package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"strconv"
	"sync"
	"time"

	"git.k6n.net/mats/go-cart-actor/pkg/actor"
	"git.k6n.net/mats/go-cart-actor/pkg/cart"
	messages "git.k6n.net/mats/go-cart-actor/proto/cart"

	"git.k6n.net/mats/go-cart-actor/pkg/voucher"
	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
	"google.golang.org/protobuf/proto"
	"google.golang.org/protobuf/types/known/anypb"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/metric"
	"go.opentelemetry.io/otel/trace"
)

// Pool metrics (cart_grain_spawned_total, cart_grain_lookups_total,
// cart_mutations_total, cart_remote_negotiation_total,
// cart_connected_remotes, …) are bumped centrally by SimpleGrainPool
// — see pkg/actor/simple_grain_pool.go. The cart Metrics is
// registered once in cmd/cart/main.go and shared with DiskStorage
// via SetMetrics, so the per-handler counters this file used to
// maintain are no longer needed.

type PoolServer struct {
	actor.GrainPool[cart.CartGrain]
	pod_name string
	// idx is the bus-fed catalog projection cache, consulted at HTTP-fetch
	// sites (AddSkuToCartHandler, buildItemGroups) to overlay authoritative
	// price / tax_class / display fields onto AddItem before mutation. nil is
	// tolerated so handlers still serve if the bus consumer is unavailable
	// (orphan / quarantine / CI), with a plain cache-miss fall-through.
	idx *catalogProjectionCache
}

func NewPoolServer(pool actor.GrainPool[cart.CartGrain], pod_name string, idx *catalogProjectionCache) *PoolServer {
	srv := &PoolServer{
		GrainPool: pool,
		pod_name:  pod_name,
		idx:       idx,
	}

	return srv
}

func (s *PoolServer) ApplyLocal(ctx context.Context, id cart.CartId, mutation ...proto.Message) (*actor.MutationResult[cart.CartGrain], error) {
	return s.Apply(ctx, uint64(id), mutation...)
}

func (s *PoolServer) GetCartHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
	grain, err := s.Get(r.Context(), uint64(id))
	if err != nil {
		return err
	}

	return s.WriteResult(w, grain)
}

func (s *PoolServer) AddSkuToCartHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
	sku := r.PathValue("sku")
	country := getCountryFromHost(r.Host)
	if s.idx == nil {
		log.Printf("No index present")
	}
	if s.idx != nil && s.idx.IsDeleted(sku) {
		// Bus-deleted SKU — skip the HTTP fetch and reject the add. Mirrors the
		// product-fetcher's "product service returned %d for sku %s" shape so
		// upstream code that pattern-matches that string still works, AND we
		// publish StatusNotFound so the HTTP response carries the right code
		// (the handler's error-return path otherwise renders as 500). http.Error
		// is the idiomatic stdlib call here — it does the encoding-safe text body
		// (no fmt.Sprintf/JSON-string-escaping fragility).
		http.Error(w, fmt.Sprintf("product service returned %d for sku %s (bus-deleted)", 404, sku), http.StatusNotFound)
		return nil
	}

	// Cache-only fast path: AddSkuToCartHandler is a SINGLE top-level add
	// (qty=1, no children). When the projection carries full authoritative
	// fields, we skip PRODUCT_BASE_URL entirely and build the AddItem
	// directly from the cache. This eliminates one HTTP round-trip per
	// add-to-cart under steady-state bus-fed conditions.
	var msg *messages.AddItem
	if s.idx != nil {
		if p, ok := s.idx.Get(sku); ok && HasRequiredFields(p) {
			msg = BuildAddItemFromCache(sku, 1, country, nil, p)
		}
	}
	if msg == nil {
		if s.idx == nil {
			log.Printf("No item found in index %s", sku)
		}
		var err error
		msg, err = GetItemAddMessage(r.Context(), sku, 1, country, nil)
		if err != nil {
			return err
		}
		if s.idx != nil {
			if p, ok := s.idx.Get(sku); ok {
				ApplyProjectionOverlay(msg, p)
			}
		}
	}

	data, err := s.ApplyLocal(r.Context(), 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 cart.CartId) error {

