Complete refactor to new grpc control plane and only http proxy for carts (#4)

Co-authored-by: matst80 <mats.tornberg@gmail.com>
Reviewed-on: https://git.tornberg.me/mats/go-cart-actor/pulls/4
Co-authored-by: Mats Törnberg <mats@tornberg.me>
Co-committed-by: Mats Törnberg <mats@tornberg.me>

cmd/backoffice/main.go

@@ -0,0 +1,5 @@
+package main
+
+func main() {
+	// Your code here
+}

cmd/cart/amqp-order-handler.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	amqp "github.com/rabbitmq/amqp091-go"
+)
+
+type AmqpOrderHandler struct {
+	Url        string
+	Connection *amqp.Connection
+	Channel    *amqp.Channel
+}
+
+func (h *AmqpOrderHandler) Connect() error {
+	conn, err := amqp.Dial(h.Url)
+	if err != nil {
+		return fmt.Errorf("failed to connect to RabbitMQ: %w", err)
+	}
+	h.Connection = conn
+
+	ch, err := conn.Channel()
+	if err != nil {
+		return fmt.Errorf("failed to open a channel: %w", err)
+	}
+	h.Channel = ch
+
+	return nil
+}
+
+func (h *AmqpOrderHandler) Close() error {
+	if h.Channel != nil {
+		h.Channel.Close()
+	}
+	if h.Connection != nil {
+		return h.Connection.Close()
+	}
+	return nil
+}
+
+func (h *AmqpOrderHandler) OrderCompleted(body []byte) error {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	err := h.Channel.PublishWithContext(ctx,
+		"orders", // exchange
+		"new",    // routing key
+		false,    // mandatory
+		false,    // immediate
+		amqp.Publishing{
+			ContentType: "application/json",
+			Body:        body,
+		})
+	if err != nil {
+		return fmt.Errorf("failed to publish a message: %w", err)
+	}
+
+	return nil
+}

cmd/cart/cart-grain.go

@@ -0,0 +1,268 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"slices"
+	"sync"
+	"time"
+
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+	"git.tornberg.me/go-cart-actor/pkg/voucher"
+)
+
+// 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"`
+	SellerId   string  `json:"sellerId,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"`
+	OrgPrice    *Price      `json:"orgPrice,omitempty"`
+	Stock       StockStatus `json:"stock"`
+	Quantity    int         `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"`
+}
+
+type CartDelivery struct {
+	Id          uint32                `json:"id"`
+	Provider    string                `json:"provider"`
+	Price       Price                 `json:"price"`
+	Items       []uint32              `json:"items"`
+	PickupPoint *messages.PickupPoint `json:"pickupPoint,omitempty"`
+}
+
+type CartNotification struct {
+	LinkedId int    `json:"id"`
+	Provider string `json:"provider"`
+	Title    string `json:"title"`
+	Content  string `json:"content"`
+}
+
+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"`
+}
+
+type Voucher struct {
+	Code  string                  `json:"code"`
+	Rules []*messages.VoucherRule `json:"rules"`
+	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 _, rule := range v.Rules {
+		expr := rule.GetCondition()
+		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 (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 getInt(data float64, ok bool) (int, error) {
+	if !ok {
+		return 0, fmt.Errorf("invalid type")
+	}
+	return int(data), nil
+}
+
+// func (c *CartGrain) AddItem(sku string, qty int, country string, storeId *string) (*CartGrain, error) {
+// 	cartItem, err := getItemData(sku, qty, country)
+// 	if err != nil {
+// 		return nil, err
+// 	}
+// 	cartItem.StoreId = storeId
+// 	return c.Apply(cartItem, false)
+// }
+
+func (c *CartGrain) GetState() ([]byte, error) {
+	return json.Marshal(c)
+}
+
+func (c *CartGrain) ItemsWithDelivery() []uint32 {
+	ret := make([]uint32, 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() []uint32 {
+	ret := make([]uint32, 0, len(c.Items))
+	hasDelivery := c.ItemsWithDelivery()
+	for _, item := range c.Items {
+		found := slices.Contains(hasDelivery, item.Id)
+
+		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 (c *CartGrain) Apply(content proto.Message, isReplay bool) (*CartGrain, error) {
+
+// 	updated, err := ApplyRegistered(c, content)
+// 	if err != nil {
+// 		if err == ErrMutationNotRegistered {
+// 			return nil, fmt.Errorf("unsupported mutation type %T (not registered)", content)
+// 		}
+// 		return nil, err
+// 	}
+
+// 	// Sliding TTL: update lastChange only for non-replay successful mutations.
+// 	if updated != nil && !isReplay {
+// 		c.lastChange = time.Now()
+// 		c.lastAccess = time.Now()
+// 		go AppendCartEvent(c.Id, content)
+// 	}
+
+// 	return updated, nil
+// }
+
+func (c *CartGrain) UpdateTotals() {
+	c.TotalPrice = NewPrice()
+	c.TotalDiscount = NewPrice()
+
+	for _, item := range c.Items {
+		rowTotal := MultiplyPrice(item.Price, int64(item.Quantity))
+
+		item.TotalPrice = *rowTotal
+
+		c.TotalPrice.Add(*rowTotal)
+
+		if item.OrgPrice != nil {
+			diff := NewPrice()
+			diff.Add(*item.OrgPrice)
+			diff.Subtract(item.Price)
+			if diff.IncVat > 0 {
+				c.TotalDiscount.Add(*diff)
+			}
+		}
+
+	}
+	for _, delivery := range c.Deliveries {
+		c.TotalPrice.Add(delivery.Price)
+	}
+	for _, voucher := range c.Vouchers {
+		if _, ok := voucher.AppliesTo(c); ok {
+			value := NewPriceFromIncVat(voucher.Value, 25)
+
+			c.TotalDiscount.Add(*value)
+			c.TotalPrice.Subtract(*value)
+		}
+	}
+}

cmd/cart/cart_grain_totals_test.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"testing"
+)
+
+// helper to create a cart grain with items and deliveries
+func newTestCart() *CartGrain {
+	return &CartGrain{Items: []*CartItem{}, Deliveries: []*CartDelivery{}, Vouchers: []*Voucher{}, Notifications: []CartNotification{}}
+}
+
+func TestCartGrainUpdateTotalsBasic(t *testing.T) {
+	c := newTestCart()
+	// Item1 price 1250 (ex 1000 vat 250) org price higher -> discount 200 per unit
+	item1Price := Price{IncVat: 1250, VatRates: map[float32]int64{25: 250}}
+	item1Org := &Price{IncVat: 1500, VatRates: map[float32]int64{25: 300}}
+	item2Price := Price{IncVat: 2000, VatRates: map[float32]int64{25: 400}}
+	c.Items = []*CartItem{
+		{Id: 1, Price: item1Price, OrgPrice: item1Org, Quantity: 2},
+		{Id: 2, Price: item2Price, OrgPrice: &item2Price, Quantity: 1},
+	}
+	deliveryPrice := Price{IncVat: 4900, VatRates: map[float32]int64{25: 980}}
+	c.Deliveries = []*CartDelivery{{Id: 1, Price: deliveryPrice, Items: []uint32{1, 2}}}
+
+	c.UpdateTotals()
+
+	// Expected totals: sum inc vat of items * qty plus delivery
+	// item1 total inc = 1250*2 = 2500
+	// item2 total inc = 2000*1 = 2000
+	// delivery inc = 4900
+	expectedInc := int64(2500 + 2000 + 4900)
+	if c.TotalPrice.IncVat != expectedInc {
+		t.Fatalf("TotalPrice IncVat expected %d got %d", expectedInc, c.TotalPrice.IncVat)
+	}
+
+	// Discount: current implementation computes (OrgPrice - Price) ignoring quantity -> 1500-1250=250
+	if c.TotalDiscount.IncVat != 250 {
+		t.Fatalf("TotalDiscount expected 250 got %d", c.TotalDiscount.IncVat)
+	}
+}
+
+func TestCartGrainUpdateTotalsNoItems(t *testing.T) {
+	c := newTestCart()
+	c.UpdateTotals()
+	if c.TotalPrice.IncVat != 0 || c.TotalDiscount.IncVat != 0 {
+		t.Fatalf("expected zero totals got %+v", c)
+	}
+}

cmd/cart/cart_id.go

@@ -0,0 +1,159 @@
+package main
+
+import (
+	"crypto/rand"
+	"encoding/json"
+	"fmt"
+)
+
+// 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 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 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
+}

cmd/cart/cart_id_test.go

@@ -0,0 +1,185 @@
+package main
+
+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
+}

