feat: Sprint 03 댓글 도메인(생성·조회·수정·삭제) 및 하이브리드 프리뷰 아키텍처 구현

[devikae]

📌 개요 (Overview)

• PR 브랜치: feature/sprint03-comment ➔ main
• 작업 목적: Snowthing 3차 MVP 핵심 타겟인 댓글/대댓글 도메인의 생성(2-Depth 평탄화, 100개 상한), 하이브리드 프리뷰 및 분리 페이징 조회(ADR-001 채택), 수정(낙관적 락, 403 권한 분기), 삭제(Soft Delete, 4대 권한 매트릭스), 그리고 프론트엔드 UI/UX를 완비하여 main 브랜치로 통합함.

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🛠️ 주요 변경 사항 (What Changed)

1. 아키텍처 의사결정 (ADR-001) 및 하이브리드 프리뷰 조회

   • 조회 구조 채택: 3개 Spike 벤치마크(210KB vs 103KB vs 5.55KB) 실측 데이터 기반으로 [후보 3: Adjacency List 기반 하이브리드 프리뷰(루트 20개 + 대댓글 상위 5개 미리보기) 및 대댓글 20개 단위 분리 페이징] 최종 채택.
   • 대댓글 카운트 일원화: 화면 렌더링 노드 일원화 정책에 따라 삭제 대댓글 placeholder를 포함한 전체 대댓글 수(totalCount)로 replyCount, previewReplies, hasMoreReplies 기준을 100% 통일하여 UI 인지 부조화 방지.
   • 보안 및 가시성 검증: 분리 페이징 API(GET /api/v1/comments/{commentId}/replies) 진입 시 상위 게시글의 삭제/차단 상태(validatePostVisibility)를 필수 검증.

2. 댓글 생성 (Create) 및 동시성 방어

   • 2-Depth 평탄화: 대댓글 작성 시 대상 노드가 대댓글이더라도 rootParent() while loop를 통해 항상 최상위 조상 루트 엔티티를 찾아 2-Depth 계층을 보장.
   • 루트당 100개 대댓글 상한 및 비관적 락: SELECT ... FOR UPDATE로 동시 대댓글 폭증 시 상한 초과(COMMENT_005)를 물리적으로 방어.
   • 트랜잭션 분리: 회원 조회 및 BCrypt 암호화는 트랜잭션 외부에서 수행하고 짧은 DB 쓰기만 CommentCommandService 독립 Bean 트랜잭션에서 수행.
   • 익명 비밀번호 검증: @Size(min = 4, max = 20)로 입력 경계값 검증.

3. 댓글 수정 (Update) 및 동시성 제어

   • 낙관적 락(@Version): Comment 엔티티에 버전 필드를 추가해 동시 수정 시 선착순 변경만 반영하고 충돌 시 COMMENT_006 반환.
   • 인가 분기: 관리자 우회 불가, 오직 작성자 본인(일반 회원 세션 일치 / 비회원 익명 비밀번호 일치)만 수정 허용.
   • 네트워크 정보 보호: 익명 댓글만 마스킹된 IP(211.234.***.***)를 응답하고, 일반 회원은 null로 차단하여 네트워크 정보 과다 노출 방지.

4. 댓글 삭제 (Delete) 및 4대 권한 매트릭스

   • Soft Delete & 계층 보존: 물리 삭제 대신 is_deleted = true 처리 및 "삭제된 댓글입니다." placeholder로 대체 노출하여 하위 대댓글의 대화 맥락 보존.
   • 4대 권한 매트릭스:
     • 최고 관리자(ROLE_ADMIN): 비밀번호 없이 강제 삭제 허용.
     • 일반 회원 & 로그인 익명: 본인 세션 일치 시 비밀번호 없이 즉시 삭제.
     • 비회원 익명: 암호화된 비밀번호 일치 시 삭제.

