Record idempotent challenge answers

docs/api-reference.md

@@ -320,10 +320,13 @@
   "questionId": "question-uuid",
   "selectedOptionId": "a",
   "timeMs": 1500,
-  "comboCount": 0
+  "comboCount": 0,
+  "submitRequestId": "client-submit-id"
 }
 ```
 
+`submitRequestId` 可选；未传时服务端会使用 `challengeId + questionId` 作为默认幂等 key。同一挑战组内重复提交同一道题会返回第一次裁决结果，不会重复扣资源或重复发放奖励。
+
 响应：
 
 ```json

docs/gamification-server-plan.md

@@ -42,7 +42,7 @@
 | # | 任务 | 状态 | 验收标准 |
 |---|------|------|----------|
 | G1-1 | 实现创建挑战组服务 | [x] | 一次返回 5 题，题目不泄露正确答案，绑定 track/node/chapter |
-| G1-2 | 实现挑战组答题提交 | [ ] | 单题提交可幂等记录，重复提交不会重复扣资源或发奖励 |
+| G1-2 | 实现挑战组答题提交 | [x] | 单题提交可幂等记录，重复提交不会重复扣资源或发奖励 |
 | G1-3 | 实现挑战组完成结算 | [ ] | 组内 5 题完成后统一计算完成奖励、全对奖励、主题节点进度和每日高奖励状态 |
 | G1-4 | 调整红心扣除边界 | [ ] | 答错扣 1 颗；Plus 用户不被红心阻断；新用户前 3 天最低保留 1 颗 |
 | G1-5 | 调整每日高奖励挑战次数 | [ ] | 免费用户每日 3 组，Plus 8 组或按产品确认无限；次数为 0 后仍可继续学习但高价值奖励降级 |

src/__tests__/services/learning/challenge-service.test.ts

@@ -1,6 +1,6 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 import { db } from '../../../db/client.js';
-import { getNextChallenge } from '../../../services/learning/challenge-service.js';
+import { getNextChallenge, submitChallengeAnswer } from '../../../services/learning/challenge-service.js';
 
 const category = {
   id: 'history',
@@ -91,4 +91,47 @@ describe('challenge-service', () => {
       }));
     });
   });
+
+  describe('submitChallengeAnswer', () => {
+    it('returns the stored result for duplicate question submissions without side effects', async () => {
+      const resultSnapshot = {
+        answerState: 'correct',
+        correctOptionId: 'a',
+        xpDelta: 10,
+        progress: {
+          hearts: 5,
+          dailyAttemptsLeft: 3,
+          xp: 120,
+          streakDays: 2,
+        },
+        knowledgeCard: {
+          id: 'card-1',
+          title: '知识点',
+          summary: '知识点',
+          fact: '解析',
+        },
+        rewards: [{ type: 'xp', amount: 10, title: '+10 XP' }],
+      };
+      vi.mocked(db.select)
+        .mockReturnValueOnce(selectChain([{
+          id: 'challenge-1',
+          userId: 'user-1',
+          status: 'pending',
+          questionIds: ['question-1'],
+        }]) as never)
+        .mockReturnValueOnce(selectChain([{
+          id: 'answer-1',
+          sessionId: 'challenge-1',
+          questionId: 'question-1',
+          submitRequestId: 'submit-1',
+          resultSnapshot,
+        }]) as never);
+
+      const result = await submitChallengeAnswer('user-1', 'challenge-1', 'question-1', 'a', 1200, 0, 'submit-1');
+
+      expect(result).toEqual(resultSnapshot);
+      expect(db.insert).not.toHaveBeenCalled();
+      expect(db.update).not.toHaveBeenCalled();
+    });
+  });
 });

src/routes/app-api.ts

@@ -25,6 +25,7 @@ const answerSchema = z.object({
   selectedOptionId: z.string().min(1),
   timeMs: z.number().min(0),
   comboCount: z.number().int().min(0).optional(),
+  submitRequestId: z.string().min(1).max(80).optional(),
 });
 
 const preferencesSchema = z.object({
@@ -82,10 +83,12 @@ export async function appApiRoutes(app: FastifyInstance): Promise<void> {
     if (!parsed.success) return validationError(parsed.error.issues[0]?.message);
     const data = await submitChallengeAnswer(
       getUserId(request),
+      parsed.data.challengeId,
       parsed.data.questionId,
       parsed.data.selectedOptionId,
       parsed.data.timeMs,
       parsed.data.comboCount,
+      parsed.data.submitRequestId,
     );
     return { success: true, data: { ...data, challengeId: parsed.data.challengeId }, error: null };
   });

