feat: No offset 방식의 채팅 조회

src/main/java/com/palettee/chat/repository/ChatCustomRepository.java

@@ -0,0 +1,9 @@
+package com.palettee.chat.repository;
+
+import com.palettee.chat.controller.dto.response.ChatCustomResponse;
+
+import java.time.LocalDateTime;
+
+public interface ChatCustomRepository {
+    ChatCustomResponse findChatNoOffset(Long chatRoomId, int size, LocalDateTime lastTimeStamp);
+}

src/main/java/com/palettee/chat/repository/ChatCustomRepositoryImpl.java

@@ -0,0 +1,52 @@
+package com.palettee.chat.repository;
+
+import com.palettee.chat.controller.dto.response.ChatCustomResponse;
+import com.palettee.chat.domain.Chat;
+import com.querydsl.jpa.impl.JPAQueryFactory;
+import org.springframework.stereotype.Repository;
+
+import java.time.LocalDateTime;
+import java.util.List;
+
+import static com.palettee.chat.domain.QChat.*;
+import static com.palettee.chat.domain.QChatImage.*;
+import static com.palettee.chat_room.domain.QChatRoom.*;
+import static com.palettee.user.domain.QUser.*;
+
+@Repository
+public class ChatCustomRepositoryImpl implements ChatCustomRepository{
+    private final JPAQueryFactory queryFactory;
+
+    public ChatCustomRepositoryImpl(JPAQueryFactory queryFactory) {
+        this.queryFactory = queryFactory;
+    }
+
+    @Override
+    public ChatCustomResponse findChatNoOffset(Long chatRoomId, int size, LocalDateTime sendAt) {
+        List<Chat> chats = queryFactory
+                .selectFrom(chat)
+                .where(
+                        chat.chatRoom.id.eq(chatRoomId),
+                        sendAt != null ?
+                                chat.sendAt.lt(sendAt) : null
+                )
+                .leftJoin(chat.chatImages, chatImage).fetchJoin()
+                .leftJoin(chat.user, user).fetchJoin()
+                .leftJoin(chat.chatRoom, chatRoom).fetchJoin()
+                .orderBy(chat.sendAt.desc())
+                .limit(size + 1)
+                .fetch();
+
+        boolean hasNext = chats.size() > size;
+
+        LocalDateTime lastSendAt = null;
+        if(hasNext) {
+            if(size != 0) {
+                lastSendAt = chats.get(size-1).getSendAt();
+            }
+            chats = chats.subList(0, size);
+        }
+
+        return ChatCustomResponse.toResponseFromEntity(chats, hasNext, lastSendAt);
+    }
+}