5. 프론트엔드 UI/UX 완성 (page.tsx)

   • 브라우저 다이얼로그 전면 퇴출: prompt, confirm 제거 및 헤더 시각 옆 미니 ✕ 버튼과 인라인 플로팅 팝오버 위젯(CommentDeleteInline) 구현.
   • 인라인 수정 폼 (CommentEditForm): 본문 불변 수정 및 익명 비밀번호 검증.
   • Append-on-Create: 신규 댓글 등록 시 최신 댓글이 첫 페이지 재조회로 사라져 보이는 현상 개선.
   • 가짜 멘션 UI 제거: DB에 저장되지 않는 임시 라벨 대신 순수 2-Depth 토글(toggleReplyEditor)로 단순화.

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🧪 테스트 및 검증 결과 (Verification & QA)

• 백엔드 전체 단위/통합 테스트: .\gradlew.bat test 실행 결과 BUILD SUCCESSFUL (130+ 개 테스트 전수 통과, 0 failure).
• 댓글 도메인 8개 전담 테스트 클래스: 총 89개 시나리오 100% 통과 (생성, 조회, 페이징, 수정, 낙관적 락, 삭제, Soft Delete, 권한 매트릭스 등).
• 프론트엔드 프로덕션 빌드: npm run build 실행 결과 Next.js 16.2.12 Turbopack 100% SUCCESS (TypeScript 컴파일 0 error, 10개 라우트 정상 생성).
• 코드 포맷팅: .\gradlew.bat spotlessApply 서식 검증 완료.

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✅ PR 체크리스트 (Checklist)

• 코드가 정상적으로 빌드되고 모든 단위/통합 테스트가 통과하는지
• DTO 컬렉션 방어적 복사 및 불변성을 준수했는지
• 문자열 리터럴 예외 대신 ErrorCode 기반 커스텀 예외로 일원화했는지
• Controller ↔ Service ↔ Repository 간 계층 분리 원칙을 준수했는지
• docs/conception/sprint03/ 하위 모든 설계 문서(API 명세서, 정책 문서, ADR)와 구현이 100% 일치하는지
• docs/project/work.md 작업 기록지가 최신 상태로 업데이트되었는지

Summary by CodeRabbit

• New Features

  • Added cursor-based pagination for comments and replies.
  • Added reply browsing with counts, previews, and a 100-reply limit.
  • Added comment editing for authorized members and anonymous authors.
  • Improved comment details with writer information, anonymity handling, timestamps, and edit/delete permissions.
  • Added stronger validation for comment content, page sizes, and anonymous passwords.

• Bug Fixes

  • Improved handling of deleted comments, permissions, concurrent updates, and invalid requests.

• Documentation

  • Expanded setup and security guidance, including CSRF and comment behavior documentation.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 44d134f and 33562c2.

⛔ Files ignored due to path filters (26)

• docs/conception/sprint03/ADR-001-댓글아키텍처.md is excluded by !docs/**
• docs/conception/sprint03/comment_api_spec.md is excluded by !docs/**
• docs/conception/sprint03/comment_policy.md is excluded by !docs/**
• docs/conception/sprint03/spike_루트커서_대댓글전체배치.md is excluded by !docs/**
• docs/conception/sprint03/spike_메모리전체트리조립.md is excluded by !docs/**
• docs/conception/sprint03/spike_하이브리드프리뷰_분리API.md is excluded by !docs/**
• docs/conception/sprint03/기술부채 해결_4.md is excluded by !docs/**
• docs/project/work.md is excluded by !docs/**
• docs/study/sprint03/comment/test/spike_experiment_guide.md is excluded by !docs/**
• docs/study/sprint03/comment/test/spike_result_template.md is excluded by !docs/**
• docs/study/studySprint02BoardIssuesAndSolutions260821.md is excluded by !docs/**
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• docs/studyArchPrinciples260810.md is excluded by !docs/**
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• docs/study_sprint01_session_concurrency_jpa_260817.md is excluded by !docs/**
• frontend/app/components/DeleteConfirmModal.tsx is excluded by !frontend/**
• frontend/app/lib/api.ts is excluded by !frontend/**
• frontend/app/posts/[publicId]/page.tsx is excluded by !frontend/**
• frontend/tsconfig.tsbuildinfo is excluded by !frontend/**

📒 Files selected for processing (38)

