package mcp

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

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

// testApplier implements Applier with an in-memory map of carts, using the real
// cart mutation registry so write tools exercise the actual mutation handlers.
type testApplier struct {
	grains map[uint64]*cart.CartGrain
	reg    actor.MutationRegistry
}

func newTestApplier() *testApplier {
	reg := cart.NewCartMultationRegistry(cart.NewCartMutationContext(nil))
	return &testApplier{
		grains: make(map[uint64]*cart.CartGrain),
		reg:    reg,
	}
}

func (a *testApplier) addCart(id uint64, items int) *cart.CartGrain {
	g := cart.NewCartGrain(id, time.Now())
	g.Currency = "SEK"
	g.Language = "sv-se"
	for i := 1; i <= items; i++ {
		g.Items = append(g.Items, &cart.CartItem{
			Id:       uint32(i),
			ItemId:   uint32(1000 + i),
			Sku:      fmt.Sprintf("SKU-%03d", i),
			Quantity: uint16(i),
			Price:    *cart.NewPriceFromIncVat(int64(i*10000), 25),
			Tax:      2500,
			Meta:     &cart.ItemMeta{Name: fmt.Sprintf("Item %d", i)},
		})
	}
	g.UpdateTotals()
	a.grains[id] = g
	return g
}

func (a *testApplier) Get(_ context.Context, id uint64) (*cart.CartGrain, error) {
	g, ok := a.grains[id]
	if !ok {
		return nil, fmt.Errorf("cart %d not found", id)
	}
	return g, nil
}

func (a *testApplier) Apply(ctx context.Context, id uint64, msgs ...proto.Message) (*actor.MutationResult[cart.CartGrain], error) {
	g, ok := a.grains[id]
	if !ok {
		return nil, fmt.Errorf("cart %d not found", id)
	}
	results, err := a.reg.Apply(ctx, g, msgs...)
	if err != nil {
		return nil, err
	}
	// Re-read state after mutations.
	state, err := g.GetCurrentState()
	if err != nil {
		return nil, err
	}
	return &actor.MutationResult[cart.CartGrain]{
		Result:    *state, //nolint:govet // test helper snapshot, same pattern as SimpleGrainPool
		Mutations: results,
	}, nil

}

// call issues a tools/call against the handler and returns the decoded text
// payload (the JSON the tool returned), failing on a tool/transport error.
func call(t *testing.T, h http.Handler, name string, args map[string]any) map[string]any {
	t.Helper()
	body, _ := json.Marshal(map[string]any{
		"jsonrpc": "2.0",
		"id":      1,
		"method":  "tools/call",
		"params":  map[string]any{"name": name, "arguments": args},
	})
	rec := httptest.NewRecorder()
	req := httptest.NewRequest(http.MethodPost, "/mcp", bytes.NewReader(body))
	h.ServeHTTP(rec, req)
	if rec.Code != http.StatusOK {
		t.Fatalf("%s: status %d", name, rec.Code)
	}
	var resp struct {
		Result struct {
			IsError bool `json:"isError"`
			Content []struct {
				Text string `json:"text"`
			} `json:"content"`
		} `json:"result"`
		Error *struct {
			Message string `json:"message"`
		} `json:"error"`
	}
	if err := json.Unmarshal(rec.Body.Bytes(), &resp); err != nil {
		t.Fatalf("%s: decode response: %v (%s)", name, err, rec.Body.String())
	}
	if resp.Error != nil {
		t.Fatalf("%s: rpc error: %s", name, resp.Error.Message)
	}
	if resp.Result.IsError {
		t.Fatalf("%s: tool error: %s", name, resp.Result.Content[0].Text)
	}
	var out map[string]any
	if len(resp.Result.Content) > 0 {
		_ = json.Unmarshal([]byte(resp.Result.Content[0].Text), &out)
	}
	return out
}

func TestCartMCPRoundTrip(t *testing.T) {
	a := newTestApplier()
	a.addCart(42, 3) // cart 42 with 3 items
	h := New(a).Handler()

	// get_cart
	got := call(t, h, "get_cart", map[string]any{"cartId": "g"})
	if got == nil {
		t.Fatal("get_cart returned nil")
	}
	if id, _ := got["id"].(string); id != "g" {
		t.Errorf("get_cart id = %v, want g", got["id"])
	}
	if curr, _ := got["currency"].(string); curr != "SEK" {
		t.Errorf("get_cart currency = %q, want SEK", curr)
	}

	// get_cart_items
	items := call(t, h, "get_cart_items", map[string]any{"cartId": "g"})
	if c, _ := items["count"].(float64); c != 3 {
		t.Errorf("get_cart_items count = %v, want 3", items["count"])
	}

	// get_cart_totals
	totals := call(t, h, "get_cart_totals", map[string]any{"cartId": "g"})
	if _, ok := totals["totalPrice"]; !ok {
		t.Errorf("get_cart_totals missing totalPrice: %v", totals)
	}
	if _, ok := totals["totalDiscount"]; !ok {
		t.Errorf("get_cart_totals missing totalDiscount: %v", totals)
	}

