cake_wallet/lib/core/validator.dart

abstract class Validator<T> {
  Validator({required this.errorMessage, this.useAdditionalValidation});

  final String errorMessage;
  final bool Function(T)? useAdditionalValidation;

  bool isValid(T? value);

  String? call(T? value) => !isValid(value) ? errorMessage : null;
}

class TextValidator extends Validator<String> {
  TextValidator({
    bool Function(String)? useAdditionalValidation,
    this.minLength,
    this.maxLength,
    this.pattern,
    String errorMessage = '',
    this.length,
    this.isAutovalidate = false,
  }) : super(
            errorMessage: errorMessage,
            useAdditionalValidation: useAdditionalValidation);

  final int? minLength;
  final int? maxLength;
  final List<int>? length;
  final bool isAutovalidate;
  String? pattern;

  @override
  bool isValid(String? value) {
    if (value == null || value.isEmpty) {
      return isAutovalidate ? true : false;
    }

    final greaterThanMinLength = value.length > (minLength ?? 0);
    if (!greaterThanMinLength) return false;

    final lengthMatched = length?.contains(value.length) ?? true;
    if (!lengthMatched) return false;

    final lowerThanMaxLength =
        (maxLength ?? 0) > 0 ? (value.length <= maxLength!) : true;
    if (!lowerThanMaxLength) return false;

    if (pattern == null) return true;

    final valueMatched = match(value);
    final valueValidated = useAdditionalValidation != null
        ? useAdditionalValidation!(value) || valueMatched
        : valueMatched;

    return valueValidated;
  }

  bool match(String value) =>
      pattern != null ? RegExp(pattern!).hasMatch(value) : false;
}