[Feat] 질문 수정 · 삭제 API 구현

backend/src/main/java/com/example/Piroin/project/domain/question/controller/QuestionController.java

@@ -44,10 +44,10 @@ public ResponseEntity<ApiResponse<QuestionResDTO.QuestionDetailResponse>> getQue
     public ResponseEntity<ApiResponse<QuestionResDTO.CreateRes>> createQuestion(
             @PathVariable Long sessionId,
             @RequestBody QuestionReqDTO.CreateReq request,
-            @AuthenticationPrincipal Integer userId
+            @AuthenticationPrincipal Long userId
     ) {
         return ResponseUtil.success(QuestionSuccessCode.QUESTION_CREATED,
-                questionService.createQuestion(sessionId, request, Long.valueOf(userId)));
+                questionService.createQuestion(sessionId, request, userId));
     }
 
     // 댓글/대댓글 등록
@@ -73,6 +73,29 @@ public ResponseEntity<ApiResponse<QuestionResDTO.LikeRes>> toggleLike(
                 questionService.toggleLike(questionId, userId));
     }
 
+    // 질문 수정
+    // PATCH /api/questions/{questionId}/modify
+    @PatchMapping("/api/questions/{questionId}/modify")
+    public ResponseEntity<ApiResponse<QuestionResDTO.UpdateDeleteRes>> updateQuestion(
+            @PathVariable Long questionId,
+            @RequestBody QuestionReqDTO.UpdateReq request,
+            @AuthenticationPrincipal Long userId
+    ) {
+    return ResponseUtil.success(QuestionSuccessCode.QUESTION_UPDATED,
+            questionService.updateQuestion(questionId, request, userId));
+    }
+
+    // 질문 삭제
+    // DELETE /api/questions/{questionId}
+    @DeleteMapping("/api/questions/{questionId}")
+    public ResponseEntity<ApiResponse<QuestionResDTO.UpdateDeleteRes>> deleteQuestion(
+            @PathVariable Long questionId,
+            @AuthenticationPrincipal Long userId
+    ) {
+    return ResponseUtil.success(QuestionSuccessCode.QUESTION_DELETED,
+            questionService.deleteQuestion(questionId, userId));
+    }
+
     // 이해도 체크 생성
     // POST /api/sessions/{sessionId}/understanding-checks
     @PostMapping("/api/sessions/{sessionId}/understanding-checks")

backend/src/main/java/com/example/Piroin/project/domain/question/dto/QuestionReqDTO.java

@@ -13,6 +13,13 @@ public static class CreateReq {
         private String content;
     }
 
+    // 질문 수정 요청
+    @Getter
+    @NoArgsConstructor
+    public static class UpdateReq {
+        private String content;
+    }
+
     // 댓글/대댓글 등록 요청
     // parentCommentId가 null이면 일반 댓글, 값이 있으면 대댓글
     @Getter

backend/src/main/java/com/example/Piroin/project/domain/question/dto/QuestionResDTO.java

@@ -50,6 +50,16 @@ public record LikeRes(
     ) {
     }
 
+    // 질문 수정/삭제 응답 (형태가 동일해서 하나로 공유)
+    // deletedAt에 값이 있으면 삭제된 상태
+    public record UpdateDeleteRes(
+            Long id,
+            String content,
+            LocalDateTime updatedAt,
+            LocalDateTime deletedAt
+    ) {
+    }
+
     // 질문 상세 응답
     public record QuestionDetailResponse(
             Long questionId,

backend/src/main/java/com/example/Piroin/project/domain/question/entity/Question.java

@@ -67,4 +67,16 @@ public void decreaseLikeCount() {
         }
         this.updatedAt = LocalDateTime.now();
     }
+
+    // 질문 내용 수정
+    public void updateContent(String content) {
+        this.content = content;
+        this.updatedAt = LocalDateTime.now();
+    }
+
+    // 질문 소프트 삭제 (DB에서 실제로 지우지 않고 deleted_at에 시각 기록)
+    public void softDelete() {
+        this.deletedAt = LocalDateTime.now();
+        this.updatedAt = LocalDateTime.now();
+    }
 }

backend/src/main/java/com/example/Piroin/project/domain/question/exception/code/QuestionSuccessCode.java

