fix: expose user_cache and make it a changenotifier

Author: demchenkoalex

packages/flutter_chat_core/lib/src/utils/user_cache.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/foundation.dart';
 import '../models/user.dart';
 import 'typedefs.dart';
 
@@ -6,7 +7,9 @@ import 'typedefs.dart';
 /// Uses a Least Recently Used (LRU) eviction strategy to limit memory usage.
 /// When the cache reaches the maximum size, the least recently accessed user
 /// will be removed to make space for new entries.
-class UserCache {
+///
+/// Extends [ChangeNotifier] to allow widgets to listen for cache modifications.
+class UserCache extends ChangeNotifier {
   final Map<UserID, User?> _cache = {};
   final List<UserID> _accessOrder = []; // For LRU eviction
 
@@ -19,7 +22,9 @@ class UserCache {
   /// ```dart
   /// final cache = UserCache(maxSize: 100);
   /// ```
-  UserCache({this.maxSize = 100});
+  UserCache({this.maxSize = 100}) {
+    assert(maxSize > 0, 'UserCache maxSize must be a positive integer.');
+  }
 
   /// Gets a user synchronously from cache, or returns null if not cached.
   ///
@@ -68,26 +73,37 @@ class UserCache {
   void clear() {
     _cache.clear();
     _accessOrder.clear();
+    notifyListeners();
   }
 
   /// Removes a specific user from the cache.
   void remove(UserID userId) {
-    _cache.remove(userId);
-    _accessOrder.remove(userId);
+    if (_cache.containsKey(userId)) {
+      _cache.remove(userId);
+      _accessOrder.remove(userId);
+      notifyListeners();
+    }
   }
 
   /// Internal method to add or update a user in the cache.
   /// Handles LRU eviction if the cache is full.
   void _cacheUser(UserID userId, User? user) {
+    var needsNotify = true;
     // Handle eviction if needed
     if (_accessOrder.length >= maxSize && !_cache.containsKey(userId)) {
       final oldestId = _accessOrder.removeAt(0);
       _cache.remove(oldestId);
+    } else if (_cache.containsKey(userId) && _cache[userId] == user) {
+      needsNotify = false;
     }
 
     // Update cache
     _cache[userId] = user;
     _accessOrder.remove(userId);
     _accessOrder.add(userId);
+
+    if (needsNotify) {
+      notifyListeners();
+    }
   }
 }

packages/flutter_chat_ui/lib/src/avatar.dart

@@ -43,7 +43,7 @@ class Avatar extends StatelessWidget {
   Widget build(BuildContext context) {
     final theme = context.watch<ChatTheme>();
     final resolveUser = context.read<ResolveUserCallback>();
-    final userCache = context.read<UserCache>();
+    final userCache = context.watch<UserCache>();
 
     // Try to get from cache synchronously first
     final cachedUser = userCache.getSync(userId);

packages/flutter_chat_ui/lib/src/chat.dart

@@ -31,6 +31,12 @@ class Chat extends StatefulWidget {
   /// If not provided, a default instance is created.
   final CrossCache? crossCache;
 
+  /// Optional user-provided cache for resolved `User` objects.
+  /// Ideally, you would not provide this and rely on the default internal LRU cache.
+  /// However, you can supply your own instance if you need direct control to clear
+  /// the cache for a specific user (e.g., when an avatar URL changes and requires a refresh).
+  final UserCache? userCache;
+
   /// The visual theme for the chat UI.
   /// If not provided, defaults to [ChatTheme.light].
   final ChatTheme? theme;
@@ -68,6 +74,7 @@ class Chat extends StatefulWidget {
     required this.chatController,
     this.builders,
     this.crossCache,
+    this.userCache,
     this.theme,
     this.onMessageSend,
     this.onMessageTap,
@@ -86,6 +93,7 @@ class _ChatState extends State<Chat> with WidgetsBindingObserver {
   late ChatTheme _theme;
   late Builders _builders;
   late final CrossCache _crossCache;
+  late final UserCache _userCache;
   late DateFormat _timeFormat;
 
   @override
@@ -95,6 +103,7 @@ class _ChatState extends State<Chat> with WidgetsBindingObserver {
     _updateTheme();
     _updateBuilders();
     _crossCache = widget.crossCache ?? CrossCache();
+    _userCache = widget.userCache ?? UserCache(maxSize: 100);
     _timeFormat = widget.timeFormat ?? DateFormat('HH:mm');
   }
 
@@ -133,14 +142,17 @@ class _ChatState extends State<Chat> with WidgetsBindingObserver {
         Provider.value(value: _theme),
         Provider.value(value: _builders),
         Provider.value(value: _crossCache),
+        if (widget.userCache != null)
+          ChangeNotifierProvider.value(value: _userCache)
+        else
+          ChangeNotifierProvider(create: (_) => _userCache),
         Provider.value(value: _timeFormat),
         Provider.value(value: widget.onMessageSend),
         Provider.value(value: widget.onMessageTap),
         Provider.value(value: widget.onMessageLongPress),
         Provider.value(value: widget.onAttachmentTap),
         ChangeNotifierProvider(create: (_) => ComposerHeightNotifier()),
         ChangeNotifierProvider(create: (_) => LoadMoreNotifier()),
-        Provider(create: (_) => UserCache(maxSize: 100)),
       ],
       child: Container(
         color: