Manga migration feature

app/src/main/AndroidManifest.xml

@@ -242,6 +242,9 @@
 		<activity
 			android:name="org.koitharu.kotatsu.stats.ui.StatsActivity"
 			android:label="@string/reading_stats" />
+		<activity
+			android:name="org.koitharu.kotatsu.alternatives.ui.AlternativesActivity"
+			android:label="@string/alternatives" />
 
 		<service
 			android:name="androidx.work.impl.foreground.SystemForegroundService"

app/src/main/kotlin/org/koitharu/kotatsu/alternatives/domain/AlternativesUseCase.kt

@@ -0,0 +1,69 @@
+package org.koitharu.kotatsu.alternatives.domain
+
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.channelFlow
+import kotlinx.coroutines.flow.emptyFlow
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.sync.Semaphore
+import kotlinx.coroutines.sync.withPermit
+import org.koitharu.kotatsu.core.parser.MangaRepository
+import org.koitharu.kotatsu.core.util.ext.almostEquals
+import org.koitharu.kotatsu.explore.data.MangaSourcesRepository
+import org.koitharu.kotatsu.parsers.model.Manga
+import org.koitharu.kotatsu.parsers.model.MangaListFilter
+import org.koitharu.kotatsu.parsers.util.runCatchingCancellable
+import javax.inject.Inject
+
+private const val MAX_PARALLELISM = 4
+private const val MATCH_THRESHOLD = 0.2f
+
+class AlternativesUseCase @Inject constructor(
+	private val sourcesRepository: MangaSourcesRepository,
+	private val mangaRepositoryFactory: MangaRepository.Factory,
+) {
+
+	suspend operator fun invoke(manga: Manga): Flow<Manga> {
+		val sources = sourcesRepository.getEnabledSources()
+		if (sources.isEmpty()) {
+			return emptyFlow()
+		}
+		val semaphore = Semaphore(MAX_PARALLELISM)
+		return channelFlow {
+			for (source in sources) {
+				val repository = mangaRepositoryFactory.create(source)
+				if (!repository.isSearchSupported) {
+					continue
+				}
+				launch {
+					val list = runCatchingCancellable {
+						semaphore.withPermit {
+							repository.getList(offset = 0, filter = MangaListFilter.Search(manga.title))
+						}
+					}.getOrDefault(emptyList())
+					for (item in list) {
+						if (item != manga && item.matches(manga)) {
+							send(item)
+						}
+					}
+				}
+			}
+		}.map {
+			runCatchingCancellable {
+				mangaRepositoryFactory.create(it.source).getDetails(it)
+			}.getOrDefault(it)
+		}
+	}
+
+	private fun Manga.matches(ref: Manga): Boolean {
+		return matchesTitles(title, ref.title) ||
+			matchesTitles(title, ref.altTitle) ||
+			matchesTitles(altTitle, ref.title) ||
+			matchesTitles(altTitle, ref.altTitle)
+
+	}
+
+	private fun matchesTitles(a: String?, b: String?): Boolean {
+		return !a.isNullOrEmpty() && !b.isNullOrEmpty() && a.almostEquals(b, MATCH_THRESHOLD)
+	}
+}

