class PasswordPolicy {
  static const defaultPassword = 'Cc@12345678';

  static final RegExp _validPassword = RegExp(
    r'^(?=.*[A-Z])(?=.*[a-z])(?=.*\d)(?=.*[!#@*&])[A-Za-z\d!#@*&]{8,16}$',
  );

  static bool requiresChange(String? password) {
    return password == defaultPassword;
  }

  static String? validate(String password) {
    if (_validPassword.hasMatch(password)) {
      return null;
    }
    return '密码长度为8-16位，且必须包含大写字母、小写字母、数字和特殊符号（!#@*&）。';
  }
}