wip

Co-authored-by: matst80 <mats.tornberg@gmail.com>
Reviewed-on: #8
Co-authored-by: Mats Törnberg <mats@tornberg.me>
Co-committed-by: Mats Törnberg <mats@tornberg.me>

.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 🚀
-on: [push]
+run-name: ${{ gitea.actor }} build 🚀
+on:
+  push:
+    branches:
+      - main
 
 jobs:
   BuildAndDeployAmd64:
     runs-on: amd64
     steps:
-      - name: Check out repository code
-        uses: actions/checkout@v4
-      - name: Build docker image
-        run: docker build --progress=plain -t registry.knatofs.se/go-cart-actor-amd64:latest .
-      - name: Push to registry
-        run: docker push registry.knatofs.se/go-cart-actor-amd64:latest
-      - name: Deploy to Kubernetes
+      - uses: actions/checkout@v5
+      - name: Build amd64 image
+        run: |
+          docker build \
+            --progress=plain \
+            -t registry.k6n.net/go-cart-actor-amd64:latest \
+            .
+      - 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
-        run: kubectl rollout restart deployment/cart-actor-x86 -n cart
+      - name: Rollout amd64 backoffice deployment
+        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
-      - name: Build docker image
-        run: docker build --progress=plain -t registry.knatofs.se/go-cart-actor .
-      - name: Push to registry
-        run: docker push registry.knatofs.se/go-cart-actor
-      - name: Rollout arm64 deployment
-        run: kubectl rollout restart deployment/cart-actor-arm64 -n cart
+      - uses: actions/checkout@v4
+      - name: Build arm64 image
+        run: |
+          docker build \
+            --progress=plain \
+            -t registry.k6n.net/go-cart-actor:latest \
+            .
+      - 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 +1,96 @@
-# 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
+############################
+FROM golang:1.25-alpine AS build
+WORKDIR /src
+
+RUN apk add --no-cache git
+
+# Build metadata (can be overridden at build time)
+ARG VERSION=dev
+ARG GIT_COMMIT=unknown
+ARG BUILD_DATE=unknown
+
+# 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}
+
+# Dependency caching
 COPY go.mod go.sum ./
 RUN go mod download
 
-COPY proto ./proto
-COPY *.go ./
+# Copy full source (relay on .dockerignore to prune)
+COPY . .
 
-RUN CGO_ENABLED=0 GOOS=linux go build -o /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
 
-FROM gcr.io/distroless/base-debian11
+# 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
+
+############################
+# 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
+
+# Document (not expose forcibly) typical ports: 8080 (HTTP), 1337 (gRPC)
+EXPOSE 8080 1337
+
+USER nonroot:nonroot
 ENTRYPOINT ["/go-cart-actor"]

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/go-cart-actor/proto;messages
+# ------------------------------------------------------------------------------
+
+MODULE_PATH := git.k6n.net/go-cart-actor
+PROTO_DIR   := proto
+PROTOS      := $(PROTO_DIR)/cart.proto $(PROTO_DIR)/control_plane.proto $(PROTO_DIR)/checkout.proto
+CART_PROTO_DIR := $(PROTO_DIR)/cart
+CONTROL_PROTO_DIR := $(PROTO_DIR)/control
+CHECKOUT_PROTO_DIR := $(PROTO_DIR)/checkout
+
+# 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 \
+	  $(PROTO_DIR)/checkout.proto
+	@echo "$(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)"
+
+
+
+
+
+
+
+
+
+
+
+
+
+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

@@ -6,7 +6,7 @@ A distributed cart management system using the actor model pattern.
 
 - Go 1.24.2+
 - Protocol Buffers compiler (`protoc`)
-- protoc-gen-go plugin
+- protoc-gen-go and protoc-gen-go-grpc plugins
 
 ### Installing Protocol Buffers
 
@@ -32,17 +32,20 @@ sudo apt install protobuf-compiler
 
 ```bash
 go install google.golang.org/protobuf/cmd/protoc-gen-go@latest
+go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@latest
 ```
 
 ## Working with Protocol Buffers
 
 ### Generating Go code from proto files
 
-After modifying `proto/messages.proto`, regenerate the Go code:
+After modifying any proto (`proto/messages.proto`, `proto/cart_actor.proto`, `proto/control_plane.proto`), regenerate the Go code (all three share the unified `messages` package):
 
 ```bash
 cd proto
-protoc --go_out=. --go_opt=paths=source_relative messages.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
 ```
 
