feat: 사진 다운로드 로직 구현 및 CDN 설정

src/main/java/com/cheeeese/album/application/validator/AlbumValidator.java

@@ -7,11 +7,15 @@
 import com.cheeeese.album.exception.code.AlbumErrorCode;
 import com.cheeeese.album.infrastructure.persistence.AlbumRepository;
 import com.cheeeese.album.infrastructure.persistence.UserAlbumRepository;
+import com.cheeeese.photo.domain.Photo;
+import com.cheeeese.photo.exception.PhotoException;
+import com.cheeeese.photo.exception.code.PhotoErrorCode;
 import com.cheeeese.user.domain.User;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Component;
 
 import java.time.LocalDate;
+import java.util.List;
 
 @Component
 @RequiredArgsConstructor
@@ -69,6 +73,20 @@ public void validateAlbumCapacity(Album album) {
     }
 
     public void validateUploadPermission(Album album, User user) { // [NEW]
+        validateAlbumParticipant(album, user);
+    }
+
+    public void validateDownloadPermission(Album album, User user, List<Photo> photos) {
+        validateAlbumParticipant(album, user);
+
+        boolean existsPhotoInAlbum = photos.stream().allMatch(photo -> photo.getAlbum().getId().equals(album.getId()));
+
+        if (!existsPhotoInAlbum) {
+            throw new PhotoException(PhotoErrorCode.PHOTO_NOT_FOUND_IN_ALBUM);
+        }
+    }
+
+    private void validateAlbumParticipant(Album album, User user) {
         validateAlbumExpiration(album);
 
         validateUserBlacklisted(album, user);

src/main/java/com/cheeeese/global/domain/BaseEntity.java

@@ -22,4 +22,8 @@ public abstract class BaseEntity {
     @LastModifiedDate
     @Column(name = "updated_at")
     private LocalDateTime updatedAt;
+
+    protected void markUpdated() {
+        this.updatedAt = LocalDateTime.now();
+    }
 }

src/main/java/com/cheeeese/global/util/S3Util.java

@@ -0,0 +1,46 @@
+package com.cheeeese.global.util;
+
+import java.net.URI;
+import java.net.URISyntaxException;
+
+public class S3Util {
+
+    public static String extractObjectKey(String imageUrl) {
+        if (imageUrl == null) {
+            throw new NullPointerException("image url is null");
+        }
+
+        try {
+            URI uri = new URI(imageUrl);
+            String path = uri.getPath();
+            if (path != null && !path.isBlank()) {
+                return path.startsWith("/") ? path.substring(1) : path;
+            }
+        } catch (URISyntaxException e) {
+
+        }
+        if (imageUrl.startsWith("album/")) {
+            return imageUrl;
+        }
+        return imageUrl;
+    }
+
+    public static String extractFileName(String imageUrl) {
+        if (imageUrl == null || imageUrl.isBlank()) {
+            return "unnamed.jpg";
+        }
+        String normalized = imageUrl.replace('\\', '/');
+
+        int lastSlashIdx = normalized.lastIndexOf('/');
+        String fileName = (lastSlashIdx >= 0)
+                ? normalized.substring(lastSlashIdx + 1)
+                : normalized;
+
+        int underscoreIdx = fileName.indexOf('_');
+        if (underscoreIdx >= 0 && underscoreIdx < fileName.length() - 1) {
+            fileName = fileName.substring(underscoreIdx + 1);
+        }
+
+        return fileName;
+    }
+}

src/main/java/com/cheeeese/global/util/resolver/CdnUrlResolver.java

@@ -0,0 +1,36 @@
+package com.cheeeese.global.util.resolver;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Component;
+
+@Component
+public class CdnUrlResolver {
+
+    @Value("${cdn.original-domain}")
+    private String originalDomain;
+
+    @Value("${cdn.thumbnail-domain}")
+    private String thumbnailDomain;
+
+    @Value("${cdn.4cut-domain}")
+    private String cutDomain;
+
+    public String resolveOriginal(String path) {
+        return resolve(originalDomain, path);
+    }
+
+    public String resolveThumbnail(String path) {
+        return resolve(thumbnailDomain, path);
+    }
+
+    public String resolveCut(String path) {
+        return resolve(cutDomain, path);
+    }
+
+    private String resolve(String domain, String path) {
+        if (path == null || path.isBlank()) return null;
+        if (path.startsWith("http")) return path;
+        if (path.startsWith("/")) path = path.substring(1);
+        return domain + "/" + path;
+    }
+}

