import 'dart:convert';
import 'dart:io';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter/material.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:travel_mate/components/account/group_expenses_page.dart';
import 'package:travel_mate/components/activities/activities_page.dart';
import 'package:travel_mate/components/group/chat_group_content.dart';
import 'package:travel_mate/components/home/show_trip_details_content.dart';
import 'package:travel_mate/repositories/account_repository.dart';
import 'package:travel_mate/repositories/group_repository.dart';
import 'package:travel_mate/repositories/trip_invitation_repository.dart';
import 'package:travel_mate/repositories/trip_repository.dart';
import 'package:travel_mate/services/error_service.dart';
import 'package:travel_mate/services/logger_service.dart';
import 'package:travel_mate/services/notification_payload_parser.dart';

@pragma('vm:entry-point')
Future<void> firebaseMessagingBackgroundHandler(RemoteMessage message) async {
  await Firebase.initializeApp();
  LoggerService.info('Handling a background message: ${message.messageId}');
}

class NotificationService {
  static final NotificationService _instance = NotificationService._internal();
  factory NotificationService() => _instance;
  NotificationService._internal();

  late final FirebaseMessaging _firebaseMessaging = FirebaseMessaging.instance;
  late final FlutterLocalNotificationsPlugin _localNotifications =
      FlutterLocalNotificationsPlugin();

  final TripRepository _tripRepository = TripRepository();
  final GroupRepository _groupRepository = GroupRepository();
  final AccountRepository _accountRepository = AccountRepository();
  final TripInvitationRepository _tripInvitationRepository =
      TripInvitationRepository();

  bool _isInitialized = false;
  bool _isInvitationDialogOpen = false;

  /// Initialise les permissions et listeners de notifications.
  ///
  /// Cette méthode est idempotente: les initialisations déjà faites ne sont
  /// pas rejouées.
  Future<void> initialize() async {
    if (_isInitialized) return;

    await _requestPermissions();

    const androidSettings = AndroidInitializationSettings(
      '@mipmap/ic_launcher',
    );
    const iosSettings = DarwinInitializationSettings();
    const initSettings = InitializationSettings(
      android: androidSettings,
      iOS: iosSettings,
    );

    await _localNotifications.initialize(
      initSettings,
      onDidReceiveNotificationResponse: (details) {
        LoggerService.info('Notification tapped: ${details.payload}');
        if (details.payload == null || details.payload!.isEmpty) {
          return;
        }

        try {
          final data = json.decode(details.payload!) as Map<String, dynamic>;
          _handleNotificationTap(data);
        } catch (e) {
          LoggerService.error('Error parsing notification payload', error: e);
        }
      },
    );

    FirebaseMessaging.onMessage.listen(_handleForegroundMessage);
    FirebaseMessaging.instance.onTokenRefresh.listen(_onTokenRefresh);

    _isInitialized = true;
    LoggerService.info('NotificationService initialized');

    final token = await getFCMToken();
    LoggerService.info('Current FCM Token: $token');
  }

  /// Démarre l'écoute des interactions de notifications en arrière-plan.
  ///
  /// À appeler quand l'arbre de navigation est prêt.
  void startListening() {
    FirebaseMessaging.onMessageOpenedApp.listen((RemoteMessage message) {
      _handleNotificationTap(message.data);
    });
  }

  /// Traite une notification ayant ouvert l'app depuis l'état terminé.
  Future<void> handleInitialMessage() async {
    final initialMessage = await _firebaseMessaging.getInitialMessage();

    if (initialMessage != null) {
      LoggerService.info('Found initial message: ${initialMessage.data}');
      _handleNotificationTap(initialMessage.data);
    }
  }

