Adding user session for history

src/app/api/chats/route.ts

@@ -1,10 +1,47 @@
 import db from '@/lib/db';
+import { chats } from '@/lib/db/schema';
+import { eq, sql} from 'drizzle-orm';
 
 export const GET = async (req: Request) => {
   try {
-    let chats = await db.query.chats.findMany();
-    chats = chats.reverse();
-    return Response.json({ chats: chats }, { status: 200 });
+    // get header from request
+    const headers = await req.headers;
+    let userSessionId = headers.get('user-session-id')?.toString() ?? '';
+
+    if (userSessionId == '') {
+      return Response.json({ chats: {} }, { status: 200 });
+    }
+    
+    let chatsRes = await db.query.chats.findMany({
+      where: eq(chats.userSessionId, userSessionId),
+    });
+    
+    chatsRes = chatsRes.reverse();
+    // Keep only the latest 20 records in the database. Delete older records.
+    let maxRecordLimit = 20;
+    if (chatsRes.length > maxRecordLimit) {
+      const deleteChatsQuery = sql`DELETE FROM chats
+        WHERE userSessionId = ${userSessionId} AND (
+          timestamp IS NULL OR
+          timestamp NOT in (
+            SELECT timestamp FROM chats
+            WHERE userSessionId = ${userSessionId}
+            ORDER BY timestamp DESC
+            LIMIT ${maxRecordLimit}
+          )
+        )
+      `;
+      await db.run(deleteChatsQuery);
+      // Delete messages that no longer link with the chat from the database.
+      const deleteMessagesQuery = sql`DELETE FROM messages
+        WHERE chatId NOT IN (
+          SELECT id FROM chats
+        )
+      `;
+      await db.run(deleteMessagesQuery);
+    }
+
+    return Response.json({ chats: chatsRes }, { status: 200 });
   } catch (err) {
     console.error('Error in getting chats: ', err);
     return Response.json(