feat(like): 좋아요 도메인 구현 및 멱등성 처리 추가

- Like 엔티티 구현
- 좋아요 등록/취소 로직 및 중복 방지 (멱등성) 구현
- Product.likeCount 증가/감소 연동
- LikeRepository 인터페이스 정의
- Like 단위 /통 합 테스트 작성

Author: adminhelper

apps/commerce-api/src/main/java/com/loopers/application/like/LikeFacade.java

@@ -0,0 +1,34 @@
+package com.loopers.application.like;
+
+import com.loopers.domain.like.LikeService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.annotation.Transactional;
+
+/**
+ * packageName : com.loopers.application.like
+ * fileName     : LikeFacade
+ * author      : byeonsungmun
+ * date        : 2025. 11. 14.
+ * description :
+ * ===========================================
+ * DATE         AUTHOR       NOTE
+ * -------------------------------------------
+ * 2025. 11. 14.     byeonsungmun       최초 생성
+ */
+@Component
+@RequiredArgsConstructor
+@Transactional
+public class LikeFacade {
+
+    private final LikeService likeService;
+
+    public void createLike(String userId, Long productId) {
+        likeService.like(userId, productId);
+    }
+
+    public void deleteLike(String userId, Long productId) {
+        likeService.unlike(userId, productId);
+    }
+}
+

apps/commerce-api/src/main/java/com/loopers/domain/like/Like.java

@@ -0,0 +1,63 @@
+package com.loopers.domain.like;
+
+import com.loopers.support.error.CoreException;
+import com.loopers.support.error.ErrorType;
+import jakarta.persistence.*;
+import lombok.Getter;
+
+import java.time.LocalDateTime;
+
+/**
+ * packageName : com.loopers.domain.like
+ * fileName     : Like
+ * author      : byeonsungmun
+ * date        : 2025. 11. 11.
+ * description :
+ * ===========================================
+ * DATE         AUTHOR       NOTE
+ * -------------------------------------------
+ * 2025. 11. 11.     byeonsungmun       최초 생성
+ */
+@Entity
+@Table(name = "product_like")
+@Getter
+public class Like {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(name = "ref_user_id", nullable = false)
+    private String userId;
+
+    @Column(name = "ref_product_id", nullable = false)
+    private Long productId;
+
+    @Column(nullable = false)
+    private LocalDateTime createdAt;
+
+    protected Like() {}
+
+    private Like(String userId, Long productId) {
+        this.userId = requireValidUserId(userId);
+        this.productId = requireValidProductId(productId);
+        this.createdAt = LocalDateTime.now();
+    }
+
+    public static Like create(String userId, Long productId) {
+        return new Like(userId, productId);
+    }
+
+    private String requireValidUserId(String userId) {
+        if (userId == null || userId.isEmpty()) {
+            throw new CoreException(ErrorType.BAD_REQUEST, "사용자 ID는 필수입니다.");
+        }
+        return userId;
+    }
+
+    private Long requireValidProductId(Long productId) {
+        if (productId == null || productId <= 0) {
+            throw new CoreException(ErrorType.BAD_REQUEST, "상품 ID는 필수입니다.");
+        }
+        return productId;
+    }
+}

apps/commerce-api/src/main/java/com/loopers/domain/like/LikeRepository.java

@@ -0,0 +1,25 @@
+package com.loopers.domain.like;
+
+import java.util.Optional;
+
+/**
+ * packageName : com.loopers.domain.like
+ * fileName     : LikeRepository
+ * author      : byeonsungmun
+ * date        : 2025. 11. 12.
+ * description :
+ * ===========================================
+ * DATE         AUTHOR       NOTE
+ * -------------------------------------------
+ * 2025. 11. 12.     byeonsungmun       최초 생성
+ */
+public interface LikeRepository {
+
+    Optional<Like> findByUserIdAndProductId(String userId, Long productId);
+
+    void save(Like like);
+
+    void delete(Like like);
+
+    long countByProductId(Long productId);
+}

