@Builder 패턴

// @Builder가 BoardDto에 자동으로 만들어주는 것 (직접 쓸 필요 없음, 이해용)
public static BoardDtoBuilder builder() {
    return new BoardDtoBuilder();
}

public static class BoardDtoBuilder {
    private Long id;
    private String title;
    private String content;
    // ... 모든 필드

    public BoardDtoBuilder id(Long id) { this.id = id; return this; }
    public BoardDtoBuilder title(String title) { this.title = title; return this; }
    public BoardDtoBuilder content(String content) { this.content = content; return this; }
    // ... 각 필드마다 메서드 하나씩 (return this → 체이닝 가능)

    public BoardDto build() {
        return new BoardDto(this.id, this.title, this.content, ...);
        // ← .build() 호출 시점에 비로소 BoardDto 객체 생성
    }
}

package com.example.board.dto;

import lombok.*;

@Getter
@Setter             // @RequestBody 수신용으로 유지
@Builder            // Builder 패턴 활성화
@NoArgsConstructor  // 기본 생성자 (Jackson, JPA용)
@AllArgsConstructor // 전체 필드 생성자 (@Builder 요구사항)
public class BoardDto {
    private Long id;
    private String title;
    private String content;
    private String nickname;
    private String username;
    private int viewCount;
    private String createdAt;
    private Long userId;
}

package com.example.board.dto;

import lombok.*;

@Getter
@Setter             // @RequestBody 수신용으로 유지
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class UserDto {
    private Long id;
    private String username;
    private String password;
    private String nickname;
    private String role;
    private String adminCode;
}

// ─── 변경 전 (Setter 방식) ───────────────────────────────────────
private BoardDto toDto(Board board) {
    BoardDto dto = new BoardDto();
    dto.setId(board.getId());
    dto.setTitle(board.getTitle());
    dto.setContent(board.getContent());
    dto.setViewCount(board.getViewCount());
    dto.setNickname(board.getUser().getNickname());
    dto.setUsername(board.getUser().getUsername());
    dto.setUserId(board.getUser().getId());
    dto.setCreatedAt(board.getCreatedAt()
        .format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm")));
    return dto;
}

// ─── 변경 후 (Builder 방식) ──────────────────────────────────────
private BoardDto toDto(Board board) {
    return BoardDto.builder()
        .id(board.getId())
        .title(board.getTitle())
        .content(board.getContent())
        .viewCount(board.getViewCount())
        .nickname(board.getUser().getNickname())
        .username(board.getUser().getUsername())
        .userId(board.getUser().getId())
        .createdAt(board.getCreatedAt()
            .format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm")))
        .build();
}

@Transactional(readOnly = true)
public List<UserDto> getAllUsers() {
    return userRepository.findAll().stream()
        .map(user -> UserDto.builder()   // ← Builder 방식
            .id(user.getId())
            .username(user.getUsername())
            .nickname(user.getNickname())
            .role(user.getRole())
            .build()
        )
        .collect(Collectors.toList());
}

@Transactional(readOnly = true)
public List<BoardDto> getAllBoards() {
    return boardRepository.findAll().stream()
        .map(board -> BoardDto.builder()   // ← Builder 방식
            .id(board.getId())
            .title(board.getTitle())
            .nickname(board.getUser().getNickname())
            .viewCount(board.getViewCount())
            .build()
        )
        .collect(Collectors.toList());
}

// deleteUser(), deleteBoard() 는 변경 없음

@Service @RequiredArgsConstructor
public class BoardService {
    private final BoardRepository boardRepository;

    @Transactional(readOnly = true)
    public Page<BoardDto> getBoardList(int page) {
        Pageable pageable = PageRequest.of(page, 10, Sort.by("createdAt").descending());
        Page<Board> boardPage = boardRepository.findAllByOrderByCreatedAtDesc(pageable);
        List<BoardDto> dtoList = boardPage.getContent().stream()
            .map(this::toDto).collect(Collectors.toList());
        return new PageImpl<>(dtoList, pageable, boardPage.getTotalElements());
    }

    @Transactional
    public BoardDto getDetail(Long id, User loginUser) {
        Board board = boardRepository.findById(id)
            .orElseThrow(() -> new CustomException("없는 게시글입니다.", 404));
        if (loginUser == null || !board.getUser().getId().equals(loginUser.getId()))
            board.setViewCount(board.getViewCount() + 1);
        return toDto(board);
    }

    @Transactional
    public void write(BoardDto boardDto, User user) {
        Board board = new Board();
        board.setTitle(boardDto.getTitle());
        board.setContent(boardDto.getContent());
        board.setUser(user);
        boardRepository.save(board);
    }

    @Transactional
    public void update(Long id, BoardDto boardDto, User user) {
        Board board = boardRepository.findById(id)
            .orElseThrow(() -> new CustomException("없는 게시글입니다.", 404));
        if (!board.getUser().getId().equals(user.getId()))
            throw new CustomException("수정 권한이 없습니다.", 403);
        board.setTitle(boardDto.getTitle());
        board.setContent(boardDto.getContent());
    }

    @Transactional
    public void delete(Long id, User user) {
        Board board = boardRepository.findById(id)
            .orElseThrow(() -> new CustomException("없는 게시글입니다.", 404));
        if (!board.getUser().getId().equals(user.getId()))
            throw new CustomException("삭제 권한이 없습니다.", 403);
        boardRepository.delete(board);
    }

    // STEP 5 — Builder 방식 toDto()
    private BoardDto toDto(Board board) {
        return BoardDto.builder()
            .id(board.getId())
            .title(board.getTitle())
            .content(board.getContent())
            .viewCount(board.getViewCount())
            .nickname(board.getUser().getNickname())
            .username(board.getUser().getUsername())
            .userId(board.getUser().getId())
            .createdAt(board.getCreatedAt()
                .format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm")))
            .build();
    }
}

@Service @RequiredArgsConstructor
public class AdminService {
    private final UserRepository userRepository;
    private final BoardRepository boardRepository;

    @Transactional(readOnly = true)
    public List<UserDto> getAllUsers() {
        return userRepository.findAll().stream()
            .map(user -> UserDto.builder()
                .id(user.getId())
                .username(user.getUsername())
                .nickname(user.getNickname())
                .role(user.getRole())
                .build()
            )
            .collect(Collectors.toList());
    }

    @Transactional(readOnly = true)
    public List<BoardDto> getAllBoards() {
        return boardRepository.findAll().stream()
            .map(board -> BoardDto.builder()
                .id(board.getId())
                .title(board.getTitle())
                .nickname(board.getUser().getNickname())
                .viewCount(board.getViewCount())
                .build()
            )
            .collect(Collectors.toList());
    }

    @Transactional
    public void deleteUser(Long userId) {
        User user = userRepository.findById(userId)
            .orElseThrow(() -> new CustomException("없는 유저입니다.", 404));
        boardRepository.deleteByUser(user);
        userRepository.delete(user);
    }

    @Transactional
    public void deleteBoard(Long boardId) {
        Board board = boardRepository.findById(boardId)
            .orElseThrow(() -> new CustomException("없는 게시글입니다.", 404));
        boardRepository.delete(board);
    }
}