 ### Protocol Buffer Messages
@@ -73,8 +76,338 @@ go build .
 go test ./...
 ```
 
+## HTTP API Quick Start (curl Examples)
+
+Assuming the service is reachable at http://localhost:8080 and the cart API is mounted at /cart.
+Most endpoints use an HTTP cookie named `cartid` to track the cart. The first request will set it.
+
+### 1. Get (or create) a cart
+```bash
+curl -i http://localhost:8080/cart/
+```
+Response sets a `cartid` cookie and returns the current (possibly empty) cart JSON.
+
+### 2. Add an item by SKU (implicit quantity = 1)
+```bash
+curl -i --cookie-jar cookies.txt http://localhost:8080/cart/add/TEST-SKU-123
+```
+Stores cookie in `cookies.txt` for subsequent calls.
+
+### 3. Add an item with explicit payload (country, quantity)
+```bash
+curl -i --cookie cookies.txt \
+  -H "Content-Type: application/json" \
+  -d '{"sku":"TEST-SKU-456","quantity":2,"country":"se"}' \
+  http://localhost:8080/cart/
+```
+
+### 4. Change quantity of an existing line
+(First list the cart to find `id` of the line; here we use id=1 as an example)
+```bash
+curl -i --cookie cookies.txt \
+  -X PUT -H "Content-Type: application/json" \
+  -d '{"id":1,"quantity":3}' \
+  http://localhost:8080/cart/
+```
+
+### 5. Remove an item
+```bash
+curl -i --cookie cookies.txt -X DELETE http://localhost:8080/cart/1
+```
+
+### 6. Set entire cart contents (overwrites items)
+```bash
+curl -i --cookie cookies.txt \
+  -X POST -H "Content-Type: application/json" \
+  -d '{"items":[{"sku":"TEST-SKU-AAA","quantity":1,"country":"se"},{"sku":"TEST-SKU-BBB","quantity":2,"country":"se"}]}' \
+  http://localhost:8080/cart/set
+```
+
+### 7. Add a delivery (provider + optional items)
+If `items` is empty or omitted, all items without a delivery get this one.
+```bash
+curl -i --cookie cookies.txt \
+  -X POST -H "Content-Type: application/json" \
+  -d '{"provider":"standard","items":[1,2]}' \
+  http://localhost:8080/cart/delivery
+```
+
+### 8. Remove a delivery by deliveryId
+```bash
+curl -i --cookie cookies.txt -X DELETE http://localhost:8080/cart/delivery/1
+```
+
+### 9. Set a pickup point for a delivery
+```bash
+curl -i --cookie cookies.txt \
+  -X PUT -H "Content-Type: application/json" \
+  -d '{"id":"PUP123","name":"Locker 5","address":"Main St 1","city":"Stockholm","zip":"11122","country":"SE"}' \
+  http://localhost:8080/cart/delivery/1/pickupPoint
+```
+
+### 10. Checkout (returns HTML snippet from Klarna)
+```bash
+curl -i --cookie cookies.txt http://localhost:8080/cart/checkout
+```
+
+### 11. Using a known cart id directly (bypassing cookie)
+If you already have a cart id (e.g. 1720000000000000):
+```bash
+CART_ID=1720000000000000
+curl -i http://localhost:8080/cart/byid/$CART_ID
+curl -i -X POST -H "Content-Type: application/json" \
+  -d '{"sku":"TEST-SKU-XYZ","quantity":1,"country":"se"}' \
+  http://localhost:8080/cart/byid/$CART_ID
+```
+
+### 12. Clear cart cookie (forces a new cart on next request)
+```bash
+curl -i --cookie cookies.txt -X DELETE http://localhost:8080/cart/
+```
+
+Tip: Use `--cookie-jar` and `--cookie` to persist the session across multiple commands:
+```bash
+curl --cookie-jar cookies.txt http://localhost:8080/cart/
+curl --cookie cookies.txt http://localhost:8080/cart/add/TEST-SKU-123
+```
+
 ## Important Notes
 
-- Always regenerate protobuf Go code after modifying `.proto` files
+- 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

cart-grain.go

@@ -1,608 +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
-
-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 interface{}) (int, error) {
-	switch v := data.(type) {
-	case float64:
-		return int(v), nil
-	case int:
-		return v, nil
-	default:
-		return 0, fmt.Errorf("invalid type")
-	}
-}
-
-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.Fields[5])
-
-	price, priceErr := getInt(item.Fields[4])
-
-	if priceErr != nil {
-		return nil, fmt.Errorf("invalid price")
-	}
-
-	stock := InStock
-	if item.StockLevel == "0" || item.StockLevel == "" {
-		stock = OutOfStock
-	} else if item.StockLevel == "5+" {
-		stock = LowStock
-	}
-	articleType, _ := item.Fields[1].(string)
-	outletGrade, ok := item.Fields[20].(string)
-	var outlet *string
-	if ok {
-		outlet = &outletGrade
-	}
-	sellerId, _ := item.Fields[24].(string)
-	sellerName, _ := item.Fields[9].(string)
-
-	brand, _ := item.Fields[2].(string)
-	category, _ := item.Fields[10].(string)
-	category2, _ := item.Fields[11].(string)
-	category3, _ := item.Fields[12].(string)
-	category4, _ := item.Fields[13].(string)
-	category5, _ := item.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)
-	}
-
-}

cart-grain_test.go

@@ -1,248 +0,0 @@
-package main
-
-import (
-	"testing"
-	"time"
-
-	messages "git.tornberg.me/go-cart-actor/proto"
-)
-
-func GetMessage(t uint16, data interface{}) *Message {
-	ts := time.Now().Unix()
-	return &Message{
-		TimeStamp: &ts,
-		Type:      t,
-		Content:   data,
-	}
-}
-
-func TestTaxAmount(t *testing.T) {
-	taxAmount := GetTaxAmount(12500, 2500)
-	if taxAmount != 2500 {
-		t.Errorf("Expected 2500, got %d\n", taxAmount)
-	}
-}
-
-func TestAddToCartShortCut(t *testing.T) {
-	grain, err := spawn(ToCartId("kalle"))
-	if err != nil {
-		t.Errorf("Error spawning: %v\n", err)
-	}
-	if len(grain.Items) != 0 {
-		t.Errorf("Expected 0 items, got %d\n", len(grain.Items))
-	}
-	msg := GetMessage(AddItemType, &messages.AddItem{
-		Quantity: 2,
-		Price:    100,
-		Sku:      "123",
-		Name:     "Test item",
-		Image:    "test.jpg",
-	})
-
-	_, err = grain.HandleMessage(msg, false)
-	if err != nil {
-		t.Errorf("Error handling message: %v\n", err)
-	}
-	if len(grain.Items) != 1 {
-		t.Errorf("Expected 1 item, got %d\n", len(grain.Items))
-	}
-	if grain.Items[0].Quantity != 2 {
-		t.Errorf("Expected quantity 2, got %d\n", grain.Items[0].Quantity)
-	}
-	if len(grain.storageMessages) != 1 {
-		t.Errorf("Expected 1 storage message, got %d\n", len(grain.storageMessages))
-	}
-	shortCutMessage := GetMessage(AddRequestType, &messages.AddRequest{
-		Quantity: 2,
-		Sku:      "123",
-	})
-	_, err = grain.HandleMessage(shortCutMessage, false)
-	if err != nil {
-		t.Errorf("Error handling message: %v\n", err)
-	}
-	if len(grain.Items) != 1 {
-		t.Errorf("Expected 1 item, got %d\n", len(grain.Items))
-	}
-	if len(grain.storageMessages) != 2 {
-		t.Errorf("Expected 2 storage message, got %d\n", len(grain.storageMessages))
-	}
-	if grain.storageMessages[0].Type != AddItemType {
-		t.Errorf("Expected AddItemType, got %d\n", grain.storageMessages[0].Type)
-	}
-	if grain.storageMessages[1].Type != AddRequestType {
-		t.Errorf("Expected AddRequestType, got %d\n", grain.storageMessages[1].Type)
-	}
-}
-
-func TestAddRequestToGrain(t *testing.T) {
-	grain, err := spawn(ToCartId("kalle"))
-	if err != nil {
-		t.Errorf("Error spawning: %v\n", err)
-	}
-	msg := GetMessage(AddRequestType, &messages.AddRequest{
-		Quantity: 2,
-		Sku:      "763281",
-	})
-	result, err := grain.HandleMessage(msg, false)
-	if err != nil {
-		t.Errorf("Error handling message: %v\n", err)
-	}
-	if result.StatusCode != 200 {
-		t.Errorf("Call failed\n")
-	}
-	t.Log(result)
-}
-
-func TestAddToCart(t *testing.T) {
-	grain, err := spawn(ToCartId("kalle"))
-	if err != nil {
-		t.Errorf("Error spawning: %v\n", err)
-	}
-	if len(grain.Items) != 0 {
-		t.Errorf("Expected 0 items, got %d\n", len(grain.Items))
-	}
-	msg := GetMessage(AddItemType, &messages.AddItem{
-		Quantity: 2,
-		Price:    100,
-		Sku:      "123",
-		Name:     "Test item",
-		Image:    "test.jpg",
-	})
-
-	result, err := grain.HandleMessage(msg, false)
-
-	if err != nil {
-		t.Errorf("Error handling message: %v\n", err)
-	}
-	if result.StatusCode != 200 {
-		t.Errorf("Call failed\n")
-	}
-	if grain.TotalPrice != 200 {
-		t.Errorf("Expected total price 200, got %d\n", grain.TotalPrice)
-	}
-	if len(grain.Items) != 1 {
-		t.Errorf("Expected 1 item, got %d\n", len(grain.Items))
-	}
-	if grain.Items[0].Quantity != 2 {
-		t.Errorf("Expected quantity 2, got %d\n", grain.Items[0].Quantity)
-	}
-	result, err = grain.HandleMessage(msg, false)
-	if err != nil {
-		t.Errorf("Error handling message: %v\n", err)
-	}
-	if result.StatusCode != 200 {
-		t.Errorf("Call failed\n")
-	}
-	if grain.Items[0].Quantity != 4 {
-		t.Errorf("Expected quantity 4, got %d\n", grain.Items[0].Quantity)
-	}
-	if grain.TotalPrice != 400 {
-		t.Errorf("Expected total price 400, got %d\n", grain.TotalPrice)
-	}
-}
-
-func TestSetDelivery(t *testing.T) {
-	grain, err := spawn(ToCartId("kalle"))
-	if err != nil {
-		t.Errorf("Error spawning: %v\n", err)
-	}
-	if len(grain.Items) != 0 {
-		t.Errorf("Expected 0 items, got %d\n", len(grain.Items))
-	}
-	msg := GetMessage(AddItemType, &messages.AddItem{
-		Quantity: 2,
-		Price:    100,
-		Sku:      "123",
-		Name:     "Test item",
-		Image:    "test.jpg",
-	})
-
-	grain.HandleMessage(msg, false)
-
-	msg = GetMessage(AddItemType, &messages.AddItem{
-		Quantity: 2,
-		Price:    100,
-		Sku:      "123",
-		Name:     "Test item",
-		Image:    "test.jpg",
-	})
-
-	result, err := grain.HandleMessage(msg, false)
-
-	if err != nil {
-		t.Errorf("Error handling message: %v\n", err)
-	}
-	if result.StatusCode != 200 {
-		t.Errorf("Call failed\n")
-	}
-
-	setDelivery := GetMessage(SetDeliveryType, &messages.SetDelivery{
-		Provider: "test",
-		Items:    []int64{1},
-	})
-
-	_, err = grain.HandleMessage(setDelivery, false)
-	if err != nil {
-		t.Errorf("Error handling message: %v\n", err)
-	}
-	if len(grain.Deliveries) != 1 {
-		t.Errorf("Expected 1 delivery, got %d\n", len(grain.Deliveries))
-	}
-	if len(grain.Deliveries[0].Items) != 1 {
-		t.Errorf("Expected 1 items in delivery, got %d\n", len(grain.Deliveries[0].Items))
-	}
-}
-
-func TestSetDeliveryOnAll(t *testing.T) {
-	grain, err := spawn(ToCartId("kalle"))
-	if err != nil {
-		t.Errorf("Error spawning: %v\n", err)
-	}
-	if len(grain.Items) != 0 {
-		t.Errorf("Expected 0 items, got %d\n", len(grain.Items))
-	}
-	msg := GetMessage(AddItemType, &messages.AddItem{
-		Quantity: 2,
-		Price:    100,
-		Sku:      "123",
-		Name:     "Test item",
-		Image:    "test.jpg",
-	})
-
-	grain.HandleMessage(msg, false)
-
-	msg = GetMessage(AddItemType, &messages.AddItem{
-		Quantity: 2,
-		Price:    100,
-		Sku:      "1233",
-		Name:     "Test item2",
-		Image:    "test.jpg",
-	})
-
-	result, err := grain.HandleMessage(msg, false)
-
-	if err != nil {
-		t.Errorf("Error handling message: %v\n", err)
-	}
-	if result.StatusCode != 200 {
-		t.Errorf("Call failed\n")
-	}
-
-	setDelivery := GetMessage(SetDeliveryType, &messages.SetDelivery{
-		Provider: "test",
-		Items:    []int64{},
-	})
-
-	_, err = grain.HandleMessage(setDelivery, false)
-	if err != nil {
-		t.Errorf("Error handling message: %v\n", err)
-	}
-	if len(grain.Deliveries) != 1 {
-		t.Errorf("Expected 1 delivery, got %d\n", len(grain.Deliveries))
-	}
-
-	if len(grain.Deliveries[0].Items) != 2 {
-		t.Errorf("Expected 2 items in delivery, got %d\n", len(grain.Deliveries[0].Items))
-	}
-
-}

cmd/backoffice/fileserver.go

@@ -0,0 +1,439 @@
+package main
+
+import (
+	"bufio"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/actor"
+	"git.k6n.net/go-cart-actor/pkg/cart"
+	"git.k6n.net/go-cart-actor/pkg/checkout"
+	"google.golang.org/protobuf/proto"
+)
+
+type FileServer struct {
+	// Define fields here
+	dataDir         string
+	checkoutDataDir string
+	storage         actor.LogStorage[cart.CartGrain]
+	checkoutStorage actor.LogStorage[checkout.CheckoutGrain]
+}
+
+func NewFileServer(dataDir string, checkoutDataDir string, storage actor.LogStorage[cart.CartGrain], checkoutStorage actor.LogStorage[checkout.CheckoutGrain]) *FileServer {
+	return &FileServer{
+		dataDir:         dataDir,
+		checkoutDataDir: checkoutDataDir,
+		storage:         storage,
+		checkoutStorage: checkoutStorage,
+	}
+}
+
+func isValidId(id string) (uint64, bool) {
+	if nr, err := strconv.ParseUint(id, 10, 64); err == nil {
+		return nr, true
+	}
+	if nr, ok := cart.ParseCartId(id); ok {
+		return uint64(nr), true
+	}
+	return 0, false
+}
+
+func isValidFileId(name string) (uint64, bool) {
+
+	parts := strings.Split(name, ".")
+	if len(parts) > 1 && parts[1] == "events" {
+		idStr := parts[0]
+
+		return isValidId(idStr)
+	}
+	return 0, false
+}
+
+// func AccessTime(info os.FileInfo) (time.Time, bool) {
+// 	switch stat := info.Sys().(type) {
+// 	case *syscall.Stat_t:
+// 		// Linux: Atim; macOS/BSD: Atimespec
+// 		// Use reflection or build tags if naming differs.
+// 		// Linux:
+// 		if stat.Atim.Sec != 0 || stat.Atim.Nsec != 0 {
+// 			return time.Unix(int64(stat.Atim.Sec), int64(stat.Atim.Nsec)), true
+// 		}
+// 		// macOS/BSD example (uncomment if needed):
+// 		//return time.Unix(int64(stat.Atimespec.Sec), int64(stat.Atimespec.Nsec)), true
+// 	}
+// 	return time.Time{}, false
+// }
+
+func appendFileInfo(info fs.FileInfo, out *CartFileInfo) *CartFileInfo {
+	//sys := info.Sys()
+	//fmt.Printf("sys type %T", sys)
+	out.Size = info.Size()
+	out.Modified = info.ModTime()
+	//out.Accessed, _ = AccessTime(info)
+	return out
+}
+
+func appendCheckoutFileInfo(info fs.FileInfo, out *CheckoutFileInfo) *CheckoutFileInfo {
+	out.Size = info.Size()
+	out.Modified = info.ModTime()
+	return out
+}
+
+// var cartFileRe = regexp.MustCompile(`^(\d+)\.events\.log$`)
+
+func listCartFiles(dir string) ([]*CartFileInfo, error) {
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return []*CartFileInfo{}, nil
+		}
+		return nil, err
+	}
+	out := make([]*CartFileInfo, 0)
+	for _, e := range entries {
+		if e.IsDir() {
+			continue
+		}
+		id, valid := isValidFileId(e.Name())
+		if !valid {
+			continue
+		}
+
+		info, err := e.Info()
+		if err != nil {
+			continue
+		}
+		info.Sys()
+		out = append(out, appendFileInfo(info, &CartFileInfo{
+			ID:     fmt.Sprintf("%d", id),
+			CartId: cart.CartId(id),
+		}))
+	}
+	return out, nil
+}
+
+func listCheckoutFiles(dir string) ([]*CheckoutFileInfo, error) {
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return []*CheckoutFileInfo{}, nil
+		}
+		return nil, err
+	}
+	out := make([]*CheckoutFileInfo, 0)
+	for _, e := range entries {
+		if e.IsDir() {
+			continue
+		}
+		id, valid := isValidFileId(e.Name())
+		if !valid {
+			continue
+		}
+
+		info, err := e.Info()
+		if err != nil {
+			continue
+		}
+		out = append(out, appendCheckoutFileInfo(info, &CheckoutFileInfo{
+			ID:         fmt.Sprintf("%d", id),
+			CheckoutId: checkout.CheckoutId(id),
+		}))
+	}
+	return out, nil
+}
+
+func readRawLogLines(path string) ([]json.RawMessage, error) {
+	fh, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer fh.Close()
+	lines := make([]json.RawMessage, 0, 64)
+	s := bufio.NewScanner(fh)
+	// increase buffer to handle larger JSON lines
+	buf := make([]byte, 0, 1024*1024)
+	s.Buffer(buf, 1024*1024)
+	for s.Scan() {
+		line := s.Bytes()
+		if line == nil {
+			continue
+		}
+		lines = append(lines, line)
+	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
+	return lines, nil
+}
+
+func writeJSON(w http.ResponseWriter, status int, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set("Cache-Control", "no-cache")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(v)
+}
+
+func (fs *FileServer) CartsHandler(w http.ResponseWriter, r *http.Request) {
+	list, err := listCartFiles(fs.dataDir)
+	if err != nil {
+		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		return
+	}
+	// sort by modified desc
+	sort.Slice(list, func(i, j int) bool { return list[i].Modified.After(list[j].Modified) })
+
+	writeJSON(w, http.StatusOK, map[string]any{
+		"count": len(list),
+		"carts": list,
+	})
+}
+
+func (fs *FileServer) CheckoutsHandler(w http.ResponseWriter, r *http.Request) {
+	list, err := listCheckoutFiles(fs.checkoutDataDir)
+	if err != nil {
+		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		return
+	}
+	// sort by modified desc
+	sort.Slice(list, func(i, j int) bool { return list[i].Modified.After(list[j].Modified) })
+
+	writeJSON(w, http.StatusOK, map[string]any{
+		"count":     len(list),
+		"checkouts": list,
+	})
+}
+
+func (fs *FileServer) PromotionsHandler(w http.ResponseWriter, r *http.Request) {
+	fileName := filepath.Join(fs.dataDir, "promotions.json")
+	if r.Method == http.MethodGet {
+		file, err := os.Open(fileName)
+		if err != nil {
+			writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+			return
+		}
+		defer file.Close()
+
+		io.Copy(w, file)
+		return
+	}
+	if r.Method == http.MethodPost {
+		file, err := os.Create(fileName)
+		if err != nil {
+			writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+			return
+		}
+		defer file.Close()
+
+		io.Copy(file, r.Body)
+		return
+	}
+
+	w.WriteHeader(http.StatusMethodNotAllowed)
+}
+
+func (fs *FileServer) VoucherHandler(w http.ResponseWriter, r *http.Request) {
+	fileName := filepath.Join(fs.dataDir, "vouchers.json")
+	if r.Method == http.MethodGet {
+		file, err := os.Open(fileName)
+		if err != nil {
+			writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+			return
+		}
+		defer file.Close()
+
+		io.Copy(w, file)
+		return
+	}
+	if r.Method == http.MethodPost {
+		file, err := os.Create(fileName)
+		if err != nil {
+			writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+			return
+		}
+		defer file.Close()
+
+		io.Copy(file, r.Body)
+		return
+	}
+
+	w.WriteHeader(http.StatusMethodNotAllowed)
+}
+
+func (fs *FileServer) PromotionPartHandler(w http.ResponseWriter, r *http.Request) {
+	idStr := r.PathValue("id")
+	if idStr == "" {
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprintf(w, "missing id")
+		return
+	}
+	_, ok := isValidId(idStr)
+	if !ok {
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprintf(w, "invalid id %s", idStr)
+		return
+	}
+	w.WriteHeader(http.StatusNotImplemented)
+}
+
+type JsonError struct {
+	Error string `json:"error"`
+}
+
+func acceptAll(_ proto.Message, _ int, _ time.Time) bool {
+	return true
+}
+
+func acceptUntilIndex(maxIndex int) func(msg proto.Message, index int, when time.Time) bool {
+	return func(msg proto.Message, index int, when time.Time) bool {
+		return index < maxIndex
+	}
+}
+
+func acceptUntilTimestamp(until time.Time) func(msg proto.Message, index int, when time.Time) bool {
+	return func(msg proto.Message, index int, when time.Time) bool {
+		return when.Before(until)
+	}
+}
+
+func (fs *FileServer) CartHandler(w http.ResponseWriter, r *http.Request) {
+	idStr := r.PathValue("id")
+	if idStr == "" {
+		writeJSON(w, http.StatusBadRequest, JsonError{Error: "missing id"})
+		return
+	}
+	id, ok := isValidId(idStr)
+	if !ok {
+		writeJSON(w, http.StatusBadRequest, JsonError{Error: "invalid id"})
+		return
+	}
+	// parse query parameters for filtering
+	query := r.URL.Query()
+	filterFunction := acceptAll
+	if maxIndexStr := query.Get("maxIndex"); maxIndexStr != "" {
+		log.Printf("filter maxIndex: %s", maxIndexStr)
+		maxIndex, err := strconv.Atoi(maxIndexStr)
+		if err != nil {
+			writeJSON(w, http.StatusBadRequest, JsonError{Error: "invalid maxIndex"})
+			return
+		}
+		filterFunction = acceptUntilIndex(maxIndex)
+	} else if untilStr := query.Get("until"); untilStr != "" {
+		log.Printf("filter until: %s", untilStr)
+		until, err := time.Parse(time.RFC3339, untilStr)
+		if err != nil {
+			writeJSON(w, http.StatusBadRequest, JsonError{Error: "invalid until timestamp"})
+			return
+		}
+		filterFunction = acceptUntilTimestamp(until)
+	}
+	// reconstruct state from event log if present
+	grain := cart.NewCartGrain(id, time.Now())
+	err := fs.storage.LoadEventsFunc(r.Context(), id, grain, filterFunction)
+	if err != nil {
+		writeJSON(w, http.StatusInternalServerError, JsonError{Error: err.Error()})
+		return
+	}
+
+	path := filepath.Join(fs.dataDir, fmt.Sprintf("%d.events.log", id))
+	info, err := os.Stat(path)
+	if err != nil && errors.Is(err, os.ErrNotExist) {
+		writeJSON(w, http.StatusNotFound, JsonError{Error: "cart not found"})
+		return
+	} else if err != nil {
+		writeJSON(w, http.StatusInternalServerError, JsonError{Error: err.Error()})
+		return
+	}
+	lines, err := readRawLogLines(path)
+	if err != nil {
+		writeJSON(w, http.StatusInternalServerError, JsonError{Error: err.Error()})
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{
+		"id":        id,
+		"cartId":    cart.CartId(id).String(),
+		"state":     grain,
+		"mutations": lines,
+		"meta": map[string]any{
+			"size":     info.Size(),
+			"modified": info.ModTime(),
+			"path":     path,
+		},
+	})
+}
+
+func (fs *FileServer) CheckoutHandler(w http.ResponseWriter, r *http.Request) {
+	idStr := r.PathValue("id")
+	if idStr == "" {
+		writeJSON(w, http.StatusBadRequest, JsonError{Error: "missing id"})
+		return
+	}
+	id, ok := isValidId(idStr)
+	if !ok {
+		writeJSON(w, http.StatusBadRequest, JsonError{Error: "invalid id"})
+		return
+	}
+	// parse query parameters for filtering
+	query := r.URL.Query()
+	filterFunction := acceptAll
+	if maxIndexStr := query.Get("maxIndex"); maxIndexStr != "" {
+		log.Printf("filter maxIndex: %s", maxIndexStr)
+		maxIndex, err := strconv.Atoi(maxIndexStr)
+		if err != nil {
+			writeJSON(w, http.StatusBadRequest, JsonError{Error: "invalid maxIndex"})
+			return
+		}
+		filterFunction = acceptUntilIndex(maxIndex)
+	} else if untilStr := query.Get("until"); untilStr != "" {
+		log.Printf("filter until: %s", untilStr)
+		until, err := time.Parse(time.RFC3339, untilStr)
+		if err != nil {
+			writeJSON(w, http.StatusBadRequest, JsonError{Error: "invalid until timestamp"})
+			return
+		}
+		filterFunction = acceptUntilTimestamp(until)
+	}
+	// reconstruct state from event log if present
+	grain := checkout.NewCheckoutGrain(id, cart.CartId(id), 0, time.Now(), nil)
+	err := fs.checkoutStorage.LoadEventsFunc(r.Context(), id, grain, filterFunction)
+	if err != nil {
+		writeJSON(w, http.StatusInternalServerError, JsonError{Error: err.Error()})
+		return
+	}
+
+	path := filepath.Join(fs.checkoutDataDir, fmt.Sprintf("%d.events.log", id))
+	info, err := os.Stat(path)
+	if err != nil && errors.Is(err, os.ErrNotExist) {
+		writeJSON(w, http.StatusNotFound, JsonError{Error: "checkout not found"})
+		return
+	} else if err != nil {
+		writeJSON(w, http.StatusInternalServerError, JsonError{Error: err.Error()})
+		return
+	}
+	lines, err := readRawLogLines(path)
+	if err != nil {
+		writeJSON(w, http.StatusInternalServerError, JsonError{Error: err.Error()})
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{
+		"id":         id,
+		"checkoutId": checkout.CheckoutId(id).String(),
+		"state":      grain,
+		"mutations":  lines,
+		"meta": map[string]any{
+			"size":     info.Size(),
+			"modified": info.ModTime(),
+			"path":     path,
+		},
+	})
+}

cmd/backoffice/fileserver_test.go

@@ -0,0 +1,89 @@
+package main
+
+import (
+	"math/rand"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/cart"
+)
+
+// TestAppendFileInfoRandomProjectFile picks a random existing .go source file in the
+// repository (from a small curated list to keep the test hermetic) and verifies
+// that appendFileInfo populates Size, Modified and System without mutating the
+// identity fields (ID, CartId). The randomness is only to satisfy the requirement
+// of using "a random project file"; the test behavior is deterministic enough for
+// CI because all chosen files are expected to exist.
+func TestAppendFileInfoRandomProjectFile(t *testing.T) {
+	candidates := []string{
+		filepath.FromSlash("../../pkg/cart/cart_id.go"),
+		filepath.FromSlash("../../pkg/actor/grain.go"),
+		filepath.FromSlash("../../cmd/cart/main.go"),
+	}
+	// Pick one at random.
+	rand.Seed(time.Now().UnixNano())
+	path := candidates[rand.Intn(len(candidates))]
+
+	info, err := os.Stat(path)
+	if err != nil {
+		t.Fatalf("stat failed for %s: %v", path, err)
+	}
+
+	// Pre-populate a CartFileInfo with identity fields.
+	origID := "test-id"
+	origCartId := cart.CartId(12345)
+	cf := &CartFileInfo{ID: origID, CartId: origCartId}
+
+	// Call function under test.
+	got := appendFileInfo(info, cf)
+
+	if got != cf {
+		t.Fatalf("appendFileInfo should return the same pointer instance")
+	}
+
+	if cf.ID != origID {
+		t.Fatalf("ID mutated: expected %q got %q", origID, cf.ID)
+	}
+	if cf.CartId != origCartId {
+		t.Fatalf("CartId mutated: expected %v got %v", origCartId, cf.CartId)
+	}
+
+	if cf.Size != info.Size() {
+		t.Fatalf("Size mismatch: expected %d got %d", info.Size(), cf.Size)
+	}
+
+	mod := info.ModTime()
+	// Allow small clock skew / coarse timestamp truncation.
+	if cf.Modified.Before(mod.Add(-2*time.Second)) || cf.Modified.After(mod.Add(2*time.Second)) {
+		t.Fatalf("Modified not within expected range: want ~%v got %v", mod, cf.Modified)
+	}
+
+}
+
+// TestAppendFileInfoTempFile creates a temporary file to ensure Size and Modified
+// are updated for a freshly written file with known content length.
+func TestAppendFileInfoTempFile(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "temp.events.log")
+	content := []byte("hello world\nanother line\n")
+	if err := os.WriteFile(path, content, 0644); err != nil {
+		t.Fatalf("write temp file failed: %v", err)
+	}
+
+	info, err := os.Stat(path)
+	if err != nil {
+		t.Fatalf("stat temp file failed: %v", err)
+	}
+
+	cf := &CartFileInfo{ID: "temp", CartId: cart.CartId(0)}
+	appendFileInfo(info, cf)
+
+	if cf.Size != int64(len(content)) {
+		t.Fatalf("expected Size %d got %d", len(content), cf.Size)
+	}
+	if cf.Modified.IsZero() {
+		t.Fatalf("Modified should be set")
+	}
+}

cmd/backoffice/hub.go

@@ -0,0 +1,248 @@
+package main
+
+import (
+	"bufio"
+	"crypto/sha1"
+	"encoding/base64"
+	"encoding/binary"
+	"io"
+	"net"
+	"net/http"
+	"strings"
+	"time"
+)
+
+// Hub manages websocket clients and broadcasts messages to them.
+type Hub struct {
+	register   chan *Client
+	unregister chan *Client
+	broadcast  chan []byte
+	clients    map[*Client]bool
+}
+
+// Client represents a single websocket client connection.
+type Client struct {
+	hub  *Hub
+	conn net.Conn
+	send chan []byte
+}
+
+// NewHub constructs a new Hub instance.
+func NewHub() *Hub {
+	return &Hub{
+		register:   make(chan *Client),
+		unregister: make(chan *Client),
+		broadcast:  make(chan []byte, 1024),
+		clients:    make(map[*Client]bool),
+	}
+}
+
+// Run starts the hub event loop.
+func (h *Hub) Run() {
+	for {
+		select {
+		case c := <-h.register:
