import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';

import '../auth/auth_provider.dart';
import '../../features/auth/login_screen.dart';
import '../../features/auth/register_screen.dart';
import '../../features/home/home_screen.dart';
import '../../features/onboarding/onboarding_screen.dart';
import '../../features/profile/profile_provider.dart';
import '../../shared/models/user.dart';
import '../../features/products/products_screen.dart';
import '../../features/products/add_product_screen.dart';
import '../../features/scan/scan_screen.dart';
import '../../features/scan/recognition_confirm_screen.dart';
import '../../features/scan/recognition_service.dart';
import '../../features/menu/menu_screen.dart';
import '../../features/menu/shopping_list_screen.dart';
import '../../features/recipes/recipe_detail_screen.dart';
import '../../features/recipes/recipes_screen.dart';
import '../../features/profile/profile_screen.dart';
import '../../features/products/product_provider.dart';
import '../../features/scan/recognition_history_screen.dart';
import '../../shared/models/recipe.dart';
import '../../shared/models/saved_recipe.dart';

// Notifies GoRouter when auth state or profile state changes.
class _RouterNotifier extends ChangeNotifier {
  _RouterNotifier(Ref ref) {
    ref.listen<AuthState>(authProvider, (previous, next) {
      // Reload profile whenever auth transitions to authenticated.
      // This handles the case where profileProvider did an initial load before
      // tokens were available (401 → AsyncError) and needs a fresh load after login.
      if (next.status == AuthStatus.authenticated &&
          previous?.status != AuthStatus.authenticated) {
        ref.read(profileProvider.notifier).load();
      }
      notifyListeners();
    });
    ref.listen<AsyncValue<User>>(profileProvider, (_, __) => notifyListeners());
  }
}

final routerProvider = Provider<GoRouter>((ref) {
  final notifier = _RouterNotifier(ref);
  ref.onDispose(notifier.dispose);

  return GoRouter(
    initialLocation: '/loading',
    refreshListenable: notifier,
    redirect: (context, state) {
      // Use ref.read — this runs inside GoRouter, not inside a Riverpod build.
      final authState = ref.read(authProvider);
      final isLoggedIn = authState.status == AuthStatus.authenticated;
      final isAuthRoute = state.matchedLocation.startsWith('/auth');
      final isOnboarding = state.matchedLocation.startsWith('/onboarding');

      // Show splash until the stored-token check completes.
      if (authState.status == AuthStatus.unknown) return '/loading';
      if (!isLoggedIn && !isAuthRoute) return '/auth/login';

      if (isLoggedIn) {
        // Reading profileProvider triggers its lazy initialization (load() in constructor).
        final profileState = ref.read(profileProvider);
        // Keep showing splash while profile loads.
        if (profileState.isLoading) {
          return state.matchedLocation == '/loading' ? null : '/loading';
        }
        final profileUser = profileState.valueOrNull;
        // If profile failed to load, don't block navigation.
        if (profileUser == null) {
          if (isAuthRoute || state.matchedLocation == '/loading') return '/home';
          return null;
        }

        final needsOnboarding = !profileUser.hasCompletedOnboarding;
        if (isAuthRoute || state.matchedLocation == '/loading') {
          return needsOnboarding ? '/onboarding' : '/home';
        }
        if (needsOnboarding && !isOnboarding) return '/onboarding';
        if (!needsOnboarding && isOnboarding) return '/home';
      }

