challenge rank application layer 구현 (#216)

## Checklist
- [ ] 충분한 양의 자동화 테스트를 작성했는가?
  - 계단정복지도 서비스는 사이드 프로젝트로 진행되는 만큼 충분한 QA 없이 배포되는 경우가 많습니다. 따라서 자동화 테스트를 꼼꼼하게 작성하는 것이 서비스 품질을 유지하는 데 매우 중요합니다.

app-server/subprojects/bounded_context/challenge/application/src/main/kotlin/club/staircrusher/challenge/application/port/in/use_case/GetChallengeLeaderboardUseCase.kt

@@ -0,0 +1,32 @@
+package club.staircrusher.challenge.application.port.`in`.use_case
+
+import club.staircrusher.challenge.application.port.out.persistence.ChallengeRankRepository
+import club.staircrusher.challenge.application.port.out.persistence.ChallengeRepository
+import club.staircrusher.challenge.domain.model.ChallengeRank
+import club.staircrusher.stdlib.di.annotation.Component
+import club.staircrusher.stdlib.domain.SccDomainException
+import club.staircrusher.stdlib.persistence.TransactionManager
+
+/**
+ * Get the leaderboard of a challenge which shows only the top 10 users.
+ * If there are more than 2 users with the same score, those users' ranks
+ * are the same and the next rank is skipped. For example, if there are
+ * 3 users with the same score, the ranks are 1, 1, 1, 4, 5, 6, 7, 8, 9, 10.
+ */
+@Component
+class GetChallengeLeaderboardUseCase(
+    private val transactionManager: TransactionManager,
+    private val challengeRepository: ChallengeRepository,
+    private val challengeRankRepository: ChallengeRankRepository,
+) {
+    companion object {
+        const val NUMBER_OF_TOP_RANKER = 10
+    }
+
+    fun handle(challengeId: String): List<ChallengeRank> = transactionManager.doInTransaction {
+        val challenge = challengeRepository.findByIdOrNull(challengeId) ?: throw SccDomainException("잘못된 챌린지입니다.")
+        val leaderboards = challengeRankRepository.findTopNUsers(challenge.id, NUMBER_OF_TOP_RANKER)
+
+        leaderboards
+    }
+}

app-server/subprojects/bounded_context/challenge/application/src/main/kotlin/club/staircrusher/challenge/application/port/in/use_case/GetChallengeRankUseCase.kt

@@ -0,0 +1,31 @@
+package club.staircrusher.challenge.application.port.`in`.use_case
+
+import club.staircrusher.challenge.application.port.`in`.ChallengeService
+import club.staircrusher.challenge.application.port.out.persistence.ChallengeRankRepository
+import club.staircrusher.challenge.application.port.out.persistence.ChallengeRepository
+import club.staircrusher.challenge.domain.model.ChallengeRank
+import club.staircrusher.stdlib.di.annotation.Component
+import club.staircrusher.stdlib.domain.SccDomainException
+import club.staircrusher.stdlib.persistence.TransactionManager
+import club.staircrusher.user.application.port.`in`.UserApplicationService
+
+@Component
+class GetChallengeRankUseCase(
+    private val transactionManager: TransactionManager,
+    private val userApplicationService: UserApplicationService,
+    private val challengeRepository: ChallengeRepository,
+    private val challengeRankRepository: ChallengeRankRepository,
+    private val challengeService: ChallengeService,
+) {
+    fun handle(challengeId: String, userId: String): ChallengeRank? = transactionManager.doInTransaction {
+        userApplicationService.getUser(userId) ?: throw SccDomainException("잘못된 계정입니다.")
+
+        val challenge = challengeRepository.findByIdOrNull(challengeId) ?: throw SccDomainException("잘못된 챌린지입니다.")
+        if (!challengeService.hasJoined(userId, challengeId)) {
+            throw SccDomainException("참여하지 않은 챌린지 입니다.")
+        }
+
+        // if the user does not have rank yet, return null and let the user know that the rank will be updated soon
+        challengeRankRepository.findByUserId(challenge.id, userId)
+    }
+}

app-server/subprojects/bounded_context/challenge/application/src/main/kotlin/club/staircrusher/challenge/application/port/in/use_case/GetCountForNextChallengeRankUseCase.kt

@@ -0,0 +1,41 @@
+package club.staircrusher.challenge.application.port.`in`.use_case
+
+import club.staircrusher.challenge.application.port.`in`.ChallengeService
+import club.staircrusher.challenge.application.port.out.persistence.ChallengeRankRepository
+import club.staircrusher.challenge.application.port.out.persistence.ChallengeRepository
+import club.staircrusher.stdlib.di.annotation.Component
+import club.staircrusher.stdlib.domain.SccDomainException
+import club.staircrusher.stdlib.persistence.TransactionManager
+import club.staircrusher.user.application.port.`in`.UserApplicationService
+
+/**
+ * Get the number of contributions needed to reach the next rank.
+ * If the user is already at the highest rank, return 0.
+ */
+@Component
+class GetCountForNextChallengeRankUseCase(
+    private val transactionManager: TransactionManager,
+    private val userApplicationService: UserApplicationService,
+    private val challengeRepository: ChallengeRepository,
+    private val challengeRankRepository: ChallengeRankRepository,
+    private val challengeService: ChallengeService,
+) {
+    fun handle(challengeId: String, userId: String): Int?  = transactionManager.doInTransaction {
+        userApplicationService.getUser(userId) ?: throw SccDomainException("잘못된 계정입니다.")
+        val challenge = challengeRepository.findByIdOrNull(challengeId) ?: throw SccDomainException("잘못된 챌린지입니다.")
+        if (!challengeService.hasJoined(userId, challengeId)) {
+            throw SccDomainException("참여하지 않은 챌린지 입니다.")
+        }
+
+        // if the user does not have rank yet, return null and let the user know that the rank will be updated soon
+        val challengeRank = challengeRankRepository.findByUserId(challenge.id, userId)
+        val rank =  challengeRank?.rank ?: return@doInTransaction null
+
+        if (rank == 1L) {
+            0
+        } else {
+            val nextRank = challengeRankRepository.findNextRank(challenge.id, rank)!!
+            nextRank.contributionCount - challengeRank.contributionCount
+        }
+    }
+}

app-server/subprojects/bounded_context/challenge/application/src/main/kotlin/club/staircrusher/challenge/application/port/in/use_case/UpdateChallengeRanksUseCase.kt

