start backend

src/main/java/com/krylov/refound/service/FavoriteService.java

@@ -0,0 +1,79 @@
+package com.krylov.refound.service;
+
+import com.krylov.refound.entity.Favorite;
+import com.krylov.refound.entity.Post;
+import com.krylov.refound.entity.User;
+import com.krylov.refound.enums.ErrorCode;
+import com.krylov.refound.exception.ApiException;
+import com.krylov.refound.repository.FavoriteRepository;
+import com.krylov.refound.repository.PostRepository;
+import java.util.List;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
+import org.springframework.stereotype.Service;
+
+@Service
+@RequiredArgsConstructor
+public class FavoriteService {
+  private final FavoriteRepository repository;
+  private final PostRepository postRepository;
+  private final UserService userService;
+
+  public void addToFavorites(Long postId) {
+
+    User user = userService.getCurrentUser();
+
+    Post post = postRepository.findById(postId)
+        .orElseThrow(() -> new ApiException(ErrorCode.NOT_FOUND, "Post not found", HttpStatus.NOT_FOUND));
+
+    if (repository.existsByUserAndPost(user, post)) {
+      return; // уже есть
+    }
+
+    Favorite favorite = new Favorite();
+    favorite.setUser(user);
+    favorite.setPost(post);
+
+    repository.save(favorite);
+  }
+
+  public void removeFromFavorites(Long postId) {
+
+    User user = userService.getCurrentUser();
+
+    Post post = postRepository.findById(postId)
+        .orElseThrow(() -> new ApiException(ErrorCode.NOT_FOUND, "Post not found", HttpStatus.NOT_FOUND));
+
+    repository.deleteByUserAndPost(user, post);
+  }
+
+  public List<Post> getFavorites() {
+    User user = userService.getCurrentUser();
+
+    return repository.findByUser(user)
+        .stream()
+        .map(Favorite::getPost)
+        .toList();
+  }
+
+  public void toggle(Long postId) {
+
+    User user = userService.getCurrentUser();
+
+    Post post = postRepository.findById(postId)
+        .orElseThrow(() -> new ApiException(
+            ErrorCode.NOT_FOUND,
+            "Post not found",
+            HttpStatus.NOT_FOUND
+        ));
+
+    if (repository.existsByUserAndPost(user, post)) {
+      repository.deleteByUserAndPost(user, post);
+    } else {
+      Favorite f = new Favorite();
+      f.setUser(user);
+      f.setPost(post);
+      repository.save(f);
+    }
+  }
+}