remove follow

src/main/java/io/spring/api/ProfileApi.java

@@ -9,6 +9,7 @@ import io.spring.core.user.UserRepository;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.web.bind.annotation.DeleteMapping;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.PostMapping;
@@ -16,6 +17,7 @@ import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
 
 import java.util.HashMap;
+import java.util.Optional;
 
 @RestController
 @RequestMapping(path = "profiles/{username}")
@@ -47,6 +49,22 @@ public class ProfileApi {
         }).orElseThrow(ResourceNotFoundException::new);
     }
 
+    @DeleteMapping(path = "follow")
+    public ResponseEntity unfollow(@PathVariable("username") String username,
+                                   @AuthenticationPrincipal User user) {
+        Optional<User> userOptional = userRepository.findByUsername(username);
+        if (userOptional.isPresent()) {
+            User target = userOptional.get();
+            return userRepository.findRelation(user.getId(), target.getId())
+                .map(relation -> {
+                    userRepository.removeRelation(relation);
+                    return profileResponse(profileQueryService.findByUsername(username, user).get());
+                }).orElseThrow(ResourceNotFoundException::new);
+        } else {
+            throw new ResourceNotFoundException();
+        }
+    }
+
     private ResponseEntity profileResponse(ProfileData profile) {
         return ResponseEntity.ok(new HashMap<String, Object>() {{
             put("profile", profile);

src/main/java/io/spring/core/user/UserRepository.java

@@ -17,4 +17,6 @@ public interface UserRepository {
     void saveRelation(FollowRelation followRelation);
 
     Optional<FollowRelation> findRelation(String userId, String targetId);
+
+    void removeRelation(FollowRelation followRelation);
 }

src/main/java/io/spring/infrastructure/user/MyBatisUserRepository.java

@@ -43,11 +43,18 @@ public class MyBatisUserRepository implements UserRepository {
 
     @Override
     public void saveRelation(FollowRelation followRelation) {
-        userMapper.saveRelation(followRelation);
+        if (!findRelation(followRelation.getUserId(), followRelation.getTargetId()).isPresent()) {
+            userMapper.saveRelation(followRelation);
+        }
     }
 
     @Override
     public Optional<FollowRelation> findRelation(String userId, String targetId) {
         return Optional.ofNullable(userMapper.findRelation(userId, targetId));
     }
+
+    @Override
+    public void removeRelation(FollowRelation followRelation) {
+        userMapper.deleteRelation(followRelation);
+    }
 }

src/main/java/io/spring/infrastructure/user/UserMapper.java

@@ -21,4 +21,6 @@ public interface UserMapper {
     FollowRelation findRelation(@Param("userId") String userId, @Param("targetId") String targetId);
 
     void saveRelation(@Param("followRelation") FollowRelation followRelation);
+
+    void deleteRelation(@Param("followRelation") FollowRelation followRelation);
 }