Show stub if favourite categories empty

app/src/main/java/org/koitharu/kotatsu/favourites/data/FavouriteCategoriesDao.kt

@@ -16,7 +16,7 @@ abstract class FavouriteCategoriesDao {
 	abstract fun observeAll(): Flow<List<FavouriteCategoryEntity>>
 
 	@Query("SELECT * FROM favourite_categories WHERE category_id = :id")
-	abstract fun observe(id: Long): Flow<FavouriteCategoryEntity>
+	abstract fun observe(id: Long): Flow<FavouriteCategoryEntity?>
 
 	@Insert(onConflict = OnConflictStrategy.ABORT)
 	abstract suspend fun insert(category: FavouriteCategoryEntity): Long

app/src/main/java/org/koitharu/kotatsu/favourites/domain/FavouritesRepository.kt

@@ -1,10 +1,7 @@
 package org.koitharu.kotatsu.favourites.domain
 
 import androidx.room.withTransaction
-import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.distinctUntilChanged
-import kotlinx.coroutines.flow.flatMapLatest
-import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.*
 import org.koitharu.kotatsu.core.db.MangaDatabase
 import org.koitharu.kotatsu.core.db.entity.*
 import org.koitharu.kotatsu.core.model.FavouriteCategory
@@ -52,9 +49,9 @@ class FavouritesRepository(
 		}.distinctUntilChanged()
 	}
 
-	fun observeCategory(id: Long): Flow<FavouriteCategory> {
+	fun observeCategory(id: Long): Flow<FavouriteCategory?> {
 		return db.favouriteCategoriesDao.observe(id)
-			.map { it.toFavouriteCategory() }
+			.map { it?.toFavouriteCategory() }
 	}
 
 	fun observeCategories(mangaId: Long): Flow<List<FavouriteCategory>> {
@@ -162,6 +159,7 @@ class FavouritesRepository(
 
 	private fun observeOrder(categoryId: Long): Flow<SortOrder> {
 		return db.favouriteCategoriesDao.observe(categoryId)
+			.filterNotNull()
 			.map { x -> SortOrder(x.order, SortOrder.NEWEST) }
 			.distinctUntilChanged()
 	}

app/src/main/java/org/koitharu/kotatsu/favourites/ui/FavouritesContainerFragment.kt

@@ -6,6 +6,7 @@ import androidx.appcompat.view.ActionMode
 import androidx.appcompat.widget.PopupMenu
 import androidx.core.graphics.Insets
 import androidx.core.view.children
+import androidx.core.view.isVisible
 import androidx.core.view.updateLayoutParams
 import androidx.core.view.updatePadding
 import com.google.android.material.snackbar.Snackbar
@@ -17,6 +18,7 @@ import org.koitharu.kotatsu.base.ui.BaseFragment
 import org.koitharu.kotatsu.base.ui.util.ActionModeListener
 import org.koitharu.kotatsu.core.model.FavouriteCategory
 import org.koitharu.kotatsu.databinding.FragmentFavouritesBinding
+import org.koitharu.kotatsu.databinding.ItemEmptyStateBinding
 import org.koitharu.kotatsu.favourites.ui.categories.CategoriesActivity
 import org.koitharu.kotatsu.favourites.ui.categories.CategoriesEditDelegate
 import org.koitharu.kotatsu.favourites.ui.categories.FavouritesCategoriesViewModel
@@ -31,13 +33,15 @@ class FavouritesContainerFragment :
 	BaseFragment<FragmentFavouritesBinding>(),
 	FavouritesTabLongClickListener,
 	CategoriesEditDelegate.CategoriesEditCallback,
-	ActionModeListener {
+	ActionModeListener,
+	View.OnClickListener {
 
 	private val viewModel by viewModel<FavouritesCategoriesViewModel>()
 	private val editDelegate by lazy(LazyThreadSafetyMode.NONE) {
 		CategoriesEditDelegate(requireContext(), this)
 	}
 	private var pagerAdapter: FavouritesPagerAdapter? = null
+	private var stubBinding: ItemEmptyStateBinding? = null
 
