[BE-Feat] 논의 탈퇴 기능구현

backend/src/main/java/endolphin/backend/domain/discussion/DiscussionParticipantRepository.java

@@ -4,11 +4,14 @@
 import endolphin.backend.domain.discussion.entity.DiscussionParticipant;
 import endolphin.backend.domain.user.dto.UserIdNameDto;
 import endolphin.backend.domain.user.entity.User;
+import jakarta.persistence.LockModeType;
 import java.util.List;
 import java.util.Optional;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Lock;
+import org.springframework.data.jpa.repository.Modifying;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
@@ -116,4 +119,21 @@ Page<Discussion> findFinishedDiscussions(@Param("userId") Long userId,
         "WHERE d.discussionStatus = 'ONGOING' " +
         "AND dp.user.id IN :userIds")
     List<Object[]> findOffsetsByUserIds(@Param("userIds") List<Long> userIds);
+
+    @Modifying
+    @Query("DELETE "
+        + "FROM DiscussionParticipant dp "
+        + "WHERE dp.discussion.id = :discussionId "
+        + "AND dp.user.id = :userId")
+    void deleteByDiscussionIdAndUserId(
+        @Param("discussionId") Long discussionId,
+        @Param("userId") Long userId);
+
+    @Query("SELECT dp.userOffset "
+        + "FROM DiscussionParticipant dp "
+        + "WHERE dp.discussion.id = :discussionId "
+        + "ORDER BY dp.userOffset ASC")
+    List<Long> findOffsetsByDiscussionId(
+        @Param("discussionId") Long discussionId
+    );
 }

backend/src/main/java/endolphin/backend/domain/discussion/DiscussionParticipantService.java

@@ -15,6 +15,7 @@
 import endolphin.backend.global.dto.ListResponse;
 import endolphin.backend.global.error.exception.ApiException;
 import endolphin.backend.global.error.exception.ErrorCode;
+import endolphin.backend.global.redis.DiscussionBitmapService;
 import endolphin.backend.global.util.TimeUtil;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -34,37 +35,34 @@
 @Transactional
 public class DiscussionParticipantService {
 
+    private static final int MAX_PARTICIPANT = 15;
+
     private final DiscussionParticipantRepository discussionParticipantRepository;
     private final UserService userService;
-    private static final int MAX_PARTICIPANT = 15;
     private final SharedEventService sharedEventService;
 
     public void addDiscussionParticipant(Discussion discussion, User user) {
-        Long offset = discussionParticipantRepository.findMaxOffsetByDiscussionId(
+        List<Long> offsets = discussionParticipantRepository.findOffsetsByDiscussionId(
             discussion.getId());
 
-        offset += 1;
-
-        if (offset >= MAX_PARTICIPANT) {
+        if (offsets.size() >= MAX_PARTICIPANT) {
             throw new ApiException(ErrorCode.DISCUSSION_PARTICIPANT_EXCEED_LIMIT);
         }
 
-        DiscussionParticipant participant;
-        if (offset == 0) {
-            participant = DiscussionParticipant.builder()
-                .discussion(discussion)
-                .user(user)
-                .isHost(true)
-                .userOffset(offset)
-                .build();
-        } else {
-            participant = DiscussionParticipant.builder()
-                .discussion(discussion)
-                .user(user)
-                .isHost(false)
-                .userOffset(offset)
-                .build();
+        long offset = 0L;
+        for (; offset < offsets.size(); ++offset) {
+            if (offsets.get((int) offset) != offset)
+                break;
         }
+
+        boolean isHost = (offset == 0);
+        DiscussionParticipant participant = DiscussionParticipant.builder()
+            .discussion(discussion)
+            .user(user)
+            .isHost(isHost)
+            .userOffset(offset)
+            .build();
+
         discussionParticipantRepository.save(participant);
     }
 
@@ -320,4 +318,8 @@ public Map<Long, Map<Discussion, Long>> getOngoingDiscussionOffsetsByUserIds(
             )
         );
     }
+
+    public void deleteDiscussionParticipant(Long discussionId, Long userId) {
+        discussionParticipantRepository.deleteByDiscussionIdAndUserId(discussionId, userId);
+    }
 }

backend/src/main/java/endolphin/backend/domain/discussion/DiscussionRepository.java

@@ -2,13 +2,22 @@
 
 import endolphin.backend.domain.discussion.entity.Discussion;
 import endolphin.backend.domain.discussion.enums.DiscussionStatus;
+import io.lettuce.core.dynamic.annotation.Param;
+import jakarta.persistence.LockModeType;
 import java.util.List;
+import java.util.Optional;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Lock;
+import org.springframework.data.jpa.repository.Query;
 import org.springframework.stereotype.Repository;
 
 @Repository
 public interface DiscussionRepository extends JpaRepository<Discussion, Long> {
 
