restore old chats

src/App.tsx

@@ -5,15 +5,56 @@ import Chat from './components/Chat';
 import Menu from './components/Menu';
 
 import useInitialiseNewChat from '@hooks/useInitialiseNewChat';
+import { ChatInterface } from '@type/chat';
+import { Theme } from '@type/theme';
 
 function App() {
   const initialiseNewChat = useInitialiseNewChat();
+  const setChats = useStore((state) => state.setChats);
+  const setTheme = useStore((state) => state.setTheme);
+  const setApiKey = useStore((state) => state.setApiKey);
+  const setCurrentChatIndex = useStore((state) => state.setCurrentChatIndex);
 
   useEffect(() => {
+    // legacy local storage
+    const oldChats = localStorage.getItem('chats');
+    const apiKey = localStorage.getItem('apiKey');
+    const theme = localStorage.getItem('theme');
+
+    if (apiKey) {
+      // legacy local storage
+      setApiKey(apiKey);
+      localStorage.removeItem('apiKey');
+    }
+
+    if (theme) {
+      // legacy local storage
+      setTheme(theme as Theme);
+      localStorage.removeItem('theme');
+    }
+
+    if (oldChats) {
+      // legacy local storage
+      try {
+        const chats: ChatInterface[] = JSON.parse(oldChats);
+        if (chats.length > 0) {
+          setChats(chats);
+          setCurrentChatIndex(0);
+        } else {
+          initialiseNewChat();
+        }
+      } catch (e: unknown) {
+        console.log(e);
+        initialiseNewChat();
+      }
+      localStorage.removeItem('chats');
+    } else {
+      // existing local storage
       const chats = useStore.getState().chats;
       if (!chats || chats.length === 0) {
         initialiseNewChat();
       }
+    }
   }, []);
 
   return (