added persistence using shared preferences

lib/main.dart

@@ -1,7 +1,10 @@
 import 'package:flutter/material.dart';
 import 'pages/collections_page.dart';
+import 'service/storage.dart';
 
-void main() {
+void main() async {
+  WidgetsFlutterBinding.ensureInitialized();
+  await Storage.initialize();
   runApp(const MapsBookmarks());
 }
 

lib/model/bookmark.dart

@@ -1,11 +1,35 @@
 class Bookmark {
-  Bookmark({required this.name, required this.link});
+  Bookmark({
+    required this.collectionId,
+    required this.name,
+    required this.link,
+    required this.description,
+    int? createdAt,
+  }) : createdAt = createdAt ?? DateTime.now().millisecondsSinceEpoch;
 
-  factory Bookmark.fromJson(Map<String, dynamic> json) =>
-      Bookmark(name: json['name'] as String, link: json['link'] as String);
+  factory Bookmark.fromJson(Map<String, dynamic> json) => Bookmark(
+    collectionId: json['collectionId'] as int,
+    name: json['name'] as String,
+    link: json['link'] as String,
+    description: json['description'] as String,
+    createdAt: json['createdAt'] as int,
+  );
 
+  int collectionId;
   String link;
   String name;
+  String description;
+  int createdAt;
 
-  Map<String, dynamic> toJson() => {'name': name, 'link': link};
+  int get id => createdAt;
+
+  DateTime get createdDate => DateTime.fromMillisecondsSinceEpoch(createdAt);
+
+  Map<String, dynamic> toJson() => {
+    'collectionId': collectionId,
+    'name': name,
+    'link': link,
+    'description': description,
+    'createdAt': createdAt,
+  };
 }

lib/model/collection.dart

@@ -1,10 +1,18 @@
 class Collection {
-  Collection({required this.name});
+  Collection({required this.name, int? createdAt})
+    : createdAt = createdAt ?? DateTime.now().millisecondsSinceEpoch;
 
-  factory Collection.fromJson(Map<String, dynamic> json) =>
-      Collection(name: json['name'] as String);
+  factory Collection.fromJson(Map<String, dynamic> json) => Collection(
+    name: json['name'] as String,
+    createdAt: json['createdAt'] as int,
+  );
 
   String name;
+  int createdAt; // used as Id with millisecondsSinceEpoch
 
-  Map<String, dynamic> toJson() => {'name': name};
+  int get id => createdAt;
+
+  DateTime get createdDate => DateTime.fromMillisecondsSinceEpoch(createdAt);
+
+  Map<String, dynamic> toJson() => {'name': name, 'createdAt': createdAt};
 }

lib/service/storage.dart

@@ -0,0 +1,117 @@
+import 'dart:convert' show jsonDecode, jsonEncode;
+
+import 'package:shared_preferences/shared_preferences.dart';
+
+import '../model/bookmark.dart';
+import '../model/collection.dart';
+
+class Storage {
+  static const String _collectionsKey = 'collections';
+  static const String _bookmarksKey = 'bookmarks';
+  static const String _statsKey = 'stats';
+  static SharedPreferencesWithCache? _prefsWithCache;
+
+  static Future<void> initialize() async {
+    _prefsWithCache = await SharedPreferencesWithCache.create(
+      cacheOptions: const SharedPreferencesWithCacheOptions(
+        allowList: <String>{_collectionsKey, _bookmarksKey, _statsKey},
+      ),
+    );
+  }
+
+  static SharedPreferencesWithCache get _prefs {
+    if (_prefsWithCache == null) {
+      throw StateError(
+        'BookmarkStorage not initialized. Call initialize() first.',
+      );
+    }
+    return _prefsWithCache!;
+  }
+
+  static List<Collection> loadCollections() {
+    final jsonString = _prefs.getString(_collectionsKey) ?? '[]';
+    final jsonList = jsonDecode(jsonString) as List;
+    return jsonList
+        .map((json) => Collection.fromJson(json as Map<String, dynamic>))
+        .toList();
+  }
+
+  static Future<void> saveCollections(List<Collection> collections) async {
+    final jsonList = collections.map((c) => c.toJson()).toList();
+    await _prefs.setString(_collectionsKey, jsonEncode(jsonList));
+  }
+
+  static List<Bookmark> loadAllBookmarks() {
+    final jsonString = _prefs.getString(_bookmarksKey) ?? '[]';
+    final jsonList = jsonDecode(jsonString) as List;
+    return jsonList
+        .map((json) => Bookmark.fromJson(json as Map<String, dynamic>))
+        .toList();
+  }
+
+  static Future<void> saveAllBookmarks(List<Bookmark> bookmarks) async {
+    final jsonList = bookmarks.map((b) => b.toJson()).toList();
+    await _prefs.setString(_bookmarksKey, jsonEncode(jsonList));
+  }
+
+  static List<Bookmark> loadBookmarksForCollection(int collectionId) {
+    final allBookmarks = loadAllBookmarks();
+    return allBookmarks.where((b) => b.collectionId == collectionId).toList();
+  }
+
+  static Future<void> addBookmark(Bookmark bookmark) async {
+    final bookmarks = loadAllBookmarks();
+    bookmarks.add(bookmark);
+    await saveAllBookmarks(bookmarks);
+  }
+
+  static Future<void> deleteBookmarkById(int bookmarkId) async {
+    final bookmarks = loadAllBookmarks();
+    bookmarks.removeWhere((b) => b.id == bookmarkId);
+    await saveAllBookmarks(bookmarks);
+  }
+
+  static Future<void> deleteBookmarksForCollection(int collectionId) async {
+    final bookmarks = loadAllBookmarks();
+    bookmarks.removeWhere((b) => b.collectionId == collectionId);
+    await saveAllBookmarks(bookmarks);
+  }
+
+  static Future<void> updateBookmarkById(
+    int bookmarkId, {
+    String? name,
+    String? description,
+  }) async {
+    final bookmarks = loadAllBookmarks();
+    final index = bookmarks.indexWhere((b) => b.id == bookmarkId);
+
+    if (index == -1) return;
+
+    if (name != null) bookmarks[index].name = name;
+    if (description != null) bookmarks[index].description = description;
+
+    await saveAllBookmarks(bookmarks);
+  }
+
+  static Map<String, int> getStats() {
+    final statsJson = _prefs.getString(_statsKey) ?? '{}';
+    final stats = jsonDecode(statsJson) as Map<String, dynamic>;
+    return {
+      'totalCollections': stats['totalCollections'] ?? 0,
+      'totalBookmarks': stats['totalBookmarks'] ?? 0,
+    };
+  }
+
+  static Future<void> updateStats() async {
+    final collections = loadCollections();
+    final bookmarks = loadAllBookmarks();
+
+    final stats = {
+      'totalCollections': collections.length,
+      'totalBookmarks': bookmarks.length,
+      'lastUpdated': DateTime.now().millisecondsSinceEpoch,
+    };
+
+    await _prefs.setString(_statsKey, jsonEncode(stats));
+  }
+}