upstream-rocketchat/apps/meteor/client/views/root/IndexRoute.tsx

import type { RouteName } from '@rocket.chat/ui-contexts';
import { useRouter, useUser, useUserId } from '@rocket.chat/ui-contexts';
import { useEffect } from 'react';

import PageLoading from './PageLoading';

const IndexRoute = () => {
	const router = useRouter();
	const uid = useUserId();
	const user = useUser();

	useEffect(() => {
		if (!uid) {
			router.navigate('/home');
			return;
		}

		const timerId = setTimeout(() => {
			if (user?.defaultRoom) {
				const room = user.defaultRoom.split('/') as [routeName: RouteName, routeParam: string];
				router.navigate({
					name: room[0],
					params: { name: room[1] },
					search: router.getSearchParameters(),
				});
			} else {
				router.navigate('/home');
			}
		}, 0);

		return () => {
			clearTimeout(timerId);
		};
	}, [router, uid, user?.defaultRoom]);

	return <PageLoading />;
};

export default IndexRoute;