add pagination to recentChapters (#246)

* add pagination to recentChapters

* Use kotlin native library

Co-authored-by: Mitchell Syer <Mitchellptbo@gmail.com>

Co-authored-by: Mitchell Syer <Mitchellptbo@gmail.com>

server/src/main/kotlin/suwayomi/tachidesk/manga/MangaAPI.kt

@@ -112,7 +112,7 @@ object MangaAPI {
         }
 
         path("update") {
-            get("recentChapters", UpdateController::recentChapters)
+            get("recentChapters/{pageNum}", UpdateController::recentChapters)
         }
     }
 }

server/src/main/kotlin/suwayomi/tachidesk/manga/controller/UpdateController.kt

@@ -14,9 +14,11 @@ import suwayomi.tachidesk.server.JavalinSetup.future
 object UpdateController {
     /** get recently updated manga chapters */
     fun recentChapters(ctx: Context) {
+        val pageNum = ctx.pathParam("pageNum").toInt()
+
         ctx.future(
             future {
-                Chapter.getRecentChapters()
+                Chapter.getRecentChapters(pageNum)
             }
         )
     }

server/src/main/kotlin/suwayomi/tachidesk/manga/impl/Chapter.kt

@@ -27,6 +27,8 @@ import suwayomi.tachidesk.manga.impl.util.source.GetCatalogueSource.getCatalogue
 import suwayomi.tachidesk.manga.impl.util.storage.ImageResponse
 import suwayomi.tachidesk.manga.model.dataclass.ChapterDataClass
 import suwayomi.tachidesk.manga.model.dataclass.MangaChapterDataClass
+import suwayomi.tachidesk.manga.model.dataclass.PaginatedList
+import suwayomi.tachidesk.manga.model.dataclass.paginatedFrom
 import suwayomi.tachidesk.manga.model.table.ChapterMetaTable
 import suwayomi.tachidesk.manga.model.table.ChapterTable
 import suwayomi.tachidesk.manga.model.table.MangaTable
@@ -321,17 +323,19 @@ object Chapter {
         }
     }
 
-    fun getRecentChapters(): List<MangaChapterDataClass> {
-        return transaction {
-            (ChapterTable innerJoin MangaTable)
-                .select { (MangaTable.inLibrary eq true) and (ChapterTable.fetchedAt greater MangaTable.inLibraryAt) }
-                .orderBy(ChapterTable.fetchedAt to SortOrder.DESC)
-                .map {
-                    MangaChapterDataClass(
-                        MangaTable.toDataClass(it),
-                        ChapterTable.toDataClass(it)
-                    )
-                }
+    fun getRecentChapters(pageNum: Int): PaginatedList<MangaChapterDataClass> {
+        return paginatedFrom(pageNum) {
+            transaction {
+                (ChapterTable innerJoin MangaTable)
+                    .select { (MangaTable.inLibrary eq true) and (ChapterTable.fetchedAt greater MangaTable.inLibraryAt) }
+                    .orderBy(ChapterTable.fetchedAt to SortOrder.DESC)
+                    .map {
+                        MangaChapterDataClass(
+                            MangaTable.toDataClass(it),
+                            ChapterTable.toDataClass(it)
+                        )
+                    }
+            }
         }
     }
 }

server/src/main/kotlin/suwayomi/tachidesk/manga/model/dataclass/PaginatedList.kt

@@ -0,0 +1,40 @@
+package suwayomi.tachidesk.manga.model.dataclass
+
+/*
+ * Copyright (C) Contributors to the Suwayomi project
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+import kotlin.math.min
+
+data class PaginatedList<T>(
+    val page: List<T>,
+    val hasNextPage: Boolean,
+)
+
+const val PaginationFactor = 50
+
+fun <T> paginatedFrom(
+    pageNum: Int,
+    paginationFactor: Int = PaginationFactor,
+    lister: () -> List<T>
+): PaginatedList<T> {
+    val list = lister()
+    val lastIndex = list.size - 1
+
+    val lowerIndex = pageNum * paginationFactor
+    val higherIndex = (pageNum + 1) * paginationFactor - 1
+
+    if (lowerIndex > lastIndex) {
+        return PaginatedList(emptyList(), false)
+    }
+
+    val sliced = list.slice(lowerIndex..min(lastIndex, higherIndex))
+
+    return PaginatedList(
+        sliced,
+        higherIndex < lastIndex
+    )
+}