	itemIdString := r.PathValue("itemId")
	itemId, err := strconv.ParseInt(itemIdString, 10, 64)
	if err != nil {
		return err
	}
	data, err := s.ApplyLocal(r.Context(), id, &messages.RemoveItem{Id: uint32(itemId)})
	if err != nil {
		return err
	}
	return s.WriteResult(w, data)
}

func (s *PoolServer) QuantityChangeHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
	changeQuantity := messages.ChangeQuantity{}
	err := json.NewDecoder(r.Body).Decode(&changeQuantity)
	if err != nil {
		return err
	}
	reply, err := s.ApplyLocal(r.Context(), id, &changeQuantity)
	if err != nil {
		return err
	}
	return s.WriteResult(w, reply)
}

type Item struct {
	Sku      string  `json:"sku"`
	Quantity int     `json:"quantity"`
	StoreId  *string `json:"storeId,omitempty"`
	// Children are sub-articles (accessories, services, insurance, ...) priced
	// relative to this item. They are added as separate cart lines whose
	// ParentId points to this item's line-item id.
	Children []Item `json:"children,omitempty"`
	// CustomFields are optional user-supplied input fields for this line.
	CustomFields map[string]string `json:"customFields,omitempty"`
}

type SetCartItems struct {
	Country string `json:"country"`
	Items   []Item `json:"items"`
}

// itemGroup is a top-level item together with its child sub-articles. The child
// AddItem messages are built with their price already derived from the parent
// product; their ParentId is filled in after the parent line is applied.
type itemGroup struct {
	parent   *messages.AddItem
	children []*messages.AddItem
}

// buildItemGroups fetches every product and builds the AddItem messages. Groups
// are built concurrently; within a group the parent is fetched first so it can
// drive child pricing, then children are fetched concurrently. Input order is
// preserved. Items that fail to fetch are skipped (logged), matching the prior
// best-effort behavior.
//
// idx is the bus-fed projection cache; when non-nil, every AddItem built here
// has its cache-covered fields (price/tax_class/display/inventory_tracked/
// drop_ship) overlaid onto the HTTP-fetched answer. Cache-hit calls naturally
// become authoritative for what the projection carries; HTTP stays for
// dimensions (parent width/height for child pricing), seller/orgPrice and the
// dynamic ExtraJson product data. Skipped cleanly when idx is nil.
//
// Cache-only fast path: a parent with NO children AND a cache hit that
// satisfies HasRequiredFields skips PRODUCT_BASE_URL entirely — BuildAddItem-
// FromCache constructs the line directly from the Projection. This eliminates
// the per-add HTTP round-trip under steady-state bus-fed conditions for the
// common top-level add case. The HTTP path continues to handle:
//   - cache miss (cold-grace; a SKU not yet bus-fed)
//   - HasRequiredFields==false (partial bus delivery, e.g. TaxClass missing
//     because the producer didn't classify)
//   - parents WITH children (configurator behavior preservation — child
//     price = child per-m² rate × parent area, and parent area comes from
//     HTTP-fetched width/height that the Projection doesn't carry yet; a
//     future schema extension can unblock a child cache-only path).
func buildItemGroups(ctx context.Context, items []Item, country string, idx *catalogProjectionCache) []itemGroup {
	groups := make([]itemGroup, len(items))
	wg := sync.WaitGroup{}
	for i, itm := range items {
		wg.Go(func() {
			if idx != nil && idx.IsDeleted(itm.Sku) {
				log.Printf("error adding item %s: bus-deleted (skipping)", itm.Sku)
				return
			}

			// Cache-only fast path: see package doc above for the eligibility
			// contract.
			var parentMsg *messages.AddItem
			var parentProduct *ProductItem
			if len(itm.Children) == 0 && idx != nil {
				if p, ok := idx.Get(itm.Sku); ok && HasRequiredFields(p) {
					parentMsg = BuildAddItemFromCache(itm.Sku, itm.Quantity, country, itm.StoreId, p)
				}
			}
			if parentMsg == nil {
				var err error
				parentMsg, parentProduct, err = BuildItemMessage(ctx, itm.Sku, itm.Quantity, country, itm.StoreId, nil)
				if err != nil {
					log.Printf("error adding item %s: %v", itm.Sku, err)
					return
				}
				if idx != nil {
					if p, ok := idx.Get(itm.Sku); ok {
						ApplyProjectionOverlay(parentMsg, p)
					}
				}
			}
			parentMsg.CustomFields = itm.CustomFields
			groups[i].parent = parentMsg

