import 'dart:async';

import 'package:facebook_app_events/facebook_app_events.dart';
import 'package:flutter/material.dart';
import 'package:flutter_native_splash/flutter_native_splash.dart';

import 'core/auth/auth_service.dart';
import 'core/nav/app_route_observer.dart';
import 'core/config/facebook_config.dart';
import 'core/log/app_logger.dart';
import 'core/theme/app_colors.dart';
import 'core/theme/app_theme.dart';
import 'core/user/user_state.dart';
import 'features/gallery/gallery_screen.dart';
import 'features/generate_video/generate_progress_screen.dart';
import 'features/generate_video/generate_video_screen.dart';
import 'features/gallery/models/gallery_task_item.dart';
import 'features/generate_video/generation_result_screen.dart';
import 'features/home/home_playback_resume.dart';
import 'features/home/home_screen.dart';
import 'features/home/models/task_item.dart';
import 'features/profile/profile_screen.dart';
import 'features/recharge/recharge_screen.dart';
import 'shared/widgets/bottom_nav_bar.dart';
import 'shared/tab_selector_scope.dart';

/// Root app widget with navigation
class App extends StatefulWidget {
  const App({super.key});

  @override
  State<App> createState() => _AppState();
}

class _AppState extends State<App> with WidgetsBindingObserver {
  NavTab _currentTab = NavTab.home;

  static final _fbLog = AppLogger('FB');
  final FacebookAppEvents _fbAppEvents = FacebookAppEvents();

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
    // Cold start is often already resumed, so lifecycle may not emit resumed—fire once after first frame.
    WidgetsBinding.instance.addPostFrameCallback((_) {
      // Remove native splash; Flutter login overlay takes over if startup is still running.
      FlutterNativeSplash.remove();
      _reportFacebookActivateApp('first_frame');
    });
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  /// With `AutoLogAppEventsEnabled=false`, manually report Facebook install + activateApp.
  void _reportFacebookActivateApp(String reason) {
    _fbAppEvents.activateApp().then((_) {
      if (FacebookConfig.debugLogs) {
        _fbLog.d('activateApp (manual: $reason)');
      }
    });
  }

  /// Foreground resume; cold start also uses addPostFrameCallback in initState.
  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.resumed) {
      _reportFacebookActivateApp('lifecycle_resumed');
    }
  }

  @override
  Widget build(BuildContext context) {
    return UserCreditsScope(
      child: TabSelectorScope(
        selectTab: (tab) => setState(() => _currentTab = tab),
        child: MaterialApp(
          title: 'AI Video App',
          theme: AppTheme.light,
          debugShowCheckedModeBanner: false,
          navigatorObservers: [appRouteObserver],
          initialRoute: '/',
          builder: (context, child) {
            return Stack(
              fit: StackFit.expand,
              children: [
                SafeArea(
                  top: true,
                  left: false,
                  right: false,
                  bottom: false,
                  child: child ?? const SizedBox.shrink(),
                ),
                ListenableBuilder(
                  listenable: AuthService.isLoginComplete,
                  builder: (context, _) {
                    if (AuthService.isLoginComplete.value) {
                      return const SizedBox.shrink();
                    }
                    return const _StartupLoginOverlay();
                  },
                ),
              ],
            );
          },
          routes: {
            '/': (_) => _MainScaffold(
                  currentTab: _currentTab,
                  onTabSelected: (tab) => setState(() => _currentTab = tab),
                ),
          '/recharge': (_) => const RechargeScreen(),
          '/generate': (ctx) {
            final task = ModalRoute.of(ctx)?.settings.arguments as TaskItem?;
            return GenerateVideoScreen(task: task);
          },
          '/progress': (ctx) {
            final args = ModalRoute.of(ctx)?.settings.arguments;
            final taskId = args is Map ? args['taskId'] : args;
            final imagePath = args is Map ? args['imagePath'] as String? : null;
            return GenerateProgressScreen(
              taskId: taskId,
              imagePath: imagePath,
            );
          },
          '/result': (ctx) {
            final mediaItem =
                ModalRoute.of(ctx)?.settings.arguments as GalleryMediaItem?;
            return GenerationResultScreen(mediaItem: mediaItem);
          },
        },
        ),
      ),
    );
  }
}

/// Full-screen wait until [AuthService.loginComplete]; after a delay, show a gentle network hint.
class _StartupLoginOverlay extends StatefulWidget {
  const _StartupLoginOverlay();