src/main/java/com/cheeeese/photo/application/PhotoQueryService.java

@@ -2,6 +2,7 @@
 
 import com.cheeeese.album.domain.type.AlbumSorting;
 import com.cheeeese.global.util.RedisCacheUtil;
+import com.cheeeese.global.util.resolver.CdnUrlResolver;
 import com.cheeeese.photo.domain.Photo;
 import com.cheeeese.photo.dto.response.*;
 import com.cheeeese.photo.exception.PhotoException;
@@ -32,6 +33,7 @@ public class PhotoQueryService {
     private final PhotoLikesRepository photoLikesRepository;
     private final PhotoHistoryRepository photoHistoryRepository;
     private final RedisCacheUtil redisCacheUtil;
+    private final CdnUrlResolver cdnUrlResolver;
 
     private static final String PHOTO_KEY = "album:%s:photos:page:%d:version:%d";
     private static final String VERSION_KEY = "album:%s:version";
@@ -94,19 +96,22 @@ public PhotoDetailResponse getPhotoDetail(User user, String code, Long photoId)
         Photo photo = photoRepository.findByIdAndAlbum_Code(photoId, code)
                 .orElseThrow(() -> new PhotoException(PhotoErrorCode.PHOTO_NOT_FOUND));
 
+        String resolveOriginalUrl = cdnUrlResolver.resolveOriginal(photo.getImageUrl());
+        String resolveThumbnailUrl = cdnUrlResolver.resolveThumbnail(photo.getThumbnailUrl());
+
         boolean isLiked = photoLikesRepository.existsByUserIdAndPhotoId(user.getId(), photo.getId());
         boolean isDownloaded = photoHistoryRepository.existsByUserIdAndPhotoId(user.getId(), photo.getId());
         boolean isRecentlyDownloaded = photoHistoryRepository.existsByUserIdAndPhotoIdAndCreatedAtAfter(
                 user.getId(), photo.getId(), LocalDateTime.now().minusHours(1)
         );
 
-        return PhotoMapper.toPhotoDetailResponse(photo, isLiked, isDownloaded, isRecentlyDownloaded);
+        return PhotoMapper.toPhotoDetailResponse(photo, resolveOriginalUrl, resolveThumbnailUrl, isLiked, isDownloaded, isRecentlyDownloaded);
     }
 
     private PhotoPageResponse getPhotoPageFromDB(String code, int page, int size, AlbumSorting albumSorting) {
         PageRequest pageRequest = PageRequest.of(page, size, getPhotoSortingOption(albumSorting));
         Slice<Photo> photos = photoRepository.findAllByAlbumCode(code, pageRequest);
-        return PhotoMapper.toPhotoPageResponse(photos);
+        return PhotoMapper.toPhotoPageResponse(photos, cdnUrlResolver);
     }
 
     private PhotoPageResponse attachUserStatus(User user, PhotoPageResponse response) {
@@ -162,9 +167,10 @@ private List<PhotoLikedResponse> buildPhotoLikedResponses(List<Photo> photos, Se
         return photos.stream()
                 .map(photo -> {
                     Long id = photo.getId();
+                    String resolvedThumbnailUrl = cdnUrlResolver.resolveThumbnail(photo.getThumbnailUrl());
                     boolean isDownloaded = downloaded.contains(id);
                     boolean isRecentlyDownloaded = recent.contains(id);
-                    return PhotoMapper.toPhotoLikedResponse(photo, isDownloaded, isRecentlyDownloaded);
+                    return PhotoMapper.toPhotoLikedResponse(photo, resolvedThumbnailUrl, isDownloaded, isRecentlyDownloaded);
                 })
                 .toList();
     }

