feat(ranking): 크리에이터 랭킹 조회 서비스를 추가한다

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

@@ -0,0 +1,92 @@
+package kr.co.vividnext.sodalive.v2.ranking.application
+
+import kr.co.vividnext.sodalive.v2.ranking.domain.CreatorRankingItem
+import kr.co.vividnext.sodalive.v2.ranking.port.out.CreatorRankingBlockPort
+import kr.co.vividnext.sodalive.v2.ranking.port.out.CreatorRankingSnapshotPort
+import kr.co.vividnext.sodalive.v2.ranking.port.out.CreatorRankingSnapshotRecord
+import org.springframework.beans.factory.annotation.Value
+import org.springframework.stereotype.Service
+import org.springframework.transaction.annotation.Transactional
+
+@Service
+class CreatorRankingQueryService(
+    private val snapshotPort: CreatorRankingSnapshotPort,
+    private val blockPort: CreatorRankingBlockPort,
+    @Value("\${cloud.aws.cloud-front.host}")
+    private val cloudFrontHost: String
+) {
+    @Transactional(readOnly = true)
+    fun getCreatorRankings(viewerMemberId: Long?): CreatorRankingResult {
+        val latestItems = snapshotPort.findLatestSnapshots().toRankedItems()
+        if (latestItems.isEmpty()) {
+            return CreatorRankingResult(showRankChange = false, items = emptyList())
+        }
+
+        val previousItems = snapshotPort.findPreviousCompletedSnapshots().toRankedItems()
+        val previousRankByCreatorId = previousItems.associate { it.creatorId to it.rank }
+        val showRankChange = previousRankByCreatorId.isNotEmpty()
+        val blockedCreatorIds = findBlockedCreatorIds(viewerMemberId = viewerMemberId, items = latestItems)
+        val items = latestItems.map { item ->
+            val previousRank = previousRankByCreatorId[item.creatorId]
+            item.copy(
+                rankChange = if (showRankChange && previousRank != null) previousRank - item.rank else null,
+                isNew = showRankChange && previousRank == null
+            ).maskIfBlocked(blockedCreatorIds)
+        }
+
+        return CreatorRankingResult(showRankChange = showRankChange, items = items)
+    }
+
+    private fun List<CreatorRankingSnapshotRecord>.toRankedItems(): List<CreatorRankingItem> {
+        return groupBy { it.finalScore }
+            .toSortedMap(compareByDescending { it })
+            .values
+            .flatMap { it.shuffled() }
+            .take(RANKING_LIMIT)
+            .mapIndexed { index, snapshot -> snapshot.toItem(rank = index + 1) }
+    }
+
+    private fun CreatorRankingSnapshotRecord.toItem(rank: Int): CreatorRankingItem {
+        return CreatorRankingItem(
+            rank = rank,
+            rankChange = null,
+            isNew = false,
+            creatorId = creatorId,
+            nickname = nickname,
+            profileImageUrl = profileImageUrl
+        )
+    }
+
+    private fun findBlockedCreatorIds(viewerMemberId: Long?, items: List<CreatorRankingItem>): Set<Long> {
+        if (viewerMemberId == null) {
+            return emptySet()
+        }
+        return blockPort.findBlockedCreatorIds(
+            memberId = viewerMemberId,
+            creatorIds = items.map { it.creatorId }
+        )
+    }
+
+    private fun CreatorRankingItem.maskIfBlocked(blockedCreatorIds: Set<Long>): CreatorRankingItem {
+        if (!blockedCreatorIds.contains(creatorId)) {
+            return this
+        }
+        return copy(
+            creatorId = MASKED_CREATOR_ID,
+            nickname = MASKED_NICKNAME,
+            profileImageUrl = "$cloudFrontHost/$DEFAULT_PROFILE_IMAGE_PATH"
+        )
+    }
+
+    companion object {
+        private const val RANKING_LIMIT = 20
+        private const val MASKED_CREATOR_ID = 0L
+        private const val MASKED_NICKNAME = ""
+        private const val DEFAULT_PROFILE_IMAGE_PATH = "profile/default-profile.png"
+    }
+}
+
+data class CreatorRankingResult(
+    val showRankChange: Boolean,
+    val items: List<CreatorRankingItem>
+)

src/main/kotlin/kr/co/vividnext/sodalive/v2/ranking/port/out/CreatorRankingBlockPort.kt

@@ -0,0 +1,5 @@
+package kr.co.vividnext.sodalive.v2.ranking.port.out
+
+interface CreatorRankingBlockPort {
+    fun findBlockedCreatorIds(memberId: Long, creatorIds: Collection<Long>): Set<Long>
+}