handle dynamic json data and examples for subscription details

2025-10-16 12:09:47 +02:00
parent 8682daf481
commit 9ab0c08e79
13 changed files with 934 additions and 307 deletions
--- a/pkg/cart/cart-grain.go
+++ b/pkg/cart/cart-grain.go
@@ -61,25 +61,33 @@ type CartNotification struct {
 	Content  string `json:"content"`
 }

+type SubscriptionDetails struct {
+	Id           string          `json:"id"`
+	OfferingCode string          `json:"offeringCode,omitempty"`
+	SigningType  string          `json:"signingType,omitempty"`
+	Meta         json.RawMessage `json:"data,omitempty"`
+}
+
 type CartGrain struct {
-	mu                sync.RWMutex
-	lastItemId        uint32
-	lastDeliveryId    uint32
-	lastVoucherId     uint32
-	lastAccess        time.Time
-	lastChange        time.Time // unix seconds of last successful mutation (replay sets from event ts)
-	userId            string
-	Id                CartId             `json:"id"`
-	Items             []*CartItem        `json:"items"`
-	TotalPrice        *Price             `json:"totalPrice"`
-	TotalDiscount     *Price             `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"`
-	Vouchers          []*Voucher         `json:"vouchers,omitempty"`
-	Notifications     []CartNotification `json:"cartNotification,omitempty"`
+	mu                  sync.RWMutex
+	lastItemId          uint32
+	lastDeliveryId      uint32
+	lastVoucherId       uint32
+	lastAccess          time.Time
+	lastChange          time.Time // unix seconds of last successful mutation (replay sets from event ts)
+	userId              string
+	Id                  CartId                          `json:"id"`
+	Items               []*CartItem                     `json:"items"`
+	TotalPrice          *Price                          `json:"totalPrice"`
+	TotalDiscount       *Price                          `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"`
+	Vouchers            []*Voucher                      `json:"vouchers,omitempty"`
+	Notifications       []CartNotification              `json:"cartNotification,omitempty"`
+	SubscriptionDetails map[string]*SubscriptionDetails `json:"subscriptionDetails,omitempty"`
 }

 type Voucher struct {
@@ -139,17 +147,18 @@ func (v *Voucher) AppliesTo(cart *CartGrain) ([]*CartItem, bool) {

 func NewCartGrain(id uint64, ts time.Time) *CartGrain {
 	return &CartGrain{
-		lastItemId:     0,
-		lastDeliveryId: 0,
-		lastVoucherId:  0,
-		lastAccess:     ts,
-		lastChange:     ts,
-		TotalDiscount:  NewPrice(),
-		Vouchers:       []*Voucher{},
-		Deliveries:     []*CartDelivery{},
-		Id:             CartId(id),
-		Items:          []*CartItem{},
-		TotalPrice:     NewPrice(),
+		lastItemId:          0,
+		lastDeliveryId:      0,
+		lastVoucherId:       0,
+		lastAccess:          ts,
+		lastChange:          ts,
+		TotalDiscount:       NewPrice(),
+		Vouchers:            []*Voucher{},
+		Deliveries:          []*CartDelivery{},
+		Id:                  CartId(id),
+		Items:               []*CartItem{},
+		TotalPrice:          NewPrice(),
+		SubscriptionDetails: make(map[string]*SubscriptionDetails),
 	}
 }

--- a/pkg/cart/cart-mutation-helper.go
+++ b/pkg/cart/cart-mutation-helper.go
@@ -42,6 +42,9 @@ func NewCartMultationRegistry() actor.MutationRegistry {
 		actor.NewMutation(RemoveVoucher, func() *messages.RemoveVoucher {
 			return &messages.RemoveVoucher{}
 		}),
+		actor.NewMutation(UpsertSubscriptionDetails, func() *messages.UpsertSubscriptionDetails {
+			return &messages.UpsertSubscriptionDetails{}
+		}),
 	)
 	return reg

