채팅방 생성 api 추가

backend/ddang/src/main/java/com/ddang/ddang/auction/domain/Auction.java

@@ -1,5 +1,6 @@
 package com.ddang.ddang.auction.domain;
 
+import com.ddang.ddang.auction.domain.exception.WinnerNotFoundException;
 import com.ddang.ddang.bid.domain.Bid;
 import com.ddang.ddang.bid.domain.BidPrice;
 import com.ddang.ddang.category.domain.Category;
@@ -147,4 +148,25 @@ private BidPrice calculateNextMinimumBidPrice() {
         final int nextMinimumBidPrice = this.lastBid.getPrice().getValue() + this.bidUnit.getValue();
         return new BidPrice(nextMinimumBidPrice);
     }
+
+    public boolean isWinner(final User user, final LocalDateTime targetTime) {
+        final User winner = findWinner(targetTime);
+
+        return user.equals(winner);
+    }
+
+    public User findWinner(final LocalDateTime targetTime) {
+        checkWinnerExist(targetTime);
+
+        return lastBid.getBidder();
+    }
+
+    private void checkWinnerExist(final LocalDateTime targetTime) {
+        if (!isClosed(targetTime)) {
+            throw new WinnerNotFoundException("경매가 종료된 후에 낙찰자가 결정됩니다.");
+        }
+        if (auctioneerCount == 0) {
+            throw new WinnerNotFoundException("입찰자가 존재하지 않아 낙찰자가 없습니다.");
+        }
+    }
 }

backend/ddang/src/main/java/com/ddang/ddang/auction/domain/exception/WinnerNotFoundException.java

@@ -0,0 +1,8 @@
+package com.ddang.ddang.auction.domain.exception;
+
+public class WinnerNotFoundException extends IllegalArgumentException {
+
+    public WinnerNotFoundException(final String message) {
+        super(message);
+    }
+}

backend/ddang/src/main/java/com/ddang/ddang/chat/application/ChatRoomService.java

@@ -1,7 +1,13 @@
 package com.ddang.ddang.chat.application;
 
+import com.ddang.ddang.auction.application.exception.AuctionNotFoundException;
+import com.ddang.ddang.auction.domain.Auction;
+import com.ddang.ddang.auction.infrastructure.persistence.JpaAuctionRepository;
+import com.ddang.ddang.chat.application.dto.CreateChatRoomDto;
 import com.ddang.ddang.chat.application.dto.ReadParticipatingChatRoomDto;
+import com.ddang.ddang.chat.application.exception.ChatAlreadyExistException;
 import com.ddang.ddang.chat.application.exception.ChatRoomNotFoundException;
+import com.ddang.ddang.chat.application.exception.InvalidAuctionToChatException;
 import com.ddang.ddang.chat.application.exception.UserNotAccessibleException;
 import com.ddang.ddang.chat.application.exception.UserNotFoundException;
 import com.ddang.ddang.chat.domain.ChatRoom;
@@ -14,6 +20,7 @@
 
 import java.time.LocalDateTime;
 import java.util.List;
+import java.util.Optional;
 
 @Service
 @Transactional(readOnly = true)
@@ -22,21 +29,64 @@ public class ChatRoomService {
 
     private final JpaChatRoomRepository chatRoomRepository;
     private final JpaUserRepository userRepository;
+    private final JpaAuctionRepository auctionRepository;
 
-    public List<ReadParticipatingChatRoomDto> readAllByUserId(final Long userId) {
+    @Transactional
+    public Long create(final Long userId, final CreateChatRoomDto chatRoomDto) {
         final User findUser = findUser(userId);
-        final List<ChatRoom> chatRooms = chatRoomRepository.findAllByUserId(findUser.getId());
+        final Auction findAuction = findAuction(chatRoomDto);
 
-        return chatRooms.stream()
-                        .map(chatRoom -> toDto(findUser, chatRoom))
-                        .toList();
+        checkAuctionStatus(findAuction);
+        checkUserCanParticipate(findUser, findAuction);
+        checkAlreadyExist(findAuction);
+
+        final ChatRoom chatRoom = chatRoomDto.toEntity(findAuction);
+
+        return chatRoomRepository.save(chatRoom)
+                                 .getId();
     }
 
     private User findUser(final Long userId) {
         return userRepository.findById(userId)
                              .orElseThrow(() -> new UserNotFoundException("사용자 정보를 찾을 수 없습니다."));
     }
 
