flutter_login_widget/lib/src/service/login_validation.dart

import 'package:flutter_login/flutter_login.dart';

class LoginValidationService implements ValidationService {
  const LoginValidationService(this.options);

  final LoginOptions options;

  @override
  String? validateEmail(String? value) {
    if (value == null || value.isEmpty) {
      return options.translations.emailEmpty;
    }
    if (!RegExp(
      r"""(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9]))\.){3}(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9])|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])""",
    ).hasMatch(value)) {
      return options.translations.emailInvalid;
    }
    return null;
  }

  @override
  String? validatePassword(String? value) {
    if (value == null || value.isEmpty) {
      return options.translations.passwordEmpty;
    }
    return null;
  }
}