
+		t.Fatal("expected x-ucp-timestamp header")
+	}
+
+	// Verify the signature input format.
+	if !strings.HasPrefix(sigInput, `sig1=(@status "content-type" "x-ucp-timestamp");`) {
+		t.Fatalf("unexpected Signature-Input format: %q", sigInput)
+	}
+	if !strings.Contains(sigInput, `keyid="k6n-ecdsa-2026"`) {
+		t.Fatalf("Signature-Input missing keyid: %q", sigInput)
+	}
+	if !strings.Contains(sigInput, `alg="ecdsa-p256"`) {
+		t.Fatalf("Signature-Input missing alg: %q", sigInput)
+	}
+
+	// Verify the signature format.
+	if !strings.HasPrefix(sig, "sig1=:") || !strings.HasSuffix(sig, ":") {
+		t.Fatalf("unexpected Signature format: %q", sig)
+	}
+}
+
+func TestWithSigning_NilConfig(t *testing.T) {
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("ok"))
+	})
+
+	wrapped := WithSigning(handler, nil)
+	req := httptest.NewRequest("GET", "/test", nil)
+	rec := httptest.NewRecorder()
+	wrapped.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d", rec.Code)
+	}
+	if rec.Header().Get("Signature-Input") != "" {
+		t.Fatal("expected no Signature-Input when signing is nil")
+	}
+}
+
+func TestWithSigning_DifferentStatuses(t *testing.T) {
+	cfg := mustLoadTestKey(t)
+
+	for _, status := range []int{200, 201, 400, 404, 500} {
+		handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(status)
+			w.Write([]byte(`{}`))
+		})
+
+		wrapped := WithSigning(handler, cfg)
+		req := httptest.NewRequest("GET", "/test", nil)
+		rec := httptest.NewRecorder()
+		wrapped.ServeHTTP(rec, req)
+
+		if rec.Code != status {
+			t.Fatalf("expected status %d, got %d", status, rec.Code)
+		}
+		if rec.Header().Get("Signature-Input") == "" {
+			t.Fatalf("expected Signature-Input for status %d", status)
+		}
+	}
+}
+
+func TestWithSigning_WithUCPCartHandler(t *testing.T) {
+	cfg := mustLoadTestKey(t)
+	applier := newTestApplier()
+	handler := CartHandler(applier)
+	wrapped := WithSigning(handler, cfg)
+
+	// Create a cart through the wrapped handler.
+	req := httptest.NewRequest("POST", "/", nil)
+	rec := httptest.NewRecorder()
+	wrapped.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusCreated {
+		t.Fatalf("expected 201, got %d", rec.Code)
+	}
+
+	// Verify signed.
+	if rec.Header().Get("Signature-Input") == "" {
+		t.Fatal("expected Signature-Input on UCP cart response")
+	}
+	if rec.Header().Get("x-ucp-timestamp") == "" {
+		t.Fatal("expected x-ucp-timestamp on UCP cart response")
+	}
+}
+
+// mustLoadTestKey loads the test PEM for signing tests.
+func mustLoadTestKey(t testing.TB) *SigningConfig {
+	t.Helper()
+	pemData := `-----BEGIN EC PRIVATE KEY-----
+MHcCAQEEIDTssEctnrEqym80fx2jEVolTW+tWrHyo8fmbi8hMFWmoAoGCCqGSM49
+AwEHoUQDQgAEpnPksDSSMcNgUYT4++Z6XuS0V2p6TNMSjWBsgXOu7mo5Esoux+Cm
+y+C84ty5VUAdEpoDyNfWMeaAlHKGo+FjiQ==
+-----END EC PRIVATE KEY-----`
+	cfg, err := NewSigningConfigFromPEM([]byte(pemData), "k6n-ecdsa-2026")
+	if err != nil {
+		t.Fatalf("mustLoadTestKey: %v", err)
+	}
+	return cfg
+}

internal/ucp/types.go

@@ -0,0 +1,479 @@
+// Package ucp provides a Universal Commerce Protocol (UCP) REST adapter for
+// the cart and checkout grain pools. It translates UCP-standard cart/checkout
+// endpoints (POST /carts, GET /carts/{id}, POST /checkout-sessions, …) into
+// grain pool Get/Apply calls, so any UCP-compatible platform or AI agent can
+// interact with the business without a bespoke integration.
+//
+// Transport: REST (JSON over HTTP, following the UCP Shopping Service spec).
+//
+// Current capabilities:
+//   - Cart:  create, read, update items, cancel/clear
+//   - Checkout:  initiate session, read, update, complete, cancel
+//
+// Mount on any existing HTTP mux via ucp.NewCartHandler(…) and
+// ucp.NewCheckoutHandler(…).
+package ucp
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/cart"
+	"git.k6n.net/mats/go-cart-actor/pkg/checkout"
+	"git.k6n.net/mats/go-cart-actor/pkg/order"
+	"git.k6n.net/mats/go-cart-actor/pkg/profile"
+	"git.k6n.net/mats/go-cart-actor/pkg/actor"
+	"google.golang.org/protobuf/proto"
+)
+
+// ---------------------------------------------------------------------------
+// Applier interfaces (same pattern as the MCP packages)
+// ---------------------------------------------------------------------------
+
+// CartApplier is the minimal grain-pool interface the UCP cart adapter needs.
+type CartApplier interface {
+	Get(ctx context.Context, id uint64) (*cart.CartGrain, error)
+	Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*actor.MutationResult[cart.CartGrain], error)
+}
+
+// CheckoutApplier is the minimal grain-pool interface the UCP checkout adapter needs.
+type CheckoutApplier interface {
+	Get(ctx context.Context, id uint64) (*checkout.CheckoutGrain, error)
+	Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*actor.MutationResult[checkout.CheckoutGrain], error)
+}
+
+// OrderReadApplier is the minimal grain-pool interface the UCP order adapter
+// needs to read and mutate order grains.
+type OrderReadApplier interface {
+	Get(ctx context.Context, id uint64) (*order.OrderGrain, error)
+	Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*actor.MutationResult[order.OrderGrain], error)
+}
+
+// ProfileApplier is the minimal grain-pool interface the UCP customer adapter needs.
+type ProfileApplier interface {
+	Get(ctx context.Context, id uint64) (*profile.ProfileGrain, error)
+	Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*actor.MutationResult[profile.ProfileGrain], error)
+}
+
+// OrderApplier is the interface the UCP checkout adapter uses to create a real
+// order from a completed checkout session. It abstracts over the transport
+// (direct grain pool, HTTP, etc.) so the adapter is portable.
+//
+// The checkout adapter calls CreateOrder in handleCompleteCheckout when the
+// optional order applier is configured. Without it, the endpoint falls back to
+// a simplified no-op order reference.
+type OrderApplier interface {
+	// CreateOrder creates a real order from the checkout session after payment
+	// has been completed. It returns the order ID string.
+	//
+	//   checkoutID — the checkout grain's numeric id
+	//   g          — the checkout grain's full state (items, deliveries, contact, …)
+	//   provider   — payment provider that settled the payment (e.g. "adyen", "klarna")
+	//   reference  — PSP / payment reference
+	//   currency   — ISO 4217 currency code (e.g. "SEK")
+	//   country    — ISO 3166-1 alpha-2 country code (e.g. "SE")
+	CreateOrder(ctx context.Context, checkoutID uint64, g *checkout.CheckoutGrain, provider, reference, currency, country string) (string, error)
+}
+
+// ---------------------------------------------------------------------------
+// UCP Cart types (mapped from the UCP Shopping Service REST spec)
+// ---------------------------------------------------------------------------
+
+// CreateCartRequest is the body for POST /carts. Optional — when empty, a fresh
+// empty cart is created. When items are supplied the cart is seeded.