--- a/pkg/cart/mutation_add_item.go
+++ b/pkg/cart/mutation_add_item.go
@@ -28,14 +28,23 @@ func AddItem(g *CartGrain, m *messages.AddItem) error {
 		return fmt.Errorf("AddItem: invalid quantity %d", m.Quantity)
 	}

-	// Fast path: merge with existing item having same SKU
-	if existing, found := g.FindItemWithSku(m.Sku); found {
-		if existing.StoreId == m.StoreId {
-			existing.Quantity += int(m.Quantity)
-			existing.Stock = StockStatus(m.Stock)
-			existing.StoreId = m.StoreId
-			return nil
+	// 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
+		}
+		existing.Quantity += int(m.Quantity)
+		existing.Stock = StockStatus(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()
--- a/pkg/cart/mutation_test.go
+++ b/pkg/cart/mutation_test.go
@@ -0,0 +1,520 @@
+package cart
+
+import (
+	"reflect"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/gogo/protobuf/proto"
+	anypb "google.golang.org/protobuf/types/known/anypb"
+
+	"git.tornberg.me/go-cart-actor/pkg/actor"
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+)
+
+// ----------------------
+// Helper constructors
+// ----------------------
+
+func newTestGrain() *CartGrain {
+	return NewCartGrain(123, time.Now())
+}
+
+func newRegistry() actor.MutationRegistry {
+	return NewCartMultationRegistry()
+}
+
+func msgAddItem(sku string, price int64, qty int32, storePtr *string) *messages.AddItem {
+	return &messages.AddItem{
+		Sku:      sku,
+		Price:    price,
+		Quantity: qty,
+		// Tax left 0 -> handler uses default 25%
+		StoreId: storePtr,
+	}
+}
+
+func msgChangeQty(id uint32, qty int32) *messages.ChangeQuantity {
+	return &messages.ChangeQuantity{Id: id, Quantity: qty}
+}
+
+func msgRemoveItem(id uint32) *messages.RemoveItem {
+	return &messages.RemoveItem{Id: id}
+}
+
+func msgSetDelivery(provider string, items ...uint32) *messages.SetDelivery {
+	uitems := make([]uint32, len(items))
+	copy(uitems, items)
+	return &messages.SetDelivery{Provider: provider, Items: uitems}
+}
+
+func msgSetPickupPoint(deliveryId uint32, id string) *messages.SetPickupPoint {
+	return &messages.SetPickupPoint{
+		DeliveryId: deliveryId,
+		Id:         id,
+		Name:       ptr("Pickup"),
+		Address:    ptr("Street 1"),
+		City:       ptr("Town"),
+		Zip:        ptr("12345"),
+		Country:    ptr("SE"),
+	}
+}
+
+func msgClearCart() *messages.ClearCartRequest {
+	return &messages.ClearCartRequest{}
+}
+
+func msgAddVoucher(code string, value int64, rules ...*messages.VoucherRule) *messages.AddVoucher {
+	return &messages.AddVoucher{Code: code, Value: value, VoucherRules: rules}
+}
+
+func msgRemoveVoucher(id uint32) *messages.RemoveVoucher {
+	return &messages.RemoveVoucher{Id: id}
+}
+
+func msgInitializeCheckout(orderId, status string, inProgress bool) *messages.InitializeCheckout {
+	return &messages.InitializeCheckout{OrderId: orderId, Status: status, PaymentInProgress: inProgress}
+}
+
+func msgOrderCreated(orderId, status string) *messages.OrderCreated {
+	return &messages.OrderCreated{OrderId: orderId, Status: status}
+}
+
+func ptr[T any](v T) *T { return &v }
+
+// ----------------------
+// Apply helpers
+// ----------------------
+
+func applyOne(t *testing.T, reg actor.MutationRegistry, g *CartGrain, msg proto.Message) actor.ApplyResult {
+	t.Helper()
+	results, err := reg.Apply(g, msg)
+	if err != nil {
+		t.Fatalf("unexpected registry-level error applying %T: %v", msg, err)
+	}
+	if len(results) != 1 {
+		t.Fatalf("expected exactly one ApplyResult, got %d", len(results))
+	}
+	return results[0]
+}
+
+// Expect success (nil error inside ApplyResult).
