opt: оптимизейшон

lib/backend/modules/shared_content.dart

@@ -139,9 +139,7 @@ class SharedContentModule {
     final index = _photoIndexes.putIfAbsent(chatId, _ChatPhotoIndex.new);
 
     for (var page = 0; page < _photoIndexMaxPages; page++) {
-      if (index.items.any((i) => i.dedupKey == photoKey)) {
-        return _snapshot(index);
-      }
+      if (index.seen.contains(photoKey)) return _snapshot(index);
       if (index.reachedEnd) return null;
       await _nextPhotoPage(chatId, index, resolveAnchor);
     }
@@ -212,17 +210,22 @@ class SharedContentModule {
       backward: _photoIndexPageSize,
     );
     index.started = true;
-
-    var added = 0;
-    for (final item in page.items) {
-      if (!index.seen.add(item.dedupKey)) continue;
-      index.items.add(item);
-      added++;
-    }
-    index.items.sort((a, b) => b.time.compareTo(a.time));
     if (page.total > index.total) index.total = page.total;
 
-    if (added == 0) index.reachedEnd = true;
+    final fresh = <SharedMediaItem>[];
+    for (final item in page.items) {
+      if (index.seen.add(item.dedupKey)) fresh.add(item);
+    }
+    if (fresh.isEmpty) {
+      index.reachedEnd = true;
+      return;
+    }
+
+    final oldest = index.items.isEmpty ? null : index.items.last;
+    index.items.addAll(fresh);
+    if (oldest != null && fresh.first.time > oldest.time) {
+      index.items.sort((a, b) => b.time.compareTo(a.time));
+    }
   }
 
   Future<SharedMediaPage> fetchMedia({

lib/frontend/screens/chats/chat_screen.dart

@@ -957,15 +957,13 @@ class _ChatScreenState extends State<ChatScreen>
     );
   }
 
-  PhotoViewerActions _photoActions() {
-    return PhotoViewerActions(
-      goToMessage: _requestGoToMessage,
-      forward: _forwardMessageById,
-      delete: (messageId, senderId) =>
-          _confirmDeleteMessage(messageId, senderId == _myId),
-      viewAllPhotos: () => _openChatInfo(initialTab: ChatInfoTab.media),
-    );
-  }
+  late final PhotoViewerActions _photoActions = PhotoViewerActions(
+    goToMessage: _requestGoToMessage,
+    forward: _forwardMessageById,
+    delete: (messageId, senderId) =>
+        _confirmDeleteMessage(messageId, senderId == _myId),
+    viewAllPhotos: () => _openChatInfo(initialTab: ChatInfoTab.media),
+  );
 
   void _forwardMessageById(String messageId) {
     final message = _messages.where((m) => m.id == messageId).firstOrNull;
@@ -4702,7 +4700,7 @@ class _ChatScreenState extends State<ChatScreen>
                                 nextMessage: nextMessage,
                                 chatType: chat?.type ?? 'CHAT',
                                 chatId: widget.chatId,
-                                photoActions: _photoActions(),
+                                photoActions: _photoActions,
                                 overrideStatus: _effectiveStatus(message),
                                 otherReadTime: _otherReadTime,
                                 reactionsListenable: _reactionNotifierFor(

lib/frontend/widgets/photo_viewer.dart

@@ -208,8 +208,19 @@ class _PhotoViewerScreenState extends State<PhotoViewerScreen> {
         resolveAnchor: () => _resolveAnchor(chatId),
       );
       if (!mounted) return;
+
+      final known = _items.length;
+      final appended =
+          known > 0 &&
+          feed.items.length > known &&
+          feed.items[known - 1].dedupKey == _items.last.id;
+
       setState(() {
-        _items = feed.items.map(_ViewerPhoto.fromFeed).toList();
+        if (appended) {
+          _items.addAll(feed.items.skip(known).map(_ViewerPhoto.fromFeed));
+        } else {
+          _items = feed.items.map(_ViewerPhoto.fromFeed).toList();
+        }
         _total = feed.total;
         _reachedEnd = feed.reachedEnd;
       });