🎨 Use feature based folder structure

lib/core/notification.dart

@@ -0,0 +1,99 @@
+import 'dart:async';
+
+import 'package:island/accounts/accounts_models/account.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+import 'package:uuid/uuid.dart';
+
+part 'notification.g.dart';
+
+const kNotificationBaseDuration = Duration(seconds: 5);
+const kNotificationStackedDuration = Duration(seconds: 1);
+
+class NotificationItem {
+  final String id;
+  final SnNotification notification;
+  final DateTime createdAt;
+  final int index;
+  final Duration duration;
+  final bool dismissed;
+
+  NotificationItem({
+    String? id,
+    required this.notification,
+    DateTime? createdAt,
+    required this.index,
+    Duration? duration,
+    this.dismissed = false,
+  }) : id = id ?? const Uuid().v4(),
+       createdAt = createdAt ?? DateTime.now(),
+       duration =
+           duration ?? kNotificationBaseDuration + Duration(seconds: index);
+
+  NotificationItem copyWith({
+    String? id,
+    SnNotification? notification,
+    DateTime? createdAt,
+    int? index,
+    Duration? duration,
+    bool? dismissed,
+  }) {
+    return NotificationItem(
+      id: id ?? this.id,
+      notification: notification ?? this.notification,
+      createdAt: createdAt ?? this.createdAt,
+      index: index ?? this.index,
+      duration: duration ?? this.duration,
+      dismissed: dismissed ?? this.dismissed,
+    );
+  }
+
+  @override
+  bool operator ==(Object other) {
+    if (identical(this, other)) return true;
+    return other is NotificationItem && other.id == id;
+  }
+
+  @override
+  int get hashCode => id.hashCode;
+}
+
+@riverpod
+class NotificationState extends _$NotificationState {
+  final Map<String, Timer> _timers = {};
+
+  @override
+  List<NotificationItem> build() {
+    return [];
+  }
+
+  void add(SnNotification notification, {Duration? duration}) {
+    final newItem = NotificationItem(
+      notification: notification,
+      index: state.length,
+      duration: duration,
+    );
+    state = [...state, newItem];
+    _timers[newItem.id] = Timer(newItem.duration, () => dismiss(newItem.id));
+  }
+
+  void dismiss(String id) {
+    _timers[id]?.cancel();
+    _timers.remove(id);
+    final index = state.indexWhere((item) => item.id == id);
+    if (index != -1) {
+      state = List.from(state)..[index] = state[index].copyWith(dismissed: true);
+    }
+  }
+
+  void remove(String id) {
+    state = state.where((item) => item.id != id).toList();
+  }
+
+  void clear() {
+    for (final timer in _timers.values) {
+      timer.cancel();
+    }
+    _timers.clear();
+    state = [];
+  }
+}