     List<Discussion> findByDiscussionStatusNot(DiscussionStatus discussionStatus);
 
+    @Lock(LockModeType.PESSIMISTIC_WRITE)
+    @Query("SELECT d FROM Discussion d WHERE d.id = :discussionId")
+    Optional<Discussion> findByIdForUpdate(@Param("discussionId") Long discussionId);
+
 }

backend/src/main/java/endolphin/backend/domain/discussion/DiscussionService.java

@@ -278,7 +278,8 @@ public Discussion getDiscussionById(Long discussionId) {
     }
 
     public JoinDiscussionResponse joinDiscussion(Long discussionId, JoinDiscussionRequest request) {
-        Discussion discussion = getDiscussionById(discussionId);
+        Discussion discussion = discussionRepository.findByIdForUpdate(discussionId)
+            .orElseThrow(() -> new ApiException(ErrorCode.DISCUSSION_NOT_FOUND));
 
         if (discussion.getDiscussionStatus() != DiscussionStatus.ONGOING) {
             throw new ApiException(ErrorCode.DISCUSSION_NOT_ONGOING);
@@ -395,6 +396,17 @@ public DiscussionResponse updateDiscussion(Long discussionId, UpdateDiscussionRe
         );
     }
 
+    public void exitDiscussion(Long discussionId, Long userId) {
+        Discussion discussion = discussionRepository.findByIdForUpdate(discussionId)
+            .orElseThrow(() -> new ApiException(ErrorCode.DISCUSSION_NOT_FOUND));
+
+        Long offset = discussionParticipantService.getDiscussionParticipantOffset(discussionId, userId);
+
+        discussionBitmapService.deleteUsersFromDiscussion(discussionId, offset);
+
+        discussionParticipantService.deleteDiscussionParticipant(discussionId, userId);
+    }
+
     private boolean isTimeChanged(Discussion discussion, UpdateDiscussionRequest request) {
         return !discussion.getDateRangeStart().equals(request.dateRangeStart())
             || !discussion.getDateRangeEnd().equals(request.dateRangeEnd())

backend/src/main/java/endolphin/backend/global/redis/DiscussionBitmapService.java

@@ -1,17 +1,26 @@
 package endolphin.backend.global.redis;
 
 import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
 import lombok.RequiredArgsConstructor;
+import org.springframework.dao.DataAccessException;
 import org.springframework.data.redis.RedisSystemException;
+import org.springframework.data.redis.connection.RedisCommands;
 import org.springframework.data.redis.connection.RedisCommandsProvider;
 import org.springframework.data.redis.connection.RedisConnection;
 import org.springframework.data.redis.connection.RedisKeyCommands;
+import org.springframework.data.redis.connection.RedisSetCommands;
 import org.springframework.data.redis.core.Cursor;
+import org.springframework.data.redis.core.RedisCallback;
+import org.springframework.data.redis.core.RedisCommand;
+import org.springframework.data.redis.core.RedisOperations;
 import org.springframework.data.redis.core.RedisTemplate;
 import org.springframework.data.redis.core.ScanOptions;
+import org.springframework.data.redis.core.SessionCallback;
 import org.springframework.scheduling.annotation.Async;
 import org.springframework.stereotype.Service;
 
@@ -168,4 +177,36 @@ public Map<Long, byte[]> getDataOfDiscussionId(Long discussionId) {
             return map;
         });
     }
+
+    public void deleteUsersFromDiscussion(Long discussionId, long bitOffset) {
+        String pattern = discussionId + ":*";
+        ScanOptions scanOptions = ScanOptions.scanOptions().match(pattern).count(1000).build();
+
+        List<byte[]> keys = redisTemplate.execute((RedisConnection connection) -> {
+            List<byte[]> k = new ArrayList<>();
+            RedisKeyCommands keyCommands = connection.keyCommands();
+            try (Cursor<byte[]> cursor = keyCommands.scan(scanOptions)) {
+                while (cursor.hasNext()) {
+                    k.add(cursor.next());
+                }
+            }
+            return k;
+        });
+
+        if (keys == null || keys.isEmpty()) {
+            return;
+        }
+
+        redisTemplate.executePipelined(new RedisCallback<Object>() {
+
+            @Override
+            public Object doInRedis(RedisConnection connection) throws DataAccessException {
+                RedisCommands redisCommands = connection.commands();
+                for (byte[] key : keys) {
+                    redisCommands.setBit(key, bitOffset, false);
+                }
+                return null;
+            }
+        });
+    }
 }

backend/src/test/java/endolphin/backend/domain/discussion/DiscussionParticipantServiceTest.java

@@ -25,6 +25,7 @@
 import java.time.LocalDate;
 import java.time.LocalDateTime;
 import java.time.LocalTime;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
@@ -79,8 +80,8 @@ void addDiscussionParticipant_ShouldAddSuccessfully() {
             .picture("profile.jpg")
             .build();
 