app/src/main/kotlin/org/koitharu/kotatsu/alternatives/domain/MigrateUseCase.kt

@@ -0,0 +1,127 @@
+package org.koitharu.kotatsu.alternatives.domain
+
+import androidx.room.withTransaction
+import org.koitharu.kotatsu.core.db.MangaDatabase
+import org.koitharu.kotatsu.core.model.getPreferredBranch
+import org.koitharu.kotatsu.core.parser.MangaDataRepository
+import org.koitharu.kotatsu.core.parser.MangaRepository
+import org.koitharu.kotatsu.details.domain.DetailsLoadUseCase
+import org.koitharu.kotatsu.details.domain.ProgressUpdateUseCase
+import org.koitharu.kotatsu.favourites.data.FavouriteEntity
+import org.koitharu.kotatsu.history.data.HistoryEntity
+import org.koitharu.kotatsu.history.data.PROGRESS_NONE
+import org.koitharu.kotatsu.history.data.toMangaHistory
+import org.koitharu.kotatsu.parsers.model.Manga
+import org.koitharu.kotatsu.parsers.model.MangaChapter
+import org.koitharu.kotatsu.parsers.util.runCatchingCancellable
+import javax.inject.Inject
+
+class MigrateUseCase @Inject constructor(
+	private val mangaRepositoryFactory: MangaRepository.Factory,
+	private val mangaDataRepository: MangaDataRepository,
+	private val database: MangaDatabase,
+	private val progressUpdateUseCase: ProgressUpdateUseCase,
+	private val useCase: DetailsLoadUseCase
+) {
+
+	suspend operator fun invoke(oldManga: Manga, newManga: Manga) {
+		val oldDetails = if (oldManga.chapters.isNullOrEmpty()) {
+			runCatchingCancellable {
+				mangaRepositoryFactory.create(oldManga.source).getDetails(oldManga)
+			}.getOrDefault(oldManga)
+		} else {
+			oldManga
+		}
+		val newDetails = if (newManga.chapters.isNullOrEmpty()) {
+			mangaRepositoryFactory.create(newManga.source).getDetails(newManga)
+		} else {
+			newManga
+		}
+		mangaDataRepository.storeManga(newDetails)
+		database.withTransaction {
+			// replace favorites
+			val favoritesDao = database.getFavouritesDao()
+			val oldFavourite = favoritesDao.find(oldDetails.id)
+			if (oldFavourite != null) {
+				favoritesDao.delete(oldManga.id)
+				for (f in oldFavourite.categories) {
+					val e = FavouriteEntity(
+						mangaId = newManga.id,
+						categoryId = f.categoryId.toLong(),
+						sortKey = f.sortKey,
+						createdAt = f.createdAt,
+						deletedAt = 0,
+					)
+					favoritesDao.upsert(e)
+				}
+			}
+			// replace history
+			val historyDao = database.getHistoryDao()
+			val oldHistory = historyDao.find(oldDetails.id)
+			if (oldHistory != null) {
+				val newHistory = makeNewHistory(oldDetails, newDetails, oldHistory)
+				historyDao.delete(oldDetails.id)
+				historyDao.upsert(newHistory)
+			}
+		}
+		progressUpdateUseCase(newManga)
+	}
+
+	private fun makeNewHistory(
+		oldManga: Manga,
+		newManga: Manga,
+		history: HistoryEntity,
+	): HistoryEntity {
+		if (oldManga.chapters.isNullOrEmpty()) { // probably broken manga/source
+			val branch = newManga.getPreferredBranch(null)
+			val chapters = checkNotNull(newManga.getChapters(branch))
+			return HistoryEntity(
+				mangaId = newManga.id,
+				createdAt = history.createdAt,
+				updatedAt = System.currentTimeMillis(),
+				chapterId = chapters[(chapters.lastIndex * history.percent).toInt()].id,
+				page = history.page,
+				scroll = history.scroll,
+				percent = history.percent,
+				deletedAt = 0,
+				chaptersCount = chapters.size,
+			)
+		}
+		val branch = oldManga.getPreferredBranch(history.toMangaHistory())
+		val oldChapters = checkNotNull(oldManga.getChapters(branch))
+		var index = oldChapters.indexOfFirst { it.id == history.chapterId }
+		if (index < 0) {
+			index = (oldChapters.size * history.percent).toInt()
+		}
+		val newChapters = checkNotNull(newManga.chapters).groupBy { it.branch }
+		val newBranch = if (newChapters.containsKey(branch)) {
+			branch
+		} else {
+			newManga.getPreferredBranch(null)
+		}
+		val newChapterId = checkNotNull(newChapters[newBranch]).let {
+			val oldChapter = oldChapters[index]
+			it.findByNumber(oldChapter.volume, oldChapter.number) ?: it.getOrNull(index) ?: it.last()
+		}.id
+
+		return HistoryEntity(
+			mangaId = newManga.id,
+			createdAt = history.createdAt,
+			updatedAt = System.currentTimeMillis(),
+			chapterId = newChapterId,
+			page = history.page,
+			scroll = history.scroll,
+			percent = PROGRESS_NONE,
+			deletedAt = 0,
+			chaptersCount = checkNotNull(newChapters[newBranch]).size,
+		)
+	}
+
+	private fun List<MangaChapter>.findByNumber(volume: Int, number: Float): MangaChapter? {
+		return if (number <= 0f) {
+			null
+		} else {
+			firstOrNull { it.volume == volume && it.number == number }
+		}
+	}
+}