cmd/cart/checkout_builder.go

@@ -0,0 +1,119 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// 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 {
+	Terms        string
+	Checkout     string
+	Confirmation string
+	Validation   string
+	Push         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 *CartGrain, 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.Items)+len(grain.Deliveries))
+
+	// Item lines
+	for _, it := range grain.Items {
+		if it == nil {
+			continue
+		}
+		lines = append(lines, &Line{
+			Type:           "physical",
+			Reference:      it.Sku,
+			Name:           it.Meta.Name,
+			Quantity:       it.Quantity,
+			UnitPrice:      int(it.Price.IncVat),
+			TaxRate:        2500, // 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),
+		})
+	}
+
+	// Delivery lines
+	for _, d := range grain.Deliveries {
+		if d == nil || d.Price.IncVat <= 0 {
+			continue
+		}
+		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(grain.TotalPrice.IncVat),
+		OrderTaxAmount:     int(grain.TotalPrice.TotalVat()),
+		OrderLines:         lines,
+		MerchantReference1: grain.Id.String(),
+		MerchantURLS: &CheckoutMerchantURLS{
+			Terms:        meta.Terms,
+			Checkout:     meta.Checkout,
+			Confirmation: meta.Confirmation,
+			Validation:   meta.Validation,
+			Push:         meta.Push,
+		},
+	}
+
+	payload, err := json.Marshal(order)
+	if err != nil {
+		return nil, nil, fmt.Errorf("marshal checkout order: %w", err)
+	}
+
+	return payload, order, nil
+}

cmd/cart/klarna-client.go

@@ -0,0 +1,128 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+
+	"github.com/google/uuid"
+)
+
+type KlarnaClient struct {
+	Url      string
+	UserName string
+	Password string
+	client   *http.Client
+}
+
+func NewKlarnaClient(url, userName, password string) *KlarnaClient {
+	return &KlarnaClient{
+		Url:      url,
+		UserName: userName,
+		Password: password,
+		client:   &http.Client{},
+	}
+}
+
+const (
+	KlarnaPlaygroundUrl = "https://api.playground.klarna.com"
+)
+
+func (k *KlarnaClient) GetOrder(orderId string) (*CheckoutOrder, error) {
+	req, err := http.NewRequest("GET", k.Url+"/checkout/v3/orders/"+orderId, nil)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Add("Content-Type", "application/json")
+	req.SetBasicAuth(k.UserName, k.Password)
+
+	res, err := k.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	return k.getOrderResponse(res)
+}
+
+func (k *KlarnaClient) getOrderResponse(res *http.Response) (*CheckoutOrder, error) {
+	var err error
+	var klarnaOrderResponse CheckoutOrder
+	if res.StatusCode >= 200 && res.StatusCode <= 299 {
+		err = json.NewDecoder(res.Body).Decode(&klarnaOrderResponse)
+		if err != nil {
+			return nil, err
+		}
+		return &klarnaOrderResponse, nil
+	}
+	body, err := io.ReadAll(res.Body)
+	if err == nil {
+		log.Println(string(body))
+	}
+
+	return nil, fmt.Errorf("%s", res.Status)
+}
+
+func (k *KlarnaClient) CreateOrder(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
+	}
+
+	req.Header.Add("Content-Type", "application/json")
+	req.SetBasicAuth(k.UserName, k.Password)
+
+	res, err := http.DefaultClient.Do(req)
+	if nil != err {
+		return nil, err
+	}
+	defer res.Body.Close()
+	return k.getOrderResponse(res)
+}
+
+func (k *KlarnaClient) UpdateOrder(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
+	}
+
+	req.Header.Add("Content-Type", "application/json")
+	req.SetBasicAuth(k.UserName, k.Password)
+
+	res, err := http.DefaultClient.Do(req)
+	if nil != err {
+		return nil, err
+	}
+	defer res.Body.Close()
+	return k.getOrderResponse(res)
+}
+
+func (k *KlarnaClient) AbortOrder(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
+	}
+
+	req.SetBasicAuth(k.UserName, k.Password)
+
+	_, err = http.DefaultClient.Do(req)
+	return err
+}
+
+// ordermanagement/v1/orders/{order_id}/acknowledge
+func (k *KlarnaClient) AcknowledgeOrder(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
+	}
+	id := uuid.New()
+
+	req.SetBasicAuth(k.UserName, k.Password)
+	req.Header.Add("Klarna-Idempotency-Key", id.String())
+
+	_, err = http.DefaultClient.Do(req)
+	return err
+}

cmd/cart/klarna-types.go

@@ -0,0 +1,169 @@
+package main
+
+type (
+	LineType string
+
+	// CheckoutOrder type is the request structure to create a new order from the Checkout API
+	CheckoutOrder struct {
+		ID                     string                `json:"order_id,omitempty"`
+		PurchaseCountry        string                `json:"purchase_country"`
+		PurchaseCurrency       string                `json:"purchase_currency"`
+		Locale                 string                `json:"locale"`
+		Status                 string                `json:"status,omitempty"`
+		BillingAddress         *Address              `json:"billing_address,omitempty"`
+		ShippingAddress        *Address              `json:"shipping_address,omitempty"`
+		OrderAmount            int                   `json:"order_amount"`
+		OrderTaxAmount         int                   `json:"order_tax_amount"`
+		OrderLines             []*Line               `json:"order_lines"`
+		Customer               *CheckoutCustomer     `json:"customer,omitempty"`
+		MerchantURLS           *CheckoutMerchantURLS `json:"merchant_urls"`
+		HTMLSnippet            string                `json:"html_snippet,omitempty"`
+		MerchantReference1     string                `json:"merchant_reference1,omitempty"`
+		MerchantReference2     string                `json:"merchant_reference2,omitempty"`
+		StartedAt              string                `json:"started_at,omitempty"`
+		CompletedAt            string                `json:"completed_at,omitempty"`
+		LastModifiedAt         string                `json:"last_modified_at,omitempty"`
+		Options                *CheckoutOptions      `json:"options,omitempty"`
+		Attachment             *Attachment           `json:"attachment,omitempty"`
+		ExternalPaymentMethods []*PaymentProvider    `json:"external_payment_methods,omitempty"`
+		ExternalCheckouts      []*PaymentProvider    `json:"external_checkouts,omitempty"`
+		ShippingCountries      []string              `json:"shipping_countries,omitempty"`
+		ShippingOptions        []*ShippingOption     `json:"shipping_options,omitempty"`
+		MerchantData           string                `json:"merchant_data,omitempty"`
+		GUI                    *GUI                  `json:"gui,omitempty"`
+		MerchantRequested      *AdditionalCheckBox   `json:"merchant_requested,omitempty"`
+		SelectedShippingOption *ShippingOption       `json:"selected_shipping_option,omitempty"`
+		ErrorCode              string                `json:"error_code,omitempty"`
+		ErrorMessages          []string              `json:"error_messages,omitempty"`
+	}
+
+	// GUI type wraps the GUI options
+	GUI struct {
+		Options []string `json:"options,omitempty"`
+	}
+
+	// ShippingOption type is part of the CheckoutOrder structure, represent the shipping options field
+	ShippingOption struct {
+		ID             string `json:"id"`
+		Name           string `json:"name"`
+		Description    string `json:"description,omitempty"`
+		Promo          string `json:"promo,omitempty"`
+		Price          int    `json:"price"`
+		TaxAmount      int    `json:"tax_amount"`
+		TaxRate        int    `json:"tax_rate"`
+		Preselected    bool   `json:"preselected,omitempty"`
+		ShippingMethod string `json:"shipping_method,omitempty"`
+	}
+
+	// PaymentProvider type is part of the CheckoutOrder structure, represent the ExternalPaymentMethods and
+	// ExternalCheckouts field
+	PaymentProvider struct {
+		Name        string   `json:"name"`
+		RedirectURL string   `json:"redirect_url"`
+		ImageURL    string   `json:"image_url,omitempty"`
+		Fee         int      `json:"fee,omitempty"`
+		Description string   `json:"description,omitempty"`
+		Countries   []string `json:"countries,omitempty"`
+	}
+
+	Attachment struct {
+		ContentType string `json:"content_type"`
+		Body        string `json:"body"`
+	}
+
+	CheckoutOptions struct {
+		AcquiringChannel               string              `json:"acquiring_channel,omitempty"`
+		AllowSeparateShippingAddress   bool                `json:"allow_separate_shipping_address,omitempty"`
+		ColorButton                    string              `json:"color_button,omitempty"`
+		ColorButtonText                string              `json:"color_button_text,omitempty"`
+		ColorCheckbox                  string              `json:"color_checkbox,omitempty"`
+		ColorCheckboxCheckmark         string              `json:"color_checkbox_checkmark,omitempty"`
+		ColorHeader                    string              `json:"color_header,omitempty"`
+		ColorLink                      string              `json:"color_link,omitempty"`
+		DateOfBirthMandatory           bool                `json:"date_of_birth_mandatory,omitempty"`
+		ShippingDetails                string              `json:"shipping_details,omitempty"`
+		TitleMandatory                 bool                `json:"title_mandatory,omitempty"`
+		AdditionalCheckbox             *AdditionalCheckBox `json:"additional_checkbox"`
+		RadiusBorder                   string              `json:"radius_border,omitempty"`
+		ShowSubtotalDetail             bool                `json:"show_subtotal_detail,omitempty"`
+		RequireValidateCallbackSuccess bool                `json:"require_validate_callback_success,omitempty"`
+		AllowGlobalBillingCountries    bool                `json:"allow_global_billing_countries,omitempty"`
+	}
+
+	AdditionalCheckBox struct {
+		Text     string `json:"text"`
+		Checked  bool   `json:"checked"`
+		Required bool   `json:"required"`
+	}
+
+	CheckoutMerchantURLS struct {
+		// URL of merchant terms and conditions. Should be different than checkout, confirmation and push URLs.
+		// (max 2000 characters)
+		Terms string `json:"terms"`
+
+		// URL of merchant checkout page. Should be different than terms, confirmation and push URLs.
+		// (max 2000 characters)
+		Checkout string `json:"checkout"`
+
+		// URL of merchant confirmation page. Should be different than checkout and confirmation URLs.
+		// (max 2000 characters)
+		Confirmation string `json:"confirmation"`
+
+		// URL that will be requested when an order is completed. Should be different than checkout and
+		// confirmation URLs. (max 2000 characters)
+		Push string `json:"push"`
+		// URL that will be requested for final merchant validation. (must be https, max 2000 characters)
+		Validation string `json:"validation,omitempty"`
+
+		// URL for shipping option update. (must be https, max 2000 characters)
+		ShippingOptionUpdate string `json:"shipping_option_update,omitempty"`
+
+		// URL for shipping, tax and purchase currency updates. Will be called on address changes.
+		// (must be https, max 2000 characters)
+		AddressUpdate string `json:"address_update,omitempty"`
+
+		// URL for notifications on pending orders. (max 2000 characters)
+		Notification string `json:"notification,omitempty"`
+
+		// URL for shipping, tax and purchase currency updates. Will be called on purchase country changes.
+		// (must be https, max 2000 characters)
+		CountryChange string `json:"country_change,omitempty"`
+	}
+
+	CheckoutCustomer struct {
+		// DateOfBirth in string representation 2006-01-02
+		DateOfBirth string `json:"date_of_birth"`
+	}
+
+	// Address type define the address object (json serializable) being used for the API to represent billing &
+	// shipping addresses
+	Address struct {
+		GivenName      string `json:"given_name,omitempty"`
+		FamilyName     string `json:"family_name,omitempty"`
+		Email          string `json:"email,omitempty"`
+		Title          string `json:"title,omitempty"`
+		StreetAddress  string `json:"street_address,omitempty"`
+		StreetAddress2 string `json:"street_address2,omitempty"`
+		PostalCode     string `json:"postal_code,omitempty"`
+		City           string `json:"city,omitempty"`
+		Region         string `json:"region,omitempty"`
+		Phone          string `json:"phone,omitempty"`
+		Country        string `json:"country,omitempty"`
+	}
+
+	Line struct {
+		Type                string `json:"type,omitempty"`
+		Reference           string `json:"reference,omitempty"`
+		Name                string `json:"name"`
+		Quantity            int    `json:"quantity"`
+		QuantityUnit        string `json:"quantity_unit,omitempty"`
+		UnitPrice           int    `json:"unit_price"`
+		TaxRate             int    `json:"tax_rate"`
+		TotalAmount         int    `json:"total_amount"`
+		TotalDiscountAmount int    `json:"total_discount_amount,omitempty"`
+		TotalTaxAmount      int    `json:"total_tax_amount"`
+		MerchantData        string `json:"merchant_data,omitempty"`
+		ProductURL          string `json:"product_url,omitempty"`
+		ImageURL            string `json:"image_url,omitempty"`
+	}
+)

