feat(core,app,android,ios): filter the library on every client, including by download

The library filter moves from the desktop into pstr_core::browse and
gains a Downloaded filter: titles with at least one episode kept on the
device. The bridge's arrangement() takes the filter. Android and iOS get
a row of filter chips above the grid. The choice is remembered per
device, and shelves stay hidden under a filter, as on the desktop.

android/app/src/main/java/io/narl/protonstream/settings/SettingsStore.kt

@@ -46,6 +46,11 @@ class SettingsStore(context: Context) {
         get() = preferences.getBoolean(KEY_METADATA_OFFER_DISMISSED, false)
         set(value) { preferences.edit { putBoolean(KEY_METADATA_OFFER_DISMISSED, value) } }
 
+    /** Which titles the library last showed, as a `LibraryFilter` name; null for all. */
+    var libraryFilter: String?
+        get() = preferences.getString(KEY_LIBRARY_FILTER, null)
+        set(value) { preferences.edit { putString(KEY_LIBRARY_FILTER, value) } }
+
     /** Whether the library folds each franchise into one tile. */
     var libraryGrouped: Boolean
         get() = preferences.getBoolean(KEY_LIBRARY_GROUPED, true)
@@ -67,6 +72,7 @@ class SettingsStore(context: Context) {
         private const val KEY_CACHE_BUDGET_GIB = "cache_budget_gib"
         private const val KEY_LIBRARY_SORT = "library_sort"
         private const val KEY_LIBRARY_GROUPED = "library_grouped"
+        private const val KEY_LIBRARY_FILTER = "library_filter"
         private const val KEY_METADATA_OFFER_DISMISSED = "metadata_offer_dismissed"
     }
 }

android/app/src/main/java/io/narl/protonstream/ui/AppViewModel.kt

@@ -28,6 +28,7 @@ import io.narl.protonstream.native.NativeRuntime
 import io.narl.protonstream.settings.SettingsStore
 import io.narl.protonstream.ui.theme.AppearanceState
 import uniffi.pstr_android.ArrangementRecord
+import uniffi.pstr_android.LibraryFilter
 import uniffi.pstr_android.LibrarySort
 import uniffi.pstr_android.ShareRecord
 import uniffi.pstr_android.TitleRecord
@@ -57,6 +58,7 @@ data class AppUiState(
      * when the grid falls back to [titles] as they are.
      */
     val arrangement: ArrangementRecord? = null,
+    val filter: LibraryFilter = LibraryFilter.ALL,
     val sort: LibrarySort = LibrarySort.NAME,
     val grouped: Boolean = true,
     val shares: List<ShareRecord> = emptyList(),
@@ -135,12 +137,16 @@ class AppViewModel(context: Context, private val workManager: WorkManager) : Vie
         // The arrangement first, so the first grid is drawn the way the viewer
         // left it rather than A–Z and then re-sorted under them.
         viewModelScope.launch {
-            val (sort, grouped) = withContext(Dispatchers.IO) {
+            val (filter, sort, grouped) = withContext(Dispatchers.IO) {
                 SettingsStore(appContext).run {
-                    librarySort?.let { name -> LibrarySort.entries.firstOrNull { it.name == name } } to libraryGrouped
+                    Triple(
+                        libraryFilter?.let { name -> LibraryFilter.entries.firstOrNull { it.name == name } },
+                        librarySort?.let { name -> LibrarySort.entries.firstOrNull { it.name == name } },
+                        libraryGrouped,
+                    )
                 }
             }
-            mutableState.update { it.copy(sort = sort ?: it.sort, grouped = grouped) }
+            mutableState.update { it.copy(filter = filter ?: it.filter, sort = sort ?: it.sort, grouped = grouped) }
             reload()
         }
         catchUp()
@@ -171,7 +177,6 @@ class AppViewModel(context: Context, private val workManager: WorkManager) : Vie
         }
     }
 
-    /** Reorder the grid, or fold or unfold its franchises. */
     /** Sort and fold the library, and keep both for the next launch. */
     fun arrange(sort: LibrarySort, grouped: Boolean) {
         mutableState.update { it.copy(sort = sort, grouped = grouped) }
@@ -186,6 +191,15 @@ class AppViewModel(context: Context, private val workManager: WorkManager) : Vie
         }
     }
 
+    /** Narrow the grid to some titles, and keep the choice for the next launch. */
+    fun filter(filter: LibraryFilter) {
+        mutableState.update { it.copy(filter = filter) }
+        viewModelScope.launch {
+            withContext(Dispatchers.IO) { SettingsStore(appContext).libraryFilter = filter.name }
+            reloadLibrary(mutableState.value.query)
+        }
+    }
+
     fun search(query: String) {
         mutableState.update { it.copy(query = query) }
         searchQuery.value = query
@@ -858,7 +872,7 @@ class AppViewModel(context: Context, private val workManager: WorkManager) : Vie
                 Reloaded(
                     engine.shares(),
                     engine.library(query),
-                    engine.arrangement(query, current.sort, current.grouped),
+                    engine.arrangement(query, current.filter, current.sort, current.grouped),
                     engine.offlineFiles(),
                     engine.metadataSettings(),
                     engine.storageUsage(),
@@ -886,7 +900,7 @@ class AppViewModel(context: Context, private val workManager: WorkManager) : Vie
             withContext(Dispatchers.IO) {
                 val engine = NativeRuntime.engine()
                 val search = query.takeIf(String::isNotBlank)
-                engine.library(search) to engine.arrangement(search, current.sort, current.grouped)
+                engine.library(search) to engine.arrangement(search, current.filter, current.sort, current.grouped)
             }
         }.onSuccess { (titles, arrangement) ->
             mutableState.update { it.copy(titles = titles, arrangement = arrangement) }