+			h.clients[c] = true
+		case c := <-h.unregister:
+			if _, ok := h.clients[c]; ok {
+				delete(h.clients, c)
+				close(c.send)
+				_ = c.conn.Close()
+			}
+		case msg := <-h.broadcast:
+			for c := range h.clients {
+				select {
+				case c.send <- msg:
+				default:
+					// Client is slow or dead; drop it.
+					delete(h.clients, c)
+					close(c.send)
+					_ = c.conn.Close()
+				}
+			}
+		}
+	}
+}
+
+// computeAccept computes the Sec-WebSocket-Accept header value.
+func computeAccept(key string) string {
+	const magic = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
+	h := sha1.New()
+	h.Write([]byte(key + magic))
+	return base64.StdEncoding.EncodeToString(h.Sum(nil))
+}
+
+// ServeWS upgrades the HTTP request to a WebSocket connection and registers a client.
+func (h *Hub) ServeWS(w http.ResponseWriter, r *http.Request) {
+	if !strings.Contains(strings.ToLower(r.Header.Get("Connection")), "upgrade") || strings.ToLower(r.Header.Get("Upgrade")) != "websocket" {
+		http.Error(w, "upgrade required", http.StatusBadRequest)
+		return
+	}
+	key := r.Header.Get("Sec-WebSocket-Key")
+	if key == "" {
+		http.Error(w, "missing Sec-WebSocket-Key", http.StatusBadRequest)
+		return
+	}
+	accept := computeAccept(key)
+
+	hj, ok := w.(http.Hijacker)
+	if !ok {
+		http.Error(w, "websocket not supported", http.StatusInternalServerError)
+		return
+	}
+	conn, buf, err := hj.Hijack()
+	if err != nil {
+		return
+	}
+
+	// Write the upgrade response
+	response := "HTTP/1.1 101 Switching Protocols\r\n" +
+		"Upgrade: websocket\r\n" +
+		"Connection: Upgrade\r\n" +
+		"Sec-WebSocket-Accept: " + accept + "\r\n" +
+		"\r\n"
+	if _, err := buf.WriteString(response); err != nil {
+		_ = conn.Close()
+		return
+	}
+	if err := buf.Flush(); err != nil {
+		_ = conn.Close()
+		return
+	}
+
+	client := &Client{
+		hub:  h,
+		conn: conn,
+		send: make(chan []byte, 256),
+	}
+	h.register <- client
+	go client.writePump()
+	go client.readPump()
+}
+
+// writeWSFrame writes a single WebSocket frame to the writer.
+func writeWSFrame(w io.Writer, opcode byte, payload []byte) error {
+	// FIN set, opcode as provided
+	header := []byte{0x80 | (opcode & 0x0F)}
+	l := len(payload)
+	switch {
+	case l < 126:
+		header = append(header, byte(l))
+	case l <= 65535:
+		ext := make([]byte, 2)
+		binary.BigEndian.PutUint16(ext, uint16(l))
+		header = append(header, 126)
+		header = append(header, ext...)
+	default:
+		ext := make([]byte, 8)
+		binary.BigEndian.PutUint64(ext, uint64(l))
+		header = append(header, 127)
+		header = append(header, ext...)
+	}
+	if _, err := w.Write(header); err != nil {
+		return err
+	}
+	if l > 0 {
+		if _, err := w.Write(payload); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// readPump handles control frames from the client and discards other incoming frames.
+// This server is broadcast-only to clients.
+func (c *Client) readPump() {
+	defer func() {
+		c.hub.unregister <- c
+	}()
+	reader := bufio.NewReader(c.conn)
+	for {
+		// Read first two bytes
+		b1, err := reader.ReadByte()
+		if err != nil {
+			return
+		}
+		b2, err := reader.ReadByte()
+		if err != nil {
+			return
+		}
+		opcode := b1 & 0x0F
+		masked := (b2 & 0x80) != 0
+		length := int64(b2 & 0x7F)
+		if length == 126 {
+			ext := make([]byte, 2)
+			if _, err := io.ReadFull(reader, ext); err != nil {
+				return
+			}
+			length = int64(binary.BigEndian.Uint16(ext))
+		} else if length == 127 {
+			ext := make([]byte, 8)
+			if _, err := io.ReadFull(reader, ext); err != nil {
+				return
+			}
+			length = int64(binary.BigEndian.Uint64(ext))
+		}
+		var maskKey [4]byte
+		if masked {
+			if _, err := io.ReadFull(reader, maskKey[:]); err != nil {
+				return
+			}
+		}
+
+		// Handle Ping -> Pong
+		if opcode == 0x9 && length <= 125 {
+			payload := make([]byte, length)
+			if _, err := io.ReadFull(reader, payload); err != nil {
+				return
+			}
+			// Unmask if masked
+			if masked {
+				for i := int64(0); i < length; i++ {
+					payload[i] ^= maskKey[i%4]
+				}
+			}
+			_ = writeWSFrame(c.conn, 0xA, payload) // best-effort pong
+			continue
+		}
+
+		// Close frame
+		if opcode == 0x8 {
+			// Drain payload if any, then exit
+			if _, err := io.CopyN(io.Discard, reader, length); err != nil {
+				return
+			}
+			return
+		}
+
+		// For other frames, just discard payload
+		if _, err := io.CopyN(io.Discard, reader, length); err != nil {
+			return
+		}
+	}
+}
+
+// writePump sends queued messages to the client and pings periodically to keep the connection alive.
+func (c *Client) writePump() {
+	ticker := time.NewTicker(30 * time.Second)
+	defer func() {
+		ticker.Stop()
+		_ = c.conn.Close()
+	}()
+	for {
+		select {
+		case msg, ok := <-c.send:
+			if !ok {
+				// try to send close frame
+				_ = writeWSFrame(c.conn, 0x8, nil)
+				return
+			}
+			if err := writeWSFrame(c.conn, 0x1, msg); err != nil {
+				return
+			}
+		case <-ticker.C:
+			// Send a ping to keep connections alive behind proxies
+			_ = writeWSFrame(c.conn, 0x9, []byte("ping"))
+		}
+	}
+}

cmd/backoffice/main.go

@@ -0,0 +1,210 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"log"
+	"net/http"
+	"os"
+	"time"
+
+	actor "git.k6n.net/go-cart-actor/pkg/actor"
+	"git.k6n.net/go-cart-actor/pkg/cart"
+	"git.k6n.net/go-cart-actor/pkg/checkout"
+	"github.com/matst80/go-redis-inventory/pkg/inventory"
+	"github.com/matst80/slask-finder/pkg/messaging"
+	amqp "github.com/rabbitmq/amqp091-go"
+	"github.com/redis/go-redis/v9"
+)
+
+type CartFileInfo struct {
+	ID       string      `json:"id"`
+	CartId   cart.CartId `json:"cartId"`
+	Size     int64       `json:"size"`
+	Modified time.Time   `json:"modified"`
+}
+
+type CheckoutFileInfo struct {
+	ID         string              `json:"id"`
+	CheckoutId checkout.CheckoutId `json:"checkoutId"`
+	Size       int64               `json:"size"`
+	Modified   time.Time           `json:"modified"`
+}
+
+func envOrDefault(key, def string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return def
+}
+
+func startMutationConsumer(ctx context.Context, conn *amqp.Connection, hub *Hub) error {
+	ch, err := conn.Channel()
+	if err != nil {
+		_ = conn.Close()
+		return err
+	}
+	msgs, err := messaging.DeclareBindAndConsume(ch, "cart", "mutation")
+	if err != nil {
+		_ = ch.Close()
+		return err
+	}
+
+	go func() {
+		defer ch.Close()
+
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case m, ok := <-msgs:
+				if !ok {
+					log.Fatalf("connection closed")
+					continue
+				}
+				// Log and broadcast to all websocket clients
+				log.Printf("mutation event: %s", string(m.Body))
+
+				if hub != nil {
+					select {
+					case hub.broadcast <- m.Body:
+					default:
+						// if hub queue is full, drop to avoid blocking
+					}
+				}
+				if err := m.Ack(false); err != nil {
+					log.Printf("error acknowledging message: %v", err)
+				}
+			}
+		}
+	}()
+	return nil
+}
+
+var redisAddress = os.Getenv("REDIS_ADDRESS")
+var redisPassword = os.Getenv("REDIS_PASSWORD")
+
+func main() {
+	dataDir := envOrDefault("DATA_DIR", "data")
+	addr := envOrDefault("ADDR", ":8080")
+	amqpURL := os.Getenv("AMQP_URL")
+
+	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)
+	}
+
+	_ = os.MkdirAll(dataDir, 0755)
+
+	reg := cart.NewCartMultationRegistry(cart.NewCartMutationContext(nil))
+	diskStorage := actor.NewDiskStorage[cart.CartGrain](dataDir, reg)
+
+	checkoutDataDir := envOrDefault("CHECKOUT_DATA_DIR", "checkout-data")
+	_ = os.MkdirAll(checkoutDataDir, 0755)
+
+	regCheckout := checkout.NewCheckoutMutationRegistry(checkout.NewCheckoutMutationContext())
+	diskStorageCheckout := actor.NewDiskStorage[checkout.CheckoutGrain](checkoutDataDir, regCheckout)
+
+	fs := NewFileServer(dataDir, checkoutDataDir, diskStorage, diskStorageCheckout)
+
+	hub := NewHub()
+	go hub.Run()
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /carts", fs.CartsHandler)
+	mux.HandleFunc("GET /cart/{id}", fs.CartHandler)
+	mux.HandleFunc("GET /checkouts", fs.CheckoutsHandler)
+	mux.HandleFunc("GET /checkout/{id}", fs.CheckoutHandler)
+	mux.HandleFunc("PUT /inventory/{locationId}/{sku}", func(w http.ResponseWriter, r *http.Request) {
+		inventoryLocationId := inventory.LocationID(r.PathValue("locationId"))
+		inventorySku := inventory.SKU(r.PathValue("sku"))
+		pipe := rdb.Pipeline()
+		var payload struct {
+			Quantity int64 `json:"quantity"`
+		}
+		err := json.NewDecoder(r.Body).Decode(&payload)
+		if err != nil {
+			http.Error(w, "invalid payload", http.StatusBadRequest)
+			return
+		}
+		inventoryService.UpdateInventory(r.Context(), pipe, inventorySku, inventoryLocationId, payload.Quantity)
+
+		_, err = pipe.Exec(r.Context())
+		if err != nil {
+			http.Error(w, "failed to update inventory", http.StatusInternalServerError)
+			return
+		}
+		err = inventoryService.SendInventoryChanged(r.Context(), inventorySku, inventoryLocationId)
+		if err != nil {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+	})
+	mux.HandleFunc("/promotions", fs.PromotionsHandler)
+	mux.HandleFunc("/vouchers", fs.VoucherHandler)
+	mux.HandleFunc("/promotion/{id}", fs.PromotionPartHandler)
+
+	mux.HandleFunc("/ws", hub.ServeWS)
+	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()
+
+	if amqpURL != "" {
+		conn, err := amqp.Dial(amqpURL)
+		if err != nil {
+			log.Fatalf("failed to connect to RabbitMQ: %v", err)
+		}
+		if err := startMutationConsumer(ctx, conn, hub); err != nil {
+			log.Printf("AMQP listener disabled: %v", err)
+		} else {
+			log.Printf("AMQP listener connected")
+		}
+	}
+
+	log.Printf("backoffice HTTP listening on %s (dataDir=%s)", addr, dataDir)
+	if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+		log.Fatalf("http server error: %v", err)
+	}
+
+	// server stopped
+}

cmd/cart/k8s-host-discovery.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"log"
+
+	"git.k6n.net/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 +1,315 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net"
+	"net/http"
+	"net/http/pprof"
+	"os"
+	"os/signal"
+	"strings"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/actor"
+	"git.k6n.net/go-cart-actor/pkg/cart"
+	"git.k6n.net/go-cart-actor/pkg/promotions"
+	"git.k6n.net/go-cart-actor/pkg/proxy"
+	"git.k6n.net/go-cart-actor/pkg/voucher"
+	"github.com/matst80/go-redis-inventory/pkg/inventory"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/redis/go-redis/v9"
+	"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")
+
+func getCountryFromHost(host string) string {
+	if strings.Contains(strings.ToLower(host), "-no") {
+		return "no"
+	}
+	if strings.Contains(strings.ToLower(host), "-se") {
+		return "se"
+	}
+	return ""
+}
+
+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() {
+
+	controlPlaneConfig := actor.DefaultServerConfig()
+
+	promotionData, err := promotions.LoadStateFile("data/promotions.json")
+	if err != nil {
+		log.Printf("Error loading promotions: %v\n", err)
+	}
+
+	log.Printf("loaded %d promotions", len(promotionData.State.Promotions))
+
+	inventoryPubSub := actor.NewPubSub[inventory.InventoryChange]()
+
+	// promotionService := promotions.NewPromotionService(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)
+	}
+
+	inventoryReservationService, err := inventory.NewRedisCartReservationService(rdb)
+	if err != nil {
+		log.Fatalf("Error creating inventory reservation service: %v\n", err)
+	}
+
+	reg := cart.NewCartMultationRegistry(cart.NewCartMutationContext(inventoryReservationService))
+	reg.RegisterProcessor(
+		actor.NewMutationProcessor(func(ctx context.Context, g *cart.CartGrain) error {
+			_, span := tracer.Start(ctx, "Totals and promotions")
+			defer span.End()
+			g.UpdateTotals()
+			g.Version++
+			// promotionCtx := promotions.NewContextFromCart(g, promotions.WithNow(time.Now()), promotions.WithCustomerSegment("vip"))
+			// _, actions := promotionService.EvaluateAll(promotionData.State.Promotions, promotionCtx)
+			// for _, action := range actions {
+
+			// 	log.Printf("apply: %+v", action)
+
+			// 	g.UpdateTotals()
+			// }
+			return nil
+		}),
+	)
+
+	diskStorage := actor.NewDiskStorage[cart.CartGrain]("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)
+		},
+		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)
+	}
+
+	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)
+	// 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)
+
+	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()
+	}()
+
+	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.Print("Server started at port 8080")
+
+	go http.ListenAndServe(":8081", 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 +1,530 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"log"
+	"net/http"
+	"strconv"
+	"sync"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/actor"
+	"git.k6n.net/go-cart-actor/pkg/cart"
+	messages "git.k6n.net/go-cart-actor/proto/cart"
+
+	"git.k6n.net/go-cart-actor/pkg/voucher"
+	"github.com/matst80/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"
+
+	"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
+	inventoryService   inventory.InventoryService
+	reservationService inventory.CartReservationService
+}
+
+func NewPoolServer(pool actor.GrainPool[cart.CartGrain], pod_name string, inventoryService inventory.InventoryService, inventoryReservationService inventory.CartReservationService) *PoolServer {
+	srv := &PoolServer{
+		GrainPool:          pool,
+		pod_name:           pod_name,
+		inventoryService:   inventoryService,
+		reservationService: inventoryReservationService,
+	}
+
+	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"`
+}
+
+type SetCartItems struct {
+	Country string `json:"country"`
+	Items   []Item `json:"items"`
+}
+
+func getMultipleAddMessages(ctx context.Context, items []Item, country string) []proto.Message {
+	wg := sync.WaitGroup{}
+	mu := sync.Mutex{}
+	msgs := make([]proto.Message, 0, len(items))
+	for _, itm := range items {
+		wg.Go(
+			func() {
+				msg, err := GetItemAddMessage(ctx, itm.Sku, itm.Quantity, country, itm.StoreId)
+				if err != nil {
+					log.Printf("error adding item %s: %v", itm.Sku, err)
+					return
+				}
+				mu.Lock()
+				msgs = append(msgs, msg)
+				mu.Unlock()
+			})
+	}
+	wg.Wait()
+	return msgs
+}
+
+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
+	}
+
+	msgs := make([]proto.Message, 0, len(setCartItems.Items)+1)
+	msgs = append(msgs, &messages.ClearCartRequest{})
+	msgs = append(msgs, getMultipleAddMessages(r.Context(), setCartItems.Items, setCartItems.Country)...)
+
+	reply, err := s.ApplyLocal(r.Context(), id, msgs...)
+	if err != nil {
+		return err
+	}
+	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
+	}
+
+	msgs := getMultipleAddMessages(r.Context(), setCartItems.Items, setCartItems.Country)
+
+	reply, err := s.ApplyLocal(r.Context(), id, msgs...)
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, reply)
+}
+
+type AddRequest struct {
+	Sku      string  `json:"sku"`
+	Quantity int32   `json:"quantity"`
+	Country  string  `json:"country"`
+	StoreId  *string `json:"storeId"`
+}
+
+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
+	}
+	msg, err := GetItemAddMessage(r.Context(), addRequest.Sku, int(addRequest.Quantity), addRequest.Country, addRequest.StoreId)
+	if err != nil {
+		return err
+	}
+
+	reply, err := s.ApplyLocal(r.Context(), id, msg)
+	if err != nil {
+		return err
+	}
+
+	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)
+}
+
+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)))
+
+	//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)))
+}

cmd/cart/product-fetcher.go

@@ -0,0 +1,150 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+
+	"git.k6n.net/go-cart-actor/pkg/cart"
+	messages "git.k6n.net/go-cart-actor/proto/cart"
+
+	"github.com/matst80/slask-finder/pkg/index"
+)
+
+// TODO make this configurable
+func getBaseUrl(country string) string {
+	// if country == "se" {
+	// 	return "http://s10n-se:8080"
+	// }
+	if country == "no" {
+		return "http://s10n-no.s10n:8080"
+	}
+	if country == "se" {
+		return "http://s10n-se.s10n:8080"
+	}
+	return "http://localhost:8082"
+}
+
+func FetchItem(ctx context.Context, sku string, country string) (*index.DataItem, error) {
+	baseUrl := getBaseUrl(country)
+	req, err := http.NewRequest("GET", fmt.Sprintf("%s/api/by-sku/%s", baseUrl, sku), nil)
+	innerCtx, span := tracer.Start(ctx, fmt.Sprintf("fetching data for %s", sku))
+	defer span.End()
+	req = req.WithContext(innerCtx)
+	if err != nil {
+		return nil, err
+	}
+	res, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	var item index.DataItem
+	err = json.NewDecoder(res.Body).Decode(&item)
+	return &item, err
+}
+
+func GetItemAddMessage(ctx context.Context, sku string, qty int, country string, storeId *string) (*messages.AddItem, error) {
+	item, err := FetchItem(ctx, sku, country)
+	if err != nil {
+		return nil, err
+	}
+	return ToItemAddMessage(item, storeId, qty, country)
+}
+
+func ToItemAddMessage(item *index.DataItem, storeId *string, qty int, country string) (*messages.AddItem, error) {
+	orgPrice, _ := getInt(item.GetNumberFieldValue(5)) // getInt(item.Fields[5])
+
+	price, err := getInt(item.GetNumberFieldValue(4)) //Fields[4]
+	if err != nil {
+		return nil, err
+	}
+	stk := item.GetStock()
+	stock := cart.StockStatus(0)
+
+	if storeId == nil {
+		centralStock, ok := stk[country]
+		if ok {
+			if !item.Buyable {
+				return nil, fmt.Errorf("item not available")
+			}
+
+			if centralStock == 0 && item.SaleStatus == "TBD" {
+				return nil, fmt.Errorf("no items available")
+			}
+			stock = cart.StockStatus(centralStock)
+		}
+
+	} else {
+		if !item.BuyableInStore {
+			return nil, fmt.Errorf("item not available in store")
+		}
+		storeStock, ok := stk[*storeId]
+		if ok {
+			stock = cart.StockStatus(storeStock)
+		}
+
+	}
+
+	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)
+
+	cgm, _ := item.GetStringFieldValue(35) // Customer Group Membership
+
+	return &messages.AddItem{
+		ItemId:      uint32(item.Id),
+		Quantity:    int32(qty),
+		Price:       int64(price),
+		OrgPrice:    int64(orgPrice),
+		Sku:         item.GetSku(),
+		Name:        item.Title,
+		Image:       item.Img,
+		Stock:       int32(stock),
+		Brand:       brand,
+		Category:    category,
+		Category2:   category2,
+		Category3:   category3,
+		Category4:   category4,
+		Category5:   category5,
+		Tax:         getTax(articleType),
+		SellerId:    sellerId,
+		SellerName:  sellerName,
+		ArticleType: articleType,
+		Disclaimer:  item.Disclaimer,
+		Country:     country,
+		Outlet:      outlet,
+		StoreId:     storeId,
+		SaleStatus:  item.SaleStatus,
+		Cgm:         cgm,
+	}, nil
+}
+
+func getTax(articleType string) int32 {
+	switch articleType {
+	case "ZDIE":
+		return 600
+	default:
+		return 2500
+	}
+}
+
+func getInt(data float64, ok bool) (int, error) {
+	if !ok {
+		return 0, fmt.Errorf("invalid type")
+	}
+	return int(data), nil
+}

cmd/cart/utils.go

@@ -0,0 +1,138 @@
+package main
+
+import (
+	"log"
+	"net/http"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/cart"
+	"github.com/matst80/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 +1,264 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log"
+	"net/http"
+	"net/url"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/cart"
+	messages "git.k6n.net/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
+				}
+				//}
+
+			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 {
+						log.Printf("Payment captured successfully: %+v", res)
+						s.ApplyAnywhere(r.Context(), *checkoutId, &messages.OrderCreated{
+							OrderId: res.PaymentPspReference,
+							Status:  item.EventCode,
+						})
+					}
+				}
+			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)
+
+}
+
+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 +1,67 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/cart"
+)
+
+type CartClient struct {
+	httpClient *http.Client
+	baseUrl    string
+}
+
+func NewCartClient(baseUrl string) *CartClient {
+	return &CartClient{
+		httpClient: &http.Client{Timeout: 10 * time.Second},
+		baseUrl:    baseUrl,
+	}
+}
+
+// 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
+	}
+	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/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 +1,208 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+
+	"git.k6n.net/go-cart-actor/pkg/cart"
+	"git.k6n.net/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"
+)
+
+// 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
+	// Terms        string
+	// Checkout     string
+	// Confirmation 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/checkout?order_id={checkout.order.id}&provider=klarna", meta.SiteUrl),
+			Confirmation: fmt.Sprintf("%s/checkout?order_id={checkout.order.id}&provider=klarna", meta.SiteUrl),
+			Notification: "https://cart.k6n.net/payment/klarna/notification",
+			Validation:   "https://cart.k6n.net/payment/klarna/validate",
+			Push:         "https://cart.k6n.net/payment/klarna/push?order_id={checkout.order.id}",
+		},
+	}
+
+	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)
+	return &CheckoutMeta{
+		ClientIp: getClientIp(r),
+		SiteUrl:  fmt.Sprintf("https://%s", host),
+		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/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 +1,277 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/cart"
+	"git.k6n.net/go-cart-actor/pkg/checkout"
+	messages "git.k6n.net/go-cart-actor/proto/checkout"
+	"github.com/matst80/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)
+		err = s.inventoryService.ReserveInventory(r.Context(), inventoryRequests...)
+
+		if err != nil {
+			logger.WarnContext(r.Context(), "placeorder inventory reservation failed")
+			w.WriteHeader(http.StatusNotAcceptable)
+			return
+		}
+		s.Apply(r.Context(), uint64(grain.Id), &messages.InventoryReserved{
+			Id:     grain.Id.String(),
+			Status: "success",
+		})
+	}
+
+	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(),
+	})
+
+	// err = confirmOrder(r.Context(), order, orderHandler)
+	// if err != nil {
+	// 	log.Printf("Error confirming order: %v\n", err)
+	// 	w.WriteHeader(http.StatusInternalServerError)
+	// 	return
+	// }
+
+	// err = triggerOrderCompleted(r.Context(), a.server, order)
+	// if err != nil {
+	// 	log.Printf("Error processing cart message: %v\n", err)
+	// 	w.WriteHeader(http.StatusInternalServerError)
+	// 	return
+	// }
+	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>
+`
+
+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 +1,201 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"os/signal"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/actor"
+	"git.k6n.net/go-cart-actor/pkg/checkout"
+	"git.k6n.net/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"
+	"github.com/matst80/go-redis-inventory/pkg/inventory"
+	"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
+
+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)
+	}
+
+	diskStorage := actor.NewDiskStorage[checkout.CheckoutGrain]("data", 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)
+
+	syncedServer := NewCheckoutPoolServer(pool, fmt.Sprintf("%s, %s", name, podIp), klarnaClient, cartClient, adyenClient)
+	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)
+
+	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/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 +1,543 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"log"
+	"net/http"
+	"os"
+	"strconv"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/actor"
+	"git.k6n.net/go-cart-actor/pkg/cart"
+	"git.k6n.net/go-cart-actor/pkg/checkout"
+	messages "git.k6n.net/go-cart-actor/proto/checkout"
+
+	adyen "github.com/adyen/adyen-go-api-library/v21/src/adyen"
+	"github.com/matst80/go-redis-inventory/pkg/inventory"
+	amqp "github.com/rabbitmq/amqp091-go"
+
+	"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
+	inventoryService *inventory.RedisInventoryService
+}
+
+func NewCheckoutPoolServer(pool actor.GrainPool[checkout.CheckoutGrain], pod_name string, klarnaClient *KlarnaClient, cartClient *CartClient, adyenClient *adyen.APIClient) *CheckoutPoolServer {
+	srv := &CheckoutPoolServer{
+		GrainPool:    pool,
+		pod_name:     pod_name,
+		klarnaClient: klarnaClient,
+		cartClient:   cartClient,
+		adyenClient:  adyenClient,
+	}
+
+	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) 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
+	}
+
+	// Create checkout with same ID as cart
+	var checkoutId checkout.CheckoutId = cart.MustNewCartId()
+	cookie, err := r.Cookie(checkoutCookieName)
+	if err == nil {
+		parsed, ok := cart.ParseCartId(cookie.Value)
+		if ok {
+			checkoutId = parsed
+		}
+	}
+
+	// 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)
+
+	conn, err := amqp.Dial(amqpUrl)
+	if err != nil {
+		log.Fatalf("failed to connect to RabbitMQ: %v", err)
+	}
+
+	orderHandler := NewAmqpOrderHandler(conn)
+	orderHandler.DefineQueue()
+
+	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("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 +1,144 @@
+package main
+
+import (
+	"context"
+	"log"
+	"net/http"
+	"strings"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/cart"
+	"git.k6n.net/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
+}
+
+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"
+}
+
+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 +1,158 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"log"
+	"net/http"
+	"os"
+	"sync"
+
+	"github.com/matst80/go-redis-inventory/pkg/inventory"
+	"github.com/matst80/slask-finder/pkg/index"
+	"github.com/matst80/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 {
+			var items []*index.DataItem
+			err := json.Unmarshal(d.Body, &items)
+			if err == nil {
+				log.Printf("Got upserts %d, message count %d", len(items), d.MessageCount)
+				wg := &sync.WaitGroup{}
+				for _, item := range items {
+					stockhandler.HandleItem(item, wg)
+				}
+				wg.Wait()
+				log.Print("Batch done...")
+			} else {
+				log.Printf("Failed to unmarshal upsert message %v", err)
+			}
+			return err
+		})
+		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 +1,49 @@
+package main
+
+import (
+	"context"
+	"log"
+	"strconv"
+	"strings"
+	"sync"
+
+	"github.com/matst80/go-redis-inventory/pkg/inventory"