+    private Auction findAuction(final CreateChatRoomDto chatRoomDto) {
+        return auctionRepository.findById(chatRoomDto.auctionId())
+                                .orElseThrow(() -> new AuctionNotFoundException("해당 경매를 찾을 수 없습니다."));
+    }
+
+    private void checkAuctionStatus(final Auction findAuction) {
+        if (!findAuction.isClosed(LocalDateTime.now())) {
+            throw new InvalidAuctionToChatException("경매가 아직 종료되지 않았습니다.");
+        }
+        if (findAuction.isDeleted()) {
+            throw new InvalidAuctionToChatException("삭제된 경매입니다.");
+        }
+    }
+
+    private void checkUserCanParticipate(final User findUser, final Auction findAuction) {
+        if (!findAuction.isOwner(findUser) && !findAuction.isWinner(findUser, LocalDateTime.now())) {
+            throw new UserNotAccessibleException("경매의 판매자 또는 최종 낙찰자만 채팅이 가능합니다.");
+        }
+    }
+
+    private void checkAlreadyExist(final Auction findAuction) {
+        final Optional<ChatRoom> nullableChatRoom = chatRoomRepository.findByAuctionId(findAuction.getId());
+        if (nullableChatRoom.isPresent()) {
+            throw new ChatAlreadyExistException("해당 경매에 대한 채팅방이 이미 존재합니다.");
+        }
+    }
+
+    public List<ReadParticipatingChatRoomDto> readAllByUserId(final Long userId) {
+        final User findUser = findUser(userId);
+        final List<ChatRoom> chatRooms = chatRoomRepository.findAllByUserId(findUser.getId());
+
+        return chatRooms.stream()
+                        .map(chatRoom -> toDto(findUser, chatRoom))
+                        .toList();
+    }
+
     public ReadParticipatingChatRoomDto readByChatRoomId(final Long chatRoomId, final Long userId) {
         final User findUser = findUser(userId);
         final ChatRoom chatRoom = chatRoomRepository.findById(chatRoomId)

backend/ddang/src/main/java/com/ddang/ddang/chat/application/dto/CreateChatRoomDto.java

@@ -0,0 +1,21 @@
+package com.ddang.ddang.chat.application.dto;
+
+import com.ddang.ddang.auction.domain.Auction;
+import com.ddang.ddang.chat.domain.ChatRoom;
+import com.ddang.ddang.chat.presentation.dto.request.CreateChatRoomRequest;
+import com.ddang.ddang.user.domain.User;
+
+import java.time.LocalDateTime;
+
+public record CreateChatRoomDto(Long auctionId) {
+
+    public static CreateChatRoomDto from(final CreateChatRoomRequest chatRoomRequest) {
+        return new CreateChatRoomDto(chatRoomRequest.auctionId());
+    }
+
+    public ChatRoom toEntity(final Auction auction) {
+        final User buyer = auction.findWinner(LocalDateTime.now());
+
+        return new ChatRoom(auction, buyer);
+    }
+}

backend/ddang/src/main/java/com/ddang/ddang/chat/application/exception/ChatAlreadyExistException.java

@@ -0,0 +1,8 @@
+package com.ddang.ddang.chat.application.exception;
+
+public class ChatAlreadyExistException extends IllegalArgumentException {
+
+    public ChatAlreadyExistException(final String message) {
+        super(message);
+    }
+}

backend/ddang/src/main/java/com/ddang/ddang/chat/application/exception/InvalidAuctionToChatException.java

@@ -0,0 +1,8 @@
+package com.ddang.ddang.chat.application.exception;
+
+public class InvalidAuctionToChatException extends IllegalArgumentException {
+
+    public InvalidAuctionToChatException(final String message) {
+        super(message);
+    }
+}

backend/ddang/src/main/java/com/ddang/ddang/chat/infrastructure/persistence/JpaChatRoomRepository.java

@@ -5,9 +5,12 @@
 import org.springframework.data.jpa.repository.Query;
 
 import java.util.List;
+import java.util.Optional;
 
 public interface JpaChatRoomRepository extends JpaRepository<ChatRoom, Long> {
 
     @Query("select c from ChatRoom c where c.auction.seller.id = :userId or c.buyer.id = :userId")
     List<ChatRoom> findAllByUserId(final Long userId);
+
+    Optional<ChatRoom> findByAuctionId(final Long auctionId);
 }

backend/ddang/src/main/java/com/ddang/ddang/chat/presentation/ChatRoomController.java

