작성자 검색 기능 추가

src/main/java/com/example/log4u/domain/user/controller/UserController.java

@@ -15,9 +15,11 @@
 import org.springframework.web.bind.annotation.PutMapping;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.bind.annotation.RestController;
 
 import com.example.log4u.common.constants.UrlConstants;
+import com.example.log4u.common.dto.PageResponse;
 import com.example.log4u.common.oauth2.dto.CustomOAuth2User;
 import com.example.log4u.domain.user.dto.NicknameValidationResponseDto;
 import com.example.log4u.domain.user.dto.UserProfileMakeRequestDto;
@@ -134,4 +136,16 @@ public ResponseEntity<NicknameValidationResponseDto> validateNickname(
 	) {
 		return ResponseEntity.ok(userService.validateNickname(nickname));
 	}
+
+	@GetMapping("/search")
+	public ResponseEntity<PageResponse<UserProfileResponseDto>> searchUsers(
+		@AuthenticationPrincipal CustomOAuth2User customOAuth2User,
+		@RequestParam(required = false) String nickname,
+		@RequestParam(required = false) Long cursorId,
+		@RequestParam(defaultValue = "12") int size
+	) {
+		return ResponseEntity.ok(
+			userService.searchUsersByCursor(nickname, cursorId, size)
+		);
+	}
 }

src/main/java/com/example/log4u/domain/user/repository/UserRepository.java

@@ -2,7 +2,11 @@
 
 import java.util.Optional;
 
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.domain.Slice;
 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 com.example.log4u.domain.user.entity.User;
@@ -14,4 +18,20 @@ public interface UserRepository extends JpaRepository<User, Long> {
 	Boolean existsByNickname(String nickname);
 
 	Optional<User> findByProviderId(String providerId);
+
+	@Query(value = """
+		SELECT u FROM User u
+		LEFT JOIN (SELECT f.targetId, COUNT(f) as followerCount 
+		          FROM Follow f 
+		          GROUP BY f.targetId) fc 
+		ON u.userId = fc.targetId
+		WHERE (:nickname IS NULL OR LOWER(u.nickname) LIKE LOWER(CONCAT('%', :nickname, '%')))
+		AND u.userId < :cursorId
+		ORDER BY fc.followerCount DESC NULLS LAST, u.userId DESC
+		""")
+	Slice<User> searchUsersByCursor(
+		@Param("nickname") String nickname,
+		@Param("cursorId") Long cursorId,
+		Pageable pageable
+	);
 }

src/main/java/com/example/log4u/domain/user/service/UserService.java

@@ -1,8 +1,14 @@
 package com.example.log4u.domain.user.service;
 
+import java.util.List;
+
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Slice;
+import org.springframework.data.domain.SliceImpl;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import com.example.log4u.common.dto.PageResponse;
 import com.example.log4u.domain.follow.repository.FollowRepository;
 import com.example.log4u.domain.user.dto.NicknameValidationResponseDto;
 import com.example.log4u.domain.user.dto.UserProfileMakeRequestDto;
@@ -13,7 +19,9 @@
 import com.example.log4u.domain.user.repository.UserRepository;
 
 import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
 
+@Slf4j
 @Service
 @RequiredArgsConstructor
 public class UserService {
@@ -87,4 +95,33 @@ public Long getUserIdByNickname(String nickname) {
 		).getUserId();
 	}
 
+	@Transactional(readOnly = true)
+	public PageResponse<UserProfileResponseDto> searchUsersByCursor(
+		String nickname,
+		Long cursorId,
+		int size
+	) {
+		Slice<User> userSlice = userRepository.searchUsersByCursor(
+			nickname,
+			cursorId != null ? cursorId : Long.MAX_VALUE,
+			PageRequest.of(0, size)
+		);
+
+		List<UserProfileResponseDto> content = userSlice.getContent().stream()
+			.map(user -> {
+				Long userId = user.getUserId();
+				Long followers = followRepository.countByTargetId(userId);
+				Long followings = followRepository.countByInitiatorId(userId);
+				return UserProfileResponseDto.fromUser(user, followers, followings);
+			})
+			.toList();
+
+		// 다음 커서 ID 계산
+		Long nextCursor = content.isEmpty() ? null : content.get(content.size() - 1).userId();
+
+		return PageResponse.of(
+			new SliceImpl<>(content, userSlice.getPageable(), userSlice.hasNext()),
+			nextCursor
+		);
+	}
 }

src/test/java/com/example/log4u/domain/user/service/UserServiceTest.java

@@ -3,17 +3,25 @@
 import static org.junit.jupiter.api.Assertions.*;
 import static org.mockito.BDDMockito.*;
 
+import java.util.List;
 import java.util.Optional;
 
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.ArgumentMatchers;
 import org.mockito.InjectMocks;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Slice;
+import org.springframework.data.domain.SliceImpl;
 
+import com.example.log4u.common.dto.PageResponse;
+import com.example.log4u.domain.follow.repository.FollowRepository;
 import com.example.log4u.domain.user.dto.NicknameValidationResponseDto;
 import com.example.log4u.domain.user.dto.UserProfileMakeRequestDto;
+import com.example.log4u.domain.user.dto.UserProfileResponseDto;
 import com.example.log4u.domain.user.dto.UserProfileUpdateRequestDto;
 import com.example.log4u.domain.user.entity.User;
 import com.example.log4u.domain.user.exception.UserNotFoundException;
@@ -29,7 +37,10 @@ class UserServiceTest {
 