 	override fun onCreate(savedInstanceState: Bundle?) {
 		super.onCreate(savedInstanceState)
@@ -52,9 +56,7 @@ class FavouritesContainerFragment :
 	override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
 		super.onViewCreated(view, savedInstanceState)
 		val adapter = FavouritesPagerAdapter(this, this)
-		viewModel.visibleCategories.value?.let {
-			adapter.replaceData(it)
-		}
+		viewModel.visibleCategories.value?.let(::onCategoriesChanged)
 		binding.pager.adapter = adapter
 		pagerAdapter = adapter
 		TabLayoutMediator(binding.tabs, binding.pager, adapter).attach()
@@ -66,6 +68,7 @@ class FavouritesContainerFragment :
 
 	override fun onDestroyView() {
 		pagerAdapter = null
+		stubBinding = null
 		super.onDestroyView()
 	}
 
@@ -101,6 +104,15 @@ class FavouritesContainerFragment :
 
 	private fun onCategoriesChanged(categories: List<CategoryListModel>) {
 		pagerAdapter?.replaceData(categories)
+		if (categories.isEmpty()) {
+			binding.pager.isVisible = false
+			binding.tabs.isVisible = false
+			showStub()
+		} else {
+			binding.pager.isVisible = true
+			binding.tabs.isVisible = true
+			(stubBinding?.root ?: binding.stubEmptyState).isVisible = false
+		}
 	}
 
 	override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
@@ -130,6 +142,12 @@ class FavouritesContainerFragment :
 		return true
 	}
 
+	override fun onClick(v: View) {
+		when (v.id) {
+			R.id.button_retry -> startActivity(FavouritesCategoryEditActivity.newIntent(v.context))
+		}
+	}
+
 	override fun onDeleteCategory(category: FavouriteCategory) {
 		viewModel.deleteCategory(category.id)
 	}
@@ -168,6 +186,18 @@ class FavouritesContainerFragment :
 		menu.show()
 	}
 
+	private fun showStub() {
+		val stub = stubBinding ?: ItemEmptyStateBinding.bind(binding.stubEmptyState.inflate())
+		stub.root.isVisible = true
+		stub.icon.setImageResource(R.drawable.ic_heart_outline)
+		stub.textPrimary.setText(R.string.text_empty_holder_primary)
+		stub.textSecondary.setText(R.string.empty_favourite_categories)
+		stub.buttonRetry.setText(R.string.add)
+		stub.buttonRetry.isVisible = true
+		stub.buttonRetry.setOnClickListener(this)
+		stubBinding = stub
+	}
+
 	companion object {
 
 		fun newInstance() = FavouritesContainerFragment()

app/src/main/java/org/koitharu/kotatsu/favourites/ui/categories/FavouritesCategoriesViewModel.kt

@@ -30,7 +30,7 @@ class FavouritesCategoriesViewModel(
 		repository.observeCategories(),
 		observeAllCategoriesVisible(),
 	) { list, showAll ->
-		mapCategories(list, showAll, showAll)
+		mapCategories(list, showAll, showAll && list.isNotEmpty())
 	}.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default)
 
 	fun deleteCategory(id: Long) {

app/src/main/java/org/koitharu/kotatsu/favourites/ui/list/FavouritesListViewModel.kt

@@ -28,11 +28,11 @@ class FavouritesListViewModel(
 	settings: AppSettings,
 ) : MangaListViewModel(settings), CountersProvider {
 
-	var sortOrder: LiveData<SortOrder> = if (categoryId == NO_ID) {
+	var sortOrder: LiveData<SortOrder?> = if (categoryId == NO_ID) {
 		MutableLiveData(null)
 	} else {
 		repository.observeCategory(categoryId)
-			.map { it.order }
+			.map { it?.order }
 			.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default)
 	}