+func applyOK(t *testing.T, reg actor.MutationRegistry, g *CartGrain, msg proto.Message) {
+	t.Helper()
+	res := applyOne(t, reg, g, msg)
+	if res.Error != nil {
+		t.Fatalf("expected mutation %s (%T) to succeed, got error: %v", res.Type, msg, res.Error)
+	}
+}
+
+// Expect an error matching substring.
+func applyErrorContains(t *testing.T, reg actor.MutationRegistry, g *CartGrain, msg proto.Message, substr string) {
+	t.Helper()
+	res := applyOne(t, reg, g, msg)
+	if res.Error == nil {
+		t.Fatalf("expected error applying %T, got nil", msg)
+	}
+	if substr != "" && !strings.Contains(res.Error.Error(), substr) {
+		t.Fatalf("error mismatch, want substring %q got %q", substr, res.Error.Error())
+	}
+}
+
+// ----------------------
+// Tests
+// ----------------------
+
+func TestMutationRegistryCoverage(t *testing.T) {
+	reg := newRegistry()
+
+	expected := []string{
+		"AddItem",
+		"ChangeQuantity",
+		"RemoveItem",
+		"InitializeCheckout",
+		"OrderCreated",
+		"RemoveDelivery",
+		"SetDelivery",
+		"SetPickupPoint",
+		"ClearCartRequest",
+		"AddVoucher",
+		"RemoveVoucher",
+		"UpsertSubscriptionDetails",
+	}
+
+	names := reg.(*actor.ProtoMutationRegistry).RegisteredMutations()
+	for _, want := range expected {
+		if !slices.Contains(names, want) {
+			t.Fatalf("registry missing mutation %s; got %v", want, names)
+		}
+	}
+
+	// Create() by name returns correct concrete type.
+	for _, name := range expected {
+		msg, ok := reg.Create(name)
+		if !ok {
+			t.Fatalf("Create failed for %s", name)
+		}
+		rt := reflect.TypeOf(msg)
+		if rt.Kind() == reflect.Ptr {
+			rt = rt.Elem()
+		}
+		if rt.Name() != name {
+			t.Fatalf("Create(%s) returned wrong type %s", name, rt.Name())
+		}
+	}
+
+	// Unregistered create
+	if m, ok := reg.Create("DoesNotExist"); ok || m != nil {
+		t.Fatalf("Create should fail for unknown; got (%T,%v)", m, ok)
+	}
+
+	// GetTypeName sanity
+	add := &messages.AddItem{}
+	nm, ok := reg.GetTypeName(add)
+	if !ok || nm != "AddItem" {
+		t.Fatalf("GetTypeName failed for AddItem, got (%q,%v)", nm, ok)
+	}
+
+	// Apply unregistered message -> result should contain ErrMutationNotRegistered, no top-level error
+	results, err := reg.Apply(newTestGrain(), &messages.Noop{})
+	if err != nil {
+		t.Fatalf("unexpected top-level error applying unregistered mutation: %v", err)
+	}
+	if len(results) != 1 || results[0].Error == nil || results[0].Error != actor.ErrMutationNotRegistered {
+		t.Fatalf("expected ApplyResult with ErrMutationNotRegistered, got %#v", results)
+	}
+}
+
+func TestAddItemAndMerging(t *testing.T) {
+	reg := newRegistry()
+	g := newTestGrain()
+
+	// Merge scenario (same SKU + same store pointer)
+	add1 := msgAddItem("SKU-1", 1000, 2, nil)