 	@Mock
 	private UserRepository userRepository;
-
+
+	@Mock
+	private FollowRepository followRepository;
+
 	@Test
 	@DisplayName("내 프로필을 생성하고 저장해야 한다.")
 	void shouldCreateAndSaveMyUserProfile() {
@@ -116,4 +127,103 @@ void shouldThrowExceptionWhenUserNotFound() {
 		verify(userRepository).findById(userId);
 	}
 
+	@Test
+	@DisplayName("닉네임으로 유저를 검색하고 팔로워 수 높은 순으로 정렬해야 한다")
+	void shouldSearchUsersByNicknameAndSortByFollowerCount() {
+		// given
+		String nickname = "test";
+		Long cursorId = null;
+		int size = 10;
+
+		// 테스트용 유저 목록 생성
+		User user1 = UserFixture.createUserWithId(1L, "User1", "test1");
+		User user2 = UserFixture.createUserWithId(2L, "User2", "test2");
+		User user3 = UserFixture.createUserWithId(3L, "User3", "test3");
+
+		List<User> users = List.of(user1, user2, user3);
+		Slice<User> userSlice = new SliceImpl<>(users, PageRequest.of(0, size), false);
+
+		// Mock 설정
+		when(userRepository.searchUsersByCursor(
+			eq(nickname),
+			eq(Long.MAX_VALUE),
+			ArgumentMatchers.any(PageRequest.class)))
+			.thenReturn(userSlice);
+
+		// 각 유저의 팔로워/팔로잉 수 설정
+		when(followRepository.countByTargetId(1L)).thenReturn(10L);
+		when(followRepository.countByInitiatorId(1L)).thenReturn(5L);
+
+		when(followRepository.countByTargetId(2L)).thenReturn(20L);
+		when(followRepository.countByInitiatorId(2L)).thenReturn(15L);
+
+		when(followRepository.countByTargetId(3L)).thenReturn(30L);
+		when(followRepository.countByInitiatorId(3L)).thenReturn(25L);
+
+		// when
+		PageResponse<UserProfileResponseDto> result = userService.searchUsersByCursor(nickname, cursorId, size);
+
+		// then
+		assertNotNull(result);
+		assertEquals(3, result.list().size());
+
+		// 팔로워 수 확인
+		assertEquals(10L, result.list().get(0).followers());
+		assertEquals(20L, result.list().get(1).followers());
+		assertEquals(30L, result.list().get(2).followers());
+
+		// 팔로잉 수 확인
+		assertEquals(5L, result.list().get(0).followings());
+		assertEquals(15L, result.list().get(1).followings());
+		assertEquals(25L, result.list().get(2).followings());
+
+		// 다음 커서 확인
+		assertEquals(3L, result.pageInfo().nextCursor());
+
+		// 메서드 호출 확인
+		verify(userRepository).searchUsersByCursor(
+			eq(nickname),
+			eq(Long.MAX_VALUE),
+			ArgumentMatchers.any(PageRequest.class));
+
+		verify(followRepository, times(3)).countByTargetId(anyLong());
+		verify(followRepository, times(3)).countByInitiatorId(anyLong());
+	}
+
+	@Test
+	@DisplayName("검색 결과가 없으면 빈 리스트를 반환해야 한다")
+	void shouldReturnEmptyListWhenNoSearchResults() {
+		// given
+		String nickname = "nonexistent";
+		Long cursorId = null;
+		int size = 10;
+
+		List<User> emptyList = List.of();
+		Slice<User> emptySlice = new SliceImpl<>(emptyList, PageRequest.of(0, size), false);
+
+		// Mock 설정
+		when(userRepository.searchUsersByCursor(
+			eq(nickname),
+			eq(Long.MAX_VALUE),
+			ArgumentMatchers.any(PageRequest.class)))
+			.thenReturn(emptySlice);
+
+		// when
+		PageResponse<UserProfileResponseDto> result = userService.searchUsersByCursor(nickname, cursorId, size);
+
+		// then
+		assertNotNull(result);
+		assertTrue(result.list().isEmpty());
+		assertNull(result.pageInfo().nextCursor());
+
+		// 메서드 호출 확인
+		verify(userRepository).searchUsersByCursor(
+			eq(nickname),
+			eq(Long.MAX_VALUE),
+			ArgumentMatchers.any(PageRequest.class));
+
+		// 팔로워/팔로잉 수 조회 메서드가 호출되지 않아야 함
+		verify(followRepository, never()).countByTargetId(anyLong());
+		verify(followRepository, never()).countByInitiatorId(anyLong());
+	}
 }

src/test/java/com/example/log4u/fixture/UserFixture.java

@@ -60,5 +60,17 @@ public static User createPremiumUserFixture(String nickname) {
 			.isPremium(true)
 			.build();
 	}
-}
 
+	public static User createUserWithId(Long userId, String name, String nickname) {
+		return User.builder()
+			.userId(userId)
+			.name(name)
+			.nickname(nickname)
+			.statusMessage("Test status message")
+			.profileImage("test-profile-image.jpg")
+			.role("ROLE_USER")
+			.providerId("test-provider-id")
+			.socialType(SocialType.GOOGLE) // 또는 다른 소셜 타입
+			.build();
+	}
+}