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.

ios/ProtonStream/App/AppModel.swift

@@ -47,6 +47,7 @@ final class AppModel {
     /// when the grid falls back to `titles` as they are.
     var arrangement: ArrangementRecord?
     /// As the viewer last left them.
+    var filter: LibraryFilter = SettingsStore().libraryFilter
     var sort: LibrarySort = SettingsStore().librarySort
     var grouped = SettingsStore().libraryGrouped
     var shares: [ShareRecord] = []
@@ -118,6 +119,13 @@ final class AppModel {
         Task { await reloadLibrary(query) }
     }
 
+    /// Narrow the grid to some titles, and keep the choice for the next launch.
+    func setFilter(_ filter: LibraryFilter) {
+        self.filter = filter
+        SettingsStore().libraryFilter = filter
+        Task { await reloadLibrary(query) }
+    }
+
     func search(_ query: String) {
         self.query = query
         searchTask?.cancel()
@@ -787,6 +795,7 @@ final class AppModel {
     /// `reload`, for a caller that goes on to read what it loaded.
     func reloadNow() async {
         let query = query.trimmingCharacters(in: .whitespaces).isEmpty ? nil : self.query
+        let filter = filter
         let sort = sort
         let grouped = grouped
         do {
@@ -798,7 +807,7 @@ final class AppModel {
                 return Reloaded(
                     shares: try engine.shares(),
                     titles: try engine.library(search: query),
-                    arrangement: try engine.arrangement(search: query, sort: sort, grouped: grouped),
+                    arrangement: try engine.arrangement(search: query, filter: filter, sort: sort, grouped: grouped),
                     offline: try engine.offlineFiles(),
                     metadataSettings: try engine.metadataSettings(),
                     storage: try engine.storageUsage()
@@ -819,11 +828,12 @@ final class AppModel {
 
     private func reloadLibrary(_ query: String) async {
         let search = query.trimmingCharacters(in: .whitespaces).isEmpty ? nil : query
+        let filter = filter
         let sort = sort
         let grouped = grouped
         do {
             let (titles, arrangement) = try await run { engine in
-                (try engine.library(search: search), try engine.arrangement(search: search, sort: sort, grouped: grouped))
+                (try engine.library(search: search), try engine.arrangement(search: search, filter: filter, sort: sort, grouped: grouped))
             }
             self.titles = titles
             self.arrangement = arrangement

ios/ProtonStream/App/SettingsStore.swift

@@ -51,6 +51,15 @@ struct SettingsStore {
         nonmutating set { defaults.set(String(describing: newValue), forKey: Key.librarySort) }
     }
 
+    /// Which titles the library last showed.
+    var libraryFilter: LibraryFilter {
+        get {
+            let stored = defaults.string(forKey: Key.libraryFilter)
+            return Self.filters.first { String(describing: $0) == stored } ?? .all
+        }
+        nonmutating set { defaults.set(String(describing: newValue), forKey: Key.libraryFilter) }
+    }
+
     /// The library's offer of posters and synopses was turned down.
     var metadataOfferDismissed: Bool {
         get { bool(Key.metadataOfferDismissed, default: false) }
@@ -63,6 +72,7 @@ struct SettingsStore {
         nonmutating set { defaults.set(newValue, forKey: Key.libraryGrouped) }
     }
 
+    static let filters: [LibraryFilter] = [.all, .series, .films, .watching, .unwatched, .downloaded]
     private static let sorts: [LibrarySort] = [.name, .recent, .added, .release, .rating, .popularity]
 
     private func bool(_ key: String, default value: Bool) -> Bool {
@@ -75,6 +85,7 @@ struct SettingsStore {
         static let hardwareDecoding = "hardware_decoding"
         static let cacheBudgetGib = "cache_budget_gib"
         static let librarySort = "library_sort"
+        static let libraryFilter = "library_filter"
         static let libraryGrouped = "library_grouped"
         static let metadataOfferDismissed = "metadata_offer_dismissed"
     }

ios/ProtonStream/UI/LibraryView.swift

@@ -229,7 +229,10 @@ struct LibraryView: View {
                         }
                     }
                 }
-                if browsing {
+                // Only over the whole library: under a filter, a shelf of
+                // titles the grid below is hiding reads as the filter not
+                // working.
+                if browsing && model.filter == .all {
                     ForEach(shelves) { shelf in
                         VStack(alignment: .leading, spacing: 10) {
                             Text(shelf.label).textStyle(.titleMedium).foregroundStyle(scheme.onSurface)
@@ -248,6 +251,20 @@ struct LibraryView: View {
                         Text("All titles").textStyle(.titleMedium).foregroundStyle(scheme.onSurface).padding(.top, 8)
                     }
                 }
+                if browsing {
+                    ScrollView(.horizontal, showsIndicators: false) {
+                        HStack(spacing: 8) {
+                            ForEach(SettingsStore.filters, id: \.self) { filter in
+                                FilterChip(label: filter.label, selected: filter == model.filter) { model.setFilter(filter) }
+                            }
+                        }
+                    }
+                    if tiles.isEmpty && model.filter != .all {
+                        Text("Nothing in the library fits that filter.")
+                            .textStyle(.bodyMedium)
+                            .foregroundStyle(scheme.onSurfaceVariant)
+                    }
+                }
                 // Posters, three across on a phone.
                 LazyVGrid(columns: [GridItem(.adaptive(minimum: 108), spacing: 12, alignment: .top)], spacing: 16) {
                     ForEach(tiles) { tile in
@@ -421,6 +438,20 @@ private struct LibrarySkeleton: View {
     }
 }
 
+extension LibraryFilter {
+    /// The desktop's names for the filters, from `browse::Filter::label`.
+    var label: String {
+        switch self {
+        case .all: "All"
+        case .series: "Series"
+        case .films: "Films"
+        case .watching: "Watching"
+        case .unwatched: "Not started"
+        case .downloaded: "Downloaded"
+        }
+    }
+}
+
 /// The offer of posters and synopses, and its two answers.
 private struct MetadataOfferCard: View {
     let onOpenSettings: () -> Void