Prefetch chapter

app/src/main/AndroidManifest.xml

@@ -188,6 +188,9 @@
 				android:name="android.content.SyncAdapter"
 				android:resource="@xml/sync_history" />
 		</service>
+		<service
+			android:name="org.koitharu.kotatsu.details.service.MangaPrefetchService"
+			android:exported="false" />
 
 		<provider
 			android:name="org.koitharu.kotatsu.search.ui.MangaSuggestionsProvider"
@@ -250,7 +253,7 @@
 			android:value="true" />
 		<meta-data
 			android:name="com.samsung.android.icon_container.has_icon_container"
-			android:value="@bool/com_samsung_android_icon_container_has_icon_container"/>
+			android:value="@bool/com_samsung_android_icon_container_has_icon_container" />
 
 	</application>
 

app/src/main/java/org/koitharu/kotatsu/core/AppModule.kt

@@ -24,6 +24,9 @@ import okhttp3.CookieJar
 import okhttp3.OkHttpClient
 import org.koitharu.kotatsu.BuildConfig
 import org.koitharu.kotatsu.base.ui.util.ActivityRecreationHandle
+import org.koitharu.kotatsu.core.cache.ContentCache
+import org.koitharu.kotatsu.core.cache.MemoryContentCache
+import org.koitharu.kotatsu.core.cache.StubContentCache
 import org.koitharu.kotatsu.core.db.MangaDatabase
 import org.koitharu.kotatsu.core.network.*
 import org.koitharu.kotatsu.core.network.cookies.AndroidCookieJar
@@ -44,6 +47,7 @@ import org.koitharu.kotatsu.search.ui.MangaSuggestionsProvider
 import org.koitharu.kotatsu.settings.backup.BackupObserver
 import org.koitharu.kotatsu.sync.domain.SyncController
 import org.koitharu.kotatsu.utils.IncognitoModeIndicator
+import org.koitharu.kotatsu.utils.ext.activityManager
 import org.koitharu.kotatsu.utils.ext.connectivityManager
 import org.koitharu.kotatsu.utils.ext.isLowRamDevice
 import org.koitharu.kotatsu.utils.image.CoilImageGetter
@@ -182,5 +186,17 @@ interface AppModule {
 			activityRecreationHandle,
 			incognitoModeIndicator,
 		)
+
+		@Provides
+		@Singleton
+		fun provideContentCache(
+			@ApplicationContext context: Context,
+		): ContentCache {
+			return if (context.activityManager?.isLowRamDevice == true) {
+				StubContentCache()
+			} else {
+				MemoryContentCache()
+			}
+		}
 	}
 }

app/src/main/java/org/koitharu/kotatsu/core/cache/ContentCache.kt

@@ -0,0 +1,22 @@
+package org.koitharu.kotatsu.core.cache
+
+import kotlinx.coroutines.Deferred
+import org.koitharu.kotatsu.parsers.model.Manga
+import org.koitharu.kotatsu.parsers.model.MangaPage
+import org.koitharu.kotatsu.parsers.model.MangaSource
+
+interface ContentCache {
+
+	suspend fun getDetails(source: MangaSource, url: String): Manga?
+
+	fun putDetails(source: MangaSource, url: String, details: Deferred<Manga>)
+
+	suspend fun getPages(source: MangaSource, url: String): List<MangaPage>?
+
+	fun putPages(source: MangaSource, url: String, pages: Deferred<List<MangaPage>>)
+
+	data class Key(
+		val source: MangaSource,
+		val url: String,
+	)
+}

app/src/main/java/org/koitharu/kotatsu/core/cache/DeferredLruCache.kt

@@ -0,0 +1,17 @@
+package org.koitharu.kotatsu.core.cache
+
+import androidx.collection.LruCache
+import kotlinx.coroutines.Deferred
+
+class DeferredLruCache<T>(maxSize: Int) : LruCache<ContentCache.Key, Deferred<T>>(maxSize) {
+
+	override fun entryRemoved(
+		evicted: Boolean,
+		key: ContentCache.Key,
+		oldValue: Deferred<T>,
+		newValue: Deferred<T>?,
+	) {
+		super.entryRemoved(evicted, key, oldValue, newValue)
+		oldValue.cancel()
+	}
+}