+	"github.com/matst80/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()
+		centralStockString, ok := item.GetStringFieldValue(3)
+		if !ok {
+			centralStockString = "0"
+		}
+		centralStockString = strings.Replace(centralStockString, "+", "", -1)
+		centralStockString = strings.Replace(centralStockString, "<", "", -1)
+		centralStockString = strings.Replace(centralStockString, ">", "", -1)
+		centralStock, err := strconv.ParseInt(centralStockString, 10, 64)
+
+		if err != nil {
+			log.Printf("unable to parse central stock for item %s: %v", item.GetSku(), err)
+			centralStock = 0
+		} else {
+			s.svc.UpdateInventory(ctx, pipe, inventory.SKU(item.GetSku()), s.MainStockLocationID, int64(centralStock))
+		}
+		for id, value := range item.GetStock() {
+			s.svc.UpdateInventory(ctx, pipe, inventory.SKU(item.GetSku()), inventory.LocationID(id), int64(value))
+		}
+		_, err = pipe.Exec(ctx)
+		if err != nil {
+			log.Printf("unable to update stock: %v", err)
+		}
+	})
+}

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

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

@@ -1,7 +1,7 @@
 apiVersion: v1
 kind: Secret
 metadata:
-  name:  klarna-api-credentials
+  name: klarna-api-credentials
 data:
   username: ZjQzZDY3YjEtNzA2Yy00NTk2LTliNTgtYjg1YjU2NDEwZTUw
   password: a2xhcm5hX3Rlc3RfYXBpX0trUWhWVE5yYVZsV2FsTnhTRVp3Y1ZSSFF5UkVNRmxyY25Kd1AxSndQMGdzWmpRelpEWTNZakV0TnpBMll5MDBOVGsyTFRsaU5UZ3RZamcxWWpVMk5ERXdaVFV3TERFc2JUUkNjRFpWU1RsTllsSk1aMlEyVEc4MmRVODNZMkozUlRaaFdEZDViV3AwYkhGV1JqTjVNQzlaYXow
@@ -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: DATA_DIR
+              value: "/data/cart-actor"
+            - name: CHECKOUT_DATA_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
@@ -32,20 +136,18 @@ spec:
           requiredDuringSchedulingIgnoredDuringExecution:
             nodeSelectorTerms:
               - matchExpressions:
-                - key: kubernetes.io/arch
-                  operator: NotIn
-                  values:
-                    - arm64
+                  - key: kubernetes.io/arch
+                    operator: NotIn
+                    values:
+                      - arm64
       volumes:
         - name: data
           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
-              name: echo
+            - containerPort: 8081
+              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: DATA_DIR
+              value: "/data/cart-actor"
+            - name: CHECKOUT_DATA_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:
@@ -134,24 +256,22 @@ spec:
           requiredDuringSchedulingIgnoredDuringExecution:
             nodeSelectorTerms:
               - matchExpressions:
-                - key: kubernetes.io/hostname
-                  operator: NotIn
-                  values:
-                    - masterpi
-                - key: kubernetes.io/arch
-                  operator: In
-                  values:
-                    - arm64
+                  - 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
             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
-              name: echo
+            - containerPort: 8081
+              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/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/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.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

@@ -1,25 +1,101 @@
-apiVersion: autoscaling/v1
+apiVersion: autoscaling/v2
 kind: HorizontalPodAutoscaler
 metadata:
-  name: cart-scaler-amd
+    name: cart-scaler-amd
 spec:
-  scaleTargetRef:
-    apiVersion: apps/v1
-    kind: Deployment
-    name: cart-actor-x86
-  minReplicas: 3
-  maxReplicas: 9
-  targetCPUUtilizationPercentage: 30
+    scaleTargetRef:
+        apiVersion: apps/v1
+        kind: Deployment
+        name: cart-actor-x86
+    minReplicas: 3
+    maxReplicas: 9
+    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
+    name: cart-scaler-arm
 spec:
-  scaleTargetRef:
-    apiVersion: apps/v1
-    kind: Deployment
-    name: cart-actor-arm64
-  minReplicas: 3
-  maxReplicas: 9
-  targetCPUUtilizationPercentage: 30
+    scaleTargetRef:
+        apiVersion: apps/v1
+        kind: Deployment
+        name: cart-actor-arm64
+    minReplicas: 3
+    maxReplicas: 9
+    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

@@ -1,83 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"log"
-	"net"
-	"sync"
-	"time"
-)
-
-type DiscardedHost struct {
-	*Connection
-	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++
-		host.Tries = -1
-	} 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,
-	})
-}

discarded-host_test.go

@@ -1,18 +0,0 @@
-package main
-
-import (
-	"testing"
-	"time"
-)
-
-func TestDiscardedHost(t *testing.T) {
-	dh := NewDiscardedHostHandler(8080)
-	dh.SetReconnectHandler(func(host string) {
-		t.Log(host)
-	})
-	dh.AppendHost("localhost")
-	time.Sleep(2 * time.Second)
-	if dh.hosts[0].Tries == 0 {
-		t.Error("Host not tested")
-	}
-}

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
-}

go.mod

@@ -1,63 +1,118 @@
-module git.tornberg.me/go-cart-actor
+module git.k6n.net/go-cart-actor
 
-go 1.24.2
+go 1.25.4
 
 require (
-	github.com/matst80/slask-finder v0.0.0-20250418094723-2eb7d6615761
-	github.com/prometheus/client_golang v1.22.0
+	github.com/adyen/adyen-go-api-library/v21 v21.1.0
+	github.com/google/uuid v1.6.0
+	github.com/matst80/go-redis-inventory v0.0.0-20251126173508-51b30de2d86e
+	github.com/matst80/slask-finder v0.0.0-20251125182907-9e57f193127a
+	github.com/prometheus/client_golang v1.23.2
 	github.com/rabbitmq/amqp091-go v1.10.0
-	github.com/yudhasubki/netpool v0.0.0-20230717065341-3c1353ca328e
-	google.golang.org/protobuf v1.36.6
-	k8s.io/api v0.32.3
-	k8s.io/apimachinery v0.32.3
-	k8s.io/client-go v0.32.3
+	github.com/redis/go-redis/v9 v9.17.0
+	go.opentelemetry.io/contrib/bridges/otelslog v0.13.0
+	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.63.0
+	go.opentelemetry.io/otel v1.38.0
+	go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc v0.14.0
+	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc v1.38.0
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.38.0
+	go.opentelemetry.io/otel/log v0.14.0
+	go.opentelemetry.io/otel/metric v1.38.0
+	go.opentelemetry.io/otel/sdk v1.38.0
+	go.opentelemetry.io/otel/sdk/log v0.14.0
+	go.opentelemetry.io/otel/sdk/metric v1.38.0
+	go.opentelemetry.io/otel/trace v1.38.0
+	google.golang.org/grpc v1.77.0
+	google.golang.org/protobuf v1.36.10
+	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 v2.14.4 // indirect
 	github.com/beorn7/perks v1.0.1 // 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/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
-	github.com/emicklei/go-restful/v3 v3.12.2 // indirect
-	github.com/fxamacker/cbor/v2 v2.8.0 // indirect
-	github.com/go-logr/logr v1.4.2 // indirect
-	github.com/go-openapi/jsonpointer v0.21.1 // indirect
-	github.com/go-openapi/jsonreference v0.21.0 // indirect
-	github.com/go-openapi/swag v0.23.1 // 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-logr/stdr v1.2.2 // indirect
+	github.com/go-openapi/jsonpointer v0.22.3 // indirect
+	github.com/go-openapi/jsonreference v0.21.3 // indirect
+	github.com/go-openapi/swag v0.25.4 // indirect
+	github.com/go-openapi/swag/cmdutils v0.25.4 // indirect
+	github.com/go-openapi/swag/conv v0.25.4 // indirect
+	github.com/go-openapi/swag/fileutils v0.25.4 // indirect
+	github.com/go-openapi/swag/jsonname v0.25.4 // indirect
+	github.com/go-openapi/swag/jsonutils v0.25.4 // indirect
+	github.com/go-openapi/swag/loading v0.25.4 // indirect
+	github.com/go-openapi/swag/mangling v0.25.4 // indirect
+	github.com/go-openapi/swag/netutils v0.25.4 // indirect
+	github.com/go-openapi/swag/stringutils v0.25.4 // 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/golang/protobuf v1.5.4 // indirect
-	github.com/google/gnostic-models v0.6.9 // indirect
+	github.com/google/gnostic-models v0.7.1 // indirect
 	github.com/google/go-cmp v0.7.0 // indirect
-	github.com/google/gofuzz v1.2.0 // indirect
-	github.com/google/uuid v1.6.0 // indirect
+	github.com/gorilla/schema v1.4.1 // indirect
+	github.com/grpc-ecosystem/grpc-gateway/v2 v2.27.3 // indirect
 	github.com/josharian/intern v1.0.0 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
-	github.com/mailru/easyjson v0.9.0 // 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 v1.0.2 // 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/pkg/errors v0.9.1 // 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 v0.63.0 // indirect
-	github.com/prometheus/procfs v0.16.0 // indirect
-	github.com/redis/go-redis/v9 v9.7.0 // indirect
-	github.com/spf13/pflag v1.0.6 // indirect
+	github.com/prometheus/common v0.67.4 // indirect
+	github.com/prometheus/procfs v0.19.2 // 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
-	golang.org/x/net v0.39.0 // indirect
-	golang.org/x/oauth2 v0.29.0 // indirect
-	golang.org/x/sys v0.32.0 // indirect
-	golang.org/x/term v0.31.0 // indirect
-	golang.org/x/text v0.24.0 // indirect
-	golang.org/x/time v0.11.0 // indirect
-	golang.org/x/tools v0.32.0 // indirect
-	gopkg.in/evanphx/json-patch.v4 v4.12.0 // indirect
+	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.38.0 // indirect
+	go.opentelemetry.io/proto/otlp v1.9.0 // indirect
+	go.yaml.in/yaml/v2 v2.4.3 // indirect
+	go.yaml.in/yaml/v3 v3.0.4 // indirect
+	go.yaml.in/yaml/v4 v4.0.0-rc.3 // indirect
+	golang.org/x/mod v0.30.0 // indirect
+	golang.org/x/net v0.47.0 // indirect
+	golang.org/x/oauth2 v0.33.0 // indirect
+	golang.org/x/sync v0.18.0 // indirect
+	golang.org/x/sys v0.38.0 // indirect
+	golang.org/x/term v0.37.0 // indirect
+	golang.org/x/text v0.31.0 // indirect
+	golang.org/x/time v0.14.0 // indirect
+	golang.org/x/tools v0.39.0 // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20251124214823-79d6a2a48846 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20251124214823-79d6a2a48846 // 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 v0.0.0-20250318190949-c8a335a9a2ff // indirect
-	k8s.io/utils v0.0.0-20250321185631-1f6e0b77f77e // indirect
-	sigs.k8s.io/json v0.0.0-20241014173422-cfa47c3a1cc8 // 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/v4 v4.7.0 // indirect
-	sigs.k8s.io/yaml v1.4.0 // 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

@@ -1,11 +1,19 @@
-github.com/Flaconi/go-klarna v0.0.0-20230216165926-e2f708c721d9 h1:U5gu3M9/khqtvgg6iRKo0+nxGEfPHWFHRlKrbZvFxIY=
-github.com/Flaconi/go-klarna v0.0.0-20230216165926-e2f708c721d9/go.mod h1:+LVFV9FXH5cwN1VcU30WcNYRs5FhkEtL7/IqqTD42cU=
+github.com/RoaringBitmap/roaring/v2 v2.14.4 h1:4aKySrrg9G/5oRtJ3TrZLObVqxgQ9f1znCRBwEwjuVw=
+github.com/RoaringBitmap/roaring/v2 v2.14.4/go.mod h1:oMvV6omPWr+2ifRdeZvVJyaz+aoEUopyv5iH0u/+wbY=
+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 v1.24.4 h1:95H15Og1clikBrKr/DuzMXkQzECs1M6hhoGXLwLQOZE=
+github.com/bits-and-blooms/bitset v1.24.4/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=
@@ -14,36 +22,84 @@ github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1
 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f h1:lO4WD4F/rVNCu3HqELle0jiPLLBs70cWOduZpkS1E78=
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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
-}

id_test.go

@@ -1,19 +0,0 @@
-package main
-
-import (
-	"testing"
-)
-
-func TestIdGeneration(t *testing.T) {
-	// Generate a random ID
-	id := NewCartId()
-
-	// Generate a random ID
-	id2 := NewCartId()
-	// Compare the two IDs
-	if id == id2 {
-		t.Errorf("IDs are the same: %v == %v", id, id2)
-	} else {
-		t.Log("ID generation test passed", id, id2)
-	}
-}

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

@@ -1,413 +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)
-	}
-
-	hg, err := NewGrainHandler(app.pool, ":1337")
-	if err != nil {
-		log.Fatalf("Error creating handler: %v\n", err)
-	}
-
-	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) {
-		if !hg.IsHealthy() {
-			w.WriteHeader(http.StatusInternalServerError)
-			w.Write([]byte("handler not healthy"))
-			return
-		}
-		if !syncedPool.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("/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
-	}()
-
-	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
-}

main_test.go

@@ -1,286 +0,0 @@
-package main
-
-import (
-	"os"
-	"testing"
-)
-
-func TestGetCountryFromHost(t *testing.T) {
-	tests := []struct {
-		name     string
-		host     string
-		expected string
-	}{
-		{
-			name:     "Norwegian host",
-			host:     "s10n-no.tornberg.me",
-			expected: "no",
-		},
-		{
-			name:     "Swedish host",
-			host:     "s10n-se.tornberg.me",
-			expected: "se",
-		},
-		{
-			name:     "Host with -no in the middle",
-			host:     "api-no-staging.tornberg.me",
-			expected: "no",
-		},
-		{
-			name:     "Host without country suffix",
-			host:     "s10n.tornberg.me",
-			expected: "se",
-		},
-		{
-			name:     "Host with different domain",
-			host:     "example-no.com",
-			expected: "no",
-		},
-		{
-			name:     "Empty host",
-			host:     "",
-			expected: "se",
-		},
-		{
-			name:     "Host with uppercase",
-			host:     "S10N-NO.TORNBERG.ME",
-			expected: "no",
-		},
-		{
-			name:     "Host with mixed case",
-			host:     "S10n-No.Tornberg.Me",
-			expected: "no",
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			result := getCountryFromHost(tt.host)
-			if result != tt.expected {
-				t.Errorf("getCountryFromHost(%q) = %q, want %q", tt.host, result, tt.expected)
-			}
-		})
-	}
-}
-
-func TestGetCheckoutOrder(t *testing.T) {
-	// Save original environment variable and restore after test
-	originalCartBaseUrl := os.Getenv("CART_BASE_URL")
-	defer func() {
-		if originalCartBaseUrl == "" {
-			os.Unsetenv("CART_BASE_URL")
-		} else {
-			os.Setenv("CART_BASE_URL", originalCartBaseUrl)
-		}
-	}()
-
-	tests := []struct {
-		name         string
-		host         string
-		cartId       CartId
-		cartBaseUrl  string
-		expectedUrls struct {
-			terms        string
-			checkout     string
-			confirmation string
-			validation   string
-			push         string
-			country      string
-		}
-	}{
-		{
-			name:        "Norwegian host with default cart base URL",
-			host:        "s10n-no.tornberg.me",
-			cartId:      ToCartId("test-cart-123"),
-			cartBaseUrl: "", // Use default
-			expectedUrls: struct {
-				terms        string
-				checkout     string
-				confirmation string
-				validation   string
-				push         string
-				country      string
-			}{
-				terms:        "https://s10n-no.tornberg.me/terms",
-				checkout:     "https://s10n-no.tornberg.me/checkout?order_id={checkout.order.id}",
-				confirmation: "https://s10n-no.tornberg.me/confirmation/{checkout.order.id}",
-				validation:   "https://cart.tornberg.me/validation",
-				push:         "https://cart.tornberg.me/push?order_id={checkout.order.id}",
-				country:      "no",
-			},
-		},
-		{
-			name:        "Swedish host with default cart base URL",
-			host:        "s10n-se.tornberg.me",
-			cartId:      ToCartId("test-cart-456"),
-			cartBaseUrl: "", // Use default
-			expectedUrls: struct {
-				terms        string
-				checkout     string
-				confirmation string
-				validation   string
-				push         string
-				country      string
-			}{
-				terms:        "https://s10n-se.tornberg.me/terms",
-				checkout:     "https://s10n-se.tornberg.me/checkout?order_id={checkout.order.id}",
-				confirmation: "https://s10n-se.tornberg.me/confirmation/{checkout.order.id}",
-				validation:   "https://cart.tornberg.me/validation",
-				push:         "https://cart.tornberg.me/push?order_id={checkout.order.id}",
-				country:      "se",
-			},
-		},
-		{
-			name:        "Norwegian host with custom cart base URL",
-			host:        "s10n-no.tornberg.me",
-			cartId:      ToCartId("test-cart-789"),
-			cartBaseUrl: "https://custom-cart.example.com",
-			expectedUrls: struct {
-				terms        string
-				checkout     string
-				confirmation string
-				validation   string
-				push         string
-				country      string
-			}{
-				terms:        "https://s10n-no.tornberg.me/terms",
-				checkout:     "https://s10n-no.tornberg.me/checkout?order_id={checkout.order.id}",
-				confirmation: "https://s10n-no.tornberg.me/confirmation/{checkout.order.id}",
-				validation:   "https://custom-cart.example.com/validation",
-				push:         "https://custom-cart.example.com/push?order_id={checkout.order.id}",
-				country:      "no",
-			},
-		},
-		{
-			name:        "Host without country code defaults to Swedish",
-			host:        "s10n.tornberg.me",
-			cartId:      ToCartId("test-cart-default"),
-			cartBaseUrl: "",
-			expectedUrls: struct {
-				terms        string
-				checkout     string
-				confirmation string
-				validation   string
-				push         string
-				country      string
-			}{
-				terms:        "https://s10n.tornberg.me/terms",
-				checkout:     "https://s10n.tornberg.me/checkout?order_id={checkout.order.id}",
-				confirmation: "https://s10n.tornberg.me/confirmation/{checkout.order.id}",
-				validation:   "https://cart.tornberg.me/validation",
-				push:         "https://cart.tornberg.me/push?order_id={checkout.order.id}",
-				country:      "se",
-			},
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			// Set up environment variable for this test
-			if tt.cartBaseUrl == "" {
-				os.Unsetenv("CART_BASE_URL")
-			} else {
-				os.Setenv("CART_BASE_URL", tt.cartBaseUrl)
-			}
-
-			result := getCheckoutOrder(tt.host, tt.cartId)
-
-			// Verify the result is not nil
-			if result == nil {
-				t.Fatal("getCheckoutOrder returned nil")
-			}
-
-			// Check each URL field
-			if result.Terms != tt.expectedUrls.terms {
-				t.Errorf("Terms URL: got %q, want %q", result.Terms, tt.expectedUrls.terms)
-			}
-
-			if result.Checkout != tt.expectedUrls.checkout {
-				t.Errorf("Checkout URL: got %q, want %q", result.Checkout, tt.expectedUrls.checkout)
-			}
-
-			if result.Confirmation != tt.expectedUrls.confirmation {
-				t.Errorf("Confirmation URL: got %q, want %q", result.Confirmation, tt.expectedUrls.confirmation)
-			}
-
-			if result.Validation != tt.expectedUrls.validation {
-				t.Errorf("Validation URL: got %q, want %q", result.Validation, tt.expectedUrls.validation)
-			}
-
-			if result.Push != tt.expectedUrls.push {
-				t.Errorf("Push URL: got %q, want %q", result.Push, tt.expectedUrls.push)
-			}
-
-			if result.Country != tt.expectedUrls.country {
-				t.Errorf("Country: got %q, want %q", result.Country, tt.expectedUrls.country)
-			}
-		})
-	}
-}
-
-func TestGetCheckoutOrderIntegration(t *testing.T) {
-	// Test that both functions work together correctly
-	hosts := []string{"s10n-no.tornberg.me", "s10n-se.tornberg.me"}
-	cartId := ToCartId("integration-test-cart")
-
-	for _, host := range hosts {
-		t.Run(host, func(t *testing.T) {
-			// Get country from host
-			country := getCountryFromHost(host)
-
-			// Get checkout order
-			order := getCheckoutOrder(host, cartId)
-
-			// Verify that the country in the order matches what getCountryFromHost returns
-			if order.Country != country {
-				t.Errorf("Country mismatch: getCountryFromHost(%q) = %q, but order.Country = %q",
-					host, country, order.Country)
-			}
-
-			// Verify that all URLs contain the correct host
-			expectedBaseUrl := "https://" + host
-
-			if !containsPrefix(order.Terms, expectedBaseUrl) {
-				t.Errorf("Terms URL should start with %q, got %q", expectedBaseUrl, order.Terms)
-			}
-
-			if !containsPrefix(order.Checkout, expectedBaseUrl) {
-				t.Errorf("Checkout URL should start with %q, got %q", expectedBaseUrl, order.Checkout)
-			}
-
-			if !containsPrefix(order.Confirmation, expectedBaseUrl) {
-				t.Errorf("Confirmation URL should start with %q, got %q", expectedBaseUrl, order.Confirmation)
-			}
-		})
-	}
-}
-
-// Helper function to check if a string starts with a prefix
-func containsPrefix(s, prefix string) bool {
-	return len(s) >= len(prefix) && s[:len(prefix)] == prefix
-}
-
-// Benchmark tests to measure performance
-func BenchmarkGetCountryFromHost(b *testing.B) {
-	hosts := []string{
-		"s10n-no.tornberg.me",
-		"s10n-se.tornberg.me",
-		"api-no-staging.tornberg.me",
-		"s10n.tornberg.me",
-	}
-
-	for i := 0; i < b.N; i++ {
-		for _, host := range hosts {
-			getCountryFromHost(host)
-		}
-	}
-}
-
-func BenchmarkGetCheckoutOrder(b *testing.B) {
-	host := "s10n-no.tornberg.me"
-	cartId := ToCartId("benchmark-cart")
-
-	for i := 0; i < b.N; i++ {
-		getCheckoutOrder(host, cartId)
-	}
-}

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-handler_test.go

@@ -1,129 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"testing"
-
-	messages "git.tornberg.me/go-cart-actor/proto"
-)
-
-func TestAddRequest(t *testing.T) {
-	h, err := GetMessageHandler(AddRequestType)
-	if err != nil {
-		t.Errorf("Error getting message handler: %v\n", err)
-	}
-	if h == nil {
-		t.Errorf("Expected message handler, got nil\n")
-	}
-	message := Message{
-		Type: AddRequestType,
-		Content: &messages.AddRequest{
-			Quantity: 2,
-			Sku:      "123",
-		},
-	}
-	var b bytes.Buffer
-	err = h.Write(&message, &b)
-	if err != nil {
-		t.Errorf("Error writing message: %v\n", err)
-	}
-	result, err := h.Read(b.Bytes())
-	if err != nil {
-		t.Errorf("Error reading message: %v\n", err)
-	}
-	if result == nil {
-		t.Errorf("Expected result, got nil\n")
-	}
-	r, ok := result.(*messages.AddRequest)
-	if !ok {
-		t.Errorf("Expected AddRequest, got %T\n", result)
-	}
-	if r.Quantity != 2 {
-		t.Errorf("Expected quantity 2, got %d\n", r.Quantity)
-	}
-	if r.Sku != "123" {
-		t.Errorf("Expected sku '123', got %s\n", r.Sku)
-	}
-}
-
-func TestItemRequest(t *testing.T) {
-	h, err := GetMessageHandler(AddItemType)
-	if err != nil {
-		t.Errorf("Error getting message handler: %v\n", err)
-	}
-	if h == nil {
-		t.Errorf("Expected message handler, got nil\n")
-	}
-	message := Message{
-		Type: AddItemType,
-		Content: &messages.AddItem{
-			Quantity: 2,
-			Sku:      "123",
-			Price:    100,
-			Name:     "Test item",
-			Image:    "test.jpg",
-		},
-	}
-	var b bytes.Buffer
-	err = h.Write(&message, &b)
-	if err != nil {
-		t.Errorf("Error writing message: %v\n", err)
-	}
-	result, err := h.Read(b.Bytes())
-	if err != nil {
-		t.Errorf("Error reading message: %v\n", err)
-	}
-	if result == nil {
-		t.Errorf("Expected result, got nil\n")
-	}
-	var r *messages.AddItem
-	ok := h.Is(&message)
-	if !ok {
-		t.Errorf("Expected AddRequest, got %T\n", result)
-	}
-	if r.Quantity != 2 {
-		t.Errorf("Expected quantity 2, got %d\n", r.Quantity)
-	}
-	if r.Sku != "123" {
-		t.Errorf("Expected sku '123', got %s\n", r.Sku)
-	}
-}
-
-func TestSetDeliveryMssage(t *testing.T) {
-	h, err := GetMessageHandler(SetDeliveryType)
-	if err != nil {
-		t.Errorf("Error getting message handler: %v\n", err)
-	}
-	if h == nil {
-		t.Errorf("Expected message handler, got nil\n")
-	}
-	message := Message{
-		Type: SetDeliveryType,
-		Content: &messages.SetDelivery{
-			Provider: "test",
-			Items:    []int64{1, 2},
-		},
-	}
-	var b bytes.Buffer
-	err = h.Write(&message, &b)
-	if err != nil {
-		t.Errorf("Error writing message: %v\n", err)
-	}
-	result, err := h.Read(b.Bytes())
-	if err != nil {
-		t.Errorf("Error reading message: %v\n", err)
-	}
-	if result == nil {
-		t.Errorf("Expected result, got nil\n")
-	}
-	r, ok := result.(*messages.SetDelivery)
-	if !ok {
-		t.Errorf("Expected AddRequest, got %T\n", result)
-	}
-	if len(r.Items) != 2 {
-		t.Errorf("Expected 2 items, got %d\n", len(r.Items))
-	}
-	if r.Provider != "test" {
-		t.Errorf("Expected provider 'test', got %s\n", r.Provider)
-	}
-}

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
-}

packet.go

@@ -1,89 +0,0 @@
-package main
-
-const (
-	RemoteGetState            = FrameType(0x01)
-	RemoteHandleMutation      = FrameType(0x02)
-	ResponseBody              = FrameType(0x03)
-	RemoteGetStateReply       = FrameType(0x04)
-	RemoteHandleMutationReply = FrameType(0x05)
-	RemoteCreateOrderReply    = FrameType(0x06)
-)
-
-// type CartPacket struct {
-// 	Version     PackageVersion
-// 	MessageType CartMessage
-// 	DataLength  uint32
-// 	StatusCode  uint32
-// 	Id          CartId
-// }
-
-// type Packet struct {
-// 	Version     PackageVersion
-// 	MessageType PoolMessage
-// 	DataLength  uint32
-// 	StatusCode  uint32
-// }
-
-// var headerData = make([]byte, 4)
-
-// func matchHeader(conn io.Reader) error {
-
-// 	pos := 0
-// 	for pos < 4 {
-
-// 		l, err := conn.Read(headerData)
-// 		if err != nil {
-// 			return err
-// 		}
-// 		for i := 0; i < l; i++ {
-// 			if headerData[i] == header[pos] {
-// 				pos++
-// 				if pos == 4 {
-// 					return nil
-// 				}
-// 			} else {
-// 				pos = 0
-// 			}
-// 		}
-// 	}
-// 	return nil
-// }
-
-// func ReadPacket(conn io.Reader, packet *Packet) error {
-// 	err := matchHeader(conn)
-// 	if err != nil {
-// 		return err
-// 	}
-// 	return binary.Read(conn, binary.LittleEndian, packet)
-// }
-
-// func ReadCartPacket(conn io.Reader, packet *CartPacket) error {
-// 	err := matchHeader(conn)
-// 	if err != nil {
-// 		return err
-// 	}
-// 	return binary.Read(conn, binary.LittleEndian, packet)
-// }
-
-// func GetPacketData(conn io.Reader, len uint32) ([]byte, error) {
-// 	if len == 0 {
-// 		return []byte{}, nil
-// 	}
-// 	data := make([]byte, len)
-// 	_, err := conn.Read(data)
-// 	return data, err
-// }
-
-// func ReceivePacket(conn io.Reader) (uint32, []byte, error) {
-// 	var packet Packet
-// 	err := ReadPacket(conn, &packet)
-// 	if err != nil {
-// 		return 0, nil, err
-// 	}
-
-// 	data, err := GetPacketData(conn, packet.DataLength)
-// 	if err != nil {
-// 		return 0, nil, err
-// 	}
-// 	return packet.MessageType, data, nil
-// }

pkg/actor/base62-id.go

@@ -0,0 +1,131 @@
+package actor
+
+import (
+	"crypto/rand"
+	"encoding/json"
+	"fmt"
+)
+
+type GrainId uint64
+
+const base62Alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+
+// Reverse lookup (0xFF marks invalid)
+var base62Rev [256]byte
+
+func init() {
+	for i := range base62Rev {
+		base62Rev[i] = 0xFF
+	}
+	for i := 0; i < len(base62Alphabet); i++ {
+		base62Rev[base62Alphabet[i]] = byte(i)
+	}
+}
+
+// String returns the canonical base62 encoding of the 64-bit id.