@@ -11,8 +11,10 @@ public enum QuestionSuccessCode implements BaseCode {
 
     QUESTION_ROOM_OK(HttpStatus.OK, "QUESTION200_1", "질문 방 조회에 성공했습니다."),
     QUESTION_DETAIL_OK(HttpStatus.OK, "QUESTION200_2", "질문 상세 조회에 성공했습니다."),
-    LIKE_TOGGLED(HttpStatus.OK, "QUESTION200_3", "좋아요가 처리되었습니다."),          // ← 추가
+    LIKE_TOGGLED(HttpStatus.OK, "QUESTION200_3", "좋아요가 처리되었습니다."),
     UNDERSTANDING_RESPONSE_OK(HttpStatus.OK, "QUESTION200_4", "이해도 응답이 반영되었습니다."),
+    QUESTION_UPDATED(HttpStatus.OK, "QUESTION200_5", "질문이 수정되었습니다."),
+    QUESTION_DELETED(HttpStatus.OK, "QUESTION200_6", "질문이 삭제되었습니다."),
     QUESTION_CREATED(HttpStatus.CREATED, "QUESTION201_1", "질문이 등록되었습니다."),
     COMMENT_CREATED(HttpStatus.CREATED, "QUESTION201_2", "댓글이 등록되었습니다."),
     UNDERSTANDING_CHECK_CREATED(HttpStatus.CREATED, "QUESTION201_3", "이해도 체크가 생성되었습니다.");

backend/src/main/java/com/example/Piroin/project/domain/question/service/QuestionService.java

@@ -237,6 +237,40 @@ public QuestionResDTO.LikeRes toggleLike(Long questionId, Long userId) {
                 });
     }
 
+    // 질문 수정
+    @Transactional
+    public QuestionResDTO.UpdateDeleteRes updateQuestion(
+            Long questionId,
+            QuestionReqDTO.UpdateReq request,
+            Long userId
+    ) {
+        User loginUser = findLoginUser(userId);
+        Question question = findQuestion(questionId);
+        validateQuestionOwner(question, loginUser);
+
+        question.updateContent(request.getContent());
+
+        return new QuestionResDTO.UpdateDeleteRes(
+                question.getId(), question.getContent(),
+                question.getUpdatedAt(), question.getDeletedAt()
+        );
+    }
+
+    // 질문 삭제
+    @Transactional
+    public QuestionResDTO.UpdateDeleteRes deleteQuestion(Long questionId, Long userId) {
+        User loginUser = findLoginUser(userId);
+        Question question = findQuestion(questionId);
+        validateQuestionOwner(question, loginUser);
+
+        question.softDelete();
+
+        return new QuestionResDTO.UpdateDeleteRes(
+                question.getId(), question.getContent(),
+                question.getUpdatedAt(), question.getDeletedAt()
+        );
+    }
+
     // 이해도 체크 생성
     @Transactional
     public QuestionResDTO.UnderstandingCheckCreateResponse createUnderstandingCheck(
@@ -320,6 +354,12 @@ private void validateCheckBelongsToSession(UnderstandingCheck check, StudySessio
         }
     }
 
+    private void validateQuestionOwner(Question question, User loginUser) {
+        if (!question.getUser().getId().equals(loginUser.getId())) {
+            throw new QuestionException(HttpStatus.FORBIDDEN, "본인의 질문만 수정/삭제할 수 있습니다.");
+        }
+    }
+
     private UnderstandResChoice applyUnderstandingResponse(
             UnderstandingCheck check, User loginUser, UnderstandResChoice requestedChoice
     ) {