feat: backend returns whether user liked each post (efficiently using sets).

backend/src/main/java/online/wesal/wesal/dto/PostResponseDTO.java

@@ -11,6 +11,7 @@ public class PostResponseDTO {
     private String body;
     private String likes;
     private String comments;
+    private boolean liked;
     private LocalDateTime creationDate;
     
     public PostResponseDTO() {}
@@ -21,6 +22,17 @@ public class PostResponseDTO {
         this.body = post.getBody();
         this.likes = String.valueOf(post.getLikes());
         this.comments = String.valueOf(post.getComments());
+        this.liked = false; // Default value, will be set by service
+        this.creationDate = post.getCreationDate();
+    }
+    
+    public PostResponseDTO(Post post, User creator, boolean liked) {
+        this.id = String.valueOf(post.getId());
+        this.creator = new CreatorDTO(creator);
+        this.body = post.getBody();
+        this.likes = String.valueOf(post.getLikes());
+        this.comments = String.valueOf(post.getComments());
+        this.liked = liked;
         this.creationDate = post.getCreationDate();
     }
     
@@ -64,6 +76,14 @@ public class PostResponseDTO {
         this.comments = comments;
     }
     
+    public boolean isLiked() {
+        return liked;
+    }
+    
+    public void setLiked(boolean liked) {
+        this.liked = liked;
+    }
+    
     public LocalDateTime getCreationDate() {
         return creationDate;
     }

backend/src/main/java/online/wesal/wesal/repository/PostLikeRepository.java

@@ -2,9 +2,13 @@ package online.wesal.wesal.repository;
 
 import online.wesal.wesal.entity.PostLike;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
 
+import java.util.List;
 import java.util.Optional;
+import java.util.Set;
 
 @Repository
 public interface PostLikeRepository extends JpaRepository<PostLike, Long> {
@@ -12,4 +16,10 @@ public interface PostLikeRepository extends JpaRepository<PostLike, Long> {
     boolean existsByPostIdAndUserId(Long postId, Long userId);
     void deleteByPostIdAndUserId(Long postId, Long userId);
     long countByPostId(Long postId);
+    
+    @Query("SELECT pl.postId FROM PostLike pl WHERE pl.userId = :userId AND pl.postId IN :postIds")
+    Set<Long> findLikedPostIdsByUserIdAndPostIds(@Param("userId") Long userId, @Param("postIds") List<Long> postIds);
+    
+    @Query("SELECT pl.postId FROM PostLike pl WHERE pl.userId = :userId")
+    Set<Long> findAllLikedPostIdsByUserId(@Param("userId") Long userId);
 }

backend/src/main/java/online/wesal/wesal/service/PostService.java

@@ -14,6 +14,7 @@ import org.springframework.transaction.annotation.Transactional;
 import java.time.LocalDateTime;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 @Service
@@ -41,16 +42,30 @@ public class PostService {
         LocalDateTime sevenDaysAgo = LocalDateTime.now().minusDays(7);
         List<Post> posts = postRepository.findAllPostsWithinLast7Days(sevenDaysAgo);
         
+        User currentUser = userService.getCurrentUser();
+        Long currentUserId = currentUser.getId();
+        
+        // Get all unique creator IDs
         List<Long> creatorIds = posts.stream()
                 .map(Post::getCreatorId)
                 .distinct()
                 .collect(Collectors.toList());
         
+        // Get all post IDs
+        List<Long> postIds = posts.stream()
+                .map(Post::getId)
+                .collect(Collectors.toList());
+        
+        // Fetch creators in one query
         Map<Long, User> creators = userRepository.findAllById(creatorIds).stream()
                 .collect(Collectors.toMap(User::getId, user -> user));
         
+        // Fetch user's likes for these posts in one query
+        Set<Long> likedPostIds = postLikeRepository.findLikedPostIdsByUserIdAndPostIds(currentUserId, postIds);
+        
         return posts.stream()
-                .map(post -> new PostResponseDTO(post, creators.get(post.getCreatorId())))
+                .map(post -> new PostResponseDTO(post, creators.get(post.getCreatorId()), 
+                     likedPostIds.contains(post.getId())))
                 .collect(Collectors.toList());
     }
     
@@ -59,8 +74,19 @@ public class PostService {
         User creator = userRepository.findById(userId)
                 .orElseThrow(() -> new RuntimeException("User not found"));
         
+        User currentUser = userService.getCurrentUser();
+        Long currentUserId = currentUser.getId();
+        
+        // Get all post IDs
+        List<Long> postIds = posts.stream()
+                .map(Post::getId)
+                .collect(Collectors.toList());
+        
+        // Fetch user's likes for these posts in one query
+        Set<Long> likedPostIds = postLikeRepository.findLikedPostIdsByUserIdAndPostIds(currentUserId, postIds);
+        
         return posts.stream()
-                .map(post -> new PostResponseDTO(post, creator))
+                .map(post -> new PostResponseDTO(post, creator, likedPostIds.contains(post.getId())))
                 .collect(Collectors.toList());
     }
     
@@ -68,7 +94,7 @@ public class PostService {
         User currentUser = userService.getCurrentUser();
         Post post = new Post(currentUser.getId(), body);
         post = postRepository.save(post);
-        return new PostResponseDTO(post, currentUser);
+        return new PostResponseDTO(post, currentUser, false); // New post is not liked by default
     }
     
     @Transactional
@@ -95,7 +121,10 @@ public class PostService {
         User creator = userRepository.findById(post.getCreatorId())
                 .orElseThrow(() -> new RuntimeException("Creator not found"));
         
-        return new PostResponseDTO(post, creator);
+        // Check if user now likes this post
+        boolean isLiked = postLikeRepository.existsByPostIdAndUserId(postId, userId);
+        
+        return new PostResponseDTO(post, creator, isLiked);
     }
     
     @Transactional
@@ -121,6 +150,9 @@ public class PostService {
         User creator = userRepository.findById(post.getCreatorId())
                 .orElseThrow(() -> new RuntimeException("Creator not found"));
         
-        return new PostResponseDTO(post, creator);
+        // Check if user now likes this post
+        boolean isLiked = postLikeRepository.existsByPostIdAndUserId(postId, userId);
+        
+        return new PostResponseDTO(post, creator, isLiked);
     }
 }