package auth

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"sync/atomic"
	"testing"

	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/metadata"
	"google.golang.org/grpc/status"
)

// mockMCIAS creates a test MCIAS server that responds to /v1/token/validate.
// The handler function receives the authorization header and returns (response, statusCode).
func mockMCIAS(t *testing.T, handler func(authHeader string) (any, int)) *httptest.Server {
	t.Helper()
	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		authHeader := r.Header.Get("Authorization")
		resp, code := handler(authHeader)
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(code)
		if err := json.NewEncoder(w).Encode(resp); err != nil {
			t.Errorf("encode response: %v", err)
		}
	}))
}

func validatorFromServer(t *testing.T, server *httptest.Server) *MCIASValidator {
	t.Helper()
	v, err := NewMCIASValidator(server.URL, "")
	if err != nil {
		t.Fatalf("create validator: %v", err)
	}
	v.httpClient = server.Client()
	return v
}

// callInterceptor invokes the interceptor with the given context and validator.
func callInterceptor(ctx context.Context, validator TokenValidator) (*TokenInfo, error) {
	interceptor := AuthInterceptor(validator)
	info := &grpc.UnaryServerInfo{FullMethod: "/mcp.v1.MCPService/TestMethod"}

	var captured *TokenInfo
	handler := func(ctx context.Context, req any) (any, error) {
		captured = TokenInfoFromContext(ctx)
		return "ok", nil
	}

	_, err := interceptor(ctx, nil, info, handler)
	return captured, err
}

func TestInterceptorRejectsNoToken(t *testing.T) {
	server := mockMCIAS(t, func(authHeader string) (any, int) {
		return map[string]any{"valid": false}, http.StatusOK
	})
	defer server.Close()

	v := validatorFromServer(t, server)

	// No metadata at all.
	_, err := callInterceptor(context.Background(), v)
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if s, ok := status.FromError(err); !ok || s.Code() != codes.Unauthenticated {
		t.Fatalf("expected Unauthenticated, got %v", err)
	}

	// Metadata present but no authorization key.
	md := metadata.Pairs("other-key", "value")
	ctx := metadata.NewIncomingContext(context.Background(), md)
	_, err = callInterceptor(ctx, v)
	if err == nil {
		t.Fatal("expected error with empty auth, got nil")
	}
	if s, ok := status.FromError(err); !ok || s.Code() != codes.Unauthenticated {
		t.Fatalf("expected Unauthenticated, got %v", err)
	}
}

func TestInterceptorRejectsMalformedToken(t *testing.T) {
	server := mockMCIAS(t, func(authHeader string) (any, int) {
		return map[string]any{"valid": false}, http.StatusOK
	})
	defer server.Close()

	v := validatorFromServer(t, server)

	md := metadata.Pairs("authorization", "NotBearer xxx")
	ctx := metadata.NewIncomingContext(context.Background(), md)

	_, err := callInterceptor(ctx, v)
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if s, ok := status.FromError(err); !ok || s.Code() != codes.Unauthenticated {
		t.Fatalf("expected Unauthenticated, got %v", err)
	}
}

func TestInterceptorRejectsInvalidToken(t *testing.T) {
	server := mockMCIAS(t, func(authHeader string) (any, int) {
		return &TokenInfo{Valid: false}, http.StatusOK
	})
	defer server.Close()

	v := validatorFromServer(t, server)

	md := metadata.Pairs("authorization", "Bearer bad-token")
	ctx := metadata.NewIncomingContext(context.Background(), md)

	_, err := callInterceptor(ctx, v)
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if s, ok := status.FromError(err); !ok || s.Code() != codes.Unauthenticated {
		t.Fatalf("expected Unauthenticated, got %v", err)
	}
}

func TestInterceptorRejectsNonAdmin(t *testing.T) {
	server := mockMCIAS(t, func(authHeader string) (any, int) {
		return &TokenInfo{
			Valid:       true,
			Username:    "regularuser",
			Roles:       []string{"user"},
			AccountType: "human",
		}, http.StatusOK
	})
	defer server.Close()

	v := validatorFromServer(t, server)

	md := metadata.Pairs("authorization", "Bearer user-token")
	ctx := metadata.NewIncomingContext(context.Background(), md)

	_, err := callInterceptor(ctx, v)
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if s, ok := status.FromError(err); !ok || s.Code() != codes.PermissionDenied {
		t.Fatalf("expected PermissionDenied, got %v", err)
	}
}

func TestInterceptorAcceptsAdmin(t *testing.T) {
	server := mockMCIAS(t, func(authHeader string) (any, int) {
		return &TokenInfo{
			Valid:       true,
			Username:    "kyle",
			Roles:       []string{"admin", "user"},
			AccountType: "human",
		}, http.StatusOK
	})
	defer server.Close()

	v := validatorFromServer(t, server)

	md := metadata.Pairs("authorization", "Bearer admin-token")
	ctx := metadata.NewIncomingContext(context.Background(), md)

	captured, err := callInterceptor(ctx, v)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if captured == nil {
		t.Fatal("expected token info in context, got nil")
	}
	if captured.Username != "kyle" {
		t.Fatalf("username: got %q, want %q", captured.Username, "kyle")
	}
	if !captured.HasRole("admin") {
		t.Fatal("expected admin role")
	}
	if captured.AccountType != "human" {
		t.Fatalf("account_type: got %q, want %q", captured.AccountType, "human")
	}
}

func TestTokenCaching(t *testing.T) {
	var requestCount atomic.Int64

	server := mockMCIAS(t, func(authHeader string) (any, int) {
		requestCount.Add(1)
		return &TokenInfo{
			Valid:       true,
			Username:    "kyle",
			Roles:       []string{"admin"},
			AccountType: "human",
		}, http.StatusOK
	})
	defer server.Close()

	v := validatorFromServer(t, server)

	ctx := context.Background()