app/src/main/kotlin/org/koitharu/kotatsu/alternatives/ui/AlternativeAD.kt

@@ -0,0 +1,88 @@
+package org.koitharu.kotatsu.alternatives.ui
+
+import android.text.style.ForegroundColorSpan
+import androidx.core.content.ContextCompat
+import androidx.core.text.buildSpannedString
+import androidx.core.text.inSpans
+import androidx.lifecycle.LifecycleOwner
+import coil.ImageLoader
+import coil.request.ImageRequest
+import coil.transform.CircleCropTransformation
+import com.hannesdorfmann.adapterdelegates4.dsl.adapterDelegateViewBinding
+import org.koitharu.kotatsu.R
+import org.koitharu.kotatsu.core.parser.favicon.faviconUri
+import org.koitharu.kotatsu.core.ui.image.ChipIconTarget
+import org.koitharu.kotatsu.core.ui.image.CoverSizeResolver
+import org.koitharu.kotatsu.core.ui.image.TrimTransformation
+import org.koitharu.kotatsu.core.ui.list.AdapterDelegateClickListenerAdapter
+import org.koitharu.kotatsu.core.ui.list.OnListItemClickListener
+import org.koitharu.kotatsu.core.util.ext.enqueueWith
+import org.koitharu.kotatsu.core.util.ext.newImageRequest
+import org.koitharu.kotatsu.core.util.ext.source
+import org.koitharu.kotatsu.databinding.ItemMangaAlternativeBinding
+import org.koitharu.kotatsu.list.ui.ListModelDiffCallback
+import org.koitharu.kotatsu.list.ui.model.ListModel
+import kotlin.math.sign
+import com.google.android.material.R as materialR
+
+fun alternativeAD(
+	coil: ImageLoader,
+	lifecycleOwner: LifecycleOwner,
+	listener: OnListItemClickListener<MangaAlternativeModel>,
+) = adapterDelegateViewBinding<MangaAlternativeModel, ListModel, ItemMangaAlternativeBinding>(
+	{ inflater, parent -> ItemMangaAlternativeBinding.inflate(inflater, parent, false) },
+) {
+
+	val colorGreen = ContextCompat.getColor(context, R.color.common_green)
+	val colorRed = ContextCompat.getColor(context, R.color.common_red)
+	val clickListener = AdapterDelegateClickListenerAdapter(this, listener)
+	itemView.setOnClickListener(clickListener)
+	binding.buttonMigrate.setOnClickListener(clickListener)
+	binding.chipSource.setOnClickListener(clickListener)
+
+	bind { payloads ->
+		binding.textViewTitle.text = item.manga.title
+		binding.textViewSubtitle.text = buildSpannedString {
+			append(context.resources.getQuantityString(R.plurals.chapters, item.chaptersCount, item.chaptersCount))
+			when (item.chaptersDiff.sign) {
+				-1 -> inSpans(ForegroundColorSpan(colorRed)) {
+					append("  ▼ ")
+					append(item.chaptersDiff.toString())
+				}
+
+				1 -> inSpans(ForegroundColorSpan(colorGreen)) {
+					append("  ▲ +")
+					append(item.chaptersDiff.toString())
+				}
+			}
+		}
+		binding.progressView.setPercent(item.progress, ListModelDiffCallback.PAYLOAD_PROGRESS_CHANGED in payloads)
+		binding.chipSource.also { chip ->
+			chip.text = item.manga.source.title
+			ImageRequest.Builder(context)
+				.data(item.manga.source.faviconUri())
+				.lifecycle(lifecycleOwner)
+				.crossfade(false)
+				.size(context.resources.getDimensionPixelSize(materialR.dimen.m3_chip_icon_size))
+				.target(ChipIconTarget(chip))
+				.placeholder(R.drawable.ic_web)
+				.fallback(R.drawable.ic_web)
+				.error(R.drawable.ic_web)
+				.source(item.manga.source)
+				.transformations(CircleCropTransformation())
+				.allowRgb565(true)
+				.enqueueWith(coil)
+		}
+		binding.imageViewCover.newImageRequest(lifecycleOwner, item.manga.coverUrl)?.run {
+			size(CoverSizeResolver(binding.imageViewCover))
+			placeholder(R.drawable.ic_placeholder)
+			fallback(R.drawable.ic_placeholder)
+			error(R.drawable.ic_error_placeholder)
+			transformations(TrimTransformation())
+			allowRgb565(true)
+			tag(item.manga)
+			source(item.manga.source)
+			enqueueWith(coil)
+		}
+	}
+}

