RocketChat/Rocket.Chat

import type { IRoom, IUser } from '@rocket.chat/core-typings';
import { Meteor } from 'meteor/meteor';

import { ChatRoom } from '../../../app/models/client';

export const getUidDirectMessage = (rid: IRoom['_id'], uid: IUser['_id'] | null = Meteor.userId()): string | undefined => {
    const room = ChatRoom.findOne({ _id: rid }, { fields: { t: 1, uids: 1 } });

    if (!room || room.t !== 'd' || !room.uids || room.uids.length > 2) {
        return undefined;
    }

    return room.uids.filter((_uid) => _uid !== uid)[0];
};