+type CreateCartRequest struct {
+	Items []CartItemInput `json:"items,omitempty"`
+}
+
+// UpdateCartRequest is the body for PUT /carts/{id}. It carries the full or
+// partial cart state to replace.
+type UpdateCartRequest struct {
+	Items    []CartItemInput `json:"items,omitempty"`
+	Vouchers []VoucherInput  `json:"vouchers,omitempty"`
+	UserId   *string         `json:"userId,omitempty"`
+	Country  string          `json:"country,omitempty"`
+}
+
+// CartItemInput is the UCP wire format for an item being added/updated.
+type CartItemInput struct {
+	Sku      string            `json:"sku"`
+	Quantity int               `json:"quantity,omitempty"`
+	Name     string            `json:"name,omitempty"`
+	Price    int64             `json:"price,omitempty"`     // inc-vat in minor units (öre)
+	TaxRate  float64           `json:"taxRate,omitempty"`   // e.g. 25 or 12.5
+	Image    string            `json:"image,omitempty"`
+	StoreId  *string           `json:"storeId,omitempty"`
+	Children []CartItemInput   `json:"children,omitempty"`
+	Fields   map[string]string `json:"customFields,omitempty"`
+}
+
+// VoucherInput is the UCP wire format for a voucher code to apply.
+type VoucherInput struct {
+	Code  string `json:"code"`
+	Value int64  `json:"value,omitempty"`
+}
+
+// CartResponse is the UCP cart response body.
+type CartResponse struct {
+	Id     string         `json:"id"`
+	Items  []CartItem     `json:"items,omitempty"`
+	Totals Totals         `json:"totals"`
+	Status string         `json:"status"`
+}
+
+// CartItem is the UCP wire format for a cart line item in responses.
+type CartItem struct {
+	Sku        string            `json:"sku"`
+	Quantity   int               `json:"quantity"`
+	Name       string            `json:"name,omitempty"`
+	UnitPrice  int64             `json:"unitPrice"`      // inc-vat minor units
+	TotalPrice int64             `json:"totalPrice"`     // inc-vat minor units
+	TaxRate    int               `json:"taxRate"`
+	Image      string            `json:"image,omitempty"`
+	ItemId     uint32            `json:"itemId,omitempty"`
+	Fields     map[string]string `json:"customFields,omitempty"`
+}
+
+// Totals is the UCP wire format for price breakdown.
+type Totals struct {
+	TotalIncVat int64             `json:"totalIncVat"`
+	TotalExVat  int64             `json:"totalExVat"`
+	TotalVat    int64             `json:"totalVat"`
+	Currency    string            `json:"currency"`
+	Discount    int64             `json:"discount,omitempty"`
+}
+
+// ---------------------------------------------------------------------------
+// UCP Checkout types
+// ---------------------------------------------------------------------------
+
+// CreateCheckoutRequest is the body for POST /checkout-sessions.
+type CreateCheckoutRequest struct {
+	CartId     string          `json:"cartId"`
+	Items      []CartItemInput `json:"items,omitempty"`
+	LineItems  []CartItemInput `json:"line_items,omitempty"`
+	Country    string          `json:"country,omitempty"`
+	Currency   string          `json:"currency,omitempty"`
+	CustomerId string          `json:"customerId,omitempty"` // profile ID for identity linking
+}
+
+// UpdateCheckoutRequest is the body for PUT /checkout-sessions/{id}.
+type UpdateCheckoutRequest struct {
+	Delivery    *DeliveryInput    `json:"delivery,omitempty"`
+	Contact     *ContactInput     `json:"contact,omitempty"`
+	PickupPoint *PickupPointInput `json:"pickupPoint,omitempty"`
+}
+
+// DeliveryInput carries a delivery option for a checkout session.
+type DeliveryInput struct {
+	Provider string   `json:"provider"`
+	ItemIds  []uint32 `json:"itemIds,omitempty"`
+}
+
+// ContactInput carries contact details for a checkout session.
+type ContactInput struct {
+	Email      *string `json:"email,omitempty"`
+	Phone      *string `json:"phone,omitempty"`
+	Name       *string `json:"name,omitempty"`
+	PostalCode *string `json:"postalCode,omitempty"`
+}
+
+// PickupPointInput carries a pickup point for a delivery.
+type PickupPointInput struct {
+	DeliveryId uint32  `json:"deliveryId"`
+	Id         string  `json:"id"`
+	Name       *string `json:"name,omitempty"`
+	Address    *string `json:"address,omitempty"`
+	City       *string `json:"city,omitempty"`
+	Zip        *string `json:"zip,omitempty"`
+}
+
+// CompleteCheckoutRequest is the body for POST /checkout-sessions/{id}/complete.
+type CompleteCheckoutRequest struct {
+	PaymentToken string `json:"paymentToken,omitempty"`
+	Provider     string `json:"provider,omitempty"`
+	Currency     string `json:"currency,omitempty"`
+	Country      string `json:"country,omitempty"`
+	CustomerId   string `json:"customerId,omitempty"` // profile ID for identity linking
+}
+
+// CheckoutResponse is the UCP checkout session response.
+type CheckoutResponse struct {
+	Id              string             `json:"id"`
+	CartId          string             `json:"cartId"`
+	Status          string             `json:"status"`
+	Items           []CartItem         `json:"items,omitempty"`
+	Totals          Totals             `json:"totals"`
+	Deliveries      []DeliveryResponse `json:"deliveries,omitempty"`
+	Contact         *ContactResponse   `json:"contact,omitempty"`
+	OrderId         *string            `json:"orderId,omitempty"`
+	Payments        []PaymentResponse  `json:"payments,omitempty"`
+}
+
+// DeliveryResponse is the UCP wire format for a delivery option.
+type DeliveryResponse struct {
+	Id          uint32            `json:"id"`
+	Provider    string            `json:"provider"`
+	Price       int64             `json:"price"`
+	Items       []uint32          `json:"items"`
+	PickupPoint *PickupPointResp  `json:"pickupPoint,omitempty"`
+}
+
+// PickupPointResp is the UCP wire format for a pickup point.
+type PickupPointResp struct {
+	Id      string  `json:"id"`
+	Name    *string `json:"name,omitempty"`
+	Address *string `json:"address,omitempty"`
+	City    *string `json:"city,omitempty"`
+	Zip     *string `json:"zip,omitempty"`
+}
+
+// ContactResponse is the UCP wire format for contact details.
+type ContactResponse struct {
+	Email      *string `json:"email,omitempty"`
+	Phone      *string `json:"phone,omitempty"`
+	Name       *string `json:"name,omitempty"`
+	PostalCode *string `json:"postalCode,omitempty"`
+}
+
+// PaymentResponse is the UCP wire format for a payment record.
+type PaymentResponse struct {
+	Id       string  `json:"id"`
+	Provider string  `json:"provider"`
+	Amount   int64   `json:"amount"`
+	Currency string  `json:"currency"`
+	Status   string  `json:"status"`
+}
+
+// ---------------------------------------------------------------------------
+// UCP Order types
+// ---------------------------------------------------------------------------
+
+// OrderResponse is the UCP order response body.