	// get_cart_vouchers (empty cart)
	vouchers := call(t, h, "get_cart_vouchers", map[string]any{"cartId": "g"})
	if c, _ := vouchers["count"].(float64); c != 0 {
		t.Errorf("get_cart_vouchers count = %v, want 0", vouchers["count"])
	}

	// update_item_quantity: change item id=1 from qty 1 to qty 5
	updated := call(t, h, "update_item_quantity", map[string]any{
		"cartId": "g", "itemId": 1, "quantity": 5,
	})
	if updated == nil {
		t.Fatal("update_item_quantity returned nil")
	}
	// Verify via get_cart_items
	items2 := call(t, h, "get_cart_items", map[string]any{"cartId": "g"})
	itemsRaw, _ := items2["items"].([]any)
	if len(itemsRaw) != 3 {
		t.Fatalf("after qty change: want 3 items, got %d", len(itemsRaw))
	}
	firstItem := itemsRaw[0].(map[string]any)
	if q, _ := firstItem["qty"].(float64); q != 5 {
		t.Errorf("item 1 qty = %v, want 5", q)
	}

	// remove_cart_item: remove item id=2
	removed := call(t, h, "remove_cart_item", map[string]any{
		"cartId": "g", "itemId": 2,
	})
	if removed == nil {
		t.Fatal("remove_cart_item returned nil")
	}
	items3 := call(t, h, "get_cart_items", map[string]any{"cartId": "g"})
	itemsRaw3, _ := items3["items"].([]any)
	if len(itemsRaw3) != 2 {
		t.Fatalf("after remove: want 2 items, got %d", len(itemsRaw3))
	}

	// apply_voucher
	withVoucher := call(t, h, "apply_voucher", map[string]any{
		"cartId": "g", "code": "SAVE10", "value": 10000,
	})
	if withVoucher == nil {
		t.Fatal("apply_voucher returned nil")
	}
	vouchers2 := call(t, h, "get_cart_vouchers", map[string]any{"cartId": "g"})
	if c, _ := vouchers2["count"].(float64); c != 1 {
		t.Errorf("after voucher apply: count = %v, want 1", vouchers2["count"])
	}

	// remove_voucher: find the voucher id
	voucherList, _ := vouchers2["vouchers"].([]any)
	if len(voucherList) > 0 {
		v := voucherList[0].(map[string]any)
		vID := v["id"].(float64)
		call(t, h, "remove_voucher", map[string]any{
			"cartId": "g", "voucherId": int(vID),
		})
		vouchers3 := call(t, h, "get_cart_vouchers", map[string]any{"cartId": "g"})
		if c, _ := vouchers3["count"].(float64); c != 0 {
			t.Errorf("after remove voucher: count = %v, want 0", vouchers3["count"])
		}
	}

	// set_cart_user
	withUser := call(t, h, "set_cart_user", map[string]any{
		"cartId": "g", "userId": "user-abc-123",
	})
	if withUser == nil {
		t.Fatal("set_cart_user returned nil")
	}

	// clear_cart
	cleared := call(t, h, "clear_cart", map[string]any{"cartId": "g"})
	if cleared == nil {
		t.Fatal("clear_cart returned nil")
	}
	items4 := call(t, h, "get_cart_items", map[string]any{"cartId": "g"})
	if c, _ := items4["count"].(float64); c != 0 {
		t.Errorf("after clear: count = %v, want 0", items4["count"])
	}
}

func TestCartMCPErrors(t *testing.T) {
	a := newTestApplier()
	a.addCart(1, 1)
	h := New(a).Handler()

	// Invalid cart id -> isError result.
	result := callWithRaw(t, h, "get_cart", map[string]any{"cartId": "!!!"})
	if !result.IsError {
		t.Fatal("expected isError for invalid cart id")
	}

	// Missing required cartId -> still hits decode (cartId absent is empty string)
	result2 := callWithRaw(t, h, "get_cart", map[string]any{})
	if !result2.IsError {
		t.Fatal("expected isError for missing cartId")
	}

	// Non-existent cart -> isError result.
	result3 := callWithRaw(t, h, "get_cart", map[string]any{"cartId": "zzzzzz"})
	if !result3.IsError {
		t.Fatal("expected isError for non-existent cart")
	}

	// Remove non-existent item -> isError
	result4 := callWithRaw(t, h, "remove_cart_item", map[string]any{
		"cartId": "1", "itemId": 999,
	})
	if !result4.IsError {
		t.Fatal("expected isError for non-existent item")
	}

	// Unknown tool -> protocol error.
	var resp struct {
		Error *struct {
			Message string `json:"message"`
		} `json:"error"`
	}
	body, _ := json.Marshal(map[string]any{
		"jsonrpc": "2.0", "id": 1, "method": "tools/call",
		"params": map[string]any{"name": "nope", "arguments": map[string]any{}},
	})
	rec := httptest.NewRecorder()
	req := httptest.NewRequest(http.MethodPost, "/mcp", bytes.NewReader(body))
	h.ServeHTTP(rec, req)
	json.Unmarshal(rec.Body.Bytes(), &resp)
	if resp.Error == nil {
		t.Fatal("expected protocol error for unknown tool")
	}
}