			if len(itm.Children) == 0 {
				return
			}
			children := make([]*messages.AddItem, len(itm.Children))
			cwg := sync.WaitGroup{}
			for j, child := range itm.Children {
				cwg.Go(func() {
					if idx != nil && idx.IsDeleted(child.Sku) {
						log.Printf("error adding child %s of %s: bus-deleted (skipping)", child.Sku, itm.Sku)
						return
					}
					childMsg, _, err := BuildItemMessage(ctx, child.Sku, child.Quantity, country, child.StoreId, parentProduct)
					if err != nil {
						log.Printf("error adding child %s of %s: %v", child.Sku, itm.Sku, err)
						return
					}
					if idx != nil {
						if p, ok := idx.Get(child.Sku); ok {
							ApplyProjectionOverlay(childMsg, p)
						}
					}
					childMsg.CustomFields = child.CustomFields
					children[j] = childMsg
				})
			}
			cwg.Wait()
			for _, c := range children {
				if c != nil {
					groups[i].children = append(groups[i].children, c)
				}
			}
		})
	}
	wg.Wait()
	return groups
}

// applyItemGroups applies each group in dependency order: the parent first, then
// its children with ParentId set to the parent's resolved line-item id. Returns
// the last mutation result for rendering.
func (s *PoolServer) applyItemGroups(ctx context.Context, id cart.CartId, groups []itemGroup) (*actor.MutationResult[cart.CartGrain], error) {
	var last *actor.MutationResult[cart.CartGrain]
	for _, g := range groups {
		if g.parent == nil {
			continue
		}
		res, err := s.ApplyLocal(ctx, id, g.parent)
		if err != nil {
			return nil, err
		}
		last = res

		if len(g.children) == 0 {
			continue
		}
		parentLineId, ok := parentLineId(&res.Result, g.parent)
		if !ok {
			log.Printf("could not resolve parent line for item %d (sku %s); skipping %d children",
				g.parent.ItemId, g.parent.Sku, len(g.children))
			continue
		}
		childMsgs := make([]proto.Message, len(g.children))
		for i, c := range g.children {
			c.ParentId = &parentLineId
			childMsgs[i] = c
		}
		res, err = s.ApplyLocal(ctx, id, childMsgs...)
		if err != nil {
			return nil, err
		}
		last = res
	}
	return last, nil
}

// parentLineId finds the line-item id of the just-applied parent: the resident
// item with the parent's catalog ItemId, matching store, and no parent of its
// own. AddItem merges by sku+store, so at most one such line exists.
func parentLineId(grain *cart.CartGrain, parent *messages.AddItem) (uint32, bool) {
	for _, it := range grain.Items {
		if it == nil || it.ParentId != nil {
			continue
		}
		if it.ItemId != parent.ItemId {
			continue
		}
		sameStore := (it.StoreId == nil && parent.StoreId == nil) ||
			(it.StoreId != nil && parent.StoreId != nil && *it.StoreId == *parent.StoreId)
		if sameStore {
			return it.Id, true
		}
	}
	return 0, false
}

func (s *PoolServer) SetCartItemsHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
	setCartItems := SetCartItems{}
	err := json.NewDecoder(r.Body).Decode(&setCartItems)
	if err != nil {
		return err
	}

	if _, err := s.ApplyLocal(r.Context(), id, &messages.ClearCartRequest{}); err != nil {
		return err
	}
	groups := buildItemGroups(r.Context(), setCartItems.Items, setCartItems.Country, s.idx)
	reply, err := s.applyItemGroups(r.Context(), id, groups)
	if err != nil {
		return err
	}
	if reply == nil {
		// Cart was cleared but nothing added; return current (empty) state.
		grain, err := s.Get(r.Context(), uint64(id))
		if err != nil {
			return err
		}
		return s.WriteResult(w, grain)
	}
	return s.WriteResult(w, reply)
}

func (s *PoolServer) AddMultipleItemHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
	setCartItems := SetCartItems{}
	err := json.NewDecoder(r.Body).Decode(&setCartItems)
	if err != nil {
		return err
	}