app/src/main/kotlin/org/koitharu/kotatsu/alternatives/ui/AlternativesActivity.kt

@@ -0,0 +1,114 @@
+package org.koitharu.kotatsu.alternatives.ui
+
+import android.content.Context
+import android.content.Intent
+import android.os.Bundle
+import android.view.View
+import android.widget.Toast
+import androidx.activity.viewModels
+import androidx.core.graphics.Insets
+import androidx.core.view.updatePadding
+import coil.ImageLoader
+import com.google.android.material.dialog.MaterialAlertDialogBuilder
+import dagger.hilt.android.AndroidEntryPoint
+import org.koitharu.kotatsu.R
+import org.koitharu.kotatsu.core.exceptions.resolve.SnackbarErrorObserver
+import org.koitharu.kotatsu.core.model.parcelable.ParcelableManga
+import org.koitharu.kotatsu.core.parser.MangaIntent
+import org.koitharu.kotatsu.core.ui.BaseActivity
+import org.koitharu.kotatsu.core.ui.BaseListAdapter
+import org.koitharu.kotatsu.core.ui.list.OnListItemClickListener
+import org.koitharu.kotatsu.core.util.ext.DIALOG_THEME_CENTERED
+import org.koitharu.kotatsu.core.util.ext.observe
+import org.koitharu.kotatsu.core.util.ext.observeEvent
+import org.koitharu.kotatsu.databinding.ActivityAlternativesBinding
+import org.koitharu.kotatsu.details.ui.DetailsActivity
+import org.koitharu.kotatsu.list.ui.adapter.ListItemType
+import org.koitharu.kotatsu.list.ui.adapter.TypedListSpacingDecoration
+import org.koitharu.kotatsu.list.ui.adapter.emptyStateListAD
+import org.koitharu.kotatsu.list.ui.adapter.loadingFooterAD
+import org.koitharu.kotatsu.list.ui.adapter.loadingStateAD
+import org.koitharu.kotatsu.list.ui.model.ListModel
+import org.koitharu.kotatsu.parsers.model.Manga
+import org.koitharu.kotatsu.search.ui.SearchActivity
+import javax.inject.Inject
+
+@AndroidEntryPoint
+class AlternativesActivity : BaseActivity<ActivityAlternativesBinding>(),
+	OnListItemClickListener<MangaAlternativeModel> {
+
+	@Inject
+	lateinit var coil: ImageLoader
+
+	private val viewModel by viewModels<AlternativesViewModel>()
+
+	override fun onCreate(savedInstanceState: Bundle?) {
+		super.onCreate(savedInstanceState)
+		setContentView(ActivityAlternativesBinding.inflate(layoutInflater))
+		supportActionBar?.run {
+			setDisplayHomeAsUpEnabled(true)
+			subtitle = viewModel.manga.title
+		}
+		val listAdapter = BaseListAdapter<ListModel>()
+			.addDelegate(ListItemType.MANGA_LIST_DETAILED, alternativeAD(coil, this, this))
+			.addDelegate(ListItemType.STATE_EMPTY, emptyStateListAD(coil, this, null))
+			.addDelegate(ListItemType.FOOTER_LOADING, loadingFooterAD())
+			.addDelegate(ListItemType.STATE_LOADING, loadingStateAD())
+		with(viewBinding.recyclerView) {
+			setHasFixedSize(true)
+			addItemDecoration(TypedListSpacingDecoration(context, addHorizontalPadding = false))
+			adapter = listAdapter
+		}
+
+		viewModel.onError.observeEvent(this, SnackbarErrorObserver(viewBinding.recyclerView, null))
+		viewModel.content.observe(this, listAdapter)
+		viewModel.onMigrated.observeEvent(this) {
+			Toast.makeText(this, R.string.migration_completed, Toast.LENGTH_SHORT).show()
+			startActivity(DetailsActivity.newIntent(this, it))
+			finishAfterTransition()
+		}
+	}
+
+	override fun onWindowInsetsChanged(insets: Insets) {
+		viewBinding.root.updatePadding(
+			left = insets.left,
+			right = insets.right,
+		)
+		viewBinding.recyclerView.updatePadding(
+			bottom = insets.bottom + viewBinding.recyclerView.paddingTop,
+		)
+	}
+
+	override fun onItemClick(item: MangaAlternativeModel, view: View) {
+		when (view.id) {
+			R.id.chip_source -> startActivity(SearchActivity.newIntent(this, item.manga.source, viewModel.manga.title))
+			R.id.button_migrate -> confirmMigration(item.manga)
+			else -> startActivity(DetailsActivity.newIntent(this, item.manga))
+		}
+	}
+
+	private fun confirmMigration(target: Manga) {
+		MaterialAlertDialogBuilder(this, DIALOG_THEME_CENTERED)
+			.setIcon(R.drawable.ic_replace)
+			.setTitle(R.string.manga_migration)
+			.setMessage(
+				getString(
+					R.string.migrate_confirmation,
+					viewModel.manga.title,
+					viewModel.manga.source.title,
+					target.title,
+					target.source.title,
+				),
+			)
+			.setNegativeButton(android.R.string.cancel, null)
+			.setPositiveButton(R.string.migrate) { _, _ ->
+				viewModel.migrate(target)
+			}.show()
+	}
+
+	companion object {
+
+		fun newIntent(context: Context, manga: Manga) = Intent(context, AlternativesActivity::class.java)
+			.putExtra(MangaIntent.KEY_MANGA, ParcelableManga(manga))
+	}
+}

