Add misc preferences

lib/utils/pref_notifier.dart

@@ -0,0 +1,41 @@
+import 'package:hiddify/data/data_providers.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+class PrefNotifier<T> extends AutoDisposeNotifier<T> {
+  PrefNotifier(this._key, this._defaultValue);
+
+  final String _key;
+  final T _defaultValue;
+
+  static AutoDisposeNotifierProvider<PrefNotifier<T>, T> provider<T>(
+    String key,
+    T defaultValue,
+  ) =>
+      NotifierProvider.autoDispose(
+        () => PrefNotifier(key, defaultValue),
+      );
+
+  SharedPreferences get _prefs => ref.read(sharedPreferencesProvider);
+
+  /// Updates the value asynchronously.
+  Future<void> update(T value) async {
+    if (value is String) {
+      await _prefs.setString(_key, value);
+    } else if (value is bool) {
+      await _prefs.setBool(_key, value);
+    } else if (value is int) {
+      await _prefs.setInt(_key, value);
+    } else if (value is double) {
+      await _prefs.setDouble(_key, value);
+    } else if (value is List<String>) {
+      await _prefs.setStringList(_key, value);
+    }
+    super.state = value;
+  }
+
+  @override
+  T build() {
+    return _prefs.get(_key) as T? ?? _defaultValue;
+  }
+}