Bug/fix qa (#332)

* fix(qa): prevent duplicate questions and improve cache invalidation

* fix(qa): keep pagination totals consistent after deduplication

* fix(qa): paginate by unique questions and bump cache namespace

Author: ViktorSvertoka

frontend/app/api/questions/[category]/route.ts

@@ -1,4 +1,4 @@
-import { and, eq, ilike, sql } from 'drizzle-orm';
+import { and, eq, ilike } from 'drizzle-orm';
 import { NextResponse } from 'next/server';
 
 import { db } from '@/db';
@@ -139,19 +139,7 @@ export async function GET(
       ? and(baseCondition, ilike(questionTranslations.question, `%${search}%`))
       : baseCondition;
 
-    const [{ count }] = await db
-      .select({ count: sql<number>`count(*)` })
-      .from(questions)
-      .innerJoin(
-        questionTranslations,
-        eq(questions.id, questionTranslations.questionId)
-      )
-      .where(whereCondition);
-
-    const total = Number(count);
-    const totalPages = Math.ceil(total / limit);
-
-    const items = await db
+    const allItems = await db
       .select({
         id: questions.id,
         categoryId: questions.categoryId,
@@ -167,20 +155,20 @@ export async function GET(
         eq(questions.id, questionTranslations.questionId)
       )
       .where(whereCondition)
-      .orderBy(questions.sortOrder)
-      .limit(limit)
-      .offset(offset);
+      .orderBy(questions.sortOrder, questions.id);
 
-    const payload = normalizeResponse(
-      {
+    const uniqueItems = dedupeItems(allItems);
+    const total = uniqueItems.length;
+    const totalPages = Math.ceil(total / limit);
+    const items = uniqueItems.slice(offset, offset + limit);
+
+    const payload = {
       items,
       total,
       page,
       totalPages,
       locale,
-      },
-      limit
-    );
+    } satisfies QaApiResponse;
     const response = NextResponse.json(payload);
     response.headers.set('Cache-Control', 'no-store');
     response.headers.set('x-qa-cache', 'MISS');

frontend/lib/cache/qa.ts

@@ -1,6 +1,6 @@
 import { getRedisClient } from '@/lib/redis';
 
-const QA_CACHE_VERSION = 'v2';
+const QA_CACHE_VERSION = 'v3';
 const QA_CACHE_TTL_SECONDS = 60 * 30;
 
 type QaCacheKeyInput = {

frontend/lib/tests/q&a/questions-route.test.ts

@@ -68,9 +68,8 @@ describe('GET /api/questions/[category]', () => {
     const selectMock = db.select as ReturnType<typeof vi.fn>;
     selectMock
       .mockReturnValueOnce(makeBuilder('limit', [{ id: 'cat-1' }]))
-      .mockReturnValueOnce(makeBuilder('where', [{ count: 2 }]))
       .mockReturnValueOnce(
-        makeBuilder('offset', [
+        makeBuilder('orderBy', [
           {
             id: 'q1',
             categoryId: 'cat-1',
@@ -80,6 +79,15 @@ describe('GET /api/questions/[category]', () => {
             answerBlocks: [],
             locale: 'en',
           },
+          {
+            id: 'q2',
+            categoryId: 'cat-1',
+            sortOrder: 2,
+            difficulty: null,
+            question: 'Question 2',
+            answerBlocks: [],
+            locale: 'en',
+          },
         ])
       );
 
@@ -93,7 +101,7 @@ describe('GET /api/questions/[category]', () => {
     const data = await res.json();
 
     expect(res.status).toBe(200);
-    expect(data.items).toHaveLength(1);
+    expect(data.items).toHaveLength(2);
     expect(data.items[0].question).toBe('Question 1');
     expect(data.total).toBe(2);
     expect(data.totalPages).toBe(1);
@@ -127,9 +135,8 @@ describe('GET /api/questions/[category]', () => {
 
     selectMock
       .mockReturnValueOnce(makeBuilder('limit', [{ id: 'cat-1' }]))
-      .mockReturnValueOnce(makeBuilder('where', [{ count: 3 }]))
       .mockReturnValueOnce(
-        makeBuilder('offset', [
+        makeBuilder('orderBy', [
           {
             id: 'q1',
             categoryId: 'cat-1',