-        given(discussionParticipantRepository.findMaxOffsetByDiscussionId(discussion.getId()))
-            .willReturn(0L);
+        given(discussionParticipantRepository.findOffsetsByDiscussionId(discussion.getId()))
+            .willReturn(new ArrayList<>());
 
         // When
         discussionParticipantService.addDiscussionParticipant(discussion, user);
@@ -109,8 +110,8 @@ void addDiscussionParticipant_ShouldThrowExceptionWhenExceedLimit() {
             .picture("profile.jpg")
             .build();
 
-        given(discussionParticipantRepository.findMaxOffsetByDiscussionId(discussion.getId()))
-            .willReturn(15L); // 최대 인원 초과 상황
+        given(discussionParticipantRepository.findOffsetsByDiscussionId(discussion.getId()))
+            .willReturn(List.of(0L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L, 14L)); // 최대 인원 초과 상황
 
         // When & Then
         ApiException exception = assertThrows(ApiException.class, () -> {

backend/src/test/java/endolphin/backend/domain/discussion/DiscussionServiceTest.java

@@ -600,7 +600,7 @@ public void joinDiscussion_withCorrectPassword_returnsTrue() {
         User currentUser = new User();
         ReflectionTestUtils.setField(currentUser, "id", 1L);
 
-        when(discussionRepository.findById(discussionId)).thenReturn(Optional.of(discussion));
+        when(discussionRepository.findByIdForUpdate(discussionId)).thenReturn(Optional.of(discussion));
         when(userService.getCurrentUser()).thenReturn(currentUser);
         when(passwordCountService.tryEnter(currentUser.getId(), discussion, correctPassword)).thenReturn(0);
 
@@ -629,7 +629,7 @@ public void joinDiscussion_withIncorrectPassword_returnsFalse() {
         User currentUser = new User();
         ReflectionTestUtils.setField(currentUser, "id", 1L);
 
-        when(discussionRepository.findById(discussionId)).thenReturn(Optional.of(discussion));
+        when(discussionRepository.findByIdForUpdate(discussionId)).thenReturn(Optional.of(discussion));
         when(userService.getCurrentUser()).thenReturn(currentUser);
         when(passwordCountService.tryEnter(currentUser.getId(), discussion, incorrectPassword)).thenReturn(1);
 
@@ -656,7 +656,7 @@ public void joinDiscussion_withNullPassword_throwsApiException() {
         User currentUser = new User();
         ReflectionTestUtils.setField(currentUser, "id", 1L);
 
-        when(discussionRepository.findById(discussionId)).thenReturn(Optional.of(discussion));
+        when(discussionRepository.findByIdForUpdate(discussionId)).thenReturn(Optional.of(discussion));
         when(userService.getCurrentUser()).thenReturn(currentUser);
 
         // 비밀번호가 null인 경우, passwordCountService.tryEnter가 예외를 던지도록 모킹
@@ -675,7 +675,7 @@ public void joinDiscussion_withNullPassword_throwsApiException() {
     public void joinDiscussion_withInvalidDiscussionId_throwsApiException() {
         // Given
         Long discussionId = 999L;
-        when(discussionRepository.findById(discussionId)).thenReturn(Optional.empty());
+        when(discussionRepository.findByIdForUpdate(discussionId)).thenReturn(Optional.empty());
 
         // When & Then
         assertThatThrownBy(() ->

backend/src/test/java/endolphin/backend/global/redis/DiscussionBitmapServiceTest.java

@@ -132,4 +132,28 @@ public void testGetDataOfDiscussionId() {
         BitSet bs = BitSet.valueOf(data);
         assertThat(bs.get(5)).as("Offset 5의 비트는 true여야 합니다").isTrue();
     }
+
+    @Test
+    @DisplayName("참여자 비트 전체 삭제 테스트")
+    public void testSetUserBitsFalse() {
+        // given
+        Long discussionId = 100L;
+        long bitOffset = 3L;
+        long minuteKey = TimeUtil.convertToMinute(LocalDateTime.now());
+        bitmapService.initializeBitmap(discussionId, minuteKey);
+        bitmapService.initializeBitmap(discussionId, minuteKey + 30);
+
+        bitmapService.setBitValue(discussionId, minuteKey, bitOffset, true);
+        bitmapService.setBitValue(discussionId, minuteKey + 30, bitOffset, true);
+
+        // when
+        bitmapService.deleteUsersFromDiscussion(discussionId, bitOffset);
+
+        // then
+        boolean data = bitmapService.getBitValue(discussionId, minuteKey, bitOffset);
+        assertThat(data).isFalse();
+
+        data = bitmapService.getBitValue(discussionId, minuteKey + 30, bitOffset);
+        assertThat(data).isFalse();
+    }
 }