app/src/main/kotlin/org/koitharu/kotatsu/alternatives/ui/AlternativesViewModel.kt

@@ -0,0 +1,94 @@
+package org.koitharu.kotatsu.alternatives.ui
+
+import androidx.lifecycle.SavedStateHandle
+import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.onEmpty
+import kotlinx.coroutines.flow.runningFold
+import org.koitharu.kotatsu.R
+import org.koitharu.kotatsu.alternatives.domain.AlternativesUseCase
+import org.koitharu.kotatsu.alternatives.domain.MigrateUseCase
+import org.koitharu.kotatsu.core.model.chaptersCount
+import org.koitharu.kotatsu.core.model.parcelable.ParcelableManga
+import org.koitharu.kotatsu.core.parser.MangaIntent
+import org.koitharu.kotatsu.core.parser.MangaRepository
+import org.koitharu.kotatsu.core.ui.BaseViewModel
+import org.koitharu.kotatsu.core.util.ext.MutableEventFlow
+import org.koitharu.kotatsu.core.util.ext.call
+import org.koitharu.kotatsu.core.util.ext.require
+import org.koitharu.kotatsu.list.domain.ListExtraProvider
+import org.koitharu.kotatsu.list.ui.model.EmptyState
+import org.koitharu.kotatsu.list.ui.model.ListModel
+import org.koitharu.kotatsu.list.ui.model.LoadingFooter
+import org.koitharu.kotatsu.list.ui.model.LoadingState
+import org.koitharu.kotatsu.parsers.model.Manga
+import javax.inject.Inject
+
+@HiltViewModel
+class AlternativesViewModel @Inject constructor(
+	savedStateHandle: SavedStateHandle,
+	private val mangaRepositoryFactory: MangaRepository.Factory,
+	private val alternativesUseCase: AlternativesUseCase,
+	private val migrateUseCase: MigrateUseCase,
+	private val extraProvider: ListExtraProvider,
+) : BaseViewModel() {
+
+	val manga = savedStateHandle.require<ParcelableManga>(MangaIntent.KEY_MANGA).manga
+
+	val onMigrated = MutableEventFlow<Manga>()
+	val content = MutableStateFlow<List<ListModel>>(listOf(LoadingState))
+	private var migrationJob: Job? = null
+
+	init {
+		launchJob(Dispatchers.Default) {
+			val ref = mangaRepositoryFactory.create(manga.source).getDetails(manga)
+			val refCount = ref.chaptersCount()
+			alternativesUseCase(manga)
+				.map {
+					MangaAlternativeModel(
+						manga = it,
+						progress = extraProvider.getProgress(it.id),
+						referenceChapters = refCount,
+					)
+				}.runningFold<MangaAlternativeModel, List<ListModel>>(listOf(LoadingState)) { acc, item ->
+					acc.filterIsInstance<MangaAlternativeModel>() + item + LoadingFooter()
+				}.onEmpty {
+					emit(
+						listOf(
+							EmptyState(
+								icon = R.drawable.ic_empty_common,
+								textPrimary = R.string.nothing_found,
+								textSecondary = R.string.text_search_holder_secondary,
+								actionStringRes = 0,
+							),
+						),
+					)
+				}.collect {
+					content.value = it
+				}
+		}
+	}
+
+	fun migrate(target: Manga) {
+		if (migrationJob?.isActive == true) {
+			return
+		}
+		migrationJob = launchLoadingJob(Dispatchers.Default) {
+			migrateUseCase(manga, target)
+			onMigrated.call(target)
+		}
+	}
+
+	private suspend fun mapList(list: List<Manga>, refCount: Int): List<MangaAlternativeModel> {
+		return list.map {
+			MangaAlternativeModel(
+				manga = it,
+				progress = extraProvider.getProgress(it.id),
+				referenceChapters = refCount,
+			)
+		}
+	}
+}

