import 'dart:async';
import 'dart:convert';
import 'package:dio/dio.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter_secure_storage/flutter_secure_storage.dart';
import '../../../../core/config/api_endpoints.dart';
import '../../../../core/config/app_config.dart';
import '../../../../core/errors/error_handler.dart';
import '../../../../core/telemetry/telemetry.dart';
import '../../../notifications/presentation/providers/notification_providers.dart';
import '../models/auth_response.dart';
import 'tenant_provider.dart';

const _keyAccessToken = 'access_token';
const _keyRefreshToken = 'refresh_token';

final secureStorageProvider = Provider<FlutterSecureStorage>((ref) {
  return const FlutterSecureStorage();
});

final authStateProvider =
    StateNotifierProvider<AuthNotifier, AuthState>((ref) {
  return AuthNotifier(ref);
});

final accessTokenProvider = FutureProvider<String?>((ref) async {
  final storage = ref.watch(secureStorageProvider);
  return storage.read(key: _keyAccessToken);
});

class AuthState {
  final bool isAuthenticated;
  final bool isLoading;
  final String? error;
  final AuthUser? user;

  const AuthState({
    this.isAuthenticated = false,
    this.isLoading = false,
    this.error,
    this.user,
  });

  AuthState copyWith({
    bool? isAuthenticated,
    bool? isLoading,
    String? error,
    AuthUser? user,
  }) {
    return AuthState(
      isAuthenticated: isAuthenticated ?? this.isAuthenticated,
      isLoading: isLoading ?? this.isLoading,
      error: error,
      user: user ?? this.user,
    );
  }
}

class AuthNotifier extends StateNotifier<AuthState> {
  final Ref _ref;
  StreamSubscription? _notificationSubscription;

  AuthNotifier(this._ref) : super(const AuthState());

  /// Try to restore session from stored tokens on app startup.
  /// Returns true if a valid session was restored.
  Future<bool> tryRestoreSession() async {
    final storage = _ref.read(secureStorageProvider);
    final accessToken = await storage.read(key: _keyAccessToken);
    if (accessToken == null) return false;

    // Decode JWT payload to get user info
    final user = _decodeUserFromJwt(accessToken);
    if (user == null) {
      // Token is malformed, try refresh
      return refreshToken();
    }

    // Check if token is expired
    if (_isTokenExpired(accessToken)) {
      // Try to refresh
      return refreshToken();
    }

    // Restore auth state
    state = state.copyWith(
      isAuthenticated: true,
      user: user,
    );

    // Restore tenant context
    if (user.tenantId != null) {
      _ref.read(currentTenantIdProvider.notifier).state = user.tenantId;
    }

    // Reconnect notifications
    _connectNotifications(user.tenantId);

    // Restore telemetry session
    TelemetryService().setUserId(user.id);
    TelemetryService().setAccessToken(accessToken);
    TelemetryService().resumeAfterLogin();

    return true;
  }

  /// Decode user info from JWT payload without verification.
  AuthUser? _decodeUserFromJwt(String token) {
    try {
      final parts = token.split('.');
      if (parts.length != 3) return null;
      final payload = json.decode(
        utf8.decode(base64Url.decode(base64Url.normalize(parts[1]))),
      ) as Map<String, dynamic>;
      return AuthUser(
        id: payload['sub'] as String,
        email: payload['email'] as String? ?? '',
        name: payload['name'] as String? ?? payload['email'] as String? ?? '',
        roles: (payload['roles'] as List?)?.cast<String>() ?? [],
        tenantId: payload['tenantId'] as String?,
      );
    } catch (_) {
      return null;
    }
  }

  /// Check if JWT is expired (with 60s buffer).
  bool _isTokenExpired(String token) {
    try {
      final parts = token.split('.');
      if (parts.length != 3) return true;
      final payload = json.decode(
        utf8.decode(base64Url.decode(base64Url.normalize(parts[1]))),
      ) as Map<String, dynamic>;
      final exp = payload['exp'] as int?;
      if (exp == null) return true;
      final expiry = DateTime.fromMillisecondsSinceEpoch(exp * 1000);
      return DateTime.now().isAfter(expiry.subtract(const Duration(seconds: 60)));
    } catch (_) {
      return true;
    }
  }

  /// Send SMS OTP to the given phone number.
  Future<void> sendSmsCode(String phone) async {
    final config = _ref.read(appConfigProvider);
    final dio = Dio(BaseOptions(baseUrl: config.apiBaseUrl));
    await dio.post(ApiEndpoints.smsSend, data: {'phone': phone, 'purpose': 'login'});
  }