+type OrderResponse struct {
+	OrderId     string              `json:"orderId"`
+	Reference   string              `json:"reference,omitempty"`
+	CartId      string              `json:"cartId,omitempty"`
+	Status      string              `json:"status"`
+	Currency    string              `json:"currency,omitempty"`
+	TotalAmount int64               `json:"totalAmount"`
+	TotalTax    int64               `json:"totalTax"`
+	Lines       []OrderLineResp     `json:"lines,omitempty"`
+	Payments    []OrderPaymentResp  `json:"payments,omitempty"`
+	Fulfillments []OrderFulfillmentResp `json:"fulfillments,omitempty"`
+	Returns     []OrderReturnResp   `json:"returns,omitempty"`
+	Refunds     []OrderRefundResp   `json:"refunds,omitempty"`
+	CapturedAmount int64            `json:"capturedAmount"`
+	RefundedAmount int64            `json:"refundedAmount"`
+	CustomerEmail   string          `json:"customerEmail,omitempty"`
+	CustomerName    string          `json:"customerName,omitempty"`
+	PlacedAt        string          `json:"placedAt,omitempty"`
+	UpdatedAt       string          `json:"updatedAt,omitempty"`
+}
+
+// OrderLineResp represents a single order line item in responses.
+type OrderLineResp struct {
+	Reference   string `json:"reference"`
+	Sku         string `json:"sku"`
+	Name        string `json:"name,omitempty"`
+	Quantity    int    `json:"quantity"`
+	UnitPrice   int64  `json:"unitPrice"`
+	TaxRate     int    `json:"taxRate"`
+	TotalAmount int64  `json:"totalAmount"`
+	TotalTax    int64  `json:"totalTax"`
+	Fulfilled   int    `json:"fulfilled,omitempty"`
+}
+
+// OrderPaymentResp represents a payment record on an order.
+type OrderPaymentResp struct {
+	Provider   string `json:"provider"`
+	Authorized int64  `json:"authorized"`
+	Captured   int64  `json:"captured"`
+	Refunded   int64  `json:"refunded"`
+	AuthRef    string `json:"authRef,omitempty"`
+	CaptureRef string `json:"captureRef,omitempty"`
+}
+
+// OrderFulfillmentResp represents a shipment record.
+type OrderFulfillmentResp struct {
+	Id             string           `json:"id"`
+	Carrier        string           `json:"carrier,omitempty"`
+	TrackingNumber string           `json:"trackingNumber,omitempty"`
+	TrackingURI    string           `json:"trackingUri,omitempty"`
+	Lines          []OrderLineEntry `json:"lines,omitempty"`
+}
+
+// OrderReturnResp represents a return request (RMA).
+type OrderReturnResp struct {
+	Id     string           `json:"id"`
+	Reason string           `json:"reason,omitempty"`
+	Lines  []OrderLineEntry `json:"lines,omitempty"`
+}
+
+// OrderRefundResp represents a refund record.
+type OrderRefundResp struct {
+	Provider  string `json:"provider"`
+	Amount    int64  `json:"amount"`
+	Reference string `json:"reference,omitempty"`
+}
+
+// OrderLineEntry is a lightweight reference+quantity pair used in fulfillment
+// and return line lists.
+type OrderLineEntry struct {
+	Reference string `json:"reference"`
+	Quantity  int    `json:"quantity"`
+}
+
+// ---------------------------------------------------------------------------
+// UCP Customer types
+// ---------------------------------------------------------------------------
+
+// CustomerResponse is the UCP customer profile response body.
+type CustomerResponse struct {
+	Id        string            `json:"id"`
+	Name      string            `json:"name,omitempty"`
+	Email     string            `json:"email,omitempty"`
+	Phone     string            `json:"phone,omitempty"`
+	Language  string            `json:"language,omitempty"`
+	Currency  string            `json:"currency,omitempty"`
+	AvatarUrl string            `json:"avatarUrl,omitempty"`
+	Addresses []AddressResponse `json:"addresses,omitempty"`
+}
+
+// AddressResponse is the UCP wire format for an address.
+type AddressResponse struct {
+	Id                uint32 `json:"id"`
+	Label             string `json:"label,omitempty"`
+	FullName          string `json:"fullName,omitempty"`
+	AddressLine1      string `json:"addressLine1"`
+	AddressLine2      string `json:"addressLine2,omitempty"`
+	City              string `json:"city"`
+	State             string `json:"state,omitempty"`
+	Zip               string `json:"zip"`
+	Country           string `json:"country"`
+	Phone             string `json:"phone,omitempty"`
+	IsDefaultShipping bool   `json:"isDefaultShipping"`
+	IsDefaultBilling  bool   `json:"isDefaultBilling"`
+}
+
+// CustomerUpdateRequest is the body for PUT /customers/{id}.
+type CustomerUpdateRequest struct {
+	Name      *string `json:"name,omitempty"`
+	Email     *string `json:"email,omitempty"`
+	Phone     *string `json:"phone,omitempty"`
+	Language  *string `json:"language,omitempty"`
+	Currency  *string `json:"currency,omitempty"`
+	AvatarUrl *string `json:"avatarUrl,omitempty"`
+}
+
+// AddAddressRequest is the body for POST /customers/{id}/addresses.
+type AddAddressRequest struct {
+	Label             string `json:"label,omitempty"`
+	FullName          string `json:"fullName,omitempty"`
+	AddressLine1      string `json:"addressLine1"`
+	AddressLine2      string `json:"addressLine2,omitempty"`
+	City              string `json:"city"`
+	State             string `json:"state,omitempty"`
+	Zip               string `json:"zip"`
+	Country           string `json:"country"`
+	Phone             string `json:"phone,omitempty"`
+	IsDefaultShipping bool   `json:"isDefaultShipping,omitempty"`
+	IsDefaultBilling  bool   `json:"isDefaultBilling,omitempty"`
+}
+
+// UpdateAddressRequest is the body for PUT /customers/{id}/addresses/{addressId}.
+type UpdateAddressRequest struct {
+	Label             *string `json:"label,omitempty"`
+	FullName          *string `json:"fullName,omitempty"`
+	AddressLine1      *string `json:"addressLine1,omitempty"`
+	AddressLine2      *string `json:"addressLine2,omitempty"`
+	City              *string `json:"city,omitempty"`
+	State             *string `json:"state,omitempty"`
+	Zip               *string `json:"zip,omitempty"`
+	Country           *string `json:"country,omitempty"`
+	Phone             *string `json:"phone,omitempty"`
+	IsDefaultShipping *bool   `json:"isDefaultShipping,omitempty"`
+	IsDefaultBilling  *bool   `json:"isDefaultBilling,omitempty"`
+}
+
+// ---------------------------------------------------------------------------
+// UCP Profile handler (/.well-known/ucp)
+// ---------------------------------------------------------------------------
+
+// ProfileData is the UCP business profile served at /.well-known/ucp.
+type ProfileData struct {
+	UCP Profile `json:"ucp"`
+}
+
+// Profile is the core UCP profile object.
+type Profile struct {
+	Version         string                          `json:"version"`
+	Business        BusinessInfo                    `json:"business,omitempty"`
+	Services        map[string][]ServiceBinding      `json:"services"`
+	Capabilities    map[string][]CapabilityDecl      `json:"capabilities"`
+	PaymentHandlers map[string][]PaymentHandlerDecl  `json:"payment_handlers,omitempty"`
+	SupportedVersions []string                       `json:"supported_versions,omitempty"`
+}
+
+// BusinessInfo describes the business behind a UCP profile.
+type BusinessInfo struct {
+	Name        string `json:"name"`
+	Description string `json:"description,omitempty"`
+	Domain      string `json:"domain"`
+}
+
+// ServiceBinding describes a transport binding for a service namespace.
+type ServiceBinding struct {
+	Version   string `json:"version"`
+	Spec      string `json:"spec"`
+	Transport string `json:"transport"`
+	Schema    string `json:"schema"`
+	Endpoint  string `json:"endpoint"`
+}
+
+// CapabilityDecl describes a single capability version.