app/src/main/kotlin/org/koitharu/kotatsu/alternatives/ui/MangaAlternativeModel.kt

@@ -0,0 +1,21 @@
+package org.koitharu.kotatsu.alternatives.ui
+
+import org.koitharu.kotatsu.core.model.chaptersCount
+import org.koitharu.kotatsu.list.ui.model.ListModel
+import org.koitharu.kotatsu.parsers.model.Manga
+
+data class MangaAlternativeModel(
+	val manga: Manga,
+	val progress: Float,
+	private val referenceChapters: Int,
+) : ListModel {
+
+	val chaptersCount = manga.chaptersCount()
+
+	val chaptersDiff: Int
+		get() = if (referenceChapters == 0 || chaptersCount == 0) 0 else chaptersCount - referenceChapters
+
+	override fun areItemsTheSame(other: ListModel): Boolean {
+		return other is MangaAlternativeModel && other.manga.id == manga.id
+	}
+}

app/src/main/kotlin/org/koitharu/kotatsu/core/model/Manga.kt

@@ -131,3 +131,19 @@ fun MangaChapter.formatNumber(): String? {
 	}
 	return chaptersNumberFormat.format(number.toDouble())
 }
+
+fun Manga.chaptersCount(): Int {
+	if (chapters.isNullOrEmpty()) {
+		return 0
+	}
+	val counters = MutableObjectIntMap<String?>()
+	var max = 0
+	chapters?.forEach { x ->
+		val c = counters.getOrDefault(x.branch, 0) + 1
+		counters[x.branch] = c
+		if (max < c) {
+			max = c
+		}
+	}
+	return max
+}

app/src/main/kotlin/org/koitharu/kotatsu/core/ui/image/ChipIconTarget.kt

@@ -0,0 +1,14 @@
+package org.koitharu.kotatsu.core.ui.image
+
+import android.graphics.drawable.Drawable
+import coil.target.GenericViewTarget
+import com.google.android.material.chip.Chip
+
+class ChipIconTarget(override val view: Chip) : GenericViewTarget<Chip>() {
+
+	override var drawable: Drawable?
+		get() = view.chipIcon
+		set(value) {
+			view.chipIcon = value
+		}
+}

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

@@ -14,6 +14,7 @@ import com.google.android.material.dialog.MaterialAlertDialogBuilder
 import com.google.android.material.snackbar.Snackbar
 import kotlinx.coroutines.launch
 import org.koitharu.kotatsu.R
+import org.koitharu.kotatsu.alternatives.ui.AlternativesActivity
 import org.koitharu.kotatsu.browser.BrowserActivity
 import org.koitharu.kotatsu.core.os.AppShortcutManager
 import org.koitharu.kotatsu.core.ui.list.OnListItemClickListener
@@ -41,6 +42,7 @@ class DetailsMenuProvider(
 		menu.findItem(R.id.action_save).isVisible = manga?.source != null && manga.source != MangaSource.LOCAL
 		menu.findItem(R.id.action_delete).isVisible = manga?.source == MangaSource.LOCAL
 		menu.findItem(R.id.action_browser).isVisible = manga?.source != MangaSource.LOCAL
+		menu.findItem(R.id.action_alternatives).isVisible = manga?.source != MangaSource.LOCAL
 		menu.findItem(R.id.action_shortcut).isVisible = ShortcutManagerCompat.isRequestPinShortcutSupported(activity)
 		menu.findItem(R.id.action_scrobbling).isVisible = viewModel.isScrobblingAvailable
 		menu.findItem(R.id.action_online).isVisible = viewModel.remoteManga.value != null
@@ -103,6 +105,12 @@ class DetailsMenuProvider(
 				}
 			}
 