server/src/test/kotlin/suwayomi/tachidesk/manga/model/PaginatedListTest.kt

@@ -0,0 +1,105 @@
+package suwayomi.tachidesk.manga.model
+
+/*
+ * Copyright (C) Contributors to the Suwayomi project
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import suwayomi.tachidesk.manga.model.dataclass.PaginatedList
+import suwayomi.tachidesk.manga.model.dataclass.PaginationFactor
+import suwayomi.tachidesk.manga.model.dataclass.paginatedFrom
+import suwayomi.tachidesk.test.ApplicationTest
+
+class PaginatedListTest : ApplicationTest() {
+    @Test
+    fun `empty list`() {
+        val paginated = paginatedFrom(0) { listIndicesOf(0, 0) }
+
+        assertEquals(
+            PaginatedList(emptyList<Int>(), false),
+            paginated
+        )
+    }
+
+    @Test
+    fun `size smaller than PaginationFactor`() {
+        val paginated = paginatedFrom(0) { listIndicesOf(0, PaginationFactor - 1) }
+
+        assertEquals(
+            PaginatedList(listIndicesOf(0, PaginationFactor - 1), false),
+            paginated,
+        )
+    }
+
+    @Test
+    fun `one less than two times PaginationFactor`() {
+        val masterLister = { listIndicesOf(0, PaginationFactor * 2 - 1) }
+
+        val firstPage = paginatedFrom(0, lister = masterLister)
+
+        assertEquals(
+            PaginatedList(listIndicesOf(0, PaginationFactor), true),
+            firstPage,
+        )
+
+        val secondPage = paginatedFrom(1, lister = masterLister)
+
+        assertEquals(
+            PaginatedList(listIndicesOf(PaginationFactor, PaginationFactor * 2 - 1), false),
+            secondPage,
+        )
+    }
+
+    @Test
+    fun `two times PaginationFactor`() {
+        val masterLister = { listIndicesOf(0, PaginationFactor * 2) }
+
+        val firstPage = paginatedFrom(0, lister = masterLister)
+
+        assertEquals(
+            PaginatedList(listIndicesOf(0, PaginationFactor), true),
+            firstPage,
+        )
+
+        val secondPage = paginatedFrom(1, lister = masterLister)
+
+        assertEquals(
+            PaginatedList(listIndicesOf(PaginationFactor, PaginationFactor * 2), false),
+            secondPage,
+        )
+    }
+
+    @Test
+    fun `one more than two times PaginationFactor`() {
+        val masterLister = { listIndicesOf(0, PaginationFactor * 2 + 1) }
+
+        val firstPage = paginatedFrom(0, lister = masterLister)
+
+        assertEquals(
+            PaginatedList(listIndicesOf(0, PaginationFactor), true),
+            firstPage,
+        )
+
+        val secondPage = paginatedFrom(1, lister = masterLister)
+
+        assertEquals(
+            PaginatedList(listIndicesOf(PaginationFactor, PaginationFactor * 2), true),
+            secondPage,
+        )
+
+        val thirdPage = paginatedFrom(2, lister = masterLister)
+
+        assertEquals(
+            PaginatedList(listIndicesOf(PaginationFactor * 2, PaginationFactor * 2 + 1), false),
+            thirdPage,
+        )
+    }
+
+    private fun listIndicesOf(first: Int, last: Int): List<Int> {
+        return (first until last).toList()
+    }
+}