refator: 쿠폰 이벤트 처리를 위해 도메인 서비스 로직 기능 분리(할인율 계산 + 사용완료처리) -> 각각 처리하도록 분리 및 분리 확인을 위한 쿠폰 상태 추가

Author: yeonjiyeon

apps/commerce-api/src/main/java/com/loopers/application/order/OrderFacade.java

@@ -1,6 +1,5 @@
 package com.loopers.application.order;
 
-import com.loopers.domain.coupon.CouponDiscountResult;
 import com.loopers.domain.coupon.CouponService;
 import com.loopers.domain.order.Order;
 import com.loopers.domain.order.OrderCommand.Item;
@@ -9,7 +8,6 @@
 import com.loopers.domain.order.OrderService;
 import com.loopers.domain.payment.Payment;
 import com.loopers.domain.payment.PaymentProcessor;
-import com.loopers.domain.point.PointService;
 import com.loopers.domain.product.Product;
 import com.loopers.domain.product.ProductService;
 import com.loopers.domain.user.User;
@@ -31,7 +29,6 @@ public class OrderFacade {
   private final ProductService productService;
   private final UserService userService;
   private final OrderService orderService;
-  private final PointService pointService;
   private final CouponService couponService;
   private final List<PaymentProcessor> paymentProcessors;
 
@@ -54,18 +51,18 @@ public OrderInfo placeOrder(PlaceOrder command) {
     long finalPaymentAmount = totalAmount;
 
     if (command.couponId() != null) {
-      CouponDiscountResult discountResult = couponService.useCouponAndCalculateDiscount(
+      long disCountAmount = couponService.calculateDiscountAmount(
           command.couponId(),
           totalAmount
       );
 
-      finalPaymentAmount -= discountResult.discountAmount();
+      finalPaymentAmount -= disCountAmount;
     }
 
     productService.deductStock(products, orderItems);
 
     PaymentProcessor processor = paymentProcessors.stream()
-        .filter(p -> p.supports(command.paymentType())) // command에 paymentType 필드 추가 필요
+        .filter(p -> p.supports(command.paymentType()))
         .findFirst()
         .orElseThrow(() -> new CoreException(ErrorType.BAD_REQUEST, "지원하지 않는 결제 방식입니다."));
 

apps/commerce-api/src/main/java/com/loopers/domain/coupon/Coupon.java

@@ -27,6 +27,10 @@ public class Coupon extends BaseEntity {
 
   private boolean used;
 
+  @Enumerated(EnumType.STRING)
+  @Column(name = "status", nullable = false)
+  private CouponStatus status;
+
   public Coupon(long userId, CouponType type, long discountValue) {
     if (type == CouponType.PERCENTAGE && (discountValue < 0 || discountValue > 100)) {
       throw new CoreException(ErrorType.BAD_REQUEST, "할인율은 0~100% 사이여야 합니다.");
@@ -52,4 +56,24 @@ public void use() {
     this.used = true;
   }
 
+  public void reserve() {
+    if (this.status != CouponStatus.ISSUED) {
+      throw new CoreException(ErrorType.BAD_REQUEST,
+          "현재 상태(" + this.status + ")에서는 쿠폰을 예약할 수 없습니다.");
+    }
+
+    this.status = CouponStatus.RESERVED;
+  }
+
+  public void confirmUse() {
+    if (this.status != CouponStatus.RESERVED) {
+      throw new CoreException(ErrorType.BAD_REQUEST,
+          "예약 상태가 아니므로 사용을 확정할 수 없습니다: " + this.status);
+    }
+    this.status = CouponStatus.USED;
+  }
+
+  public boolean canUse() {
+    return  this.status == CouponStatus.ISSUED;
+  }
 }

apps/commerce-api/src/main/java/com/loopers/domain/coupon/CouponDiscountResult.java

@@ -2,9 +2,9 @@
 
 import com.loopers.support.error.CoreException;
 import com.loopers.support.error.ErrorType;
-import jakarta.transaction.Transactional;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Component;
+import org.springframework.transaction.annotation.Transactional;
 
 @RequiredArgsConstructor
 @Component
@@ -18,22 +18,37 @@ public Coupon getCoupon(Long id) {
         .orElseThrow(() -> new CoreException(ErrorType.NOT_FOUND, "쿠폰을 찾을 수 없습니다."));
   }
 
-  @Transactional
-  public CouponDiscountResult useCouponAndCalculateDiscount(
+  @Transactional(readOnly = true)
+  public long calculateDiscountAmount(
       Long couponId,
       long totalOrderAmount
   ) {
     Coupon coupon = couponRepository.findById(couponId)
         .orElseThrow(() -> new CoreException(ErrorType.NOT_FOUND, "쿠폰을 찾을 수 없습니다."));
 
+    if (!coupon.canUse()) {
+      throw new CoreException(ErrorType.BAD_REQUEST, "사용할 수 없는 쿠폰입니다.");
+    }
+
+    return coupon.calculateDiscountAmount(totalOrderAmount);
+  }
+
+  @Transactional
+  public void reserveCoupon(Long couponId) {
+    Coupon coupon = couponRepository.findById(couponId)
+        .orElseThrow(() -> new CoreException(ErrorType.NOT_FOUND, "쿠폰을 찾을 수 없습니다."));
+
     try {
-      coupon.use();
+      coupon.reserve();
     } catch (CoreException e) {
-      throw new CoreException(ErrorType.BAD_REQUEST, "이미 사용되었거나 사용할 수 없는 쿠폰입니다.");
+      throw new CoreException(ErrorType.BAD_REQUEST, "쿠폰 예약에 실패했습니다.");
     }
+  }
 
-    long discountAmount = coupon.calculateDiscountAmount(totalOrderAmount);
-
-    return new CouponDiscountResult(discountAmount, couponId);
+  @Transactional
+  public void confirmCouponUsage(Long couponId) {
+    Coupon coupon = couponRepository.findById(couponId)
+        .orElseThrow(() -> new CoreException(ErrorType.NOT_FOUND, "쿠폰을 찾을 수 없습니다."));
+    coupon.confirmUse();
   }
 }

apps/commerce-api/src/main/java/com/loopers/domain/coupon/CouponService.java

@@ -0,0 +1,8 @@
+package com.loopers.domain.coupon;
+
+public enum CouponStatus {
+  ISSUED,
+  RESERVED,
+  USED,
+  CANCELED
+}