feat: 스터디 수료 시 회비 할인 쿠폰 발급 기능 구현 (#843)

* feat: 스터디 수료 이벤트 추가

* feat: 스터디 수료 철회 이벤트 추가

* feat: 스터디 수료 관련 이벤트 발행을 위한 명시적 save 호출

* docs: 오타 수정

* feat: 스터디 단일 수료 이벤트 제거

* feat: 스터디 다건 수료 이벤트 추가

* feat: 쿠폰 이름 생성 유틸리티 구현

* test: 쿠폰 이름 생성 유틸리티 테스트 추가

* feat: 쿠폰 이벤트 핸들러 추가

* feat: 스터디 수료 쿠폰 발급 로직 구현

* docs: 투두 추가

* fix: setId 테스트 로직 추가

* refactor: void 리턴하도록 변경

Author: uwoobeat

src/main/java/com/gdschongik/gdsc/domain/coupon/application/CouponEventHandler.java

@@ -0,0 +1,23 @@
+package com.gdschongik.gdsc.domain.coupon.application;
+
+import com.gdschongik.gdsc.domain.study.domain.StudyHistoriesCompletedEvent;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.event.TransactionPhase;
+import org.springframework.transaction.event.TransactionalEventListener;
+
+@Slf4j
+@Component
+@RequiredArgsConstructor
+public class CouponEventHandler {
+    // TODO: 여기서는 쿠폰 외 도메인의 이벤트를 받아서 쿠폰 서비스를 호출. 다른 핸들러는 반대로 되어있으므로 수정 필요
+
+    private final CouponService couponService;
+
+    @TransactionalEventListener(phase = TransactionPhase.BEFORE_COMMIT)
+    public void handleStudyHistoryCompletedEvent(StudyHistoriesCompletedEvent event) {
+        log.info("[CouponEventHandler] 스터디 수료 이벤트 수신: studyHistoryIds={}", event.studyHistoryIds());
+        couponService.createAndIssueCouponByStudyHistories(event.studyHistoryIds());
+    }
+}

src/main/java/com/gdschongik/gdsc/domain/coupon/application/CouponService.java

@@ -12,8 +12,11 @@
 import com.gdschongik.gdsc.domain.coupon.dto.request.IssuedCouponQueryOption;
 import com.gdschongik.gdsc.domain.coupon.dto.response.CouponResponse;
 import com.gdschongik.gdsc.domain.coupon.dto.response.IssuedCouponResponse;
+import com.gdschongik.gdsc.domain.coupon.util.CouponNameUtil;
 import com.gdschongik.gdsc.domain.member.dao.MemberRepository;
 import com.gdschongik.gdsc.domain.member.domain.Member;
+import com.gdschongik.gdsc.domain.study.dao.StudyHistoryRepository;
+import com.gdschongik.gdsc.domain.study.domain.StudyHistory;
 import com.gdschongik.gdsc.global.exception.CustomException;
 import com.gdschongik.gdsc.global.util.MemberUtil;
 import java.util.List;
@@ -30,7 +33,9 @@
 @Transactional(readOnly = true)
 public class CouponService {
 
+    private final CouponNameUtil couponNameUtil;
     private final MemberUtil memberUtil;
+    private final StudyHistoryRepository studyHistoryRepository;
     private final CouponRepository couponRepository;
     private final IssuedCouponRepository issuedCouponRepository;
     private final MemberRepository memberRepository;
@@ -87,4 +92,28 @@ public List<IssuedCouponResponse> findMyUsableIssuedCoupons() {
                 .map(IssuedCouponResponse::from)
                 .toList();
     }
+
+    @Transactional
+    public void createAndIssueCouponByStudyHistories(List<Long> studyHistoryIds) {
+        List<StudyHistory> studyHistories = studyHistoryRepository.findAllById(studyHistoryIds);
+        List<Long> studentIds = studyHistories.stream()
+                .map(studyHistory -> studyHistory.getStudent().getId())
+                .toList();
+        List<Member> students = memberRepository.findAllById(studentIds);
+
+        String couponName = couponNameUtil.generateStudyCompletionCouponName(
+                studyHistories.get(0).getStudy());
+        // TODO: 요청할 때마다 새로운 쿠폰 생성되는 문제 수정: 스터디마다 하나의 쿠폰만 존재하도록 쿠폰 타입 및 참조 식별자 추가
+        Coupon coupon = Coupon.create(couponName, Money.from(5000L));
+        couponRepository.save(coupon);
+
+        List<IssuedCoupon> issuedCoupons = students.stream()
+                .map(student -> IssuedCoupon.create(coupon, student))
+                .toList();
+        issuedCouponRepository.saveAll(issuedCoupons);
+
+        log.info(
+                "[CouponService] 스터디 수료 쿠폰 발급: issuedCouponIds={}",
+                issuedCoupons.stream().map(IssuedCoupon::getId).toList());
+    }
 }

