feat: 가장 많이 예약된 테마 ID 조회 API 추가

src/main/kotlin/roomescape/reservation/business/ReservationService.kt

@@ -9,6 +9,7 @@ import org.springframework.transaction.annotation.Transactional
 import roomescape.common.config.next
 import roomescape.common.dto.CurrentUserContext
 import roomescape.common.dto.PrincipalType
+import roomescape.common.util.DateUtils
 import roomescape.member.business.UserService
 import roomescape.member.web.UserContactRetrieveResponse
 import roomescape.payment.business.PaymentService
@@ -23,6 +24,7 @@ import roomescape.schedule.web.ScheduleSummaryResponse
 import roomescape.schedule.web.ScheduleUpdateRequest
 import roomescape.theme.business.ThemeService
 import roomescape.theme.web.ThemeInfoRetrieveResponse
+import java.time.LocalDate
 import java.time.LocalDateTime
 
 private val log: KLogger = KotlinLogging.logger {}
@@ -126,6 +128,23 @@ class ReservationService(
         }
     }
 
+    @Transactional(readOnly = true)
+    fun findMostReservedThemeIds(count: Int): MostReservedThemeIdListResponse {
+        log.info { "[ReservationService.findMostReservedThemeIds] 인기 테마 조회 시작: count=$count" }
+        val previousWeekSunday = DateUtils.getSundayOfPreviousWeek(LocalDate.now())
+        val previousWeekSaturday = previousWeekSunday.plusDays(6)
+
+        val themeIds: List<Long> = reservationRepository.findMostReservedThemeIds(
+            dateFrom = previousWeekSunday,
+            dateTo = previousWeekSaturday,
+            count = count
+        )
+
+        return MostReservedThemeIdListResponse(themeIds = themeIds).also {
+            log.info { "[ReservationService.findMostReservedThemeIds] 인기 테마 조회 완료: count=${it.themeIds.size}" }
+        }
+    }
+
     private fun findOrThrow(id: Long): ReservationEntity {
         log.info { "[ReservationService.findOrThrow] 예약 조회 시작: reservationId=${id}" }
 

src/main/kotlin/roomescape/reservation/docs/ReservationAPI.kt

@@ -7,8 +7,10 @@ import jakarta.validation.Valid
 import org.springframework.http.ResponseEntity
 import org.springframework.web.bind.annotation.PathVariable
 import org.springframework.web.bind.annotation.RequestBody
+import org.springframework.web.bind.annotation.RequestParam
 import roomescape.auth.web.support.Authenticated
 import roomescape.auth.web.support.CurrentUser
+import roomescape.auth.web.support.Public
 import roomescape.auth.web.support.UserOnly
 import roomescape.common.dto.CurrentUserContext
 import roomescape.common.dto.response.CommonApiResponse
@@ -16,6 +18,13 @@ import roomescape.reservation.web.*
 
 interface ReservationAPI {
 
+    @Public
+    @Operation(summary = "결제 대기 예약 저장", tags = ["로그인이 필요한 API"])
+    @ApiResponses(ApiResponse(responseCode = "200", description = "성공", useReturnTypeSchema = true))
+    fun findMostReservedThemeIds(
+        @RequestParam count: Int
+    ): ResponseEntity<CommonApiResponse<MostReservedThemeIdListResponse>>
+
     @UserOnly
     @Operation(summary = "결제 대기 예약 저장", tags = ["로그인이 필요한 API"])
     @ApiResponses(ApiResponse(responseCode = "200", description = "성공", useReturnTypeSchema = true))

src/main/kotlin/roomescape/reservation/infrastructure/persistence/ReservationRepository.kt

@@ -1,8 +1,27 @@
 package roomescape.reservation.infrastructure.persistence
 
 import org.springframework.data.jpa.repository.JpaRepository
+import org.springframework.data.jpa.repository.Query
+import org.springframework.data.repository.query.Param
+import java.time.LocalDate
 
 interface ReservationRepository : JpaRepository<ReservationEntity, Long> {
 
     fun findAllByUserId(userId: Long): List<ReservationEntity>
+
+    @Query("""
+        SELECT s.themeId 
+        FROM ReservationEntity r
+        JOIN ScheduleEntity s ON s._id = r.scheduleId
+        WHERE r.status = roomescape.reservation.infrastructure.persistence.ReservationStatus.CONFIRMED
+        AND s.date BETWEEN :dateFrom AND :dateTo
+        GROUP BY s.themeId
+        ORDER BY count(r) DESC 
+        LIMIT :count
+    """)
+    fun findMostReservedThemeIds(
+        @Param("dateFrom") dateFrom: LocalDate,
+        @Param("dateTo") dateTo: LocalDate,
+        @Param("count") count: Int
+    ): List<Long>
 }

src/main/kotlin/roomescape/reservation/web/ReservationController.kt

@@ -14,6 +14,15 @@ class ReservationController(
     private val reservationService: ReservationService
 ) : ReservationAPI {
 
+    @GetMapping("/reservations/popular-themes")
+    override fun findMostReservedThemeIds(
+        @RequestParam count: Int
+    ): ResponseEntity<CommonApiResponse<MostReservedThemeIdListResponse>> {
+        val response = reservationService.findMostReservedThemeIds(count)
+
+        return ResponseEntity.ok(CommonApiResponse(response))
+    }
+
     @PostMapping("/reservations/pending")
     override fun createPendingReservation(
         @CurrentUser user: CurrentUserContext,

src/main/kotlin/roomescape/reservation/web/ReservationDto.kt

@@ -68,3 +68,7 @@ fun ReservationEntity.toReservationDetailRetrieveResponse(
 data class ReservationCancelRequest(
     val cancelReason: String
 )
+
+data class MostReservedThemeIdListResponse(
+    val themeIds: List<Long>
+)