chore: add new cache manager

lib/core/app/res/const/app_constant.dart

@@ -4,4 +4,5 @@ class AppConstant {
   static const String appName = 'Flutter Template';
   static const String baseUrl = '';
   static const String getRefreshToken = '';
+  static const String userLocalStorageKey = 'USER_LOCAL_STORAGE_KEY';
 }

lib/core/app/service/interface/i_user_cache_service.dart

@@ -0,0 +1,12 @@
+import 'package:dartz/dartz.dart';
+import 'package:flutter_template/core/shared/data/data_source/error/failure.dart';
+import 'package:flutter_template/core/shared/data/model/user_model.dart';
+
+abstract class IUserCacheService {
+  String get storageKey;
+
+  Future<Either<Failure, User>> fetchUser();
+  Future<bool> saveUser({required User user});
+  Future<bool> deleteUser();
+  Future<bool> hasUser();
+}

lib/core/app/service/user_cache_service.dart

@@ -0,0 +1,43 @@
+import 'dart:convert';
+
+import 'package:dartz/dartz.dart';
+import 'package:flutter_template/core/app/res/const/app_constant.dart';
+import 'package:flutter_template/core/app/service/interface/i_user_cache_service.dart';
+import 'package:flutter_template/core/shared/data/data_source/error/failure.dart';
+import 'package:flutter_template/core/shared/data/data_source/local/interface/storage_service.dart';
+import 'package:flutter_template/core/shared/data/model/user_model.dart';
+
+class UserCacheService implements IUserCacheService {
+  UserCacheService(this.storageService);
+
+  final StorageService storageService;
+
+  @override
+  String get storageKey => AppConstant.userLocalStorageKey;
+
+  @override
+  Future<Either<Failure, User>> fetchUser() async {
+    final data = await storageService.get(storageKey);
+    if (data == null) {
+      return const Left(CacheFailure());
+    }
+    final userJson = jsonDecode(data.toString());
+
+    return Right(User.fromJson(userJson));
+  }
+
+  @override
+  Future<bool> saveUser({required User user}) async {
+    return await storageService.set(storageKey, jsonEncode(user.toJson()));
+  }
+
+  @override
+  Future<bool> deleteUser() async {
+    return await storageService.remove(storageKey);
+  }
+
+  @override
+  Future<bool> hasUser() async {
+    return await storageService.has(storageKey);
+  }
+}

lib/core/shared/data/data_source/error/failure.dart

@@ -16,6 +16,11 @@ class Failure extends Equatable {
   /// Overrides [Equatable]'s props to include the message and metadata for comparison.
   @override
   List<Object> get props => [message, metadata!]; // Forces metadata to be non-null.
+
+  /// Overrides [Equatable]'s toString method to return the message.
+  /// This is useful for debugging purposes.
+  @override
+  String toString() => 'Failure: $message\nMetadata: $metadata';
 }
 
 /// A subclass of [Failure] representing a default failure case.
@@ -31,3 +36,10 @@ class CancelTokenFailure extends Failure {
 
   const CancelTokenFailure(super.errorMessage, this.statusCode);
 }
+
+/// A subclass of [Failure] representing a cache failure case.
+/// Uses a cache error message from [ResponseMessage].
+/// This is used when a cache operation fails.
+class CacheFailure extends Failure {
+  const CacheFailure() : super(ResponseMessage.cacheError);
+}

lib/core/shared/data/data_source/local/interface/storage_service.dart

@@ -0,0 +1,16 @@
+/// Storage service interface
+abstract class StorageService {
+  void init();
+
+  bool get hasInitialized;
+
+  Future<bool> remove(String key);
+
+  Future<Object?> get(String key);
+
+  Future<bool> set(String key, String data);
+
+  Future<bool> has(String key);
+
+  Future<void> clear();
+}

lib/core/shared/data/data_source/local/shared_prefs_storage_service.dart

@@ -0,0 +1,48 @@
+import 'dart:async';
+
+import 'package:flutter_template/core/shared/data/data_source/local/interface/storage_service.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+class SharedPrefsStorageService implements StorageService {
+  SharedPreferences? _sharedPreferences;
+
+  final Completer<SharedPreferences> initCompleter = Completer<SharedPreferences>();
+
+  @override
+  void init() {
+    initCompleter.complete(SharedPreferences.getInstance());
+  }
+
+  @override
+  bool get hasInitialized => _sharedPreferences != null;
+
+  @override
+  Future<Object?> get(String key) async {
+    _sharedPreferences = await initCompleter.future;
+    return _sharedPreferences!.get(key);
+  }
+
+  @override
+  Future<void> clear() async {
+    _sharedPreferences = await initCompleter.future;
+    await _sharedPreferences!.clear();
+  }
+
+  @override
+  Future<bool> has(String key) async {
+    _sharedPreferences = await initCompleter.future;
+    return _sharedPreferences?.containsKey(key) ?? false;
+  }
+
+  @override
+  Future<bool> remove(String key) async {
+    _sharedPreferences = await initCompleter.future;
+    return await _sharedPreferences!.remove(key);
+  }
+
+  @override
+  Future<bool> set(String key, data) async {
+    _sharedPreferences = await initCompleter.future;
+    return await _sharedPreferences!.setString(key, data);
+  }
+}

lib/core/shared/data/model/user_model.dart

@@ -0,0 +1,60 @@
+// ignore_for_file: public_member_api_docs, sort_constructors_first
+import 'dart:convert';
+
+import 'package:equatable/equatable.dart';
+
+class User extends Equatable {
+  final String id;
+  final String name;
+  final String email;
+  final String? imageUrl;
+
+  const User({
+    required this.id,
+    required this.name,
+    required this.email,
+    this.imageUrl,
+  });
+
+  @override
+  List<Object> get props => [id, name, email, imageUrl ?? ''];
+
+  User copyWith({
+    String? id,
+    String? name,
+    String? email,
+    String? imageUrl,
+  }) {
+    return User(
+      id: id ?? this.id,
+      name: name ?? this.name,
+      email: email ?? this.email,
+      imageUrl: imageUrl ?? this.imageUrl,
+    );
+  }
+
+  Map<String, dynamic> toMap() {
+    return <String, dynamic>{
+      'id': id,
+      'name': name,
+      'email': email,
+      'image_url': imageUrl,
+    };
+  }
+
+  factory User.fromMap(Map<String, dynamic> map) {
+    return User(
+      id: map['id'] as String,
+      name: map['name'] as String,
+      email: map['email'] as String,
+      imageUrl: map['image_url'] != null ? map['image_url'] as String : null,
+    );
+  }
+
+  String toJson() => json.encode(toMap());
+
+  factory User.fromJson(String source) => User.fromMap(json.decode(source) as Map<String, dynamic>);
+
+  @override
+  bool get stringify => true;
+}