Decouple Cache and Download behaviour (#493)

* Separate cache dir from download dir

* Move downloader logic outside of caching/image download logic

* remove unnecessary method duplication

* moved download logic inside download provider

* optimize and handle partial downloads

* made code review changes

server/src/main/kotlin/suwayomi/tachidesk/manga/impl/download/DownloadedFilesProvider.kt

@@ -0,0 +1,20 @@
+package suwayomi.tachidesk.manga.impl.download
+
+import kotlinx.coroutines.CoroutineScope
+import suwayomi.tachidesk.manga.impl.download.model.DownloadChapter
+import java.io.InputStream
+
+/*
+* Base class for downloaded chapter files provider, example: Folder, Archive
+* */
+abstract class DownloadedFilesProvider(val mangaId: Int, val chapterId: Int) {
+    abstract fun getImage(index: Int): Pair<InputStream, String>
+
+    abstract suspend fun download(
+        download: DownloadChapter,
+        scope: CoroutineScope,
+        step: suspend (DownloadChapter?, Boolean) -> Unit
+    ): Boolean
+
+    abstract fun delete(): Boolean
+}

server/src/main/kotlin/suwayomi/tachidesk/manga/impl/download/Downloader.kt

@@ -13,17 +13,13 @@ import kotlinx.coroutines.Job
 import kotlinx.coroutines.cancelAndJoin
 import kotlinx.coroutines.currentCoroutineContext
 import kotlinx.coroutines.ensureActive
-import kotlinx.coroutines.flow.distinctUntilChanged
-import kotlinx.coroutines.flow.launchIn
-import kotlinx.coroutines.flow.onEach
-import kotlinx.coroutines.flow.sample
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
 import mu.KotlinLogging
 import org.jetbrains.exposed.sql.and
 import org.jetbrains.exposed.sql.transactions.transaction
 import org.jetbrains.exposed.sql.update
-import suwayomi.tachidesk.manga.impl.Page.getPageImage
+import suwayomi.tachidesk.manga.impl.ChapterDownloadHelper
 import suwayomi.tachidesk.manga.impl.chapter.getChapterDownloadReady
 import suwayomi.tachidesk.manga.impl.download.model.DownloadChapter
 import suwayomi.tachidesk.manga.impl.download.model.DownloadState.Downloading
@@ -95,33 +91,7 @@ class Downloader(
                 download.chapter = getChapterDownloadReady(download.chapterIndex, download.mangaId)
                 step(download, false)
 
-                val pageCount = download.chapter.pageCount
-                for (pageNum in 0 until pageCount) {
-                    var pageProgressJob: Job? = null
-                    try {
-                        getPageImage(
-                            mangaId = download.mangaId,
-                            chapterIndex = download.chapterIndex,
-                            index = pageNum,
-                            progressFlow = { flow ->
-                                pageProgressJob = flow
-                                    .sample(100)
-                                    .distinctUntilChanged()
-                                    .onEach {
-                                        download.progress = (pageNum.toFloat() + (it.toFloat() * 0.01f)) / pageCount
-                                        step(null, false) // don't throw on canceled download here since we can't do anything
-                                    }
-                                    .launchIn(scope)
-                            }
-                        ).first.close()
-                    } finally {
-                        // always cancel the page progress job even if it throws an exception to avoid memory leaks
-                        pageProgressJob?.cancel()
-                    }
-                    // TODO: retry on error with 2,4,8 seconds of wait
-                    download.progress = ((pageNum + 1).toFloat()) / pageCount
-                    step(download, false)
-                }
+                ChapterDownloadHelper.download(download.mangaId, download.chapter.id, download, scope, this::step)
                 download.state = Finished
                 transaction {
                     ChapterTable.update({ (ChapterTable.manga eq download.mangaId) and (ChapterTable.sourceOrder eq download.chapterIndex) }) {

server/src/main/kotlin/suwayomi/tachidesk/manga/impl/download/FolderProvider.kt

@@ -0,0 +1,87 @@
+package suwayomi.tachidesk.manga.impl.download
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.FlowPreview
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.launchIn
+import kotlinx.coroutines.flow.onEach
+import kotlinx.coroutines.flow.sample
+import suwayomi.tachidesk.manga.impl.Page
+import suwayomi.tachidesk.manga.impl.Page.getPageName
+import suwayomi.tachidesk.manga.impl.download.model.DownloadChapter
+import suwayomi.tachidesk.manga.impl.util.getChapterDir
+import suwayomi.tachidesk.manga.impl.util.storage.ImageResponse
+import java.io.File
+import java.io.FileInputStream
+import java.io.InputStream
+
+/*
+* Provides downloaded files when pages were downloaded into folders
+* */
+class FolderProvider(mangaId: Int, chapterId: Int) : DownloadedFilesProvider(mangaId, chapterId) {
+    override fun getImage(index: Int): Pair<InputStream, String> {
+        val chapterDir = getChapterDir(mangaId, chapterId)
+        val folder = File(chapterDir)
+        folder.mkdirs()
+        val file = folder.listFiles()?.get(index)
+        val fileType = file!!.name.substringAfterLast(".")
+        return Pair(FileInputStream(file).buffered(), "image/$fileType")
+    }
+
+    @OptIn(FlowPreview::class)
+    override suspend fun download(
+        download: DownloadChapter,
+        scope: CoroutineScope,
+        step: suspend (DownloadChapter?, Boolean) -> Unit
+    ): Boolean {
+        val pageCount = download.chapter.pageCount
+        val chapterDir = getChapterDir(mangaId, chapterId)
+        val folder = File(chapterDir)
+        folder.mkdirs()
+
+        for (pageNum in 0 until pageCount) {
+            var pageProgressJob: Job? = null
+            val fileName = getPageName(pageNum) // might have to change this to index stored in database
+            if (isExistingFile(folder, fileName)) continue
+            try {
+                Page.getPageImage(
+                    mangaId = download.mangaId,
+                    chapterIndex = download.chapterIndex,
+                    index = pageNum
+                ) { flow ->
+                    pageProgressJob = flow
+                        .sample(100)
+                        .distinctUntilChanged()
+                        .onEach {
+                            download.progress = (pageNum.toFloat() + (it.toFloat() * 0.01f)) / pageCount
+                            step(null, false) // don't throw on canceled download here since we can't do anything
+                        }
+                        .launchIn(scope)
+                }.first.use { image ->
+                    val filePath = "$chapterDir/$fileName"
+                    ImageResponse.saveImage(filePath, image)
+                }
+            } finally {
+                // always cancel the page progress job even if it throws an exception to avoid memory leaks
+                pageProgressJob?.cancel()
+            }
+            // TODO: retry on error with 2,4,8 seconds of wait
+            download.progress = ((pageNum + 1).toFloat()) / pageCount
+            step(download, false)
+        }
+        return true
+    }
+
+    override fun delete(): Boolean {
+        val chapterDir = getChapterDir(mangaId, chapterId)
+        return File(chapterDir).deleteRecursively()
+    }
+
+    private fun isExistingFile(folder: File, fileName: String): Boolean {
+        val existingFile = folder.listFiles { file ->
+            file.isFile && file.name.startsWith(fileName)
+        }?.firstOrNull()
+        return existingFile?.exists() == true
+    }
+}