import 'dart:async';
import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter/services.dart';

/// 알림 타입 상수.
class PushNotificationType {
  static const String message = 'message';
  static const String clear = 'clear';
  static const String session = 'session';
  static const String tokenRefresh = 'token_refresh';
  static const String opened = 'opened';
}

/// 알림 탭 이벤트 데이터.
class NotificationOpenedEvent {
  final String? serverUrl;
  final String? channelId;
  final String? rootId;
  final bool isCRTEnabled;

  const NotificationOpenedEvent({
    this.serverUrl,
    this.channelId,
    this.rootId,
    this.isCRTEnabled = false,
  });
}

/// 푸시 알림 싱글톤 서비스.
/// mattermost-mobile의 push_notifications.ts 싱글톤 대응.
class PushNotificationService {
  static final PushNotificationService _instance =
      PushNotificationService._internal();
  factory PushNotificationService() => _instance;
  PushNotificationService._internal();

  static const EventChannel _notificationChannel =
      EventChannel('com.tokilabs.mattermost/notifications');
  static const MethodChannel _actionChannel =
      MethodChannel('com.tokilabs.mattermost/notification_actions');

  StreamSubscription? _channelSubscription;

  /// 알림 수신 스트림 (포그라운드 메시지 등 UI에서 구독)
  final StreamController<Map<String, dynamic>> _notificationController =
      StreamController<Map<String, dynamic>>.broadcast();
  Stream<Map<String, dynamic>> get onNotification =>
      _notificationController.stream;

  /// 알림 탭 스트림 (채널/스레드 네비게이션용)
  final StreamController<NotificationOpenedEvent> _openedController =
      StreamController<NotificationOpenedEvent>.broadcast();
  Stream<NotificationOpenedEvent> get onNotificationOpened =>
      _openedController.stream;

  // 네비게이션 콜백 (앱 라우터에서 등록)
  void Function(String serverUrl, String channelId)? onNavigateToChannel;
  void Function(String serverUrl, String rootId)? onNavigateToThread;

  // FCM 토큰 발급/갱신 시 서버 등록 콜백
  void Function(String deviceToken)? onDeviceTokenReady;

  // ─── 초기화 / 해제 ────────────────────────────────────────────────────

  void init() {
    _listenNativeChannel();
    _listenFcmTokenRefresh();
    _requestPermission();
  }

  void dispose() {
    _channelSubscription?.cancel();
    _notificationController.close();
    _openedController.close();
  }

  // ─── 내부 초기화 ─────────────────────────────────────────────────────

  void _listenNativeChannel() {
    _channelSubscription = _notificationChannel
        .receiveBroadcastStream()
        .listen(
          (dynamic event) {
            if (event is Map) {
              _processNotification(Map<String, dynamic>.from(event));
            }
          },
          onError: (error) => print('[PushNotification] EventChannel error: $error'),
        );
  }

  void _listenFcmTokenRefresh() {
    FirebaseMessaging.instance.onTokenRefresh.listen((token) async {
      await _saveDeviceToken(token);
    });
  }

  Future<void> _requestPermission() async {
    final settings = await FirebaseMessaging.instance.requestPermission(
      alert: true,
      badge: true,
      sound: true,
    );
    print('[PushNotification] Permission: ${settings.authorizationStatus}');

    final token = await FirebaseMessaging.instance.getToken();
    if (token != null) await _saveDeviceToken(token);
  }

  // ─── 알림 처리 ───────────────────────────────────────────────────────

  void _processNotification(Map<String, dynamic> data) {
    final type = data['type'] as String?;

    switch (type) {
      case PushNotificationType.message:
        _handleMessageNotification(data);
        break;
      case PushNotificationType.clear:
        _handleClearNotification(data);
        break;
      case PushNotificationType.session:
        _handleSessionNotification(data);
        break;
      case PushNotificationType.tokenRefresh:
        final token = data['token'] as String?;
        if (token != null) _saveDeviceToken(token);
        break;
      case PushNotificationType.opened:
        _handleNotificationOpened(data);
        break;
    }

    if (!_notificationController.isClosed) {
      _notificationController.add(data);
    }
  }