+func (id GrainId) String() string {
+	return encodeBase62(uint64(id))
+}
+
+// MarshalJSON encodes the cart id as a JSON string.
+func (id GrainId) MarshalJSON() ([]byte, error) {
+	return json.Marshal(id.String())
+}
+
+// UnmarshalJSON decodes a cart id from a JSON string containing base62 text.
+func (id *GrainId) UnmarshalJSON(data []byte) error {
+	var s string
+	if err := json.Unmarshal(data, &s); err != nil {
+		return err
+	}
+	parsed, ok := ParseGrainId(s)
+	if !ok {
+		return fmt.Errorf("invalid cart id: %q", s)
+	}
+	*id = parsed
+	return nil
+}
+
+// NewGrainId generates a new cryptographically random non-zero 64-bit id.
+func NewGrainId() (GrainId, error) {
+	var b [8]byte
+	if _, err := rand.Read(b[:]); err != nil {
+		return 0, fmt.Errorf("NewGrainId: %w", err)
+	}
+	u := (uint64(b[0]) << 56) |
+		(uint64(b[1]) << 48) |
+		(uint64(b[2]) << 40) |
+		(uint64(b[3]) << 32) |
+		(uint64(b[4]) << 24) |
+		(uint64(b[5]) << 16) |
+		(uint64(b[6]) << 8) |
+		uint64(b[7])
+	if u == 0 {
+		// Extremely unlikely; regenerate once to avoid "0" identifier if desired.
+		return NewGrainId()
+	}
+	return GrainId(u), nil
+}
+
+// MustNewGrainId panics if generation fails.
+func MustNewGrainId() GrainId {
+	id, err := NewGrainId()
+	if err != nil {
+		panic(err)
+	}
+	return id
+}
+
+// ParseGrainId parses a base62 string into a GrainId.
+// Returns (0,false) for invalid input.
+func ParseGrainId(s string) (GrainId, bool) {
+	// Accept length 1..11 (11 sufficient for 64 bits). Reject >11 immediately.
+	// Provide a slightly looser upper bound (<=16) only if you anticipate future
+	// extensions; here we stay strict.
+	if len(s) == 0 || len(s) > 11 {
+		return 0, false
+	}
+	u, ok := decodeBase62(s)
+	if !ok {
+		return 0, false
+	}
+	return GrainId(u), true
+}
+
+// MustParseGrainId panics on invalid base62 input.
+func MustParseGrainId(s string) GrainId {
+	id, ok := ParseGrainId(s)
+	if !ok {
+		panic(fmt.Sprintf("invalid cart id: %q", s))
+	}
+	return id
+}
+
+// encodeBase62 converts a uint64 to base62 (shortest form).
+func encodeBase62(u uint64) string {
+	if u == 0 {
+		return "0"
+	}
+	var buf [11]byte
+	i := len(buf)
+	for u > 0 {
+		i--
+		buf[i] = base62Alphabet[u%62]
+		u /= 62
+	}
+	return string(buf[i:])
+}
+
+// decodeBase62 converts base62 text to uint64.
+func decodeBase62(s string) (uint64, bool) {
+	var v uint64
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		d := base62Rev[c]
+		if d == 0xFF {
+			return 0, false
+		}
+		v = v*62 + uint64(d)
+	}
+	return v, true
+}

pkg/actor/disk_storage.go

@@ -0,0 +1,162 @@
+package actor
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+
+	"google.golang.org/protobuf/proto"
+)
+
+type QueueEvent struct {
+	TimeStamp time.Time
+	Message   proto.Message
+}
+
+type DiskStorage[V any] struct {
+	*StateStorage
+	path  string
+	done  chan struct{}
+	queue *sync.Map // map[uint64][]QueueEvent
+}
+
+type LogStorage[V any] interface {
+	LoadEvents(ctx context.Context, id uint64, grain Grain[V]) error
+	LoadEventsFunc(ctx context.Context, id uint64, grain Grain[V], condition func(msg proto.Message, index int, timeStamp time.Time) bool) error
+	AppendMutations(id uint64, msg ...proto.Message) error
+}
+
+func NewDiskStorage[V any](path string, registry MutationRegistry) *DiskStorage[V] {
+	return &DiskStorage[V]{
+		StateStorage: NewState(registry),
+		path:         path,
+		done:         make(chan struct{}),
+	}
+}
+
+func (s *DiskStorage[V]) SaveLoop(duration time.Duration) {
+	s.queue = &sync.Map{}
+	ticker := time.NewTicker(duration)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-s.done:
+			s.save()
+			return
+		case <-ticker.C:
+			s.save()
+		}
+	}
+}
+
+func (s *DiskStorage[V]) save() {
+	carts := 0
+	lines := 0
+	s.queue.Range(func(key, value any) bool {
+		id := key.(uint64)
+		path := s.logPath(id)
+		fh, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+		if err != nil {
+			log.Printf("failed to open event log file: %v", err)
+			return true
+		}
+		defer fh.Close()
+
+		if qe, ok := value.([]QueueEvent); ok {
+			for _, msg := range qe {
+				if err := s.Append(fh, msg.Message, msg.TimeStamp); err != nil {
+					log.Printf("failed to append event to log file: %v", err)
+				}
+				lines++
+			}
+		}
+		carts++
+		s.queue.Delete(id)
+		return true
+	})
+	if lines > 0 {
+		log.Printf("Appended %d carts and %d lines to disk", carts, lines)
+	}
+}
+
+func (s *DiskStorage[V]) logPath(id uint64) string {
+	return filepath.Join(s.path, fmt.Sprintf("%d.events.log", id))
+}
+
+func (s *DiskStorage[V]) LoadEventsFunc(ctx context.Context, id uint64, grain Grain[V], condition func(msg proto.Message, index int, timeStamp time.Time) bool) error {
+	path := s.logPath(id)
+	if _, err := os.Stat(path); errors.Is(err, os.ErrNotExist) {
+		// No log -> nothing to replay
+		return nil
+	}
+
+	fh, err := os.Open(path)
+	if err != nil {
+		return fmt.Errorf("open replay file: %w", err)
+	}
+	defer fh.Close()
+	index := 0
+	return s.Load(fh, func(msg proto.Message, when time.Time) {
+		if condition(msg, index, when) {
+			s.registry.Apply(ctx, grain, msg)
+		}
+		index++
+	})
+}
+
+func (s *DiskStorage[V]) LoadEvents(ctx context.Context, id uint64, grain Grain[V]) error {
+	path := s.logPath(id)
+	if _, err := os.Stat(path); errors.Is(err, os.ErrNotExist) {
+		// No log -> nothing to replay
+		return nil
+	}
+
+	fh, err := os.Open(path)
+	if err != nil {
+		return fmt.Errorf("open replay file: %w", err)
+	}
+	defer fh.Close()
+	return s.Load(fh, func(msg proto.Message, _ time.Time) {
+		s.registry.Apply(ctx, grain, msg)
+	})
+}
+
+func (s *DiskStorage[V]) Close() {
+	if s.queue != nil {
+		s.save()
+	}
+	close(s.done)
+}
+
+func (s *DiskStorage[V]) AppendMutations(id uint64, msg ...proto.Message) error {
+	if s.queue != nil {
+		queue := make([]QueueEvent, 0)
+		data, found := s.queue.Load(id)
+		if found {
+			queue = data.([]QueueEvent)
+		}
+		for _, m := range msg {
+			queue = append(queue, QueueEvent{Message: m, TimeStamp: time.Now()})
+		}
+		s.queue.Store(id, queue)
+		return nil
+	} else {
+		path := s.logPath(id)
+		fh, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+		if err != nil {
+			log.Printf("failed to open event log file: %v", err)
+			return err
+		}
+		defer fh.Close()
+		for _, m := range msg {
+			err = s.Append(fh, m, time.Now())
+		}
+		return err
+	}
+
+}

pkg/actor/grain.go

@@ -0,0 +1,13 @@
+package actor
+
+import (
+	"time"
+)
+
+type Grain[V any] interface {
+	GetId() uint64
+
+	GetLastAccess() time.Time
+	GetLastChange() time.Time
+	GetCurrentState() (*V, error)
+}

pkg/actor/grain_pool.go

@@ -0,0 +1,46 @@
+package actor
+
+import (
+	"context"
+	"io"
+	"net/http"
+
+	"google.golang.org/protobuf/proto"
+)
+
+type MutationResult[V any] struct {
+	Result    V             `json:"result"`
+	Mutations []ApplyResult `json:"mutations,omitempty"`
+}
+
+type GrainPool[V any] interface {
+	Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*MutationResult[V], error)
+	Get(ctx context.Context, id uint64) (*V, error)
+	OwnerHost(id uint64) (Host[V], bool)
+	Hostname() string
+	TakeOwnership(id uint64)
+	HandleOwnershipChange(host string, ids []uint64) error
+	HandleRemoteExpiry(host string, ids []uint64) error
+	Negotiate(otherHosts []string)
+	GetLocalIds() []uint64
+	IsHealthy() bool
+	Close()
+	IsKnown(string) bool
+	RemoveHost(host string)
+	AddRemoteHost(host string)
+}
+
+// Host abstracts a remote node capable of proxying cart requests.
+type Host[V any] interface {
+	AnnounceExpiry(ids []uint64)
+	Negotiate(otherHosts []string) ([]string, error)
+	Name() string
+	Proxy(id uint64, w http.ResponseWriter, r *http.Request, customBody io.Reader) (bool, error)
+	Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*MutationResult[V], error)
+	Get(ctx context.Context, id uint64) (*V, error)
+	GetActorIds() []uint64
+	Close() error
+	Ping() bool
+	IsHealthy() bool
+	AnnounceOwnership(ownerHost string, ids []uint64)
+}

pkg/actor/grpc_server.go

@@ -0,0 +1,301 @@
+package actor
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net"
+	"time"
+
+	messages "git.k6n.net/go-cart-actor/proto/control"
+	"go.opentelemetry.io/contrib/bridges/otelslog"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/reflection"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/known/anypb"
+)
+
+// ControlServer implements the ControlPlane gRPC services.
+// It delegates to a grain pool and cluster operations to a synced pool.
+type ControlServer[V any] struct {
+	messages.UnimplementedControlPlaneServer
+	pool GrainPool[V]
+}
+
+const name = "grpc_server"
+
+var (
+	tracer                 = otel.Tracer(name)
+	meter                  = otel.Meter(name)
+	logger                 = otelslog.NewLogger(name)
+	pingCalls              metric.Int64Counter
+	negotiateCalls         metric.Int64Counter
+	getLocalActorIdsCalls  metric.Int64Counter
+	announceOwnershipCalls metric.Int64Counter
+	announceExpiryCalls    metric.Int64Counter
+	closingCalls           metric.Int64Counter
+)
+
+func init() {
+	var err error
+	pingCalls, err = meter.Int64Counter("grpc.ping_calls",
+		metric.WithDescription("Number of ping calls"),
+		metric.WithUnit("{calls}"))
+	if err != nil {
+		panic(err)
+	}
+	negotiateCalls, err = meter.Int64Counter("grpc.negotiate_calls",
+		metric.WithDescription("Number of negotiate calls"),
+		metric.WithUnit("{calls}"))
+	if err != nil {
+		panic(err)
+	}
+	getLocalActorIdsCalls, err = meter.Int64Counter("grpc.get_local_actor_ids_calls",
+		metric.WithDescription("Number of get local actor ids calls"),
+		metric.WithUnit("{calls}"))
+	if err != nil {
+		panic(err)
+	}
+	announceOwnershipCalls, err = meter.Int64Counter("grpc.announce_ownership_calls",
+		metric.WithDescription("Number of announce ownership calls"),
+		metric.WithUnit("{calls}"))
+	if err != nil {
+		panic(err)
+	}
+	announceExpiryCalls, err = meter.Int64Counter("grpc.announce_expiry_calls",
+		metric.WithDescription("Number of announce expiry calls"),
+		metric.WithUnit("{calls}"))
+	if err != nil {
+		panic(err)
+	}
+	closingCalls, err = meter.Int64Counter("grpc.closing_calls",
+		metric.WithDescription("Number of closing calls"),
+		metric.WithUnit("{calls}"))
+	if err != nil {
+		panic(err)
+	}
+}
+
+func (s *ControlServer[V]) AnnounceOwnership(ctx context.Context, req *messages.OwnershipAnnounce) (*messages.OwnerChangeAck, error) {
+	ctx, span := tracer.Start(ctx, "grpc_announce_ownership")
+	defer span.End()
+	span.SetAttributes(
+		attribute.String("component", "controlplane"),
+		attribute.String("host", req.Host),
+		attribute.Int("id_count", len(req.Ids)),
+	)
+	logger.InfoContext(ctx, "announce ownership", "host", req.Host, "id_count", len(req.Ids))
+	announceOwnershipCalls.Add(ctx, 1, metric.WithAttributes(attribute.String("host", req.Host)))
+
+	err := s.pool.HandleOwnershipChange(req.Host, req.Ids)
+	if err != nil {
+		span.RecordError(err)
+		return &messages.OwnerChangeAck{
+			Accepted: false,
+			Message:  "owner change failed",
+		}, err
+	}
+
+	// log.Printf("Ack count: %d", len(req.Ids))
+	return &messages.OwnerChangeAck{
+		Accepted: true,
+		Message:  "ownership announced",
+	}, nil
+}
+
+func toAny[V any](grain V) (*anypb.Any, error) {
+	data, err := json.Marshal(grain)
+	if err != nil {
+		return nil, err
+	}
+	return &anypb.Any{
+		Value: data,
+	}, nil
+}
+
+func (s *ControlServer[V]) Get(ctx context.Context, req *messages.GetRequest) (*messages.GetReply, error) {
+	grain, err := s.pool.Get(ctx, req.Id)
+	if err != nil {
+		return nil, err
+	}
+	grainAny, err := toAny(grain)
+	if err != nil {
+		return nil, err
+	}
+	return &messages.GetReply{
+		Grain: grainAny,
+	}, nil
+}
+
+func (s *ControlServer[V]) AnnounceExpiry(ctx context.Context, req *messages.ExpiryAnnounce) (*messages.OwnerChangeAck, error) {
+	ctx, span := tracer.Start(ctx, "grpc_announce_expiry")
+	defer span.End()
+	span.SetAttributes(
+		attribute.String("component", "controlplane"),
+		attribute.String("host", req.Host),
+		attribute.Int("id_count", len(req.Ids)),
+	)
+	logger.InfoContext(ctx, "announce expiry", "host", req.Host, "id_count", len(req.Ids))
+	announceExpiryCalls.Add(ctx, 1, metric.WithAttributes(attribute.String("host", req.Host)))
+
+	err := s.pool.HandleRemoteExpiry(req.Host, req.Ids)
+	if err != nil {
+		span.RecordError(err)
+	}
+	return &messages.OwnerChangeAck{
+		Accepted: err == nil,
+		Message:  "expiry acknowledged",
+	}, nil
+}
+
+// ControlPlane: Ping
+func (s *ControlServer[V]) Ping(ctx context.Context, req *messages.Empty) (*messages.PingReply, error) {
+
+	host := s.pool.Hostname()
+
+	pingCalls.Add(ctx, 1, metric.WithAttributes(attribute.String("host", host)))
+
+	// log.Printf("got ping")
+	return &messages.PingReply{
+		Host:     host,
+		UnixTime: time.Now().Unix(),
+	}, nil
+}
+
+func (s *ControlServer[V]) Apply(ctx context.Context, in *messages.ApplyRequest) (*messages.ApplyResult, error) {
+	msgs := make([]proto.Message, len(in.Messages))
+	for i, anyMsg := range in.Messages {
+		msg, err := anyMsg.UnmarshalNew()
+		if err != nil {
+			return nil, fmt.Errorf("failed to unmarshal message: %w", err)
+		}
+		msgs[i] = msg
+	}
+	r, err := s.pool.Apply(ctx, in.Id, msgs...)
+	if err != nil {
+		return nil, err
+	}
+	grainAny, err := toAny(r)
+	if err != nil {
+		return nil, err
+	}
+	mutList := make([]*messages.MutationResult, len(in.Messages))
+	for i, msg := range r.Mutations {
+		mut, err := anypb.New(msg.Mutation)
+		if err != nil {
+			return nil, err
+		}
+		var errString *string
+		if msg.Error != nil {
+			s := msg.Error.Error()
+			errString = &s
+		}
+		mutList[i] = &messages.MutationResult{
+			Type:    msg.Type,
+			Message: mut,
+			Error:   errString,
+		}
+	}
+
+	return &messages.ApplyResult{
+		State:     grainAny,
+		Mutations: mutList,
+	}, nil
+}
+
+// ControlPlane: Negotiate (merge host views)
+func (s *ControlServer[V]) Negotiate(ctx context.Context, req *messages.NegotiateRequest) (*messages.NegotiateReply, error) {
+	ctx, span := tracer.Start(ctx, "grpc_negotiate")
+	defer span.End()
+	span.SetAttributes(
+		attribute.String("component", "controlplane"),
+		attribute.Int("known_hosts_count", len(req.KnownHosts)),
+	)
+	logger.InfoContext(ctx, "negotiate", "known_hosts_count", len(req.KnownHosts))
+	negotiateCalls.Add(ctx, 1)
+
+	s.pool.Negotiate(req.KnownHosts)
+	return &messages.NegotiateReply{Hosts: req.GetKnownHosts()}, nil
+}
+
+// ControlPlane: GetCartIds (locally owned carts only)
+func (s *ControlServer[V]) GetLocalActorIds(ctx context.Context, req *messages.Empty) (*messages.ActorIdsReply, error) {
+	ctx, span := tracer.Start(ctx, "grpc_get_local_actor_ids")
+	defer span.End()
+	ids := s.pool.GetLocalIds()
+	span.SetAttributes(
+		attribute.String("component", "controlplane"),
+		attribute.Int("id_count", len(ids)),
+	)
+	logger.InfoContext(ctx, "get local actor ids", "id_count", len(ids))
+	getLocalActorIdsCalls.Add(ctx, 1)
+
+	return &messages.ActorIdsReply{Ids: ids}, nil
+}
+
+// ControlPlane: Closing (peer shutdown notification)
+func (s *ControlServer[V]) Closing(ctx context.Context, req *messages.ClosingNotice) (*messages.OwnerChangeAck, error) {
+	ctx, span := tracer.Start(ctx, "grpc_closing")
+	defer span.End()
+	host := req.GetHost()
+	span.SetAttributes(
+		attribute.String("component", "controlplane"),
+		attribute.String("host", host),
+	)
+	logger.InfoContext(ctx, "closing notice", "host", host)
+	closingCalls.Add(ctx, 1, metric.WithAttributes(attribute.String("host", host)))
+
+	if host != "" {
+		s.pool.RemoveHost(host)
+	}
+	return &messages.OwnerChangeAck{
+		Accepted: true,
+		Message:  "removed host",
+	}, nil
+}
+
+type ServerConfig struct {
+	Addr    string
+	Options []grpc.ServerOption
+}
+
+func NewServerConfig(addr string, options ...grpc.ServerOption) ServerConfig {
+	return ServerConfig{
+		Addr:    addr,
+		Options: options,
+	}
+}
+
+func DefaultServerConfig() ServerConfig {
+	return NewServerConfig(":1337")
+}
+
+// StartGRPCServer configures and starts the unified gRPC server on the given address.
+// It registers both the CartActor and ControlPlane services.
+func NewControlServer[V any](config ServerConfig, pool GrainPool[V]) (*grpc.Server, error) {
+	lis, err := net.Listen("tcp", config.Addr)
+	if err != nil {
+		return nil, fmt.Errorf("failed to listen: %w", err)
+	}
+
+	grpcServer := grpc.NewServer(config.Options...)
+	server := &ControlServer[V]{
+		pool: pool,
+	}
+
+	messages.RegisterControlPlaneServer(grpcServer, server)
+	reflection.Register(grpcServer)
+
+	log.Printf("gRPC server listening as %s on %s", pool.Hostname(), config.Addr)
+	go func() {
+		if err := grpcServer.Serve(lis); err != nil {
+			log.Fatalf("failed to serve gRPC: %v", err)
+		}
+	}()
+
+	return grpcServer, nil
+}

pkg/actor/grpc_server_test.go

@@ -0,0 +1,150 @@
+package actor
+
+import (
+	"context"
+	"testing"
+
+	cart_messages "git.k6n.net/go-cart-actor/proto/cart"
+	control_plane_messages "git.k6n.net/go-cart-actor/proto/control"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/known/anypb"
+)
+
+// MockGrainPool for testing
+type mockGrainPool struct {
+	applied []proto.Message
+}
+
+func (m *mockGrainPool) Apply(ctx context.Context, id uint64, mutations ...proto.Message) (*MutationResult[mockGrain], error) {
+	m.applied = mutations
+	// Simulate successful application
+	return &MutationResult[mockGrain]{
+		Result: mockGrain{},
+		Mutations: []ApplyResult{
+			{Type: "AddItem", Mutation: &cart_messages.AddItem{ItemId: 1, Quantity: 2}, Error: nil},
+			{Type: "RemoveItem", Mutation: &cart_messages.RemoveItem{Id: 1}, Error: nil},
+		},
+	}, nil
+}
+
+func (m *mockGrainPool) Get(ctx context.Context, id uint64) (*mockGrain, error) {
+	return &mockGrain{}, nil
+}
+
+func (m *mockGrainPool) OwnerHost(id uint64) (Host[mockGrain], bool) {
+	return nil, false
+}
+
+func (m *mockGrainPool) TakeOwnership(id uint64) {}
+
+func (m *mockGrainPool) Hostname() string { return "test-host" }
+
+func (m *mockGrainPool) HandleOwnershipChange(host string, ids []uint64) error { return nil }
+func (m *mockGrainPool) HandleRemoteExpiry(host string, ids []uint64) error    { return nil }
+func (m *mockGrainPool) Negotiate(hosts []string)                              {}
+func (m *mockGrainPool) GetLocalIds() []uint64                                 { return []uint64{} }
+func (m *mockGrainPool) RemoveHost(host string)                                {}
+func (m *mockGrainPool) AddRemoteHost(host string)                             {}
+func (m *mockGrainPool) IsHealthy() bool                                       { return true }
+func (m *mockGrainPool) IsKnown(host string) bool                              { return false }
+func (m *mockGrainPool) Close()                                                {}
+
+type mockGrain struct{}
+
+func TestApplyRequestWithMutations(t *testing.T) {
+	// Setup mock pool
+	pool := &mockGrainPool{}
+
+	// Create gRPC server
+	server, err := NewControlServer[mockGrain](DefaultServerConfig(), pool)
+	if err != nil {
+		t.Fatalf("failed to create server: %v", err)
+	}
+	defer server.GracefulStop()
+
+	// Create client connection
+	conn, err := grpc.Dial("localhost:1337", grpc.WithTransportCredentials(insecure.NewCredentials()))
+	if err != nil {
+		t.Fatalf("failed to dial: %v", err)
+	}
+	defer conn.Close()
+
+	client := control_plane_messages.NewControlPlaneClient(conn)
+
+	// Prepare ApplyRequest with multiple Any messages
+	addItemAny, _ := anypb.New(&cart_messages.AddItem{ItemId: 1, Quantity: 2})
+	removeItemAny, _ := anypb.New(&cart_messages.RemoveItem{Id: 1})
+	req := &control_plane_messages.ApplyRequest{
+		Id:       123,
+		Messages: []*anypb.Any{addItemAny, removeItemAny},
+	}
+
+	// Call Apply
+	resp, err := client.Apply(context.Background(), req)
+	if err != nil {
+		t.Fatalf("Apply failed: %v", err)
+	}
+
+	// Verify response
+	if resp.State == nil {
+		t.Errorf("expected State to be non-nil")
+	}
+	if len(resp.Mutations) != 2 {
+		t.Errorf("expected 2 mutation results, got %d", len(resp.Mutations))
+	}
+	for i, mut := range resp.Mutations {
+		if mut.Error != nil {
+			t.Errorf("expected no error in mutation %d, got %s", i, *mut.Error)
+		}
+	}
+
+	// Verify mutations were extracted and applied
+	if len(pool.applied) != 2 {
+		t.Errorf("expected 2 mutations applied, got %d", len(pool.applied))
+	}
+	if addItem, ok := pool.applied[0].(*cart_messages.AddItem); !ok || addItem.ItemId != 1 {
+		t.Errorf("expected AddItem with ItemId=1, got %v", pool.applied[0])
+	}
+	if removeItem, ok := pool.applied[1].(*cart_messages.RemoveItem); !ok || removeItem.Id != 1 {
+		t.Errorf("expected RemoveItem with Id=1, got %v", pool.applied[1])
+	}
+}
+
+func TestGetRequest(t *testing.T) {
+	// Setup mock pool
+	pool := &mockGrainPool{}
+
+	// Create gRPC server
+	server, err := NewControlServer[mockGrain](DefaultServerConfig(), pool)
+	if err != nil {
+		t.Fatalf("failed to create server: %v", err)
+	}
+	defer server.GracefulStop()
+
+	// Create client connection
+	conn, err := grpc.Dial("localhost:1337", grpc.WithTransportCredentials(insecure.NewCredentials()))
+	if err != nil {
+		t.Fatalf("failed to dial: %v", err)
+	}
+	defer conn.Close()
+
+	client := control_plane_messages.NewControlPlaneClient(conn)
+
+	// Prepare GetRequest
+	req := &control_plane_messages.GetRequest{
+		Id: 123,
+	}
+
+	// Call Get
+	resp, err := client.Get(context.Background(), req)
+	if err != nil {
+		t.Fatalf("Get failed: %v", err)
+	}
+
+	// Verify response
+	if resp.Grain == nil {
+		t.Errorf("expected Grain to be non-nil")
+	}
+}

pkg/actor/log_listerner.go

@@ -0,0 +1,47 @@
+package actor
+
+import (
+	"log"
+
+	"github.com/matst80/slask-finder/pkg/messaging"
+	amqp "github.com/rabbitmq/amqp091-go"
+)
+
+type LogListener interface {
+	AppendMutations(id uint64, msg ...ApplyResult)
+}
+
+type AmqpListener struct {
+	conn        *amqp.Connection
+	transformer func(id uint64, msg []ApplyResult) (any, error)
+}
+
+func NewAmqpListener(conn *amqp.Connection, transformer func(id uint64, msg []ApplyResult) (any, error)) *AmqpListener {
+	return &AmqpListener{
+		conn:        conn,
+		transformer: transformer,
+	}
+}
+
+func (l *AmqpListener) DefineTopics() {
+	ch, err := l.conn.Channel()
+	if err != nil {
+		log.Fatalf("Failed to open a channel: %v", err)
+	}
+	defer ch.Close()
+	if err := messaging.DefineTopic(ch, "cart", "mutation"); err != nil {
+		log.Fatalf("Failed to declare topic mutation: %v", err)
+	}
+}
+
+func (l *AmqpListener) AppendMutations(id uint64, msg ...ApplyResult) {
+	data, err := l.transformer(id, msg)
+	if err != nil {
+		log.Printf("Failed to transform mutation event: %v", err)
+		return
+	}
+	err = messaging.SendChange(l.conn, "cart", "mutation", data)
+	if err != nil {
+		log.Printf("Failed to send mutation event: %v", err)
+	}
+}

pkg/actor/mutation_registry.go

@@ -0,0 +1,361 @@
+package actor
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"reflect"
+	"sync"
+
+	"go.opentelemetry.io/otel/attribute"
+	"google.golang.org/protobuf/proto"
+)
+
+type ApplyResult struct {
+	Type     string        `json:"type"`
+	Mutation proto.Message `json:"mutation"`
+	Error    error         `json:"error,omitempty"`
+}
+
+type MutationProcessor interface {
+	Process(ctx context.Context, grain any) error
+}
+
+type BasicMutationProcessor[V any] struct {
+	processor func(ctx context.Context, grain V) error
+}
+
+func NewMutationProcessor[V any](process func(ctx context.Context, grain V) error) MutationProcessor {
+	return &BasicMutationProcessor[V]{
+		processor: process,
+	}
+}
+
+func (p *BasicMutationProcessor[V]) Process(ctx context.Context, grain any) error {
+	return p.processor(ctx, grain.(V))
+}
+
+type MutationRegistry interface {
+	Apply(ctx context.Context, grain any, msg ...proto.Message) ([]ApplyResult, error)
+	RegisterMutations(handlers ...MutationHandler)
+	Create(typeName string) (proto.Message, bool)
+	GetTypeName(msg proto.Message) (string, bool)
+	RegisterProcessor(processor ...MutationProcessor)
+	RegisterTrigger(trigger ...TriggerHandler)
+	SetEventChannel(ch chan<- ApplyResult)
+}
+
+type ProtoMutationRegistry struct {
+	mutationRegistryMu sync.RWMutex
+	mutationRegistry   map[reflect.Type]MutationHandler
+	triggers           map[reflect.Type][]TriggerHandler
+	processors         []MutationProcessor
+	eventChannel       chan<- ApplyResult
+}
+
+var (
+	ErrMutationNotRegistered = &MutationError{
+		Message:    "mutation not registered",
+		Code:       255,
+		StatusCode: 500,
+	}
+)
+
+type MutationError struct {
+	Message    string `json:"message"`
+	Code       uint32 `json:"code"`
+	StatusCode uint32 `json:"status_code"`
+}
+
+func (m MutationError) Error() string {
+	return m.Message
+}
+
+// MutationOption configures additional behavior for a registered mutation.
+type MutationOption func(*mutationOptions)
+
+// mutationOptions holds flags adjustable per registration.
+type mutationOptions struct {
+	updateTotals bool
+}
+
+// WithTotals ensures CartGrain.UpdateTotals() is called after a successful handler.
+func WithTotals() MutationOption {
+	return func(o *mutationOptions) {
+		o.updateTotals = true
+	}
+}
+
+type TriggerHandler interface {
+	Handle(state any, msg proto.Message) []proto.Message
+	Name() string
+	Type() reflect.Type
+}
+
+type RegisteredTrigger[V any, I proto.Message] struct {
+	name    string
+	handler func(state any, msg proto.Message) []proto.Message
+	msgType reflect.Type
+}
+
+func NewTrigger[V any, I proto.Message](name string, handler func(state any, msg proto.Message) []proto.Message) *RegisteredTrigger[V, I] {
+	return &RegisteredTrigger[V, I]{
+		name:    name,
+		handler: handler,
+		msgType: reflect.TypeOf((*I)(nil)).Elem(),
+	}
+}
+
+type MutationHandler interface {
+	Handle(state any, msg proto.Message) error
+	Name() string
+	Type() reflect.Type
+	Create() proto.Message
+}
+
+// RegisteredMutation stores metadata + the execution closure.
+type RegisteredMutation[V any, T proto.Message] struct {
+	name    string
+	handler func(*V, T) error
+	create  func() proto.Message
+	msgType reflect.Type
+}
+
+func NewMutation[V any, T proto.Message](handler func(*V, T) error) *RegisteredMutation[V, T] {
+	// Derive the name and message type from a concrete instance produced by create().
