processCommand method Null safety

Implementation

void processCommand(Command cmd) {
  final unreadCountPayload = cmd.payload['unread_cnt'];
  if (unreadCountPayload != null) {
    final info = UnreadCountInfo.fromJson(unreadCountPayload);
    _updateSubscribedUnreadCountInfo(info);
  }

  if (cmd.requestId != null) {
    _ackTimers.remove(cmd.requestId)?.cancel();
    final completer = _completers.remove(cmd.requestId);
    // final completer2 = _completers2.remove(cmd.requestId);

    if (cmd.isError || cmd.hasError) {
      if (cmd.errorCode == ErrorCode.accessTokenNotValid) {
        sdk.eventManager.notifySessionTokenRequired();
      }
      completer?.completeError(SBError(
        code: cmd.errorCode,
        message: cmd.errorMessage,
      ));
      // completer2?.completeError(SBError(
      //   code: cmd.errorCode,
      //   message: cmd.errorMessage,
      // ));
      return;
    } else {
      completer?.complete(cmd);
      // completer2?.complete(cmd.event);
    }
  }

  final cmdString = '-- Command: ${cmd.cmd}';
  final encoder = JsonEncoder.withIndent('  ');
  final payloadString = '-- Payload: ${encoder.convert(cmd.payload)}';
  logger.i('Processing Socket event\n$cmdString\n$payloadString');

  // cmd.event?.handleEvent();
  // final handler = cmd.event?.handleEvent;
  // if (handler != null) {
  //   _queue.enqueue(AsyncSimpleTask(handler));
  // }

  Future Function(Command)? fnc;
  if (cmd.isError || cmd.hasError) {
    fnc = _processError;
  } else if (cmd.isLogin && cmd.requestId != null) {
    fnc = _processSessionRefresh;
  } else if (cmd.isLogin) {
    fnc = _processLogin;
  } else if (cmd.isSessionExpired) {
    fnc = _processSessionExpired;
  } else if (cmd.isNewMessage) {
    fnc = _processNewMessage;
  } else if (cmd.isUpdatedMessage) {
    fnc = _processUpdateMessage;
  } else if (cmd.isDeletedMessage) {
    fnc = _processDeleteMessage;
  } else if (cmd.isMemberCountChange) {
    fnc = _processMemberCountChange;
  } else if (cmd.isRead) {
    fnc = _processRead;
  } else if (cmd.isDelivery) {
    fnc = _processDelivery;
  } else if (cmd.isThread) {
    fnc = _processThread;
  } else if (cmd.isReaction) {
    fnc = _processReaction;
  } else if (cmd.isUserEvent) {
    fnc = _processUserEvent;
  } else if (cmd.isSystemEvent) {
    fnc = _processSystemEvent;
  } else if (cmd.isUpdatedPoll) {
    fnc = _processUpdatePoll;
  } else if (cmd.isVote) {
    fnc = _processVote;
  } else {/*not handle command*/}

  if (fnc != null) {
    final op = AsyncTask<Command>(func: fnc, arg: cmd);

    _queue.enqueue(op);
  }
}