  void _handleMessageNotification(Map<String, dynamic> data) {
    final isUserInteraction = data['userInteraction'] == true;
    if (isUserInteraction) {
      _handleNotificationOpened(data);
    }
    // 포그라운드 메시지는 onNotification 스트림으로 UI에서 처리
  }

  void _handleClearNotification(Map<String, dynamic> data) {
    print('[PushNotification] Clear: channelId=${data['channel_id']}');
    // TODO: 뱃지 카운트 초기화, 로컬 알림 상태 초기화
  }

  void _handleSessionNotification(Map<String, dynamic> data) {
    print('[PushNotification] Session expired: serverUrl=${data['server_url']}');
    // TODO: 해당 서버 로그아웃 처리
    // clearAuthToken(data['server_url'])
  }

  /// 알림 탭 처리 - 채널 또는 스레드로 이동.
  /// mattermost-mobile의 openNotification() + pushNotificationEntry() 대응.
  void _handleNotificationOpened(Map<String, dynamic> data) {
    final serverUrl = data['server_url'] as String?;
    final channelId = data['channel_id'] as String?;
    final rootId = data['root_id'] as String?;
    final isCRTEnabled = data['is_crt_enabled'] == 'true';

    print('[PushNotification] Opened: channelId=$channelId rootId=$rootId');

    final event = NotificationOpenedEvent(
      serverUrl: serverUrl,
      channelId: channelId,
      rootId: rootId,
      isCRTEnabled: isCRTEnabled,
    );

    if (!_openedController.isClosed) {
      _openedController.add(event);
    }

    // 등록된 네비게이션 콜백 호출
    if (serverUrl == null) return;

    if (isCRTEnabled && rootId != null && rootId.isNotEmpty) {
      onNavigateToThread?.call(serverUrl, rootId);
    } else if (channelId != null) {
      onNavigateToChannel?.call(serverUrl, channelId);
    }
  }

  // ─── 인증 토큰 관리 ──────────────────────────────────────────────────

  /// 로그인 성공 시 호출. 서버 URL + Bearer 토큰을 네이티브에 저장.
  /// 이후 ReceiptDelivery(ACK), NotificationReplyBroadcastReceiver(답장) API 호출에 사용.
  Future<void> setAuthToken(String serverUrl, String token,
      {String? identifier}) async {
    try {
      await _actionChannel.invokeMethod('setAuthToken', {
        'serverUrl': serverUrl,
        'token': token,
        'identifier': identifier,
      });
      print('[PushNotification] Auth token saved for $serverUrl');
    } catch (e) {
      print('[PushNotification] Failed to save auth token: $e');
    }
  }

  /// 로그아웃 시 호출.
  Future<void> clearAuthToken(String serverUrl) async {
    try {
      await _actionChannel.invokeMethod('clearAuthToken', {'serverUrl': serverUrl});
    } catch (e) {
      print('[PushNotification] Failed to clear auth token: $e');
    }
  }

  /// 서버의 JWT 서명 검증용 공개키를 네이티브에 저장.
  Future<void> setSigningKey(String serverUrl, String signingKey) async {
    try {
      await _actionChannel.invokeMethod('setSigningKey', {
        'serverUrl': serverUrl,
        'signingKey': signingKey,
      });
    } catch (e) {
      print('[PushNotification] Failed to save signing key: $e');
    }
  }

  /// FCM 디바이스 토큰 저장 (네이티브 DB에 android_rn-v2:{token} 형식으로 저장).
  Future<void> _saveDeviceToken(String token) async {
    try {
      const prefix = 'android_rn';
      final formattedToken = '$prefix-v2:$token';
      await _actionChannel
          .invokeMethod('saveDeviceToken', {'token': formattedToken});
      print('[PushNotification] Device token saved');
      // 토큰 준비 완료 → 서버 등록 콜백 호출
      onDeviceTokenReady?.call(formattedToken);
    } catch (e) {
      print('[PushNotification] Failed to save device token: $e');
    }
  }

  Future<String?> getDeviceToken() async {
    try {
      return await _actionChannel.invokeMethod<String>('getDeviceToken');
    } catch (e) {
      return null;
    }
  }
}