import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:supabase_flutter/supabase_flutter.dart';
import 'theme/app_theme.dart';
import 'services/collection_service.dart';
import 'services/main_collection_sync.dart';
import 'screens/login_screen.dart';
import 'screens/home_shell.dart';
import 'utils/error_utils.dart';

// Re-export so other files can `import '../main.dart'` for these.
export 'package:supabase_flutter/supabase_flutter.dart'
    show AuthException, UserAttributes;

// ── Supabase credentials ──────────────────────────────────────────────
const _supabaseUrl = String.fromEnvironment(
  'SUPABASE_URL',
  defaultValue: 'https://yaopcyubateifnicpywp.supabase.co',
);
const _supabaseAnonKey = String.fromEnvironment(
  'SUPABASE_ANON_KEY',
  defaultValue: 'sb_publishable_a7czIl7-TGeBJvid9z2XZA_3ElImliL',
);
const _usePkceAuthFlow = bool.fromEnvironment(
  'SUPABASE_USE_PKCE',
  defaultValue: true,
);

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  await Supabase.initialize(
    url: _supabaseUrl,
    anonKey: _supabaseAnonKey,
    authOptions: FlutterAuthClientOptions(
      authFlowType: _usePkceAuthFlow
          ? AuthFlowType.pkce
          : AuthFlowType.implicit,
    ),
  );

  runApp(const Car64App());
}

/// Convenience accessor used throughout the app.
final supabase = Supabase.instance.client;

/// Global keys so dialogs & snackbars survive widget-tree rebuilds.
final navigatorKey = GlobalKey<NavigatorState>();
final scaffoldMessengerKey = GlobalKey<ScaffoldMessengerState>();

/// Show a snackbar safely through the global key.
void showGlobalSnackBar(String message, {bool isError = false}) {
  final messenger = scaffoldMessengerKey.currentState;
  if (messenger == null) return;

  messenger
    ..hideCurrentSnackBar()
    ..showSnackBar(
    SnackBar(
      content: Text(message),
      backgroundColor: isError ? Colors.red : null,
      behavior: SnackBarBehavior.floating,
      margin: const EdgeInsets.fromLTRB(16, 0, 16, 96),
      duration: const Duration(seconds: 3),
    ),
  );
}

void showGlobalError(
  Object error, {
  String fallback = 'Something went wrong. Please try again.',
}) {
  logError('ui', error);
  showGlobalSnackBar(
    userMessageForError(error, fallback: fallback),
    isError: true,
  );
}

/// Show a dialog safely through the global navigator key.
Future<T?> showGlobalDialog<T>({required WidgetBuilder builder}) {
  final context = navigatorKey.currentContext;
  if (context == null) {
    return Future<T?>.value(null);
  }
  return showDialog<T>(
    context: context,
    builder: builder,
  );
}

// ── Root App Widget ───────────────────────────────────────────────────
class Car64App extends StatelessWidget {
  const Car64App({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'car64',
      debugShowCheckedModeBanner: false,
      navigatorKey: navigatorKey,
      scaffoldMessengerKey: scaffoldMessengerKey,
      theme: AppTheme.light,
      darkTheme: AppTheme.dark,
      themeMode: ThemeMode.system,
      home: const AuthGate(),
    );
  }
}

// ── Auth Gate ─────────────────────────────────────────────────────────
class AuthGate extends StatefulWidget {
  const AuthGate({super.key});

  @override
  State<AuthGate> createState() => _AuthGateState();
}

class _AuthGateState extends State<AuthGate> {
  static const _activeCollectionPrefKey = 'active_collection_id';

  bool _isLoading = true;
  bool _isInPasswordRecoveryFlow = false;
  Session? _session;
  String? _lastEnsuredUserId;

  @override
  void initState() {
    super.initState();

    _session = supabase.auth.currentSession;
    _ensureDefaultCollectionIfNeeded();

    supabase.auth.onAuthStateChange.listen(
      (AuthState authState) {
        if (!mounted) return;

        final wasLoggedIn = _session != null;
        final isLoggedIn = authState.session != null;
        _session = authState.session;

        if (wasLoggedIn != isLoggedIn) {
          setState(() {});
        }

        _ensureDefaultCollectionIfNeeded();

        if (authState.event == AuthChangeEvent.passwordRecovery) {
          setState(() => _isInPasswordRecoveryFlow = true);
          _showResetPasswordDialog();
        }
      },
      onError: (error) {
        showGlobalError(
          error,
          fallback: 'Authentication error. Please sign in again.',
        );
      },
    );

    setState(() => _isLoading = false);
  }

  Future<void> _ensureDefaultCollectionIfNeeded() async {
    final userId = _session?.user.id;
    if (userId == null || userId == _lastEnsuredUserId) return;