cmd/cart/main.go

@@ -0,0 +1,461 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"net/http/pprof"
+	"os"
+	"os/signal"
+	"strings"
+	"syscall"
+	"time"
+
+	"git.tornberg.me/go-cart-actor/pkg/actor"
+	"git.tornberg.me/go-cart-actor/pkg/discovery"
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+	"git.tornberg.me/go-cart-actor/pkg/proxy"
+	"git.tornberg.me/go-cart-actor/pkg/voucher"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"k8s.io/apimachinery/pkg/watch"
+	"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 init() {
+	os.Mkdir("data", 0755)
+}
+
+type App struct {
+	pool *actor.SimpleGrainPool[CartGrain]
+}
+
+var podIp = os.Getenv("POD_IP")
+var name = os.Getenv("POD_NAME")
+var amqpUrl = os.Getenv("AMQP_URL")
+
+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"
+	}
+	if strings.Contains(strings.ToLower(host), "-se") {
+		return "se"
+	}
+	return ""
+}
+
+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)
+	}
+	return discovery.NewK8sDiscovery(client)
+}
+
+type MutationContext struct {
+	VoucherService voucher.Service
+}
+
+func main() {
+
+	controlPlaneConfig := actor.DefaultServerConfig()
+
+	reg := actor.NewMutationRegistry()
+	reg.RegisterMutations(
+		actor.NewMutation(AddItem, func() *messages.AddItem {
+			return &messages.AddItem{}
+		}),
+		actor.NewMutation(ChangeQuantity, func() *messages.ChangeQuantity {
+			return &messages.ChangeQuantity{}
+		}),
+		actor.NewMutation(RemoveItem, func() *messages.RemoveItem {
+			return &messages.RemoveItem{}
+		}),
+		actor.NewMutation(InitializeCheckout, func() *messages.InitializeCheckout {
+			return &messages.InitializeCheckout{}
+		}),
+		actor.NewMutation(OrderCreated, func() *messages.OrderCreated {
+			return &messages.OrderCreated{}
+		}),
+		actor.NewMutation(RemoveDelivery, func() *messages.RemoveDelivery {
+			return &messages.RemoveDelivery{}
+		}),
+		actor.NewMutation(SetDelivery, func() *messages.SetDelivery {
+			return &messages.SetDelivery{}
+		}),
+		actor.NewMutation(SetPickupPoint, func() *messages.SetPickupPoint {
+			return &messages.SetPickupPoint{}
+		}),
+		actor.NewMutation(ClearCart, func() *messages.ClearCartRequest {
+			return &messages.ClearCartRequest{}
+		}),
+		actor.NewMutation(AddVoucher, func() *messages.AddVoucher {
+			return &messages.AddVoucher{}
+		}),
+		actor.NewMutation(RemoveVoucher, func() *messages.RemoveVoucher {
+			return &messages.RemoveVoucher{}
+		}),
+	)
+	diskStorage := actor.NewDiskStorage[CartGrain]("data", reg)
+	poolConfig := actor.GrainPoolConfig[CartGrain]{
+		MutationRegistry: reg,
+		Storage:          diskStorage,
+		Spawn: func(id uint64) (actor.Grain[CartGrain], error) {
+			grainSpawns.Inc()
+			ret := &CartGrain{
+				lastItemId:     0,
+				lastDeliveryId: 0,
+				Deliveries:     []*CartDelivery{},
+				Id:             CartId(id),
+				Items:          []*CartItem{},
+				TotalPrice:     NewPrice(),
+			}
+			// Set baseline lastChange at spawn; replay may update it to last event timestamp.
+			ret.lastChange = time.Now()
+			ret.lastAccess = time.Now()
+
+			err := diskStorage.LoadEvents(id, ret)
+
+			return ret, err
+		},
+		SpawnHost: func(host string) (actor.Host, error) {
+			return proxy.NewRemoteHost(host)
+		},
+		TTL:      15 * time.Minute,
+		PoolSize: 2 * 65535,
+		Hostname: podIp,
+	}
+
+	pool, err := actor.NewSimpleGrainPool(poolConfig)
+	if err != nil {
+		log.Fatalf("Error creating cart pool: %v\n", err)
+	}
+	app := &App{
+		pool: pool,
+	}
+
+	grpcSrv, err := actor.NewControlServer[*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)
+
+	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.Type {
+			case watch.Deleted:
+				if pool.IsKnown(evt.Host) {
+					pool.RemoveHost(evt.Host)
+				}
+			default:
+				if !pool.IsKnown(evt.Host) {
+					log.Printf("Discovered host %s", evt.Host)
+					pool.AddRemote(evt.Host)
+				}
+			}
+		}
+	}(GetDiscovery())
+
+	orderHandler := &AmqpOrderHandler{
+		Url: amqpUrl,
+	}
+	klarnaClient := NewKlarnaClient(KlarnaPlaygroundUrl, os.Getenv("KLARNA_API_USERNAME"), os.Getenv("KLARNA_API_PASSWORD"))
+
+	syncedServer := NewPoolServer(pool, fmt.Sprintf("%s, %s", name, podIp), klarnaClient)
+	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) {
+		pool.AddRemote(r.PathValue("host"))
+	})
+	// mux.HandleFunc("GET /save", app.HandleSave)
+	//mux.HandleFunc("/", app.RewritePath)
+	mux.HandleFunc("/debug/pprof/", pprof.Index)
+	mux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
+	mux.HandleFunc("/debug/pprof/profile", pprof.Profile)
+	mux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
+	mux.HandleFunc("/debug/pprof/trace", pprof.Trace)
+	mux.Handle("/metrics", promhttp.Handler())
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		// Grain pool health: simple capacity check (mirrors previous GrainHandler.IsHealthy)
+		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("/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
+			}
+			parsed, ok := ParseCartId(cookie.Value)
+			if !ok {
+				w.WriteHeader(http.StatusBadRequest)
+				w.Write([]byte("invalid cart id format"))
+				return
+			}
+			cartId := parsed
+			syncedServer.ProxyHandler(func(w http.ResponseWriter, r *http.Request, cartId CartId) error {
+				order, err = syncedServer.CreateOrUpdateCheckout(r.Host, cartId)
+				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)
+				fmt.Fprintf(w, tpl, order.HTMLSnippet)
+				return nil
+			})(cartId, w, r)
+
+			if err != nil {
+				w.WriteHeader(http.StatusInternalServerError)
+				w.Write([]byte(err.Error()))
+			}
+
+			// v2: Apply now returns *CartGrain; order creation handled inside grain (no payload to unmarshal)
+		} else {
+			order, err = klarnaClient.GetOrder(orderId)
+			if err != nil {
+				w.WriteHeader(http.StatusBadRequest)
+				w.Write([]byte(err.Error()))
+				return
+			}
+			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)
+			fmt.Fprintf(w, tpl, order.HTMLSnippet)
+		}
+
+	})
+	mux.HandleFunc("/confirmation/{order_id}", func(w http.ResponseWriter, r *http.Request) {
+
+		orderId := r.PathValue("order_id")
+		order, err := klarnaClient.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)
+		fmt.Fprintf(w, 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 := klarnaClient.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(syncedServer, order)
+		if err != nil {
+			log.Printf("Error processing cart message: %v\n", err)
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		err = klarnaClient.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"))
+	})
+
+	mux.HandleFunc("/openapi.json", ServeEmbeddedOpenAPI)
+
+	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)
+		diskStorage.Close()
+		pool.Close()
+
+		done <- true
+	}()
+
+	log.Print("Server started at port 8080")
+	go http.ListenAndServe(":8080", mux)
+	<-done
+
+}
+
+func triggerOrderCompleted(syncedServer *PoolServer, order *CheckoutOrder) error {
+	mutation := &messages.OrderCreated{
+		OrderId: order.ID,
+		Status:  order.Status,
+	}
+	cid, ok := ParseCartId(order.MerchantReference1)
+	if !ok {
+		return fmt.Errorf("invalid cart id in order reference: %s", order.MerchantReference1)
+	}
+	_, applyErr := syncedServer.Apply(uint64(cid), mutation)
+
+	return applyErr
+}
+
+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
+}