src/main/java/com/gdschongik/gdsc/domain/coupon/util/CouponNameUtil.java

@@ -0,0 +1,16 @@
+package com.gdschongik.gdsc.domain.coupon.util;
+
+import com.gdschongik.gdsc.domain.study.domain.Study;
+import com.gdschongik.gdsc.global.util.formatter.SemesterFormatter;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Component;
+
+@Component
+@RequiredArgsConstructor
+public class CouponNameUtil {
+
+    public String generateStudyCompletionCouponName(Study study) {
+        String academicYearAndSemesterName = SemesterFormatter.format(study);
+        return academicYearAndSemesterName + " " + study.getTitle() + " 수료 쿠폰";
+    }
+}

src/main/java/com/gdschongik/gdsc/domain/study/application/MentorStudyHistoryService.java

@@ -6,6 +6,7 @@
 import com.gdschongik.gdsc.domain.study.dao.StudyHistoryRepository;
 import com.gdschongik.gdsc.domain.study.dao.StudyRepository;
 import com.gdschongik.gdsc.domain.study.domain.Study;
+import com.gdschongik.gdsc.domain.study.domain.StudyHistoriesCompletedEvent;
 import com.gdschongik.gdsc.domain.study.domain.StudyHistory;
 import com.gdschongik.gdsc.domain.study.domain.StudyHistoryValidator;
 import com.gdschongik.gdsc.domain.study.domain.StudyValidator;
@@ -15,6 +16,7 @@
 import java.util.List;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
+import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
@@ -23,6 +25,7 @@
 @RequiredArgsConstructor
 public class MentorStudyHistoryService {
 
+    private final ApplicationEventPublisher applicationEventPublisher;
     private final MemberUtil memberUtil;
     private final StudyValidator studyValidator;
     private final StudyHistoryValidator studyHistoryValidator;
@@ -43,6 +46,9 @@ public void completeStudy(StudyCompleteRequest request) {
 
         studyHistories.forEach(StudyHistory::complete);
 
+        applicationEventPublisher.publishEvent(new StudyHistoriesCompletedEvent(
+                studyHistories.stream().map(StudyHistory::getId).toList()));
+
         log.info(
                 "[MentorStudyHistoryService] 스터디 수료 처리: studyId={}, studentIds={}",
                 request.studyId(),
@@ -63,6 +69,8 @@ public void withdrawStudyCompletion(StudyCompleteRequest request) {
 
         studyHistories.forEach(StudyHistory::withdrawCompletion);
 
+        studyHistoryRepository.saveAll(studyHistories);
+
         log.info(
                 "[MentorStudyHistoryService] 스터디 수료 철회: studyId={}, studentIds={}",
                 request.studyId(),

src/main/java/com/gdschongik/gdsc/domain/study/domain/StudyHistoriesCompletedEvent.java

@@ -0,0 +1,6 @@
+package com.gdschongik.gdsc.domain.study.domain;
+
+import java.util.List;
+import lombok.NonNull;
+
+public record StudyHistoriesCompletedEvent(@NonNull List<Long> studyHistoryIds) {}

src/main/java/com/gdschongik/gdsc/domain/study/domain/StudyHistory.java

@@ -84,6 +84,7 @@ public void complete() {
      */
     public void withdrawCompletion() {
         studyHistoryStatus = NONE;
+        registerEvent(new StudyHistoryCompletionWithdrawnEvent(this.id));
     }
 
