[#39] 쿠폰 중복 발급 검증을 API 레이어로 이동 및 캐시-DB 2단계 조회 개선

      1. 쿠폰 발급 요청 시 컨트롤러에서 사전 중복 검증 수행
      2. isIssued → checkCouponIssueStatus 리네이밍
      3. 캐시 miss 시 DB fallback 조회 후 캐시 갱신(cache warming) 추가
      4. issueCoupon에서 중복 검증 로직 제거 (컨트롤러로 이동)

Author: SinJeongEun

coupon/src/main/java/com/commerce/coupon/bootstrap/CouponController.java

@@ -25,7 +25,16 @@ public ResponseEntity<String> issueCoupon(
             @PathVariable String couponId,
             @PathVariable String customerId
     ) {
-        couponIssueUseCase.requestIssueCoupon(CouponId.of(couponId), CustomerId.of(customerId));
+        CouponId couId = CouponId.of(couponId);
+        CustomerId cusId = CustomerId.of(customerId);
+
+        boolean issued = couponIssueUseCase.checkCouponIssueStatus(couId, cusId);
+        if(issued) {
+            return ResponseEntity.ok("이미 발급된 쿠폰입니다.");
+        }
+
+        // 미발행된 경우에만 이벤트 발행
+        couponIssueUseCase.requestIssueCoupon(couId, cusId);
         return ResponseEntity.ok("발급 요청 완료");
     }
 
@@ -44,7 +53,7 @@ public ResponseEntity<String> checkIssued(
             @PathVariable String couponId,
             @PathVariable String customerId
     ) {
-        boolean isIssued = couponIssueUseCase.isIssued(
+        boolean isIssued = couponIssueUseCase.checkCouponIssueStatus(
                 CouponId.of(couponId),
                 CustomerId.of(customerId)
         );

coupon/src/main/java/com/commerce/coupon/core/application/port/in/CouponIssueUseCase.java

@@ -10,5 +10,5 @@ public interface CouponIssueUseCase {
     List<CouponView> getMyCoupons(CustomerId customerId);
     void issueCoupon(CouponId couponId, CustomerId customerId);
     void requestIssueCoupon(CouponId couponId, CustomerId customerId);
-    boolean isIssued(CouponId of, CustomerId of1);
+    boolean checkCouponIssueStatus(CouponId couponId, CustomerId customerId);
 }

coupon/src/main/java/com/commerce/coupon/core/application/port/in/CouponIssueUseCaseImpl.java

@@ -21,10 +21,10 @@
 import java.time.LocalDate;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 
-import static com.commerce.shared.exception.BusinessError.DUPLICATE_ISSUED_COUPON;
 import static com.commerce.shared.exception.BusinessError.INVALID_COUPON;
 import static com.commerce.shared.kafka.event.topic.EventTopic.COUPON_ISSUE_TOPIC;
 
@@ -68,16 +68,10 @@ public List<CouponView> getMyCoupons(CustomerId customerId) {
 
     @Override
     public void issueCoupon(CouponId couponId, CustomerId customerId) {
-        // 캐싱데이터 조회
-        if(isIssued(couponId, customerId)) return;
-
-        // db에서 발행여부 조회
-        CouponIssueId couponIssueId = new CouponIssueId(couponId, customerId);
-        couponIssueOutPort.findByCouponIssueId(couponIssueId)
-                .ifPresent(exist -> {
-                    throw new BusinessException(DUPLICATE_ISSUED_COUPON);
-                });
-
+        // todo 큐이기 때문에 중복 요청이 올 수 있다. redis 검증로직이 필요하다.
+        // todo 발행실패인 경우, 멱등성있게 처리하는 방법이 필요하다.
+        // todo 테스트코드 수정
+        
         // 발행
         Coupon coupon = couponOutPort.findById(couponId)
                 .orElseThrow(() -> new BusinessException(INVALID_COUPON));
@@ -97,7 +91,22 @@ public void requestIssueCoupon(CouponId couponId, CustomerId customerId) {
     }
 
     @Override
-    public boolean isIssued(CouponId couponId, CustomerId customerId) {
-        return couponIssueCache.isIssued(couponId, customerId);
+    public boolean checkCouponIssueStatus(CouponId couponId, CustomerId customerId) {
+        // 쿠폰발행 캐싱 확인
+        AtomicBoolean issued = new AtomicBoolean(couponIssueCache.isIssued(couponId, customerId));
+
+        if(issued.get()){
+            return true;
+        }
+
+        // cache miss or 미발행
+        CouponIssueId couponIssueId = new CouponIssueId(couponId, customerId);
+        couponIssueOutPort.findByCouponIssueId(couponIssueId)
+                .ifPresent(exist -> {
+                    couponIssueCache.save(couponId, customerId);
+                    issued.set(true);
+                });
+
+        return issued.get();
     }
 }