Add reaction module

src/main/java/com/openisle/service/ReactionService.java

@@ -0,0 +1,49 @@
+package com.openisle.service;
+
+import com.openisle.model.Comment;
+import com.openisle.model.Post;
+import com.openisle.model.Reaction;
+import com.openisle.model.ReactionType;
+import com.openisle.model.User;
+import com.openisle.repository.CommentRepository;
+import com.openisle.repository.PostRepository;
+import com.openisle.repository.ReactionRepository;
+import com.openisle.repository.UserRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+
+@Service
+@RequiredArgsConstructor
+public class ReactionService {
+    private final ReactionRepository reactionRepository;
+    private final UserRepository userRepository;
+    private final PostRepository postRepository;
+    private final CommentRepository commentRepository;
+
+    public Reaction reactToPost(String username, Long postId, ReactionType type) {
+        User user = userRepository.findByUsername(username)
+                .orElseThrow(() -> new IllegalArgumentException("User not found"));
+        Post post = postRepository.findById(postId)
+                .orElseThrow(() -> new IllegalArgumentException("Post not found"));
+        Reaction reaction = reactionRepository.findByUserAndPost(user, post)
+                .orElseGet(Reaction::new);
+        reaction.setUser(user);
+        reaction.setPost(post);
+        reaction.setType(type);
+        return reactionRepository.save(reaction);
+    }
+
+    public Reaction reactToComment(String username, Long commentId, ReactionType type) {
+        User user = userRepository.findByUsername(username)
+                .orElseThrow(() -> new IllegalArgumentException("User not found"));
+        Comment comment = commentRepository.findById(commentId)
+                .orElseThrow(() -> new IllegalArgumentException("Comment not found"));
+        Reaction reaction = reactionRepository.findByUserAndComment(user, comment)
+                .orElseGet(Reaction::new);
+        reaction.setUser(user);
+        reaction.setComment(comment);
+        reaction.setPost(null);
+        reaction.setType(type);
+        return reactionRepository.save(reaction);
+    }
+}