+type CapabilityDecl struct {
+	Version     string  `json:"version"`
+	Spec        string  `json:"spec"`
+	Schema      string  `json:"schema"`
+	Extends     string  `json:"extends,omitempty"`
+	Description string  `json:"description,omitempty"`
+	Operations  []OpDef `json:"operations,omitempty"`
+}
+
+// OpDef describes an operation method+path for a capability.
+type OpDef struct {
+	Method string `json:"method"`
+	Path   string `json:"path"`
+}
+
+// PaymentHandlerDecl describes a payment handler specification.
+type PaymentHandlerDecl struct {
+	ID      string `json:"id"`
+	Version string `json:"version"`
+	Spec    string `json:"spec"`
+	Schema  string `json:"schema"`
+	Description string `json:"description,omitempty"`
+}
+
+// ---------------------------------------------------------------------------
+// HTTP helpers
+// ---------------------------------------------------------------------------
+
+// writeJSON encodes v as JSON and writes it with the given status code.
+func writeJSON(w http.ResponseWriter, status int, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	json.NewEncoder(w).Encode(v)
+}
+
+// errorBody is a simple {"error": "…"} response.
+type errorBody struct {
+	Error string `json:"error"`
+}
+
+// writeError writes a JSON error response.
+func writeError(w http.ResponseWriter, status int, msg string) {
+	writeJSON(w, status, errorBody{Error: msg})
+}

k6/README.md

@@ -0,0 +1,174 @@
+# k6 Load Tests for Cart API
+
+This directory contains a k6 script (`cart_load_test.js`) to stress and observe the cart actor HTTP API.
+
+## Contents
+
+- `cart_load_test.js` – primary k6 scenario script
+- `README.md` – this file
+
+## Prerequisites
+
+- Node not required (k6 runs standalone)
+- k6 installed (>= v0.43 recommended)
+- Prometheus + Grafana (optional) if you want to correlate with the dashboard you generated
+- A running cart service exposing HTTP endpoints at (default) `http://localhost:8080/cart`
+
+## Endpoints Exercised
+
+The script exercises (per iteration):
+
+1. `GET /cart` – ensure / fetch cart state (creates cart if missing; sets `cartid` & `cartowner` cookies)
+2. `POST /cart` – add item mutation (random SKU & quantity)
+3. `GET /cart` – fetch after mutations
+4. `GET /checkout` – occasionally (~2% of iterations) to simulate checkout start
+
+You can extend it easily to hit deliveries, quantity changes, or removal endpoints.
+
+## Environment Variables
+
+| Variable        | Purpose                                      | Default                 |
+|-----------------|----------------------------------------------|-------------------------|
+| `BASE_URL`      | Base URL root (either host or host/cart)     | `http://localhost:8080/cart` |
+| `VUS`           | VUs for steady_mutations scenario            | `20`                    |
+| `DURATION`      | Duration for steady_mutations scenario       | `5m`                    |
+| `RAMP_TARGET`   | Peak VUs for ramp_up scenario                 | `50`                    |
+
+You can also disable one scenario by editing `options.scenarios` inside the script.
+
+Example run:
+
+```bash
+k6 run \
+  -e BASE_URL=https://cart.k6n.net/cart \
+  -e VUS=40 \
+  -e DURATION=1m \
+  -e RAMP_TARGET=120 \
+  k6/cart_load_test.js
+```
+
+## Metrics (Custom)
+
+The script defines additional k6 metrics:
+
+- `cart_add_item_duration` (Trend) – latency of POST add item
+- `cart_fetch_duration` (Trend) – latency of GET cart state
+- `cart_checkout_duration` (Trend) – latency of checkout
+- `cart_items_added` (Counter) – successful add item operations
+- `cart_checkout_calls` (Counter) – successful checkout calls
+
+Thresholds (in `options.thresholds`) enforce basic SLO:
+- Mutation failure rate < 2%
+- p90 mutation latency < 800 ms
+- p99 overall HTTP latency < 1500 ms
+
+Adjust thresholds to your environment if they trigger prematurely.
+
+## Cookies & Stickiness
+
+The script preserves:
+- `cartid` – cart identity (server sets expiry separately)
+- `cartowner` – owning host for sticky routing
+
+If your load balancer or ingress enforces affinity based on these cookies, traffic will naturally concentrate on the originally claimed host for each cart under test.
+
+## SKU Set
+
+SKUs used (randomly selected each mutation):
+
+```
+778290 778345 778317 778277 778267 778376 778244 778384
+778365 778377 778255 778286 778246 778270 778266 778285
+778329 778425 778407 778418 778430 778469 778358 778351
+778319 778307 778278 778251 778253 778261 778263 778273
+778281 778294 778297 778302
+```
+
+To add/remove SKUs, edit the `SKUS` array. Keeping it non-empty and moderately sized helps randomization.
+
+## Extending the Script
+
+### Add Quantity Change
+
+```js
+function changeQuantity(itemId, newQty) {
+  const payload = JSON.stringify({ Id: itemId, Qty: newQty });
+  http.put(baseUrl() + '/', payload, { headers: headers() });
+}
+```
+
+### Remove Item
+
+```js
+function removeItem(itemId) {
+  http.del(baseUrl() + '/' + itemId, null, { headers: headers() });
+}
+```
+
+### Add Delivery
+
+```js
+function addDelivery(itemIds) {
+  const payload = JSON.stringify({ provider: "POSTNORD", items: itemIds });
+  http.post(baseUrl() + '/delivery', payload, { headers: headers() });
+}
+```
+
+You can integrate these into the iteration loop with probabilities.
+
+## Output Summary
+
+`handleSummary` outputs a JSON summary to stdout:
+- Average & p95 mutation latencies (if present)
+- Fetch p95
+- Checkout count
+- Check statuses
+
+Redirect or parse that output for CI pipelines.
+
+## Running in CI
+
+Use shorter durations (e.g. `DURATION=2m VUS=10`) to keep builds fast. Fail build on threshold breaches:
+
+```bash
+k6 run -e BASE_URL=$TARGET -e VUS=10 -e DURATION=2m k6/cart_load_test.js || exit 1
+```
+
+## Correlating with Prometheus / Grafana
+
+During load, observe:
+- `cart_mutations_total` growth and latency histograms
+- Event log write rate (`cart_event_log_appends_total`)
+- Pool usage (`cart_grain_pool_usage`) and spawn rate (`cart_grain_spawned_total`)
+- Failure counters (`cart_mutation_failures_total`) ensure they remain low
+
+If mutation latency spikes without high error rate, inspect external dependencies (e.g., product fetcher or Klarna endpoints).
+
+## Common Tuning Tips
+
+| Symptom                             | Potential Adjustment                              |
+|------------------------------------|---------------------------------------------------|
+| High latency p99                   | Increase CPU/memory, optimize mutation handlers   |
+| Pool at capacity                   | Raise pool size argument or TTL                   |
+| Frequent cart eviction mid-test    | Confirm TTL is sliding (now 2h on mutation)       |
+| High replay duration               | Consider snapshot + truncate event logs           |
+| Uneven host load                   | Verify `cartowner` cookie is respected upstream   |
+
+## Safety / Load Guardrails
+
+- Start with low VUs (5–10) and short duration.
+- Scale incrementally to find saturation points.
+- If using production endpoints, coordinate off-peak runs.
+
+## License / Attribution
+
+This test script is tailored for your internal cart actor system; adapt freely. k6 is open-source (AGPL v3). Ensure compliance if redistributing.
+
+---
+
+Feel free to request:
+- A variant script for spike tests
+- WebSocket / long poll integration (if added later)
+- Synthetic error injection harness
+
+Happy load testing!