app/src/main/java/org/koitharu/kotatsu/core/cache/MemoryContentCache.kt

@@ -0,0 +1,29 @@
+package org.koitharu.kotatsu.core.cache
+
+import kotlinx.coroutines.Deferred
+import org.koitharu.kotatsu.parsers.model.Manga
+import org.koitharu.kotatsu.parsers.model.MangaPage
+import org.koitharu.kotatsu.parsers.model.MangaSource
+
+@Suppress("DeferredResultUnused")
+class MemoryContentCache : ContentCache {
+
+	private val detailsCache = DeferredLruCache<Manga>(10)
+	private val pagesCache = DeferredLruCache<List<MangaPage>>(10)
+
+	override suspend fun getDetails(source: MangaSource, url: String): Manga? {
+		return detailsCache[ContentCache.Key(source, url)]?.await()
+	}
+
+	override fun putDetails(source: MangaSource, url: String, details: Deferred<Manga>) {
+		detailsCache.put(ContentCache.Key(source, url), details)
+	}
+
+	override suspend fun getPages(source: MangaSource, url: String): List<MangaPage>? {
+		return pagesCache[ContentCache.Key(source, url)]?.await()
+	}
+
+	override fun putPages(source: MangaSource, url: String, pages: Deferred<List<MangaPage>>) {
+		pagesCache.put(ContentCache.Key(source, url), pages)
+	}
+}

app/src/main/java/org/koitharu/kotatsu/core/cache/StubContentCache.kt

@@ -0,0 +1,17 @@
+package org.koitharu.kotatsu.core.cache
+
+import kotlinx.coroutines.Deferred
+import org.koitharu.kotatsu.parsers.model.Manga
+import org.koitharu.kotatsu.parsers.model.MangaPage
+import org.koitharu.kotatsu.parsers.model.MangaSource
+
+class StubContentCache : ContentCache {
+
+	override suspend fun getDetails(source: MangaSource, url: String): Manga? = null
+
+	override fun putDetails(source: MangaSource, url: String, details: Deferred<Manga>) = Unit
+
+	override suspend fun getPages(source: MangaSource, url: String): List<MangaPage>? = null
+
+	override fun putPages(source: MangaSource, url: String, pages: Deferred<List<MangaPage>>) = Unit
+}

app/src/main/java/org/koitharu/kotatsu/core/parser/MangaRepository.kt

@@ -1,13 +1,19 @@
 package org.koitharu.kotatsu.core.parser
 
+import org.koitharu.kotatsu.core.cache.ContentCache
+import org.koitharu.kotatsu.local.domain.LocalMangaRepository
+import org.koitharu.kotatsu.parsers.MangaLoaderContext
+import org.koitharu.kotatsu.parsers.model.Manga
+import org.koitharu.kotatsu.parsers.model.MangaChapter
+import org.koitharu.kotatsu.parsers.model.MangaPage
+import org.koitharu.kotatsu.parsers.model.MangaSource
+import org.koitharu.kotatsu.parsers.model.MangaTag
+import org.koitharu.kotatsu.parsers.model.SortOrder
 import java.lang.ref.WeakReference
-import java.util.*
+import java.util.EnumMap
 import javax.inject.Inject
 import javax.inject.Singleton
 import kotlin.collections.set
-import org.koitharu.kotatsu.local.domain.LocalMangaRepository
-import org.koitharu.kotatsu.parsers.MangaLoaderContext
-import org.koitharu.kotatsu.parsers.model.*
 
 interface MangaRepository {
 
@@ -31,6 +37,7 @@ interface MangaRepository {
 	class Factory @Inject constructor(
 		private val localMangaRepository: LocalMangaRepository,
 		private val loaderContext: MangaLoaderContext,
+		private val contentCache: ContentCache,
 	) {
 
 		private val cache = EnumMap<MangaSource, WeakReference<RemoteMangaRepository>>(MangaSource::class.java)
@@ -42,7 +49,7 @@ interface MangaRepository {
 			cache[source]?.get()?.let { return it }
 			return synchronized(cache) {
 				cache[source]?.get()?.let { return it }
-				val repository = RemoteMangaRepository(MangaParser(source, loaderContext))
+				val repository = RemoteMangaRepository(MangaParser(source, loaderContext), contentCache)
 				cache[source] = WeakReference(repository)
 				repository
 			}

app/src/main/java/org/koitharu/kotatsu/core/parser/RemoteMangaRepository.kt

@@ -1,12 +1,24 @@
 package org.koitharu.kotatsu.core.parser
 
+import kotlinx.coroutines.async
+import kotlinx.coroutines.coroutineScope
+import org.koitharu.kotatsu.core.cache.ContentCache
 import org.koitharu.kotatsu.core.prefs.SourceSettings
 import org.koitharu.kotatsu.parsers.MangaParser
 import org.koitharu.kotatsu.parsers.MangaParserAuthProvider
 import org.koitharu.kotatsu.parsers.config.ConfigKey
-import org.koitharu.kotatsu.parsers.model.*
+import org.koitharu.kotatsu.parsers.model.Favicons
+import org.koitharu.kotatsu.parsers.model.Manga
+import org.koitharu.kotatsu.parsers.model.MangaChapter
+import org.koitharu.kotatsu.parsers.model.MangaPage
+import org.koitharu.kotatsu.parsers.model.MangaSource
+import org.koitharu.kotatsu.parsers.model.MangaTag
+import org.koitharu.kotatsu.parsers.model.SortOrder
 