  /// Login with phone number + OTP (passwordless).
  Future<bool> loginWithOtp(String phone, String smsCode) async {
    state = state.copyWith(isLoading: true, error: null);
    try {
      final config = _ref.read(appConfigProvider);
      final dio = Dio(BaseOptions(baseUrl: config.apiBaseUrl));
      final response = await dio.post(
        ApiEndpoints.loginOtp,
        data: {'phone': phone, 'smsCode': smsCode},
      );
      final authResponse = AuthResponse.fromJson(response.data as Map<String, dynamic>);
      final storage = _ref.read(secureStorageProvider);
      await storage.write(key: _keyAccessToken, value: authResponse.accessToken);
      await storage.write(key: _keyRefreshToken, value: authResponse.refreshToken);
      state = state.copyWith(isAuthenticated: true, isLoading: false, user: authResponse.user);
      _ref.invalidate(accessTokenProvider);
      if (authResponse.user.tenantId != null) {
        _ref.read(currentTenantIdProvider.notifier).state = authResponse.user.tenantId;
      }
      _connectNotifications(authResponse.user.tenantId);
      TelemetryService().setUserId(authResponse.user.id);
      TelemetryService().setAccessToken(authResponse.accessToken);
      TelemetryService().resumeAfterLogin();
      return true;
    } on DioException catch (e) {
      final message = (e.response?.data is Map) ? e.response?.data['message'] : null;
      state = state.copyWith(isLoading: false, error: message?.toString() ?? '验证码登录失败');
      return false;
    } catch (e) {
      state = state.copyWith(isLoading: false, error: ErrorHandler.friendlyMessage(e));
      return false;
    }
  }

  Future<bool> login(String email, String password) async {
    state = state.copyWith(isLoading: true, error: null);

    try {
      final config = _ref.read(appConfigProvider);
      final dio = Dio(BaseOptions(baseUrl: config.apiBaseUrl));

      final response = await dio.post(
        ApiEndpoints.login,
        data: {'email': email, 'password': password},
      );

      final authResponse =
          AuthResponse.fromJson(response.data as Map<String, dynamic>);

      final storage = _ref.read(secureStorageProvider);
      await storage.write(
          key: _keyAccessToken, value: authResponse.accessToken);
      await storage.write(
          key: _keyRefreshToken, value: authResponse.refreshToken);

      state = state.copyWith(
        isAuthenticated: true,
        isLoading: false,
        user: authResponse.user,
      );

      _ref.invalidate(accessTokenProvider);

      // Set tenant context for all subsequent API calls
      if (authResponse.user.tenantId != null) {
        _ref.read(currentTenantIdProvider.notifier).state =
            authResponse.user.tenantId;
      }

      // Connect notification service after login
      _connectNotifications(authResponse.user.tenantId);

      TelemetryService().setUserId(authResponse.user.id);
      TelemetryService().setAccessToken(authResponse.accessToken);
      TelemetryService().resumeAfterLogin();

      return true;
    } on DioException catch (e) {
      final message =
          (e.response?.data is Map) ? e.response?.data['message'] : null;
      state = state.copyWith(
        isLoading: false,
        error: message?.toString() ?? '登录失败',
      );
      return false;
    } catch (e) {
      state = state.copyWith(
        isLoading: false,
        error: ErrorHandler.friendlyMessage(e),
      );
      return false;
    }
  }

  Future<void> logout() async {
    // Disconnect notification service
    _notificationSubscription?.cancel();
    _notificationSubscription = null;
    _ref.read(notificationServiceProvider).disconnect();

    // Clear tenant context
    _ref.read(currentTenantIdProvider.notifier).state = null;

    // Pause telemetry before clearing tokens
    await TelemetryService().pauseForLogout();
    TelemetryService().clearUserId();
    TelemetryService().clearAccessToken();

    final storage = _ref.read(secureStorageProvider);
    await storage.delete(key: _keyAccessToken);
    await storage.delete(key: _keyRefreshToken);
    _ref.invalidate(accessTokenProvider);
    state = const AuthState();
  }

  Future<bool> refreshToken() async {
    try {
      final storage = _ref.read(secureStorageProvider);
      final storedRefreshToken = await storage.read(key: _keyRefreshToken);
      if (storedRefreshToken == null) return false;

      final config = _ref.read(appConfigProvider);
      final dio = Dio(BaseOptions(baseUrl: config.apiBaseUrl));

      final response = await dio.post(
        ApiEndpoints.refreshToken,
        data: {'refreshToken': storedRefreshToken},
      );

      final data = response.data as Map<String, dynamic>;
      final newAccessToken = data['accessToken'] as String;
      await storage.write(key: _keyAccessToken, value: newAccessToken);
      await storage.write(
          key: _keyRefreshToken, value: data['refreshToken'] as String);

      _ref.invalidate(accessTokenProvider);

      // Restore user state from new token if not already authenticated
      if (!state.isAuthenticated) {
        final user = _decodeUserFromJwt(newAccessToken);
        if (user != null) {
          state = state.copyWith(isAuthenticated: true, user: user);
          if (user.tenantId != null) {
            _ref.read(currentTenantIdProvider.notifier).state = user.tenantId;
          }
          _connectNotifications(user.tenantId);
        }
      }

      return true;
    } catch (_) {
      await logout();
      return false;
    }
  }

  void _connectNotifications(String? tenantId) {
    if (tenantId == null) return;
    try {
      final notificationService = _ref.read(notificationServiceProvider);
      final notificationList = _ref.read(notificationListProvider.notifier);

      notificationService.connect(tenantId);

      // Forward incoming notifications to the list
      _notificationSubscription =
          notificationService.notifications.listen((notification) {
        notificationList.add(notification);
      });
    } catch (_) {
      // Non-critical — app works without push notifications
    }
  }
}