Feat/74 회원 탈퇴 구현

src/main/kotlin/com/wafflestudio/spring2025/common/email/service/EmailService.kt

@@ -109,7 +109,7 @@ class EmailService(
         val endsAt: Instant?,
         val location: String?,
         val description: String?,
-        val hostEmail: String,
+        val hostEmail: String?,
     )
 
     data class DemotionEmailData(
@@ -240,7 +240,7 @@ class EmailService(
                 .replace("{eventTitle}", formatEventTitle(data.eventTitle))
                 .replace("{eventDateRange}", formatEventDateRange(data.startsAt, data.endsAt, "-"))
                 .replace("{location}", formatLocation(data.location))
-                .replace("{hostEmail}", data.hostEmail)
+                .replace("{hostEmail}", data.hostEmail ?: "탈퇴유저")
                 .replace("{description}", formatDescription(data.description))
 
         sendHtmlEmail(

src/main/kotlin/com/wafflestudio/spring2025/domain/event/dto/core/EventDto.kt

@@ -13,7 +13,7 @@ data class EventDto(
     val waitlistEnabled: Boolean,
     val registrationStartsAt: Long?,
     val registrationEndsAt: Long,
-    val createdBy: Long,
+    val createdBy: Long?,
     val createdAt: Long?,
     val updatedAt: Long?,
 ) {

src/main/kotlin/com/wafflestudio/spring2025/domain/event/dto/response/EventDetailResponse.kt

@@ -26,7 +26,7 @@ data class EventInfo(
 
 data class CreatorInfo(
     val name: String,
-    val email: String,
+    val email: String?,
     val profileImage: String?,
 )
 

src/main/kotlin/com/wafflestudio/spring2025/domain/event/model/Event.kt

@@ -28,7 +28,7 @@ class Event(
     @Column("registration_ends_at")
     var registrationEndsAt: Instant,
     @Column("created_by")
-    var createdBy: Long,
+    var createdBy: Long?,
     @CreatedDate
     @Column("created_at")
     var createdAt: Instant? = null,

src/main/kotlin/com/wafflestudio/spring2025/domain/event/repository/EventRepository.kt

@@ -8,6 +8,8 @@ import java.time.Instant
 interface EventRepository : ListCrudRepository<Event, Long> {
     fun findByPublicId(publicId: String): Event?
 
+    fun findByCreatedBy(createdBy: Long): List<Event>
+
     fun findByCreatedByAndCreatedAtIsNotNullOrderByCreatedAtDesc(
         createdBy: Long,
         pageable: Pageable,

src/main/kotlin/com/wafflestudio/spring2025/domain/event/service/EventService.kt

@@ -99,7 +99,7 @@ class EventService(
 
         val userIdsToFetch = listOfNotNull(event.createdBy, requesterId).distinct()
         val usersById = userRepository.findAllById(userIdsToFetch).associateBy { it.id!! }
-        val creatorUser = usersById[event.createdBy] ?: throw EventNotFoundException()
+        val creatorUser = event.createdBy?.let { usersById[it] }
 
         val myReg =
             if (requesterId == null) {
@@ -230,9 +230,9 @@ class EventService(
                 ),
             creator =
                 CreatorInfo(
-                    name = creatorUser.name,
-                    email = creatorUser.email,
-                    profileImage = creatorUser.profileImage?.let { imageService.presignedGetUrl(it) },
+                    name = creatorUser?.name ?: "탈퇴유저",
+                    email = creatorUser?.email,
+                    profileImage = creatorUser?.profileImage?.let { imageService.presignedGetUrl(it) },
                 ),
             viewer = viewer,
             capabilities = capabilities,
@@ -391,7 +391,7 @@ class EventService(
             )
 
         // 이메일 데이터 구성 (삭제 전에 user 정보 조회)
-        val hostUser = userRepository.findById(event.createdBy).orElse(null)
+        val hostUser = event.createdBy?.let { userRepository.findById(it).orElse(null) }
         val userIds = registrationsToNotify.mapNotNull { it.userId }.distinct()
         val usersById = userRepository.findAllById(userIds).associateBy { it.id!! }
 
@@ -408,7 +408,7 @@ class EventService(
                     endsAt = event.endsAt,
                     location = event.location,
                     description = event.description,
-                    hostEmail = hostUser?.email ?: "",
+                    hostEmail = hostUser?.email,
                 )
             }
 
@@ -423,6 +423,54 @@ class EventService(
         }
     }
 
+    /**
+     * 유저 탈퇴 시 호출. 시작 전(now < startsAt) 이벤트들을 일괄 삭제하고
+     * 참여자/대기자에게 익명화된 주최자 정보로 취소 메일을 발송한다.
+     * 소유권 체크는 호출 측에서 보장.
+     */
+    @Transactional
+    fun deleteEventsForWithdrawal(events: List<Event>) {
+        if (events.isEmpty()) return
+        val eventIds = events.map { it.id!! }.sorted()
+
+        // 락 획득 (ID 오름차순으로 deadlock 방지)
+        eventIds.forEach { eventLockRepository.lockById(it) }
+
+        val eventsById = events.associateBy { it.id!! }
+        val registrations =
+            registrationRepository.findByEventIdInAndStatusIn(
+                eventIds = eventIds,
+                statuses = listOf(RegistrationStatus.CONFIRMED, RegistrationStatus.WAITLISTED),
+            )
+        val userIds = registrations.mapNotNull { it.userId }.distinct()
+        val usersById = userRepository.findAllById(userIds).associateBy { it.id!! }
+
+        val emailDataList =
+            registrations.mapNotNull { reg ->
+                val event = eventsById[reg.eventId] ?: return@mapNotNull null
+                val user = reg.userId?.let { usersById[it] }
+                val toEmail = user?.email ?: reg.guestEmail
+                if (toEmail.isNullOrBlank()) return@mapNotNull null
+                EmailService.EventCancellationEmailData(
+                    toEmail = toEmail,
+                    name = user?.name ?: reg.guestName ?: "참여자",
+                    eventTitle = event.title,
+                    startsAt = event.startsAt,
+                    endsAt = event.endsAt,
+                    location = event.location,
+                    description = event.description,
+                    hostEmail = null,
+                )
+            }
+
+        registrationRepository.deleteByEventIdIn(eventIds)
+        eventRepository.deleteAllById(eventIds)
+
+        afterCommit {
+            emailDataList.forEach { emailService.sendEventCancellationEmail(it) }
+        }
+    }
+
     private fun getEventByPublicId(publicId: String): Event =
         eventRepository.findByPublicId(publicId)
             ?: throw EventNotFoundException()

