LibreChat/client/src/routes/Chat.jsx

import { 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 {
  useGetMessagesByConvoId,
  useGetConversationByIdMutation,
  useGetStartupConfig
} from '~/data-provider';

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();

  //disabled by default, we only enable it when messagesTree is null
  const messagesQuery = useGetMessagesByConvoId(conversationId, { enabled: false });
  const getConversationMutation = useGetConversationByIdMutation(conversationId);
  const { data: config } = useGetStartupConfig();

  // 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
        getConversationMutation.mutate(conversationId, {
          onSuccess: (data) => {
            setConversation(data);
          },
          onError: (error) => {
            console.error('failed to fetch the conversation');
            console.error(error);
            navigate(`/chat/new`);
            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}`);
    }
    document.title = conversation?.title || config?.appTitle || 'Chat';
  }, [conversation, conversationId, config]);

  useEffect(() => {
    if (messagesTree === null && conversation?.conversationId) {
      messagesQuery.refetch(conversation?.conversationId);
    }
  }, [conversation?.conversationId, messagesQuery, messagesTree]);

  useEffect(() => {
    if (messagesQuery.data) {
      setMessages(messagesQuery.data);
    } else if (messagesQuery.isError) {
      console.error('failed to fetch the messages');
      console.error(messagesQuery.error);
      setMessages(null);
    }
  }, [messagesQuery.data, messagesQuery.isError, setMessages]);

  // 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 />
    </>
  );
}