feat(be): implement compare and management retry logic

apps/backend/apps/client/src/group/group.service.ts

@@ -13,8 +13,15 @@ import {
   QnACategory
 } from '@prisma/client'
 import { Cache } from 'cache-manager'
-import { invitationCodeKey, joinGroupCacheKey } from '@libs/cache'
-import { JOIN_GROUP_REQUEST_EXPIRE_TIME } from '@libs/constants'
+import {
+  invitationCodeKey,
+  joinGroupCacheKey,
+  studentRetryKey
+} from '@libs/cache'
+import {
+  JOIN_GROUP_REQUEST_EXPIRE_TIME,
+  STUDENT_RETRY_EXPIRE_TIME
+} from '@libs/constants'
 import {
   ConflictFoundException,
   EntityNotExistException,
@@ -504,6 +511,30 @@ export class GroupService {
     })
   }
 
+  async getUserRetryCount(userId: number, courseId: number) {
+    const count = await this.cacheManager.get<number>(
+      studentRetryKey(userId, courseId)
+    )
+    return count || 0
+  }
+
+  async canUserRetry(userId: number, courseId: number) {
+    const count = await this.getUserRetryCount(userId, courseId)
+
+    if (count >= 3) {
+      return false
+    }
+    return true
+  }
+
+  async updateRetryCount(userId: number, courseId: number, count: number) {
+    await this.cacheManager.set<number>(
+      studentRetryKey(userId, courseId),
+      count,
+      STUDENT_RETRY_EXPIRE_TIME
+    )
+  }
+
   /**
    * 사용자-그룹 관계(UserGroup)를 생성하여 실제 가입 처리를 수행합니다.
    *

apps/backend/libs/cache/src/keys.ts

@@ -9,6 +9,9 @@ export const joinGroupCacheKey = (groupId: number) => `group:${groupId}`
 export const invitationCodeKey = (code: string) => `invite:${code}`
 export const invitationGroupKey = (groupId: number) => `invite:to:${groupId}`
 
+export const studentRetryKey = (courseId: number, userId: number) =>
+  `course-retry:${userId}:${courseId}`
+
 /* TEST API용 Key */
 export const testKey = (testSubmissionId: number, testcaseId: number) =>
   `test:id:${testSubmissionId}:testcase:${testcaseId}`

apps/backend/libs/constants/src/time.constants.ts

@@ -23,6 +23,7 @@ export const PUBLICIZING_REQUEST_EXPIRE_TIME = 7 * SECONDS_PER_DAY * 1000
 export const JOIN_GROUP_REQUEST_EXPIRE_TIME = 7 * SECONDS_PER_DAY * 1000
 export const INVIATION_EXPIRE_TIME = 14 * SECONDS_PER_DAY * 1000
 export const TEST_SUBMISSION_EXPIRE_TIME = 10 * SECONDS_PER_MINUTE * 1000
+export const STUDENT_RETRY_EXPIRE_TIME = 15 * SECONDS_PER_MINUTE * 1000
 
 export const PUBLICIZING_REQUEST_KEY = 'publicize'