cmd/cart/mutation_add_item.go

@@ -0,0 +1,87 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+)
+
+// 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.
+
+func AddItem(g *CartGrain, m *messages.AddItem) error {
+	if m == nil {
+		return fmt.Errorf("AddItem: nil payload")
+	}
+	if m.Quantity < 1 {
+		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 {
+		existing.Quantity += int(m.Quantity)
+		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)
+
+	g.Items = append(g.Items, &CartItem{
+		Id:       g.lastItemId,
+		ItemId:   uint32(m.ItemId),
+		Quantity: int(m.Quantity),
+		Sku:      m.Sku,
+		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,
+			SellerId:   m.SellerId,
+			SellerName: m.SellerName,
+		},
+
+		Price:      *pricePerItem,
+		TotalPrice: *MultiplyPrice(*pricePerItem, int64(m.Quantity)),
+
+		Stock:      StockStatus(m.Stock),
+		Disclaimer: m.Disclaimer,
+
+		OrgPrice:    getOrgPrice(m.OrgPrice, taxRate),
+		ArticleType: m.ArticleType,
+
+		StoreId: m.StoreId,
+	})
+	g.UpdateTotals()
+	return nil
+}
+
+func getOrgPrice(orgPrice int64, taxRate float32) *Price {
+	if orgPrice <= 0 {
+		return nil
+	}
+	return NewPriceFromIncVat(orgPrice, taxRate)
+}

cmd/cart/mutation_add_voucher.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"slices"
+
+	"git.tornberg.me/go-cart-actor/pkg/actor"
+	"git.tornberg.me/go-cart-actor/pkg/messages"
+)
+
+func RemoveVoucher(g *CartGrain, m *messages.RemoveVoucher) error {
+	if m == nil {
+		return &actor.MutationError{
+			Message:    "RemoveVoucher: nil payload",
+			Code:       1003,
+			StatusCode: 400,
+		}
+	}
+
+	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,
+		Code:  m.Code,
+		Rules: m.VoucherRules,
+		Value: m.Value,
+	})
+	g.UpdateTotals()
+	return nil
+}

cmd/cart/mutation_change_quantity.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+)
+
+// 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 ChangeQuantity(g *CartGrain, m *messages.ChangeQuantity) error {
+	if m == nil {
+		return fmt.Errorf("ChangeQuantity: nil payload")
+	}
+
+	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
+		g.Items = append(g.Items[:foundIndex], g.Items[foundIndex+1:]...)
+		return nil
+	}
+
+	g.Items[foundIndex].Quantity = int(m.Quantity)
+	g.UpdateTotals()
+	return nil
+}

cmd/cart/mutation_initialize_checkout.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+)
+
+// mutation_initialize_checkout.go
+//
+// Registers the InitializeCheckout mutation.
+// This mutation is invoked AFTER an external Klarna checkout session
+// has been successfully created or updated. It persists the Klarna
+// order reference / status and marks the cart as having a payment in progress.
+//
+// Behavior:
+//   - Sets OrderReference to the Klarna order ID (overwriting if already set).
+//   - Sets PaymentStatus to the current Klarna status.
+//   - Sets / updates PaymentInProgress flag.
+//   - Does NOT alter pricing or line items (so no totals recalculation).
+//
+// Validation:
+//   - Returns an error if payload is nil.
+//   - Returns an error if orderId is empty (integrity guard).
+//
+// Concurrency:
+//   - Relies on upstream mutation serialization for a single grain. If
+//     parallel checkout attempts are possible, add higher-level guards
+//     (e.g. reject if PaymentInProgress already true unless reusing
+//     the same OrderReference).
+
+func InitializeCheckout(g *CartGrain, m *messages.InitializeCheckout) error {
+	if m == nil {
+		return fmt.Errorf("InitializeCheckout: nil payload")
+	}
+	if m.OrderId == "" {
+		return fmt.Errorf("InitializeCheckout: missing orderId")
+	}
+
+	g.OrderReference = m.OrderId
+	g.PaymentStatus = m.Status
+	g.PaymentInProgress = m.PaymentInProgress
+	return nil
+}

cmd/cart/mutation_order_created.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+)
+
+// mutation_order_created.go
+//
+// Registers the OrderCreated mutation.
+//
+// This mutation represents the completion (or state transition) of an order
+// initiated earlier via InitializeCheckout / external Klarna processing.
+// It finalizes (or updates) the cart's order metadata.
+//
+// Behavior:
+//   - Validates payload non-nil and OrderId not empty.
+//   - Sets (or overwrites) OrderReference with the provided OrderId.
+//   - Sets PaymentStatus from payload.Status.
+//   - Marks PaymentInProgress = false (checkout flow finished / acknowledged).
+//   - Does NOT adjust monetary totals (no WithTotals()).
+//
+// Notes / Future Extensions:
+//   - If multiple order completion events can arrive (e.g., retries / webhook
+//     replays), this handler is idempotent: it simply overwrites fields.
+//   - If you need to guard against conflicting order IDs, add a check:
+//     if g.OrderReference != "" && g.OrderReference != m.OrderId { ... }
+//   - Add audit logging or metrics here if required.
+//
+// Concurrency:
+//   - Relies on the higher-level guarantee that Apply() calls are serialized
+//     per grain. If out-of-order events are possible, embed versioning or
+//     timestamps in the mutation and compare before applying changes.
+
+func OrderCreated(g *CartGrain, m *messages.OrderCreated) error {
+	if m == nil {
+		return fmt.Errorf("OrderCreated: nil payload")
+	}
+	if m.OrderId == "" {
+		return fmt.Errorf("OrderCreated: missing orderId")
+	}
+
+	g.OrderReference = m.OrderId
+	g.PaymentStatus = m.Status
+	g.PaymentInProgress = false
+	return nil
+}