-class RemoteMangaRepository(private val parser: MangaParser) : MangaRepository {
+class RemoteMangaRepository(
+	private val parser: MangaParser,
+	private val cache: ContentCache,
+) : MangaRepository {
 
 	override val source: MangaSource
 		get() = parser.source
@@ -28,9 +40,23 @@ class RemoteMangaRepository(private val parser: MangaParser) : MangaRepository {
 		return parser.getList(offset, tags, sortOrder)
 	}
 
-	override suspend fun getDetails(manga: Manga): Manga = parser.getDetails(manga)
+	override suspend fun getDetails(manga: Manga): Manga {
+		cache.getDetails(source, manga.url)?.let { return it }
+		return coroutineScope {
+			val details = async { parser.getDetails(manga) }
+			cache.putDetails(source, manga.url, details)
+			details
+		}.await()
+	}
 
-	override suspend fun getPages(chapter: MangaChapter): List<MangaPage> = parser.getPages(chapter)
+	override suspend fun getPages(chapter: MangaChapter): List<MangaPage> {
+		cache.getPages(source, chapter.url)?.let { return it }
+		return coroutineScope {
+			val pages = async { parser.getPages(chapter) }
+			cache.putPages(source, chapter.url, pages)
+			pages
+		}.await()
+	}
 
 	override suspend fun getPageUrl(page: MangaPage): String = parser.getPageUrl(page)
 

app/src/main/java/org/koitharu/kotatsu/details/service/MangaPrefetchService.kt

@@ -0,0 +1,96 @@
+package org.koitharu.kotatsu.details.service
+
+import android.content.Context
+import android.content.Intent
+import dagger.hilt.android.AndroidEntryPoint
+import dagger.hilt.android.EntryPointAccessors
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.launch
+import org.koitharu.kotatsu.base.ui.CoroutineIntentService
+import org.koitharu.kotatsu.core.cache.ContentCache
+import org.koitharu.kotatsu.core.cache.StubContentCache
+import org.koitharu.kotatsu.core.model.parcelable.ParcelableManga
+import org.koitharu.kotatsu.core.model.parcelable.ParcelableMangaChapters
+import org.koitharu.kotatsu.core.parser.MangaRepository
+import org.koitharu.kotatsu.parsers.model.Manga
+import org.koitharu.kotatsu.parsers.model.MangaChapter
+import org.koitharu.kotatsu.parsers.model.MangaSource
+import org.koitharu.kotatsu.utils.ext.getParcelableExtraCompat
+import org.koitharu.kotatsu.utils.ext.processLifecycleScope
+import org.koitharu.kotatsu.utils.ext.runCatchingCancellable
+import javax.inject.Inject
+
+@AndroidEntryPoint
+class MangaPrefetchService : CoroutineIntentService() {
+
+	@Inject
+	lateinit var mangaRepositoryFactory: MangaRepository.Factory
+
+	@Inject
+	lateinit var cache: ContentCache
+
+	override suspend fun processIntent(startId: Int, intent: Intent) {
+		when (intent.action) {
+			ACTION_PREFETCH_DETAILS -> prefetchDetails(
+				manga = intent.getParcelableExtraCompat<ParcelableManga>(EXTRA_MANGA)?.manga ?: return,
+			)
+
+			ACTION_PREFETCH_PAGES -> prefetchPages(
+				chapter = intent.getParcelableExtraCompat<ParcelableMangaChapters>(EXTRA_CHAPTER)
+					?.chapters?.singleOrNull() ?: return,
+			)
+		}
+	}
+
+	override fun onError(startId: Int, error: Throwable) = Unit
+
+	private suspend fun prefetchDetails(manga: Manga) = coroutineScope {
+		val source = mangaRepositoryFactory.create(manga.source)
+		processLifecycleScope.launch(Dispatchers.Default) {
+			runCatchingCancellable { source.getDetails(manga) }
+		}.join()
+	}
+
+	private suspend fun prefetchPages(chapter: MangaChapter) {
+		val source = mangaRepositoryFactory.create(chapter.source)
+		processLifecycleScope.launch(Dispatchers.Default) {
+			runCatchingCancellable { source.getPages(chapter) }
+		}.join()
+	}
+
+	companion object {
+
+		private const val EXTRA_MANGA = "manga"
+		private const val EXTRA_CHAPTER = "manga"
+		private const val ACTION_PREFETCH_DETAILS = "details"
+		private const val ACTION_PREFETCH_PAGES = "pages"
+
+		fun prefetchDetails(context: Context, manga: Manga) {
+			if (!isPrefetchAvailable(context, manga.source)) return
+			val intent = Intent(context, MangaPrefetchService::class.java)
+			intent.action = ACTION_PREFETCH_DETAILS
+			intent.putExtra(EXTRA_MANGA, ParcelableManga(manga, withChapters = false))
+			context.startService(intent)
+		}
+
+		fun prefetchPages(context: Context, chapter: MangaChapter) {
+			if (!isPrefetchAvailable(context, chapter.source)) return
+			val intent = Intent(context, MangaPrefetchService::class.java)
+			intent.action = ACTION_PREFETCH_PAGES
+			intent.putExtra(EXTRA_CHAPTER, ParcelableMangaChapters(listOf(chapter)))
+			context.startService(intent)
+		}
+
+		private fun isPrefetchAvailable(context: Context, source: MangaSource): Boolean {
+			if (source == MangaSource.LOCAL) {
+				return false
+			}
+			val entryPoint = EntryPointAccessors.fromApplication(context, PrefetchCompanionEntryPoint::class.java)
+			if (entryPoint.contentCache is StubContentCache) {
+				return false
+			}
+			return true
+		}
+	}
+}