	groups := buildItemGroups(r.Context(), setCartItems.Items, setCartItems.Country, s.idx)
	reply, err := s.applyItemGroups(r.Context(), id, groups)
	if err != nil {
		return err
	}
	if reply == nil {
		grain, err := s.Get(r.Context(), uint64(id))
		if err != nil {
			return err
		}
		return s.WriteResult(w, grain)
	}
	return s.WriteResult(w, reply)
}

type AddRequest struct {
	Sku      string  `json:"sku"`
	Quantity int32   `json:"quantity"`
	Country  string  `json:"country"`
	StoreId  *string `json:"storeId"`
	// Children are sub-articles priced relative to this item (see Item.Children).
	Children []Item `json:"children,omitempty"`
	// CustomFields are optional user-supplied input fields for this line.
	CustomFields map[string]string `json:"customFields,omitempty"`
}

func (s *PoolServer) AddSkuRequestHandler(w http.ResponseWriter, r *http.Request, id cart.CartId) error {
	addRequest := AddRequest{Quantity: 1}
	err := json.NewDecoder(r.Body).Decode(&addRequest)
	if err != nil {
		return err
	}

	item := Item{
		Sku:          addRequest.Sku,
		Quantity:     int(addRequest.Quantity),
		StoreId:      addRequest.StoreId,
		Children:     addRequest.Children,
		CustomFields: addRequest.CustomFields,
	}
	groups := buildItemGroups(r.Context(), []Item{item}, addRequest.Country, s.idx)
	reply, err := s.applyItemGroups(r.Context(), id, groups)
	if err != nil {
		return err
	}
	if reply == nil {
		grain, err := s.Get(r.Context(), uint64(id))
		if err != nil {
			return err
		}
		return s.WriteResult(w, grain)
	}
	return s.WriteResult(w, reply)
}

// func (s *PoolServer) HandleConfirmation(w http.ResponseWriter, r *http.Request, id CartId) error {
// 	orderId := r.PathValue("orderId")
// 	if orderId == "" {
// 		return fmt.Errorf("orderId is empty")
// 	}
// 	order, err := KlarnaInstance.GetOrder(orderId)

// 	if err != nil {
// 		return err
// 	}

// 	w.Header().Set("Content-Type", "application/json")
// 	w.Header().Set("X-Pod-Name", s.pod_name)
// 	w.Header().Set("Cache-Control", "no-cache")
// 	w.Header().Set("Access-Control-Allow-Origin", "*")
// 	w.WriteHeader(http.StatusOK)
// 	return json.NewEncoder(w).Encode(order)
// }

// func (s *PoolServer) HandleCheckout(w http.ResponseWriter, r *http.Request, id CartId) error {
// 	klarnaOrder, err := s.CreateOrUpdateCheckout(r.Host, id)
// 	if err != nil {
// 		return err
// 	}

// 	s.ApplyCheckoutStarted(klarnaOrder, id)

// 	w.Header().Set("Content-Type", "application/json")
// 	return json.NewEncoder(w).Encode(klarnaOrder)
// }
//

// Removed leftover legacy block after CookieCartIdHandler (obsolete code referencing cid/legacy)

func (s *PoolServer) RemoveCartCookie(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
	// Clear cart cookie (breaking change: do not issue a new legacy id here)
	http.SetCookie(w, &http.Cookie{
		Name:     "cartid",
		Value:    "",
		Path:     "/",
		Secure:   r.TLS != nil,
		HttpOnly: true,
		Expires:  time.Unix(0, 0),
		SameSite: http.SameSiteLaxMode,
	})
	w.WriteHeader(http.StatusOK)
	return nil
}

func (s *PoolServer) ProxyHandler(fn func(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error) func(cartId cart.CartId, w http.ResponseWriter, r *http.Request) error {
	return func(cartId cart.CartId, w http.ResponseWriter, r *http.Request) error {
		if ownerHost, ok := s.OwnerHost(uint64(cartId)); ok {
			ctx, span := tracer.Start(r.Context(), "proxy")
			defer span.End()
			span.SetAttributes(attribute.String("cartid", cartId.String()))
			hostAttr := attribute.String("other host", ownerHost.Name())
			span.SetAttributes(hostAttr)
			proxyCalls.Add(ctx, 1, metric.WithAttributes(hostAttr))
				handled, err := ownerHost.Proxy(uint64(cartId), w, r, nil)

			if err == nil && handled {
				return nil
			}
		}
		_, span := tracer.Start(r.Context(), "own")
		span.SetAttributes(attribute.String("cartid", cartId.String()))
		defer span.End()
		return fn(w, r, cartId)