cmd/cart/mutation_remove_delivery.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+)
+
+// mutation_remove_delivery.go
+//
+// Registers the RemoveDelivery mutation.
+//
+// Behavior:
+//   - Removes the delivery entry whose Id == payload.Id.
+//   - If not found, returns an error.
+//   - Cart totals are recalculated (WithTotals) after removal.
+//   - Items previously associated with that delivery simply become "without delivery";
+//     subsequent delivery mutations can reassign them.
+//
+// Differences vs legacy:
+//   - Legacy logic decremented TotalPrice explicitly before recalculating.
+//     Here we rely solely on UpdateTotals() to recompute from remaining
+//     deliveries and items (simpler / single source of truth).
+//
+// Future considerations:
+//   - If delivery pricing logic changes (e.g., dynamic taxes per delivery),
+//     UpdateTotals() may need enhancement to incorporate delivery tax properly.
+
+func RemoveDelivery(g *CartGrain, m *messages.RemoveDelivery) error {
+	if m == nil {
+		return fmt.Errorf("RemoveDelivery: nil payload")
+	}
+	targetID := uint32(m.Id)
+	index := -1
+	for i, d := range g.Deliveries {
+		if d.Id == targetID {
+			index = i
+			break
+		}
+	}
+	if index == -1 {
+		return fmt.Errorf("RemoveDelivery: delivery id %d not found", m.Id)
+	}
+
+	// Remove delivery (order not preserved beyond necessity)
+	g.Deliveries = append(g.Deliveries[:index], g.Deliveries[index+1:]...)
+	g.UpdateTotals()
+	return nil
+}

cmd/cart/mutation_remove_item.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+)
+
+// 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 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)
+	}
+
+	g.Items = append(g.Items[:index], g.Items[index+1:]...)
+	g.UpdateTotals()
+	return nil
+}

cmd/cart/mutation_set_delivery.go

@@ -0,0 +1,96 @@
+package main
+
+import (
+	"fmt"
+	"slices"
+
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+)
+
+// mutation_set_delivery.go
+//
+// Registers the SetDelivery mutation.
+//
+// Semantics (mirrors legacy switch logic):
+//   - If the payload specifies an explicit list of item IDs (payload.Items):
+//   - Each referenced cart line must exist.
+//   - None of the referenced items may already belong to a delivery.
+//   - Only those items are associated with the new delivery.
+//   - If payload.Items is empty:
+//   - All items currently without any delivery are associated with the new delivery.
+//   - A new delivery line is created with:
+//   - Auto-incremented delivery ID (cart-local)
+//   - Provider from payload
+//   - Fixed price (currently hard-coded: 4900 minor units) – adjust as needed
+//   - Optional PickupPoint copied from payload
+//   - Cart totals are recalculated (WithTotals)
+//
+// Error cases:
+//   - Referenced item does not exist
+//   - Referenced item already has a delivery
+//   - No items qualify (resulting association set empty) -> returns error (prevents creating empty delivery)
+//
+// Concurrency:
+//   - Uses g.mu to protect lastDeliveryId increment and append to Deliveries slice.
+//     Item scans are read-only and performed outside the lock for simplicity;
+//     if stricter guarantees are needed, widen the lock section.
+//
+// Future extension points:
+//   - Variable delivery pricing (based on weight, distance, provider, etc.)
+//   - Validation of provider codes
+//   - Multi-currency delivery pricing
+
+func SetDelivery(g *CartGrain, m *messages.SetDelivery) error {
+	if m == nil {
+		return fmt.Errorf("SetDelivery: nil payload")
+	}
+	if m.Provider == "" {
+		return fmt.Errorf("SetDelivery: provider is empty")
+	}
+
+	withDelivery := g.ItemsWithDelivery()
+	targetItems := make([]uint32, 0)
+
+	if len(m.Items) == 0 {
+		// Use every item currently without a delivery
+		targetItems = append(targetItems, g.ItemsWithoutDelivery()...)
+	} else {
+		// Validate explicit list
+		for _, id64 := range m.Items {
+			id := uint32(id64)
+			found := false
+			for _, it := range g.Items {
+				if it.Id == id {
+					found = true
+					break
+				}
+			}
+			if !found {
+				return fmt.Errorf("SetDelivery: item id %d not found", id)
+			}
+			if slices.Contains(withDelivery, id) {
+				return fmt.Errorf("SetDelivery: item id %d already has a delivery", id)
+			}
+			targetItems = append(targetItems, id)
+		}
+	}
+
+	if len(targetItems) == 0 {
+		return fmt.Errorf("SetDelivery: no eligible items to attach")
+	}
+
+	// Append new delivery
+	g.mu.Lock()
+	g.lastDeliveryId++
+	newId := g.lastDeliveryId
+	g.Deliveries = append(g.Deliveries, &CartDelivery{
+		Id:          newId,
+		Provider:    m.Provider,
+		PickupPoint: m.PickupPoint,
+		Price:       *NewPriceFromIncVat(4900, 25.0),
+		Items:       targetItems,
+	})
+	g.mu.Unlock()
+
+	return nil
+}

cmd/cart/mutation_set_pickup_point.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+)
+
+// mutation_set_pickup_point.go
+//
+// Registers the SetPickupPoint mutation using the generic mutation registry.
+//
+// Semantics (mirrors original switch-based implementation):
+//   - Locate the delivery with Id == payload.DeliveryId
+//   - Set (or overwrite) its PickupPoint with the provided data
+//   - Does NOT alter pricing or taxes (so no totals recalculation required)
+//
+// Validation / Error Handling:
+//   - If payload is nil -> error
+//   - If DeliveryId not found -> error
+//
+// Concurrency:
+//   - Relies on the existing expectation that higher-level mutation routing
+//     serializes Apply() calls per grain; if stricter guarantees are needed,
+//     a delivery-level lock could be introduced later.
+//
+// Future Extensions:
+//   - Validate pickup point fields (country code, zip format, etc.)
+//   - Track history / audit of pickup point changes
+//   - Trigger delivery price adjustments (which would then require WithTotals()).
+
+func SetPickupPoint(g *CartGrain, m *messages.SetPickupPoint) error {
+	if m == nil {
+		return fmt.Errorf("SetPickupPoint: nil payload")
+	}
+
+	for _, d := range g.Deliveries {
+		if d.Id == uint32(m.DeliveryId) {
+			d.PickupPoint = &messages.PickupPoint{
+				Id:      m.Id,
+				Name:    m.Name,
+				Address: m.Address,
+				City:    m.City,
+				Zip:     m.Zip,
+				Country: m.Country,
+			}
+			return nil
+		}
+	}
+	return fmt.Errorf("SetPickupPoint: delivery id %d not found", m.DeliveryId)
+}
+
+func ClearCart(g *CartGrain, m *messages.ClearCartRequest) error {
+	if m == nil {
+		return fmt.Errorf("ClearCart: nil payload")
+	}
+	// maybe check if payment is done?
+	g.Deliveries = g.Deliveries[:0]
+	g.Items = g.Items[:0]
+	g.UpdateTotals()
+	return nil
+}

