fix(discover): preserve library order on home

close #1034

lib/screens/discover_screen.dart

@@ -49,6 +49,7 @@ import '../utils/watch_state_notifier.dart';
 import '../utils/app_logger.dart';
 import '../utils/dialogs.dart';
 import '../utils/formatters.dart';
+import '../utils/media_hub_ordering.dart';
 import '../utils/provider_extensions.dart';
 import '../utils/video_player_navigation.dart';
 import '../utils/layout_constants.dart';
@@ -128,7 +129,9 @@ class _DiscoverScreenState extends State<DiscoverScreen>
   bool _isAutoScrollPaused = false;
   bool _isTabVisible = true;
   HiddenLibrariesProvider? _hiddenLibrariesProvider;
+  LibrariesProvider? _librariesProvider;
   Set<String> _lastSeenHiddenKeys = {};
+  List<String> _lastSeenLibraryOrderKeys = const [];
 
   // WatchStateAware: watch on-deck items and their parent shows/seasons
   @override
@@ -308,6 +311,13 @@ class _DiscoverScreenState extends State<DiscoverScreen>
       _hiddenLibrariesProvider = provider;
       _hiddenLibrariesProvider!.addListener(_onHiddenLibrariesChanged);
     }
+    final librariesProvider = context.read<LibrariesProvider>();
+    if (librariesProvider != _librariesProvider) {
+      _librariesProvider?.removeListener(_onLibrariesChanged);
+      _librariesProvider = librariesProvider;
+      _lastSeenLibraryOrderKeys = _libraryOrderKeys(librariesProvider);
+      _librariesProvider!.addListener(_onLibrariesChanged);
+    }
   }
 
   void _onHiddenLibrariesChanged() {
@@ -319,6 +329,34 @@ class _DiscoverScreenState extends State<DiscoverScreen>
     _loadContent();
   }
 
+  void _onLibrariesChanged() {
+    final provider = _librariesProvider;
+    if (provider == null) return;
+    final currentKeys = _libraryOrderKeys(provider);
+    if (_sameStringList(currentKeys, _lastSeenLibraryOrderKeys)) return;
+    _lastSeenLibraryOrderKeys = currentKeys;
+    if (_hubs.isEmpty || !mounted) return;
+
+    final sortedHubs = List<MediaHub>.from(_hubs);
+    if (!sortMediaHubsByLibraryOrder(sortedHubs, provider.libraries)) return;
+    setState(() {
+      _hubs = sortedHubs;
+      _updateHubKeys();
+    });
+  }
+
+  List<String> _libraryOrderKeys(LibrariesProvider provider) {
+    return [for (final library in provider.libraries) library.globalKey];
+  }
+
+  bool _sameStringList(List<String> a, List<String> b) {
+    if (a.length != b.length) return false;
+    for (var i = 0; i < a.length; i++) {
+      if (a[i] != b[i]) return false;
+    }
+    return true;
+  }
+
   /// Handle key events for the hero section
   late final _handleHeroKeyEvent = dpadKeyHandler(
     onDown: () {
@@ -348,6 +386,7 @@ class _DiscoverScreenState extends State<DiscoverScreen>
   @override
   void dispose() {
     _hiddenLibrariesProvider?.removeListener(_onHiddenLibrariesChanged);
+    _librariesProvider?.removeListener(_onLibrariesChanged);
     WidgetsBinding.instance.removeObserver(this);
     _autoScrollTimer?.cancel();
     _indicatorTimer?.cancel();
@@ -601,24 +640,8 @@ class _DiscoverScreenState extends State<DiscoverScreen>
             !title.contains('next up');
       }).toList();
 