• .env.example
• .github/workflows/gradle.yml
• README.md
• backend/build.gradle
• backend/src/main/java/com/ikae/snowthing/domain/comment/controller/CommentController.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/dto/CommentCreateRequest.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/dto/CommentReplyListResponse.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/dto/CommentResponse.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/dto/CommentUpdateRequest.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/dto/CommentUpdateResponse.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/dto/PostCommentListResponse.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/entity/Comment.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/repository/CommentRepository.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/repository/CommentRepositoryCustom.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/repository/CommentRepositoryImpl.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/service/CommentCommandService.java
• backend/src/main/java/com/ikae/snowthing/domain/comment/service/CommentService.java
• backend/src/main/java/com/ikae/snowthing/global/config/DataInitializer.java
• backend/src/main/java/com/ikae/snowthing/global/error/ErrorCode.java
• backend/src/main/java/com/ikae/snowthing/global/exception/GlobalExceptionHandler.java
• backend/src/main/resources/application.yml
• backend/src/test/java/com/ikae/snowthing/domain/comment/CommentReadTest.java
• backend/src/test/java/com/ikae/snowthing/domain/comment/controller/CommentControllerTest.java
• backend/src/test/java/com/ikae/snowthing/domain/comment/dto/CommentResponseTest.java
• backend/src/test/java/com/ikae/snowthing/domain/comment/entity/CommentTest.java
• backend/src/test/java/com/ikae/snowthing/domain/comment/service/CommentCreateTest.java
• backend/src/test/java/com/ikae/snowthing/domain/comment/service/CommentDeleteTest.java
• backend/src/test/java/com/ikae/snowthing/domain/comment/service/CommentServiceTest.java
• backend/src/test/java/com/ikae/snowthing/domain/comment/service/CommentUpdateTest.java
• backend/src/test/java/com/ikae/snowthing/domain/comment/spike/CommentSpikeBenchmarkHarness.java
• backend/src/test/java/com/ikae/snowthing/domain/comment/spike/CommentSpikeDataInitializer.java
• backend/src/test/java/com/ikae/snowthing/domain/comment/spike/CommentSpikeDataSeederTest.java
• backend/src/test/java/com/ikae/snowthing/domain/post/repository/PostRepositoryCustomTest.java
• backend/src/test/resources/application-test.yml
• backend/src/test/resources/application.yml
• database/ddl.sql
• database/spike_seed_comments.sql
• docker-compose.yml

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📝 Walkthrough

Walkthrough

The change migrates local, test, CI, and container databases to MySQL. It adds cursor-paginated comment reads, bounded reply previews, comment updates, permission handling, locking, reply limits, scale-test utilities, and extensive integration coverage.

Changes

Comment domain and MySQL migration

Layer / File(s)	Summary
MySQL environment and initialization .env.example, .github/workflows/*, backend/.../application*.yml, docker-compose.yml, backend/build.gradle	MySQL 8.0 replaces H2 for tests and uses environment-based credentials across local, CI, and container setups.
Comment model and write operations backend/src/main/java/.../comment/{controller,dto,entity,repository,service}/*, backend/src/main/java/.../global/*, backend/src/test/java/.../comment/{controller,dto,entity,service}/*	Comment creation, updates, deletion, validation, anonymous access, reply limits, locking, and permission metadata are implemented and tested.
Cursor-paginated comment reads backend/src/main/java/.../comment/{controller,dto,repository,service}/*, database/ddl.sql, backend/src/test/java/.../comment/CommentReadTest.java	Root comments and replies support cursor pagination, bounded previews, reply statistics, masked identities, deleted-comment handling, and continuation metadata.
Comment scale validation backend/src/test/java/.../comment/spike/*, database/spike_seed_comments.sql	Distributed and hotspot datasets, benchmark measurements, SQL plans, and Markdown reports support comment-query evaluation.
Documentation and security contracts README.md	The README documents MySQL usage, CSRF behavior, comment architecture, pagination, indexing, query comparisons, measured results, and updated section structure.

Estimated code review effort: 4 (Complex) | ~60 minutes

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/sprint03-comment

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