import 'dart:async';
import 'dart:developer';

import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:persistent_bottom_nav_bar_v2/persistent_bottom_nav_bar_v2.dart';

import 'api/mhsl/breaker/get_breakers/get_breakers_response.dart';
import 'api/mhsl/server/user_index/update/update_userindex.dart';
import 'main.dart';
import 'model/data_cleaner.dart';
import 'notification/notification_controller.dart';
import 'notification/notification_tasks.dart';
import 'notification/notify_updater.dart';
import 'state/app/modules/app_modules.dart';
import 'state/app/modules/breaker/bloc/breaker_bloc.dart';
import 'state/app/modules/chat_list/bloc/chat_list_bloc.dart';
import 'state/app/modules/settings/bloc/settings_cubit.dart';
import 'state/app/modules/timetable/bloc/timetable_bloc.dart';
import 'storage/settings.dart' as model;
import 'utils/debouncer.dart';
import 'view/pages/overhang.dart';
import 'widget/breaker/breaker.dart';

class App extends StatefulWidget {
  const App({super.key});

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

class _AppState extends State<App> with WidgetsBindingObserver {
  late Timer _refetchChats;
  late Timer _updateTimings;
  // Tracked via the bottom-nav controller's listener so it always reflects the
  // user's actual position, even between rapid setting emits where the
  // controller hasn't caught up to a scheduled jump yet.
  int _knownTotalTabs = 1;
  bool _userOnLastTab = false;

  void _onTabControllerChanged() {
    _userOnLastTab = Main.bottomNavigator.index == _knownTotalTabs - 1;
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    log('AppLifecycle: $state');
    if (state == AppLifecycleState.resumed) {
      Debouncer.throttle('appLifecycleState', const Duration(seconds: 10), () {
        if (!mounted) return;
        log('Refreshing due to LifecycleChange');
        NotificationTasks.updateProviders(context);
      });
    }
  }

  @override
  void initState() {
    super.initState();
    Main.bottomNavigator = PersistentTabController(initialIndex: 0);
    Main.bottomNavigator.addListener(_onTabControllerChanged);
    WidgetsBinding.instance.addObserver(this);

    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted) return;
      context.read<BreakerBloc>().refresh();
      context.read<ChatListBloc>().refresh();
      // App is freshly mounted on every login (BlocConsumer in main.dart
      // swaps it in for Login), so this also covers the post-logout case
      // where the bloc was reset to an empty state and needs a fresh fetch.
      context.read<TimetableBloc>().refresh();
    });

    _updateTimings = Timer.periodic(const Duration(seconds: 30), (_) {
      if (mounted) setState(() {});
    });

    _refetchChats = Timer.periodic(const Duration(seconds: 60), (_) {
      WidgetsBinding.instance.addPostFrameCallback((_) {
        if (!mounted) return;
        context.read<ChatListBloc>().refresh();
      });
    });

    UpdateUserIndex.index();

    if (context.read<SettingsCubit>().val().notificationSettings.enabled) {
      void update() => NotifyUpdater.registerToServer();
      FirebaseMessaging.instance.onTokenRefresh.listen((_) => update());
      update();
    }

    FirebaseMessaging.onMessage.listen((message) {
      if (!mounted) return;
      NotificationController.onForegroundMessageHandler(message, context);
    });
    FirebaseMessaging.onBackgroundMessage(NotificationController.onBackgroundMessageHandler);

    FirebaseMessaging.onMessageOpenedApp.listen((message) {
      if (!mounted) return;
      NotificationController.onAppOpenedByNotification(message, context);
    });
    FirebaseMessaging.instance.getInitialMessage().then((message) {
      if (message == null || !mounted) return;
      NotificationController.onAppOpenedByNotification(message, context);
    });

    DataCleaner.cleanOldCache();
  }

  @override
  void dispose() {
    _refetchChats.cancel();
    _updateTimings.cancel();
    Main.bottomNavigator.removeListener(_onTabControllerChanged);
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  Widget build(BuildContext context) => BlocBuilder<SettingsCubit, model.Settings>(
        builder: (context, _) {
          final bottomBarModules = AppModule.getBottomBarModules(context);
          final totalTabs = bottomBarModules.length + 1;
          final currentIndex = Main.bottomNavigator.index;

          // The bottom-bar layout is identified by the ordered list of module
          // names plus the trailing 'more' slot. Whenever this layout changes
          // — slot count, reordering, or hiding a module — we recreate the
          // entire PersistentTabView via the [layoutKey] below. The package
          // caches per-tab navigator state by index in `_navigatorKeys`, and
          // its internal `alignLength` only ever appends or trims at the end.
          // So when the module sitting at e.g. index 3 changes, the navigator
          // at that index still serves the old screen's route stack and the
          // user sees stale content. Re-mounting clears those stacks; the
          // trade-off (losing in-tab pushed routes on a settings change) is
          // acceptable since the user explicitly re-shaped the bar.
          final layoutKey = ValueKey('${bottomBarModules.map((m) => m.module.name).join('|')}|more');

          if (totalTabs != _knownTotalTabs) {
            var targetIndex = currentIndex;
            if (_userOnLastTab) {
              targetIndex = totalTabs - 1;
            } else if (currentIndex >= totalTabs) {
              targetIndex = totalTabs - 1;
            }
            // Re-mounting PTV with a new key constructs fresh internals from
            // its controller's current index. If the controller still points
            // past the new tab list, Style6BottomNavBar (and others) crash on
            // out-of-range access during initState. Replace the controller
            // atomically with one initialised at the safe target index so the
            // new PTV mounts cleanly.
            if (targetIndex != currentIndex) {
              Main.bottomNavigator.removeListener(_onTabControllerChanged);
              Main.bottomNavigator = PersistentTabController(initialIndex: targetIndex);
              Main.bottomNavigator.addListener(_onTabControllerChanged);
              _userOnLastTab = targetIndex == totalTabs - 1;
            }
          }

          _knownTotalTabs = totalTabs;

          return PersistentTabView(
            key: layoutKey,
            controller: Main.bottomNavigator,
            navBarOverlap: const NavBarOverlap.none(),
            backgroundColor: Theme.of(context).colorScheme.primary,
            handleAndroidBackButtonPress: true,
            screenTransitionAnimation: const ScreenTransitionAnimation(
              curve: Curves.easeOutQuad,
              duration: Duration(milliseconds: 200),
            ),
            tabs: [
              ...bottomBarModules.map((e) => e.toBottomTab(context)),
              PersistentTabConfig(
                screen: const Breaker(breaker: BreakerArea.more, child: Overhang()),
                item: ItemConfig(
                  activeForegroundColor: Theme.of(context).primaryColor,
                  inactiveForegroundColor: Theme.of(context).colorScheme.secondary,
                  icon: const Icon(Icons.apps),
                  title: 'Mehr',
                ),
              ),
            ],
            navBarBuilder: (config) => Style6BottomNavBar(
              // Style6BottomNavBar builds its internal animation controller list
              // in initState and never grows it on didUpdateWidget. Keying by the
              // item count forces a fresh State whenever the slot count changes,
              // which avoids a RangeError when more tabs slide in.
              key: ValueKey(config.items.length),
              navBarConfig: config,
              navBarDecoration: NavBarDecoration(
                border: const Border(top: BorderSide(width: 1, color: Colors.grey)),
                color: Theme.of(context).colorScheme.surface,
              ),
            ),
          );
        },
      );
}