[BOOK-198] feat: apis - 사용자 홈 화면에 최근 읽은 도서 조회 기능 추가

Author: move-hoon

apis/src/main/kotlin/org/yapp/apis/book/service/UserBookService.kt

@@ -4,17 +4,18 @@ import org.springframework.data.domain.Page
 import org.springframework.data.domain.Pageable
 import org.springframework.stereotype.Service
 import org.yapp.apis.auth.dto.request.UserBooksByIsbnsRequest
+import org.yapp.apis.book.dto.request.UpsertUserBookRequest
 import org.yapp.apis.book.dto.response.UserBookPageResponse
 import org.yapp.apis.book.dto.response.UserBookResponse
-import org.yapp.apis.book.dto.request.UpsertUserBookRequest
 import org.yapp.apis.book.exception.UserBookErrorCode
 import org.yapp.apis.book.exception.UserBookNotFoundException
+import org.yapp.apis.home.dto.response.UserHomeResponse
 import org.yapp.domain.userbook.BookStatus
 import org.yapp.domain.userbook.UserBook
 import org.yapp.domain.userbook.UserBookDomainService
 import org.yapp.domain.userbook.UserBookSortType
-import java.util.UUID
-
+import org.yapp.domain.userbook.vo.UserBookWithLastRecordVO
+import java.util.*
 
 @Service
 class UserBookService(
@@ -42,7 +43,6 @@ class UserBookService(
             )
     }
 
-
     fun findAllByUserIdAndBookIsbnIn(userBooksByIsbnsRequest: UserBooksByIsbnsRequest): List<UserBookResponse> {
         val userBooks = userBookDomainService.findAllByUserIdAndBookIsbnIn(
             userBooksByIsbnsRequest.validUserId(),
@@ -51,6 +51,55 @@ class UserBookService(
         return userBooks.map { UserBookResponse.from(it) }
     }
 
+    fun findRecentReadingBooksForHome(userId: UUID, limit: Int): UserHomeResponse {
+        val fetchLimit = maxOf(limit * 2, 10)
+        val allUserBookVoInfos = userBookDomainService.findRecentReadingBooksWithLastRecord(userId, fetchLimit)
+        val selectedBooks = selectBooksByPriority(allUserBookVoInfos, limit)
+
+        return UserHomeResponse.from(selectedBooks)
+    }
+
+    private fun selectBooksByPriority(
+        allBooks: List<UserBookWithLastRecordVO>,
+        targetLimit: Int
+    ): List<UserBookWithLastRecordVO> {
+        if (allBooks.isEmpty()) return emptyList()
+
+        val result = mutableListOf<UserBookWithLastRecordVO>()
+        val usedBookIds = mutableSetOf<UUID>()
+
+        val readingBooks = allBooks
+            .filter { it.status == BookStatus.READING }
+            .sortedByDescending { it.lastRecordedAt }
+
+        val readingSelected = readingBooks.take(targetLimit)
+        result.addAll(readingSelected)
+        usedBookIds.addAll(readingSelected.map { it.id.value })
+
+        if (result.size < targetLimit) {
+            val remainingSlots = targetLimit - result.size
+            val completedBooks = allBooks
+                .filter { it.status == BookStatus.COMPLETED && !usedBookIds.contains(it.id.value) }
+                .sortedByDescending { it.lastRecordedAt }
+
+            val completedSelected = completedBooks.take(remainingSlots)
+            result.addAll(completedSelected)
+            usedBookIds.addAll(completedSelected.map { it.id.value })
+        }
+
+        if (result.size < targetLimit) {
+            val remainingSlots = targetLimit - result.size
+            val remainingBooks = allBooks
+                .filter { !usedBookIds.contains(it.id.value) }
+                .sortedByDescending { it.lastRecordedAt }
+
+            val remainingSelected = remainingBooks.take(remainingSlots)
+            result.addAll(remainingSelected)
+        }
+
+        return result
+    }
+
     private fun findUserBooksByDynamicCondition(
         userId: UUID,
         status: BookStatus?,