+	// This avoids relying on reflect.TypeFor (which can yield unexpected results in some toolchains)
+	// and ensures we always peel off the pointer layer for proto messages.
+	create := func() proto.Message {
+		var t T
+		rt := reflect.TypeOf(t)
+		if rt != nil && rt.Kind() == reflect.Pointer {
+			return reflect.New(rt.Elem()).Interface().(proto.Message)
+		}
+		log.Fatalf("expected to create proto message got %+v", rt)
+		return nil
+	}
+	instance := create()
+	rt := reflect.TypeOf(instance)
+	if rt.Kind() == reflect.Pointer {
+		rt = rt.Elem()
+	}
+	return &RegisteredMutation[V, T]{
+		name:    rt.Name(),
+		handler: handler,
+		create:  create,
+		msgType: rt,
+	}
+}
+
+func (m *RegisteredMutation[V, T]) Handle(state any, msg proto.Message) error {
+	return m.handler(state.(*V), msg.(T))
+}
+
+func (m *RegisteredMutation[V, T]) Name() string {
+	return m.name
+}
+
+func (m *RegisteredMutation[V, T]) Create() proto.Message {
+	return m.create()
+}
+
+func (m *RegisteredMutation[V, T]) Type() reflect.Type {
+	return m.msgType
+}
+
+func NewMutationRegistry() MutationRegistry {
+	return &ProtoMutationRegistry{
+		mutationRegistry:   make(map[reflect.Type]MutationHandler),
+		mutationRegistryMu: sync.RWMutex{},
+		triggers:           make(map[reflect.Type][]TriggerHandler),
+		processors:         make([]MutationProcessor, 0),
+	}
+}
+
+func (r *ProtoMutationRegistry) RegisterProcessor(processors ...MutationProcessor) {
+	r.processors = append(r.processors, processors...)
+}
+
+func (r *ProtoMutationRegistry) RegisterMutations(handlers ...MutationHandler) {
+	r.mutationRegistryMu.Lock()
+	defer r.mutationRegistryMu.Unlock()
+
+	for _, handler := range handlers {
+		r.mutationRegistry[handler.Type()] = handler
+	}
+}
+
+func (r *ProtoMutationRegistry) RegisterTrigger(triggers ...TriggerHandler) {
+	r.mutationRegistryMu.Lock()
+	defer r.mutationRegistryMu.Unlock()
+
+	for _, trigger := range triggers {
+		existingTriggers, ok := r.triggers[trigger.Type()]
+		if !ok {
+			r.triggers[trigger.Type()] = []TriggerHandler{trigger}
+		} else {
+			r.triggers[trigger.Type()] = append(existingTriggers, trigger)
+		}
+	}
+}
+
+func (r *ProtoMutationRegistry) SetEventChannel(ch chan<- ApplyResult) {
+	r.eventChannel = ch
+}
+
+func (r *ProtoMutationRegistry) GetTypeName(msg proto.Message) (string, bool) {
+	r.mutationRegistryMu.RLock()
+	defer r.mutationRegistryMu.RUnlock()
+
+	rt := indirectType(reflect.TypeOf(msg))
+	if handler, ok := r.mutationRegistry[rt]; ok {
+		return handler.Name(), true
+	}
+	return "", false
+}
+
+func (r *ProtoMutationRegistry) getHandler(typeName string) MutationHandler {
+	r.mutationRegistryMu.Lock()
+	defer r.mutationRegistryMu.Unlock()
+
+	for _, handler := range r.mutationRegistry {
+		if handler.Name() == typeName {
+			return handler
+		}
+	}
+
+	return nil
+}
+
+func (r *ProtoMutationRegistry) Create(typeName string) (proto.Message, bool) {
+
+	handler := r.getHandler(typeName)
+	if handler == nil {
+		log.Printf("missing handler for %s", typeName)
+		return nil, false
+	}
+
+	return handler.Create(), true
+}
+
+// ApplyRegistered attempts to apply a registered mutation.
+// Returns updated grain if successful.
+//
+// If the mutation is not registered, returns (nil, ErrMutationNotRegistered).
+func (r *ProtoMutationRegistry) Apply(ctx context.Context, grain any, msg ...proto.Message) ([]ApplyResult, error) {
+
+	parentCtx, span := tracer.Start(ctx, "apply mutations")
+	defer span.End()
+	span.SetAttributes(
+		attribute.String("component", "registry"),
+		attribute.Int("mutations", len(msg)),
+	)
+
+	results := make([]ApplyResult, 0, len(msg))
+
+	if grain == nil {
+		return results, fmt.Errorf("nil grain")
+	}
+	// Nil slice of mutations still treated as an error (call contract violation).
+	if msg == nil {
+		return results, fmt.Errorf("nil mutation message")
+	}
+
+	for _, m := range msg {
+		// Error if any mutation element is nil.
+		if m == nil {
+			return results, fmt.Errorf("nil mutation message")
+		}
+		// Typed nil: interface holds concrete proto message type whose pointer value is nil.
+		rv := reflect.ValueOf(m)
+		if rv.Kind() == reflect.Pointer && rv.IsNil() {
+			continue
+		}
+		rt := indirectType(reflect.TypeOf(m))
+		_, msgSpan := tracer.Start(parentCtx, rt.Name())
+
+		r.mutationRegistryMu.RLock()
+		entry, ok := r.mutationRegistry[rt]
+		r.mutationRegistryMu.RUnlock()
+		if !ok {
+			results = append(results, ApplyResult{Error: ErrMutationNotRegistered, Type: rt.Name(), Mutation: m})
+			continue
+		} else {
+			err := entry.Handle(grain, m)
+			if err != nil {
+				msgSpan.RecordError(err)
+			}
+			if r.eventChannel != nil {
+				go func() {
+					defer func() {
+						if r := recover(); r != nil {
+							// Handle panic from sending to closed channel
+							log.Printf("event channel closed: %v", r)
+						}
+					}()
+					for _, tr := range r.triggers[rt] {
+						for _, msg := range tr.Handle(grain, m) {
+							select {
+							case r.eventChannel <- msg:
+							default:
+								// Channel full or no receiver, skip to avoid blocking
+							}
+						}
+					}
+				}()
+			}
+			results = append(results, ApplyResult{Error: err, Type: rt.Name(), Mutation: m})
+		}
+		msgSpan.End()
+	}
+
+	if len(results) > 0 {
+		processCtx, processSpan := tracer.Start(ctx, "after mutation processors")
+		defer processSpan.End()
+		for _, processor := range r.processors {
+
+			err := processor.Process(processCtx, grain)
+			if err != nil {
+				return results, err
+			}
+		}
+	}
+	// Return error for unregistered mutations
+	for _, res := range results {
+		if res.Error == ErrMutationNotRegistered {
+			return results, res.Error
+		}
+	}
+
+	return results, nil
+}
+
+// RegisteredMutations returns metadata for all registered mutations (snapshot).
+func (r *ProtoMutationRegistry) RegisteredMutations() []string {
+	r.mutationRegistryMu.RLock()
+	defer r.mutationRegistryMu.RUnlock()
+	out := make([]string, 0, len(r.mutationRegistry))
+	for _, entry := range r.mutationRegistry {
+		out = append(out, entry.Name())
+	}
+	return out
+}
+
+// RegisteredMutationTypes returns the reflect.Type list of all registered messages.
+// Useful for coverage tests ensuring expected set matches actual set.
+func (r *ProtoMutationRegistry) RegisteredMutationTypes() []reflect.Type {
+	r.mutationRegistryMu.RLock()
+	defer r.mutationRegistryMu.RUnlock()
+	out := make([]reflect.Type, 0, len(r.mutationRegistry))
+	for _, entry := range r.mutationRegistry {
+		out = append(out, entry.Type())
+	}
+	return out
+}
+
+func indirectType(t reflect.Type) reflect.Type {
+	for t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	return t
+}

pkg/actor/mutation_registry_test.go

@@ -0,0 +1,207 @@
+package actor
+
+import (
+	"context"
+	"reflect"
+	"slices"
+	"testing"
+	"time"
+
+	cart_messages "git.k6n.net/go-cart-actor/proto/cart"
+)
+
+type cartState struct {
+	calls     int
+	lastAdded *cart_messages.AddItem
+}
+
+func TestRegisteredMutationBasics(t *testing.T) {
+	reg := NewMutationRegistry().(*ProtoMutationRegistry)
+
+	addItemMutation := NewMutation(
+		func(state *cartState, msg *cart_messages.AddItem) error {
+			state.calls++
+			// copy to avoid external mutation side-effects (not strictly necessary for the test)
+			cp := msg
+			state.lastAdded = cp
+			return nil
+		},
+	)
+
+	// Sanity check on mutation metadata
+	if addItemMutation.Name() != "AddItem" {
+		t.Fatalf("expected mutation Name() == AddItem, got %s", addItemMutation.Name())
+	}
+	if got, want := addItemMutation.Type(), reflect.TypeOf(cart_messages.AddItem{}); got != want {
+		t.Fatalf("expected Type() == %v, got %v", want, got)
+	}
+
+	reg.RegisterMutations(addItemMutation)
+
+	// RegisteredMutations: membership (order not guaranteed)
+	names := reg.RegisteredMutations()
+	if !slices.Contains(names, "AddItem") {
+		t.Fatalf("RegisteredMutations missing AddItem, got %v", names)
+	}
+
+	// RegisteredMutationTypes: membership (order not guaranteed)
+	types := reg.RegisteredMutationTypes()
+	if !slices.Contains(types, reflect.TypeOf(cart_messages.AddItem{})) {
+		t.Fatalf("RegisteredMutationTypes missing AddItem type, got %v", types)
+	}
+
+	// GetTypeName should resolve for a pointer instance
+	name, ok := reg.GetTypeName(&cart_messages.AddItem{})
+	if !ok || name != "AddItem" {
+		t.Fatalf("GetTypeName returned (%q,%v), expected (AddItem,true)", name, ok)
+	}
+
+	// GetTypeName should fail for unregistered type
+	if name, ok := reg.GetTypeName(&cart_messages.RemoveItem{}); ok || name != "" {
+		t.Fatalf("expected GetTypeName to fail for unregistered message, got (%q,%v)", name, ok)
+	}
+
+	// Create by name
+	msg, ok := reg.Create("AddItem")
+	if !ok {
+		t.Fatalf("Create failed for registered mutation")
+	}
+	if _, isAddItem := msg.(*cart_messages.AddItem); !isAddItem {
+		t.Fatalf("Create returned wrong concrete type: %T", msg)
+	}
+
+	// Create unknown
+	if m2, ok := reg.Create("Unknown"); ok || m2 != nil {
+		t.Fatalf("Create should fail for unknown mutation, got (%T,%v)", m2, ok)
+	}
+
+	// Apply happy path
+	state := &cartState{}
+	add := &cart_messages.AddItem{ItemId: 42, Quantity: 3, Sku: "ABC"}
+	if _, err := reg.Apply(context.Background(), state, add); err != nil {
+		t.Fatalf("Apply returned error: %v", err)
+	}
+	if state.calls != 1 {
+		t.Fatalf("handler not invoked expected calls=1 got=%d", state.calls)
+	}
+	if state.lastAdded == nil || state.lastAdded.ItemId != 42 || state.lastAdded.Quantity != 3 {
+		t.Fatalf("state not updated correctly: %+v", state.lastAdded)
+	}
+
+	// Apply nil grain
+	if _, err := reg.Apply(context.Background(), nil, add); err == nil {
+		t.Fatalf("expected error for nil grain")
+	}
+
+	// Apply nil message
+	if _, err := reg.Apply(context.Background(), state, nil); err == nil {
+		t.Fatalf("expected error for nil mutation message")
+	}
+
+	// Apply unregistered message
+	_, err := reg.Apply(context.Background(), state, &cart_messages.RemoveItem{})
+	if err != ErrMutationNotRegistered {
+		t.Fatalf("expected ErrMutationNotRegistered, got %v", err)
+	}
+}
+
+func TestEventChannel(t *testing.T) {
+	reg := NewMutationRegistry().(*ProtoMutationRegistry)
+
+	addItemMutation := NewMutation(
+		func(state *cartState, msg *cart_messages.AddItem) error {
+			state.calls++
+			return nil
+		},
+	)
+
+	reg.RegisterMutations(addItemMutation)
+
+	eventCh := make(chan ApplyResult, 10)
+	reg.SetEventChannel(eventCh)
+
+	state := &cartState{}
+	add := &cart_messages.AddItem{ItemId: 42, Quantity: 3, Sku: "ABC"}
+	results, err := reg.Apply(context.Background(), state, add)
+	if err != nil {
+		t.Fatalf("Apply returned error: %v", err)
+	}
+	if len(results) != 1 {
+		t.Fatalf("expected 1 result, got %d", len(results))
+	}
+
+	// Receive from channel with timeout
+	select {
+	case res := <-eventCh:
+		if res.Type != "AddItem" {
+			t.Fatalf("expected type AddItem, got %s", res.Type)
+		}
+		if res.Error != nil {
+			t.Fatalf("expected no error, got %v", res.Error)
+		}
+	case <-time.After(time.Second):
+		t.Fatalf("expected to receive event on channel within timeout")
+	}
+}
+
+func TestEventChannelClosed(t *testing.T) {
+	reg := NewMutationRegistry().(*ProtoMutationRegistry)
+
+	addItemMutation := NewMutation(
+		func(state *cartState, msg *cart_messages.AddItem) error {
+			state.calls++
+			return nil
+		},
+	)
+
+	reg.RegisterMutations(addItemMutation)
+
+	eventCh := make(chan ApplyResult, 10)
+	reg.SetEventChannel(eventCh)
+
+	close(eventCh) // Close the channel to simulate external close
+
+	state := &cartState{}
+	add := &cart_messages.AddItem{ItemId: 42, Quantity: 3, Sku: "ABC"}
+	// This should not panic due to recover in goroutine
+	results, err := reg.Apply(context.Background(), state, add)
+	if err != nil {
+		t.Fatalf("Apply returned error: %v", err)
+	}
+	if len(results) != 1 {
+		t.Fatalf("expected 1 result, got %d", len(results))
+	}
+	// Test passes if no panic occurs
+}
+
+func TestEventChannelUnbufferedNoListener(t *testing.T) {
+	reg := NewMutationRegistry().(*ProtoMutationRegistry)
+
+	addItemMutation := NewMutation(
+		func(state *cartState, msg *cart_messages.AddItem) error {
+			state.calls++
+			return nil
+		},
+	)
+
+	reg.RegisterMutations(addItemMutation)
+
+	eventCh := make(chan ApplyResult) // unbuffered
+	reg.SetEventChannel(eventCh)
+
+	// No goroutine reading from eventCh
+
+	state := &cartState{}
+	add := &cart_messages.AddItem{ItemId: 42, Quantity: 3, Sku: "ABC"}
+	results, err := reg.Apply(context.Background(), state, add)
+	if err != nil {
+		t.Fatalf("Apply returned error: %v", err)
+	}
+	if len(results) != 1 {
+		t.Fatalf("expected 1 result, got %d", len(results))
+	}
+	// Since no listener, the send should go to default and not block
+	// Test passes if Apply completes without hanging
+}
+
+// Helpers

pkg/actor/pubsub.go

@@ -0,0 +1,78 @@
+package actor
+
+import (
+	"iter"
+	"slices"
+	"sync"
+)
+
+type ReceiverFunc[V any] func(event V)
+
+type PubSub[V any] struct {
+	subscribers []*ReceiverFunc[V]
+	mu          sync.RWMutex
+}
+
+// NewPubSub creates a new PubSub instance.
+func NewPubSub[V any]() *PubSub[V] {
+	return &PubSub[V]{
+		subscribers: make([]*ReceiverFunc[V], 0),
+	}
+}
+
+// Subscribe adds a grain ID to the subscribers of a topic.
+func (p *PubSub[V]) Subscribe(receiver ReceiverFunc[V]) {
+	if receiver == nil {
+		return
+	}
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	// log.Printf("adding subscriber")
+	p.subscribers = append(p.subscribers, &receiver)
+}
+
+// Unsubscribe removes a grain ID from the subscribers of a topic.
+func (p *PubSub[V]) Unsubscribe(receiver ReceiverFunc[V]) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	list := p.subscribers
+	prt := &receiver
+	for i, sub := range list {
+		if sub == nil {
+			continue
+		}
+		if sub == prt {
+			// log.Printf("removing subscriber")
+			p.subscribers = append(list[:i], list[i+1:]...)
+			break
+		}
+	}
+	p.subscribers = slices.DeleteFunc(p.subscribers, func(fn *ReceiverFunc[V]) bool {
+		return fn == nil
+	})
+	// If list is empty, could delete, but not necessary
+}
+
+// GetSubscribers returns a copy of the subscriber IDs for a topic.
+func (p *PubSub[V]) GetSubscribers() iter.Seq[ReceiverFunc[V]] {
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+
+	return func(yield func(ReceiverFunc[V]) bool) {
+		for _, sub := range p.subscribers {
+			if sub == nil {
+				continue
+			}
+			if !yield(*sub) {
+				return
+			}
+		}
+	}
+}
+
+// Publish sends an event to all subscribers of the topic.
+func (p *PubSub[V]) Publish(event V) {
+	for notify := range p.GetSubscribers() {
+		notify(event)
+	}
+}

pkg/actor/simple_grain_pool.go

@@ -0,0 +1,462 @@
+package actor
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"maps"
+	"sync"
+	"time"
+
+	"google.golang.org/protobuf/proto"
+)
+
+type SimpleGrainPool[V any] struct {
+	// fields and methods
+	localMu          sync.RWMutex
+	grains           map[uint64]Grain[V]
+	mutationRegistry MutationRegistry
+	spawn            func(ctx context.Context, id uint64) (Grain[V], error)
+	destroy          func(grain Grain[V]) error
+	spawnHost        func(host string) (Host[V], error)
+	listeners        []LogListener
+	storage          LogStorage[V]
+	ttl              time.Duration
+	poolSize         int
+
+	// Cluster coordination --------------------------------------------------
+	hostname     string
+	remoteMu     sync.RWMutex
+	remoteOwners map[uint64]Host[V]
+	remoteHosts  map[string]Host[V]
+	//discardedHostHandler *DiscardedHostHandler
+
+	// House-keeping ---------------------------------------------------------
+	purgeTicker *time.Ticker
+}
+
+type GrainPoolConfig[V any] struct {
+	Hostname         string
+	Spawn            func(ctx context.Context, id uint64) (Grain[V], error)
+	SpawnHost        func(host string) (Host[V], error)
+	Destroy          func(grain Grain[V]) error
+	TTL              time.Duration
+	PoolSize         int
+	MutationRegistry MutationRegistry
+	Storage          LogStorage[V]
+}
+
+func NewSimpleGrainPool[V any](config GrainPoolConfig[V]) (*SimpleGrainPool[V], error) {
+	p := &SimpleGrainPool[V]{
+		grains:           make(map[uint64]Grain[V]),
+		mutationRegistry: config.MutationRegistry,
+		storage:          config.Storage,
+		spawn:            config.Spawn,
+		spawnHost:        config.SpawnHost,
+		destroy:          config.Destroy,
+		ttl:              config.TTL,
+		poolSize:         config.PoolSize,
+		hostname:         config.Hostname,
+		remoteOwners:     make(map[uint64]Host[V]),
+		remoteHosts:      make(map[string]Host[V]),
+	}
+
+	p.purgeTicker = time.NewTicker(time.Minute)
+	go func() {
+		for range p.purgeTicker.C {
+			p.purge()
+		}
+	}()
+
+	return p, nil
+}
+
+func (p *SimpleGrainPool[V]) AddListener(listener LogListener) {
+	p.listeners = append(p.listeners, listener)
+}
+
+func (p *SimpleGrainPool[V]) RemoveListener(listener LogListener) {
+	for i, l := range p.listeners {
+		if l == listener {
+			p.listeners = append(p.listeners[:i], p.listeners[i+1:]...)
+			break
+		}
+	}
+}
+
+func (p *SimpleGrainPool[V]) purge() {
+	purgeLimit := time.Now().Add(-p.ttl)
+	purgedIds := make([]uint64, 0, len(p.grains))
+	p.localMu.Lock()
+	for id, grain := range p.grains {
+		if grain.GetLastAccess().Before(purgeLimit) {
+			purgedIds = append(purgedIds, id)
+			if err := p.destroy(grain); err != nil {
+				log.Printf("failed to destroy grain %d: %v", id, err)
+			}
+
+			delete(p.grains, id)
+		}
+	}
+	p.localMu.Unlock()
+	p.forAllHosts(func(remote Host[V]) {
+		remote.AnnounceExpiry(purgedIds)
+	})
+
+}
+
+// LocalUsage returns the number of resident grains and configured capacity.
+func (p *SimpleGrainPool[V]) LocalUsage() (int, int) {
+	p.localMu.RLock()
+	defer p.localMu.RUnlock()
+	return len(p.grains), p.poolSize
+}
+
+// LocalCartIDs returns the currently owned cart ids (for control-plane RPCs).
+func (p *SimpleGrainPool[V]) GetLocalIds() []uint64 {
+	p.localMu.RLock()
+	defer p.localMu.RUnlock()
+	ids := make([]uint64, 0, len(p.grains))
+	for _, g := range p.grains {
+		if g == nil {
+			continue
+		}
+		ids = append(ids, uint64(g.GetId()))
+	}
+	return ids
+}
+
+func (p *SimpleGrainPool[V]) HandleRemoteExpiry(host string, ids []uint64) error {
+	p.remoteMu.Lock()
+	defer p.remoteMu.Unlock()
+	for _, id := range ids {
+		delete(p.remoteOwners, id)
+	}
+	return nil
+}
+
+func (p *SimpleGrainPool[V]) HandleOwnershipChange(host string, ids []uint64) error {
+	p.remoteMu.RLock()
+	remoteHost, exists := p.remoteHosts[host]
+	p.remoteMu.RUnlock()
+	if !exists {
+		createdHost, err := p.AddRemote(host)
+		if err != nil {
+			return err
+		}
+		remoteHost = createdHost
+	}
+	p.remoteMu.Lock()
+	defer p.remoteMu.Unlock()
+	p.localMu.Lock()
+	defer p.localMu.Unlock()
+	for _, id := range ids {
+		log.Printf("Handling ownership change for cart %d to host %s", id, host)
+		delete(p.grains, id)
+		p.remoteOwners[id] = remoteHost
+	}
+	return nil
+}
+
+// TakeOwnership takes ownership of a grain.
+func (p *SimpleGrainPool[V]) TakeOwnership(id uint64) {
+	p.broadcastOwnership([]uint64{id})
+}
+
+func (p *SimpleGrainPool[V]) AddRemoteHost(host string) {
+	p.AddRemote(host)
+}
+
+func (p *SimpleGrainPool[V]) AddRemote(host string) (Host[V], error) {
+	if host == "" {
+		return nil, fmt.Errorf("host is empty")
+	}
+	if host == p.hostname {
+		return nil, fmt.Errorf("same host, this should not happen")
+	}
+	p.remoteMu.RLock()
+	existing, found := p.remoteHosts[host]
+	p.remoteMu.RUnlock()
+	if found {
+		return existing, nil
+	}
+
+	remote, err := p.spawnHost(host)
+	if err != nil {
+		log.Printf("AddRemote %s failed: %v", host, err)
+
+		return nil, err
+	}
+	p.remoteMu.Lock()
+	p.remoteHosts[host] = remote
+	p.remoteMu.Unlock()
+	// connectedRemotes.Set(float64(p.RemoteCount()))
+
+	log.Printf("Connected to remote host %s", host)
+	go p.pingLoop(remote)
+	go p.initializeRemote(remote)
+	go p.SendNegotiation()
+	return remote, nil
+}
+
+func (p *SimpleGrainPool[V]) initializeRemote(remote Host[V]) {
+
+	remotesIds := remote.GetActorIds()
+
+	p.remoteMu.Lock()
+	for _, id := range remotesIds {
+		p.localMu.Lock()
+		delete(p.grains, id)
+		p.localMu.Unlock()
+		if _, exists := p.remoteOwners[id]; !exists {
+			p.remoteOwners[id] = remote
+		}
+	}
+	p.remoteMu.Unlock()
+
+}
+
+func (p *SimpleGrainPool[V]) RemoveHost(host string) {
+	p.remoteMu.Lock()
+	remote, exists := p.remoteHosts[host]
+
+	if exists {
+		go remote.Close()
+		delete(p.remoteHosts, host)
+	}
+	count := 0
+	for id, owner := range p.remoteOwners {
+		if owner.Name() == host {
+			count++
+			delete(p.remoteOwners, id)
+		}
+	}
+	log.Printf("Removing host %s, grains: %d", host, count)
+	p.remoteMu.Unlock()
+
+	if exists {
+		remote.Close()
+	}
+	// connectedRemotes.Set(float64(p.RemoteCount()))
+}
+
+func (p *SimpleGrainPool[V]) RemoteCount() int {
+	p.remoteMu.RLock()
+	defer p.remoteMu.RUnlock()
+	return len(p.remoteHosts)
+}
+
+// RemoteHostNames returns a snapshot of connected remote host identifiers.
+func (p *SimpleGrainPool[V]) RemoteHostNames() []string {
+	p.remoteMu.RLock()
+	defer p.remoteMu.RUnlock()
+	hosts := make([]string, 0, len(p.remoteHosts))
+	for host := range p.remoteHosts {
+		hosts = append(hosts, host)
+	}
+	return hosts
+}
+
+func (p *SimpleGrainPool[V]) IsKnown(host string) bool {
+	if host == p.hostname {
+		return true
+	}
+	p.remoteMu.RLock()
+	defer p.remoteMu.RUnlock()
+	_, ok := p.remoteHosts[host]
+	return ok
+}
+
+func (p *SimpleGrainPool[V]) pingLoop(remote Host[V]) {
+	remote.Ping()
+	ticker := time.NewTicker(5 * time.Second)
+	defer ticker.Stop()
+	for range ticker.C {
+		if !remote.Ping() {
+			if !remote.IsHealthy() {
+				log.Printf("Remote %s unhealthy, removing", remote.Name())
+				p.Close()
+				p.RemoveHost(remote.Name())
+				return
+			}
+			continue
+		}
+	}
+}
+
+func (p *SimpleGrainPool[V]) IsHealthy() bool {
+	p.remoteMu.RLock()
+	defer p.remoteMu.RUnlock()
+	for _, r := range p.remoteHosts {
+		if !r.IsHealthy() {
+			return false
+		}
+	}
+	return true
+}
+
+func (p *SimpleGrainPool[V]) Negotiate(otherHosts []string) {
+
+	for _, host := range otherHosts {
+		if host != p.hostname {
+			p.remoteMu.RLock()
+			_, ok := p.remoteHosts[host]
+			p.remoteMu.RUnlock()
+			if !ok {
+				go p.AddRemote(host)
+			}
+		}
+	}
+}
+
+func (p *SimpleGrainPool[V]) SendNegotiation() {
+	//negotiationCount.Inc()
+
+	p.remoteMu.RLock()
+	hosts := make([]string, 0, len(p.remoteHosts)+1)
+	hosts = append(hosts, p.hostname)
+	remotes := make([]Host[V], 0, len(p.remoteHosts))
+	for h, r := range p.remoteHosts {
+		hosts = append(hosts, h)
+		remotes = append(remotes, r)
+	}
+	p.remoteMu.RUnlock()
+
+	p.forAllHosts(func(remote Host[V]) {
+		knownByRemote, err := remote.Negotiate(hosts)
+
+		if err != nil {
+			log.Printf("Negotiate with %s failed: %v", remote.Name(), err)
+			return
+		}
+		for _, h := range knownByRemote {
+			if !p.IsKnown(h) {
+				go p.AddRemote(h)
+			}
+		}
+	})
+}
+
+func (p *SimpleGrainPool[V]) forAllHosts(fn func(Host[V])) {
+	p.remoteMu.RLock()
+	rh := maps.Clone(p.remoteHosts)
+	p.remoteMu.RUnlock()
+
+	wg := sync.WaitGroup{}
+	for _, host := range rh {
+
+		wg.Go(func() { fn(host) })
+
+	}
+
+	for name, host := range rh {
+		if !host.IsHealthy() {
+			host.Close()
+			p.remoteMu.Lock()
+			delete(p.remoteHosts, name)
+			p.remoteMu.Unlock()
+		}
+
+	}
+}
+
+func (p *SimpleGrainPool[V]) broadcastOwnership(ids []uint64) {
+	if len(ids) == 0 {
+		return
+	}
+
+	p.forAllHosts(func(rh Host[V]) {
+		rh.AnnounceOwnership(p.hostname, ids)
+	})
+	log.Printf("%s taking ownership of %d ids", p.hostname, len(ids))
+	// go p.statsUpdate()
+}
+
+func (p *SimpleGrainPool[V]) getOrClaimGrain(ctx context.Context, id uint64) (Grain[V], error) {
+	p.localMu.RLock()
+	grain, exists := p.grains[id]
+	p.localMu.RUnlock()
+	if exists && grain != nil {
+		return grain, nil
+	}
+
+	grain, err := p.spawn(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	go p.broadcastOwnership([]uint64{id})
+	p.localMu.Lock()
+	p.grains[id] = grain
+	p.localMu.Unlock()
+
+	return grain, nil
+}
+
+// // ErrNotOwner is returned when a cart belongs to another host.
+// var ErrNotOwner = fmt.Errorf("not owner")
+
+// Apply applies a mutation to a grain.
+func (p *SimpleGrainPool[V]) Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*MutationResult[V], error) {
+	grain, err := p.getOrClaimGrain(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	mutations, err := p.mutationRegistry.Apply(ctx, grain, mutation...)
+	if err != nil {
+		return nil, err
+	}
+	if p.storage != nil {
+		go func() {
+			if err := p.storage.AppendMutations(id, mutation...); err != nil {
+				log.Printf("failed to store mutation for grain %d: %v", id, err)
+			}
+		}()
+	}
+	for _, listener := range p.listeners {
+		go listener.AppendMutations(id, mutations...)
+	}
+	result, err := grain.GetCurrentState()
+	if err != nil {
+		return nil, err
+	}
+
+	return &MutationResult[V]{
+		Result:    *result,
+		Mutations: mutations,
+	}, nil
+}
+
+// Get returns the current state of a grain.
+func (p *SimpleGrainPool[V]) Get(ctx context.Context, id uint64) (*V, error) {
+	grain, err := p.getOrClaimGrain(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	return grain.GetCurrentState()
+}
+
+// OwnerHost reports the remote owner (if any) for the supplied cart id.
+func (p *SimpleGrainPool[V]) OwnerHost(id uint64) (Host[V], bool) {
+	p.remoteMu.RLock()
+	defer p.remoteMu.RUnlock()
+	owner, ok := p.remoteOwners[id]
+	return owner, ok
+}
+
+// Hostname returns the local hostname (pod IP).
+func (p *SimpleGrainPool[V]) Hostname() string {
+	return p.hostname
+}
+
+// Close notifies remotes that this host is shutting down.
+func (p *SimpleGrainPool[V]) Close() {
+
+	p.forAllHosts(func(rh Host[V]) {
+		rh.Close()
+	})
+
+	if p.purgeTicker != nil {
+		p.purgeTicker.Stop()
+	}
+}

pkg/actor/state.go

@@ -0,0 +1,98 @@
+package actor
+
+import (
+	"bufio"
+	"encoding/json"
+	"errors"
+	"io"
+	"time"
+
+	"google.golang.org/protobuf/proto"
+)
+
+type StateStorage struct {
+	registry MutationRegistry
+}
+
+type StorageEvent struct {
+	Type      string        `json:"type"`
+	TimeStamp time.Time     `json:"timestamp"`
+	Mutation  proto.Message `json:"mutation"`
+}
+
+type rawEvent struct {