k6/cart_load_test.js

@@ -0,0 +1,244 @@
+import http from "k6/http";
+import { check, sleep, group } from "k6";
+import { Counter, Trend } from "k6/metrics";
+
+// ---------------- Configuration ----------------
+export const options = {
+  // Adjust vus/duration for your environment
+  scenarios: {
+    steady_mutations: {
+      executor: "constant-vus",
+      vus: __ENV.VUS ? parseInt(__ENV.VUS, 10) : 20,
+      duration: __ENV.DURATION || "5m",
+      gracefulStop: "30s",
+    },
+    ramp_up: {
+      executor: "ramping-vus",
+      startVUs: 0,
+      stages: [
+        {
+          duration: "1m",
+          target: __ENV.RAMP_TARGET ? parseInt(__ENV.RAMP_TARGET, 10) : 50,
+        },
+        {
+          duration: "1m",
+          target: __ENV.RAMP_TARGET ? parseInt(__ENV.RAMP_TARGET, 10) : 50,
+        },
+        { duration: "1m", target: 0 },
+      ],
+      gracefulStop: "30s",
+      startTime: "30s",
+    },
+  },
+  thresholds: {
+    http_req_failed: ["rate<0.02"], // < 2% failures
+    http_req_duration: ["p(90)<800", "p(99)<1500"], // latency SLO
+    "cart_add_item_duration{op:add}": ["p(90)<800"],
+    "cart_fetch_duration{op:get}": ["p(90)<600"],
+  },
+  summaryTrendStats: ["avg", "min", "med", "max", "p(90)", "p(95)", "p(99)"],
+};
+
+// ---------------- Metrics ----------------
+const addItemTrend = new Trend("cart_add_item_duration", true);
+const fetchTrend = new Trend("cart_fetch_duration", true);
+const checkoutTrend = new Trend("cart_checkout_duration", true);
+const addedItemsCounter = new Counter("cart_items_added");
+const checkoutCounter = new Counter("cart_checkout_calls");
+
+// ---------------- SKUs ----------------
+const SKUS = [
+  "778290",
+  "778345",
+  "778317",
+  "778277",
+  "778267",
+  "778376",
+  "778244",
+  "778384",
+  "778365",
+  "778377",
+  "778255",
+  "778286",
+  "778246",
+  "778270",
+  "778266",
+  "778285",
+  "778329",
+  "778425",
+  "778407",
+  "778418",
+  "778430",
+  "778469",
+  "778358",
+  "778351",
+  "778319",
+  "778307",
+  "778278",
+  "778251",
+  "778253",
+  "778261",
+  "778263",
+  "778273",
+  "778281",
+  "778294",
+  "778297",
+  "778302",
+];
+
+// ---------------- Helpers ----------------
+function randomSku() {
+  return SKUS[Math.floor(Math.random() * SKUS.length)];
+}
+function randomQty() {
+  return 1 + Math.floor(Math.random() * 3); // 1..3
+}
+function baseUrl() {
+  const u = __ENV.BASE_URL || "http://localhost:8080/cart";
+  // Allow user to pass either root host or full /cart path
+  return u.endsWith("/cart") ? u : u.replace(/\/+$/, "") + "/cart";
+}
+function extractCookie(res, name) {
+  const cookies = res.cookies[name];
+  if (!cookies || cookies.length === 0) return null;
+  return cookies[0].value;
+}
+function withCookies(headers, cookieJar) {
+  if (!cookieJar || Object.keys(cookieJar).length === 0) return headers;
+  const cookieStr = Object.entries(cookieJar)
+    .map(([k, v]) => `${k}=${v}`)
+    .join("; ");
+  return { ...headers, Cookie: cookieStr };
+}
+
+// Maintain cart + owner cookies per VU
+let cartState = {
+  cartid: null,
+  cartowner: null,
+};
+
+// Refresh cookies from response
+function updateCookies(res) {
+  const cid = extractCookie(res, "cartid");
+  if (cid) cartState.cartid = cid;
+  const owner = extractCookie(res, "cartowner");
+  if (owner) cartState.cartowner = owner;
+}
+
+// Build headers
+function headers() {
+  const h = { "Content-Type": "application/json" };
+  const jar = {};
+  if (cartState.cartid) jar["cartid"] = cartState.cartid;
+  if (cartState.cartowner) jar["cartowner"] = cartState.cartowner;
+  return withCookies(h, jar);
+}
+
+// Ensure cart exists (GET /)
+function ensureCart() {
+  if (cartState.cartid) return;
+  const res = http.get(baseUrl(), { headers: headers() });
+  updateCookies(res);
+  check(res, {
+    "ensure cart status 200": (r) => r.status === 200,
+    "ensure cart has id": () => !!cartState.cartid,
+  });
+}
+
+// Add random item
+function addRandomItem() {
+  const payload = JSON.stringify({
+    sku: randomSku(),
+    quantity: randomQty(),
+    country: "no",
+  });
+  const start = Date.now();
+  const res = http.post(baseUrl(), payload, { headers: headers() });
+  const dur = Date.now() - start;
+  addItemTrend.add(dur, { op: "add" });
+  if (res.status === 200) {
+    addedItemsCounter.add(1);
+  }
+  updateCookies(res);
+  check(res, {
+    "add item status ok": (r) => r.status === 200,
+  });
+}
+
+// Fetch cart state
+function fetchCart() {
+  const start = Date.now();
+  const res = http.get(baseUrl(), { headers: headers() });
+  const dur = Date.now() - start;
+  fetchTrend.add(dur, { op: "get" });
+  updateCookies(res);
+  check(res, { "fetch status ok": (r) => r.status === 200 });
+}
+
+// Occasional checkout trigger
+function maybeCheckout() {
+  if (!cartState.cartid) return;
+  // // Small probability
+  // if (Math.random() < 0.02) {
+  //     const start = Date.now();
+  //     const res = http.get(baseUrl() + "/checkout", { headers: headers() });
+  //     const dur = Date.now() - start;
+  //     checkoutTrend.add(dur, { op: "checkout" });
+  //     updateCookies(res);
+  //     if (res.status === 200) checkoutCounter.add(1);
+  //     check(res, { "checkout status ok": (r) => r.status === 200 });
+  // }
+}
+
+// ---------------- k6 lifecycle ----------------
+export function setup() {
+  // Provide SKU list length for summary
+  return { skuCount: SKUS.length };
+}
+
+export default function (data) {
+  group("cart flow", () => {
+    // Create or reuse cart
+    ensureCart();
+
+    // Random number of item mutations per iteration (1..5)
+    const ops = 1 + Math.floor(Math.random() * 5);
+    for (let i = 0; i < ops; i++) {
+      addRandomItem();
+    }
+
+    // Fetch state
+    fetchCart();
+
+    // Optional checkout attempt
+    maybeCheckout();
+  });
+
+  // Small think time
+  sleep(Math.random() * 0.5);
+}
+
+export function teardown(data) {
+  // Optionally we could GET confirmation or clear cart cookie
+  // Not implemented for load purpose.