	}
}

var (
	tracer     = otel.Tracer(name)
	meter      = otel.Meter(name)
	proxyCalls metric.Int64Counter
)

func init() {
	var err error
	proxyCalls, err = meter.Int64Counter("proxy.calls",
		metric.WithDescription("Number of proxy calls"),
		metric.WithUnit("{calls}"))
	if err != nil {
		panic(err)
	}

}

type AddVoucherRequest struct {
	VoucherCode string `json:"code"`
}

func (s *PoolServer) AddVoucherHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
	data := &AddVoucherRequest{}
	json.NewDecoder(r.Body).Decode(data)
	v := voucher.Service{}
	msg, err := v.GetVoucher(data.VoucherCode)
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte(err.Error()))
		return err
	}
	reply, err := s.ApplyLocal(r.Context(), cartId, msg)
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte(err.Error()))
		return err
	}
	s.WriteResult(w, reply)
	return nil
}

type SubscriptionDetailsRequest struct {
	Id           *string         `json:"id,omitempty"`
	OfferingCode string          `json:"offeringCode,omitempty"`
	SigningType  string          `json:"signingType,omitempty"`
	Data         json.RawMessage `json:"data,omitempty"`
}

func (sd *SubscriptionDetailsRequest) ToMessage() *messages.UpsertSubscriptionDetails {
	return &messages.UpsertSubscriptionDetails{
		Id:           sd.Id,
		OfferingCode: sd.OfferingCode,
		SigningType:  sd.SigningType,
		Data:         &anypb.Any{Value: sd.Data},
	}
}

func (s *PoolServer) SubscriptionDetailsHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
	data := &SubscriptionDetailsRequest{}
	err := json.NewDecoder(r.Body).Decode(data)
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte(err.Error()))
		return err
	}
	reply, err := s.ApplyLocal(r.Context(), cartId, data.ToMessage())
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte(err.Error()))
		return err
	}
	s.WriteResult(w, reply)
	return nil
}

func (s *PoolServer) RemoveVoucherHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {

	idStr := r.PathValue("voucherId")
	id, err := strconv.ParseInt(idStr, 10, 64)
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte(err.Error()))
		return err
	}
	reply, err := s.ApplyLocal(r.Context(), cartId, &messages.RemoveVoucher{Id: uint32(id)})
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte(err.Error()))
		return err
	}
	s.WriteResult(w, reply)
	return nil
}

// SetRecoveryContactRequest is the wire shape clients send to
// PUT /cart/recovery-contact. It mirrors proto SetRecoveryContact with
// JSON-friendly types; sending an empty JSON object clears all contact info.
type SetRecoveryContactRequest struct {
	Email      string           `json:"email,omitempty"`
	PushTokens []cart.PushToken `json:"pushTokens,omitempty"`
}

// toMessage builds the proto message from the JSON request body.
func (s *SetRecoveryContactRequest) toMessage() *messages.SetRecoveryContact {
	out := &messages.SetRecoveryContact{Email: s.Email}
	if len(s.PushTokens) > 0 {
		out.PushTokens = make([]*messages.PushToken, 0, len(s.PushTokens))
		for _, t := range s.PushTokens {
			out.PushTokens = append(out.PushTokens, &messages.PushToken{
				Platform: t.Platform,
				Token:    t.Token,
			})
		}
	}
	return out
}

func (s *PoolServer) SetRecoveryContactHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
	if r.Method != http.MethodPut {
		w.WriteHeader(http.StatusMethodNotAllowed)
		return nil
	}
	req := SetRecoveryContactRequest{}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(err.Error()))
		return err
	}
	reply, err := s.ApplyLocal(r.Context(), cartId, req.toMessage())
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte(err.Error()))
		return err
	}
	return s.WriteResult(w, reply)
}

func (s *PoolServer) SetUserIdHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
	setUserId := messages.SetUserId{}
	err := json.NewDecoder(r.Body).Decode(&setUserId)
	if err != nil {
		return err
	}
	reply, err := s.ApplyLocal(r.Context(), cartId, &setUserId)
	if err != nil {
		return err
	}
	return s.WriteResult(w, reply)
}

