Improve loading both local and remote manga

app/src/main/kotlin/org/koitharu/kotatsu/details/domain/DoubleMangaLoadUseCase.kt

@@ -1,8 +1,11 @@
 package org.koitharu.kotatsu.details.domain
 
 import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.async
-import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.flatMapLatest
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.flowOn
 import org.koitharu.kotatsu.core.model.isLocal
 import org.koitharu.kotatsu.core.parser.MangaDataRepository
 import org.koitharu.kotatsu.core.parser.MangaIntent
@@ -23,24 +26,28 @@ class DoubleMangaLoadUseCase @Inject constructor(
 	private val recoverUseCase: RecoverMangaUseCase,
 ) {
 
-	suspend operator fun invoke(manga: Manga): DoubleManga = coroutineScope {
-		val remoteDeferred = async(Dispatchers.Default) { loadRemote(manga) }
-		val localDeferred = async(Dispatchers.Default) { loadLocal(manga) }
-		DoubleManga(
-			remoteManga = remoteDeferred.await(),
-			localManga = localDeferred.await(),
-		)
-	}
+	operator fun invoke(manga: Manga): Flow<DoubleManga> = flow<DoubleManga> {
+		var lastValue: DoubleManga? = null
+		var emitted = false
+		invokeImpl(manga).collect {
+			lastValue = it
+			if (it.any != null) {
+				emitted = true
+				emit(it)
+			}
+		}
+		if (!emitted) {
+			lastValue?.requireAny()
+		}
+	}.flowOn(Dispatchers.Default)
 
-	suspend operator fun invoke(mangaId: Long): DoubleManga {
-		val manga = mangaDataRepository.findMangaById(mangaId) ?: throwNFE()
-		return invoke(manga)
-	}
+	operator fun invoke(mangaId: Long): Flow<DoubleManga> = flow {
+		emit(mangaDataRepository.findMangaById(mangaId) ?: throwNFE())
+	}.flatMapLatest { invoke(it) }
 
-	suspend operator fun invoke(intent: MangaIntent): DoubleManga {
-		val manga = mangaDataRepository.resolveIntent(intent) ?: throwNFE()
-		return invoke(manga)
-	}
+	operator fun invoke(intent: MangaIntent): Flow<DoubleManga> = flow {
+		emit(mangaDataRepository.resolveIntent(intent) ?: throwNFE())
+	}.flatMapLatest { invoke(it) }
 
 	private suspend fun loadLocal(manga: Manga): Result<Manga>? {
 		return runCatchingCancellable {
@@ -70,5 +77,15 @@ class DoubleMangaLoadUseCase @Inject constructor(
 		}
 	}
 
+	private fun invokeImpl(manga: Manga): Flow<DoubleManga> = combine(
+		flow { emit(null); emit(loadRemote(manga)) },
+		flow { emit(null); emit(loadLocal(manga)) },
+	) { remote, local ->
+		DoubleManga(
+			remoteManga = remote,
+			localManga = local,
+		)
+	}
+
 	private fun throwNFE(): Nothing = throw NotFoundException("Cannot find manga", "")
 }

app/src/main/kotlin/org/koitharu/kotatsu/details/domain/model/DoubleManga.kt

@@ -1,5 +1,6 @@
 package org.koitharu.kotatsu.details.domain.model
 
+import org.koitharu.kotatsu.core.model.findById
 import org.koitharu.kotatsu.parsers.model.Manga
 import org.koitharu.kotatsu.parsers.model.MangaChapter
 import org.koitharu.kotatsu.parsers.model.MangaSource
@@ -34,6 +35,10 @@ data class DoubleManga(
 		mergeChapters()
 	}
 
+	fun hasChapter(id: Long): Boolean {
+		return local?.chapters?.findById(id) != null || remote?.chapters?.findById(id) != null
+	}
+
 	fun requireAny(): Manga {
 		val result = remoteManga?.getOrNull() ?: localManga?.getOrNull()
 		if (result != null) {

