import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'core/auth/auth_notifier.dart';
import 'features/auth/screens/welcome_screen.dart';
import 'features/auth/screens/display_name_screen.dart';
import 'features/auth/screens/register_screen.dart';
import 'features/auth/screens/otp_screen.dart';
import 'features/auth/screens/force_register_screen.dart';
import 'features/auth/screens/set_display_name_screen.dart';
import 'features/onboarding/onboarding_screen.dart';
import 'features/splash/splash_screen.dart';
import 'features/home/home_screen.dart';
import 'features/chat/screens/searching_screen.dart';
import 'features/chat/screens/bestie_found_screen.dart';
import 'features/chat/screens/no_bestie_screen.dart';
import 'features/chat/screens/chat_screen.dart';
import 'features/chat/screens/chat_history_screen.dart';
import 'features/chat/screens/chat_transcript_screen.dart';

class RouterNotifier extends ChangeNotifier {
  final Ref _ref;

  RouterNotifier(this._ref) {
    _ref.listen(authProvider, (prev, next) {
      // Errors are handled locally by screens (toast) — they should never
      // trigger router/Navigator rebuilds, otherwise the active SnackBar
      // re-animates and looks like a duplicate toast.
      if (next is AsyncError) return;
      // Skip transient AsyncLoading where the data variant didn't change.
      if (prev?.valueOrNull?.runtimeType == next.valueOrNull?.runtimeType) {
        return;
      }
      notifyListeners();
    });
  }
}

/// Cached onboarding status — loaded once at startup, invalidated after onboarding completes
final onboardingDoneProvider = FutureProvider<bool>((ref) => isOnboardingDone());

final routerProvider = Provider<GoRouter>((ref) => buildRouter(ref));

GoRouter buildRouter(Ref ref) {
  final notifier = RouterNotifier(ref);

  return GoRouter(
    initialLocation: '/splash',
    refreshListenable: notifier,
    redirect: (context, state) {
      final authState = ref.read(authProvider);
      final isSplash = state.matchedLocation == '/splash';
      final isOnboarding = state.matchedLocation == '/onboarding';
      final isAuthRoute = state.matchedLocation.startsWith('/auth') ||
          state.matchedLocation == '/welcome';

      // Show splash only during initial load
      if (authState is AsyncLoading) {
        if (isSplash || isAuthRoute || isOnboarding) return null;
        return '/splash';
      }

      // Check onboarding status — must complete before anything else
      final onboardingDone = ref.read(onboardingDoneProvider).valueOrNull ?? false;
      if (!onboardingDone) {
        return isOnboarding ? null : '/onboarding';
      }
      if (isOnboarding) {
        return '/welcome';
      }

      final data = authState.valueOrNull;
      if (data == null) {
        // Error state — show login
        if (!isAuthRoute && !isSplash) return '/welcome';
        if (isSplash) return '/welcome';
        return null;
      }

      if (data is AuthAuthenticatedData || data is AuthAnonymousData) {
        return (isSplash || isAuthRoute) ? '/home' : null;
      }
      if (data is AuthNeedsDisplayNameData) return '/auth/set-name';
      if (data is AuthForceRegisterData) return '/auth/force-register';
      if (!isAuthRoute && !isSplash) return '/welcome';
      if (isSplash) return '/welcome';
      return null;
    },
    routes: [
      GoRoute(path: '/splash', builder: (_, __) => const SplashScreen()),
      GoRoute(path: '/onboarding', builder: (_, __) => const OnboardingScreen()),
      GoRoute(path: '/welcome', builder: (_, __) => const WelcomeScreen()),
      GoRoute(path: '/auth/display-name', builder: (_, __) => const DisplayNameScreen()),
      GoRoute(path: '/auth/register', builder: (_, __) => const RegisterScreen()),
      GoRoute(path: '/auth/otp', builder: (context, state) => OtpScreen(phone: state.extra as String)),
      GoRoute(path: '/auth/set-name', builder: (_, __) => const SetDisplayNameScreen()),
      GoRoute(path: '/auth/force-register', builder: (_, __) => const ForceRegisterScreen()),
      GoRoute(path: '/home', builder: (_, __) => const HomeScreen()),
      GoRoute(path: '/chat/searching', builder: (_, __) => const SearchingScreen()),
      GoRoute(path: '/chat/found', builder: (context, state) {
        final extra = state.extra as Map<String, dynamic>;
        return BestieFoundScreen(
          sessionId: extra['sessionId'] as String,
          mitraName: extra['mitraName'] as String,
        );
      }),
      GoRoute(path: '/chat/no-bestie', builder: (_, __) => const NoBestieScreen()),
      GoRoute(path: '/chat/session/:sessionId', builder: (context, state) {
        final extra = state.extra;
        final mitraName = extra is String
            ? extra
            : (extra is Map<String, dynamic> ? extra['mitraName'] as String? : null);
        return ChatScreen(
          sessionId: state.pathParameters['sessionId']!,
          mitraName: mitraName ?? 'Bestie',
        );
      }),
      GoRoute(path: '/chat/history', builder: (_, __) => const ChatHistoryScreen()),
      GoRoute(path: '/chat/history/:sessionId', builder: (context, state) {
        return ChatTranscriptScreen(sessionId: state.pathParameters['sessionId']!);
      }),
    ],
  );
}