  /// Exécute l'action métier/navigation associée à un payload push.
  ///
  /// Le routage se base en priorité sur `type`, puis sur un fallback par clés.
  Future<void> _handleNotificationTap(Map<String, dynamic> data) async {
    LoggerService.info('Handling notification tap with data: $data');

    final action = NotificationPayloadParser.parse(data);

    try {
      switch (action.type) {
        case 'message':
          if (action.groupId != null) {
            await _openGroupChat(action.groupId!);
          }
          return;
        case 'expense':
          if (action.tripId != null) {
            await _openExpenses(action.tripId!);
            return;
          }
          if (action.groupId != null) {
            final tripId = await _resolveTripIdFromGroup(action.groupId!);
            if (tripId != null) {
              await _openExpenses(tripId);
            }
          }
          return;
        case 'activity':
          if (action.tripId != null) {
            await _openActivities(action.tripId!);
          }
          return;
        case 'trip_invitation':
          await _showTripInvitationDialog(action);
          return;
        case 'trip_invitation_response':
        case 'trip':
          if (action.tripId != null) {
            await _openTripDetails(action.tripId!);
          }
          return;
        default:
          if (action.groupId != null) {
            await _openGroupChat(action.groupId!);
            return;
          }
          if (action.tripId != null) {
            await _openTripDetails(action.tripId!);
            return;
          }
          LoggerService.info('Unknown notification payload: $data');
      }
    } catch (e) {
      LoggerService.error('Error handling notification tap: $e');
      ErrorService().showError(message: 'Erreur navigation: $e');
    }
  }

  /// Ouvre la discussion du groupe ciblé.
  ///
  /// Ne fait rien si le groupe n'existe plus ou n'est pas accessible.
  Future<void> _openGroupChat(String groupId) async {
    final group = await _groupRepository.getGroupById(groupId);
    if (group == null) {
      LoggerService.error('Group not found: $groupId');
      return;
    }

    ErrorService.navigatorKey.currentState?.push(
      MaterialPageRoute(builder: (context) => ChatGroupContent(group: group)),
    );
  }

  /// Ouvre la page des dépenses pour un voyage.
  ///
  /// Nécessite que le groupe et le compte du voyage soient disponibles.
  Future<void> _openExpenses(String tripId) async {
    final account = await _accountRepository.getAccountByTripId(tripId);
    final group = await _groupRepository.getGroupByTripId(tripId);

    if (account == null || group == null) {
      LoggerService.error('Account or Group not found for trip: $tripId');
      return;
    }

    ErrorService.navigatorKey.currentState?.push(
      MaterialPageRoute(
        builder: (context) => GroupExpensesPage(account: account, group: group),
      ),
    );
  }

  /// Ouvre la page de détail d'un voyage.
  ///
  /// Retourne silencieusement si le voyage n'existe plus.
  Future<void> _openTripDetails(String tripId) async {
    final trip = await _tripRepository.getTripById(tripId);
    if (trip == null) {
      LoggerService.error('Trip not found: $tripId');
      return;
    }

    ErrorService.navigatorKey.currentState?.push(
      MaterialPageRoute(
        builder: (context) => ShowTripDetailsContent(trip: trip),
      ),
    );
  }

  /// Ouvre la page des activités du voyage ciblé.
  ///
  /// Cette navigation est utilisée pour les notifications d'ajout d'activité.
  Future<void> _openActivities(String tripId) async {
    final trip = await _tripRepository.getTripById(tripId);
    if (trip == null) {
      LoggerService.error('Trip not found for activities: $tripId');
      return;
    }

    ErrorService.navigatorKey.currentState?.push(
      MaterialPageRoute(builder: (context) => ActivitiesPage(trip: trip)),
    );
  }

  /// Affiche un popup d'invitation de voyage et traite la réponse utilisateur.
  ///
  /// Si [action.invitationId] est absent, aucun popup n'est affiché.
  Future<void> _showTripInvitationDialog(NotificationAction action) async {
    if (_isInvitationDialogOpen || action.invitationId == null) {
      return;
    }

    final context = ErrorService.navigatorKey.currentContext;
    if (context == null) {
      LoggerService.error('Cannot show invitation dialog: missing context');
      return;
    }

    _isInvitationDialogOpen = true;

    final inviterName = action.inviterName ?? 'Quelqu\'un';
    final tripTitle = action.tripTitle ?? 'ce voyage';

    await showDialog<void>(
      context: context,
      barrierDismissible: false,
      builder: (dialogContext) {
        return AlertDialog(
          title: const Text('Invitation de voyage'),
          content: Text('$inviterName vous invite à rejoindre "$tripTitle".'),
          actions: [
            TextButton(
              onPressed: () async {
                Navigator.of(dialogContext).pop();
                await _tripInvitationRepository.respondToInvitation(
                  invitationId: action.invitationId!,
                  isAccepted: false,
                );
                ErrorService().showSnackbar(
                  message: 'Invitation refusée',
                  isError: false,
                );
              },
              child: const Text('Refuser'),
            ),
            ElevatedButton(
              onPressed: () async {
                Navigator.of(dialogContext).pop();
                await _tripInvitationRepository.respondToInvitation(
                  invitationId: action.invitationId!,
                  isAccepted: true,
                );
                ErrorService().showSnackbar(
                  message: 'Invitation acceptée',
                  isError: false,
                );
                if (action.tripId != null) {
                  await _openTripDetails(action.tripId!);
                }
              },
              child: const Text('Rejoindre'),
            ),
          ],
        );
      },
    );

