package ucp

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"net/http/httptest"
	"os"
	"strings"
	"testing"
	"time"

	"git.k6n.net/mats/go-cart-actor/pkg/actor"
	"git.k6n.net/mats/go-cart-actor/pkg/cart"
	"git.k6n.net/mats/go-cart-actor/pkg/checkout"
	checkoutMessages "git.k6n.net/mats/go-cart-actor/proto/checkout"
	"google.golang.org/protobuf/proto"
)

type testCheckoutApplier struct {
	grains map[uint64]*checkout.CheckoutGrain
}

func newTestCheckoutApplier() *testCheckoutApplier {
	return &testCheckoutApplier{
		grains: make(map[uint64]*checkout.CheckoutGrain),
	}
}

func (a *testCheckoutApplier) Get(_ context.Context, id uint64) (*checkout.CheckoutGrain, error) {
	g, ok := a.grains[id]
	if !ok {
		g = checkout.NewCheckoutGrain(id, 0, 0, time.UnixMilli(1000000), nil)
		a.grains[id] = g
	}
	return g, nil
}

func (a *testCheckoutApplier) Apply(ctx context.Context, id uint64, msgs ...proto.Message) (*actor.MutationResult[checkout.CheckoutGrain], error) {
	g, err := a.Get(ctx, id)
	if err != nil {
		return nil, err
	}
	for _, msg := range msgs {
		switch m := msg.(type) {
		case *checkoutMessages.InitializeCheckout:
			g.CartId = cart.CartId(m.CartId)
		}
	}
	return &actor.MutationResult[checkout.CheckoutGrain]{
		Result: *g,
	}, nil
}

func TestCheckoutHandler_CreateWithCartId(t *testing.T) {
	// Start a mock Cart server.
	mockCartServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if !strings.Contains(r.URL.Path, "/cart/byid/") {
			t.Errorf("expected path to contain /cart/byid/, got %q", r.URL.Path)
		}
		// Return dummy cart state bytes.
		w.WriteHeader(http.StatusOK)
		w.Write([]byte(`{}`))
	}))
	defer mockCartServer.Close()

	os.Setenv("CART_INTERNAL_URL", mockCartServer.URL)
	defer os.Unsetenv("CART_INTERNAL_URL")

	applier := newTestCheckoutApplier()
	handler := CheckoutHandler(applier)

	// Create a dummy cart ID.
	dummyCartId, _ := cart.NewCartId()

	reqBody := fmt.Sprintf(`{"cartId": %q}`, dummyCartId.String())
	req := httptest.NewRequest("POST", "/", strings.NewReader(reqBody))
	req.Header.Set("Content-Type", "application/json")
	rec := httptest.NewRecorder()
	handler.ServeHTTP(rec, req)

	if rec.Code != http.StatusCreated {
		t.Fatalf("expected 201 Created, got %d. Body: %s", rec.Code, rec.Body.String())
	}

	var resp CheckoutResponse
	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
		t.Fatalf("failed to decode response: %v", err)
	}
	if resp.Id == "" {
		t.Fatal("expected non-empty checkout session id")
	}
	if resp.CartId != dummyCartId.String() {
		t.Fatalf("expected cartId %q, got %q", dummyCartId.String(), resp.CartId)
	}
}

func TestCheckoutHandler_CreateWithLineItemsFallback(t *testing.T) {
	// Start a mock Cart server that supports both creating a cart and getting it.
	var createdCartId cart.CartId
	mockCartServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.Method == "POST" && strings.Contains(r.URL.Path, "/ucp/v1/carts/") {
			var err error
			createdCartId, err = cart.NewCartId()
			if err != nil {
				w.WriteHeader(http.StatusInternalServerError)
				return
			}
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusCreated)
			w.Write([]byte(fmt.Sprintf(`{"id": %q, "status": "active"}`, createdCartId.String())))
			return
		}

		if r.Method == "GET" && strings.Contains(r.URL.Path, "/cart/byid/") {
			w.WriteHeader(http.StatusOK)
			w.Write([]byte(`{}`))
			return
		}

		w.WriteHeader(http.StatusNotFound)
	}))
	defer mockCartServer.Close()

	os.Setenv("CART_INTERNAL_URL", mockCartServer.URL)
	defer os.Unsetenv("CART_INTERNAL_URL")

	applier := newTestCheckoutApplier()
	handler := CheckoutHandler(applier)

	// POST with line_items and no cartId.
	reqBody := `{"line_items": [{"sku": "SKU123", "quantity": 2}]}`
	req := httptest.NewRequest("POST", "/", strings.NewReader(reqBody))
	req.Header.Set("Content-Type", "application/json")
	rec := httptest.NewRecorder()
	handler.ServeHTTP(rec, req)

	if rec.Code != http.StatusCreated {
		t.Fatalf("expected 201 Created, got %d. Body: %s", rec.Code, rec.Body.String())
	}

	var resp CheckoutResponse
	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
		t.Fatalf("failed to decode response: %v", err)
	}
	if resp.Id == "" {
		t.Fatal("expected non-empty checkout session id")
	}
	if resp.CartId != createdCartId.String() {
		t.Fatalf("expected cartId %q to match created implicit cart %q", resp.CartId, createdCartId.String())
	}
}