app/src/main/java/org/koitharu/kotatsu/details/service/PrefetchCompanionEntryPoint.kt

@@ -0,0 +1,14 @@
+package org.koitharu.kotatsu.details.service
+
+import dagger.hilt.EntryPoint
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+import org.koitharu.kotatsu.core.cache.ContentCache
+import org.koitharu.kotatsu.core.prefs.AppSettings
+
+@EntryPoint
+@InstallIn(SingletonComponent::class)
+interface PrefetchCompanionEntryPoint {
+	val settings: AppSettings
+	val contentCache: ContentCache
+}

app/src/main/java/org/koitharu/kotatsu/details/ui/DetailsActivity.kt

@@ -18,6 +18,7 @@ import androidx.core.graphics.Insets
 import androidx.core.view.isGone
 import androidx.core.view.isVisible
 import androidx.core.view.updatePadding
+import androidx.lifecycle.Observer
 import androidx.lifecycle.lifecycleScope
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
 import com.google.android.material.snackbar.BaseTransientBottomBar
@@ -33,6 +34,8 @@ import org.koitharu.kotatsu.core.model.parcelable.ParcelableManga
 import org.koitharu.kotatsu.core.os.ShortcutsUpdater
 import org.koitharu.kotatsu.core.ui.MangaErrorDialog
 import org.koitharu.kotatsu.databinding.ActivityDetailsBinding
+import org.koitharu.kotatsu.details.service.MangaPrefetchService
+import org.koitharu.kotatsu.details.ui.model.ChapterListItem
 import org.koitharu.kotatsu.details.ui.model.HistoryInfo
 import org.koitharu.kotatsu.download.ui.service.DownloadService
 import org.koitharu.kotatsu.main.ui.owners.NoModalBottomSheetOwner
@@ -120,6 +123,7 @@ class DetailsActivity :
 		viewModel.branches.observe(this) {
 			binding.buttonDropdown.isVisible = it.size > 1
 		}
+		viewModel.chapters.observe(this, PrefetchObserver(this))
 
 		registerReceiver(downloadReceiver, IntentFilter(DownloadService.ACTION_DOWNLOAD_COMPLETE))
 		addMenuProvider(
@@ -325,6 +329,24 @@ class DetailsActivity :
 		return sb
 	}
 
+	private class PrefetchObserver(
+		private val context: Context,
+	) : Observer<List<ChapterListItem>> {
+
+		private var isCalled = false
+
+		override fun onChanged(t: List<ChapterListItem>?) {
+			if (t.isNullOrEmpty()) {
+				return
+			}
+			if (!isCalled) {
+				isCalled = true
+				val item = t.find { it.hasFlag(ChapterListItem.FLAG_CURRENT) } ?: t.first()
+				MangaPrefetchService.prefetchPages(context, item.chapter)
+			}
+		}
+	}
+
 	companion object {
 
 		fun newIntent(context: Context, manga: Manga): Intent {