+			R.id.action_alternatives -> {
+				viewModel.manga.value?.let {
+					activity.startActivity(AlternativesActivity.newIntent(activity, it))
+				}
+			}
+
 			R.id.action_stats -> {
 				viewModel.manga.value?.let {
 					MangaStatsSheet.show(activity.supportFragmentManager, it)

app/src/main/kotlin/org/koitharu/kotatsu/favourites/ui/categories/FavouriteCategoriesActivity.kt

@@ -178,6 +178,7 @@ class FavouriteCategoriesActivity :
 		}
 	}
 
+	@Deprecated("")
 	companion object {
 
 		fun newIntent(context: Context) = Intent(context, FavouriteCategoriesActivity::class.java)

app/src/main/res/drawable/ic_replace.xml

@@ -0,0 +1,11 @@
+<vector
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	android:width="24dp"
+	android:height="24dp"
+	android:tint="?attr/colorControlNormal"
+	android:viewportWidth="24"
+	android:viewportHeight="24">
+	<path
+		android:fillColor="#000"
+		android:pathData="M14,3L12,1H4A2,2 0 0,0 2,3V15A2,2 0 0,0 4,17H11V19L15,16L11,13V15H4V3H14M21,10V21A2,2 0 0,1 19,23H8A2,2 0 0,1 6,21V19H8V21H19V12H14V7H8V13H6V7A2,2 0 0,1 8,5H16L21,10Z" />
+</vector>

app/src/main/res/layout/activity_alternatives.xml

@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.coordinatorlayout.widget.CoordinatorLayout
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent">
+
+	<com.google.android.material.appbar.AppBarLayout
+		android:id="@+id/appbar"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:fitsSystemWindows="true">
+
+		<com.google.android.material.appbar.CollapsingToolbarLayout
+			android:id="@+id/collapsingToolbarLayout"
+			style="?attr/collapsingToolbarLayoutMediumStyle"
+			android:layout_width="match_parent"
+			android:layout_height="?attr/collapsingToolbarLayoutMediumSize"
+			app:layout_scrollFlags="scroll|exitUntilCollapsed|snap"
+			app:toolbarId="@id/toolbar">
+
+			<com.google.android.material.appbar.MaterialToolbar
+				android:id="@id/toolbar"
+				android:layout_width="match_parent"
+				android:layout_height="?attr/actionBarSize"
+				app:layout_collapseMode="pin"
+				tools:title="@string/alternatives" />
+
+		</com.google.android.material.appbar.CollapsingToolbarLayout>
+
+	</com.google.android.material.appbar.AppBarLayout>
+
+	<androidx.recyclerview.widget.RecyclerView
+		android:id="@+id/recyclerView"
+		android:layout_width="match_parent"
+		android:layout_height="match_parent"
+		android:clipToPadding="false"
+		android:orientation="vertical"
+		android:padding="@dimen/list_spacing_normal"
+		android:scrollbars="vertical"
+		app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
+		app:layout_behavior="com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior"
+		tools:listitem="@layout/item_manga_alternative" />
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>

