优化目录结构

backend/src/main/java/com/openisle/service/PostReadService.java

@@ -0,0 +1,49 @@
+package com.openisle.service;
+
+import com.openisle.model.Post;
+import com.openisle.model.PostRead;
+import com.openisle.model.User;
+import com.openisle.repository.PostReadRepository;
+import com.openisle.repository.PostRepository;
+import com.openisle.repository.UserRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+
+import java.time.LocalDateTime;
+
+@Service
+@RequiredArgsConstructor
+public class PostReadService {
+    private final PostReadRepository postReadRepository;
+    private final UserRepository userRepository;
+    private final PostRepository postRepository;
+
+    public void recordRead(String username, Long postId) {
+        if (username == null) return;
+        User user = userRepository.findByUsername(username)
+                .orElseThrow(() -> new com.openisle.exception.NotFoundException("User not found"));
+        Post post = postRepository.findById(postId)
+                .orElseThrow(() -> new com.openisle.exception.NotFoundException("Post not found"));
+        postReadRepository.findByUserAndPost(user, post).ifPresentOrElse(pr -> {
+            pr.setLastReadAt(LocalDateTime.now());
+            postReadRepository.save(pr);
+        }, () -> {
+            PostRead pr = new PostRead();
+            pr.setUser(user);
+            pr.setPost(post);
+            pr.setLastReadAt(LocalDateTime.now());
+            postReadRepository.save(pr);
+        });
+    }
+
+    public long countReads(String username) {
+        User user = userRepository.findByUsername(username)
+                .orElseThrow(() -> new com.openisle.exception.NotFoundException("User not found"));
+        return postReadRepository.countByUser(user);
+    }
+
+    @org.springframework.transaction.annotation.Transactional
+    public void deleteByPost(Post post) {
+        postReadRepository.deleteByPost(post);
+    }
+}