validateSecurityCode function

ValidationResults validateSecurityCode(String code, CreditCardType type)

Validates the card's security code based allowed card type's length and whether it contains only numbers

Default length is 3 digits but American Express uses security codes that are 4 digits long

Implementation

ValidationResults validateSecurityCode(String code, CreditCardType type ) {
    String trimmedCode = code.replaceAll(whiteSpaceRegex, '');

    if (trimmedCode.isEmpty) {
      return ValidationResults(
        isValid: false,
        isPotentiallyValid: false,
        message: 'No security code given',
      );
    }

    if (nonNumberRegex.hasMatch(trimmedCode)) {
      return ValidationResults(
        isValid: false,
        isPotentiallyValid: false,
        message: 'Alphabetic characters are not allowed',
      );
    }

    // Set the correct security code length
    int expectedCodeLength = type == CreditCardType.amex
        ? _ALT_SECURITY_CODE_LENGTH
        : _DEFAULT_SECURITY_CODE_LENGTH;

    if (trimmedCode.length < expectedCodeLength) {
      return ValidationResults(
        isValid: false,
        isPotentiallyValid: true,
        message: 'Security code is too short for this card type',
      );
    }
    else if (trimmedCode.length > expectedCodeLength) {
      return ValidationResults(
        isValid: false,
        isPotentiallyValid: false,
        message: 'Security code is too long',
      );
    }

    return ValidationResults(
      isValid: true,
      isPotentiallyValid: true,
    );
  }