feat(be): 유저,가이드 채팅방 제목 관련 로직 추가

docs/api-specification.yaml

@@ -182,7 +182,10 @@ components:
           description: 채팅방 고유 식별자
         title:
           type: string
-          description: 채팅방 제목(Guide-User 조합)
+          description: 채팅방 내부 식별용 기본 제목 (Guide-사용자 ID 조합)
+        displayTitle:
+          type: string
+          description: 요청자 기준 상대 닉네임을 포함한 표현용 제목 (예: "홍길동님과의 채팅")
         guideId:
           type: integer
           format: int64

src/main/kotlin/com/back/koreaTravelGuide/domain/userChat/chatroom/controller/ChatRoomController.kt

@@ -42,7 +42,8 @@ class ChatRoomController(
     ): ResponseEntity<ApiResponse<ChatRoomResponse>> {
         val authenticatedId = requesterId ?: throw AccessDeniedException("인증이 필요합니다.")
         val room = roomService.createOneToOneRoom(req.guideId, req.userId, authenticatedId)
-        return ResponseEntity.ok(ApiResponse(msg = "채팅방 시작", data = ChatRoomResponse.from(room)))
+        val responseData = roomService.toResponse(room, authenticatedId)
+        return ResponseEntity.ok(ApiResponse(msg = "채팅방 시작", data = responseData))
     }
 
     @DeleteMapping("/{roomId}")
@@ -61,7 +62,7 @@ class ChatRoomController(
         @AuthenticationPrincipal requesterId: Long?,
     ): ResponseEntity<ApiResponse<ChatRoomResponse>> {
         val authenticatedId = requesterId ?: throw AccessDeniedException("인증이 필요합니다.")
-        val room = roomService.get(roomId, authenticatedId)
-        return ResponseEntity.ok(ApiResponse(msg = "채팅방 조회", data = ChatRoomResponse.from(room)))
+        val responseData = roomService.getResponse(roomId, authenticatedId)
+        return ResponseEntity.ok(ApiResponse(msg = "채팅방 조회", data = responseData))
     }
 }

src/main/kotlin/com/back/koreaTravelGuide/domain/userChat/chatroom/dto/ChatRoomResponse.kt

@@ -7,16 +7,21 @@ import java.time.ZonedDateTime
 data class ChatRoomResponse(
     val id: Long?,
     val title: String,
+    val displayTitle: String,
     val guideId: Long,
     val userId: Long,
     val updatedAt: ZonedDateTime = ZonedDateTime.now(ZoneId.of("Asia/Seoul")),
     val lastMessageId: Long?,
 ) {
     companion object {
-        fun from(room: ChatRoom): ChatRoomResponse {
+        fun from(
+            room: ChatRoom,
+            displayTitle: String? = null,
+        ): ChatRoomResponse {
             return ChatRoomResponse(
                 id = room.id,
                 title = room.title,
+                displayTitle = displayTitle ?: room.title,
                 guideId = room.guideId,
                 userId = room.userId,
                 updatedAt = room.updatedAt,

src/main/kotlin/com/back/koreaTravelGuide/domain/userChat/chatroom/service/ChatRoomService.kt

@@ -1,5 +1,7 @@
 package com.back.koreaTravelGuide.domain.userChat.chatroom.service
 
+import com.back.koreaTravelGuide.domain.user.entity.User
+import com.back.koreaTravelGuide.domain.user.repository.UserRepository
 import com.back.koreaTravelGuide.domain.userChat.chatmessage.repository.ChatMessageRepository
 import com.back.koreaTravelGuide.domain.userChat.chatroom.dto.ChatRoomListResponse
 import com.back.koreaTravelGuide.domain.userChat.chatroom.dto.ChatRoomResponse
@@ -17,6 +19,7 @@ import java.util.NoSuchElementException
 class ChatRoomService(
     private val roomRepository: ChatRoomRepository,
     private val messageRepository: ChatMessageRepository,
+    private val userRepository: UserRepository,
 ) {
     @Transactional
     fun createOneToOneRoom(
@@ -74,7 +77,11 @@ class ChatRoomService(
         val (cursorUpdatedAt, cursorRoomId) = parseCursor(cursor)
         val pageable = PageRequest.of(0, limit)
         val rooms = roomRepository.findPagedByMember(requesterId, cursorUpdatedAt, cursorRoomId, pageable)
-        val roomResponses = rooms.map(ChatRoomResponse::from)
+        val usersById = loadUsersFor(rooms)
+        val roomResponses =
+            rooms.map { room ->
+                toResponse(room, requesterId, usersById)
+            }
         val nextCursor =
             if (roomResponses.size < limit) {
                 null
@@ -90,6 +97,52 @@ class ChatRoomService(
         )
     }
 
