parse method

@override int parse(String input)

Parses input and returns the numeric value.

Throws FormatException when input cannot be parsed by this codec.

Implementation

@override
int parse(String input) {
  var text = input.trim();
  if (text.isEmpty) {
    throw FormatException('Expected a Japanese cardinal number.', input);
  }

  final negative = text.startsWith('負');
  if (negative) {
    text = text.substring(1);
    if (text.isEmpty) {
      throw FormatException('Expected a Japanese cardinal number.', input);
    }
  }

  if (text.runes.length == 1 &&
      _digitValues[String.fromCharCode(text.runes.single)] == 0) {
    return 0;
  }

  var total = 0;
  var sectionText = StringBuffer();
  var lastSectionUnit = 1000000000000000000;
  for (final char in text.runes.map(String.fromCharCode)) {
    final sectionUnit = _sectionUnitValues[char];
    if (sectionUnit == null) {
      sectionText.write(char);
      continue;
    }

    if (sectionUnit >= lastSectionUnit) {
      throw FormatException('Unexpected Japanese cardinal token.', input);
    }

    final rawSection = sectionText.toString();
    if (rawSection.isEmpty && total > 0) {
      throw FormatException('Unexpected Japanese cardinal token.', input);
    }

    final section = _parseSection(
      rawSection,
      input,
      allowEmptyAsOne: true,
      allowLeadingZero: total > 0,
    );
    if (section == 0) {
      throw FormatException('Unexpected Japanese cardinal token.', input);
    }

    total += section * sectionUnit;
    sectionText = StringBuffer();
    lastSectionUnit = sectionUnit;
  }

  final lowerSection = _parseSection(
    sectionText.toString(),
    input,
    allowEmptyAsOne: false,
    allowLeadingZero: total > 0,
  );
  final value = total + lowerSection;
  return negative ? -value : value;
}