feat: paginate chat history (#903)

lib/db/queries.ts

@@ -1,7 +1,7 @@
 import 'server-only';
 
 import { genSaltSync, hashSync } from 'bcrypt-ts';
-import { and, asc, desc, eq, gt, gte, inArray } from 'drizzle-orm';
+import { and, asc, desc, eq, gt, gte, inArray, lt, SQL } from 'drizzle-orm';
 import { drizzle } from 'drizzle-orm/postgres-js';
 import postgres from 'postgres';
 
@@ -15,6 +15,7 @@ import {
   message,
   vote,
   type DBMessage,
+  Chat,
 } from './schema';
 import { ArtifactKind } from '@/components/artifact';
 
@@ -81,13 +82,68 @@ export async function deleteChatById({ id }: { id: string }) {
   }
 }
 
-export async function getChatsByUserId({ id }: { id: string }) {
+export async function getChatsByUserId({
+  id,
+  limit,
+  startingAfter,
+  endingBefore,
+}: {
+  id: string;
+  limit: number;
+  startingAfter: string | null;
+  endingBefore: string | null;
+}) {
   try {
-    return await db
-      .select()
-      .from(chat)
-      .where(eq(chat.userId, id))
-      .orderBy(desc(chat.createdAt));
+    const extendedLimit = limit + 1;
+
+    const query = (whereCondition?: SQL<any>) =>
+      db
+        .select()
+        .from(chat)
+        .where(
+          whereCondition
+            ? and(whereCondition, eq(chat.userId, id))
+            : eq(chat.userId, id),
+        )
+        .orderBy(desc(chat.createdAt))
+        .limit(extendedLimit);
+
+    let filteredChats: Array<Chat> = [];
+
+    if (startingAfter) {
+      const [selectedChat] = await db
+        .select()
+        .from(chat)
+        .where(eq(chat.id, startingAfter))
+        .limit(1);
+
+      if (!selectedChat) {
+        throw new Error(`Chat with id ${startingAfter} not found`);
+      }
+
+      filteredChats = await query(gt(chat.createdAt, selectedChat.createdAt));
+    } else if (endingBefore) {
+      const [selectedChat] = await db
+        .select()
+        .from(chat)
+        .where(eq(chat.id, endingBefore))
+        .limit(1);
+
+      if (!selectedChat) {
+        throw new Error(`Chat with id ${endingBefore} not found`);
+      }
+
+      filteredChats = await query(lt(chat.createdAt, selectedChat.createdAt));
+    } else {
+      filteredChats = await query();
+    }
+
+    const hasMore = filteredChats.length > limit;
+
+    return {
+      chats: hasMore ? filteredChats.slice(0, limit) : filteredChats,
+      hasMore,
+    };
   } catch (error) {
     console.error('Failed to get chats by user from database');
     throw error;