cmd/cart/openapi.json

@@ -0,0 +1,677 @@
+{
+  "openapi": "3.0.3",
+  "info": {
+    "title": "Cart Service API",
+    "description": "HTTP API for shopping cart operations (cookie-based or explicit id): retrieve cart, add/replace items, update quantity, manage deliveries.",
+    "version": "1.0.0"
+  },
+  "servers": [
+    {
+      "url": "https://cart.tornberg.me",
+      "description": "Production server"
+    },
+    {
+      "url": "http://localhost:8080",
+      "description": "Local development (cart API mounted under /cart)"
+    }
+  ],
+  "paths": {
+    "/cart/": {
+      "get": {
+        "summary": "Get (or create) current cart (cookie based)",
+        "description": "Returns the current cart. If no cartid cookie is present a new cart is created and Set-Cart-Id response header plus a Set-Cookie header are sent.",
+        "responses": {
+          "200": {
+            "description": "Cart retrieved",
+            "headers": {
+              "Set-Cart-Id": {
+                "description": "Returned when a new cart was created this request",
+                "schema": { "type": "string" }
+              },
+              "X-Pod-Name": {
+                "description": "Pod identifier serving the request",
+                "schema": { "type": "string" }
+              }
+            },
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "500": { "description": "Server error" }
+        }
+      },
+      "post": {
+        "summary": "Add single SKU (body)",
+        "description": "Adds (or increases quantity of) a single SKU using request body.",
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": { "$ref": "#/components/schemas/AddRequest" }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "Item added",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid request body" },
+          "500": { "description": "Server error" }
+        }
+      },
+      "put": {
+        "summary": "Change quantity of an item",
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": { "$ref": "#/components/schemas/ChangeQuantity" }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "Quantity updated",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid request body" },
+          "500": { "description": "Server error" }
+        }
+      },
+      "delete": {
+        "summary": "Clear cart cookie (logical cart reused only if referenced later)",
+        "description": "Removes the cartid cookie by expiring it. Does not mutate server-side cart state.",
+        "responses": {
+          "200": { "description": "Cookie cleared (empty body)" }
+        }
+      }
+    },
+    "/cart/add/{sku}": {
+      "get": {
+        "summary": "Add a SKU (path)",
+        "description": "Adds a single SKU with implicit quantity 1. Country inferred from Host header (-se / -no).",
+        "parameters": [{ "$ref": "#/components/parameters/SkuParam" }],
+        "responses": {
+          "200": {
+            "description": "Item added",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/add": {
+      "post": {
+        "summary": "Add multiple items (append)",
+        "description": "Adds multiple items to the cart without clearing existing contents.",
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": { "$ref": "#/components/schemas/SetCartItems" }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "Items added",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid body" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/set": {
+      "post": {
+        "summary": "Replace cart contents",
+        "description": "Clears the cart first, then adds the provided items (idempotent with respect to target set).",
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": { "$ref": "#/components/schemas/SetCartItems" }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "Cart replaced",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid body" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/{itemId}": {
+      "delete": {
+        "summary": "Remove item by line id",
+        "parameters": [
+          {
+            "name": "itemId",
+            "in": "path",
+            "required": true,
+            "schema": { "type": "integer", "format": "int64", "minimum": 0 },
+            "description": "Internal cart line item identifier (not SKU)."
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "Item removed",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Bad id" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/delivery": {
+      "post": {
+        "summary": "Set (add) delivery",
+        "description": "Adds a delivery option referencing one or more line item ids.",
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": { "$ref": "#/components/schemas/SetDeliveryRequest" }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "Delivery added/updated",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid body" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/delivery/{deliveryId}": {
+      "delete": {
+        "summary": "Remove delivery",
+        "parameters": [{ "$ref": "#/components/parameters/DeliveryIdParam" }],
+        "responses": {
+          "200": {
+            "description": "Delivery removed",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Bad id" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/delivery/{deliveryId}/pickupPoint": {
+      "put": {
+        "summary": "Set pickup point for delivery",
+        "parameters": [{ "$ref": "#/components/parameters/DeliveryIdParam" }],
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": { "$ref": "#/components/schemas/PickupPoint" }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "Pickup point set",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid body" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/byid/{id}": {
+      "get": {
+        "summary": "Get cart by explicit id",
+        "parameters": [{ "$ref": "#/components/parameters/CartIdParam" }],
+        "responses": {
+          "200": {
+            "description": "Cart retrieved",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid id" },
+          "500": { "description": "Server error" }
+        }
+      },
+      "post": {
+        "summary": "Add single SKU (body) by cart id",
+        "parameters": [{ "$ref": "#/components/parameters/CartIdParam" }],
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": { "$ref": "#/components/schemas/AddRequest" }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "Item added",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid body" },
+          "500": { "description": "Server error" }
+        }
+      },
+      "put": {
+        "summary": "Change quantity (by id variant)",
+        "parameters": [{ "$ref": "#/components/parameters/CartIdParam" }],
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": { "$ref": "#/components/schemas/ChangeQuantity" }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "Quantity updated",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid body" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/byid/{id}/add/{sku}": {
+      "get": {
+        "summary": "Add SKU (path) by explicit cart id",
+        "parameters": [
+          { "$ref": "#/components/parameters/CartIdParam" },
+          { "$ref": "#/components/parameters/SkuParam" }
+        ],
+        "responses": {
+          "200": {
+            "description": "Item added",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid id/sku" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/byid/{id}/{itemId}": {
+      "delete": {
+        "summary": "Remove item (by id variant)",
+        "parameters": [
+          { "$ref": "#/components/parameters/CartIdParam" },
+          {
+            "name": "itemId",
+            "in": "path",
+            "required": true,
+            "schema": { "type": "integer", "format": "int64", "minimum": 0 }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "Item removed",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid id" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/byid/{id}/delivery": {
+      "post": {
+        "summary": "Set delivery (by id variant)",
+        "parameters": [{ "$ref": "#/components/parameters/CartIdParam" }],
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": { "$ref": "#/components/schemas/SetDeliveryRequest" }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "Delivery added/updated",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid body" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/byid/{id}/delivery/{deliveryId}": {
+      "delete": {
+        "summary": "Remove delivery (by id variant)",
+        "parameters": [
+          { "$ref": "#/components/parameters/CartIdParam" },
+          { "$ref": "#/components/parameters/DeliveryIdParam" }
+        ],
+        "responses": {
+          "200": {
+            "description": "Delivery removed",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid ids" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/cart/byid/{id}/delivery/{deliveryId}/pickupPoint": {
+      "put": {
+        "summary": "Set pickup point (by id variant)",
+        "parameters": [
+          { "$ref": "#/components/parameters/CartIdParam" },
+          { "$ref": "#/components/parameters/DeliveryIdParam" }
+        ],
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": { "$ref": "#/components/schemas/PickupPoint" }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "Pickup point updated",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/CartGrain" }
+              }
+            }
+          },
+          "400": { "description": "Invalid body" },
+          "500": { "description": "Server error" }
+        }
+      }
+    },
+    "/healthz": {
+      "get": {
+        "summary": "Liveness & capacity probe",
+        "responses": {
+          "200": { "description": "Healthy" },
+          "500": { "description": "Unhealthy" }
+        }
+      }
+    },
+    "/readyz": {
+      "get": {
+        "summary": "Readiness probe",
+        "responses": {
+          "200": { "description": "Ready" }
+        }
+      }
+    },
+    "/livez": {
+      "get": {
+        "summary": "Liveness probe",
+        "responses": {
+          "200": { "description": "Alive" }
+        }
+      }
+    },
+    "/version": {
+      "get": {
+        "summary": "Service version",
+        "responses": {
+          "200": {
+            "description": "Version string",
+            "content": {
+              "text/plain": {
+                "schema": { "type": "string", "example": "1.0.0" }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "parameters": {
+      "SkuParam": {
+        "name": "sku",
+        "in": "path",
+        "required": true,
+        "schema": { "type": "string" }
+      },
+      "CartIdParam": {
+        "name": "id",
+        "in": "path",
+        "required": true,
+        "description": "Base62 encoded cart id",
+        "schema": {
+          "type": "string",
+          "pattern": "^[0-9A-Za-z]+$",
+          "minLength": 1
+        }
+      },
+      "DeliveryIdParam": {
+        "name": "deliveryId",
+        "in": "path",
+        "required": true,
+        "schema": { "type": "integer", "format": "int64", "minimum": 0 }
+      }
+    },
+    "schemas": {
+      "CartGrain": {
+        "type": "object",
+        "description": "Cart aggregate (actor state)",
+        "properties": {
+          "id": {
+            "type": "string",
+            "description": "Cart id (base62 encoded uint64)"
+          },
+          "items": {
+            "type": "array",
+            "items": { "$ref": "#/components/schemas/CartItem" }
+          },
+          "totalPrice": { "type": "integer", "format": "int64" },
+          "totalTax": { "type": "integer", "format": "int64" },
+          "totalDiscount": { "type": "integer", "format": "int64" },
+          "deliveries": {
+            "type": "array",
+            "items": { "$ref": "#/components/schemas/CartDelivery" }
+          },
+          "processing": { "type": "boolean" },
+          "paymentInProgress": { "type": "boolean" },
+          "orderReference": { "type": "string" },
+          "paymentStatus": { "type": "string" }
+        },
+        "required": ["id", "items", "totalPrice", "totalTax", "totalDiscount"]
+      },
+      "CartItem": {
+        "type": "object",
+        "properties": {
+          "id": { "type": "integer" },
+          "itemId": { "type": "integer" },
+          "parentId": { "type": "integer" },
+          "sku": { "type": "string" },
+          "name": { "type": "string" },
+          "price": { "type": "integer", "format": "int64" },
+          "totalPrice": { "type": "integer", "format": "int64" },
+          "totalTax": { "type": "integer", "format": "int64" },
+          "orgPrice": { "type": "integer", "format": "int64" },
+          "stock": {
+            "type": "integer",
+            "description": "0=OutOfStock,1=LowStock,2=InStock"
+          },
+          "qty": { "type": "integer" },
+          "tax": { "type": "integer" },
+          "taxRate": { "type": "integer" },
+          "brand": { "type": "string" },
+          "category": { "type": "string" },
+          "category2": { "type": "string" },
+          "category3": { "type": "string" },
+          "category4": { "type": "string" },
+          "category5": { "type": "string" },
+          "disclaimer": { "type": "string" },
+          "sellerId": { "type": "string" },
+          "sellerName": { "type": "string" },
+          "type": { "type": "string", "description": "Article type" },
+          "image": { "type": "string" },
+          "outlet": { "type": "string", "nullable": true },
+          "storeId": { "type": "string", "nullable": true }
+        },
+        "required": ["id", "sku", "name", "price", "qty", "tax"]
+      },
+      "CartDelivery": {
+        "type": "object",
+        "properties": {
+          "id": { "type": "integer" },
+          "provider": { "type": "string" },
+          "price": { "type": "integer", "format": "int64" },
+          "items": {
+            "type": "array",
+            "items": { "type": "integer" }
+          },
+          "pickupPoint": { "$ref": "#/components/schemas/PickupPoint" }
+        },
+        "required": ["id", "provider", "price", "items"]
+      },
+      "PickupPoint": {
+        "type": "object",
+        "properties": {
+          "id": { "type": "string" },
+          "name": { "type": "string", "nullable": true },
+          "address": { "type": "string", "nullable": true },
+          "city": { "type": "string", "nullable": true },
+          "zip": { "type": "string", "nullable": true },
+          "country": { "type": "string", "nullable": true }
+        },
+        "required": ["id"]
+      },
+      "AddRequest": {
+        "type": "object",
+        "properties": {
+          "quantity": {
+            "type": "integer",
+            "format": "int32",
+            "minimum": 1,
+            "default": 1
+          },
+          "sku": { "type": "string" },
+          "country": {
+            "type": "string",
+            "description": "Two-letter country code (inferred if omitted)"
+          },
+          "storeId": { "type": "string", "nullable": true }
+        },
+        "required": ["sku"]
+      },
+      "ChangeQuantity": {
+        "type": "object",
+        "properties": {
+          "id": {
+            "type": "integer",
+            "format": "int64",
+            "description": "Cart line item id"
+          },
+          "quantity": { "type": "integer", "format": "int32", "minimum": 0 }
+        },
+        "required": ["id", "quantity"]
+      },
+      "Item": {
+        "type": "object",
+        "properties": {
+          "sku": { "type": "string" },
+          "quantity": { "type": "integer", "minimum": 1 },
+          "storeId": { "type": "string", "nullable": true }
+        },
+        "required": ["sku", "quantity"]
+      },
+      "SetCartItems": {
+        "type": "object",
+        "properties": {
+          "country": { "type": "string" },
+          "items": {
+            "type": "array",
+            "items": { "$ref": "#/components/schemas/Item" },
+            "minItems": 0
+          }
+        },
+        "required": ["items"]
+      },
+      "SetDeliveryRequest": {
+        "type": "object",
+        "properties": {
+          "provider": { "type": "string" },
+          "items": {
+            "type": "array",
+            "items": { "type": "integer", "format": "int64" },
+            "description": "Line item ids served by this delivery"
+          },
+          "pickupPoint": { "$ref": "#/components/schemas/PickupPoint" }
+        },
+        "required": ["provider", "items"]
+      }
+    }
+  },
+  "tags": [{ "name": "Cart" }, { "name": "Delivery" }, { "name": "System" }]
+}