apps/commerce-api/src/main/java/com/loopers/domain/like/LikeService.java

@@ -0,0 +1,49 @@
+package com.loopers.domain.like;
+
+import com.loopers.domain.product.ProductRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.annotation.Transactional;
+
+/**
+ * packageName : com.loopers.application.like
+ * fileName     : LikeService
+ * author      : byeonsungmun
+ * date        : 2025. 11. 12.
+ * description :
+ * ===========================================
+ * DATE         AUTHOR       NOTE
+ * -------------------------------------------
+ * 2025. 11. 12.     byeonsungmun       최초 생성
+ */
+@Component
+@RequiredArgsConstructor
+public class LikeService {
+
+    private final LikeRepository likeRepository;
+    private final ProductRepository productRepository;
+
+    @Transactional
+    public void like(String userId, Long productId) {
+        if (likeRepository.findByUserIdAndProductId(userId, productId).isPresent()) return;
+
+        Like like = Like.create(userId, productId);
+        likeRepository.save(like);
+        productRepository.incrementLikeCount(productId);
+    }
+
+    @Transactional
+    public void unlike(String userId, Long productId) {
+        likeRepository.findByUserIdAndProductId(userId, productId)
+                .ifPresent(like -> {
+                    likeRepository.delete(like);
+                    productRepository.decrementLikeCount(productId);
+                });
+    }
+
+    @Transactional(readOnly = true)
+    public long countByProductId(Long productId) {
+        return likeRepository.countByProductId(productId);
+    }
+
+}

apps/commerce-api/src/main/java/com/loopers/infrastructure/like/LikeJpaRepository.java

@@ -0,0 +1,23 @@
+package com.loopers.infrastructure.like;
+
+import com.loopers.domain.like.Like;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+import java.util.Optional;
+
+/**
+ * packageName : com.loopers.infrastructure.like
+ * fileName     : LikeJpaRepository
+ * author      : byeonsungmun
+ * date        : 2025. 11. 12.
+ * description :
+ * ===========================================
+ * DATE         AUTHOR       NOTE
+ * -------------------------------------------
+ * 2025. 11. 12.     byeonsungmun       최초 생성
+ */
+public interface LikeJpaRepository extends JpaRepository<Like, Long> {
+    Optional<Like> findByUserIdAndProductId(String userId, Long productId);
+
+    long countByProductId(Long productId);
+}

apps/commerce-api/src/main/java/com/loopers/infrastructure/like/LikeRepositoryImpl.java

@@ -0,0 +1,46 @@
+package com.loopers.infrastructure.like;
+
+import com.loopers.domain.like.Like;
+import com.loopers.domain.like.LikeRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Component;
+
+import java.util.Optional;
+
+/**
+ * packageName : com.loopers.infrastructure.like
+ * fileName     : LikeRepositoryImpl
+ * author      : byeonsungmun
+ * date        : 2025. 11. 12.
+ * description :
+ * ===========================================
+ * DATE         AUTHOR       NOTE
+ * -------------------------------------------
+ * 2025. 11. 12.     byeonsungmun       최초 생성
+ */
+@Component
+@RequiredArgsConstructor
+public class LikeRepositoryImpl implements LikeRepository {
+
+    private final LikeJpaRepository likeJpaRepository;
+
+    @Override
+    public Optional<Like> findByUserIdAndProductId(String userId, Long productId) {
+        return likeJpaRepository.findByUserIdAndProductId(userId, productId);
+    }
+
+    @Override
+    public void save(Like like) {
+        likeJpaRepository.save(like);
+    }
+
+    @Override
+    public void delete(Like like) {
+        likeJpaRepository.delete(like);
+    }
+
+    @Override
+    public long countByProductId(Long productId) {
+        return likeJpaRepository.countByProductId(productId);
+    }
+}