	// First call should hit the server.
	info1, err := v.ValidateToken(ctx, "same-token")
	if err != nil {
		t.Fatalf("first validate: %v", err)
	}
	if !info1.Valid {
		t.Fatal("expected valid token")
	}

	// Second call with the same token should be cached.
	info2, err := v.ValidateToken(ctx, "same-token")
	if err != nil {
		t.Fatalf("second validate: %v", err)
	}
	if info2.Username != info1.Username {
		t.Fatalf("cached result mismatch: got %q, want %q", info2.Username, info1.Username)
	}

	if count := requestCount.Load(); count != 1 {
		t.Fatalf("expected 1 MCIAS request, got %d", count)
	}
}

func TestTokenCacheSeparateEntries(t *testing.T) {
	var requestCount atomic.Int64

	server := mockMCIAS(t, func(authHeader string) (any, int) {
		requestCount.Add(1)
		// Return different usernames based on the token.
		token := authHeader[len("Bearer "):]
		return &TokenInfo{
			Valid:       true,
			Username:    fmt.Sprintf("user-for-%s", token),
			Roles:       []string{"admin"},
			AccountType: "human",
		}, http.StatusOK
	})
	defer server.Close()

	v := validatorFromServer(t, server)

	ctx := context.Background()

	info1, err := v.ValidateToken(ctx, "token-a")
	if err != nil {
		t.Fatalf("validate token-a: %v", err)
	}

	info2, err := v.ValidateToken(ctx, "token-b")
	if err != nil {
		t.Fatalf("validate token-b: %v", err)
	}

	if info1.Username == info2.Username {
		t.Fatalf("different tokens should have different cache entries, both got %q", info1.Username)
	}

	if count := requestCount.Load(); count != 2 {
		t.Fatalf("expected 2 MCIAS requests for different tokens, got %d", count)
	}

	// Repeat calls should be cached.
	_, err = v.ValidateToken(ctx, "token-a")
	if err != nil {
		t.Fatalf("cached validate token-a: %v", err)
	}
	_, err = v.ValidateToken(ctx, "token-b")
	if err != nil {
		t.Fatalf("cached validate token-b: %v", err)
	}

	if count := requestCount.Load(); count != 2 {
		t.Fatalf("expected still 2 MCIAS requests after cache hits, got %d", count)
	}
}

func TestLoadSaveToken(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "subdir", "token")

	token := "test-bearer-token-12345"

	if err := SaveToken(path, token); err != nil {
		t.Fatalf("save: %v", err)
	}

	// Check file permissions.
	fi, err := os.Stat(path)
	if err != nil {
		t.Fatalf("stat: %v", err)
	}
	if perm := fi.Mode().Perm(); perm != 0600 {
		t.Fatalf("permissions: got %o, want 0600", perm)
	}

	// Load and verify.
	loaded, err := LoadToken(path)
	if err != nil {
		t.Fatalf("load: %v", err)
	}
	if loaded != token {
		t.Fatalf("loaded: got %q, want %q", loaded, token)
	}
}

func TestLogin(t *testing.T) {
	expectedToken := "mcias-session-token-xyz"

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/v1/auth/login" {
			t.Errorf("unexpected path: %s", r.URL.Path)
			http.NotFound(w, r)
			return
		}
		if r.Method != http.MethodPost {
			t.Errorf("unexpected method: %s", r.Method)
			w.WriteHeader(http.StatusMethodNotAllowed)
			return
		}

		var body struct {
			Username string `json:"username"`
			Password string `json:"password"`
		}
		if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
			t.Errorf("decode request body: %v", err)
			w.WriteHeader(http.StatusBadRequest)
			return
		}

		if body.Username != "kyle" || body.Password != "secret" {
			w.WriteHeader(http.StatusUnauthorized)
			_ = json.NewEncoder(w).Encode(map[string]string{"error": "invalid credentials"})
			return
		}

		w.Header().Set("Content-Type", "application/json")
		_ = json.NewEncoder(w).Encode(map[string]string{"token": expectedToken})
	}))
	defer server.Close()

	token, err := Login(server.URL, "", "kyle", "secret")
	if err != nil {
		t.Fatalf("login: %v", err)
	}
	if token != expectedToken {
		t.Fatalf("token: got %q, want %q", token, expectedToken)
	}
}

func TestLoginBadCredentials(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusUnauthorized)
		_ = json.NewEncoder(w).Encode(map[string]string{"error": "invalid credentials"})
	}))
	defer server.Close()

	_, err := Login(server.URL, "", "kyle", "wrong")
	if err == nil {
		t.Fatal("expected error for bad credentials")
	}
}

func TestContextTokenInfo(t *testing.T) {
	info := &TokenInfo{
		Valid:       true,
		Username:    "kyle",
		Roles:       []string{"admin"},
		AccountType: "human",
	}

	ctx := ContextWithTokenInfo(context.Background(), info)
	got := TokenInfoFromContext(ctx)
	if got == nil {
		t.Fatal("expected token info from context, got nil")
	}
	if got.Username != "kyle" {
		t.Fatalf("username: got %q, want %q", got.Username, "kyle")
	}

	// Empty context should return nil.
	got = TokenInfoFromContext(context.Background())
	if got != nil {
		t.Fatalf("expected nil from empty context, got %+v", got)
	}
}