@@ -2,10 +2,12 @@
 
 import com.ddang.ddang.chat.application.ChatRoomService;
 import com.ddang.ddang.chat.application.MessageService;
+import com.ddang.ddang.chat.application.dto.CreateChatRoomDto;
 import com.ddang.ddang.chat.application.dto.CreateMessageDto;
 import com.ddang.ddang.chat.application.dto.ReadParticipatingChatRoomDto;
 import com.ddang.ddang.chat.presentation.auth.AuthenticateUser;
 import com.ddang.ddang.chat.presentation.auth.AuthenticateUserInfo;
+import com.ddang.ddang.chat.presentation.dto.request.CreateChatRoomRequest;
 import com.ddang.ddang.chat.presentation.dto.request.CreateMessageRequest;
 import com.ddang.ddang.chat.presentation.dto.response.CreateMessageResponse;
 import com.ddang.ddang.chat.presentation.dto.response.ReadChatRoomResponse;
@@ -34,6 +36,17 @@ public class ChatRoomController {
     private final ChatRoomService chatRoomService;
     private final MessageService messageService;
 
+    @PostMapping
+    public ResponseEntity<Void> create(
+            @AuthenticateUser final AuthenticateUserInfo userInfo,
+            @RequestBody @Valid final CreateChatRoomRequest chatRoomRequest
+    ) {
+        final Long chatRoomId = chatRoomService.create(userInfo.id(), CreateChatRoomDto.from(chatRoomRequest));
+
+        return ResponseEntity.created(URI.create("/chattings/" + chatRoomId))
+                             .build();
+    }
+
     @GetMapping
     public ResponseEntity<ReadChatRoomsResponse> readAllParticipatingChatRooms(
             @AuthenticateUser final AuthenticateUserInfo userInfo

backend/ddang/src/main/java/com/ddang/ddang/chat/presentation/dto/request/CreateChatRoomRequest.java

@@ -0,0 +1,11 @@
+package com.ddang.ddang.chat.presentation.dto.request;
+
+import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.Positive;
+
+public record CreateChatRoomRequest(
+        @NotNull(message = "경매 아이디가 입력되지 않았습니다.")
+        @Positive(message = "경매 아이디는 양수입니다.")
+        Long auctionId
+) {
+}

backend/ddang/src/main/java/com/ddang/ddang/exception/GlobalExceptionHandler.java

@@ -3,9 +3,12 @@
 import com.ddang.ddang.auction.application.exception.AuctionNotFoundException;
 import com.ddang.ddang.auction.application.exception.UserNotAuthorizationException;
 import com.ddang.ddang.auction.domain.exception.InvalidPriceValueException;
+import com.ddang.ddang.auction.domain.exception.WinnerNotFoundException;
 import com.ddang.ddang.bid.application.exception.InvalidBidException;
 import com.ddang.ddang.category.application.exception.CategoryNotFoundException;
+import com.ddang.ddang.chat.application.exception.ChatAlreadyExistException;
 import com.ddang.ddang.chat.application.exception.ChatRoomNotFoundException;
+import com.ddang.ddang.chat.application.exception.InvalidAuctionToChatException;
 import com.ddang.ddang.chat.application.exception.UserNotAccessibleException;
 import com.ddang.ddang.chat.application.exception.UserNotFoundException;
 import com.ddang.ddang.exception.dto.ExceptionResponse;
@@ -175,6 +178,36 @@ public ResponseEntity<ExceptionResponse> handleUserNotAccessibleException(
                              .body(new ExceptionResponse(ex.getMessage()));
     }
 
+    @ExceptionHandler(WinnerNotFoundException.class)
+    public ResponseEntity<ExceptionResponse> handleWinnerNotFoundException(
+            final WinnerNotFoundException ex
+    ) {
+        logger.warn(String.format(EXCEPTION_FORMAT, WinnerNotFoundException.class), ex);
+
+        return ResponseEntity.status(HttpStatus.NOT_FOUND)
+                             .body(new ExceptionResponse(ex.getMessage()));
+    }
+
+    @ExceptionHandler(InvalidAuctionToChatException.class)
+    public ResponseEntity<ExceptionResponse> handleInvalidAuctionToChatException(
+            final InvalidAuctionToChatException ex
+    ) {
+        logger.warn(String.format(EXCEPTION_FORMAT, InvalidAuctionToChatException.class), ex);
+
+        return ResponseEntity.status(HttpStatus.BAD_REQUEST)
+                             .body(new ExceptionResponse(ex.getMessage()));
+    }
+
+    @ExceptionHandler(ChatAlreadyExistException.class)
+    public ResponseEntity<ExceptionResponse> handleChatAlreadyExistException(
+            final ChatAlreadyExistException ex
+    ) {
+        logger.warn(String.format(EXCEPTION_FORMAT, ChatAlreadyExistException.class), ex);
+
+        return ResponseEntity.status(HttpStatus.BAD_REQUEST)
+                             .body(new ExceptionResponse(ex.getMessage()));
+    }
+
     @Override
     protected ResponseEntity<Object> handleMethodArgumentNotValid(
             final MethodArgumentNotValidException ex,