src/main/kotlin/com/wafflestudio/spring2025/domain/registration/repository/RegistrationRepository.kt

@@ -14,6 +14,18 @@ interface RegistrationRepository :
 
     fun deleteByEventId(eventId: Long)
 
+    fun deleteByEventIdIn(eventIds: Collection<Long>)
+
+    fun findByUserIdAndStatusIn(
+        userId: Long,
+        statuses: Collection<RegistrationStatus>,
+    ): List<Registration>
+
+    fun findByEventIdInAndStatusIn(
+        eventIds: Collection<Long>,
+        statuses: Collection<RegistrationStatus>,
+    ): List<Registration>
+
     fun findByRegistrationPublicId(registrationPublicId: String): Registration?
 
     @Query(

src/main/kotlin/com/wafflestudio/spring2025/domain/registration/service/RegistrationService.kt

@@ -281,6 +281,35 @@ RegistrationService(
         }
     }
 
+    /**
+     * 유저 탈퇴 시 호출. 신청기간/소유권 체크 없이 다수 등록을 일괄 삭제하고
+     * 확정 등록이 있던 이벤트에 대해서만 대기자 승격을 트리거한다.
+     * 탈퇴자에게 취소 메일은 발송하지 않는다. 대기자 승격 메일은 reconcileWaitlist 내부에서 처리됨.
+     */
+    @Transactional
+    fun cancelRegistrationsForWithdrawal(registrations: List<Registration>) {
+        if (registrations.isEmpty()) return
+
+        val byEventId = registrations.groupBy { it.eventId }
+        val eventIds = byEventId.keys.sorted()
+
+        // 1. 이벤트 락 (ID 오름차순으로 deadlock 방지)
+        eventIds.forEach { eventLockRepository.lockById(it) }
+
+        // 2. CONFIRMED 등록이 포함된 이벤트만 대기자 승격 필요
+        val eventsToReconcile =
+            byEventId
+                .filterValues { regs -> regs.any { it.status == RegistrationStatus.CONFIRMED } }
+                .keys
+                .sorted()
+
+        // 3. 배치 삭제
+        registrationRepository.deleteAllById(registrations.map { it.id!! })
+
+        // 4. 필요한 이벤트만 승격
+        eventsToReconcile.forEach { reconcileWaitlist(it) }
+    }
+
     private fun toResponseStatus(status: RegistrationStatus): RegistrationStatusResponse =
         when (status) {
             RegistrationStatus.HOST -> RegistrationStatusResponse.CONFIRMED

src/main/kotlin/com/wafflestudio/spring2025/domain/user/controller/UserController.kt

@@ -8,6 +8,7 @@ import com.wafflestudio.spring2025.domain.user.dto.PatchMeResponse
 import com.wafflestudio.spring2025.domain.user.model.User
 import com.wafflestudio.spring2025.domain.user.service.UserService
 import org.springframework.http.ResponseEntity
+import org.springframework.web.bind.annotation.DeleteMapping
 import org.springframework.web.bind.annotation.GetMapping
 import org.springframework.web.bind.annotation.PatchMapping
 import org.springframework.web.bind.annotation.RequestBody
@@ -41,4 +42,12 @@ class UserController(
         )
         return ResponseEntity.ok(userService.me(user))
     }
+
+    @DeleteMapping("/me")
+    fun deleteMe(
+        @LoggedInUser user: User,
+    ): ResponseEntity<Void> {
+        userService.deleteMe(user = user)
+        return ResponseEntity.noContent().build()
+    }
 }

src/main/kotlin/com/wafflestudio/spring2025/domain/user/exception/UserErrorCode.kt

@@ -18,4 +18,9 @@ enum class UserErrorCode(
         title = "이메일은 변경할 수 없습니다.",
         message = "이메일 주소는 변경이 불가능합니다.",
     ),
+    NO_SUCH_USER(
+        httpStatusCode = HttpStatus.NOT_FOUND,
+        title = "존재하지 않는 회원입니다.",
+        message = "이미 탈퇴 처리가 되었거나\n존재하지 않는 회원입니다.",
+    ),
 }

src/main/kotlin/com/wafflestudio/spring2025/domain/user/identity/repository/UserIdentityRepository.kt

@@ -12,4 +12,6 @@ interface UserIdentityRepository : ListCrudRepository<UserIdentity, Long> {
     fun findByUserId(userId: Long): List<UserIdentity>
 
     fun findByProviderUserId(providerId: String): List<UserIdentity>
+
+    fun deleteByUserId(userId: Long)
 }