feat: 채팅방 partner 정보를 조회하는 API 추가 (#457)

* feat: 채팅방 partner 정보를 조회하는 API 추가

* test: 채팅방 partner 정보를 조회 테스트 추가

Author: Gyuhyeok99

src/main/java/com/example/solidconnection/chat/controller/ChatController.java

@@ -1,6 +1,7 @@
 package com.example.solidconnection.chat.controller;
 
 import com.example.solidconnection.chat.dto.ChatMessageResponse;
+import com.example.solidconnection.chat.dto.ChatParticipantResponse;
 import com.example.solidconnection.chat.dto.ChatRoomListResponse;
 import com.example.solidconnection.chat.service.ChatService;
 import com.example.solidconnection.common.dto.SliceResponse;
@@ -41,6 +42,15 @@ public ResponseEntity<SliceResponse<ChatMessageResponse>> getChatMessages(
         return ResponseEntity.ok(response);
     }
 
+    @GetMapping("rooms/{room-id}/partner")
+    public ResponseEntity<ChatParticipantResponse> getChatPartner(
+            @AuthorizedUser long siteUserId,
+            @PathVariable("room-id") Long roomId
+    ) {
+        ChatParticipantResponse response = chatService.getChatPartner(siteUserId, roomId);
+        return ResponseEntity.ok(response);
+    }
+
     @PutMapping("/rooms/{room-id}/read")
     public ResponseEntity<Void> markChatMessagesAsRead(
             @AuthorizedUser long siteUserId,

src/main/java/com/example/solidconnection/chat/service/ChatService.java

@@ -84,16 +84,6 @@ private ChatRoomResponse toChatRoomResponse(ChatRoom chatRoom, long siteUserId)
         return ChatRoomResponse.of(chatRoom.getId(), lastChatMessage, lastReceivedTime, partner, unReadCount);
     }
 
-    private ChatParticipant findPartner(ChatRoom chatRoom, long siteUserId) {
-        if (chatRoom.isGroup()) {
-            throw new CustomException(INVALID_CHAT_ROOM_STATE);
-        }
-        return chatRoom.getChatParticipants().stream()
-                .filter(participant -> participant.getSiteUserId() != siteUserId)
-                .findFirst()
-                .orElseThrow(() -> new CustomException(CHAT_PARTNER_NOT_FOUND));
-    }
-
     @Transactional(readOnly = true)
     public SliceResponse<ChatMessageResponse> getChatMessages(long siteUserId, long roomId, Pageable pageable) {
         validateChatRoomParticipant(siteUserId, roomId);
@@ -107,6 +97,26 @@ public SliceResponse<ChatMessageResponse> getChatMessages(long siteUserId, long
         return SliceResponse.of(content, chatMessages);
     }
 
+    @Transactional(readOnly = true)
+    public ChatParticipantResponse getChatPartner(long siteUserId, Long roomId) {
+        ChatRoom chatRoom = chatRoomRepository.findById(roomId)
+                .orElseThrow(() -> new CustomException(INVALID_CHAT_ROOM_STATE));
+        ChatParticipant partnerParticipant = findPartner(chatRoom, siteUserId);
+        SiteUser siteUser = siteUserRepository.findById(partnerParticipant.getSiteUserId())
+                .orElseThrow(() -> new CustomException(USER_NOT_FOUND));
+        return ChatParticipantResponse.of(siteUser.getId(), siteUser.getNickname(), siteUser.getProfileImageUrl());
+    }
+
+    private ChatParticipant findPartner(ChatRoom chatRoom, long siteUserId) {
+        if (chatRoom.isGroup()) {
+            throw new CustomException(INVALID_CHAT_ROOM_STATE);
+        }
+        return chatRoom.getChatParticipants().stream()
+                .filter(participant -> participant.getSiteUserId() != siteUserId)
+                .findFirst()
+                .orElseThrow(() -> new CustomException(CHAT_PARTNER_NOT_FOUND));
+    }
+
     public void validateChatRoomParticipant(long siteUserId, long roomId) {
         boolean isParticipant = chatParticipantRepository.existsByChatRoomIdAndSiteUserId(roomId, siteUserId);
         if (!isParticipant) {

src/test/java/com/example/solidconnection/chat/service/ChatServiceTest.java

@@ -14,6 +14,7 @@
 import com.example.solidconnection.chat.dto.ChatMessageResponse;
 import com.example.solidconnection.chat.dto.ChatMessageSendRequest;
 import com.example.solidconnection.chat.dto.ChatMessageSendResponse;
+import com.example.solidconnection.chat.dto.ChatParticipantResponse;
 import com.example.solidconnection.chat.dto.ChatRoomListResponse;
 import com.example.solidconnection.chat.fixture.ChatAttachmentFixture;
 import com.example.solidconnection.chat.fixture.ChatMessageFixture;
@@ -309,6 +310,28 @@ void setUp() {
         }
     }
 
+    @Nested
+    class 채팅방_파트너_정보를_조회한다 {
+
+        @Test
+        void 채팅방_파트너를_정상_조회한다() {
+            // given
+            ChatRoom chatRoom = chatRoomFixture.채팅방(false);
+            chatParticipantFixture.참여자(user.getId(), chatRoom);
+            chatParticipantFixture.참여자(mentor1.getId(), chatRoom);
+
+            // when
+            ChatParticipantResponse response = chatService.getChatPartner(user.getId(), chatRoom.getId());
+
+            // then
+            assertAll(
+                    () -> assertThat(response.partnerId()).isEqualTo(mentor1.getId()),
+                    () -> assertThat(response.nickname()).isEqualTo(mentor1.getNickname()),
+                    () -> assertThat(response.profileUrl()).isEqualTo(mentor1.getProfileImageUrl())
+            );
+        }
+    }
+
     @Nested
     class 채팅_메시지_읽음을_처리한다 {