Feat: 게시글 북마크 취소 API 구현

Author: joyewon0705

src/main/java/com/back/domain/board/post/controller/PostBookmarkController.java

@@ -7,16 +7,12 @@
 import lombok.RequiredArgsConstructor;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
-import org.springframework.web.bind.annotation.PathVariable;
-import org.springframework.web.bind.annotation.PostMapping;
-import org.springframework.web.bind.annotation.RequestMapping;
-import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.bind.annotation.*;
 
 @RestController
 @RequestMapping("/api/posts/{postId}/bookmark")
 @RequiredArgsConstructor
 public class PostBookmarkController {
-    private final PostBookmarkService bookmarkService;
     private final PostBookmarkService postBookmarkService;
 
     // 게시글 북마크
@@ -32,4 +28,18 @@ public ResponseEntity<RsData<PostBookmarkResponse>> bookmarkPost(
                         response
                 ));
     }
+
+    // 게시글 북마크 취소
+    @DeleteMapping
+    public ResponseEntity<RsData<PostBookmarkResponse>> cancelBookmarkPost(
+            @PathVariable Long postId,
+            @AuthenticationPrincipal CustomUserDetails user
+    ) {
+        PostBookmarkResponse response = postBookmarkService.cancelBookmarkPost(postId, user.getUserId());
+        return ResponseEntity
+                .ok(RsData.success(
+                        "게시글 북마크가 취소되었습니다.",
+                        response
+                ));
+    }
 }

src/main/java/com/back/domain/board/post/repository/PostBookmarkRepository.java

@@ -4,7 +4,10 @@
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.stereotype.Repository;
 
+import java.util.Optional;
+
 @Repository
 public interface PostBookmarkRepository extends JpaRepository<PostBookmark, Long> {
     boolean existsByUserIdAndPostId(Long userId, Long postId);
+    Optional<PostBookmark> findByUserIdAndPostId(Long userId, Long postId);
 }

src/main/java/com/back/domain/board/post/service/PostBookmarkService.java

@@ -50,4 +50,35 @@ public PostBookmarkResponse bookmarkPost(Long postId, Long userId) {
         postBookmarkRepository.save(new PostBookmark(post, user));
         return PostBookmarkResponse.from(post);
     }
+
+    /**
+     * 게시글 북마크 취소 서비스
+     * 1. User 조회
+     * 2. Post 조회
+     * 3. PostBookmark 조회
+     * 4. PostBookmark 삭제 및 bookmarkCount 감소
+     * 5. PostBookmarkResponse 반환
+     */
+    public PostBookmarkResponse cancelBookmarkPost(Long postId, Long userId) {
+        // User 조회
+        User user = userRepository.findById(userId)
+                .orElseThrow(() -> new CustomException(ErrorCode.USER_NOT_FOUND));
+
+        // Post 조회
+        Post post = postRepository.findById(postId)
+                .orElseThrow(() -> new CustomException(ErrorCode.POST_NOT_FOUND));
+
+        // PostBookmark 조회
+        PostBookmark postBookmark = postBookmarkRepository.findByUserIdAndPostId(userId, postId)
+                .orElseThrow(() -> new CustomException(ErrorCode.BOOKMARK_NOT_FOUND));
+
+        // PostBookmark 삭제
+        postBookmarkRepository.delete(postBookmark);
+
+        // 북마크 수 감소
+        post.decreaseBookmarkCount();
+
+        // 응답 반환
+        return PostBookmarkResponse.from(post);
+    }
 }