LibreChat/client/src/routes/Chat.jsx

import React, { useEffect } from 'react';
import { useNavigate, useParams } from 'react-router-dom';
import { useRecoilState, useRecoilValue, useSetRecoilState } from 'recoil';

import Landing from '../components/ui/Landing';
import Messages from '../components/Messages';
import TextChat from '../components/Input';

import store from '~/store';
import manualSWR from '~/utils/fetchers';

export default function Chat() {
  const searchQuery = useRecoilValue(store.searchQuery);
  const [conversation, setConversation] = useRecoilState(store.conversation);
  const setMessages = useSetRecoilState(store.messages);
  const messagesTree = useRecoilValue(store.messagesTree);
  const { newConversation } = store.useConversation();
  const { conversationId } = useParams();
  const navigate = useNavigate();

  const { trigger: messagesTrigger } = manualSWR(`/api/messages/${conversation?.conversationId}`, 'get');

  const { trigger: conversationTrigger } = manualSWR(`/api/convos/${conversationId}`, 'get');

  // when conversation changed or conversationId (in url) changed
  useEffect(() => {
    if (conversation === null) {
      // no current conversation, we need to do something
      if (conversationId === 'new') {
        // create new
        newConversation();
      } else if (conversationId) {
        // fetch it from server
        conversationTrigger()
          .then(setConversation)
          .catch(error => {
            console.error('failed to fetch the conversation');
            console.error(error);
            newConversation();
          });
        setMessages(null);
      } else {
        navigate(`/chat/new`);
      }
    } else if (conversation?.conversationId === 'search') {
      // jump to search page
      navigate(`/search/${searchQuery}`);
    } else if (conversation?.conversationId !== conversationId) {
      // conversationId (in url) should always follow conversation?.conversationId, unless conversation is null
      navigate(`/chat/${conversation?.conversationId}`);
    }
  }, [conversation, conversationId]);

  // when messagesTree is null (<=> messages is null)
  // we need to fetch message list from server
  useEffect(() => {
    if (messagesTree === null) {
      messagesTrigger().then(setMessages);
    }
  }, [conversation?.conversationId]);

  // if not a conversation
  if (conversation?.conversationId === 'search') return null;
  // if conversationId not match
  if (conversation?.conversationId !== conversationId) return null;
  // if conversationId is null
  if (!conversationId) return null;

  return (
    <>
      {conversationId === 'new' && !!messagesTree?.length ? <Landing /> : <Messages />}
      <TextChat />
    </>
  );
}