  @override
  State<_StartupLoginOverlay> createState() => _StartupLoginOverlayState();
}

class _StartupLoginOverlayState extends State<_StartupLoginOverlay> {
  static const _longWaitAfter = Duration(seconds: 22);
  Timer? _longWaitTimer;
  bool _showNetworkHint = false;

  @override
  void initState() {
    super.initState();
    _longWaitTimer = Timer(_longWaitAfter, () {
      if (mounted) setState(() => _showNetworkHint = true);
    });
  }

  @override
  void dispose() {
    _longWaitTimer?.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Positioned.fill(
      child: AbsorbPointer(
        child: Container(
          color: Colors.black.withValues(alpha: 0.22),
          child: Center(
            child: Padding(
              padding: const EdgeInsets.symmetric(horizontal: 28),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  const CircularProgressIndicator(color: AppColors.primary),
                  if (_showNetworkHint) ...[
                    const SizedBox(height: 22),
                    Text(
                      'Still getting things ready',
                      textAlign: TextAlign.center,
                      style: TextStyle(
                        color: AppColors.surface.withValues(alpha: 0.96),
                        fontSize: 16,
                        fontWeight: FontWeight.w600,
                      ),
                    ),
                    const SizedBox(height: 10),
                    Text(
                      'This is slower than usual—your connection may be weak. Check Wi‑Fi or mobile data; loading will continue automatically. You can also fully close the app and open it again.',
                      textAlign: TextAlign.center,
                      style: TextStyle(
                        color: AppColors.surface.withValues(alpha: 0.78),
                        fontSize: 14,
                        height: 1.4,
                      ),
                    ),
                  ],
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}

class _MainScaffold extends StatefulWidget {
  const _MainScaffold({
    required this.currentTab,
    required this.onTabSelected,
  });

  final NavTab currentTab;
  final ValueChanged<NavTab> onTabSelected;

  @override
  State<_MainScaffold> createState() => _MainScaffoldState();
}

class _MainScaffoldState extends State<_MainScaffold> with RouteAware {
  bool _routeObserverSubscribed = false;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    if (!_routeObserverSubscribed) {
      final route = ModalRoute.of(context);
      if (route is PageRoute<dynamic>) {
        appRouteObserver.subscribe(this, route);
        _routeObserverSubscribed = true;
      }
    }
  }

  @override
  void dispose() {
    if (_routeObserverSubscribed) {
      appRouteObserver.unsubscribe(this);
    }
    super.dispose();
  }

  /// Subscribed on `/` [PageRoute]: fires when a pushed route is popped and home is visible again.
  @override
  void didPopNext() {
    if (widget.currentTab == NavTab.home) {
      homePlaybackResumeNonce.value++;
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          ListenableBuilder(
            listenable: AuthService.startupUiListenable,
            builder: (context, _) {
              if (!AuthService.shouldShowStartupFailure) {
                return const SizedBox.shrink();
              }
              final msg = AuthService.startupFailureMessage.value ??
                  'We couldn’t finish loading. Check your network and tap Retry.';
              return Material(
                color: const Color(0xFFFFF3E0),
                child: Padding(
                  padding: const EdgeInsets.fromLTRB(16, 10, 12, 10),
                  child: Row(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Icon(
                        Icons.wifi_off_rounded,
                        color: AppColors.primary.withValues(alpha: 0.85),
                        size: 22,
                      ),
                      const SizedBox(width: 12),
                      Expanded(
                        child: Text(
                          msg,
                          style: TextStyle(
                            color: Colors.brown.shade800,
                            fontSize: 14,
                            height: 1.35,
                          ),
                        ),
                      ),
                      TextButton(
                        onPressed: () async {
                          await AuthService.retryStartup();
                        },
                        child: const Text('Retry'),
                      ),
                    ],
                  ),
                ),
              );
            },
          ),
          Expanded(
            child: IndexedStack(
              index: widget.currentTab.index,
              children: [
                HomeScreen(isActive: widget.currentTab == NavTab.home),
                GalleryScreen(isActive: widget.currentTab == NavTab.gallery),
                ProfileScreen(isActive: widget.currentTab == NavTab.profile),
              ],
            ),
          ),
        ],
      ),
      bottomNavigationBar: BottomNavBar(
        currentTab: widget.currentTab,
        onTabSelected: widget.onTabSelected,
      ),
    );
  }
}