+  console.log(`Test complete. SKU count: ${data.skuCount}`);
+}
+
+// ---------------- Summary ----------------
+export function handleSummary(data) {
+  return {
+    stdout: JSON.stringify(
+      {
+        metrics: {
+          mutations_avg: data.metrics.cart_add_item_duration?.avg,
+          mutations_p95: data.metrics.cart_add_item_duration?.p(95),
+          fetch_p95: data.metrics.cart_fetch_duration?.p(95),
+          checkout_count: data.metrics.cart_checkout_calls?.count,
+        },
+        checks: data.root_checks,
+      },
+      null,
+      2,
+    ),
+  };
+}

main.go

@@ -1,421 +0,0 @@
-package main
-
-import (
-	"encoding/json"
-	"fmt"
-	"log"
-	"net/http"
-	"net/http/pprof"
-	"os"
-	"os/signal"
-	"strings"
-	"syscall"
-	"time"
-
-	messages "git.tornberg.me/go-cart-actor/proto"
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promauto"
-	"github.com/prometheus/client_golang/prometheus/promhttp"
-	"k8s.io/client-go/kubernetes"
-	"k8s.io/client-go/rest"
-)
-
-var (
-	grainSpawns = promauto.NewCounter(prometheus.CounterOpts{
-		Name: "cart_grain_spawned_total",
-		Help: "The total number of spawned grains",
-	})
-	grainMutations = promauto.NewCounter(prometheus.CounterOpts{
-		Name: "cart_grain_mutations_total",
-		Help: "The total number of mutations",
-	})
-	grainLookups = promauto.NewCounter(prometheus.CounterOpts{
-		Name: "cart_grain_lookups_total",
-		Help: "The total number of lookups",
-	})
-)
-
-func spawn(id CartId) (*CartGrain, error) {
-	grainSpawns.Inc()
-	ret := &CartGrain{
-		lastItemId:      0,
-		lastDeliveryId:  0,
-		Deliveries:      []*CartDelivery{},
-		Id:              id,
-		Items:           []*CartItem{},
-		storageMessages: []Message{},
-		TotalPrice:      0,
-	}
-	err := loadMessages(ret, id)
-	return ret, err
-}
-
-func init() {
-	os.Mkdir("data", 0755)
-}
-
-type App struct {
-	pool    *GrainLocalPool
-	storage *DiskStorage
-}
-
-func (a *App) Save() error {
-	hasChanges := false
-	a.pool.mu.RLock()
-	defer a.pool.mu.RUnlock()
-	for id, grain := range a.pool.GetGrains() {
-		if grain == nil {
-			continue
-		}
-		if grain.GetLastChange() > a.storage.LastSaves[id] {
-			hasChanges = true
-			err := a.storage.Store(id, grain)
-			if err != nil {
-				log.Printf("Error saving grain %s: %v\n", id, err)
-			}
-		}
-	}
-
-	if !hasChanges {
-		return nil
-	}
-	return a.storage.saveState()
-}
-
-func (a *App) HandleSave(w http.ResponseWriter, r *http.Request) {
-	err := a.Save()
-	if err != nil {
-		w.WriteHeader(http.StatusInternalServerError)
-		w.Write([]byte(err.Error()))
-	} else {
-		w.WriteHeader(http.StatusCreated)
-	}
-}
-
-var podIp = os.Getenv("POD_IP")
-var name = os.Getenv("POD_NAME")
-var amqpUrl = os.Getenv("AMQP_URL")
-var KlarnaInstance = NewKlarnaClient(KlarnaPlaygroundUrl, os.Getenv("KLARNA_API_USERNAME"), os.Getenv("KLARNA_API_PASSWORD"))
-
-func GetDiscovery() Discovery {
-	if podIp == "" {
-		return nil
-	}
-
-	config, kerr := rest.InClusterConfig()
-
-	if kerr != nil {
-		log.Fatalf("Error creating kubernetes client: %v\n", kerr)
-	}
-	client, err := kubernetes.NewForConfig(config)
-	if err != nil {
-		log.Fatalf("Error creating client: %v\n", err)
-	}
-	return NewK8sDiscovery(client)
-}
-
-var tpl = `<!DOCTYPE html>
-<html lang="en">
-  <head>
-    <meta charset="UTF-8" />
-    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-    <title>s10r testing - checkout</title>
-  </head>
-
-  <body>
-    %s
-  </body>
-</html>
-`
-
-func getCountryFromHost(host string) string {
-	if strings.Contains(strings.ToLower(host), "-no") {
-		return "no"
-	}
-	return "se"
-}
-
-func getCheckoutOrder(host string, cartId CartId) *messages.CreateCheckoutOrder {
-	baseUrl := fmt.Sprintf("https://%s", host)
-	cartBaseUrl := os.Getenv("CART_BASE_URL")
-	if cartBaseUrl == "" {
-		cartBaseUrl = "https://cart.tornberg.me"
-	}
-	country := getCountryFromHost(host)
-
-	return &messages.CreateCheckoutOrder{
-		Terms:        fmt.Sprintf("%s/terms", baseUrl),
-		Checkout:     fmt.Sprintf("%s/checkout?order_id={checkout.order.id}", baseUrl),
-		Confirmation: fmt.Sprintf("%s/confirmation/{checkout.order.id}", baseUrl),
-		Validation:   fmt.Sprintf("%s/validation", cartBaseUrl),
-		Push:         fmt.Sprintf("%s/push?order_id={checkout.order.id}", cartBaseUrl),
-		Country:      country,
-	}
-}
-
-func main() {
-
-	storage, err := NewDiskStorage(fmt.Sprintf("data/%s_state.gob", name))
-	if err != nil {
-		log.Printf("Error loading state: %v\n", err)
-	}
-	app := &App{
-		pool:    NewGrainLocalPool(65535, 5*time.Minute, spawn),
-		storage: storage,
-	}
-
-	syncedPool, err := NewSyncedPool(app.pool, podIp, GetDiscovery())
-	if err != nil {
-		log.Fatalf("Error creating synced pool: %v\n", err)
-	}
-
-	// Start unified gRPC server (CartActor + ControlPlane) replacing legacy RPC server on :1337
-	// TODO: Remove any remaining legacy RPC server references and deprecated frame-based code after full gRPC migration is validated.