+    @Transactional(readOnly = true)
+    fun getResponse(
+        roomId: Long,
+        requesterId: Long,
+    ): ChatRoomResponse {
+        val room = get(roomId, requesterId)
+        val usersById = loadUsersFor(listOf(room))
+        return toResponse(room, requesterId, usersById)
+    }
+
+    fun toResponse(
+        room: ChatRoom,
+        viewerId: Long,
+    ): ChatRoomResponse {
+        val usersById = loadUsersFor(listOf(room))
+        return toResponse(room, viewerId, usersById)
+    }
+
+    private fun toResponse(
+        room: ChatRoom,
+        viewerId: Long,
+        cachedUsers: Map<Long, User>,
+    ): ChatRoomResponse {
+        val displayTitle = buildDisplayTitle(room, viewerId, cachedUsers)
+        return ChatRoomResponse.from(room, displayTitle)
+    }
+
+    private fun loadUsersFor(rooms: Collection<ChatRoom>): Map<Long, User> {
+        val ids = rooms.flatMap { listOf(it.guideId, it.userId) }.toSet()
+        if (ids.isEmpty()) {
+            return emptyMap()
+        }
+        return userRepository.findAllById(ids).associateBy { it.id!! }
+    }
+
+    private fun buildDisplayTitle(
+        room: ChatRoom,
+        viewerId: Long,
+        cachedUsers: Map<Long, User>,
+    ): String {
+        val guideNickname = cachedUsers[room.guideId]?.nickname ?: "Guide-${room.guideId}"
+        val userNickname = cachedUsers[room.userId]?.nickname ?: "User-${room.userId}"
+        val counterpartName = if (viewerId == room.guideId) userNickname else guideNickname
+        return "${counterpartName}님과의 채팅"
+    }
+
     private fun parseCursor(cursor: String?): Pair<ZonedDateTime?, Long?> {
         if (cursor.isNullOrBlank()) {
             return null to null

src/test/kotlin/com/back/koreaTravelGuide/domain/userChat/chatroom/controller/ChatRoomControllerTest.kt

@@ -125,6 +125,7 @@ class ChatRoomControllerTest {
                 .andExpect(status().isOk)
                 .andExpect(jsonPath("$.data.rooms.length()").value(3))
                 .andExpect(jsonPath("$.data.rooms[0].id").value(existingRoom.id!!.toInt()))
+                .andExpect(jsonPath("$.data.rooms[0].displayTitle").value("${guide.nickname}님과의 채팅"))
                 .andReturn()
 
         val firstCursorNode = objectMapper.readTree(firstPage.response.contentAsString)["data"]["nextCursor"]
@@ -139,7 +140,8 @@ class ChatRoomControllerTest {
         )
             .andExpect(status().isOk)
             .andExpect(jsonPath("$.data.rooms.length()").value(3))
-            .andExpect(jsonPath("$.data.rooms[0].id").exists()) // 도커 환경에서 정렬 순서가 다를 수 있어 ID 존재만 확인
+            .andExpect(jsonPath("$.data.rooms[0].id").value(extraRooms[2].id!!.toInt()))
+            .andExpect(jsonPath("$.data.rooms[0].displayTitle").value("guide3님과의 채팅"))
     }
 
     @Test
@@ -156,6 +158,7 @@ class ChatRoomControllerTest {
             .andExpect(jsonPath("$.data.id").value(existingRoom.id!!.toInt()))
             .andExpect(jsonPath("$.data.guideId").value(guide.id!!.toInt()))
             .andExpect(jsonPath("$.data.userId").value(guest.id!!.toInt()))
+            .andExpect(jsonPath("$.data.displayTitle").value("${guide.nickname}님과의 채팅"))
     }
 
     @Test
@@ -168,6 +171,7 @@ class ChatRoomControllerTest {
             .andExpect(status().isOk)
             .andExpect(jsonPath("$.data.id").value(existingRoom.id!!.toInt()))
             .andExpect(jsonPath("$.data.title").value(existingRoom.title))
+            .andExpect(jsonPath("$.data.displayTitle").value("${guest.nickname}님과의 채팅"))
     }
 
     @Test