// callWithRaw returns the raw result (including isError) without failing.
type rawResult struct {
	IsError bool
	Content []struct {
		Text string `json:"text"`
	}
}

func callWithRaw(t *testing.T, h http.Handler, name string, args map[string]any) rawResult {
	t.Helper()
	body, _ := json.Marshal(map[string]any{
		"jsonrpc": "2.0", "id": 1, "method": "tools/call",
		"params": map[string]any{"name": name, "arguments": args},
	})
	rec := httptest.NewRecorder()
	req := httptest.NewRequest(http.MethodPost, "/mcp", bytes.NewReader(body))
	h.ServeHTTP(rec, req)
	if rec.Code != http.StatusOK {
		t.Fatalf("%s: status %d", name, rec.Code)
	}
	var resp struct {
		Result rawResult `json:"result"`
		Error  *struct{ Message string } `json:"error"`
	}
	if err := json.Unmarshal(rec.Body.Bytes(), &resp); err != nil {
		t.Fatalf("%s: decode: %v", name, err)
	}
	if resp.Error != nil {
		t.Fatalf("%s: rpc error: %s", name, resp.Error.Message)
	}
	return resp.Result
}

func TestInitializeAndToolsList(t *testing.T) {
	a := newTestApplier()
	h := New(a).Handler()

	// Initialize.
	body, _ := json.Marshal(map[string]any{
		"jsonrpc": "2.0", "id": 1, "method": "initialize",
		"params": map[string]any{"protocolVersion": "2025-06-18"},
	})
	rec := httptest.NewRecorder()
	req := httptest.NewRequest(http.MethodPost, "/mcp", bytes.NewReader(body))
	h.ServeHTTP(rec, req)
	if rec.Code != http.StatusOK {
		t.Fatalf("initialize: status %d", rec.Code)
	}
	var initResp struct {
		Result struct {
			ProtocolVersion string `json:"protocolVersion"`
			ServerInfo      struct {
				Name string `json:"name"`
			} `json:"serverInfo"`
		} `json:"result"`
	}
	json.Unmarshal(rec.Body.Bytes(), &initResp)
	if initResp.Result.ProtocolVersion != "2025-06-18" || initResp.Result.ServerInfo.Name != "cart" {
		t.Fatalf("unexpected initialize: %+v", initResp)
	}

	// tools/list.
	body2, _ := json.Marshal(map[string]any{
		"jsonrpc": "2.0", "id": 1, "method": "tools/list",
	})
	rec2 := httptest.NewRecorder()
	req2 := httptest.NewRequest(http.MethodPost, "/mcp", bytes.NewReader(body2))
	h.ServeHTTP(rec2, req2)
	var listResp struct {
		Result struct {
			Tools []struct {
				Name        string          `json:"name"`
				InputSchema json.RawMessage `json:"inputSchema"`
			} `json:"tools"`
		} `json:"result"`
	}
	json.Unmarshal(rec2.Body.Bytes(), &listResp)
	want := map[string]bool{
		"get_cart": false, "update_item_quantity": false,
		"remove_cart_item": false, "clear_cart": false,
	}
	for _, tl := range listResp.Result.Tools {
		if _, ok := want[tl.Name]; ok {
			want[tl.Name] = true
		}
		if len(tl.InputSchema) == 0 {
			t.Fatalf("tool %s has empty inputSchema", tl.Name)
		}
	}
	for name, found := range want {
		if !found {
			t.Fatalf("expected tool %q in tools/list", name)
		}
	}
}

func TestCartMCPCartIdRoundTrip(t *testing.T) {
	// Verify that we can round-trip a base62 cart id through tools.
	a := newTestApplier()
	// Use a larger cart id to test base62 encoding.
	g := cart.NewCartGrain(12345, time.Now())
	g.Currency = "EUR"
	a.grains[12345] = g
	h := New(a).Handler()

	got := call(t, h, "get_cart", map[string]any{"cartId": g.Id.String()})
	if curr, _ := got["currency"].(string); curr != "EUR" {
		t.Errorf("currency = %q, want EUR", curr)
	}
}

func TestGetCartPromotions(t *testing.T) {
	a := newTestApplier()
	g := a.addCart(99, 2)
	// Add a synthetic applied promotion.
	g.AppliedPromotions = []cart.AppliedPromotion{
		{PromotionId: "volymrabatt", Name: "Volymrabatt", Type: "tiered_discount", Discount: cart.NewPriceFromIncVat(10000, 25)},
	}
	h := New(a).Handler()

	result := call(t, h, "get_cart_promotions", map[string]any{"cartId": g.Id.String()})
	if result == nil {
		t.Fatal("get_cart_promotions returned nil")
	}
	promos, _ := result["appliedPromotions"].([]any)
	if len(promos) != 1 {
		t.Fatalf("want 1 promotion, got %d", len(promos))
	}
	p := promos[0].(map[string]any)
	if name, _ := p["name"].(string); name != "Volymrabatt" {
		t.Errorf("promotion name = %q, want Volymrabatt", name)
	}
}