isValidIBANChecksum function

bool isValidIBANChecksum(String iban)

Calculate checksum of IBAN and compares it with checksum provided in IBAN Registry

@ignore

Implementation

bool isValidIBANChecksum(String iban) {
  final String countryCode = iban.substring(0, 2);
  final int providedChecksum = int.parse(iban.substring(2, 4), radix: 10);
  final String bban = iban.substring(4);

  // Wikipedia[validating_iban] says there are a specif way to check if a IBAN is valid but
  // it. It says 'If the remainder is 1, the check digit test is passed and the
  // IBAN might be valid.'. might, MIGHT!
  // We don't want might but want yes or no. Since every BBAN is IBAN from the fifth
  // (slice(4)) we can generate the IBAN from BBAN and country code(two first characters)
  // from in the IBAN.
  // To generate the (generate the iban check digits)[generating-iban-check]
  //   Move the country code to the end
  //   remove the checksum from the begging
  //   Add "00" to the end
  //   modulo 97 on the amount
  //   subtract remainder from 98, (98 - remainder)
  //   Add a leading 0 if the remainder is less then 10 (padStart(2, "0")) (we skip this
  //     since we compare int, not string)
  //
  // [validating_iban][https://en.wikipedia.org/wiki/International_Bank_Account_Number#Validating_the_IBAN]
  // [generating-iban-check][https://en.wikipedia.org/wiki/International_Bank_Account_Number#Generating_IBAN_check_digits]

  final String validationString =
      replaceCharacterWithCode('$bban${countryCode}00');
  final int rest = mod9710(validationString);

  return 98 - rest == providedChecksum;
}