RocketChat/Rocket.Chat

import type { IUser } from '@rocket.chat/core-typings';
import { Users } from '@rocket.chat/models';

import { executeSendMessage } from '../../app/lib/server/methods/sendMessage';
import { createDirectMessage } from '../methods/createDirectMessage';
import { SystemLogger } from './logger/system';

export async function sendDirectMessageToUsers(
    fromId = 'rocket.cat',
    toIds: string[],
    messageFn: (user: IUser) => string,
): Promise<string[]> {
    const fromUser = await Users.findOneById(fromId, { projection: { _id: 1, username: 1 } });
    if (!fromUser) {
        throw new Error(`User not found: ${fromId}`);
    }

    const users = Users.findByIds(toIds, { projection: { _id: 1, username: 1, language: 1 } });
    const success: string[] = [];

    for await (const user of users) {
        try {
            const { rid } = await createDirectMessage([user.username], fromId);
            const msg = typeof messageFn === 'function' ? messageFn(user) : messageFn;

            await executeSendMessage(fromId, { rid, msg });
            success.push(user._id);
        } catch (error) {
            SystemLogger.error(error);
        }
    }

    return success;
}