+	applyOK(t, reg, g, add1)
+
+	if len(g.Items) != 1 || g.Items[0].Quantity != 2 {
+		t.Fatalf("expected first item added; items=%d qty=%d", len(g.Items), g.Items[0].Quantity)
+	}
+
+	applyOK(t, reg, g, msgAddItem("SKU-1", 1000, 3, nil)) // should merge
+	if len(g.Items) != 1 || g.Items[0].Quantity != 5 {
+		t.Fatalf("expected merge quantity=5 items=%d qty=%d", len(g.Items), g.Items[0].Quantity)
+	}
+
+	// Different store pointer -> new line
+	store := "S1"
+	applyOK(t, reg, g, msgAddItem("SKU-1", 1000, 1, &store))
+	if len(g.Items) != 2 {
+		t.Fatalf("expected second line for different store pointer; items=%d", len(g.Items))
+	}
+
+	// Same store pointer & SKU -> merge with second line
+	applyOK(t, reg, g, msgAddItem("SKU-1", 1000, 4, &store))
+	if len(g.Items) != 2 || g.Items[1].Quantity != 5 {
+		t.Fatalf("expected merge on second line; items=%d second.qty=%d", len(g.Items), g.Items[1].Quantity)
+	}
+
+	// Invalid quantity
+	applyErrorContains(t, reg, g, msgAddItem("BAD", 1000, 0, nil), "invalid quantity")
+}
+
+func TestChangeQuantityBehavior(t *testing.T) {
+	reg := newRegistry()
+	g := newTestGrain()
+
+	applyOK(t, reg, g, msgAddItem("A", 1500, 2, nil))
+	id := g.Items[0].Id
+
+	// Increase quantity
+	applyOK(t, reg, g, msgChangeQty(id, 5))
+	if g.Items[0].Quantity != 5 {
+		t.Fatalf("quantity not updated expected=5 got=%d", g.Items[0].Quantity)
+	}
+
+	// Remove item by setting <=0
+	applyOK(t, reg, g, msgChangeQty(id, 0))
+	if len(g.Items) != 0 {
+		t.Fatalf("expected item removed; items=%d", len(g.Items))
+	}
+
+	// Not found
+	applyErrorContains(t, reg, g, msgChangeQty(9999, 1), "not found")
+}
+
+func TestRemoveItemBehavior(t *testing.T) {
+	reg := newRegistry()
+	g := newTestGrain()
+
+	applyOK(t, reg, g, msgAddItem("X", 1200, 1, nil))
+	id := g.Items[0].Id
+
+	applyOK(t, reg, g, msgRemoveItem(id))
+	if len(g.Items) != 0 {
+		t.Fatalf("expected item removed; items=%d", len(g.Items))
+	}
+
+	applyErrorContains(t, reg, g, msgRemoveItem(id), "not found")
+}
+
+func TestDeliveryMutations(t *testing.T) {
+	reg := newRegistry()
+	g := newTestGrain()
+
+	applyOK(t, reg, g, msgAddItem("D1", 1000, 1, nil))
+	applyOK(t, reg, g, msgAddItem("D2", 2000, 1, nil))
+	i1 := g.Items[0].Id
+
+	// Explicit items
+	applyOK(t, reg, g, msgSetDelivery("POSTNORD", i1))
+	if len(g.Deliveries) != 1 || len(g.Deliveries[0].Items) != 1 || g.Deliveries[0].Items[0] != i1 {
+		t.Fatalf("delivery not created as expected: %+v", g.Deliveries)
+	}
+
+	// Attempt to attach an already-delivered item
+	applyErrorContains(t, reg, g, msgSetDelivery("POSTNORD", i1), "already has a delivery")
+
+	// Attach remaining item via empty list (auto include items without delivery)