-      // Sort hubs by the user's library order
       final libraryOrder = context.read<LibrariesProvider>().libraries;
-      if (!useGlobalHubs && libraryOrder.isNotEmpty) {
-        final orderMap = <String, int>{};
-        for (var i = 0; i < libraryOrder.length; i++) {
-          orderMap[libraryOrder[i].globalKey] = i;
-        }
-        filteredHubs.sort((a, b) {
-          final aKey = _hubLibraryGlobalKey(a);
-          final bKey = _hubLibraryGlobalKey(b);
-          final aIndex = aKey != null ? orderMap[aKey] : null;
-          final bIndex = bKey != null ? orderMap[bKey] : null;
-          if (aIndex == null && bIndex == null) return 0;
-          if (aIndex == null) return 1;
-          if (bIndex == null) return -1;
-          return aIndex.compareTo(bIndex);
-        });
-      }
+      sortMediaHubsByLibraryOrder(filteredHubs, libraryOrder);
 
       appLogger.d('Received ${onDeck.length} on deck items and ${filteredHubs.length} global hubs from all servers');
       if (!mounted) return;
@@ -640,15 +663,6 @@ class _DiscoverScreenState extends State<DiscoverScreen>
     }
   }
 
-  /// Resolve the library globalKey for a hub (for sorting by library order).
-  String? _hubLibraryGlobalKey(MediaHub hub) {
-    final serverId = hub.serverId;
-    if (serverId == null) return null;
-    final sectionId = hub.libraryId ?? hub.items.firstOrNull?.libraryId;
-    if (sectionId == null) return null;
-    return buildGlobalKey(serverId, sectionId);
-  }
-
   /// Refresh only the Continue Watching section in the background
   /// This is called when returning to the home screen to avoid blocking UI
   Future<void> _refreshContinueWatching() async {

lib/utils/media_hub_ordering.dart

@@ -0,0 +1,56 @@
+import '../media/media_hub.dart';
+import '../media/media_library.dart';
+import 'global_key_utils.dart';
+
+/// Sorts home hubs by the user's library order. Hubs without a known library
+/// stay after known-library hubs, preserving their relative server order.
+bool sortMediaHubsByLibraryOrder(List<MediaHub> hubs, List<MediaLibrary> libraryOrder) {
+  if (hubs.length < 2 || libraryOrder.isEmpty) return false;
+
+  final orderByGlobalKey = <String, int>{};
+  for (var i = 0; i < libraryOrder.length; i++) {
+    orderByGlobalKey.putIfAbsent(libraryOrder[i].globalKey, () => i);
+  }
+
+  final indexedHubs = [for (var i = 0; i < hubs.length; i++) (index: i, hub: hubs[i])];
+  indexedHubs.sort((a, b) {
+    final aIndex = _hubLibraryOrderIndex(a.hub, orderByGlobalKey);
+    final bIndex = _hubLibraryOrderIndex(b.hub, orderByGlobalKey);
+    if (aIndex == null && bIndex == null) return a.index.compareTo(b.index);
+    if (aIndex == null) return 1;
+    if (bIndex == null) return -1;
+
+    final order = aIndex.compareTo(bIndex);
+    if (order != 0) return order;
+    return a.index.compareTo(b.index);
+  });
+
+  var changed = false;
+  for (var i = 0; i < hubs.length; i++) {
+    final hub = indexedHubs[i].hub;
+    if (!identical(hubs[i], hub)) changed = true;
+    hubs[i] = hub;
+  }
+  return changed;
+}
+
+int? _hubLibraryOrderIndex(MediaHub hub, Map<String, int> orderByGlobalKey) {
+  final hubLibraryKey = _globalKey(hub.serverId, hub.libraryId);
+  final hubIndex = hubLibraryKey == null ? null : orderByGlobalKey[hubLibraryKey];
+  if (hubIndex != null) return hubIndex;
+
+  int? bestIndex;
+  for (final item in hub.items) {
+    final key = _globalKey(item.serverId ?? hub.serverId, item.libraryId);
+    final index = key == null ? null : orderByGlobalKey[key];
+    if (index != null && (bestIndex == null || index < bestIndex)) {
+      bestIndex = index;
+    }
+  }
+  return bestIndex;
+}
+
+String? _globalKey(String? serverId, String? libraryId) {
+  if (serverId == null || libraryId == null) return null;
+  return buildGlobalKey(serverId, libraryId);
+}