android/app/src/main/java/io/narl/protonstream/ui/LibraryScreen.kt

@@ -63,6 +63,7 @@ import androidx.compose.material.icons.filled.Search
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
+import androidx.compose.material3.FilterChip
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextField
@@ -84,6 +85,7 @@ import androidx.compose.material3.DropdownMenu
 import androidx.compose.material3.DropdownMenuItem
 import androidx.compose.material3.HorizontalDivider
 import uniffi.pstr_android.EpisodeRecord
+import uniffi.pstr_android.LibraryFilter
 import uniffi.pstr_android.LibrarySort
 import uniffi.pstr_android.SeasonRecord
 import uniffi.pstr_android.TitleRecord
@@ -109,6 +111,16 @@ private data class Resumable(
 /** One tile of the grid: the title drawn, and how many more of its franchise it stands for. */
 private data class Tile(val title: TitleRecord, val folded: Int)
 
+/** The desktop's names for the filters, from `browse::Filter::label`. */
+internal fun LibraryFilter.label(): String = when (this) {
+    LibraryFilter.ALL -> "All"
+    LibraryFilter.SERIES -> "Series"
+    LibraryFilter.FILMS -> "Films"
+    LibraryFilter.WATCHING -> "Watching"
+    LibraryFilter.UNWATCHED -> "Not started"
+    LibraryFilter.DOWNLOADED -> "Downloaded"
+}
+
 /** The offer of posters and synopses, and its two answers. */
 internal class MetadataOffer(val onOpenSettings: () -> Unit, val onDismiss: () -> Unit)
 
@@ -151,6 +163,7 @@ internal fun LibraryScreen(
     onArrange: (LibrarySort, Boolean) -> Unit = { _, _ -> },
     onAddShare: () -> Unit = {},
     onOpenSettings: () -> Unit = {},
+    onFilter: (LibraryFilter) -> Unit = {},
 ) {
     val download = rememberDownload()
     val context = LocalContext.current
@@ -236,6 +249,7 @@ internal fun LibraryScreen(
                     onTitle,
                     onTitleMenu = { menuFor = it },
                     onResumeMenu = { menuResume = it },
+                    onFilter = onFilter,
                     metadataOffer = if (state.metadataSettings.enabled || offerDismissed) {
                         null
                     } else {
@@ -438,6 +452,7 @@ private fun LibraryGrid(
     onTitle: (TitleRecord) -> Unit,
     onTitleMenu: (TitleRecord) -> Unit,
     onResumeMenu: (Resumable) -> Unit,
+    onFilter: (LibraryFilter) -> Unit = {},
     metadataOffer: MetadataOffer? = null,
 ) {
     // The arrangement names titles by key; before it has arrived, the titles
@@ -499,7 +514,10 @@ private fun LibraryGrid(
             }
         }
         if (state.query.isBlank()) {
-            shelves.forEach { shelf ->
+            // Only over the whole library: under a filter, a shelf of titles
+            // the grid below is hiding reads as the filter not working. The
+            // bridge leaves them out too; this covers the frame before it.
+            shelves.takeIf { state.filter == LibraryFilter.ALL }.orEmpty().forEach { shelf ->
                 item(key = "shelf-${shelf.label}", span = { GridItemSpan(maxLineSpan) }) {
                     Column {
                         Text(shelf.label, style = MaterialTheme.typography.titleMedium)
@@ -520,9 +538,29 @@ private fun LibraryGrid(
                     }
                 }
             }
-            if (resumable.isNotEmpty() || shelves.isNotEmpty()) {
-                item(key = "library-heading", span = { GridItemSpan(maxLineSpan) }) {
-                    Text("All titles", style = MaterialTheme.typography.titleMedium, modifier = Modifier.padding(top = 8.dp))
+            item(key = "library-heading", span = { GridItemSpan(maxLineSpan) }) {
+                Column {
+                    if (resumable.isNotEmpty() || shelves.isNotEmpty()) {
+                        Text("All titles", style = MaterialTheme.typography.titleMedium, modifier = Modifier.padding(top = 8.dp))
+                    }
+                    LazyRow(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                        items(LibraryFilter.entries, key = { it.name }) { filter ->
+                            FilterChip(
+                                selected = filter == state.filter,
+                                onClick = { onFilter(filter) },
+                                label = { Text(filter.label()) },
+                            )
+                        }
+                    }
+                }
+            }
+            if (tiles.isEmpty() && state.filter != LibraryFilter.ALL) {
+                item(key = "filtered-out", span = { GridItemSpan(maxLineSpan) }) {
+                    Text(
+                        "Nothing in the library fits that filter.",
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
                 }
             }
         }

android/app/src/main/java/io/narl/protonstream/ui/ProtonStreamApp.kt

@@ -233,6 +233,7 @@ fun ProtonStreamApp(
                                     addingShare = true
                                 },
                                 onOpenSettings = { destination = Destination.Settings },
+                                onFilter = model::filter,
                                 )
                         }
                         val titlePane = @Composable { selected: TitleRecord ->