+	applyOK(t, reg, g, msgSetDelivery("DHL"))
+	if len(g.Deliveries) != 2 {
+		t.Fatalf("expected second delivery; deliveries=%d", len(g.Deliveries))
+	}
+
+	// Non-existent item
+	applyErrorContains(t, reg, g, msgSetDelivery("UPS", 99999), "not found")
+
+	// No eligible items left
+	applyErrorContains(t, reg, g, msgSetDelivery("UPS"), "no eligible items")
+
+	// Set pickup point on first delivery
+	did := g.Deliveries[0].Id
+	applyOK(t, reg, g, msgSetPickupPoint(did, "PP1"))
+	if g.Deliveries[0].PickupPoint == nil || g.Deliveries[0].PickupPoint.Id != "PP1" {
+		t.Fatalf("pickup point not set correctly: %+v", g.Deliveries[0].PickupPoint)
+	}
+
+	// Bad delivery id
+	applyErrorContains(t, reg, g, msgSetPickupPoint(9999, "PPX"), "delivery id")
+
+	// Remove delivery
+	applyOK(t, reg, g, &messages.RemoveDelivery{Id: did})
+	if len(g.Deliveries) != 1 || g.Deliveries[0].Id == did {
+		t.Fatalf("expected first delivery removed, remaining: %+v", g.Deliveries)
+	}
+
+	// Remove delivery not found
+	applyErrorContains(t, reg, g, &messages.RemoveDelivery{Id: did}, "not found")
+}
+
+func TestClearCart(t *testing.T) {
+	reg := newRegistry()
+	g := newTestGrain()
+
+	applyOK(t, reg, g, msgAddItem("X", 1000, 2, nil))
+	applyOK(t, reg, g, msgSetDelivery("P", g.Items[0].Id))
+
+	applyOK(t, reg, g, msgClearCart())
+
+	if len(g.Items) != 0 || len(g.Deliveries) != 0 {
+		t.Fatalf("expected cart cleared; items=%d deliveries=%d", len(g.Items), len(g.Deliveries))
+	}
+}
+
+func TestVoucherMutations(t *testing.T) {
+	reg := newRegistry()
+	g := newTestGrain()
+
+	applyOK(t, reg, g, msgAddItem("VOUCH", 10000, 1, nil))
+	applyOK(t, reg, g, msgAddVoucher("PROMO", 5000))
+
+	if len(g.Vouchers) != 1 {
+		t.Fatalf("voucher not stored")
+	}
+	if g.TotalDiscount.IncVat != 5000 {
+		t.Fatalf("expected discount 5000 got %d", g.TotalDiscount.IncVat)
+	}
+	if g.TotalPrice.IncVat != 5000 {
+		t.Fatalf("expected total price 5000 got %d", g.TotalPrice.IncVat)
+	}
+
+	// Duplicate voucher code
+	applyErrorContains(t, reg, g, msgAddVoucher("PROMO", 1000), "already applied")
+
+	// Add a large voucher (should not apply because value > total price)
+	applyOK(t, reg, g, msgAddVoucher("BIG", 100000))
+	if len(g.Vouchers) != 2 {
+		t.Fatalf("expected second voucher stored")
+	}
+	if g.TotalDiscount.IncVat != 5000 || g.TotalPrice.IncVat != 5000 {
+		t.Fatalf("large voucher incorrectly applied discount=%d total=%d",
+			g.TotalDiscount.IncVat, g.TotalPrice.IncVat)
+	}
+
+	// Remove existing voucher
+	firstId := g.Vouchers[0].Id
+	applyOK(t, reg, g, msgRemoveVoucher(firstId))
+
+	if slices.ContainsFunc(g.Vouchers, func(v *Voucher) bool { return v.Id == firstId }) {
+		t.Fatalf("voucher id %d not removed", firstId)
+	}