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/pool-server.go

@@ -0,0 +1,532 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"strconv"
+	"sync"
+	"time"
+
+	"git.tornberg.me/go-cart-actor/pkg/actor"
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+	"git.tornberg.me/go-cart-actor/pkg/voucher"
+	"github.com/gogo/protobuf/proto"
+)
+
+type PoolServer struct {
+	actor.GrainPool[*CartGrain]
+	pod_name     string
+	klarnaClient *KlarnaClient
+}
+
+func NewPoolServer(pool actor.GrainPool[*CartGrain], pod_name string, klarnaClient *KlarnaClient) *PoolServer {
+	return &PoolServer{
+		GrainPool:    pool,
+		pod_name:     pod_name,
+		klarnaClient: klarnaClient,
+	}
+}
+
+func (s *PoolServer) ApplyLocal(id CartId, mutation ...proto.Message) (*actor.MutationResult[*CartGrain], error) {
+	return s.Apply(uint64(id), mutation...)
+}
+
+func (s *PoolServer) GetCartHandler(w http.ResponseWriter, r *http.Request, id CartId) error {
+	grain, err := s.Get(uint64(id))
+	if err != nil {
+		return err
+	}
+
+	return s.WriteResult(w, grain)
+}
+
+func (s *PoolServer) AddSkuToCartHandler(w http.ResponseWriter, r *http.Request, id CartId) error {
+	sku := r.PathValue("sku")
+	msg, err := GetItemAddMessage(sku, 1, getCountryFromHost(r.Host), nil)
+	if err != nil {
+		return err
+	}
+	data, err := s.ApplyLocal(id, msg)
+	if err != nil {
+		return err
+	}
+	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 CartId) error {
+
+	itemIdString := r.PathValue("itemId")
+	itemId, err := strconv.ParseInt(itemIdString, 10, 64)
+	if err != nil {
+		return err
+	}
+	data, err := s.ApplyLocal(id, &messages.RemoveItem{Id: uint32(itemId)})
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, data)
+}
+
+type SetDeliveryRequest struct {
+	Provider    string                `json:"provider"`
+	Items       []uint32              `json:"items"`
+	PickupPoint *messages.PickupPoint `json:"pickupPoint,omitempty"`
+}
+
+func (s *PoolServer) SetDeliveryHandler(w http.ResponseWriter, r *http.Request, id CartId) error {
+
+	delivery := SetDeliveryRequest{}
+	err := json.NewDecoder(r.Body).Decode(&delivery)
+	if err != nil {
+		return err
+	}
+	data, err := s.ApplyLocal(id, &messages.SetDelivery{
+		Provider:    delivery.Provider,
+		Items:       delivery.Items,
+		PickupPoint: delivery.PickupPoint,
+	})
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, data)
+}
+
+func (s *PoolServer) SetPickupPointHandler(w http.ResponseWriter, r *http.Request, id CartId) error {
+
+	deliveryIdString := r.PathValue("deliveryId")
+	deliveryId, err := strconv.ParseInt(deliveryIdString, 10, 64)
+	if err != nil {
+		return err
+	}
+	pickupPoint := messages.PickupPoint{}
+	err = json.NewDecoder(r.Body).Decode(&pickupPoint)
+	if err != nil {
+		return err
+	}
+	reply, err := s.ApplyLocal(id, &messages.SetPickupPoint{
+		DeliveryId: uint32(deliveryId),
+		Id:         pickupPoint.Id,
+		Name:       pickupPoint.Name,
+		Address:    pickupPoint.Address,
+		City:       pickupPoint.City,
+		Zip:        pickupPoint.Zip,
+		Country:    pickupPoint.Country,
+	})
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, reply)
+}
+
+func (s *PoolServer) RemoveDeliveryHandler(w http.ResponseWriter, r *http.Request, id CartId) error {
+
+	deliveryIdString := r.PathValue("deliveryId")
+	deliveryId, err := strconv.Atoi(deliveryIdString)
+	if err != nil {
+		return err
+	}
+	reply, err := s.ApplyLocal(id, &messages.RemoveDelivery{Id: uint32(deliveryId)})
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, reply)
+}
+
+func (s *PoolServer) QuantityChangeHandler(w http.ResponseWriter, r *http.Request, id CartId) error {
+	changeQuantity := messages.ChangeQuantity{}
+	err := json.NewDecoder(r.Body).Decode(&changeQuantity)
+	if err != nil {
+		return err
+	}
+	reply, err := s.ApplyLocal(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(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(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 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(setCartItems.Items, setCartItems.Country)...)
+
+	reply, err := s.ApplyLocal(id, msgs...)
+	if err != nil {
+		return err
+	}
+	return s.WriteResult(w, reply)
+}
+
+func (s *PoolServer) AddMultipleItemHandler(w http.ResponseWriter, r *http.Request, id CartId) error {
+	setCartItems := SetCartItems{}
+	err := json.NewDecoder(r.Body).Decode(&setCartItems)
+	if err != nil {
+		return err
+	}
+
+	reply, err := s.ApplyLocal(id, getMultipleAddMessages(setCartItems.Items, setCartItems.Country)...)
+	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 CartId) error {
+	addRequest := AddRequest{Quantity: 1}
+	err := json.NewDecoder(r.Body).Decode(&addRequest)
+	if err != nil {
+		return err
+	}
+	msg, err := GetItemAddMessage(addRequest.Sku, int(addRequest.Quantity), addRequest.Country, addRequest.StoreId)
+	if err != nil {
+		return err
+	}
+	reply, err := s.ApplyLocal(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 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 (s *PoolServer) CreateOrUpdateCheckout(host string, id CartId) (*CheckoutOrder, error) {
+	country := getCountryFromHost(host)
+	meta := &CheckoutMeta{
+		Terms:        fmt.Sprintf("https://%s/terms", host),
+		Checkout:     fmt.Sprintf("https://%s/checkout?order_id={checkout.order.id}", host),
+		Confirmation: fmt.Sprintf("https://%s/confirmation/{checkout.order.id}", host),
+		Validation:   fmt.Sprintf("https://%s/validate", host),
+		Push:         fmt.Sprintf("https://%s/push?order_id={checkout.order.id}", host),
+		Country:      country,
+		Currency:     getCurrency(country),
+		Locale:       getLocale(country),
+	}
+
+	// Get current grain state (may be local or remote)
+	grain, err := s.Get(uint64(id))
+	if err != nil {
+		return nil, err
+	}
+
+	// Build pure checkout payload
+	payload, _, err := BuildCheckoutOrderPayload(grain, meta)
+	if err != nil {
+		return nil, err
+	}
+
+	if grain.OrderReference != "" {
+		return s.klarnaClient.UpdateOrder(grain.OrderReference, bytes.NewReader(payload))
+	} else {
+		return s.klarnaClient.CreateOrder(bytes.NewReader(payload))
+	}
+}
+
+func (s *PoolServer) ApplyCheckoutStarted(klarnaOrder *CheckoutOrder, id CartId) (*actor.MutationResult[*CartGrain], error) {
+	// Persist initialization state via mutation (best-effort)
+	return s.ApplyLocal(id, &messages.InitializeCheckout{
+		OrderId:           klarnaOrder.ID,
+		Status:            klarnaOrder.Status,
+		PaymentInProgress: true,
+	})
+}
+
+// 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)
+// }
+//
+
+func CookieCartIdHandler(fn func(cartId 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 CartId
+		cookie, err := r.Cookie("cartid")
+		if err != nil || cookie.Value == "" {
