isValid method

bool isValid(String? gst)

function to check if the provided gst is valid or not.

returns true if the dlNumber seems to be valid.

Implementation

bool isValid(String? gst) {
  if (gst == null) return false;

  if (gst.length != 15) {
    // gst number must be 15 characters long
    return false;
  }

  RegExp gstRegEx = RegExp(
      r"^[0-9]{2}[A-Za-z]{5}[0-9]{4}[A-Za-z]{1}[1-9A-Za-z]{1}(Z|z)[0-9A-Za-z]{1}$");
  if (gstRegEx.hasMatch(gst)) {
    // now validate the checksum digit
    return _validCheckSum(gst);
  }

  return false;
}