-	grpcSrv, err := StartGRPCServer(":1337", app.pool, syncedPool)
-	if err != nil {
-		log.Fatalf("Error starting gRPC server: %v\n", err)
-	}
-	defer grpcSrv.GracefulStop()
-
-	go func() {
-		for range time.Tick(time.Minute * 10) {
-			err := app.Save()
-			if err != nil {
-				log.Printf("Error saving: %v\n", err)
-			}
-		}
-	}()
-	orderHandler := &AmqpOrderHandler{
-		Url: amqpUrl,
-	}
-
-	syncedServer := NewPoolServer(syncedPool, fmt.Sprintf("%s, %s", name, podIp))
-	mux := http.NewServeMux()
-	mux.Handle("/cart/", http.StripPrefix("/cart", syncedServer.Serve()))
-	// only for local
-	// mux.HandleFunc("GET /add/remote/{host}", func(w http.ResponseWriter, r *http.Request) {
-	// 	syncedPool.AddRemote(r.PathValue("host"))
-	// })
-	// mux.HandleFunc("GET /save", app.HandleSave)
-	//mux.HandleFunc("/", app.RewritePath)
-	mux.HandleFunc("/debug/pprof/", pprof.Index)
-	mux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
-	mux.HandleFunc("/debug/pprof/profile", pprof.Profile)
-	mux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
-	mux.HandleFunc("/debug/pprof/trace", pprof.Trace)
-	mux.Handle("/metrics", promhttp.Handler())
-	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
-		// Grain pool health: simple capacity check (mirrors previous GrainHandler.IsHealthy)
-		app.pool.mu.RLock()
-		grainCount := len(app.pool.grains)
-		capacity := app.pool.PoolSize
-		app.pool.mu.RUnlock()
-		if grainCount >= capacity {
-			w.WriteHeader(http.StatusInternalServerError)
-			w.Write([]byte("grain pool at capacity"))
-			return
-		}
-		if !syncedPool.IsHealthy() {
-			w.WriteHeader(http.StatusInternalServerError)
-			w.Write([]byte("control plane not healthy"))
-			return
-		}
-		w.WriteHeader(http.StatusOK)
-		w.Write([]byte("ok"))
-	})
-	mux.HandleFunc("/readyz", func(w http.ResponseWriter, r *http.Request) {
-		w.WriteHeader(http.StatusOK)
-		w.Write([]byte("ok"))
-	})
-	mux.HandleFunc("/livez", func(w http.ResponseWriter, r *http.Request) {
-		w.WriteHeader(http.StatusOK)
-		w.Write([]byte("ok"))
-	})
-
-	mux.HandleFunc("/checkout", func(w http.ResponseWriter, r *http.Request) {
-		orderId := r.URL.Query().Get("order_id")
-		order := &CheckoutOrder{}
-
-		if orderId == "" {
-			cookie, err := r.Cookie("cartid")
-			if err != nil {
-				w.WriteHeader(http.StatusBadRequest)
-				w.Write([]byte(err.Error()))
-				return
-			}
-			if cookie.Value == "" {
-				w.WriteHeader(http.StatusBadRequest)
-				w.Write([]byte("no cart id to checkout is empty"))
-				return
-			}
-			cartId := ToCartId(cookie.Value)
-			reply, err := syncedServer.pool.Process(cartId, Message{
-				Type:    CreateCheckoutOrderType,
-				Content: getCheckoutOrder(r.Host, cartId),
-			})
-			if err != nil {
-				w.WriteHeader(http.StatusInternalServerError)
-				w.Write([]byte(err.Error()))
-			}
-			err = json.Unmarshal(reply.Payload, &order)
-			if err != nil {
-				w.WriteHeader(http.StatusInternalServerError)
-				w.Write([]byte(err.Error()))
-				return
-			}
-		} else {
-			prevOrder, err := KlarnaInstance.GetOrder(orderId)
-			if err != nil {
-				w.WriteHeader(http.StatusBadRequest)
-				w.Write([]byte(err.Error()))
-				return
-			}
-			order = prevOrder
-		}
-		w.Header().Set("Content-Type", "text/html; charset=utf-8")
-		w.Header().Set("Permissions-Policy", "payment=(self \"https://js.stripe.com\" \"https://m.stripe.network\" \"https://js.playground.kustom.co\")")
-		w.WriteHeader(http.StatusOK)
-		w.Write([]byte(fmt.Sprintf(tpl, order.HTMLSnippet)))
-	})
-	mux.HandleFunc("/confirmation/{order_id}", func(w http.ResponseWriter, r *http.Request) {
-
-		orderId := r.PathValue("order_id")
-		order, err := KlarnaInstance.GetOrder(orderId)
-
-		if err != nil {
-			w.WriteHeader(http.StatusInternalServerError)
-			w.Write([]byte(err.Error()))
-			return
-		}
-
-		w.Header().Set("Content-Type", "text/html; charset=utf-8")
-		if order.Status == "checkout_complete" {
-			http.SetCookie(w, &http.Cookie{
-				Name:     "cartid",
-				Value:    "",
-				Path:     "/",
-				Secure:   true,
-				HttpOnly: true,
-				Expires:  time.Unix(0, 0),
-				SameSite: http.SameSiteLaxMode,
-			})
-		}
-
-		w.WriteHeader(http.StatusOK)
-		w.Write([]byte(fmt.Sprintf(tpl, order.HTMLSnippet)))
-	})
-	mux.HandleFunc("/validate", func(w http.ResponseWriter, r *http.Request) {
-		log.Printf("Klarna order validation, method: %s", r.Method)
-		if r.Method != "POST" {
-			w.WriteHeader(http.StatusMethodNotAllowed)
-			return
-		}
-		order := &CheckoutOrder{}
-		err := json.NewDecoder(r.Body).Decode(order)
-		if err != nil {
-			w.WriteHeader(http.StatusBadRequest)
-		}
-		log.Printf("Klarna order validation: %s", order.ID)
-		//err = confirmOrder(order, orderHandler)
-		//if err != nil {
-		//	log.Printf("Error validating order: %v\n", err)
-		//	w.WriteHeader(http.StatusInternalServerError)
-		//	return
-		//}
-		//
-		//err = triggerOrderCompleted(err, syncedServer, order)
-		//if err != nil {
-		//	log.Printf("Error processing cart message: %v\n", err)
-		//	w.WriteHeader(http.StatusInternalServerError)
-		//	return
-		//}
-		w.WriteHeader(http.StatusOK)
-	})
-	mux.HandleFunc("/push", func(w http.ResponseWriter, r *http.Request) {
-
-		if r.Method != http.MethodPost {
-			w.WriteHeader(http.StatusMethodNotAllowed)
-			return
-		}
-		orderId := r.URL.Query().Get("order_id")
-		log.Printf("Order confirmation push: %s", orderId)
-
-		order, err := KlarnaInstance.GetOrder(orderId)
-
-		if err != nil {
-			log.Printf("Error creating request: %v\n", err)
-			w.WriteHeader(http.StatusInternalServerError)
-			return
-		}
-
-		err = confirmOrder(order, orderHandler)
-		if err != nil {
-			log.Printf("Error confirming order: %v\n", err)
-			w.WriteHeader(http.StatusInternalServerError)
-			return
-		}
-
-		err = triggerOrderCompleted(err, syncedServer, order)
-		if err != nil {
-			log.Printf("Error processing cart message: %v\n", err)
-			w.WriteHeader(http.StatusInternalServerError)
-			return
-		}
-		err = KlarnaInstance.AcknowledgeOrder(orderId)
-		if err != nil {
-			log.Printf("Error acknowledging order: %v\n", err)
-		}
-
-		w.WriteHeader(http.StatusOK)
-	})
-	mux.HandleFunc("/version", func(w http.ResponseWriter, r *http.Request) {
-		w.WriteHeader(http.StatusOK)
-		w.Write([]byte("1.0.0"))
-	})
-
-	sigs := make(chan os.Signal, 1)
-	done := make(chan bool, 1)
-	signal.Notify(sigs, syscall.SIGTERM)
-
-	go func() {
-		sig := <-sigs
-		fmt.Println("Shutting down due to signal:", sig)
-		go syncedPool.Close()
-		app.Save()
-		done <- true
-	}()
-
-	log.Print("Server started at port 8080")
-	go http.ListenAndServe(":8080", mux)
-	<-done
-
-}
-
-func triggerOrderCompleted(err error, syncedServer *PoolServer, order *CheckoutOrder) error {
-	_, err = syncedServer.pool.Process(ToCartId(order.MerchantReference1), Message{
-		Type: OrderCompletedType,
-		Content: &messages.OrderCreated{
-			OrderId: order.ID,
-			Status:  order.Status,
-		},
-	})
-	return err
-}
-
-func confirmOrder(order *CheckoutOrder, orderHandler *AmqpOrderHandler) error {
-	orderToSend, err := json.Marshal(order)
-	if err != nil {
-		return err
-	}
-	err = orderHandler.Connect()
-	if err != nil {
-		return err
-	}
-	defer orderHandler.Close()
-	err = orderHandler.OrderCompleted(orderToSend)
-	if err != nil {
-		return err
-	}
-
-	return nil
-}

message-handler.go

@@ -1,315 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"io"
-
-	messages "git.tornberg.me/go-cart-actor/proto"
-	"google.golang.org/protobuf/proto"
-)
-
-var Handlers = map[uint16]MessageHandler{