      return null;
    },
    routes: [
      // Splash shown while auth status is unknown.
      GoRoute(
        path: '/loading',
        builder: (_, __) => const _SplashScreen(),
      ),
      GoRoute(
        path: '/auth/login',
        builder: (_, __) => const LoginScreen(),
      ),
      GoRoute(
        path: '/auth/register',
        builder: (_, __) => const RegisterScreen(),
      ),
      // Onboarding — full-screen, no bottom nav, shown to new users.
      GoRoute(
        path: '/onboarding',
        builder: (_, __) => const OnboardingScreen(),
      ),
      // Full-screen recipe detail — shown without the bottom navigation bar.
      GoRoute(
        path: '/recipe-detail',
        builder: (context, state) {
          final extra = state.extra;
          if (extra is Recipe) {
            return RecipeDetailScreen(recipe: extra);
          }
          if (extra is SavedRecipe) {
            return RecipeDetailScreen(saved: extra);
          }
          return const _InvalidRoute();
        },
      ),
      // Add product — shown without the bottom navigation bar.
      GoRoute(
        path: '/products/add',
        builder: (_, __) => const AddProductScreen(),
      ),
      // Shopping list — full-screen, no bottom nav.
      GoRoute(
        path: '/menu/shopping-list',
        builder: (context, state) {
          final week = state.extra as String? ?? '';
          return ShoppingListScreen(week: week);
        },
      ),
      // Scan / recognition flow — all without bottom nav.
      GoRoute(
        path: '/scan',
        builder: (_, __) => const ScanScreen(),
      ),
      GoRoute(
        path: '/scan/confirm',
        builder: (context, state) {
          final items = state.extra as List<RecognizedItem>? ?? [];
          return RecognitionConfirmScreen(items: items);
        },
      ),
      GoRoute(
        path: '/scan/history',
        builder: (_, __) => const RecognitionHistoryScreen(),
      ),
      ShellRoute(
        builder: (context, state, child) => MainShell(child: child),
        routes: [
          GoRoute(path: '/home', builder: (_, __) => const HomeScreen()),
          GoRoute(
              path: '/products',
              builder: (_, __) => const ProductsScreen()),
          GoRoute(path: '/menu', builder: (_, __) => const MenuScreen()),
          GoRoute(
              path: '/recipes', builder: (_, __) => const RecipesScreen()),
          GoRoute(
              path: '/profile', builder: (_, __) => const ProfileScreen()),
        ],
      ),
    ],
  );
});

class _SplashScreen extends StatelessWidget {
  const _SplashScreen();

  @override
  Widget build(BuildContext context) => const Scaffold(
        body: Center(child: CircularProgressIndicator()),
      );
}

class _InvalidRoute extends StatelessWidget {
  const _InvalidRoute();

  @override
  Widget build(BuildContext context) {
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (context.mounted) Navigator.of(context).pop();
    });
    return const Scaffold(body: SizedBox.shrink());
  }
}

class MainShell extends ConsumerWidget {
  final Widget child;

  const MainShell({super.key, required this.child});

  static const _tabs = [
    '/home',
    '/products',
    '/menu',
    '/recipes',
    '/profile',
  ];

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final location = GoRouterState.of(context).matchedLocation;
    final currentIndex = _tabs.indexOf(location).clamp(0, _tabs.length - 1);

    // Count products expiring soon for the badge.
    final expiringCount = ref.watch(productsProvider).maybeWhen(
          data: (products) => products.where((p) => p.expiringSoon).length,
          orElse: () => 0,
        );

    return Scaffold(
      body: child,
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: currentIndex,
        onTap: (index) => context.go(_tabs[index]),
        items: [
          const BottomNavigationBarItem(
            icon: Icon(Icons.home),
            label: 'Главная',
          ),
          BottomNavigationBarItem(
            icon: Badge(
              isLabelVisible: expiringCount > 0,
              label: Text('$expiringCount'),
              child: const Icon(Icons.kitchen),
            ),
            label: 'Продукты',
          ),
          const BottomNavigationBarItem(
            icon: Icon(Icons.calendar_month),
            label: 'Меню',
          ),
          const BottomNavigationBarItem(
            icon: Icon(Icons.menu_book),
            label: 'Рецепты',
          ),
          const BottomNavigationBarItem(
            icon: Icon(Icons.person),
            label: 'Профиль',
          ),
        ],
      ),
    );
  }
}