@@ -0,0 +1,75 @@
+package club.staircrusher.challenge.application.port.`in`.use_case
+
+import club.staircrusher.challenge.application.port.out.persistence.ChallengeContributionRepository
+import club.staircrusher.challenge.application.port.out.persistence.ChallengeParticipationRepository
+import club.staircrusher.challenge.application.port.out.persistence.ChallengeRankRepository
+import club.staircrusher.challenge.application.port.out.persistence.ChallengeRepository
+import club.staircrusher.challenge.domain.model.ChallengeContribution
+import club.staircrusher.challenge.domain.model.ChallengeRank
+import club.staircrusher.stdlib.clock.SccClock
+import club.staircrusher.stdlib.di.annotation.Component
+import club.staircrusher.stdlib.domain.entity.EntityIdGenerator
+import club.staircrusher.stdlib.persistence.TransactionIsolationLevel
+import club.staircrusher.stdlib.persistence.TransactionManager
+import java.time.Duration
+import java.time.Instant
+
+/**
+ * Update the users' ranks of all challenges.
+ */
+@Component
+class UpdateChallengeRanksUseCase(
+    private val transactionManager: TransactionManager,
+    private val challengeRepository: ChallengeRepository,
+    private val challengeRankRepository: ChallengeRankRepository,
+    private val challengeContributionRepository: ChallengeContributionRepository,
+    private val challengeParticipationRepository: ChallengeParticipationRepository,
+) {
+    fun handle() {
+        val challenges = challengeRepository.findAllOrderByCreatedAtDesc()
+            .filter { (it.endsAt ?: Instant.MAX) > SccClock.instant() - Duration.ofDays(1) }
+        challenges.forEach { challenge ->
+            val now = SccClock.instant()
+            transactionManager.doInTransaction(TransactionIsolationLevel.SERIALIZABLE) {
+                val contributions = challengeContributionRepository.findByChallengeId(challenge.id)
+                val participants = challengeParticipationRepository.findByChallengeId(challenge.id)
+
+                val userIds = participants.map { it.userId }.toSet()
+                val contributionUserIds = contributions.map { it.userId }.toSet()
+                val missingUserIds = userIds - contributionUserIds
+                val userWithNoContribution = missingUserIds.map { userId -> userId to emptyList<ChallengeContribution>() }
+
+                val ranks = (contributions.groupBy { it.userId } + userWithNoContribution)
+                    .map { (userId, contributions) ->
+                        val challengeRank = challengeRankRepository.findByUserId(challenge.id, userId) ?: ChallengeRank(
+                            id = EntityIdGenerator.generateRandom(),
+                            challengeId = challenge.id,
+                            userId = userId,
+                            contributionCount = contributions.size,
+                            rank = -1,
+                            createdAt = now,
+                            updatedAt = now,
+                        )
+
+                        challengeRank.apply {
+                            contributionCount = contributions.size
+                            updatedAt = now
+                        }
+                    }
+
+                var nextRank = 1L
+                val updatedRanks = ranks.groupBy { it.contributionCount }
+                    .toSortedMap(compareByDescending { it })
+                    .flatMap { (_, ranks) ->
+                        val currentRank = nextRank
+                        nextRank += ranks.size
+                        ranks.map {
+                            it.apply { rank = currentRank; updatedAt = now }
+                        }
+                    }
+                challengeRankRepository.removeAll(challenge.id)
+                challengeRankRepository.saveAll(updatedRanks)
+            }
+        }
+    }
+}

app-server/subprojects/bounded_context/challenge/application/src/main/kotlin/club/staircrusher/challenge/application/port/out/persistence/ChallengeRankRepository.kt

@@ -0,0 +1,15 @@
+package club.staircrusher.challenge.application.port.out.persistence
+
+import club.staircrusher.challenge.domain.model.ChallengeRank
+import club.staircrusher.stdlib.domain.repository.EntityRepository
+
+interface ChallengeRankRepository : EntityRepository<ChallengeRank, String> {
+    fun findTopNUsers(challengeId: String, n: Int): List<ChallengeRank>
+    fun findByUserId(challengeId: String, userId: String): ChallengeRank?
+    fun findByRank(challengeId: String, rank: Long): ChallengeRank?
+    fun findNextRank(challengeId: String, rank: Long): ChallengeRank?
+    fun findByContributionCount(challengeId: String, contributionCount: Int): ChallengeRank?
+    fun findLastRank(challengeId: String): Long?
+    fun findAll(challengeId: String): List<ChallengeRank>
+    fun removeAll(challengeId: String): Unit
+}

app-server/subprojects/bounded_context/challenge/domain/src/main/kotlin/club/staircrusher/challenge/domain/model/ChallengeRank.kt

@@ -0,0 +1,13 @@
+package club.staircrusher.challenge.domain.model
+
+import java.time.Instant
+
+class ChallengeRank(
+    val id: String,
+    val challengeId: String,
+    val userId: String,
+    var contributionCount: Int,
+    var rank: Long,
+    var createdAt: Instant,
+    var updatedAt: Instant,
+)