app/src/main/res/layout/item_manga_alternative.xml

@@ -0,0 +1,94 @@
+<?xml version="1.0" encoding="utf-8"?>
+<com.google.android.material.card.MaterialCardView
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:layout_width="match_parent"
+	android:layout_height="wrap_content"
+	app:cardCornerRadius="16dp">
+
+	<androidx.constraintlayout.widget.ConstraintLayout
+		android:layout_width="match_parent"
+		android:layout_height="match_parent">
+
+		<com.google.android.material.imageview.ShapeableImageView
+			android:id="@+id/imageView_cover"
+			android:layout_width="98dp"
+			android:layout_height="0dp"
+			android:background="?colorSurfaceContainer"
+			android:scaleType="centerCrop"
+			app:layout_constraintDimensionRatio="13:18"
+			app:layout_constraintStart_toStartOf="parent"
+			app:layout_constraintTop_toTopOf="parent"
+			app:shapeAppearanceOverlay="@style/ShapeAppearanceOverlay.Kotatsu.Cover"
+			tools:src="@tools:sample/backgrounds/scenic" />
+
+		<org.koitharu.kotatsu.history.ui.util.ReadingProgressView
+			android:id="@+id/progressView"
+			android:layout_width="@dimen/card_indicator_size"
+			android:layout_height="@dimen/card_indicator_size"
+			android:layout_margin="@dimen/card_indicator_offset"
+			app:layout_constraintBottom_toBottomOf="@id/imageView_cover"
+			app:layout_constraintEnd_toEndOf="@id/imageView_cover" />
+
+		<TextView
+			android:id="@+id/textView_title"
+			android:layout_width="0dp"
+			android:layout_height="wrap_content"
+			android:layout_marginStart="12dp"
+			android:layout_marginTop="12dp"
+			android:layout_marginEnd="12dp"
+			android:ellipsize="end"
+			android:maxLines="2"
+			android:textAppearance="?attr/textAppearanceTitleMedium"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintStart_toEndOf="@+id/imageView_cover"
+			app:layout_constraintTop_toTopOf="parent"
+			tools:text="@tools:sample/lorem" />
+
+		<TextView
+			android:id="@+id/textView_subtitle"
+			android:layout_width="0dp"
+			android:layout_height="wrap_content"
+			android:layout_marginStart="12dp"
+			android:layout_marginTop="8dp"
+			android:layout_marginEnd="12dp"
+			android:ellipsize="end"
+			android:gravity="center_vertical"
+			android:maxLines="2"
+			android:textAppearance="?attr/textAppearanceBodySmall"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintStart_toEndOf="@+id/imageView_cover"
+			app:layout_constraintTop_toBottomOf="@+id/textView_title"
+			tools:text="@tools:sample/lorem/random" />
+
+		<com.google.android.material.chip.Chip
+			android:id="@+id/chip_source"
+			style="@style/Widget.Kotatsu.Chip.Assist"
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:layout_marginHorizontal="12dp"
+			app:layout_constrainedWidth="true"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintHorizontal_bias="0"
+			app:layout_constraintStart_toEndOf="@+id/imageView_cover"
+			app:layout_constraintTop_toBottomOf="@+id/textView_subtitle"
+			tools:text="Mangadex" />
+
+		<com.google.android.material.button.MaterialButton
+			android:id="@+id/button_migrate"
+			style="@style/Widget.Material3.Button.TonalButton"
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:layout_marginEnd="12dp"
+			android:layout_marginBottom="12dp"
+			android:text="@string/migrate"
+			app:icon="@drawable/ic_replace"
+			app:layout_constraintBottom_toBottomOf="parent"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintTop_toBottomOf="@id/chip_source"
+			app:layout_constraintVertical_bias="1" />
+
+	</androidx.constraintlayout.widget.ConstraintLayout>
+
+</com.google.android.material.card.MaterialCardView>

app/src/main/res/menu/opt_details.xml

@@ -49,6 +49,12 @@
 		android:title="@string/find_similar"
 		app:showAsAction="never" />
 
+	<item
+		android:id="@+id/action_alternatives"
+		android:orderInCategory="50"
+		android:title="@string/alternatives"
+		app:showAsAction="never" />
+
 	<item
 		android:id="@+id/action_online"
 		android:orderInCategory="50"

app/src/main/res/values-night/colors.xml

@@ -11,6 +11,8 @@
 	<color name="status_bar_incognito">#66311B92</color>
 	<color name="warning">#FB8C00</color>
 	<color name="launcher_background">#222222</color>
+	<color name="common_green">#81C784</color>
+	<color name="common_red">#E57373</color>
 
 	<!-- Color schemes colors -->
 	<color name="background_miku">#191C1C</color>

app/src/main/res/values/colors.xml

@@ -25,6 +25,8 @@
 	<color name="status_bar_incognito">#99B39DDB</color>
 	<color name="warning">#E65100</color>
 	<color name="launcher_background">#FFFFFF</color>
+	<color name="common_green">#388E3C</color>
+	<color name="common_red">#D32F2F</color>
 
 	<!-- Color schemes colors -->
 	<color name="background_miku">#E4FFFA</color>