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

import '../../../core/network/supabase_status.dart';
import '../../features/auth/presentation/controllers/auth_controller.dart';
import '../../features/auth/presentation/controllers/dev_auth_bypass.dart';
import '../../features/auth/presentation/screens/login_screen.dart';
import '../../features/exercise/presentation/screens/exercise_screen.dart';
import '../../features/medication/presentation/screens/medication_screen.dart';
import '../../features/nutrition/presentation/screens/nutrition_screen.dart';
import '../../features/nutrition/presentation/screens/food_search_screen.dart';
import '../../features/meal_planner/presentation/screens/meal_planner_screen.dart';
import '../../features/pantry/presentation/screens/pantry_screen.dart';
import '../../features/recipes/presentation/screens/recipes_screen.dart';
import '../../features/settings/presentation/screens/settings_screen.dart';
import '../scaffold/adaptive_home_scaffold.dart';

/// Locations that may be visited without an authenticated session.
const Set<String> _publicPaths = {'/login'};

final _rootNavigatorKey = GlobalKey<NavigatorState>();
final _shellNavigatorKey = GlobalKey<NavigatorState>();

/// Whether the current session satisfies the authenticated guard.
///
/// Reads the live GoTrue session when the SDK is initialized and reports
/// `false` otherwise. Watches [authStateProvider] so the value is re-derived
/// on every GoTrue transition — `currentSession` itself is a plain, non
/// reactive getter, so without the watch this provider would cache whatever
/// was true at first read (e.g. booting already signed-in) and a later
/// sign-out could never redirect to `/login`. Extracted into a provider so
/// integration tests can simulate an authenticated (or unauthenticated)
/// session without booting Supabase — they simply override this value.
final isAuthenticatedProvider = Provider<bool>(
  (ref) {
    // Recompute on every auth transition (signedIn / signedOut /
    // tokenRefreshed / initialSession).
    ref.watch(authStateProvider);
    return isSupabaseAvailable &&
        Supabase.instance.client.auth.currentSession != null;
  },
);

/// Application router with a reactive authentication guard and dev bypass hook.
final routerProvider = Provider<GoRouter>((ref) {
  final authRefreshNotifier = ValueNotifier<int>(0);
  ref.onDispose(authRefreshNotifier.dispose);

  // Trigger re-evaluation on GoTrue auth transitions or dev bypass toggle.
  //
  // The auth bump is deferred by one microtask so Riverpod finishes
  // propagating the transition to dependent providers (notably
  // isAuthenticatedProvider, which watches authStateProvider) before the
  // redirect guard re-reads them; ValueNotifier listeners otherwise run
  // inside the provider-notification cascade and could observe a stale
  // cached value (symptom: sign-out clears the session but never navigates
  // to /login).
  ref.listen(authStateProvider, (_, __) {
    Future.microtask(() => authRefreshNotifier.value++);
  });
  ref.listen(devAuthBypassProvider, (_, __) => authRefreshNotifier.value++);

  return GoRouter(
    navigatorKey: _rootNavigatorKey,
    initialLocation: '/medication',
    refreshListenable: authRefreshNotifier,
    redirect: (context, state) => _authGuard(context, state, ref),
    routes: [
      GoRoute(
        path: '/login',
        builder: (context, state) => const LoginScreen(),
      ),
      // Full-screen food search (pushed above the shell so it covers the
      // navigation rail). `?preset=pantry` reorders the product action
      // sheet to emphasize adding to pantry stock.
      GoRoute(
        path: '/food-search',
        builder: (context, state) => FoodSearchScreen(
          preset: foodSearchPresetFrom(state.uri.queryParameters['preset']),
        ),
      ),
      ShellRoute(
        navigatorKey: _shellNavigatorKey,
        builder: (context, state, child) {
          return AdaptiveHomeScaffold(child: child);
        },
        routes: [
          GoRoute(
            path: '/medication',
            builder: (context, state) => const MedicationScreen(),
          ),
          GoRoute(
            path: '/nutrition',
            builder: (context, state) => const NutritionScreen(),
          ),
          GoRoute(
            path: '/exercise',
            builder: (context, state) => const ExerciseScreen(),
          ),
          GoRoute(
            path: '/meal-planner',
            builder: (context, state) => const MealPlannerScreen(),
          ),
          GoRoute(
            path: '/recipes',
            builder: (context, state) => const RecipesScreen(),
          ),
          GoRoute(
            path: '/pantry',
            builder: (context, state) => const PantryScreen(),
          ),
          GoRoute(
            path: '/settings',
            builder: (context, state) => const SettingsScreen(),
          ),
        ],
      ),
    ],
  );
});

/// Redirect guard enforcing the passwordless session lifecycle with dev bypass.
///
/// * Development bypass (debug builds only): `/login` -> `/medication`, all
///   other routes pass without a session.
/// * Unauthenticated sessions on a protected route -> `/login`.
/// * Authenticated sessions on `/login` -> `/medication`.
String? _authGuard(BuildContext context, GoRouterState state, Ref ref) {
  final isDevBypassed = ref.read(devAuthBypassProvider);
  final location = state.matchedLocation;

  if (isDevBypassed) {
    if (location == '/login') return '/medication';
    return null;
  }

  final isAuthenticated = ref.read(isAuthenticatedProvider);

  if (!isAuthenticated && !_publicPaths.contains(location)) {
    return '/login';
  }
  if (isAuthenticated && location == '/login') {
    return '/medication';
  }
  return null;
}