     // 데이터 전달 로직

src/main/java/com/gdschongik/gdsc/domain/study/domain/StudyHistoryCompletionWithdrawnEvent.java

@@ -0,0 +1,6 @@
+package com.gdschongik.gdsc.domain.study.domain;
+
+public record StudyHistoryCompletionWithdrawnEvent(long studyHistoryId) {
+    // TODO: 이벤트 내부 필드의 식별자 값은 항상 not null이므로, primitive 타입으로 사용하도록 변경
+    // TODO: 스터디 철회 시 기존에 발행된 쿠폰 회수하는 로직 구현
+}

src/test/java/com/gdschongik/gdsc/domain/coupon/util/CouponNameUtilTest.java

@@ -0,0 +1,42 @@
+package com.gdschongik.gdsc.domain.coupon.util;
+
+import static com.gdschongik.gdsc.global.common.constant.RecruitmentConstant.*;
+import static com.gdschongik.gdsc.global.common.constant.StudyConstant.*;
+import static org.assertj.core.api.Assertions.*;
+
+import com.gdschongik.gdsc.domain.common.model.SemesterType;
+import com.gdschongik.gdsc.domain.common.vo.Period;
+import com.gdschongik.gdsc.domain.member.domain.Member;
+import com.gdschongik.gdsc.domain.study.domain.Study;
+import com.gdschongik.gdsc.helper.FixtureHelper;
+import org.junit.jupiter.api.Test;
+
+class CouponNameUtilTest {
+
+    CouponNameUtil couponNameUtil = new CouponNameUtil();
+    FixtureHelper fixtureHelper = new FixtureHelper();
+
+    @Test
+    void 스터디_수료_쿠폰_이름이_생성된다() {
+        // given
+        Member mentor = fixtureHelper.createMentor(1L);
+        Study study = Study.create(
+                2025,
+                SemesterType.FIRST,
+                "기초 백엔드 스터디",
+                mentor,
+                STUDY_ONGOING_PERIOD,
+                Period.of(START_DATE.minusDays(10), START_DATE.minusDays(5)),
+                TOTAL_WEEK,
+                ONLINE_STUDY,
+                DAY_OF_WEEK,
+                STUDY_START_TIME,
+                STUDY_END_TIME);
+
+        // when
+        String couponName = couponNameUtil.generateStudyCompletionCouponName(study);
+
+        // then
+        assertThat(couponName).isEqualTo("2025-1 기초 백엔드 스터디 수료 쿠폰");
+    }
+}

src/test/java/com/gdschongik/gdsc/domain/study/domain/StudyHistoryTest.java

@@ -69,6 +69,7 @@ class 스터디_수료_철회시 {
                     mentor, Period.of(now.plusDays(5), now.plusDays(10)), Period.of(now.minusDays(5), now));
 
             StudyHistory studyHistory = StudyHistory.create(student, study);
+            fixtureHelper.setId(studyHistory, 1L); // TODO: 이벤트 ID 필드를 원시 타입으로 설정하는 것 vs setId를 테스트 사용 강제 간 trade-off 고민
             studyHistory.complete();
 
             // when

src/test/java/com/gdschongik/gdsc/helper/FixtureHelper.java

@@ -8,6 +8,7 @@
 import static com.gdschongik.gdsc.global.common.constant.StudyConstant.*;
 import static com.gdschongik.gdsc.global.common.constant.TemporalConstant.*;
 
+import com.gdschongik.gdsc.domain.common.model.BaseEntity;
 import com.gdschongik.gdsc.domain.common.model.SemesterType;
 import com.gdschongik.gdsc.domain.common.vo.Money;
 import com.gdschongik.gdsc.domain.common.vo.Period;
@@ -25,6 +26,10 @@
 
 public class FixtureHelper {
 
+    public <T extends BaseEntity> void setId(T entity, Long id) {
+        ReflectionTestUtils.setField(entity, "id", id);
+    }
+
     public Member createGuestMember(Long id) {
         Member member = Member.createGuest(OAUTH_ID);
         ReflectionTestUtils.setField(member, "id", id);