Rocket.Chat/app/livechat/server/hooks/markRoomResponded.js

import { callbacks } from '../../../callbacks';
import { Rooms } from '../../../models';

callbacks.add('afterSaveMessage', function(message, room) {
	// skips this callback if the message was edited
	if (!message || message.editedAt) {
		return message;
	}

	// check if room is yet awaiting for response
	if (!(typeof room.t !== 'undefined' && room.t === 'l' && room.waitingResponse)) {
		return message;
	}

	// if the message has a token, it was sent by the visitor, so ignore it
	if (message.token) {
		return message;
	}

	Rooms.setResponseByRoomId(room._id, {
		user: {
			_id: message.u._id,
			username: message.u.username,
		},
	});

	return message;
}, callbacks.priority.LOW, 'markRoomResponded');