validatePhoneNumber function Null safety

Either<ValueObjectFailure<String>, String> validatePhoneNumber(
  1. String input
)

Implementation

Either<ValueObjectFailure<String>, String> validatePhoneNumber(String input) {
  // a valid Kenyan phone number regex
  final RegExp kenyanPhoneRegExp = RegExp(
      r'''^(?:254|\+254|0)?((7|1)(?:(?:[129][0-9])|(?:0[0-8])|(4[0-1]))[0-9]{6})$''');

// a valid US phone number regex
  final RegExp americanPhoneRegExp =
      RegExp(r'''^(\+)(\d{1,})([(]{1}\d{1,3}[)]){0,}\d{2}\d{3}\d{5}$''');

  // a valid UK phone number regex
  final RegExp unitedKingdomRegExp = RegExp(
      r'''^(?:(?:\(?(?:0(?:0|11)\)?[\s-]?\(?|\+)44\)?[\s-]?(?:\(?0\)?[\s-]?)?)|(?:\(?0))(?:(?:\d{5}\)?[\s-]?\d{4,5})|(?:\d{4}\)?[\s-]?(?:\d{5}|\d{3}[\s-]?\d{3}))|(?:\d{3}\)?[\s-]?\d{3}[\s-]?\d{3,4})|(?:\d{2}\)?[\s-]?\d{4}[\s-]?\d{4}))(?:[\s-]?(?:x|ext\.?|\#)\d{3,4})?$''');

  // a generic regex for all international phone numbers. In our case this will suffice to validate Belgium phone numbers and in the future,
  // any new country
  final RegExp genericInternationalRegExp = RegExp(
      r'''\+(9[976]\d|8[987530]\d|6[987]\d|5[90]\d|42\d|3[875]\d|2[98654321]\d|9[8543210]|8[6421]|6[6543210]|5[87654321]|4[987654310]|3[9643210]|2[70]|7|1)\d{1,14}$''');

  if (kenyanPhoneRegExp.hasMatch(input) ||
      (americanPhoneRegExp.hasMatch(input)) ||
      (unitedKingdomRegExp.hasMatch(input)) ||
      (genericInternationalRegExp.hasMatch(input))) {
    return right(input);
  } else {
    return left(
        ValueObjectFailure<String>.invalidPhoneNumber(failedValue: input));
  }
}