RocketChat/Rocket.Chat

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

import { settings } from '../../../app/settings/server';

export const findExistingCASUser = async (username: string): Promise<IUser | undefined> => {
    const casUser = await Users.findOne({ 'services.cas.external_id': username });
    if (casUser) {
        return casUser;
    }

    if (!settings.get<boolean>('CAS_trust_username')) {
        return;
    }

    // If that user was not found, check if there's any Rocket.Chat user with that username
    // With this, CAS login will continue to work if the user is renamed on both sides and also if the user is renamed only on Rocket.Chat.
    // It'll also allow non-CAS users to switch to CAS based login
    // #TODO: Remove regex based search
    const regex = new RegExp(`^${username}$`, 'i');
    const user = await Users.findOne({ username: regex });
    if (user) {
        // Update the user's external_id to reflect this new username.
        await Users.updateOne({ _id: user._id }, { $set: { 'services.cas.external_id': username } });
        return user;
    }
};