convert method

@override String convert(String input)

Converts input and returns the result of the conversion.

Implementation

@override
String convert(String input) {
  final inputLen = input.length;
  final inputRunes = input.runes.toList();

  var n = initialN;
  var i = 0;
  var bias = initialBias;

  // Handle the basic code points:
  // Find the last delimiter
  var b = 0;
  for (var j = 0; j < inputLen; j++) {
    if (isDelimiter(inputRunes[j])) b = j;
  }

  final output = <int>[];
  final caseFlags = <bool>[];

  for (var j = 0; j < b; j++) {
    final cp = inputRunes[j];
    if (!isBasic(cp)) {
      throw FormatException(
        'Invalid input: non-basic code point in literal portion',
      );
    }
    output.add(cp);
    caseFlags.add(_isUpperCaseCodePoint(cp));
  }

  // Main decoding loop:
  var index = b > 0 ? b + 1 : 0;
  while (index < inputLen) {
    final oldi = i;
    var w = 1;
    for (var k = base; ; k += base) {
      if (index >= inputLen) {
        throw FormatException('Invalid input: unexpected end of input');
      }
      final digit = decodeDigit(inputRunes[index++]);
      if (digit == -1) {
        throw FormatException('Invalid input: not a valid digit');
      }

      if (digit > (dartMaxInt - i) ~/ w) {
        throw FormatException('Punycode overflow');
      }
      i += digit * w;

      final t = k <= bias ? tmin : (k >= bias + tmax ? tmax : k - bias);
      if (digit < t) {
        final isUpper = _isUpperCaseCodePoint(inputRunes[index - 1]);

        bias = adapt(i - oldi, output.length + 1, firstTime: oldi == 0);

        if (i ~/ (output.length + 1) > dartMaxInt - n) {
          throw FormatException('Punycode overflow');
        }
        n += i ~/ (output.length + 1);
        i %= output.length + 1;

        caseFlags.insert(i, isUpper);
        output.insert(i, n);
        i++;
        break;
      }

      if (w > dartMaxInt ~/ (base - t)) {
        throw FormatException('Punycode overflow');
      }
      w *= base - t;
    }
  }

  // Apply case flags for mixed-case annotation
  final result = StringBuffer();
  for (var j = 0; j < output.length; j++) {
    result.writeCharCode(_applyCase(output[j], caseFlags[j]));
  }

  return result.toString();
}