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

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

func newTestApplier() *testApplier {
	reg := actor.NewMutationRegistry()
	order.RegisterMutations(reg)
	return &testApplier{
		grains: make(map[uint64]*order.OrderGrain),
		reg:    reg,
	}
}

// addPlacedOrder creates a fully placed order with n line items, returning its
// base62 id string.
func (a *testApplier) addPlacedOrder(id uint64, items int) string {
	g := order.NewOrderGrain(id, time.Now())
	lines := make([]*messages.OrderLine, items)
	for i := 0; i < items; i++ {
		lines[i] = &messages.OrderLine{
			Reference: fmt.Sprintf("line-%d", i+1),
			Sku:       fmt.Sprintf("SKU-%03d", i+1),
			Name:      fmt.Sprintf("Item %d", i+1),
			Quantity:  int32(i + 1),
			UnitPrice: int64((i + 1) * 10000),
			TaxRate:   2500,
		}
	}
	// Place the order through the real handler.
	po := &messages.PlaceOrder{
		OrderReference: "ord-" + order.OrderId(id).String(),
		CartId:         "cart-abc",
		Currency:       "SEK",
		Locale:         "sv-se",
		Country:        "se",
		CustomerEmail:  "test@example.com",
		TotalAmount:    60000,
		TotalTax:       12000,
		PlacedAtMs:     time.Now().UnixMilli(),
		Lines:          lines,
	}
	results, err := a.reg.Apply(context.Background(), g, po)
	if err != nil || len(results) == 0 || results[0].Error != nil {
		panic(fmt.Sprintf("place order: %v %v", err, results))
	}
	a.grains[id] = g
	return order.OrderId(id).String()
}

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

func (a *testApplier) Apply(ctx context.Context, id uint64, msgs ...proto.Message) (*actor.MutationResult[order.OrderGrain], error) {
	g, ok := a.grains[id]
	if !ok {
		return nil, fmt.Errorf("order %d not found", id)
	}
	results, err := a.reg.Apply(ctx, g, msgs...)
	if err != nil {
		return nil, err
	}
	state, err := g.GetCurrentState()
	if err != nil {
		return nil, err
	}
	return &actor.MutationResult[order.OrderGrain]{
		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
}

// 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 != "orders" {
		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_order": false, "get_order_status": false,
		"cancel_order": false, "complete_order": false,
		"create_fulfillment": false, "request_return": false,
		"issue_refund": 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 TestGetOrder(t *testing.T) {
	a := newTestApplier()
	oid := a.addPlacedOrder(42, 2)
	h := New(a).Handler()

	got := call(t, h, "get_order", map[string]any{"orderId": oid})
	if got == nil {
		t.Fatal("get_order returned nil")
	}
	if ref, _ := got["orderReference"].(string); ref != "ord-"+oid {
		t.Errorf("orderReference = %q, want ord-%s", ref, oid)
	}
	if curr, _ := got["currency"].(string); curr != "SEK" {
		t.Errorf("currency = %q, want SEK", curr)
	}
	if email, _ := got["customerEmail"].(string); email != "test@example.com" {
		t.Errorf("customerEmail = %q, want test@example.com", email)
	}
}

func TestGetOrderStatus(t *testing.T) {
	a := newTestApplier()
	oid := a.addPlacedOrder(1, 1)
	h := New(a).Handler()

	got := call(t, h, "get_order_status", map[string]any{"orderId": oid})
	if s, _ := got["status"].(string); s != "pending" {
		t.Errorf("status = %q, want pending", s)
	}
	transitions, _ := got["nextTransitions"].([]any)
	if len(transitions) == 0 {
		t.Fatal("expected non-empty nextTransitions")
	}
}

func TestGetOrderLines(t *testing.T) {
	a := newTestApplier()
	oid := a.addPlacedOrder(1, 3)
	h := New(a).Handler()

	got := call(t, h, "get_order_lines", map[string]any{"orderId": oid})
	if c, _ := got["count"].(float64); c != 3 {
		t.Errorf("lines count = %v, want 3", got["count"])
	}
}

func TestGetOrderPayments(t *testing.T) {
	a := newTestApplier()
	oid := a.addPlacedOrder(1, 1)
	// Simulate an authorized + captured payment.
	g, _ := a.Get(context.Background(), 1)
	g.Status = order.StatusAuthorized
	g.Payments = append(g.Payments, &order.Payment{
		Provider:   "mock",
		Authorized: 60000,
		AuthRef:    "auth-123",
	})
	h := New(a).Handler()

	got := call(t, h, "get_order_payments", map[string]any{"orderId": oid})
	if got == nil {
		t.Fatal("get_order_payments returned nil")
	}
	payments, _ := got["payments"].([]any)
	if len(payments) != 1 {
		t.Fatalf("want 1 payment, got %d", len(payments))
	}
	p := payments[0].(map[string]any)
	if prov, _ := p["provider"].(string); prov != "mock" {
		t.Errorf("payment provider = %q, want mock", prov)
	}
}

func TestCancelOrder(t *testing.T) {
	a := newTestApplier()
	oid := a.addPlacedOrder(1, 1)
	h := New(a).Handler()