    _lastEnsuredUserId = userId;
    try {
      final defaultCollectionId = await CollectionService.ensureDefaultCollection();
      await _ensureMainCollectionPreference(defaultCollectionId);
    } catch (e) {
      showGlobalError(
        e,
        fallback: 'Collection setup failed. Please try again.',
      );
    }
  }

  Future<void> _ensureMainCollectionPreference(String? defaultCollectionId) async {
    final userId = _session?.user.id;
    if (userId == null) return;

    final prefs = await SharedPreferences.getInstance();
    final persisted = prefs.getString(_activeCollectionPrefKey);

    Future<bool> hasMembership(String collectionId) async {
      final membership = await supabase
          .from('collection_members')
          .select('id')
          .eq('user_id', userId)
          .eq('collection_id', collectionId)
          .maybeSingle();
      return membership != null;
    }

    if (persisted != null && await hasMembership(persisted)) {
      return;
    }

    String? nextActiveId;
    if (defaultCollectionId != null && await hasMembership(defaultCollectionId)) {
      nextActiveId = defaultCollectionId;
    } else {
      final firstMembership = await supabase
          .from('collection_members')
          .select('collection_id')
          .eq('user_id', userId)
          .limit(1);
      if (firstMembership.isNotEmpty) {
        nextActiveId = firstMembership.first['collection_id'] as String;
      }
    }

    if (nextActiveId == null) {
      await prefs.remove(_activeCollectionPrefKey);
      return;
    }

    await prefs.setString(_activeCollectionPrefKey, nextActiveId);
    MainCollectionSync.notifyChanged();
  }

  Future<void> _showResetPasswordDialog() async {
    final context = navigatorKey.currentContext;
    if (context == null) {
      _isInPasswordRecoveryFlow = false;
      return;
    }

    await showDialog<void>(
      context: context,
      barrierDismissible: false,
      builder: (_) => const _ResetPasswordDialog(),
    );

    if (mounted) {
      setState(() => _isInPasswordRecoveryFlow = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    if (_isLoading) {
      return const Scaffold(
        body: Center(child: CircularProgressIndicator()),
      );
    }
    if (_isInPasswordRecoveryFlow) return const LoginScreen();
    return _session != null ? const HomeShell() : const LoginScreen();
  }
}

// ── Reset Password Dialog ─────────────────────────────────────────────
class _ResetPasswordDialog extends StatefulWidget {
  const _ResetPasswordDialog();

  @override
  State<_ResetPasswordDialog> createState() => _ResetPasswordDialogState();
}

class _ResetPasswordDialogState extends State<_ResetPasswordDialog> {
  final _passwordController = TextEditingController();
  bool _isSaving = false;

  @override
  void dispose() {
    _passwordController.dispose();
    super.dispose();
  }

  Future<void> _save() async {
    final newPassword = _passwordController.text.trim();
    if (newPassword.length < 6) {
      showGlobalSnackBar('Password must be at least 6 characters.');
      return;
    }

    setState(() => _isSaving = true);

    try {
      await supabase.auth.updateUser(
        UserAttributes(password: newPassword),
      );
      if (!mounted) return;
      Navigator.of(context).pop();
      showGlobalSnackBar('Password updated successfully!');
    } on AuthException catch (e) {
      if (!mounted) return;
      setState(() => _isSaving = false);
      showGlobalSnackBar(e.message, isError: true);
    }
  }

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: const Text('Set New Password'),
      content: TextField(
        controller: _passwordController,
        obscureText: true,
        decoration: const InputDecoration(labelText: 'New password'),
        onSubmitted: (_) => _save(),
      ),
      actions: [
        TextButton(
          onPressed: () => Navigator.of(context).pop(),
          child: const Text('Cancel'),
        ),
        ElevatedButton(
          onPressed: _isSaving ? null : _save,
          child: _isSaving
              ? const SizedBox(
                  height: 18,
                  width: 18,
                  child: CircularProgressIndicator(strokeWidth: 2),
                )
              : const Text('Save'),
        ),
      ],
    );
  }
}