src/main/java/com/cheeeese/photo/application/PhotoService.java

@@ -3,17 +3,23 @@
 import com.cheeeese.album.application.validator.AlbumValidator;
 import com.cheeeese.album.domain.Album;
 import com.cheeeese.album.infrastructure.persistence.AlbumRepository;
+import com.cheeeese.global.util.S3Util;
 import com.cheeeese.photo.application.validator.PhotoValidator;
 import com.cheeeese.photo.domain.Photo;
+import com.cheeeese.photo.domain.PhotoHistory;
 import com.cheeeese.photo.domain.PhotoLikes;
 import com.cheeeese.photo.domain.PhotoStatus;
+import com.cheeeese.photo.dto.request.PhotoDownloadRequest;
 import com.cheeeese.photo.dto.request.PhotoPresignedUrlRequest;
 import com.cheeeese.photo.dto.request.PhotoUploadReportRequest;
+import com.cheeeese.photo.dto.response.PhotoDownloadResponse;
 import com.cheeeese.photo.dto.response.PhotoPresignedUrlResponse;
 import com.cheeeese.photo.exception.PhotoException;
 import com.cheeeese.photo.exception.code.PhotoErrorCode;
+import com.cheeeese.photo.infrastructure.mapper.PhotoHistoryMapper;
 import com.cheeeese.photo.infrastructure.mapper.PhotoLikesMapper;
 import com.cheeeese.photo.infrastructure.mapper.PhotoMapper;
+import com.cheeeese.photo.infrastructure.persistence.PhotoHistoryRepository;
 import com.cheeeese.photo.infrastructure.persistence.PhotoLikesRepository;
 import com.cheeeese.photo.infrastructure.persistence.PhotoRepository;
 import com.cheeeese.user.application.UserService;
@@ -24,7 +30,9 @@
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.time.LocalDateTime;
 import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 @Service
@@ -35,6 +43,7 @@ public class PhotoService {
     private final UserService userService;
     private final PhotoRepository photoRepository;
     private final PhotoLikesRepository photoLikesRepository;
+    private final PhotoHistoryRepository photoHistoryRepository;
     private final PhotoValidator photoValidator;
     private final AlbumValidator albumValidator;
     private final AlbumRepository albumRepository;
@@ -75,6 +84,36 @@ public PhotoPresignedUrlResponse createPresignedUrls(User user, PhotoPresignedUr
         return PhotoMapper.toPresignedUrlResponse(presignedUrls);
     }
 
+    @Transactional
+    public PhotoDownloadResponse getDownloadPresignedUrls(User user, PhotoDownloadRequest request) {
+        Album album = validateAlbumAndPermission(user, request.code());
+
+        List<Photo> photos = photoRepository.findAllByIdIn(request.photoIds());
+
+        albumValidator.validateDownloadPermission(album, user, photos);
+
+        Set<Long> recentDownloadIds = photoHistoryRepository.findRecentlyDownloadedPhotoIds(
+                user.getId(),
+                request.photoIds(),
+                LocalDateTime.now().minusHours(1)
+        );
+
+        List<PhotoDownloadResponse.DownloadFileInfo> presignedUrls = generateDownloadPresignedUrls(
+                photos, recentDownloadIds
+        );
+
+        photos.stream()
+                .filter(photo -> !recentDownloadIds.contains(photo.getId()))
+                .forEach(photo -> photoHistoryRepository.findByUserIdAndPhotoId(user.getId(), photo.getId())
+                        .ifPresentOrElse(
+                                PhotoHistory::touch,
+                                () -> photoHistoryRepository.save(PhotoHistoryMapper.toEntity(user, photo))
+                        )
+                );
+
+        return PhotoMapper.toPhotoDownloadResponse(presignedUrls);
+    }
+
     @Transactional
     public void reportUploadResult(User user, PhotoUploadReportRequest request) {
         List<Long> failurePhotoIds = request.failurePhotoIds().stream()
@@ -139,6 +178,15 @@ private List<PhotoPresignedUrlResponse.PresignedUrlInfo> generatePresignedUrls(
                 .collect(Collectors.toList());
     }
 
