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/onboarding/screens/esp_screen.dart';
import 'features/onboarding/screens/notif_gate_screen.dart';
import 'features/onboarding/screens/usp_screen.dart';
import 'features/splash/splash_screen.dart';
import 'features/home/home_screen.dart';
import 'core/constants.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';
import 'features/chat/screens/targeted_waiting_screen.dart';
import 'features/payment/screens/payment_screen.dart';
import 'features/payment/screens/payment_entry_screen.dart';
import 'features/payment/screens/discount_paywall_screen.dart';
import 'features/payment/screens/method_pick_screen.dart';
import 'features/payment/screens/duration_pick_screen.dart';
import 'features/payment/screens/payment_method_screen.dart';
import 'features/payment/screens/waiting_payment_screen.dart';
import 'features/payment/screens/payment_expired_screen.dart';
import 'core/theme/_preview.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: kThemePreviewEnabled ? '/_theme_preview' : '/splash',
    refreshListenable: notifier,
    redirect: (context, state) {
      // Theme preview is dev-only and intentionally bypasses auth + onboarding
      // gates so it can be opened on any device build.
      if (state.matchedLocation == '/_theme_preview') return null;
      final authState = ref.read(authProvider);
      final isSplash = state.matchedLocation == '/splash';
      final isOnboarding = state.matchedLocation == '/onboarding';
      final isAuthRoute = state.matchedLocation.startsWith('/auth') ||
          state.matchedLocation == '/welcome';
      // Phase 4 onboarding flow (Verif Choice → ESP → USP) — must transit
      // freely while authState is AuthAnonymousData so the router doesn't
      // boot the user back to /home before they finish onboarding.
      final isOnboardingFlow =
          state.matchedLocation.startsWith('/onboarding/');

      // 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) {
        // Allow the Phase 4 onboarding flow (ESP/USP) to stay put even when
        // the user is already anonymous-authenticated — display_name_screen
        // intentionally pushes into /onboarding/* after loginAnonymous.
        if (isOnboardingFlow) return null;
        // display_name_screen owns the post-anonymous-login routing decision
        // (onboarding-state lookup → Verif Choice Sheet vs returning-user
        // jump). Don't preempt it by redirecting to /home the instant the
        // anonymous login resolves — wait until the screen pushes onward.
        if (data is AuthAnonymousData &&
            state.matchedLocation == '/auth/display-name') {
          return null;
        }
        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: [
      if (kThemePreviewEnabled)
        GoRoute(path: '/_theme_preview', builder: (_, __) => const ThemePreviewScreen()),
      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()),
      // Phase 4 onboarding sub-flow (Stage 2). Verified vs anonymous branch
      // share ESP + USP screens; the parent path drives the post-USP fork.
      GoRoute(
        path: '/onboarding/verif/esp',
        builder: (_, __) => const EspScreen(verified: true),
      ),
      GoRoute(
        path: '/onboarding/verif/usp',
        builder: (_, __) => const UspScreen(verified: true),
      ),
      GoRoute(
        path: '/onboarding/anon/esp',
        builder: (_, __) => const EspScreen(verified: false),
      ),
      GoRoute(
        path: '/onboarding/anon/usp',
        builder: (_, __) => const UspScreen(verified: false),
      ),
      // Phase 4 Stage 4 — post-payment OS-notif gate. Sits under the
      // `/onboarding/*` carve-out so the auth/onboarding redirect rules let
      // anonymous + authenticated users transit through unhindered.
      GoRoute(
        path: '/onboarding/notif-gate',
        builder: (_, __) => const NotifGateScreen(),
      ),
      // Alias for the OTP-blocked popup's "lanjut tanpa verif" exit. The
      // popup may fire from any point in the verified branch (after the
      // user has already passed ESP+USP), so we expose a stable terminal
      // landing-zone alias rather than rewriting all upstream pushes.
      GoRoute(
        path: '/onboarding/anon/method',
        redirect: (_, __) => '/payment/method-pick',
      ),
      GoRoute(path: '/home', builder: (_, __) => const HomeScreen()),
      GoRoute(path: '/payment', builder: (context, state) {
        // Legacy Phase 3.7 single-screen payment. Still reachable from
        //   - Home "Mulai Curhat" CTA  → no extras (general blast follows confirm)
        //   - Chat history "Curhat lagi" CTA → extras carry targetedMitraId/mitraName
        //     for the returning-chat flow, plus optional topicSensitivity.
        // Phase 4 Stage 3 introduces sibling routes under `/payment/*`; the new
        // entry point is `/payment/entry`. This route is preserved until Stage 5
        // migrates the chat-history "Curhat lagi" flow.
        final extra = state.extra;
        if (extra is Map<String, dynamic>) {
          final topic = extra['topicSensitivity'];
          return PaymentScreen(
            targetedMitraId: extra['targetedMitraId'] as String?,
            mitraName: extra['mitraName'] as String?,
            topicSensitivity: topic is TopicSensitivity ? topic : TopicSensitivity.regular,
          );
        }
        return const PaymentScreen();
      }),
      // Phase 4 Stage 3 — multi-screen payment shell.
      GoRoute(path: '/payment/entry', builder: (_, __) => const PaymentEntryScreen()),
      GoRoute(path: '/payment/discount-paywall', builder: (_, __) => const DiscountPaywallScreen()),
      GoRoute(path: '/payment/method-pick', builder: (_, __) => const MethodPickScreen()),
      GoRoute(path: '/payment/duration-pick', builder: (_, __) => const DurationPickScreen()),
      GoRoute(path: '/payment/method', builder: (_, __) => const PaymentMethodScreen()),
      GoRoute(
        path: '/payment/waiting/:paymentId',
        builder: (context, state) => WaitingPaymentScreen(
          paymentId: state.pathParameters['paymentId']!,
        ),
      ),
      GoRoute(
        path: '/payment/expired/:paymentId',
        builder: (context, state) => PaymentExpiredScreen(
          paymentId: state.pathParameters['paymentId']!,
        ),
      ),
      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()),
      // Phase 4 Stage 5 — targeted "Curhat lagi" 20s wait overlay. Pushed
      // after a confirmed targeted payment session; the pairing notifier
      // emits PairingTargetedWaitingData synchronously after the POST.
      GoRoute(
        path: '/chat/waiting-targeted/:mitraId',
        builder: (context, state) => TargetedWaitingScreen(
          mitraId: state.pathParameters['mitraId']!,
        ),
      ),
      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']!);
      }),
    ],
  );
}