+	Type      string          `json:"type"`
+	TimeStamp time.Time       `json:"timestamp"`
+	Mutation  json.RawMessage `json:"mutation"`
+}
+
+func NewState(registry MutationRegistry) *StateStorage {
+	return &StateStorage{
+		registry: registry,
+	}
+}
+
+var ErrUnknownType = errors.New("unknown type")
+
+func (s *StateStorage) Load(r io.Reader, onMessage func(msg proto.Message, timeStamp time.Time)) error {
+	var err error
+	var evt *StorageEvent
+	scanner := bufio.NewScanner(r)
+	for err == nil {
+		evt, err = s.Read(scanner)
+		if err == nil {
+			onMessage(evt.Mutation, evt.TimeStamp)
+		}
+	}
+	if err == io.EOF {
+		return nil
+	}
+	return err
+}
+
+func (s *StateStorage) Append(io io.Writer, mutation proto.Message, timeStamp time.Time) error {
+	typeName, ok := s.registry.GetTypeName(mutation)
+	if !ok {
+		return ErrUnknownType
+	}
+	event := &StorageEvent{
+		Type:      typeName,
+		TimeStamp: timeStamp,
+		Mutation:  mutation,
+	}
+	jsonBytes, err := json.Marshal(event)
+	if err != nil {
+		return err
+	}
+	if _, err := io.Write(jsonBytes); err != nil {
+		return err
+	}
+	io.Write([]byte("\n"))
+	return nil
+}
+
+func (s *StateStorage) Read(r *bufio.Scanner) (*StorageEvent, error) {
+	var event rawEvent
+
+	if r.Scan() {
+		b := r.Bytes()
+		err := json.Unmarshal(b, &event)
+		if err != nil {
+			return nil, err
+		}
+		typeName := event.Type
+		mutation, ok := s.registry.Create(typeName)
+		if !ok {
+			return nil, ErrUnknownType
+		}
+		if err := json.Unmarshal(event.Mutation, mutation); err != nil {
+			return nil, err
+		}
+		return &StorageEvent{
+			Type:      typeName,
+			TimeStamp: event.TimeStamp,
+			Mutation:  mutation,
+		}, r.Err()
+	}
+	return nil, io.EOF
+}

pkg/cart/cart-grain.go

@@ -0,0 +1,276 @@
+package cart
+
+import (
+	"encoding/json"
+	"sync"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/voucher"
+	"github.com/matst80/go-redis-inventory/pkg/inventory"
+)
+
+// Legacy padded [16]byte CartId and its helper methods removed.
+// Unified CartId (uint64 with base62 string form) now defined in cart_id.go.
+
+type StockStatus int
+
+type ItemMeta struct {
+	Name       string  `json:"name"`
+	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"`
+	SellerName string  `json:"sellerName,omitempty"`
+	Image      string  `json:"image,omitempty"`
+	Outlet     *string `json:"outlet,omitempty"`
+}
+
+type CartItem struct {
+	Id                    uint32  `json:"id"`
+	ItemId                uint32  `json:"itemId,omitempty"`
+	ParentId              *uint32 `json:"parentId,omitempty"`
+	Sku                   string  `json:"sku"`
+	Price                 Price   `json:"price"`
+	TotalPrice            Price   `json:"totalPrice"`
+	SellerId              string  `json:"sellerId,omitempty"`
+	OrgPrice              *Price  `json:"orgPrice,omitempty"`
+	Cgm                   string  `json:"cgm,omitempty"`
+	Tax                   int
+	Stock                 uint16     `json:"stock"`
+	Quantity              uint16     `json:"qty"`
+	Discount              *Price     `json:"discount,omitempty"`
+	Disclaimer            string     `json:"disclaimer,omitempty"`
+	ArticleType           string     `json:"type,omitempty"`
+	StoreId               *string    `json:"storeId,omitempty"`
+	Meta                  *ItemMeta  `json:"meta,omitempty"`
+	SaleStatus            string     `json:"saleStatus"`
+	Marking               *Marking   `json:"marking,omitempty"`
+	SubscriptionDetailsId string     `json:"subscriptionDetailsId,omitempty"`
+	OrderReference        string     `json:"orderReference,omitempty"`
+	IsSubscribed          bool       `json:"isSubscribed,omitempty"`
+	ReservationEndTime    *time.Time `json:"reservationEndTime,omitempty"`
+}
+
+type CartNotification struct {
+	LinkedId int    `json:"id"`
+	Provider string `json:"provider"`
+	Title    string `json:"title"`
+	Content  string `json:"content"`
+}
+
+type SubscriptionDetails struct {
+	Id           string          `json:"id,omitempty"`
+	Version      uint16          `json:"version"`
+	OfferingCode string          `json:"offeringCode,omitempty"`
+	SigningType  string          `json:"signingType,omitempty"`
+	Meta         json.RawMessage `json:"data,omitempty"`
+}
+
+type Notice struct {
+	Timestamp time.Time `json:"timestamp"`
+	Message   string    `json:"message"`
+	Code      *string   `json:"code,omitempty"`
+}
+
+type CartPaymentStatus string
+
+const (
+	CartPaymentStatusPending   CartPaymentStatus = "pending"
+	CartPaymentStatusFailed    CartPaymentStatus = "failed"
+	CartPaymentStatusSuccess   CartPaymentStatus = "success"
+	CartPaymentStatusCancelled CartPaymentStatus = "partial"
+)
+
+type Marking struct {
+	Type uint32 `json:"type"`
+	Text string `json:"text"`
+}
+
+type CartGrain struct {
+	mu                sync.RWMutex
+	lastItemId        uint32
+	lastVoucherId     uint32
+	lastAccess        time.Time
+	lastChange        time.Time // unix seconds of last successful mutation (replay sets from event ts)
+	userId            string
+	Currency          string      `json:"currency"`
+	Language          string      `json:"language"`
+	Version           uint        `json:"version"`
+	InventoryReserved bool        `json:"inventoryReserved"`
+	Id                CartId      `json:"id"`
+	Items             []*CartItem `json:"items"`
+	TotalPrice        *Price      `json:"totalPrice"`
+	TotalDiscount     *Price      `json:"totalDiscount"`
+	Processing        bool        `json:"processing"`
+	//PaymentInProgress uint16      `json:"paymentInProgress"`
+	OrderReference string `json:"orderReference,omitempty"`
+
+	Vouchers            []*Voucher                      `json:"vouchers,omitempty"`
+	Notifications       []CartNotification              `json:"cartNotification,omitempty"`
+	SubscriptionDetails map[string]*SubscriptionDetails `json:"subscriptionDetails,omitempty"`
+
+	//CheckoutOrderId        string                          `json:"checkoutOrderId,omitempty"`
+	CheckoutStatus *CartPaymentStatus `json:"checkoutStatus,omitempty"`
+	//CheckoutCountry        string                          `json:"checkoutCountry,omitempty"`
+}
+
+type Voucher struct {
+	Code        string   `json:"code"`
+	Applied     bool     `json:"applied"`
+	Rules       []string `json:"rules"`
+	Description string   `json:"description,omitempty"`
+	Id          uint32   `json:"id"`
+	Value       int64    `json:"value"`
+}
+
+func (v *Voucher) AppliesTo(cart *CartGrain) ([]*CartItem, bool) {
+	// No rules -> applies to entire cart
+	if len(v.Rules) == 0 {
+		return cart.Items, true
+	}
+
+	// Build evaluation context once
+	ctx := voucher.EvalContext{
+		Items:        make([]voucher.Item, 0, len(cart.Items)),
+		CartTotalInc: 0,
+	}
+
+	if cart.TotalPrice != nil {
+		ctx.CartTotalInc = cart.TotalPrice.IncVat
+	}
+
+	for _, it := range cart.Items {
+		category := ""
+		if it.Meta != nil {
+			category = it.Meta.Category
+		}
+		ctx.Items = append(ctx.Items, voucher.Item{
+			Sku:       it.Sku,
+			Category:  category,
+			UnitPrice: it.Price.IncVat,
+		})
+	}
+
+	// All voucher rules must pass (logical AND)
+	for _, expr := range v.Rules {
+
+		if expr == "" {
+			// Empty condition treated as pass (acts like a comment / placeholder)
+			continue
+		}
+		rs, err := voucher.ParseRules(expr)
+		if err != nil {
+			// Fail closed on parse error
+			return nil, false
+		}
+		if !rs.Applies(ctx) {
+			return nil, false
+		}
+	}
+
+	return cart.Items, true
+}
+
+func NewCartGrain(id uint64, ts time.Time) *CartGrain {
+	return &CartGrain{
+		lastItemId:          0,
+		lastVoucherId:       0,
+		lastAccess:          ts,
+		lastChange:          ts,
+		TotalDiscount:       NewPrice(),
+		Vouchers:            []*Voucher{},
+		Id:                  CartId(id),
+		Items:               []*CartItem{},
+		TotalPrice:          NewPrice(),
+		SubscriptionDetails: make(map[string]*SubscriptionDetails),
+	}
+}
+
+func (c *CartGrain) GetId() uint64 {
+	return uint64(c.Id)
+}
+
+func (c *CartGrain) GetLastChange() time.Time {
+	return c.lastChange
+}
+
+func (c *CartGrain) GetLastAccess() time.Time {
+	return c.lastAccess
+}
+
+func (c *CartGrain) GetCurrentState() (*CartGrain, error) {
+	c.lastAccess = time.Now()
+	return c, nil
+}
+
+func (c *CartGrain) HandleInventoryChange(change inventory.InventoryChange) {
+	for _, item := range c.Items {
+		l := "se"
+		if item.StoreId != nil {
+			l = *item.StoreId
+		}
+		if item.Sku == change.SKU && change.StockLocationID == l {
+			item.Stock = uint16(change.Value)
+			break
+		}
+	}
+}
+
+func (c *CartGrain) GetState() ([]byte, error) {
+	return json.Marshal(c)
+}
+
+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 (c *CartGrain) UpdateTotals() {
+	c.TotalPrice = NewPrice()
+	c.TotalDiscount = NewPrice()
+
+	for _, item := range c.Items {
+		rowTotal := MultiplyPrice(item.Price, int64(item.Quantity))
+
+		if item.OrgPrice != nil {
+			diff := NewPrice()
+			diff.Add(*item.OrgPrice)
+			diff.Subtract(item.Price)
+			diff.Multiply(int64(item.Quantity))
+			//rowTotal.Subtract(*diff)
+			item.Discount = diff
+			if diff.IncVat > 0 {
+				c.TotalDiscount.Add(*diff)
+			}
+		}
+
+		item.TotalPrice = *rowTotal
+
+		c.TotalPrice.Add(*rowTotal)
+
+	}
+
+	for _, voucher := range c.Vouchers {
+		_, ok := voucher.AppliesTo(c)
+		voucher.Applied = false
+		if ok {
+			value := NewPriceFromIncVat(voucher.Value, 25)
+			if c.TotalPrice.IncVat <= value.IncVat {
+				// don't apply discounts to more than the total price
+				continue
+			}
+			voucher.Applied = true
+			c.TotalDiscount.Add(*value)
+			c.TotalPrice.Subtract(*value)
+		}
+	}
+
+}

pkg/cart/cart-mutation-helper.go

@@ -0,0 +1,87 @@
+package cart
+
+import (
+	"context"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/actor"
+	"github.com/matst80/go-redis-inventory/pkg/inventory"
+)
+
+type CartMutationContext struct {
+	reservationService inventory.CartReservationService
+}
+
+func NewCartMutationContext(reservationService inventory.CartReservationService) *CartMutationContext {
+	return &CartMutationContext{
+		reservationService: reservationService,
+	}
+}
+
+func (c *CartMutationContext) ReserveItem(ctx context.Context, cartId CartId, sku string, locationId *string, quantity uint16) (*time.Time, error) {
+
+	if quantity <= 0 || c.reservationService == nil {
+		return nil, nil
+	}
+
+	l := inventory.LocationID("se")
+	if locationId != nil {
+		l = inventory.LocationID(*locationId)
+	}
+	ttl := time.Minute * 15
+	endTime := time.Now().Add(ttl)
+	err := c.reservationService.ReserveForCart(ctx, inventory.CartReserveRequest{
+		CartID: inventory.CartID(cartId.String()),
+		InventoryReference: &inventory.InventoryReference{
+			SKU:        inventory.SKU(sku),
+			LocationID: l,
+		},
+		TTL:      ttl,
+		Quantity: uint32(quantity),
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return &endTime, nil
+
+}
+
+func (c *CartMutationContext) UseReservations(item *CartItem) bool {
+	if item.ReservationEndTime != nil {
+		return true
+	}
+	return item.Cgm == "55010"
+}
+
+func (c *CartMutationContext) ReleaseItem(ctx context.Context, cartId CartId, sku string, locationId *string) error {
+	if c.reservationService == nil {
+		return nil
+	}
+	l := inventory.LocationID("se")
+	if locationId != nil {
+		l = inventory.LocationID(*locationId)
+	}
+	return c.reservationService.ReleaseForCart(ctx, inventory.SKU(sku), l, inventory.CartID(cartId.String()))
+}
+
+func NewCartMultationRegistry(context *CartMutationContext) actor.MutationRegistry {
+
+	reg := actor.NewMutationRegistry()
+	reg.RegisterMutations(
+		actor.NewMutation(context.AddItem),
+		actor.NewMutation(context.ChangeQuantity),
+		actor.NewMutation(context.RemoveItem),
+		actor.NewMutation(ClearCart),
+		actor.NewMutation(AddVoucher),
+		actor.NewMutation(RemoveVoucher),
+		actor.NewMutation(UpsertSubscriptionDetails),
+		actor.NewMutation(SetUserId),
+		actor.NewMutation(LineItemMarking),
+		actor.NewMutation(RemoveLineItemMarking),
+		actor.NewMutation(SubscriptionAdded),
+		//		actor.NewMutation(SubscriptionRemoved),
+	)
+	return reg
+
+}

pkg/cart/cart_id.go

@@ -0,0 +1,161 @@
+package cart
+
+import (
+	"crypto/rand"
+	"encoding/json"
+	"fmt"
+
+	"git.k6n.net/go-cart-actor/pkg/actor"
+)
+
+// cart_id.go
+//
+// Breaking change:
+//   Unified cart identifier as a raw 64-bit unsigned integer (type CartId uint64).
+//   External textual representation: base62 (0-9 A-Z a-z), shortest possible
+//   encoding for 64 bits (max 11 characters, since 62^11 > 2^64).
+//
+// Rationale:
+//   - Replaces legacy fixed [16]byte padded string and transitional CartID wrapper.
+//   - Provides compact, URL/cookie-friendly identifiers.
+//   - O(1) hashing and minimal memory footprint.
+//   - 64 bits of crypto randomness => negligible collision probability at realistic scale.
+//
+// Public API:
+//   type CartId uint64
+//   func NewCartId() (CartId, error)
+//   func MustNewCartId() CartId
+//   func ParseCartId(string) (CartId, bool)
+//   func MustParseCartId(string) CartId
+//   (CartId).String() string
+//   (CartId).MarshalJSON() / UnmarshalJSON()
+//
+// NOTE:
+//   All legacy helpers (UpgradeLegacyCartId, Fallback hashing, Canonicalize variants,
+//   CartIDToLegacy, LegacyToCartID) have been removed as part of the breaking change.
+//
+// ---------------------------------------------------------------------------
+
+type CartId actor.GrainId
+
+const base62Alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+
+// Reverse lookup (0xFF marks invalid)
+var base62Rev [256]byte
+
+func init() {
+	for i := range base62Rev {
+		base62Rev[i] = 0xFF
+	}
+	for i := 0; i < len(base62Alphabet); i++ {
+		base62Rev[base62Alphabet[i]] = byte(i)
+	}
+}
+
+// String returns the canonical base62 encoding of the 64-bit id.
+func (id CartId) String() string {
+	return encodeBase62(uint64(id))
+}
+
+// MarshalJSON encodes the cart id as a JSON string.
+func (id CartId) MarshalJSON() ([]byte, error) {
+	return json.Marshal(id.String())
+}
+
+// UnmarshalJSON decodes a cart id from a JSON string containing base62 text.
+func (id *CartId) UnmarshalJSON(data []byte) error {
+	var s string
+	if err := json.Unmarshal(data, &s); err != nil {
+		return err
+	}
+	parsed, ok := ParseCartId(s)
+	if !ok {
+		return fmt.Errorf("invalid cart id: %q", s)
+	}
+	*id = parsed
+	return nil
+}
+
+// NewCartId generates a new cryptographically random non-zero 64-bit id.
+func NewCartId() (CartId, error) {
+	var b [8]byte
+	if _, err := rand.Read(b[:]); err != nil {
+		return 0, fmt.Errorf("NewCartId: %w", err)
+	}
+	u := (uint64(b[0]) << 56) |
+		(uint64(b[1]) << 48) |
+		(uint64(b[2]) << 40) |
+		(uint64(b[3]) << 32) |
+		(uint64(b[4]) << 24) |
+		(uint64(b[5]) << 16) |
+		(uint64(b[6]) << 8) |
+		uint64(b[7])
+	if u == 0 {
+		// Extremely unlikely; regenerate once to avoid "0" identifier if desired.
+		return NewCartId()
+	}
+	return CartId(u), nil
+}
+
+// MustNewCartId panics if generation fails.
+func MustNewCartId() CartId {
+	id, err := NewCartId()
+	if err != nil {
+		panic(err)
+	}
+	return id
+}
+
+// ParseCartId parses a base62 string into a CartId.
+// Returns (0,false) for invalid input.
+func ParseCartId(s string) (CartId, bool) {
+	// Accept length 1..11 (11 sufficient for 64 bits). Reject >11 immediately.
+	// Provide a slightly looser upper bound (<=16) only if you anticipate future
+	// extensions; here we stay strict.
+	if len(s) == 0 || len(s) > 11 {
+		return 0, false
+	}
+	u, ok := decodeBase62(s)
+	if !ok {
+		return 0, false
+	}
+	return CartId(u), true
+}
+
+// MustParseCartId panics on invalid base62 input.
+func MustParseCartId(s string) CartId {
+	id, ok := ParseCartId(s)
+	if !ok {
+		panic(fmt.Sprintf("invalid cart id: %q", s))
+	}
+	return id
+}
+
+// encodeBase62 converts a uint64 to base62 (shortest form).
+func encodeBase62(u uint64) string {
+	if u == 0 {
+		return "0"
+	}
+	var buf [11]byte
+	i := len(buf)
+	for u > 0 {
+		i--
+		buf[i] = base62Alphabet[u%62]
+		u /= 62
+	}
+	return string(buf[i:])
+}
+
+// decodeBase62 converts base62 text to uint64.
+func decodeBase62(s string) (uint64, bool) {
+	var v uint64
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		d := base62Rev[c]
+		if d == 0xFF {
+			return 0, false
+		}
+		v = v*62 + uint64(d)
+	}
+	return v, true
+}

pkg/cart/cart_id_test.go

@@ -0,0 +1,185 @@
+package cart
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+)
+
+// TestNewCartIdUniqueness generates many ids and checks for collisions.
+func TestNewCartIdUniqueness(t *testing.T) {
+	const n = 20000
+	seen := make(map[string]struct{}, n)
+	for i := 0; i < n; i++ {
+		id, err := NewCartId()
+		if err != nil {
+			t.Fatalf("NewCartId error: %v", err)
+		}
+		s := id.String()
+		if _, exists := seen[s]; exists {
+			t.Fatalf("duplicate id encountered: %s", s)
+		}
+		seen[s] = struct{}{}
+		if s == "" {
+			t.Fatalf("empty string representation for id %d", id)
+		}
+		if len(s) > 11 {
+			t.Fatalf("encoded id length exceeds 11 chars: %s (%d)", s, len(s))
+		}
+		if id == 0 {
+			// We force regeneration on zero, extremely unlikely but test guards intent.
+			t.Fatalf("zero id generated (should be regenerated)")
+		}
+	}
+}
+
+// TestParseCartIdRoundTrip ensures parse -> string -> parse is stable.
+func TestParseCartIdRoundTrip(t *testing.T) {
+	id := MustNewCartId()
+	txt := id.String()
+	parsed, ok := ParseCartId(txt)
+	if !ok {
+		t.Fatalf("ParseCartId failed for valid text %q", txt)
+	}
+	if parsed != id {
+		t.Fatalf("round trip mismatch: original=%d parsed=%d txt=%s", id, parsed, txt)
+	}
+}
+
+// TestParseCartIdInvalid covers invalid inputs.
+func TestParseCartIdInvalid(t *testing.T) {
+	invalid := []string{
+		"",               // empty
+		" ",              // space
+		"01234567890abc", // >11 chars
+		"!!!!",           // invalid chars
+		"-underscore-",   // invalid chars
+		"abc_def",        // underscore invalid for base62
+		"0123456789ABCD", // 14 chars
+	}
+	for _, s := range invalid {
+		if _, ok := ParseCartId(s); ok {
+			t.Fatalf("expected parse failure for %q", s)
+		}
+	}
+}
+
+// TestMustParseCartIdPanics verifies panic behavior for invalid input.
+func TestMustParseCartIdPanics(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fatalf("expected panic for invalid MustParseCartId input")
+		}
+	}()
+	_ = MustParseCartId("not*base62")
+}
+
+// TestJSONMarshalUnmarshalCartId verifies JSON round trip.
+func TestJSONMarshalUnmarshalCartId(t *testing.T) {
+	id := MustNewCartId()
+	data, err := json.Marshal(struct {
+		Cart CartId `json:"cart"`
+	}{Cart: id})
+	if err != nil {
+		t.Fatalf("marshal error: %v", err)
+	}
+	var out struct {
+		Cart CartId `json:"cart"`
+	}
+	if err := json.Unmarshal(data, &out); err != nil {
+		t.Fatalf("unmarshal error: %v", err)
+	}
+	if out.Cart != id {
+		t.Fatalf("JSON round trip mismatch: have %d got %d", id, out.Cart)
+	}
+}
+
+// TestBase62LengthBound checks worst-case length (near max uint64).
+func TestBase62LengthBound(t *testing.T) {
+	// Largest uint64
+	const maxU64 = ^uint64(0)
+	s := encodeBase62(maxU64)
+	if len(s) > 11 {
+		t.Fatalf("max uint64 encoded length > 11: %d (%s)", len(s), s)
+	}
+	dec, ok := decodeBase62(s)
+	if !ok || dec != maxU64 {
+		t.Fatalf("decode failed for max uint64: ok=%v dec=%d want=%d", ok, dec, maxU64)
+	}
+}
+
+// TestZeroEncoding ensures zero value encodes to "0" and parses back.
+func TestZeroEncoding(t *testing.T) {
+	if s := encodeBase62(0); s != "0" {
+		t.Fatalf("encodeBase62(0) expected '0', got %q", s)
+	}
+	v, ok := decodeBase62("0")
+	if !ok || v != 0 {
+		t.Fatalf("decodeBase62('0') failed: ok=%v v=%d", ok, v)
+	}
+	if _, ok := ParseCartId("0"); !ok {
+		t.Fatalf("ParseCartId(\"0\") should succeed")
+	}
+}
+
+// TestSequentialParse ensures sequentially generated ids parse correctly.
+func TestSequentialParse(t *testing.T) {
+	for i := 0; i < 1000; i++ {
+		id := MustNewCartId()
+		txt := id.String()
+		parsed, ok := ParseCartId(txt)
+		if !ok || parsed != id {
+			t.Fatalf("sequential parse mismatch: idx=%d orig=%d parsed=%d txt=%s", i, id, parsed, txt)
+		}
+	}
+}
+
+// BenchmarkNewCartId measures generation performance.
+func BenchmarkNewCartId(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		if _, err := NewCartId(); err != nil {
+			b.Fatalf("NewCartId error: %v", err)
+		}
+	}
+}
+
+// BenchmarkEncodeBase62 measures encoding performance.
+func BenchmarkEncodeBase62(b *testing.B) {
+	// Precompute sample values
+	samples := make([]uint64, 1024)
+	for i := range samples {
+		// Spread bits without crypto randomness overhead
+		samples[i] = (uint64(i) << 53) ^ (uint64(i) * 0x9E3779B185EBCA87)
+	}
+	b.ResetTimer()
+	var sink string
+	for i := 0; i < b.N; i++ {
+		sink = encodeBase62(samples[i%len(samples)])
+	}
+	_ = sink
+}
+
+// BenchmarkDecodeBase62 measures decoding performance.
+func BenchmarkDecodeBase62(b *testing.B) {
+	encoded := make([]string, 1024)
+	for i := range encoded {
+		encoded[i] = encodeBase62((uint64(i) << 32) | uint64(i))
+	}
+	b.ResetTimer()
+	var sum uint64
+	for i := 0; i < b.N; i++ {
+		v, ok := decodeBase62(encoded[i%len(encoded)])
+		if !ok {
+			b.Fatalf("decode failure for %s", encoded[i%len(encoded)])
+		}
+		sum ^= v
+	}
+	_ = sum
+}
+
+// ExampleCartIdString documents usage of CartId string form.
+func ExampleCartId_string() {
+	id := MustNewCartId()
+	fmt.Println(len(id.String()) <= 11) // outputs true
+	// Output: true
+}

pkg/cart/mutation_add_item.go

@@ -0,0 +1,141 @@
+package cart
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"time"
+
+	cart_messages "git.k6n.net/go-cart-actor/proto/cart"
+	"google.golang.org/protobuf/types/known/timestamppb"
+)
+
+// mutation_add_item.go
+//
+// Registers the AddItem cart mutation in the generic mutation registry.
+// This replaces the legacy switch-based logic previously found in CartGrain.Apply.
+//
+// Behavior:
+//   - Validates quantity > 0
+//   - If an item with same SKU exists -> increases quantity
+//   - Else creates a new CartItem with computed tax amounts
+//   - Totals recalculated automatically via WithTotals()
+//
+// NOTE: Any future field additions in messages.AddItem that affect pricing / tax
+// must keep this handler in sync.
+var ErrPaymentInProgress = errors.New("payment in progress")
+
+func (c *CartMutationContext) AddItem(g *CartGrain, m *cart_messages.AddItem) error {
+	ctx := context.Background()
+	if m == nil {
+		return fmt.Errorf("AddItem: nil payload")
+	}
+	if m.Quantity < 1 {
+		return fmt.Errorf("AddItem: invalid quantity %d", m.Quantity)
+	}
+
+	// Merge with any existing item having same SKU and matching StoreId (including both nil).
+	for _, existing := range g.Items {
+		if existing.Sku != m.Sku {
+			continue
+		}
+		sameStore := (existing.StoreId == nil && m.StoreId == nil) ||
+			(existing.StoreId != nil && m.StoreId != nil && *existing.StoreId == *m.StoreId)
+		if !sameStore {
+			continue
+		}
+		if c.UseReservations(existing) {
+			if err := c.ReleaseItem(ctx, g.Id, existing.Sku, existing.StoreId); err != nil {
+				log.Printf("failed to release item %d: %v", existing.Id, err)
+			}
+			endTime, err := c.ReserveItem(ctx, g.Id, existing.Sku, existing.StoreId, existing.Quantity+uint16(m.Quantity))
+			if err != nil {
+				return err
+			}
+			existing.ReservationEndTime = endTime
+		}
+		existing.Quantity += uint16(m.Quantity)
+		existing.Stock = uint16(m.Stock)
+		// If existing had nil store but new has one, adopt it.
+		if existing.StoreId == nil && m.StoreId != nil {
+			existing.StoreId = m.StoreId
+		}
+
+		return nil
+	}
+
+	g.mu.Lock()
+	defer g.mu.Unlock()
+
+	g.lastItemId++
+	taxRate := float32(25.0)
+	if m.Tax > 0 {
+		taxRate = float32(int(m.Tax) / 100)
+	}
+
+	pricePerItem := NewPriceFromIncVat(m.Price, taxRate)
+
+	needsReservation := true
+	if m.ReservationEndTime != nil {
+		needsReservation = m.ReservationEndTime.AsTime().Before(time.Now())
+	}
+
+	cartItem := &CartItem{
+		Id:       g.lastItemId,
+		ItemId:   uint32(m.ItemId),
+		Quantity: uint16(m.Quantity),
+		Sku:      m.Sku,
+		Tax:      int(taxRate * 100),
+		Meta: &ItemMeta{
+			Name:       m.Name,
+			Image:      m.Image,
+			Brand:      m.Brand,
+			Category:   m.Category,
+			Category2:  m.Category2,
+			Category3:  m.Category3,
+			Category4:  m.Category4,
+			Category5:  m.Category5,
+			Outlet:     m.Outlet,
+			SellerName: m.SellerName,
+		},
+		SellerId:   m.SellerId,
+		Cgm:        m.Cgm,
+		SaleStatus: m.SaleStatus,
+		ParentId:   m.ParentId,
+
+		Price:      *pricePerItem,
+		TotalPrice: *MultiplyPrice(*pricePerItem, int64(m.Quantity)),
+
+		Stock:      uint16(m.Stock),
+		Disclaimer: m.Disclaimer,
+
+		OrgPrice:    getOrgPrice(m.OrgPrice, taxRate),
+		ArticleType: m.ArticleType,
+
+		StoreId: m.StoreId,
+	}
+
+	if needsReservation && c.UseReservations(cartItem) {
+		endTime, err := c.ReserveItem(ctx, g.Id, m.Sku, m.StoreId, uint16(m.Quantity))
+		if err != nil {
+			return err
+		}
+		if endTime != nil {
+			m.ReservationEndTime = timestamppb.New(*endTime)
+			t := m.ReservationEndTime.AsTime()
+			cartItem.ReservationEndTime = &t
+		}
+	}
+
+	g.Items = append(g.Items, cartItem)
+	g.UpdateTotals()
+	return nil
+}
+
+func getOrgPrice(orgPrice int64, taxRate float32) *Price {
+	if orgPrice <= 0 {
+		return nil
+	}
+	return NewPriceFromIncVat(orgPrice, taxRate)
+}

pkg/cart/mutation_add_voucher.go

@@ -0,0 +1,69 @@
+package cart
+
+import (
+	"slices"
+
+	"git.k6n.net/go-cart-actor/pkg/actor"
+	messages "git.k6n.net/go-cart-actor/proto/cart"
+)
+
+func RemoveVoucher(g *CartGrain, m *messages.RemoveVoucher) error {
+	if m == nil {
+		return &actor.MutationError{
+			Message:    "RemoveVoucher: nil payload",
+			Code:       1003,
+			StatusCode: 400,
+		}
+	}
+	if g.CheckoutStatus != nil {
+		return ErrPaymentInProgress
+	}
+
+	if !slices.ContainsFunc(g.Vouchers, func(v *Voucher) bool {
+		return v.Id == m.Id
+	}) {
+		return &actor.MutationError{
+			Message:    "voucher not applied",
+			Code:       1004,
+			StatusCode: 400,
+		}
+	}
+
+	g.Vouchers = slices.DeleteFunc(g.Vouchers, func(v *Voucher) bool {
+		return v.Id == m.Id
+	})
+	g.UpdateTotals()
+	return nil
+}
+
+func AddVoucher(g *CartGrain, m *messages.AddVoucher) error {
+	if m == nil {
+		return &actor.MutationError{
+			Message:    "AddVoucher: nil payload",
+			Code:       1001,
+			StatusCode: 400,