    _isInvitationDialogOpen = false;
  }

  /// Résout un `tripId` à partir d'un `groupId`.
  ///
  /// Retourne `null` si le groupe est introuvable.
  Future<String?> _resolveTripIdFromGroup(String groupId) async {
    final group = await _groupRepository.getGroupById(groupId);
    return group?.tripId;
  }

  /// Callback lors du refresh d'un token FCM.
  ///
  /// Quand un utilisateur est connecté, le nouveau token est persisté
  /// immédiatement pour éviter toute perte de notifications.
  Future<void> _onTokenRefresh(String newToken) async {
    LoggerService.info('FCM Token refreshed: $newToken');
    final userId = FirebaseAuth.instance.currentUser?.uid;
    if (userId == null) {
      return;
    }
    await saveTokenToFirestore(userId);
  }

  /// Demande les permissions système de notification.
  Future<void> _requestPermissions() async {
    final settings = await _firebaseMessaging.requestPermission(
      alert: true,
      badge: true,
      sound: true,
    );

    LoggerService.info(
      'User granted permission: ${settings.authorizationStatus}',
    );
  }

  /// Retourne le token FCM courant de l'appareil.
  ///
  /// Sur iOS, un token APNS valide est attendu avant de récupérer le token FCM.
  Future<String?> getFCMToken() async {
    try {
      if (Platform.isIOS) {
        String? apnsToken = await _firebaseMessaging.getAPNSToken();
        int retries = 0;
        while (apnsToken == null && retries < 10) {
          LoggerService.info(
            'Waiting for APNS token... (Attempt ${retries + 1}/10)',
          );
          await Future.delayed(const Duration(seconds: 2));
          apnsToken = await _firebaseMessaging.getAPNSToken();
          retries++;
        }
        if (apnsToken == null) {
          LoggerService.error('APNS token not available after retries');
          return null;
        }
      }

      final token = await _firebaseMessaging.getToken();
      LoggerService.info('NotificationService - FCM Token: $token');
      return token;
    } catch (e) {
      LoggerService.error('Error getting FCM token: $e');
      return null;
    }
  }

  /// Sauvegarde le token FCM de l'utilisateur courant dans Firestore.
  Future<void> saveTokenToFirestore(String userId) async {
    try {
      final token = await getFCMToken();
      if (token != null) {
        await FirebaseFirestore.instance.collection('users').doc(userId).set({
          'fcmToken': token,
          'fcmTokens': FieldValue.arrayUnion([token]),
        }, SetOptions(merge: true));
        LoggerService.info('FCM Token saved to Firestore for user: $userId');
      }
    } catch (e) {
      LoggerService.error('Error saving FCM token to Firestore: $e');
    }
  }

  /// Affiche une notification locale lorsque le message arrive en foreground.
  ///
  /// Le payload FCM est conservé pour permettre le deep link au clic local.
  Future<void> _handleForegroundMessage(RemoteMessage message) async {
    LoggerService.info('Got a message whilst in the foreground!');
    LoggerService.info('Message data: ${message.data}');

    final title = message.notification?.title ?? message.data['title'];
    final body = message.notification?.body ?? message.data['body'];

    if (title == null && body == null) {
      return;
    }

    const androidDetails = AndroidNotificationDetails(
      'high_importance_channel',
      'High Importance Notifications',
      importance: Importance.max,
      priority: Priority.high,
    );
    const iosDetails = DarwinNotificationDetails();
    const details = NotificationDetails(
      android: androidDetails,
      iOS: iosDetails,
    );

    await _localNotifications.show(
      message.hashCode,
      title,
      body,
      details,
      payload: json.encode(message.data),
    );
  }
}