Rocket.Chat/app/lib/server/functions/loadMessageHistory.js

import { settings } from '../../../settings/server';
import { Messages, Rooms } from '../../../models/server';
import { normalizeMessagesForUser } from '../../../utils/server/lib/normalizeMessagesForUser';
import { getHiddenSystemMessages } from '../lib/getHiddenSystemMessages';

export const loadMessageHistory = function loadMessageHistory({ userId, rid, end, limit = 20, ls, showThreadMessages = true }) {
	const room = Rooms.findOneById(rid, { fields: { sysMes: 1 } });

	const hiddenMessageTypes = getHiddenSystemMessages(room);

	const options = {
		sort: {
			ts: -1,
		},
		limit,
	};

	if (!settings.get('Message_ShowEditedStatus')) {
		options.fields = {
			editedAt: 0,
		};
	}

	const records = end != null
		? Messages.findVisibleByRoomIdBeforeTimestampNotContainingTypes(
			rid,
			end,
			hiddenMessageTypes,
			options,
			showThreadMessages,
		).fetch()
		: Messages.findVisibleByRoomIdNotContainingTypes(
			rid,
			hiddenMessageTypes,
			options,
			showThreadMessages,
		).fetch();
	const messages = normalizeMessagesForUser(records, userId);
	let unreadNotLoaded = 0;
	let firstUnread;

	if (ls != null) {
		const firstMessage = messages[messages.length - 1];

		if ((firstMessage != null ? firstMessage.ts : undefined) > ls) {
			delete options.limit;
			const unreadMessages = Messages.findVisibleByRoomIdBetweenTimestampsNotContainingTypes(
				rid,
				ls,
				firstMessage.ts,
				hiddenMessageTypes,
				{
					limit: 1,
					sort: {
						ts: 1,
					},
				},
				showThreadMessages,
			);

			firstUnread = unreadMessages.fetch()[0];
			unreadNotLoaded = unreadMessages.count();
		}
	}

	return {
		messages,
		firstUnread,
		unreadNotLoaded,
	};
};