import 'dart:async';
import 'dart:io';

import 'package:firebase_messaging/firebase_messaging.dart';

typedef FcmTokenCallback = Future<void> Function(String token, String platform);

class PushService {
  PushService({required this.firebaseReady});

  final bool firebaseReady;
  final _subscriptions = <StreamSubscription<dynamic>>[];
  bool _listening = false;

  Future<void> listen({
    required void Function(String ticketId) onOpenTicket,
    required void Function(RemoteMessage message) onForegroundMessage,
    required FcmTokenCallback onToken,
    required bool Function() isSignedIn,
  }) async {
    if (!firebaseReady || _listening) {
      return;
    }
    _listening = true;
    _subscriptions
      ..add(
        FirebaseMessaging.instance.onTokenRefresh.listen((token) async {
          try {
            if (!isSignedIn()) {
              return;
            }
            final settings = await FirebaseMessaging.instance
                .getNotificationSettings();
            if (!_allowsNotifications(settings.authorizationStatus)) {
              return;
            }
            await onToken(token, _platform);
          } on Object {
            // Keep the previous registration when a token refresh cannot be saved.
          }
        }),
      )
      ..add(FirebaseMessaging.onMessage.listen(onForegroundMessage))
      ..add(
        FirebaseMessaging.onMessageOpenedApp.listen((message) {
          final ticketId = _ticketId(message);
          if (ticketId != null) {
            onOpenTicket(ticketId);
          }
        }),
      );
    try {
      final initial = await FirebaseMessaging.instance.getInitialMessage();
      if (initial != null) {
        final ticketId = _ticketId(initial);
        if (ticketId != null) {
          onOpenTicket(ticketId);
        }
      }
    } on Object {
      // Opening from a notification can wait until the next tap.
    }
  }

  Future<void> register(FcmTokenCallback onToken) async {
    if (!firebaseReady) {
      return;
    }
    try {
      final settings = await FirebaseMessaging.instance.requestPermission(
        alert: true,
        badge: true,
        sound: true,
      );
      if (!_allowsNotifications(settings.authorizationStatus)) {
        return;
      }
      final token = await FirebaseMessaging.instance.getToken();
      if (token == null || token.isEmpty) {
        return;
      }
      await onToken(token, _platform);
    } on Object {
      // Denied permission or a missing Firebase file should not block the inbox.
    }
  }

  String? _ticketId(RemoteMessage message) {
    final value = message.data['ticketId'];
    if (value is String && value.isNotEmpty) {
      return value;
    }
    return null;
  }

  bool _allowsNotifications(AuthorizationStatus status) {
    return status == AuthorizationStatus.authorized ||
        status == AuthorizationStatus.provisional;
  }

  String get _platform => Platform.isIOS ? 'ios' : 'android';
}