+		}
+	}
+
+	if slices.ContainsFunc(g.Vouchers, func(v *Voucher) bool {
+		return v.Code == m.Code
+	}) {
+		return &actor.MutationError{
+			Message:    "voucher already applied",
+			Code:       1002,
+			StatusCode: 400,
+		}
+	}
+
+	g.lastVoucherId++
+	g.Vouchers = append(g.Vouchers, &Voucher{
+		Id:          g.lastVoucherId,
+		Applied:     false,
+		Description: m.Description,
+		Code:        m.Code,
+		Rules:       m.VoucherRules,
+		Value:       m.Value,
+	})
+	g.UpdateTotals()
+	return nil
+}

pkg/cart/mutation_change_quantity.go

@@ -0,0 +1,85 @@
+package cart
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"time"
+
+	messages "git.k6n.net/go-cart-actor/proto/cart"
+)
+
+// mutation_change_quantity.go
+//
+// Registers the ChangeQuantity mutation.
+//
+// Behavior:
+//   - Locates an item by its cart-local line item Id (not source item_id).
+//   - If requested quantity <= 0 the line is removed.
+//   - Otherwise the line's Quantity field is updated.
+//   - Totals are recalculated (WithTotals).
+//
+// Error handling:
+//   - Returns an error if the item Id is not found.
+//   - Returns an error if payload is nil (defensive).
+//
+// Concurrency:
+//   - Uses the grain's RW-safe mutation pattern: we mutate in place under
+//     the grain's implicit expectation that higher layers control access.
+//     (If strict locking is required around every mutation, wrap logic in
+//     an explicit g.mu.Lock()/Unlock(), but current model mirrors prior code.)
+
+func (c *CartMutationContext) ChangeQuantity(g *CartGrain, m *messages.ChangeQuantity) error {
+	if m == nil {
+		return fmt.Errorf("ChangeQuantity: nil payload")
+	}
+
+	ctx := context.Background()
+
+	foundIndex := -1
+	for i, it := range g.Items {
+		if it.Id == uint32(m.Id) {
+			foundIndex = i
+			break
+		}
+	}
+	if foundIndex == -1 {
+		return fmt.Errorf("ChangeQuantity: item id %d not found", m.Id)
+	}
+
+	if m.Quantity <= 0 {
+		// Remove the item
+		itemToRemove := g.Items[foundIndex]
+		if itemToRemove.ReservationEndTime != nil && itemToRemove.ReservationEndTime.Before(time.Now()) {
+			err := c.ReleaseItem(ctx, g.Id, itemToRemove.Sku, itemToRemove.StoreId)
+			if err != nil {
+				log.Printf("unable to release reservation for %s in location: %v", itemToRemove.Sku, itemToRemove.StoreId)
+			}
+		}
+		g.Items = append(g.Items[:foundIndex], g.Items[foundIndex+1:]...)
+		g.UpdateTotals()
+		return nil
+	}
+	item := g.Items[foundIndex]
+	if item == nil {
+		return fmt.Errorf("ChangeQuantity: item id %d not found", m.Id)
+	}
+	if c.UseReservations(item) {
+		if item.ReservationEndTime != nil {
+			err := c.ReleaseItem(ctx, g.Id, item.Sku, item.StoreId)
+			if err != nil {
+				log.Printf("unable to release reservation for %s in location: %v", item.Sku, item.StoreId)
+			}
+
+		}
+		endTime, err := c.ReserveItem(ctx, g.Id, item.Sku, item.StoreId, uint16(m.Quantity))
+		if err != nil {
+			return err
+		}
+		item.ReservationEndTime = endTime
+	}
+	item.Quantity = uint16(m.Quantity)
+	g.UpdateTotals()
+
+	return nil
+}

pkg/cart/mutation_clear_cart.go

@@ -0,0 +1,26 @@
+package cart
+
+import (
+	"fmt"
+
+	messages "git.k6n.net/go-cart-actor/proto/cart"
+)
+
+func ClearCart(g *CartGrain, m *messages.ClearCartRequest) error {
+	if m == nil {
+		return fmt.Errorf("ClearCart: nil payload")
+	}
+	if g.CheckoutStatus != nil {
+		return fmt.Errorf("ClearCart: cart is in checkout")
+	}
+	// Clear items, vouchers, etc., but keep userId, etc.
+	g.Items = g.Items[:0]
+	g.Vouchers = g.Vouchers[:0]
+	g.Notifications = g.Notifications[:0]
+	g.OrderReference = ""
+	g.Processing = false
+
+	// g.InventoryReserved = false maybe should release inventory
+	g.UpdateTotals()
+	return nil
+}

pkg/cart/mutation_line_item_marking.go

@@ -0,0 +1,20 @@
+package cart
+
+import (
+	"fmt"
+
+	messages "git.k6n.net/go-cart-actor/proto/cart"
+)
+
+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)
+}

pkg/cart/mutation_remove_item.go

@@ -0,0 +1,57 @@
+package cart
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"time"
+
+	messages "git.k6n.net/go-cart-actor/proto/cart"
+)
+
+// mutation_remove_item.go
+//
+// Registers the RemoveItem mutation.
+//
+// Behavior:
+//   - Removes the cart line whose local cart line Id == payload.Id
+//   - If no such line exists returns an error
+//   - Recalculates cart totals (WithTotals)
+//
+// Notes:
+//   - This removes only the line item; any deliveries referencing the removed
+//     item are NOT automatically adjusted (mirrors prior logic). If future
+//     semantics require pruning delivery.item_ids you can extend this handler.
+//   - If multiple lines somehow shared the same Id (should not happen), only
+//     the first match would be removed—data integrity relies on unique line Ids.
+
+func (c *CartMutationContext) RemoveItem(g *CartGrain, m *messages.RemoveItem) error {
+	if m == nil {
+		return fmt.Errorf("RemoveItem: nil payload")
+	}
+
+	targetID := uint32(m.Id)
+
+	index := -1
+	for i, it := range g.Items {
+		if it.Id == targetID {
+			index = i
+			break
+		}
+	}
+	if index == -1 {
+		return fmt.Errorf("RemoveItem: item id %d not found", m.Id)
+	}
+
+	item := g.Items[index]
+	if item.ReservationEndTime != nil && item.ReservationEndTime.After(time.Now()) {
+		err := c.ReleaseItem(context.Background(), g.Id, item.Sku, item.StoreId)
+		if err != nil {
+			log.Printf("unable to release item reservation")
+		}
+	}
+
+	g.Items = append(g.Items[:index], g.Items[index+1:]...)
+	g.UpdateTotals()
+	return nil
+}

pkg/cart/mutation_remove_line_item_marking.go

@@ -0,0 +1,18 @@
+package cart
+
+import (
+	"fmt"
+
+	messages "git.k6n.net/go-cart-actor/proto/cart"
+)
+
+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)
+}

pkg/cart/mutation_set_user_id.go

@@ -0,0 +1,15 @@
+package cart
+
+import (
+	"errors"
+
+	messages "git.k6n.net/go-cart-actor/proto/cart"
+)
+
+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
+}

pkg/cart/mutation_subscription_added.go

@@ -0,0 +1,20 @@
+package cart
+
+import (
+	"fmt"
+
+	messages "git.k6n.net/go-cart-actor/proto/cart"
+)
+
+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)
+}

pkg/cart/mutation_upsert_subscriptiondetails.go

@@ -0,0 +1,65 @@
+package cart
+
+import (
+	"encoding/json"
+	"fmt"
+
+	messages "git.k6n.net/go-cart-actor/proto/cart"
+)
+
+func UpsertSubscriptionDetails(g *CartGrain, m *messages.UpsertSubscriptionDetails) error {
+	if m == nil {
+		return nil
+	}
+
+	metaBytes := m.Data.GetValue()
+
+	// Create new subscription details when Id is nil.
+	if m.Id == nil {
+		// Validate JSON if provided.
+		var meta json.RawMessage
+		if metaBytes != nil {
+			if !json.Valid(metaBytes) {
+				return fmt.Errorf("subscription details invalid json")
+			}
+			meta = json.RawMessage(metaBytes)
+		}
+
+		id := MustNewCartId().String()
+
+		g.SubscriptionDetails[id] = &SubscriptionDetails{
+			Id:           id,
+			Version:      1,
+			OfferingCode: m.OfferingCode,
+			SigningType:  m.SigningType,
+			Meta:         meta,
+		}
+		return nil
+	}
+
+	// Update existing entry.
+	existing, ok := g.SubscriptionDetails[*m.Id]
+	if !ok {
+		return fmt.Errorf("subscription details with id %s not found", *m.Id)
+	}
+	changed := false
+	if m.OfferingCode != "" {
+		existing.OfferingCode = m.OfferingCode
+		changed = true
+	}
+	if m.SigningType != "" {
+		existing.SigningType = m.SigningType
+		changed = true
+	}
+	if metaBytes != nil {
+		if !json.Valid(metaBytes) {
+			return fmt.Errorf("subscription details invalid json")
+		}
+		existing.Meta = json.RawMessage(metaBytes)
+		changed = true
+	}
+	if changed {
+		existing.Version++
+	}
+	return nil
+}

pkg/cart/price.go

@@ -0,0 +1,159 @@
+package cart
+
+import (
+	"encoding/json"
+	"strconv"
+)
+
+func GetTaxAmount(total int64, tax int) int64 {
+	taxD := 10000 / float64(tax)
+	return int64(float64(total) / float64((1 + taxD)))
+}
+
+type Price struct {
+	IncVat   int64             `json:"incVat"`
+	VatRates map[float32]int64 `json:"vat,omitempty"`
+}
+
+func NewPrice() *Price {
+	return &Price{
+		IncVat:   0,
+		VatRates: make(map[float32]int64),
+	}
+}
+
+func NewPriceFromIncVat(incVat int64, taxRate float32) *Price {
+	tax := GetTaxAmount(incVat, int(taxRate*100))
+	return &Price{
+		IncVat: incVat,
+		VatRates: map[float32]int64{
+			taxRate: tax,
+		},
+	}
+}
+
+func (p *Price) ValueExVat() int64 {
+	exVat := p.IncVat
+	for _, amount := range p.VatRates {
+		exVat -= amount
+	}
+	return exVat
+}
+
+func (p *Price) TotalVat() int64 {
+	total := int64(0)
+	for _, amount := range p.VatRates {
+		total += amount
+	}
+	return total
+}
+
+func MultiplyPrice(p Price, qty int64) *Price {
+	ret := &Price{
+		IncVat:   p.IncVat * qty,
+		VatRates: make(map[float32]int64),
+	}
+	for rate, amount := range p.VatRates {
+		ret.VatRates[rate] = amount * qty
+	}
+	return ret
+}
+
+func (p *Price) Multiply(qty int64) {
+	p.IncVat *= qty
+	for rate, amount := range p.VatRates {
+		p.VatRates[rate] = amount * qty
+	}
+}
+
+func (p Price) MarshalJSON() ([]byte, error) {
+	// Build a stable wire format without calling Price.MarshalJSON recursively
+	exVat := p.ValueExVat()
+	var vat map[string]int64
+	if len(p.VatRates) > 0 {
+		vat = make(map[string]int64, len(p.VatRates))
+		for rate, amount := range p.VatRates {
+			// Rely on default formatting that trims trailing zeros for whole numbers
+			// Using %g could output scientific notation for large numbers; float32 rates here are small.
+			key := trimFloat(rate)
+			vat[key] = amount
+		}
+	}
+	type wire struct {
+		ExVat  int64            `json:"exVat"`
+		IncVat int64            `json:"incVat"`
+		Vat    map[string]int64 `json:"vat,omitempty"`
+	}
+	return json.Marshal(wire{ExVat: exVat, IncVat: p.IncVat, Vat: vat})
+}
+
+func (p *Price) UnmarshalJSON(data []byte) error {
+	type wire struct {
+		ExVat  int64            `json:"exVat"`
+		IncVat int64            `json:"incVat"`
+		Vat    map[string]int64 `json:"vat,omitempty"`
+	}
+	var w wire
+	if err := json.Unmarshal(data, &w); err != nil {
+		return err
+	}
+
+	p.IncVat = w.IncVat
+	if len(w.Vat) > 0 {
+		p.VatRates = make(map[float32]int64, len(w.Vat))
+		for rateStr, amount := range w.Vat {
+			rate, err := strconv.ParseFloat(rateStr, 32)
+			if err != nil {
+				return err
+			}
+			p.VatRates[float32(rate)] = amount
+		}
+	} else {
+		p.VatRates = make(map[float32]int64)
+	}
+
+	return nil
+}
+
+// trimFloat converts a float32 tax rate like 25 or 12.5 into a compact string without
+// unnecessary decimals ("25", "12.5").
+func trimFloat(f float32) string {
+	// Convert via FormatFloat then trim trailing zeros and dot.
+	s := strconv.FormatFloat(float64(f), 'f', -1, 32)
+	return s
+}
+
+func (p *Price) Add(price Price) {
+	p.IncVat += price.IncVat
+	for rate, amount := range price.VatRates {
+		p.VatRates[rate] += amount
+	}
+}
+
+func (p *Price) Subtract(price Price) {
+	p.IncVat -= price.IncVat
+	for rate, amount := range price.VatRates {
+		p.VatRates[rate] -= amount
+	}
+}
+
+func SumPrices(prices ...Price) *Price {
+	if len(prices) == 0 {
+		return NewPrice()
+	}
+
+	aggregated := NewPrice()
+
+	for _, price := range prices {
+		aggregated.IncVat += price.IncVat
+		for rate, amount := range price.VatRates {
+			aggregated.VatRates[rate] += amount
+		}
+	}
+
+	if len(aggregated.VatRates) == 0 {
+		aggregated.VatRates = nil
+	}
+
+	return aggregated
+}

pkg/cart/price_test.go

@@ -0,0 +1,238 @@
+package cart
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestPriceMarshalJSON(t *testing.T) {
+	p := Price{IncVat: 13700, VatRates: map[float32]int64{25: 2500, 12: 1200}}
+	// ExVat = 13700 - (2500+1200) = 10000
+	data, err := json.Marshal(p)
+	if err != nil {
+		t.Fatalf("marshal error: %v", err)
+	}
+	// Unmarshal into a generic struct to validate fields
+	var out struct {
+		ExVat  int64            `json:"exVat"`
+		IncVat int64            `json:"incVat"`
+		Vat    map[string]int64 `json:"vat"`
+	}
+	if err := json.Unmarshal(data, &out); err != nil {
+		t.Fatalf("unmarshal error: %v", err)
+	}
+	if out.ExVat != 10000 {
+		t.Fatalf("expected exVat 10000 got %d", out.ExVat)
+	}
+	if out.IncVat != 13700 {
+		t.Fatalf("expected incVat 13700 got %d", out.IncVat)
+	}
+	if out.Vat["25"] != 2500 || out.Vat["12"] != 1200 {
+		t.Fatalf("unexpected vat map: %#v", out.Vat)
+	}
+}
+
+func TestNewPriceFromIncVat(t *testing.T) {
+	p := NewPriceFromIncVat(1250, 25)
+	if p.IncVat != 1250 {
+		t.Fatalf("expected IncVat %d got %d", 1250, p.IncVat)
+	}
+	if p.VatRates[25] != 250 {
+		t.Fatalf("expected VAT 25 rate %d got %d", 250, p.VatRates[25])
+	}
+	if p.ValueExVat() != 1000 {
+		t.Fatalf("expected exVat %d got %d", 750, p.ValueExVat())
+	}
+}
+
+func TestSumPrices(t *testing.T) {
+	// We'll construct prices via raw struct since constructor expects tax math.
+	// IncVat already includes vat portions.
+	a := Price{IncVat: 1250, VatRates: map[float32]int64{25: 250}}          // ex=1000
+	b := Price{IncVat: 2740, VatRates: map[float32]int64{25: 500, 12: 240}} // ex=2000
+	c := Price{IncVat: 0, VatRates: nil}
+
+	sum := SumPrices(a, b, c)
+
+	if sum.IncVat != 3990 { // 1250+2740
+		t.Fatalf("expected incVat 3990 got %d", sum.IncVat)
+	}
+	if len(sum.VatRates) != 2 {
+		t.Fatalf("expected 2 vat rates got %d", len(sum.VatRates))
+	}
+	if sum.VatRates[25] != 750 {
+		t.Fatalf("expected 25%% vat 750 got %d", sum.VatRates[25])
+	}
+	if sum.VatRates[12] != 240 {
+		t.Fatalf("expected 12%% vat 240 got %d", sum.VatRates[12])
+	}
+	if sum.ValueExVat() != 3000 { // 3990 - (750+240)
+		t.Fatalf("expected exVat 3000 got %d", sum.ValueExVat())
+	}
+}
+
+func TestSumPricesEmpty(t *testing.T) {
+	sum := SumPrices()
+	if sum.IncVat != 0 || sum.VatRates == nil { // constructor sets empty map
+		t.Fatalf("expected zero price got %#v", sum)
+	}
+}
+
+func TestMultiplyPriceFunction(t *testing.T) {
+	base := Price{IncVat: 1250, VatRates: map[float32]int64{25: 250}}
+	multiplied := MultiplyPrice(base, 3)
+	if multiplied.IncVat != 1250*3 {
+		t.Fatalf("expected IncVat %d got %d", 1250*3, multiplied.IncVat)
+	}
+	if multiplied.VatRates[25] != 250*3 {
+		t.Fatalf("expected VAT 25 rate %d got %d", 250*3, multiplied.VatRates[25])
+	}
+	if multiplied.ValueExVat() != (1250-250)*3 {
+		t.Fatalf("expected exVat %d got %d", (1250-250)*3, multiplied.ValueExVat())
+	}
+}
+
+func TestPriceAddSubtract(t *testing.T) {
+	a := Price{IncVat: 1000, VatRates: map[float32]int64{25: 200}}
+	b := Price{IncVat: 500, VatRates: map[float32]int64{25: 100, 12: 54}}
+
+	acc := NewPrice()
+	acc.Add(a)
+	acc.Add(b)
+
+	if acc.IncVat != 1500 {
+		t.Fatalf("expected IncVat 1500 got %d", acc.IncVat)
+	}
+	if acc.VatRates[25] != 300 || acc.VatRates[12] != 54 {
+		t.Fatalf("unexpected VAT map: %#v", acc.VatRates)
+	}
+
+	// Subtract b then a returns to zero
+	acc.Subtract(b)
+	acc.Subtract(a)
+	if acc.IncVat != 0 {
+		t.Fatalf("expected IncVat 0 got %d", acc.IncVat)
+	}
+	if len(acc.VatRates) != 2 || acc.VatRates[25] != 0 || acc.VatRates[12] != 0 {
+		t.Fatalf("expected zeroed vat rates got %#v", acc.VatRates)
+	}
+}
+
+func TestPriceMultiplyMethod(t *testing.T) {
+	p := Price{IncVat: 2000, VatRates: map[float32]int64{25: 400}}
+	// Value before multiply
+	exBefore := p.ValueExVat()
+	p.Multiply(2)
+	if p.IncVat != 4000 {
+		t.Fatalf("expected IncVat 4000 got %d", p.IncVat)
+	}
+	if p.VatRates[25] != 800 {
+		t.Fatalf("expected VAT 800 got %d", p.VatRates[25])
+	}
+	if p.ValueExVat() != exBefore*2 {
+		t.Fatalf("expected exVat %d got %d", exBefore*2, p.ValueExVat())
+	}
+}
+
+func TestGetTaxAmount(t *testing.T) {
+	tests := []struct {
+		total    int64
+		tax      int
+		expected int64
+		desc     string
+	}{
+		{1250, 2500, 250, "25% VAT"}, // 1250 / (1 + 100/25) = 1250 / 5 = 250
+		{1000, 2000, 166, "20% VAT"}, // 1000 / (1 + 100/20) = 1000 / 6 ≈ 166
+		{1200, 2500, 240, "25% VAT on 1200"},
+		{0, 2500, 0, "zero total"},
+		{100, 1000, 9, "10% VAT"},    // tax=1000 for 10%, 100 / (1 + 100/10) = 100 / 11 ≈ 9
+		{100, 10000, 50, "100% VAT"}, // tax=10000 for 100%, 100 / (1 + 100/100) = 100 / 2 = 50
+	}
+
+	for _, tt := range tests {
+		result := GetTaxAmount(tt.total, tt.tax)
+		if result != tt.expected {
+			t.Errorf("GetTaxAmount(%d, %d) [%s] = %d; expected %d", tt.total, tt.tax, tt.desc, result, tt.expected)
+		}
+	}
+}
+
+func TestNewPriceFromIncVatEdgeCases(t *testing.T) {
+	// Zero VAT rate
+	p := NewPriceFromIncVat(1000, 0)
+	if p.IncVat != 1000 {
+		t.Errorf("expected IncVat 1000, got %d", p.IncVat)
+	}
+	if len(p.VatRates) != 1 || p.VatRates[0] != 0 {
+		t.Errorf("expected VAT 0 for rate 0, got %v", p.VatRates)
+	}
+	if p.ValueExVat() != 1000 {
+		t.Errorf("expected exVat 1000, got %d", p.ValueExVat())
+	}
+
+	// High VAT rate, e.g., 50%
+	p = NewPriceFromIncVat(1500, 50)
+	expectedVat := int64(1500 / (1 + 100/50)) // 1500 / 3 = 500
+	if p.VatRates[50] != expectedVat {
+		t.Errorf("expected VAT %d for 50%%, got %d", expectedVat, p.VatRates[50])
+	}
+	if p.ValueExVat() != 1500-expectedVat {
+		t.Errorf("expected exVat %d, got %d", 1500-expectedVat, p.ValueExVat())
+	}
+}
+
+func TestPriceValueExVatAndTotalVat(t *testing.T) {
+	p := Price{IncVat: 13700, VatRates: map[float32]int64{25: 2500, 12: 1200}}
+	exVat := p.ValueExVat()
+	totalVat := p.TotalVat()
+	if exVat != 10000 {
+		t.Errorf("expected exVat 10000, got %d", exVat)
+	}
+	if totalVat != 3700 {
+		t.Errorf("expected totalVat 3700, got %d", totalVat)
+	}
+	if exVat+totalVat != p.IncVat {
+		t.Errorf("exVat + totalVat should equal IncVat: %d + %d != %d", exVat, totalVat, p.IncVat)
+	}
+
+	// Empty VAT rates
+	p2 := Price{IncVat: 500, VatRates: nil}
+	if p2.ValueExVat() != 500 {
+		t.Errorf("expected exVat 500 for no VAT, got %d", p2.ValueExVat())
+	}
+	if p2.TotalVat() != 0 {
+		t.Errorf("expected totalVat 0, got %d", p2.TotalVat())
+	}
+}
+
+func TestMultiplyPriceWithZeroQty(t *testing.T) {
+	base := Price{IncVat: 1250, VatRates: map[float32]int64{25: 250}}
+	multiplied := MultiplyPrice(base, 0)
+	if multiplied.IncVat != 0 {
+		t.Errorf("expected IncVat 0, got %d", multiplied.IncVat)
+	}
+	if len(multiplied.VatRates) != 1 || multiplied.VatRates[25] != 0 {
+		t.Errorf("expected VAT 0, got %v", multiplied.VatRates)
+	}
+}
+
+func TestPriceAddSubtractEdgeCases(t *testing.T) {
+	a := Price{IncVat: 1000, VatRates: map[float32]int64{25: 200}}
+	b := Price{IncVat: 500, VatRates: map[float32]int64{12: 54}} // Different rate
+
+	acc := NewPrice()
+	acc.Add(a)
+	acc.Add(b)
+
+	if acc.VatRates[25] != 200 || acc.VatRates[12] != 54 {
+		t.Errorf("expected VAT 25:200, 12:54, got %v", acc.VatRates)
+	}
+
+	// Subtract more than added (negative VAT)
+	acc.Subtract(a)
+	acc.Subtract(b)
+	acc.Subtract(a) // Subtract extra a
+	if acc.VatRates[25] != -200 || acc.VatRates[12] != 0 {
+		t.Errorf("expected negative VAT for 25 after over-subtract, got %v", acc.VatRates)
+	}
+}

pkg/checkout/checkout-grain.go

@@ -0,0 +1,195 @@
+package checkout
+
+import (
+	"encoding/json"
+	"sync"
+	"time"
+
+	"git.k6n.net/go-cart-actor/pkg/cart"
+)
+
+// CheckoutId is the same as CartId for simplicity
+type CheckoutId = cart.CartId
+
+type PickupPoint struct {
+	DeliveryId uint32  `json:"deliveryId,omitempty"`
+	Id         string  `json:"id"`
+	Name       *string `json:"name,omitempty"`
+	Address    *string `json:"address,omitempty"`
+	City       *string `json:"city,omitempty"`
+	Zip        *string `json:"zip,omitempty"`
+	Country    *string `json:"country,omitempty"`
+}
+
+type CheckoutDelivery struct {
+	Id          uint32       `json:"id"`
+	Provider    string       `json:"provider"`
+	Price       cart.Price   `json:"price"`
+	Items       []uint32     `json:"items"`
+	PickupPoint *PickupPoint `json:"pickupPoint,omitempty"`
+}
+type PaymentStatus string
+type CheckoutPaymentStatus PaymentStatus
+
+const (
+	PaymentStatusPending           PaymentStatus         = "pending"
+	PaymentStatusFailed            PaymentStatus         = "failed"
+	PaymentStatusSuccess           PaymentStatus         = "success"
+	CheckoutPaymentStatusPending   CheckoutPaymentStatus = "pending"
+	CheckoutPaymentStatusFailed    CheckoutPaymentStatus = "failed"
+	CheckoutPaymentStatusSuccess   CheckoutPaymentStatus = "success"
+	CheckoutPaymentStatusCancelled CheckoutPaymentStatus = "partial"
+)
+
+type Payment struct {
+	PaymentId          string           `json:"paymentId"`
+	Status             PaymentStatus    `json:"status"`
+	Amount             int64            `json:"amount"`
+	Currency           string           `json:"currency"`
+	Provider           string           `json:"provider,omitempty"`
+	Method             *string          `json:"method,omitempty"`
+	SessionData        *json.RawMessage `json:"sessionData,omitempty"`
+	Events             []PaymentEvent   `json:"events,omitempty"`
+	ProcessorReference *string          `json:"processorReference,omitempty"`
+	StartedAt          *time.Time       `json:"startedAt,omitempty"`
+	CompletedAt        *time.Time       `json:"completedAt,omitempty"`
+}
+
+type PaymentEvent struct {
+	Name    string          `json:"name"`
+	Success bool            `json:"success"`
+	Data    json.RawMessage `json:"data"`
+}
+
+func (p *Payment) IsSettled() bool {
+	if p == nil {
+		return false
+	}
+
+	switch p.Status {
+	case PaymentStatusSuccess:
+		return true
+	default:
+		return false
+	}
+}
+
+type ContactDetails struct {
+	Email *string `json:"email,omitempty"`
+	Phone *string `json:"phone,omitempty"`
+	Name  *string `json:"name,omitempty"`
+}
+
+type ConfirmationStatus struct {
+	Code         *string   `json:"code,omitempty"`
+	ViewCount    int       `json:"viewCount"`
+	LastViewedAt time.Time `json:"lastViewedAt"`
+}
+
+type CheckoutGrain struct {
+	mu                sync.RWMutex
+	lastDeliveryId    uint32
+	lastGiftcardId    uint32
+	lastAccess        time.Time
+	lastChange        time.Time
+	Version           uint32              `json:"version"`
+	Id                CheckoutId          `json:"id"`
+	CartId            cart.CartId         `json:"cartId"`
+	CartVersion       uint64              `json:"cartVersion"`
+	CartState         *cart.CartGrain     `json:"cartState"` // snapshot of items
+	CartTotalPrice    *cart.Price         `json:"cartTotalPrice"`
+	OrderId           *string             `json:"orderId"`
+	Deliveries        []*CheckoutDelivery `json:"deliveries,omitempty"`
+	PaymentInProgress uint16              `json:"paymentInProgress"`
+	InventoryReserved bool                `json:"inventoryReserved"`
+	Confirmation      *ConfirmationStatus `json:"confirmationViewed,omitempty"`
+	Payments          []*Payment          `json:"payments,omitempty"`
+	ContactDetails    *ContactDetails     `json:"contactDetails,omitempty"`
+}
+
+func NewCheckoutGrain(id uint64, cartId cart.CartId, cartVersion uint64, ts time.Time, cartState *cart.CartGrain) *CheckoutGrain {
+	r := &CheckoutGrain{
+		lastDeliveryId: 0,
+		lastGiftcardId: 0,
+		lastAccess:     ts,
+		lastChange:     ts,
+		Id:             CheckoutId(id),
+		CartId:         cartId,
+		CartVersion:    cartVersion,
+		Deliveries:     []*CheckoutDelivery{},
+		Payments:       []*Payment{},
+	}
+	if cartState != nil {
+		r.CartState = cartState
+		r.CartTotalPrice = cartState.TotalPrice
+	}
+	return r
+}
+
+func (c *CheckoutGrain) GetId() uint64 {
+	return uint64(c.Id)
+}
+
+func (c *CheckoutGrain) GetLastChange() time.Time {
+	return c.lastChange
+}
+
+func (c *CheckoutGrain) GetLastAccess() time.Time {
+	return c.lastAccess
+}
+
+func (c *CheckoutGrain) GetCurrentState() (*CheckoutGrain, error) {
+	c.lastAccess = time.Now()
+	return c, nil
+}
+
+func (c *CheckoutGrain) GetState() ([]byte, error) {
+	return json.Marshal(c)
+}
+
+func (c *CheckoutGrain) FindPayment(paymentId string) (*Payment, bool) {
+	if paymentId == "" {
+		return nil, false
+	}
+	for _, payment := range c.Payments {
+		if payment != nil && payment.PaymentId == paymentId {
+			return payment, true
+		}
+	}
+	return nil, false
+}
+
+func (c *CheckoutGrain) SettledPayments() []*Payment {
+	if len(c.Payments) == 0 {
+		return nil
+	}
+	settled := make([]*Payment, 0, len(c.Payments))
+	for _, payment := range c.Payments {
+		if payment != nil && payment.IsSettled() {
+			settled = append(settled, payment)
+		}
+	}
+	if len(settled) == 0 {
+		return nil
+	}
+	return settled
+}
+
+func (c *CheckoutGrain) OpenPayments() []*Payment {
+	if len(c.Payments) == 0 {
+		return nil
+	}
+	pending := make([]*Payment, 0, len(c.Payments))
+	for _, payment := range c.Payments {
+		if payment == nil {
+			continue
+		}
+		if !payment.IsSettled() {
+			pending = append(pending, payment)
+		}
+	}
+	if len(pending) == 0 {
+		return nil
+	}
+	return pending
+}

pkg/checkout/mutation-context.go

@@ -0,0 +1,32 @@
+package checkout
+
+import (
+	"git.k6n.net/go-cart-actor/pkg/actor"
+)
+
+type CheckoutMutationContext struct {
+	// Add any services needed, e.g., for delivery calculations, but since inventory is pre-handled, maybe none
+}
+
+func NewCheckoutMutationContext() *CheckoutMutationContext {
+	return &CheckoutMutationContext{}
+}
+
+func NewCheckoutMutationRegistry(ctx *CheckoutMutationContext) actor.MutationRegistry {
+	reg := actor.NewMutationRegistry()
+	reg.RegisterMutations(
+		actor.NewMutation(HandleInitializeCheckout),
+		actor.NewMutation(HandlePaymentStarted),
+		actor.NewMutation(HandlePaymentCompleted),
+		actor.NewMutation(HandlePaymentDeclined),
+		actor.NewMutation(HandlePaymentEvent),
+		actor.NewMutation(HandleConfirmationViewed),
+		actor.NewMutation(HandleOrderCreated),
+		actor.NewMutation(HandleInventoryReserved),
+		actor.NewMutation(HandleSetDelivery),
+		actor.NewMutation(HandleSetPickupPoint),
+		actor.NewMutation(HandleRemoveDelivery),
+		actor.NewMutation(HandleContactDetailsUpdated),
+	)
+	return reg
+}

pkg/checkout/mutation_confirmation_viewed.go

@@ -0,0 +1,26 @@
+package checkout
+
+import (
+	"fmt"
+	"time"
+
+	messages "git.k6n.net/go-cart-actor/proto/checkout"
+)
+
+func HandleConfirmationViewed(g *CheckoutGrain, m *messages.ConfirmationViewed) error {
+	if m == nil {
+		return fmt.Errorf("ConfirmationViewed: nil payload")
+	}
+
+	if g.Confirmation != nil {
+		g.Confirmation = &ConfirmationStatus{
+			ViewCount:    1,
+			LastViewedAt: time.Now(),
+		}
+	} else {
+		g.Confirmation.ViewCount++
+		g.Confirmation.LastViewedAt = time.Now()
+	}
+
+	return nil
+}