+    private List<PhotoDownloadResponse.DownloadFileInfo> generateDownloadPresignedUrls(
+            List<Photo> photos,
+            Set<Long> recentDownloadedIds
+    ) {
+        return photos.stream()
+                .map(photo -> createPresignedUrlForDownload(photo, recentDownloadedIds))
+                .toList();
+    }
+
     private PhotoPresignedUrlResponse.PresignedUrlInfo createPresignedUrlForFile(
             User user,
             Album album,
@@ -162,6 +210,20 @@ private PhotoPresignedUrlResponse.PresignedUrlInfo createPresignedUrlForFile(
         return PhotoMapper.toPresignedUrlInfo(photo.getId(), uploadUrl);
     }
 
+    private PhotoDownloadResponse.DownloadFileInfo createPresignedUrlForDownload(Photo photo, Set<Long> recentDownloadedIds) {
+        String fileName = S3Util.extractFileName(photo.getImageUrl());
+
+        // 1시간 이내 다운로드 O -> null 반환
+        if (recentDownloadedIds.contains(photo.getId())) {
+            return PhotoMapper.toDownloadPresignedUrlInfo(photo, fileName, null);
+        }
+
+        String objectKey = S3Util.extractObjectKey(photo.getImageUrl());
+        String url = presignedUrlService.generatePresignedGetUrl(objectKey);
+
+        return PhotoMapper.toDownloadPresignedUrlInfo(photo, fileName, url);
+    }
+
     private String sanitizeFileName(String raw) {
         String name = raw == null ? "unnamed" : raw;
         name = name.replace('\\', '/'); // 구분자 통일

src/main/java/com/cheeeese/photo/application/PresignedUrlService.java

@@ -3,8 +3,10 @@
 import lombok.RequiredArgsConstructor;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Component;
+import software.amazon.awssdk.services.s3.model.GetObjectRequest;
 import software.amazon.awssdk.services.s3.model.PutObjectRequest;
 import software.amazon.awssdk.services.s3.presigner.S3Presigner;
+import software.amazon.awssdk.services.s3.presigner.model.PresignedGetObjectRequest;
 import software.amazon.awssdk.services.s3.presigner.model.PresignedPutObjectRequest;
 
 import java.time.Duration;
@@ -33,4 +35,19 @@ public String generatePresignedPutUrl(String uniqueKey, String contentType) {
 
         return presignedRequest.url().toString();
     }
+
+    public String generatePresignedGetUrl(String uniqueKey) {
+        GetObjectRequest getObjectRequest = GetObjectRequest.builder()
+                .bucket(bucket)
+                .key(uniqueKey)
+                .build();
+
+        PresignedGetObjectRequest presignedRequest =
+                s3Presigner.presignGetObject(r -> r
+                        .signatureDuration(Duration.ofMinutes(10))
+                        .getObjectRequest(getObjectRequest)
+                );
+
+        return presignedRequest.url().toString();
+    }
 }

src/main/java/com/cheeeese/photo/domain/PhotoHistory.java

@@ -37,4 +37,8 @@ private PhotoHistory(User user, Photo photo) {
         this.user = user;
         this.photo = photo;
     }
+
+    public void touch() {
+        this.markUpdated();
+    }
 }

src/main/java/com/cheeeese/photo/dto/request/PhotoDownloadRequest.java

@@ -0,0 +1,17 @@
+package com.cheeeese.photo.dto.request;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import lombok.Builder;
+
+import java.util.List;
+
+@Builder
+@Schema(description = "사진 다운로드 presigned url 발급 API")
+public record PhotoDownloadRequest(
+        @Schema(description = "앨범 코드", example = "1f0b7ea8-fab6-6581-95e3-0720bc07603e")
+        String code,
+
+        @Schema(description = "사진 고유 ID", example = "[1, 2, 3]")
+        List<Long> photoIds
+) {
+}