大幅変更＆環境バージョンアップ

lib/provider/auth_provider.dart

@@ -0,0 +1,31 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:gifunavi/model/auth_user.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+final authUserStateProvider =
+    StateNotifierProvider<AuthUserState, AuthUser>((ref) {
+  return AuthUserState();
+});
+
+class AuthUserState extends StateNotifier<AuthUser> {
+  AuthUserState() : super(AuthUser());
+
+  Future<void> saveToDevice(String val) async {
+    final SharedPreferences prefs = await SharedPreferences.getInstance();
+    await prefs.setString("user_token", val);
+  }
+
+  Future<String?> tokenFromDevice() async {
+    final SharedPreferences prefs = await SharedPreferences.getInstance();
+    return prefs.getString("user_token");
+  }
+
+  Future<void> addLogin(AuthUser user) async {
+    state = user;
+    await saveToDevice(user.auth_token!);
+  }
+
+  void removeLogin() {
+    state = AuthUser();
+  }
+}