+			id = 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 := ParseCartId(cookie.Value)
+			if !ok {
+				id = 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()))
+		}
+
+	}
+}
+
+// Removed leftover legacy block after CookieCartIdHandler (obsolete code referencing cid/legacy)
+
+func (s *PoolServer) RemoveCartCookie(w http.ResponseWriter, r *http.Request, cartId 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 CartIdHandler(fn func(cartId 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 CartId
+		raw := r.PathValue("id")
+		// If no id supplied, generate a new one
+		if raw == "" {
+			id := MustNewCartId()
+			w.Header().Set("Set-Cart-Id", id.String())
+		} else {
+			// Parse base62 cart id
+			if parsedId, ok := 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()))
+		}
+	}
+}
+
+func (s *PoolServer) ProxyHandler(fn func(w http.ResponseWriter, r *http.Request, cartId CartId) error) func(cartId CartId, w http.ResponseWriter, r *http.Request) error {
+	return func(cartId CartId, w http.ResponseWriter, r *http.Request) error {
+		if ownerHost, ok := s.OwnerHost(uint64(cartId)); ok {
+			handled, err := ownerHost.Proxy(uint64(cartId), w, r)
+			if err == nil && handled {
+				return nil
+			}
+		}
+
+		return fn(w, r, cartId)
+
+	}
+}
+
+type AddVoucherRequest struct {
+	VoucherCode string `json:"code"`
+}
+
+func (s *PoolServer) AddVoucherHandler(w http.ResponseWriter, r *http.Request, cartId 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(cartId, msg)
+	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 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(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) Serve() *http.ServeMux {
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("OPTIONS /", 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)
+	})
+
+	mux.HandleFunc("GET /", CookieCartIdHandler(s.ProxyHandler(s.GetCartHandler)))
+	mux.HandleFunc("GET /add/{sku}", CookieCartIdHandler(s.ProxyHandler(s.AddSkuToCartHandler)))
+	mux.HandleFunc("POST /add", CookieCartIdHandler(s.ProxyHandler(s.AddMultipleItemHandler)))
+	mux.HandleFunc("POST /", CookieCartIdHandler(s.ProxyHandler(s.AddSkuRequestHandler)))
+	mux.HandleFunc("POST /set", CookieCartIdHandler(s.ProxyHandler(s.SetCartItemsHandler)))
+	mux.HandleFunc("DELETE /{itemId}", CookieCartIdHandler(s.ProxyHandler(s.DeleteItemHandler)))
+	mux.HandleFunc("PUT /", CookieCartIdHandler(s.ProxyHandler(s.QuantityChangeHandler)))
+	mux.HandleFunc("DELETE /", CookieCartIdHandler(s.ProxyHandler(s.RemoveCartCookie)))
+	mux.HandleFunc("POST /delivery", CookieCartIdHandler(s.ProxyHandler(s.SetDeliveryHandler)))
+	mux.HandleFunc("DELETE /delivery/{deliveryId}", CookieCartIdHandler(s.ProxyHandler(s.RemoveDeliveryHandler)))
+	mux.HandleFunc("PUT /delivery/{deliveryId}/pickupPoint", CookieCartIdHandler(s.ProxyHandler(s.SetPickupPointHandler)))
+	mux.HandleFunc("PUT /voucher", CookieCartIdHandler(s.ProxyHandler(s.AddVoucherHandler)))
+	mux.HandleFunc("DELETE /voucher/{voucherId}", CookieCartIdHandler(s.ProxyHandler(s.RemoveVoucherHandler)))
+
+	//mux.HandleFunc("GET /checkout", CookieCartIdHandler(s.ProxyHandler(s.HandleCheckout)))
+	//mux.HandleFunc("GET /confirmation/{orderId}", CookieCartIdHandler(s.ProxyHandler(s.HandleConfirmation)))
+
+	mux.HandleFunc("GET /byid/{id}", CartIdHandler(s.ProxyHandler(s.GetCartHandler)))
+	mux.HandleFunc("GET /byid/{id}/add/{sku}", CartIdHandler(s.ProxyHandler(s.AddSkuToCartHandler)))
+	mux.HandleFunc("POST /byid/{id}", CartIdHandler(s.ProxyHandler(s.AddSkuRequestHandler)))
+	mux.HandleFunc("DELETE /byid/{id}/{itemId}", CartIdHandler(s.ProxyHandler(s.DeleteItemHandler)))
+	mux.HandleFunc("PUT /byid/{id}", CartIdHandler(s.ProxyHandler(s.QuantityChangeHandler)))
+	mux.HandleFunc("POST /byid/{id}/delivery", CartIdHandler(s.ProxyHandler(s.SetDeliveryHandler)))
+	mux.HandleFunc("DELETE /byid/{id}/delivery/{deliveryId}", CartIdHandler(s.ProxyHandler(s.RemoveDeliveryHandler)))
+	mux.HandleFunc("PUT /byid/{id}/delivery/{deliveryId}/pickupPoint", CartIdHandler(s.ProxyHandler(s.SetPickupPointHandler)))
+	mux.HandleFunc("PUT /byid/{id}/voucher", CookieCartIdHandler(s.ProxyHandler(s.AddVoucherHandler)))
+	mux.HandleFunc("DELETE /byid/{id}/voucher/{voucherId}", CookieCartIdHandler(s.ProxyHandler(s.RemoveVoucherHandler)))
+	//mux.HandleFunc("GET /byid/{id}/checkout", CartIdHandler(s.ProxyHandler(s.HandleCheckout)))
+	//mux.HandleFunc("GET /byid/{id}/confirmation", CartIdHandler(s.ProxyHandler(s.HandleConfirmation)))
+
+	return mux
+}

cmd/cart/price.go

@@ -0,0 +1,131 @@
+package main
+
+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})
+}
+
+// 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
+}

cmd/cart/price_test.go

@@ -0,0 +1,135 @@
+package main
+
+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(1000, 0.25)
+	if p.IncVat != 1000 {
+		t.Fatalf("expected IncVat %d got %d", 1000, p.IncVat)
+	}
+	if p.VatRates[25] != 250 {
+		t.Fatalf("expected VAT 25 rate %d got %d", 250, p.VatRates[25])
+	}
+	if p.ValueExVat() != 750 {
+		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())
+	}
+}

cmd/cart/product-fetcher.go

@@ -0,0 +1,121 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+
+	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+	"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(sku string, country string) (*index.DataItem, error) {
+	baseUrl := getBaseUrl(country)
+	res, err := http.Get(fmt.Sprintf("%s/api/by-sku/%s", baseUrl, sku))
+	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(sku string, qty int, country string, storeId *string) (*messages.AddItem, error) {
+	item, err := FetchItem(sku, country)
+	if err != nil {
+		return nil, err
+	}
+	return ToItemAddMessage(item, storeId, qty, country), nil
+}
+
+func ToItemAddMessage(item *index.DataItem, storeId *string, qty int, country string) *messages.AddItem {
+	orgPrice, _ := getInt(item.GetNumberFieldValue(5)) // getInt(item.Fields[5])
+
+	price, err := getInt(item.GetNumberFieldValue(4)) //Fields[4]
+	if err != nil {
+		return nil
+	}
+
+	stock := StockStatus(0)
+	centralStockValue, ok := item.GetStringFieldValue(3)
+	if storeId == nil {
+		if ok {
+			pureNumber := strings.Replace(centralStockValue, "+", "", -1)
+			if centralStock, err := strconv.ParseInt(pureNumber, 10, 64); err == nil {
+				stock = StockStatus(centralStock)
+			}
+		}
+	} else {
+		storeStock, ok := item.Stock.GetStock()[*storeId]
+		if ok {
+			stock = 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)
+
+	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,
+	}
+}
+
+func getTax(articleType string) int32 {
+	switch articleType {
+	case "ZDIE":
+		return 600
+	default:
+		return 2500
+	}
+}