	// Cancel pending order.
	got := call(t, h, "cancel_order", map[string]any{"orderId": oid, "reason": "test cancellation"})
	if got == nil {
		t.Fatal("cancel_order returned nil")
	}
	// Verify via get_order.
	after := call(t, h, "get_order", map[string]any{"orderId": oid})
	if s, _ := after["status"].(string); s != "cancelled" {
		t.Errorf("after cancel: status = %q, want cancelled", s)
	}
}

func TestCreateFulfillment(t *testing.T) {
	a := newTestApplier()
	oid := a.addPlacedOrder(1, 1)
	// Advance to captured state.
	h := New(a).Handler()
	g, _ := a.Get(context.Background(), 1)
	g.Status = order.StatusCaptured
	g.CapturedAmount = 60000

	// Fulfill the only line.
	got := call(t, h, "create_fulfillment", map[string]any{
		"orderId":        oid,
		"carrier":        "PostNord",
		"trackingNumber": "TN123456",
		"lines": []any{
			map[string]any{"reference": "line-1", "quantity": 1},
		},
	})
	if got == nil {
		t.Fatal("create_fulfillment returned nil")
	}
	after := call(t, h, "get_order", map[string]any{"orderId": oid})
	if s, _ := after["status"].(string); s != "fulfilled" {
		t.Errorf("after fulfill: status = %q, want fulfilled", s)
	}
}

func TestCompleteOrder(t *testing.T) {
	a := newTestApplier()
	oid := a.addPlacedOrder(1, 1)
	// Advance to fulfilled state.
	g, _ := a.Get(context.Background(), 1)
	g.Status = order.StatusFulfilled
	h := New(a).Handler()

	got := call(t, h, "complete_order", map[string]any{"orderId": oid})
	if got == nil {
		t.Fatal("complete_order returned nil")
	}
	after := call(t, h, "get_order", map[string]any{"orderId": oid})
	if s, _ := after["status"].(string); s != "completed" {
		t.Errorf("after complete: status = %q, want completed", s)
	}
}

func TestRequestReturn(t *testing.T) {
	a := newTestApplier()
	oid := a.addPlacedOrder(1, 2)
	// Advance to fulfilled state.
	g, _ := a.Get(context.Background(), 1)
	g.Status = order.StatusFulfilled
	h := New(a).Handler()

	got := call(t, h, "request_return", map[string]any{
		"orderId": oid,
		"reason":  "defective item",
		"lines": []any{
			map[string]any{"reference": "line-1", "quantity": 1},
		},
	})
	if got == nil {
		t.Fatal("request_return returned nil")
	}
	after := call(t, h, "get_order", map[string]any{"orderId": oid})
	returns, _ := after["returns"].([]any)
	if len(returns) != 1 {
		t.Errorf("after return: want 1 return, got %d", len(returns))
	}
}

func TestIssueRefund(t *testing.T) {
	a := newTestApplier()
	oid := a.addPlacedOrder(1, 1)
	// Advance to captured state.
	g, _ := a.Get(context.Background(), 1)
	g.Status = order.StatusCaptured
	g.CapturedAmount = 60000
	h := New(a).Handler()

	got := call(t, h, "issue_refund", map[string]any{"orderId": oid, "amount": 30000})
	if got == nil {
		t.Fatal("issue_refund returned nil")
	}
	after := call(t, h, "get_order", map[string]any{"orderId": oid})
	if r, _ := after["refundedAmount"].(float64); r != 30000 {
		t.Errorf("refundedAmount = %v, want 30000", r)
	}
}

func TestOrderMCPErrors(t *testing.T) {
	a := newTestApplier()
	oid := a.addPlacedOrder(1, 1)
	h := New(a).Handler()

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

	// Non-existent order -> isError.
	result2 := callWithRaw(t, h, "get_order", map[string]any{"orderId": "zzzzzz"})
	if !result2.IsError {
		t.Fatal("expected isError for non-existent order")
	}

	// Cancel wrong state (already cancelled) -> isError.
	call(t, h, "cancel_order", map[string]any{"orderId": oid, "reason": "cancel"})
	result3 := callWithRaw(t, h, "cancel_order", map[string]any{"orderId": oid, "reason": "double cancel"})
	if !result3.IsError {
		t.Fatal("expected isError for cancelling already-cancelled order")
	}

	// Unknown tool -> protocol error.
	var resp struct {
		Error *struct{ Message string } `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")
	}
}