func (s *PoolServer) LineItemMarkingHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
	itemIdStr := r.PathValue("itemId")
	itemId, err := strconv.ParseInt(itemIdStr, 10, 64)
	if err != nil {
		return err
	}
	lineItemMarking := messages.LineItemMarking{Id: uint32(itemId)}
	err = json.NewDecoder(r.Body).Decode(&lineItemMarking)
	if err != nil {
		return err
	}
	reply, err := s.ApplyLocal(r.Context(), cartId, &lineItemMarking)
	if err != nil {
		return err
	}
	return s.WriteResult(w, reply)
}

func (s *PoolServer) RemoveLineItemMarkingHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
	itemIdStr := r.PathValue("itemId")
	itemId, err := strconv.ParseInt(itemIdStr, 10, 64)
	if err != nil {
		return err
	}
	removeLineItemMarking := messages.RemoveLineItemMarking{Id: uint32(itemId)}
	reply, err := s.ApplyLocal(r.Context(), cartId, &removeLineItemMarking)
	if err != nil {
		return err
	}
	return s.WriteResult(w, reply)
}

type SetCustomFieldsRequest struct {
	CustomFields map[string]string `json:"customFields"`
}

func (s *PoolServer) SetCustomFieldsHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
	itemId, err := strconv.ParseInt(r.PathValue("itemId"), 10, 64)
	if err != nil {
		return err
	}
	req := SetCustomFieldsRequest{}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		return err
	}
	reply, err := s.ApplyLocal(r.Context(), cartId, &messages.SetLineItemCustomFields{
		Id:           uint32(itemId),
		CustomFields: req.CustomFields,
	})
	if err != nil {
		return err
	}
	return s.WriteResult(w, reply)
}

func (s *PoolServer) InternalApplyMutationHandler(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error {
	if r.Method != http.MethodPost {
		w.WriteHeader(http.StatusMethodNotAllowed)
		return nil
	}
	data, err := io.ReadAll(r.Body)
	if err != nil {
		return err
	}
	mutation := &messages.Mutation{}
	err = proto.Unmarshal(data, mutation)
	if err != nil {
		return err
	}
	reply, err := s.ApplyLocal(r.Context(), cartId, mutation)
	if err != nil {
		return err
	}
	return s.WriteResult(w, reply)
}

func (s *PoolServer) GetAnywhere(ctx context.Context, cartId cart.CartId) (*cart.CartGrain, error) {
	id := uint64(cartId)
	if host, isOnOtherHost := s.OwnerHost(id); isOnOtherHost {
		return host.Get(ctx, id)
	}
	return s.Get(ctx, id)
}

func (s *PoolServer) ApplyAnywhere(ctx context.Context, cartId cart.CartId, msgs ...proto.Message) error {
	id := uint64(cartId)
	if host, isOnOtherHost := s.OwnerHost(id); isOnOtherHost {
		_, err := host.Apply(ctx, id, msgs...)
		return err
	}
	_, err := s.Apply(ctx, id, msgs...)
	return err
}

func (s *PoolServer) Serve(mux *http.ServeMux) {

	// mux.HandleFunc("OPTIONS /cart", func(w http.ResponseWriter, r *http.Request) {
	// 	w.Header().Set("Access-Control-Allow-Origin", "*")
	// 	w.Header().Set("Access-Control-Allow-Methods", "GET, PUT, POST, DELETE")
	// 	w.Header().Set("Access-Control-Allow-Headers", "Content-Type")
	// 	w.WriteHeader(http.StatusOK)
	// })

	handleFunc := func(pattern string, handlerFunc func(http.ResponseWriter, *http.Request)) {
		attr := attribute.String("http.route", pattern)
		mux.HandleFunc(pattern, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			span := trace.SpanFromContext(r.Context())
			span.SetName(pattern)
			span.SetAttributes(attr)

			labeler, _ := otelhttp.LabelerFromContext(r.Context())
			labeler.Add(attr)

