toQaFunc function

BigInt toQaFunc(String input, Units unit)

Implementation

BigInt toQaFunc(String input, Units unit) {
  String inputStr = num.parse(input).toString();
  String? baseStr = unitMap[unit];

  if (baseStr == null) {
    throw 'No unit of type ${unit} exists.';
  }

  int baseNumDecimals = baseStr.length - 1;

  BigInt base = BigInt.parse(baseStr);

  // Is it negative?
  bool isNegative = inputStr.substring(0, 1) == '-';
  if (isNegative) {
    inputStr = inputStr.substring(1);
  }

  if (inputStr == '.') {
    throw 'type error: Cannot convert ${inputStr} to Qa.';
  }

  // Split it into a whole and fractional part
  List<String> comps = inputStr.split('.'); // eslint-disable-line

  if (comps.length > 2) {
    throw 'too long: Cannot convert ${inputStr} to Qa.';
  }
  String? whole;
  try {
    whole = comps.first;
  } on StateError {
    whole = '0';
  }
  String? fraction = comps.length == 2 ? comps.last : null;

  if (fraction == null) {
    fraction = '0';
  }
  if (fraction.length > baseNumDecimals) {
    throw 'fraction is too long :Cannot convert ${inputStr} to Qa.';
  }

  while (fraction!.length < baseNumDecimals) {
    fraction += '0';
  }

  BigInt wholeBN = BigInt.parse(whole);
  BigInt fractionBN = BigInt.parse(fraction);
  BigInt wei = wholeBN * base + fractionBN;

  if (isNegative) {
    wei = -(wei);
  }

  return BigInt.parse(wei.toString());
}