+	// After removing PROMO, BIG remains but is not applied (exceeds price)
+	if g.TotalDiscount.IncVat != 0 || g.TotalPrice.IncVat != 10000 {
+		t.Fatalf("totals incorrect after removal discount=%d total=%d",
+			g.TotalDiscount.IncVat, g.TotalPrice.IncVat)
+	}
+
+	// Remove not applied
+	applyErrorContains(t, reg, g, msgRemoveVoucher(firstId), "not applied")
+}
+
+func TestCheckoutMutations(t *testing.T) {
+	reg := newRegistry()
+	g := newTestGrain()
+
+	applyOK(t, reg, g, msgInitializeCheckout("ORD-1", "PENDING", true))
+	if g.OrderReference != "ORD-1" || g.PaymentStatus != "PENDING" || !g.PaymentInProgress {
+		t.Fatalf("initialize checkout failed: ref=%s status=%s inProgress=%v",
+			g.OrderReference, g.PaymentStatus, g.PaymentInProgress)
+	}
+
+	applyOK(t, reg, g, msgOrderCreated("ORD-1", "COMPLETED"))
+	if g.OrderReference != "ORD-1" || g.PaymentStatus != "COMPLETED" || g.PaymentInProgress {
+		t.Fatalf("order created mutation failed: ref=%s status=%s inProgress=%v",
+			g.OrderReference, g.PaymentStatus, g.PaymentInProgress)
+	}
+
+	applyErrorContains(t, reg, g, msgInitializeCheckout("", "X", true), "missing orderId")
+	applyErrorContains(t, reg, g, msgOrderCreated("", "X"), "missing orderId")
+}
+
+func TestSubscriptionDetailsMutation(t *testing.T) {
+	reg := newRegistry()
+	g := newTestGrain()
+
+	// Upsert new (Id == nil)
+	msgNew := &messages.UpsertSubscriptionDetails{
+		OfferingCode: "OFF1",
+		SigningType:  "TYPE1",
+	}
+	applyOK(t, reg, g, msgNew)
+	if len(g.SubscriptionDetails) != 1 {
+		t.Fatalf("expected one subscription detail; got=%d", len(g.SubscriptionDetails))
+	}
+
+	// Capture created id
+	var createdId string
+	for k := range g.SubscriptionDetails {
+		createdId = k
+	}
+
+	// Update existing
+	msgUpdate := &messages.UpsertSubscriptionDetails{
+		Id:           &createdId,
+		OfferingCode: "OFF2",
+		SigningType:  "TYPE2",
+	}
+	applyOK(t, reg, g, msgUpdate)
+	if g.SubscriptionDetails[createdId].OfferingCode != "OFF2" ||
+		g.SubscriptionDetails[createdId].SigningType != "TYPE2" {
+		t.Fatalf("subscription details not updated: %+v", g.SubscriptionDetails[createdId])
+	}
+
+	// Update non-existent
+	badId := "NON_EXISTENT"
+	applyErrorContains(t, reg, g, &messages.UpsertSubscriptionDetails{Id: &badId}, "not found")
+
+	// Nil mutation should be ignored and produce zero results.
+	resultsNil, errNil := reg.Apply(g, (*messages.UpsertSubscriptionDetails)(nil))
+	if errNil != nil {
+		t.Fatalf("unexpected error for nil mutation element: %v", errNil)
+	}
+	if len(resultsNil) != 0 {
+		t.Fatalf("expected zero results for nil mutation, got %d", len(resultsNil))
+	}
+}
+
+// Ensure registry Apply handles nil grain and nil message defensive errors consistently.
