feat(content-ranking): 스냅샷 기반 랭킹 조회를 추가한다

src/main/kotlin/kr/co/vividnext/sodalive/v2/content/ranking/application/AudioRankingQueryService.kt

@@ -1,17 +1,80 @@
 package kr.co.vividnext.sodalive.v2.content.ranking.application
 
 import kr.co.vividnext.sodalive.member.Member
+import kr.co.vividnext.sodalive.member.contentpreference.MemberContentPreferenceService
 import kr.co.vividnext.sodalive.v2.content.ranking.domain.AudioRanking
+import kr.co.vividnext.sodalive.v2.content.ranking.domain.AudioRankingItem
 import kr.co.vividnext.sodalive.v2.content.ranking.domain.AudioRankingType
+import kr.co.vividnext.sodalive.v2.content.ranking.port.out.AudioRankingSnapshotPort
+import kr.co.vividnext.sodalive.v2.content.ranking.port.out.AudioRankingSnapshotRecord
 import org.springframework.stereotype.Service
+import org.springframework.transaction.annotation.Transactional
+import java.time.ZoneOffset
+import java.time.ZonedDateTime
 
 @Service
-class AudioRankingQueryService {
+class AudioRankingQueryService(
+    private val snapshotPort: AudioRankingSnapshotPort,
+    private val memberContentPreferenceService: MemberContentPreferenceService,
+    private val nowProvider: () -> ZonedDateTime = { ZonedDateTime.now() }
+) {
+    @Transactional(readOnly = true)
     fun getRankings(type: AudioRankingType, member: Member?): AudioRanking {
+        val nowUtc = nowProvider().withZoneSameInstant(ZoneOffset.UTC).toLocalDateTime()
+        val latestSnapshots = snapshotPort.findLatestVisibleSnapshots(type, nowUtc)
+        if (latestSnapshots.isEmpty()) {
+            return AudioRanking(showRankChange = false, type = type, items = emptyList())
+        }
+        val canViewAdultContent = canViewAdultContent(member)
+        val latestVisibleSnapshots = latestSnapshots.visibleTo(canViewAdultContent).take(ITEM_LIMIT)
+
+        val previousSnapshots = snapshotPort.findPreviousVisibleSnapshots(
+            rankingType = type,
+            currentAggregationStartAtUtc = latestSnapshots.first().aggregationStartAtUtc,
+            nowUtc = nowUtc
+        )
+        val previousRankByContentId = previousSnapshots.visibleTo(canViewAdultContent)
+            .take(ITEM_LIMIT)
+            .mapIndexed { index, snapshot -> snapshot.contentId to index + 1 }
+            .toMap()
+        val showRankChange = previousRankByContentId.isNotEmpty()
+
         return AudioRanking(
-            showRankChange = false,
+            showRankChange = showRankChange,
             type = type,
-            items = emptyList()
+            items = latestVisibleSnapshots.mapIndexed { index, snapshot ->
+                snapshot.toItem(index + 1, showRankChange, previousRankByContentId)
+            }
         )
     }
+
+    private fun canViewAdultContent(member: Member?): Boolean {
+        if (member == null) return false
+        return memberContentPreferenceService.canViewAdultContent(member)
+    }
+
+    private fun List<AudioRankingSnapshotRecord>.visibleTo(canViewAdultContent: Boolean): List<AudioRankingSnapshotRecord> {
+        return if (canViewAdultContent) this else filter { !it.isAdult }
+    }
+
+    private fun AudioRankingSnapshotRecord.toItem(
+        rank: Int,
+        showRankChange: Boolean,
+        previousRankByContentId: Map<Long, Int>
+    ): AudioRankingItem {
+        val previousRank = previousRankByContentId[contentId]
+        return AudioRankingItem(
+            contentId = contentId,
+            title = title,
+            creatorNickname = creatorNickname,
+            rank = rank,
+            rankChange = if (showRankChange && previousRank != null) previousRank - rank else null,
+            isNew = showRankChange && previousRank == null,
+            coverImageUrl = coverImageUrl
+        )
+    }
+
+    companion object {
+        private const val ITEM_LIMIT = 20
+    }
 }