refactor(paging): share unknown-total sentinel

lib/media/library_query.dart

@@ -76,3 +76,11 @@ sealed class LibraryPage<T> with _$LibraryPage<T> {
   const factory LibraryPage({required List<T> items, required int totalCount, @Default(0) int offset}) =
       _LibraryPage<T>;
 }
+
+/// Conservative total for a page whose backend omitted an exact count. A full
+/// page adds one sentinel item so callers keep pagination enabled without
+/// claiming to know the real total.
+int fallbackPageTotal({required int offset, required int itemCount, int? requestedSize}) {
+  final fullPage = requestedSize != null && requestedSize > 0 && itemCount >= requestedSize;
+  return offset + itemCount + (fullPage ? 1 : 0);
+}

lib/services/jellyfin_client/parts/browse.dart

@@ -107,13 +107,6 @@ String _jellyfinFolderSortName(Map<String, dynamic> item) {
   return raw.toLowerCase();
 }
 
-int _fallbackPageTotal({required int offset, required int itemCount, int? requestedSize}) {
-  if (requestedSize == null || requestedSize <= 0 || itemCount < requestedSize) {
-    return offset + itemCount;
-  }
-  return offset + itemCount + 1;
-}
-
 /// `/Items/Filters` is a legacy unpaged endpoint; keep failures isolated from
 /// the paged Browse tab so very large libraries can still open.
 const _filtersTimeout = Duration(seconds: 8);
@@ -209,7 +202,7 @@ mixin _JellyfinBrowseMethods on MediaServerCacheMixin {
     final totalUnreliable = isArtistQuery && rawTotal == 0 && items.isNotEmpty;
     final total = rawTotal is int && !totalUnreliable
         ? rawTotal
-        : _fallbackPageTotal(offset: query.offset, itemCount: items.length, requestedSize: query.limit);
+        : fallbackPageTotal(offset: query.offset, itemCount: items.length, requestedSize: query.limit);
     return LibraryPage<MediaItem>(items: _mapItems(items), totalCount: total, offset: query.offset);
   }
 
@@ -1588,7 +1581,7 @@ mixin _JellyfinBrowseMethods on MediaServerCacheMixin {
       final rawTotal = data is Map<String, dynamic> ? data['TotalRecordCount'] : null;
       final fallbackTotal = singlePage
           ? offset + rawItems.length
-          : _fallbackPageTotal(offset: offset, itemCount: rawItems.length, requestedSize: requestedSize);
+          : fallbackPageTotal(offset: offset, itemCount: rawItems.length, requestedSize: requestedSize);
       return LibraryPage<MediaItem>(
         items: _mapItems(rawItems),
         totalCount: rawTotal is int ? rawTotal : fallbackTotal,
@@ -1603,7 +1596,7 @@ mixin _JellyfinBrowseMethods on MediaServerCacheMixin {
   LibraryPage<MediaItem> _pagedMediaItems(Object? data, {required int offset, required int requestedSize}) {
     final rawItems = _itemsArray(data);
     final rawTotal = data is Map<String, dynamic> ? data['TotalRecordCount'] : null;
-    final fallbackTotal = _fallbackPageTotal(offset: offset, itemCount: rawItems.length, requestedSize: requestedSize);
+    final fallbackTotal = fallbackPageTotal(offset: offset, itemCount: rawItems.length, requestedSize: requestedSize);
     return LibraryPage<MediaItem>(
       items: _mapItems(rawItems),
       totalCount: rawTotal is int ? rawTotal : fallbackTotal,

lib/services/jellyfin_client/parts/collections.dart

@@ -76,7 +76,7 @@ mixin _JellyfinCollectionMethods on MediaServerCacheMixin {
   LibraryPage<MediaItem> _itemsPage(Object? data, {required int offset, int? requestedSize}) {
     final rawItems = _itemsArray(data);
     final rawTotal = data is Map<String, dynamic> ? data['TotalRecordCount'] : null;
-    final fallbackTotal = _fallbackPageTotal(offset: offset, itemCount: rawItems.length, requestedSize: requestedSize);
+    final fallbackTotal = fallbackPageTotal(offset: offset, itemCount: rawItems.length, requestedSize: requestedSize);
     final total = rawTotal is int ? rawTotal : fallbackTotal;
     return LibraryPage<MediaItem>(items: _mapItems(rawItems), totalCount: total, offset: offset);
   }

lib/services/jellyfin_client/parts/playlists.dart

@@ -83,7 +83,7 @@ mixin _JellyfinPlaylistMethods on MediaServerCacheMixin {
 
     final fallbackTotal = rawFinished
         ? filteredSeen
-        : _fallbackPageTotal(offset: offset, itemCount: items.length, requestedSize: pageSize);
+        : fallbackPageTotal(offset: offset, itemCount: items.length, requestedSize: pageSize);
     return LibraryPage<MediaPlaylist>(items: items, totalCount: fallbackTotal, offset: offset);
   }
 
@@ -134,7 +134,7 @@ mixin _JellyfinPlaylistMethods on MediaServerCacheMixin {
     final rawTotal = response.data is Map<String, dynamic>
         ? (response.data as Map<String, dynamic>)['TotalRecordCount']
         : null;
-    final fallbackTotal = _fallbackPageTotal(offset: offset, itemCount: items.length, requestedSize: pageSize);
+    final fallbackTotal = fallbackPageTotal(offset: offset, itemCount: items.length, requestedSize: pageSize);
     return LibraryPage<MediaItem>(
       items: _mapItems(items),
       totalCount: rawTotal is int ? rawTotal : fallbackTotal,

lib/services/plex_client.dart

@@ -758,11 +758,6 @@ class PlexClient
     return null;
   }
 
-  int _fallbackPageTotal({required int offset, required int itemCount, int? requestedSize}) {
-    final fullPage = requestedSize != null && requestedSize > 0 && itemCount >= requestedSize;
-    return offset + itemCount + (fullPage ? 1 : 0);
-  }
-
   int _responseTotalSize(MediaServerResponse response, {required int itemCount, int? start, int? requestedSize}) {
     final headerTotal = _responseHeaderInt(response, 'X-Plex-Container-Total-Size');
     if (headerTotal != null) return headerTotal;
@@ -776,7 +771,7 @@ class PlexClient
       return flexibleInt(container?['size']) ?? itemCount;
     }
 
-    return _fallbackPageTotal(offset: offset, itemCount: itemCount, requestedSize: requestedSize);
+    return fallbackPageTotal(offset: offset, itemCount: itemCount, requestedSize: requestedSize);
   }
 
   ({List<PlexPlaylistDto> items, int totalSize}) _extractPlaylistListResult(

test/media/library_query_test.dart

@@ -0,0 +1,13 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/media/library_query.dart';
+
+void main() {
+  test('fallbackPageTotal adds a has-more sentinel only for full pages', () {
+    expect(fallbackPageTotal(offset: 20, itemCount: 10, requestedSize: 10), 31);
+    expect(fallbackPageTotal(offset: 20, itemCount: 11, requestedSize: 10), 32);
+    expect(fallbackPageTotal(offset: 20, itemCount: 9, requestedSize: 10), 29);
+    expect(fallbackPageTotal(offset: 20, itemCount: 10), 30);
+    expect(fallbackPageTotal(offset: 20, itemCount: 10, requestedSize: 0), 30);
+    expect(fallbackPageTotal(offset: 20, itemCount: 10, requestedSize: -1), 30);
+  });
+}