+func TestRegistryDefensiveErrors(t *testing.T) {
+	reg := newRegistry()
+	g := newTestGrain()
+
+	// Nil grain
+	results, err := reg.Apply(nil, &messages.AddItem{})
+	if err == nil {
+		t.Fatalf("expected error for nil grain")
+	}
+	if len(results) != 0 {
+		t.Fatalf("expected no results for nil grain")
+	}
+
+	// Nil message slice
+	results, _ = reg.Apply(g, nil)
+
+	if len(results) != 0 {
+		t.Fatalf("expected no results when message slice nil")
+	}
+}
+func TestSubscriptionDetailsJSONValidation(t *testing.T) {
+	reg := newRegistry()
+	g := newTestGrain()
+
+	// Valid JSON on create
+	validCreate := &messages.UpsertSubscriptionDetails{
+		OfferingCode: "OFFJSON",
+		SigningType:  "TYPEJSON",
+		Data:         &anypb.Any{Value: []byte(`{"ok":true}`)},
+	}
+	applyOK(t, reg, g, validCreate)
+	if len(g.SubscriptionDetails) != 1 {
+		t.Fatalf("expected one subscription detail after valid create, got %d", len(g.SubscriptionDetails))
+	}
+	var id string
+	for k := range g.SubscriptionDetails {
+		id = k
+	}
+	if string(g.SubscriptionDetails[id].Meta) != `{"ok":true}` {
+		t.Fatalf("expected meta stored as valid json, got %s", string(g.SubscriptionDetails[id].Meta))
+	}
+
+	// Update with valid JSON replaces meta
+	updateValid := &messages.UpsertSubscriptionDetails{
+		Id:   &id,
+		Data: &anypb.Any{Value: []byte(`{"changed":123}`)},
+	}
+	applyOK(t, reg, g, updateValid)
+	if string(g.SubscriptionDetails[id].Meta) != `{"changed":123}` {
+		t.Fatalf("expected meta updated to new json, got %s", string(g.SubscriptionDetails[id].Meta))
+	}
+
+	// Invalid JSON on create
+	invalidCreate := &messages.UpsertSubscriptionDetails{
+		OfferingCode: "BAD",
+		Data:         &anypb.Any{Value: []byte(`{"broken":}`)},
+	}
+	res := applyOne(t, reg, g, invalidCreate)
+	if res.Error == nil || !strings.Contains(res.Error.Error(), "invalid json") {
+		t.Fatalf("expected invalid json error on create, got %v", res.Error)
+	}
+
+	// Invalid JSON on update
+	badUpdate := &messages.UpsertSubscriptionDetails{
+		Id:   &id,
+		Data: &anypb.Any{Value: []byte(`{oops`)},
+	}
+	res2 := applyOne(t, reg, g, badUpdate)
+	if res2.Error == nil || !strings.Contains(res2.Error.Error(), "invalid json") {
+		t.Fatalf("expected invalid json error on update, got %v", res2.Error)
+	}
+
+	// Empty Data.Value should not overwrite existing meta
+	emptyUpdate := &messages.UpsertSubscriptionDetails{
+		Id:   &id,
+		Data: &anypb.Any{Value: []byte{}},
+	}
+	applyOK(t, reg, g, emptyUpdate)
+	if string(g.SubscriptionDetails[id].Meta) != `{"changed":123}` {
+		t.Fatalf("empty update should not change meta, got %s", string(g.SubscriptionDetails[id].Meta))
+	}
+}
--- a/pkg/cart/mutation_upsert_subscriptiondetails.go
+++ b/pkg/cart/mutation_upsert_subscriptiondetails.go
@@ -0,0 +1,57 @@
+package cart
+
+import (
+	"encoding/json"
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+)
+
+func UpsertSubscriptionDetails(g *CartGrain, m *messages.UpsertSubscriptionDetails) error {
+	if m == nil {
+		return nil
+	}
+
+	// Create new subscription details when Id is nil.
+	if m.Id == nil {
+		// Validate JSON if provided.
+		var meta json.RawMessage
+		if m.Data != nil && len(m.Data.Value) > 0 {
+			if !json.Valid(m.Data.Value) {
+				return fmt.Errorf("subscription details invalid json")
+			}
+			meta = json.RawMessage(m.Data.Value)
+		}
+
+		id := MustNewCartId().String()
+		g.SubscriptionDetails[id] = &SubscriptionDetails{
+			Id:           id,
+			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 not found")
+	}
+	if m.OfferingCode != "" {
+		existing.OfferingCode = m.OfferingCode
+	}
+	if m.SigningType != "" {
+		existing.SigningType = m.SigningType
+	}
+	if m.Data != nil {
+		// Only validate & assign if there is content; empty -> leave as-is.
+		if len(m.Data.Value) > 0 {
+			if !json.Valid(m.Data.Value) {
+				return fmt.Errorf("subscription details invalid json")
+			}
+			existing.Meta = m.Data.Value
+		}
+	}
+	return nil
+}
--- a/pkg/cart/price_test.go
+++ b/pkg/cart/price_test.go
@@ -0,0 +1,135 @@
+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())
+	}
+}