getUnreadChatsCountStream method

Implementation

@override
Stream<int> getUnreadChatsCountStream() {
  // open a stream to the user's chats collection and listen to changes in
  // this collection we will also add the amount of read chats
  StreamSubscription? unreadChatSubscription;
  // ignore: close_sinks
  late StreamController<int> controller;
  controller = StreamController(
    onListen: () async {
      var currentUser = await _userService.getCurrentUser();
      var userSnapshot = _db
          .collection(_options.usersCollectionName)
          .doc(currentUser?.id)
          .collection(_options.userChatsCollectionName)
          .snapshots();

      unreadChatSubscription = userSnapshot.listen((event) {
        // every chat has a field called amount_unread_messages, combine all
        // of these fields to get the total amount of unread messages
        var unreadChats = event.docs
            .map((chat) => chat.data()['amount_unread_messages'] ?? 0)
            .toList();
        var totalUnreadChats = unreadChats.fold<int>(
          0,
          (previousValue, element) => previousValue + (element as int),
        );
        controller.add(totalUnreadChats);
      });
    },
    onCancel: () async {
      await unreadChatSubscription?.cancel();
    },
  );
  return controller.stream;
}