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

@@ -5,6 +5,7 @@ import android.content.Intent
 import dagger.hilt.android.AndroidEntryPoint
 import dagger.hilt.android.EntryPointAccessors
 import org.koitharu.kotatsu.core.cache.ContentCache
+import org.koitharu.kotatsu.core.model.findById
 import org.koitharu.kotatsu.core.model.parcelable.ParcelableChapter
 import org.koitharu.kotatsu.core.model.parcelable.ParcelableManga
 import org.koitharu.kotatsu.core.parser.MangaRepository
@@ -72,7 +73,7 @@ class MangaPrefetchService : CoroutineIntentService() {
 		val chapter = if (history == null) {
 			chapters.firstOrNull()
 		} else {
-			chapters.find { x -> x.id == history.chapterId } ?: chapters.firstOrNull()
+			chapters.findById(history.chapterId) ?: chapters.firstOrNull()
 		} ?: return
 		runCatchingCancellable { repo.getPages(chapter) }
 	}
@@ -122,7 +123,7 @@ class MangaPrefetchService : CoroutineIntentService() {
 			}
 			val entryPoint = EntryPointAccessors.fromApplication(
 				context,
-				PrefetchCompanionEntryPoint::class.java
+				PrefetchCompanionEntryPoint::class.java,
 			)
 			return entryPoint.contentCache.isCachingEnabled && entryPoint.settings.isContentPrefetchEnabled
 		}

app/src/main/kotlin/org/koitharu/kotatsu/details/ui/DetailsFragment.kt

@@ -43,6 +43,7 @@ import org.koitharu.kotatsu.core.util.ext.observe
 import org.koitharu.kotatsu.core.util.ext.parentView
 import org.koitharu.kotatsu.core.util.ext.resolveDp
 import org.koitharu.kotatsu.core.util.ext.scaleUpActivityOptionsOf
+import org.koitharu.kotatsu.core.util.ext.showOrHide
 import org.koitharu.kotatsu.core.util.ext.textAndVisible
 import org.koitharu.kotatsu.databinding.FragmentDetailsBinding
 import org.koitharu.kotatsu.details.ui.model.ChapterListItem
@@ -247,11 +248,7 @@ class DetailsFragment :
 	}
 
 	private fun onLoadingStateChanged(isLoading: Boolean) {
-		if (isLoading) {
-			requireViewBinding().progressBar.show()
-		} else {
-			requireViewBinding().progressBar.hide()
-		}
+		requireViewBinding().progressBar.showOrHide(isLoading)
 	}
 
 	private fun onBookmarksChanged(bookmarks: List<Bookmark>) {

app/src/main/kotlin/org/koitharu/kotatsu/details/ui/DetailsViewModel.kt

@@ -42,6 +42,7 @@ import org.koitharu.kotatsu.core.util.ext.MutableEventFlow
 import org.koitharu.kotatsu.core.util.ext.call
 import org.koitharu.kotatsu.core.util.ext.combine
 import org.koitharu.kotatsu.core.util.ext.computeSize
+import org.koitharu.kotatsu.core.util.ext.onFirst
 import org.koitharu.kotatsu.core.util.ext.requireValue
 import org.koitharu.kotatsu.core.util.ext.sanitize
 import org.koitharu.kotatsu.core.util.ext.toFileOrNull
@@ -87,7 +88,8 @@ class DetailsViewModel @Inject constructor(
 
 	private val intent = MangaIntent(savedStateHandle)
 	private val mangaId = intent.mangaId
-	private val doubleManga: MutableStateFlow<DoubleManga?> = MutableStateFlow(intent.manga?.let { DoubleManga(it) })
+	private val doubleManga: MutableStateFlow<DoubleManga?> =
+		MutableStateFlow(intent.manga?.let { DoubleManga(it) })
 	private var loadingJob: Job
 
 	val onShowToast = MutableEventFlow<Int>()
@@ -202,7 +204,14 @@ class DetailsViewModel @Inject constructor(
 			bookmarks,
 			networkState,
 		) { manga, history, branch, news, bookmarks, isOnline ->
-			mapChapters(manga?.remote?.takeIf { isOnline }, manga?.local, history, news, branch, bookmarks)
+			mapChapters(
+				manga?.remote?.takeIf { isOnline },
+				manga?.local,
+				history,
+				news,
+				branch,
+				bookmarks,
+			)
 		},
 		isChaptersReversed,
 		chaptersQuery,
@@ -324,12 +333,15 @@ class DetailsViewModel @Inject constructor(
 	}
 
 	private fun doLoad() = launchLoadingJob(Dispatchers.Default) {
-		val result = doubleMangaLoadUseCase(intent)
-		val manga = result.requireAny()
-		// find default branch
-		val hist = historyRepository.getOne(manga)
-		selectedBranch.value = manga.getPreferredBranch(hist)
-		doubleManga.value = result
+		doubleMangaLoadUseCase.invoke(intent)
+			.onFirst {
+				val manga = it.requireAny()
+				// find default branch
+				val hist = historyRepository.getOne(manga)
+				selectedBranch.value = manga.getPreferredBranch(hist)
+			}.collect {
+				doubleManga.value = it
+			}
 	}
 
 	private fun List<ChapterListItem>.filterSearch(query: String): List<ChapterListItem> {