upstream-rocketchat/apps/meteor/server/lib/users/getUsernameSuggestion.ts

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

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

function slug(text: string): string {
	return limax(text, { replacement: '.' }).replace(/[^0-9a-z-_.]/g, '');
}

async function usernameIsAvailable(username: string): Promise<boolean> {
	if (username.length === 0) {
		return false;
	}

	if (username === 'all') {
		return false;
	}

	return !(await Users.findOneByUsernameIgnoringCase(username, {}));
}

const name = (username: string): string => (settings.get('UTF8_Names_Slugify') ? slug(username) : username);

export async function generateUsernameSuggestion(user: Pick<IUser, 'name' | 'emails' | 'services'>): Promise<string | undefined> {
	let usernames = [];

	if (user.name) {
		usernames.push(name(user.name));

		const nameParts = user.name.split(' ');

		if (nameParts.length > 1) {
			const [first] = nameParts;
			const last = nameParts[nameParts.length - 1];
			usernames.push(name(first[0] + last));
			usernames.push(name(first + last[0]));
		}
	}

	if (user?.name) {
		usernames.push(name(user.name));
	}

	if (Array.isArray(user.services)) {
		const services = [
			...new Set(user.services.flatMap(({ name, username, firstName, lastName }) => [name, username, firstName, lastName])),
		];
		usernames.push(...services.map(name));
	}

	if (user.emails && user.emails.length > 0) {
		for (const email of user.emails) {
			if (email.address && email.verified === true) {
				usernames.push(slug(email.address.replace(/@.+$/, '')));
				usernames.push(slug(email.address.replace(/(.+)@(\w+).+/, '$1.$2')));
			}
		}
	}

	usernames = usernames.filter((e) => e);

	for (const item of usernames) {
		if (await usernameIsAvailable(item)) {
			return item;
		}
	}

	usernames.push(settings.get('Accounts_DefaultUsernamePrefixSuggestion'));

	let index = await Users.countDocuments({ username: new RegExp(`^${usernames[0]}-[0-9]+`) });
	const username = '';
	while (!username) {
		if (await usernameIsAvailable(`${usernames[0]}-${index}`)) {
			return `${usernames[0]}-${index}`;
		}
		index++;
	}
}