feat(audio-recommendation): 오디오 추천 점수 정책을 추가한다

src/main/kotlin/kr/co/vividnext/sodalive/v2/audio/recommendation/domain/AudioRecommendationScorePolicy.kt

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+package kr.co.vividnext.sodalive.v2.audio.recommendation.domain
+
+import java.time.LocalDateTime
+import java.time.temporal.ChronoUnit
+
+class AudioRecommendationScorePolicy {
+    fun calculateNewAndHotScore(
+        viewCount: Long,
+        likeCount: Long,
+        commentCount: Long,
+        releaseDate: LocalDateTime,
+        now: LocalDateTime
+    ): Double {
+        return viewCount * NEW_AND_HOT_VIEW_WEIGHT +
+            likeCount * NEW_AND_HOT_LIKE_WEIGHT +
+            commentCount * NEW_AND_HOT_COMMENT_WEIGHT +
+            newAndHotRecencyMultiplier(releaseDate, now) * NEW_AND_HOT_RECENCY_WEIGHT
+    }
+
+    fun calculateRecommendedAudioScore(
+        viewCount: Long,
+        likeCount: Long,
+        commentCount: Long,
+        releaseDate: LocalDateTime,
+        now: LocalDateTime
+    ): Double {
+        return viewCount * RECOMMENDED_VIEW_WEIGHT +
+            likeCount * RECOMMENDED_LIKE_WEIGHT +
+            commentCount * RECOMMENDED_COMMENT_WEIGHT +
+            recommendedAudioRecencyMultiplier(releaseDate, now) * RECOMMENDED_RECENCY_WEIGHT
+    }
+
+    fun calculateCommentScore(commentCount: Long, latestCommentAt: LocalDateTime, now: LocalDateTime): Double {
+        return commentCount * COMMENT_COUNT_WEIGHT + commentRecencyMultiplier(latestCommentAt, now) * COMMENT_RECENCY_WEIGHT
+    }
+
+    fun newAndHotRecencyMultiplier(releaseDate: LocalDateTime, now: LocalDateTime): Double {
+        val days = daysBetween(releaseDate, now)
+        return when {
+            days <= 3 -> 1.3
+            days <= 7 -> 1.15
+            days <= 14 -> 1.0
+            else -> 0.8
+        }
+    }
+
+    fun recommendedAudioRecencyMultiplier(releaseDate: LocalDateTime, now: LocalDateTime): Double {
+        val days = daysBetween(releaseDate, now)
+        return when {
+            days <= 3 -> 1.3
+            days <= 7 -> 1.15
+            days <= 30 -> 1.1
+            else -> 1.0
+        }
+    }
+
+    fun commentRecencyMultiplier(latestCommentAt: LocalDateTime, now: LocalDateTime): Double {
+        val days = daysBetween(latestCommentAt, now)
+        return when {
+            days <= 3 -> 1.3
+            days <= 7 -> 1.15
+            days <= 14 -> 1.0
+            else -> 0.0
+        }
+    }
+
+    private fun daysBetween(from: LocalDateTime, now: LocalDateTime): Long {
+        return ChronoUnit.DAYS.between(from.toLocalDate(), now.toLocalDate()).coerceAtLeast(0)
+    }
+
+    companion object {
+        const val NEW_AND_HOT_RECENCY_WEIGHT = 35.0
+        const val NEW_AND_HOT_VIEW_WEIGHT = 35.0
+        const val NEW_AND_HOT_LIKE_WEIGHT = 15.0
+        const val NEW_AND_HOT_COMMENT_WEIGHT = 15.0
+        const val RECOMMENDED_VIEW_WEIGHT = 45.0
+        const val RECOMMENDED_LIKE_WEIGHT = 25.0
+        const val RECOMMENDED_COMMENT_WEIGHT = 20.0
+        const val RECOMMENDED_RECENCY_WEIGHT = 10.0
+        const val COMMENT_COUNT_WEIGHT = 80.0
+        const val COMMENT_RECENCY_WEIGHT = 20.0
+    }
+}

src/test/kotlin/kr/co/vividnext/sodalive/v2/audio/recommendation/domain/AudioRecommendationScorePolicyTest.kt

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+package kr.co.vividnext.sodalive.v2.audio.recommendation.domain
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.Test
+import java.time.LocalDateTime
+
+class AudioRecommendationScorePolicyTest {
+    private val policy = AudioRecommendationScorePolicy()
+    private val now = LocalDateTime.of(2026, 6, 23, 12, 0)
+
+    @Test
+    @DisplayName("New & Hot 점수는 원본 count를 정규화하지 않고 가중합으로 계산한다")
+    fun shouldCalculateNewAndHotScoreWithoutNormalization() {
+        val score = policy.calculateNewAndHotScore(10, 4, 2, now.minusDays(2), now)
+
+        assertEquals(485.5, score)
+    }
+
+    @Test
+    @DisplayName("추천 오디오 점수는 원본 count와 최신성 배수를 가중합으로 계산한다")
+    fun shouldCalculateRecommendedAudioScoreWithoutNormalization() {
+        val score = policy.calculateRecommendedAudioScore(10, 4, 2, now.minusDays(10), now)
+
+        assertEquals(601.0, score)
+    }
+
+    @Test
+    @DisplayName("최신성 배수는 정책별 일수 경계를 적용한다")
+    fun shouldReturnRecencyMultipliersByPolicyBoundaries() {
+        assertEquals(1.3, policy.newAndHotRecencyMultiplier(now.minusDays(3), now))
+        assertEquals(1.15, policy.newAndHotRecencyMultiplier(now.minusDays(7), now))
+        assertEquals(1.0, policy.newAndHotRecencyMultiplier(now.minusDays(14), now))
+        assertEquals(0.8, policy.newAndHotRecencyMultiplier(now.minusDays(15), now))
+        assertEquals(1.3, policy.recommendedAudioRecencyMultiplier(now.minusDays(3), now))
+        assertEquals(1.15, policy.recommendedAudioRecencyMultiplier(now.minusDays(7), now))
+        assertEquals(1.1, policy.recommendedAudioRecencyMultiplier(now.minusDays(30), now))
+        assertEquals(1.0, policy.recommendedAudioRecencyMultiplier(now.minusDays(31), now))
+        assertEquals(1.3, policy.commentRecencyMultiplier(now.minusDays(3), now))
+        assertEquals(1.15, policy.commentRecencyMultiplier(now.minusDays(7), now))
+        assertEquals(1.0, policy.commentRecencyMultiplier(now.minusDays(14), now))
+        assertEquals(0.0, policy.commentRecencyMultiplier(now.minusDays(15), now))
+    }
+}