src/services/learning/challenge-service.ts

@@ -1,6 +1,6 @@
 import { db } from '../../db/client.js';
-import { challengeSessions, knowledgeCards, questions, skillTree, userChapterProgress, userProgress } from '../../db/schema.js';
+import { challengeSessionAnswers, challengeSessions, knowledgeCards, questions, skillTree, userChapterProgress, userProgress } from '../../db/schema.js';
-import { and, asc, eq, notInArray, sql } from 'drizzle-orm';
+import { and, asc, eq, notInArray, or, sql } from 'drizzle-orm';
 import { v4 as uuid } from 'uuid';
 import { NotFoundError, ValidationError } from '../../utils/errors.js';
 import { addXp, BASE_XP, calculateXp } from '../progress/xp-service.js';
@@ -176,11 +176,43 @@ export async function getNextChallenge(userId: string, trackId: string): Promise
 
 export async function submitChallengeAnswer(
   userId: string,
+  challengeId: string,
   questionId: string,
   selectedOptionId: string,
   timeMs: number,
   comboCount = 0,
+  submitRequestId = `${challengeId}:${questionId}`,
 ): Promise<AnswerResultDto> {
+  const [session] = await db
+    .select()
+    .from(challengeSessions)
+    .where(and(eq(challengeSessions.id, challengeId), eq(challengeSessions.userId, userId)))
+    .limit(1);
+  if (!session) throw new NotFoundError('Challenge');
+  if (session.status === 'completed' || session.status === 'expired' || session.status === 'abandoned') {
+    throw new ValidationError('Challenge session is not accepting answers');
+  }
+
+  const sessionQuestionIds = Array.isArray(session.questionIds) ? session.questionIds : [];
+  const answerOrder = sessionQuestionIds.indexOf(questionId) + 1;
+  if (answerOrder <= 0) throw new ValidationError('Question does not belong to challenge session');
+
+  const [existingAnswer] = await db
+    .select()
+    .from(challengeSessionAnswers)
+    .where(and(
+      eq(challengeSessionAnswers.sessionId, challengeId),
+      or(
+        eq(challengeSessionAnswers.questionId, questionId),
+        eq(challengeSessionAnswers.submitRequestId, submitRequestId),
+      ),
+    ))
+    .limit(1);
+
+  if (existingAnswer?.resultSnapshot) {
+    return existingAnswer.resultSnapshot as unknown as AnswerResultDto;
+  }
+
   const [question] = await db.select().from(questions).where(eq(questions.id, questionId)).limit(1);
   if (!question) throw new NotFoundError('Question');
 
@@ -233,7 +265,7 @@ export async function submitChallengeAnswer(
     getKnowledgeCard(question),
   ]);
 
-  return {
+  const result: AnswerResultDto = {
     answerState: correct ? 'correct' : 'wrong',
     correctOptionId,
     xpDelta,
@@ -246,4 +278,29 @@ export async function submitChallengeAnswer(
     knowledgeCard,
     rewards: correct && xpDelta > 0 ? [{ type: 'xp', amount: xpDelta, title: `+${xpDelta} XP` }] : [],
   };
+
+  await db.insert(challengeSessionAnswers).values({
+    id: uuid(),
+    sessionId: challengeId,
+    userId,
+    questionId,
+    submitRequestId,
+    answerOrder,
+    answer: selectedOptionId,
+    correct: correct ? 1 : 0,
+    timeMs,
+    comboCount,
+    resultSnapshot: result as unknown as Record<string, unknown>,
+  });
+
+  await db
+    .update(challengeSessions)
+    .set({
+      status: 'in_progress',
+      answeredCount: sql`LEAST(COALESCE(answered_count, 0) + 1, COALESCE(total_questions, ${CHALLENGE_RULES.questionsPerSession}))`,
+      correctCount: correct ? sql`COALESCE(correct_count, 0) + 1` : sql`COALESCE(correct_count, 0)`,
+    })
+    .where(eq(challengeSessions.id, challengeId));
+
+  return result;
 }

src/types/app-api.ts

@@ -94,6 +94,7 @@ export interface AnswerRequestDto {
   questionId: string;
   selectedOptionId: string;
   timeMs: number;
+  submitRequestId?: string;
 }
 
 export interface AnswerResultDto {