[Hibit] 조회수 어뷰징 방지를 위한 쿠키 기반 로그 관리

@RestController
public class PostController {

    private final PostService postService;

    public PostController(PostService postService) {
        this.postService = postService;
    }
    // ...
    
    @GetMapping("api/posts/{id}")
    @Operation(summary = "/api/posts/{id}", description = "게시글에 대한 상세 페이지를 조회한다.")
    public ResponseEntity<PostDetailResponse> findPost(@PathVariable(name = "id") Long postId) {
        PostDetailResponse response = postService.findPost(postId);
        return ResponseEntity.ok(response);
    }
}

@Component
public class ViewCountManager {
    private static final String DATE_LOG_DELIMITER = "&";
    private static final String DATE_AND_ID_DELIMITER = ":";
    private static final String ID_DELIMITER = "/";
    private static final int DATE_INDEX = 0;
    private static final int LOG_INDEX = 1;

    // <DATE>:1/2/3&
    public boolean isFirstAccess(String logs, Long postId) {
        Map<Integer, String> dateLogs = extractDateLogs(logs);
        int today = LocalDateTime.now().getDayOfMonth();
        String todayLog = dateLogs.get(today);
        if (Objects.isNull(todayLog)) {
            return true;
        }
        return isLogNonExist(todayLog, postId);
    }

    private Map<Integer, String> extractDateLogs(String logs) {
        Map<Integer, String> dateLogs = new HashMap<>();
        String[] logsPerDate = logs.split(DATE_LOG_DELIMITER);
        for (String logPerDate : logsPerDate) {
            dateLogs.putAll(divideDateAndLog(logPerDate));
        }
        return dateLogs;
    }

    private boolean isLogNonExist(String log, Long postId) {
        List<Long> loggedPostIds = Arrays.stream(log.split(ID_DELIMITER))
                .map(Long::parseLong)
                .collect(Collectors.toList());
        return !loggedPostIds.contains(postId);
    }

    private Map<Integer, String> divideDateAndLog(String logPerDate) {
        if (logPerDate.isEmpty()) {
            return Collections.emptyMap();
        }
        String[] dateAndLog = logPerDate.split(DATE_AND_ID_DELIMITER);
        int date = Integer.parseInt(dateAndLog[DATE_INDEX]);
        String log = dateAndLog[LOG_INDEX];
        return Map.of(date, log);
    }

    public String getUpdatedLog(String logs, Long postId) {
        if (!isFirstAccess(logs, postId)) {
            return logs;
        }
        Map<Integer, String> dateLogs = extractDateLogs(logs);
        int today = LocalDateTime.now().getDayOfMonth();
        String updatedLog = appendLog(dateLogs.get(today), postId);
        return today + DATE_AND_ID_DELIMITER + updatedLog;
    }

    private String appendLog(String log, Long postId) {
        if (Objects.isNull(log) || log.isEmpty()) {
            return Long.toString(postId);
        }
        return log + ID_DELIMITER + postId;
    }
}

@Service
@Transactional(readOnly = true)
public class PostService {
    private final PostRepository postRepository;
    private final ViewCountManager viewCountManager;
    
    // ...

    @Transactional
    public PostDetailResponse findPost(final Long postId, final LoginMember loginMember, final String cookieValue) {
        if (viewCountManager.isFirstAccess(cookieValue, postId)) { // 해당 게시글에 처음 방문했다면
            postRepository.updateViewCount(postId);
        }
        Post foundPost = findPostObject(postId);
        return PostDetailResponse.of(foundPost, loginMember);
    }

    public String updatePostLog(final Long postId, final String cookieValue) { // 다른 게시글ID를 포함한 로그를 쿠키에 저장
        return viewCountManager.getUpdatedLog(cookieValue, postId);
    }

    private Post findPostObject(final Long postId) {
        List<Post> posts = postRepository.findPostById(postId);
        if (posts.isEmpty()) {
            throw new NotFoundPostException();
        }
        return posts.get(0);
    }
}

@Tag(name = "posts", description = "매칭 게시글")
@RestController
public class PostController {

    private final PostService postService;

    @GetMapping("api/posts/{id}")
    @Operation(summary = "/api/posts/{id}", description = "게시글에 대한 상세 페이지를 조회한다.")
    public ResponseEntity<PostDetailResponse> findPost(@PathVariable(name = "id") final Long postId,
                                                       @AuthenticationPrincipal final LoginMember loginMember,
                                                       @CookieValue(value = "viewedPost", required = false, defaultValue = "") final String postLog) {
        PostDetailResponse response = postService.findPost(postId, loginMember, postLog);
        String updatedLog = postService.updatePostLog(postId, postLog);
        ResponseCookie responseCookie = ResponseCookie.from("viewedPost", updatedLog).maxAge(86400L).build(); // 86400L: 1일(24시간)
        return ResponseEntity.ok().header(HttpHeaders.SET_COOKIE, responseCookie.toString()).body(response);
    }
}