test/utils/media_hub_ordering_test.dart

@@ -0,0 +1,92 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/media/media_backend.dart';
+import 'package:plezy/media/media_hub.dart';
+import 'package:plezy/media/media_item.dart';
+import 'package:plezy/media/media_kind.dart';
+import 'package:plezy/media/media_library.dart';
+import 'package:plezy/utils/media_hub_ordering.dart';
+
+MediaLibrary _library(String id, {String serverId = 'server'}) {
+  return MediaLibrary(
+    id: id,
+    backend: MediaBackend.plex,
+    title: 'Library $id',
+    kind: MediaKind.movie,
+    serverId: serverId,
+  );
+}
+
+MediaItem _item(String id, {String? libraryId, String? serverId = 'server'}) {
+  return MediaItem(id: id, backend: MediaBackend.plex, kind: MediaKind.movie, libraryId: libraryId, serverId: serverId);
+}
+
+MediaHub _hub(String id, {String? libraryId, String? serverId = 'server', List<MediaItem> items = const []}) {
+  return MediaHub(id: id, title: id, type: 'movie', libraryId: libraryId, serverId: serverId, items: items);
+}
+
+void main() {
+  group('sortMediaHubsByLibraryOrder', () {
+    test('sorts explicit library hubs by library order', () {
+      final hubs = [_hub('movies', libraryId: '1'), _hub('anime', libraryId: '3'), _hub('shows', libraryId: '2')];
+
+      final changed = sortMediaHubsByLibraryOrder(hubs, [_library('3'), _library('1'), _library('2')]);
+
+      expect(changed, isTrue);
+      expect(hubs.map((hub) => hub.id), ['anime', 'movies', 'shows']);
+    });
+
+    test('uses item library ids for promoted hubs', () {
+      final hubs = [
+        _hub('recent-movies', items: [_item('movie', libraryId: '1')]),
+        _hub('recent-tv', items: [_item('episode', libraryId: '2')]),
+      ];
+
+      final changed = sortMediaHubsByLibraryOrder(hubs, [_library('2'), _library('1')]);
+
+      expect(changed, isTrue);
+      expect(hubs.map((hub) => hub.id), ['recent-tv', 'recent-movies']);
+    });
+
+    test('uses the earliest ordered item library within mixed hubs', () {
+      final hubs = [
+        _hub('later', items: [_item('later', libraryId: '3')]),
+        _hub(
+          'mixed',
+          items: [
+            _item('last', libraryId: '4'),
+            _item('first', libraryId: '1'),
+          ],
+        ),
+      ];
+
+      final changed = sortMediaHubsByLibraryOrder(hubs, [_library('1'), _library('3'), _library('4')]);
+
+      expect(changed, isTrue);
+      expect(hubs.map((hub) => hub.id), ['mixed', 'later']);
+    });
+
+    test('keeps equal and unknown hubs stable after known libraries', () {
+      final hubs = [
+        _hub('unknown-a'),
+        _hub('second-a', libraryId: '2'),
+        _hub('unknown-b', serverId: null, items: [_item('missing-server', libraryId: '1', serverId: null)]),
+        _hub('first', libraryId: '1'),
+        _hub('second-b', libraryId: '2'),
+      ];
+
+      final changed = sortMediaHubsByLibraryOrder(hubs, [_library('1'), _library('2')]);
+
+      expect(changed, isTrue);
+      expect(hubs.map((hub) => hub.id), ['first', 'second-a', 'second-b', 'unknown-a', 'unknown-b']);
+    });
+
+    test('returns false when the current order is already correct', () {
+      final hubs = [_hub('first', libraryId: '1'), _hub('second', libraryId: '2')];
+
+      final changed = sortMediaHubsByLibraryOrder(hubs, [_library('1'), _library('2')]);
+
+      expect(changed, isFalse);
+      expect(hubs.map((hub) => hub.id), ['first', 'second']);
+    });
+  });
+}