			handlerFunc(w, r)
		}))
	}

	handleFunc("GET /cart", CookieCartIdHandler(s.ProxyHandler(s.GetCartHandler)))
	handleFunc("GET /cart/add/{sku}", CookieCartIdHandler(s.ProxyHandler(s.AddSkuToCartHandler)))
	handleFunc("POST /cart/add", CookieCartIdHandler(s.ProxyHandler(s.AddMultipleItemHandler)))
	handleFunc("POST /cart", CookieCartIdHandler(s.ProxyHandler(s.AddSkuRequestHandler)))
	handleFunc("POST /cart/set", CookieCartIdHandler(s.ProxyHandler(s.SetCartItemsHandler)))
	handleFunc("DELETE /cart/{itemId}", CookieCartIdHandler(s.ProxyHandler(s.DeleteItemHandler)))
	handleFunc("PUT /cart", CookieCartIdHandler(s.ProxyHandler(s.QuantityChangeHandler)))
	handleFunc("DELETE /cart", CookieCartIdHandler(s.ProxyHandler(s.RemoveCartCookie)))
	handleFunc("PUT /cart/voucher", CookieCartIdHandler(s.ProxyHandler(s.AddVoucherHandler)))
	handleFunc("PUT /cart/subscription-details", CookieCartIdHandler(s.ProxyHandler(s.SubscriptionDetailsHandler)))
	handleFunc("DELETE /cart/voucher/{voucherId}", CookieCartIdHandler(s.ProxyHandler(s.RemoveVoucherHandler)))
	handleFunc("PUT /cart/user", CookieCartIdHandler(s.ProxyHandler(s.SetUserIdHandler)))
	// PUT only — SetRecoveryContact is PUT/replace semantics. We deliberately
	// do NOT allow POST here to avoid conflicts with any future POST→create
	// semantics on /cart paths.
	handleFunc("PUT /cart/recovery-contact", CookieCartIdHandler(s.ProxyHandler(s.SetRecoveryContactHandler)))

	handleFunc("PUT /cart/item/{itemId}/marking", CookieCartIdHandler(s.ProxyHandler(s.LineItemMarkingHandler)))
	handleFunc("DELETE /cart/item/{itemId}/marking", CookieCartIdHandler(s.ProxyHandler(s.RemoveLineItemMarkingHandler)))
	handleFunc("PUT /cart/item/{itemId}/custom-fields", CookieCartIdHandler(s.ProxyHandler(s.SetCustomFieldsHandler)))

	//mux.HandleFunc("GET /cart/checkout", CookieCartIdHandler(s.ProxyHandler(s.HandleCheckout)))
	//mux.HandleFunc("GET /cart/confirmation/{orderId}", CookieCartIdHandler(s.ProxyHandler(s.HandleConfirmation)))

	handleFunc("GET /cart/byid/{id}", CartIdHandler(s.ProxyHandler(s.GetCartHandler)))

	handleFunc("POST /cart/byid/{id}", CartIdHandler(s.ProxyHandler(s.AddSkuRequestHandler)))
	handleFunc("DELETE /cart/byid/{id}/{itemId}", CartIdHandler(s.ProxyHandler(s.DeleteItemHandler)))
	handleFunc("PUT /cart/byid/{id}", CartIdHandler(s.ProxyHandler(s.QuantityChangeHandler)))
	handleFunc("PUT /cart/byid/{id}/voucher", CookieCartIdHandler(s.ProxyHandler(s.AddVoucherHandler)))
	handleFunc("DELETE /cart/byid/{id}/voucher/{voucherId}", CookieCartIdHandler(s.ProxyHandler(s.RemoveVoucherHandler)))
	handleFunc("PUT /cart/byid/{id}/user", CartIdHandler(s.ProxyHandler(s.SetUserIdHandler)))
	handleFunc("PUT /cart/byid/{id}/recovery-contact", CartIdHandler(s.ProxyHandler(s.SetRecoveryContactHandler)))
	handleFunc("PUT /cart/byid/{id}/item/{itemId}/marking", CartIdHandler(s.ProxyHandler(s.LineItemMarkingHandler)))
	handleFunc("DELETE /cart/byid/{id}/item/{itemId}/marking", CartIdHandler(s.ProxyHandler(s.RemoveLineItemMarkingHandler)))
	handleFunc("PUT /cart/byid/{id}/item/{itemId}/custom-fields", CartIdHandler(s.ProxyHandler(s.SetCustomFieldsHandler)))
}