-	AddRequestType:          &AddRequestHandler{},
-	AddItemType:             &AddItemHandler{},
-	ChangeQuantityType:      &ChangeQuantityHandler{},
-	SetDeliveryType:         &SetDeliveryHandler{},
-	RemoveItemType:          &RemoveItemHandler{},
-	RemoveDeliveryType:      &RemoveDeliveryHandler{},
-	CreateCheckoutOrderType: &CheckoutHandler{},
-	SetCartItemsType:        &SetCartItemsHandler{},
-	OrderCompletedType:      &OrderCompletedHandler{},
-}
-
-func GetMessageHandler(t uint16) (MessageHandler, error) {
-	h, ok := Handlers[t]
-	if !ok {
-		return nil, fmt.Errorf("no handler for message type %d", t)
-	}
-	return h, nil
-}
-
-type MessageHandler interface {
-	Write(*Message, io.Writer) error
-	Read(data []byte) (interface{}, error)
-	Is(*Message) bool
-}
-type TypedMessageHandler struct {
-	Type uint16
-}
-
-type SetCartItemsHandler struct {
-	TypedMessageHandler
-}
-
-func (h *SetCartItemsHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.SetCartRequest))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *SetCartItemsHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.SetCartRequest{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *SetCartItemsHandler) Is(m *Message) bool {
-	if m.Type != AddRequestType {
-		return false
-	}
-	_, ok := m.Content.(*messages.SetCartRequest)
-	return ok
-}
-
-type AddRequestHandler struct {
-	TypedMessageHandler
-}
-
-func (h *AddRequestHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.AddRequest))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *AddRequestHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.AddRequest{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *AddRequestHandler) Is(m *Message) bool {
-	if m.Type != AddRequestType {
-		return false
-	}
-	_, ok := m.Content.(*messages.AddRequest)
-	return ok
-}
-
-type AddItemHandler struct {
-	TypedMessageHandler
-}
-
-func (h *AddItemHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.AddItem))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *AddItemHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.AddItem{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *AddItemHandler) Is(m *Message) bool {
-	if m.Type != AddItemType {
-		return false
-	}
-	_, ok := m.Content.(*messages.AddItem)
-	return ok
-}
-
-type ChangeQuantityHandler struct {
-	TypedMessageHandler
-}
-
-func (h *ChangeQuantityHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.ChangeQuantity))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *ChangeQuantityHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.ChangeQuantity{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *ChangeQuantityHandler) Is(m *Message) bool {
-	if m.Type != ChangeQuantityType {
-		return false
-	}
-	_, ok := m.Content.(*messages.ChangeQuantity)
-	return ok
-}
-
-type SetDeliveryHandler struct {
-	TypedMessageHandler
-}
-
-func (h *SetDeliveryHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.SetDelivery))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *SetDeliveryHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.SetDelivery{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *SetDeliveryHandler) Is(m *Message) bool {
-	if m.Type != ChangeQuantityType {
-		return false
-	}
-	_, ok := m.Content.(*messages.SetDelivery)
-	return ok
-}
-
-type RemoveItemHandler struct {
-	TypedMessageHandler
-}
-
-func (h *RemoveItemHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.RemoveItem))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *RemoveItemHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.RemoveItem{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *RemoveItemHandler) Is(m *Message) bool {
-	if m.Type != AddItemType {
-		return false
-	}
-	_, ok := m.Content.(*messages.RemoveItem)
-	return ok
-}
-
-type RemoveDeliveryHandler struct {
-	TypedMessageHandler
-}
-
-func (h *RemoveDeliveryHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.RemoveDelivery))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *RemoveDeliveryHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.RemoveDelivery{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *RemoveDeliveryHandler) Is(m *Message) bool {
-	if m.Type != AddItemType {
-		return false
-	}
-	_, ok := m.Content.(*messages.RemoveDelivery)
-	return ok
-}
-
-type CheckoutHandler struct {
-	TypedMessageHandler
-}
-
-func (h *CheckoutHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.CreateCheckoutOrder))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-
-func (h *CheckoutHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.CreateCheckoutOrder{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-
-func (h *CheckoutHandler) Is(m *Message) bool {
-	if m.Type != CreateCheckoutOrderType {
-		return false
-	}
-	_, ok := m.Content.(*messages.CreateCheckoutOrder)
-	return ok
-}
-
-type OrderCompletedHandler struct {
-	TypedMessageHandler
-}
-
-func (h *OrderCompletedHandler) Write(m *Message, w io.Writer) error {
-	messageBytes, err := proto.Marshal(m.Content.(*messages.OrderCreated))
-	if err != nil {
-		return err
-	}
-	w.Write(messageBytes)
-	return nil
-}
-func (h *OrderCompletedHandler) Read(data []byte) (interface{}, error) {
-	msg := &messages.OrderCreated{}
-
-	err := proto.Unmarshal(data, msg)
-	if err != nil {
-		return nil, err
-	}
-	return msg, nil
-}
-func (h *OrderCompletedHandler) Is(m *Message) bool {
-	if m.Type != OrderCompletedType {
-		return false
-	}
-	_, ok := m.Content.(*messages.OrderCreated)
-	return ok
-}

message-types.go

@@ -1,15 +0,0 @@
-package main
-
-const (
-	AddRequestType = 1
-	AddItemType    = 2
-
-	RemoveItemType          = 4
-	RemoveDeliveryType      = 5
-	ChangeQuantityType      = 6
-	SetDeliveryType         = 7
-	SetPickupPointType      = 8
-	CreateCheckoutOrderType = 9
-	SetCartItemsType        = 10
-	OrderCompletedType      = 11
-)

message.go

@@ -1,94 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"encoding/binary"
-	"io"
-	"time"
-)
-
-type StorableMessage interface {
-	Write(w io.Writer) error
-}
-
-type Message struct {
-	Type      uint16
-	TimeStamp *int64
-	Content   interface{}
-}
-
-type MessageWriter struct {
-	io.Writer
-}
-
-type StorableMessageHeader struct {
-	Version    uint16
-	Type       uint16
-	TimeStamp  int64
-	DataLength uint64
-}
-
-func GetData(fn func(w io.Writer) error) ([]byte, error) {
-	var buf bytes.Buffer
-	err := fn(&buf)
-	if err != nil {
-		return nil, err
-	}
-	b := buf.Bytes()
-	return b, nil
-}
-
-func (m Message) Write(w io.Writer) error {
-	h, err := GetMessageHandler(m.Type)
-	if err != nil {
-		return err
-	}
-	data, err := GetData(func(w io.Writer) error {
-		return h.Write(&m, w)
-	})
-	if err != nil {
-		return err
-	}
-	ts := time.Now().Unix()
-	if m.TimeStamp != nil {
-		ts = *m.TimeStamp
-	}
-
-	err = binary.Write(w, binary.LittleEndian, StorableMessageHeader{
-		Version:    1,
-		Type:       m.Type,
-		TimeStamp:  ts,
-		DataLength: uint64(len(data)),
-	})
-	w.Write(data)
-
-	return err
-}
-
-func ReadMessage(reader io.Reader, m *Message) error {
-
-	header := StorableMessageHeader{}
-	err := binary.Read(reader, binary.LittleEndian, &header)
-	if err != nil {
-		return err
-	}
-	messageBytes := make([]byte, header.DataLength)
-	_, err = reader.Read(messageBytes)
-	if err != nil {
-		return err
-	}
-	h, err := GetMessageHandler(header.Type)
-	if err != nil {
-		return err
-	}
-	content, err := h.Read(messageBytes)
-	if err != nil {
-		return err
-	}
-	m.Content = content
-
-	m.Type = header.Type
-	m.TimeStamp = &header.TimeStamp
-
-	return nil
-}