decodeHtmlCharacterFromMatch function

String decodeHtmlCharacterFromMatch(Match match)

Decodes HTML entity and numeric character references from the given match.

Implementation

String decodeHtmlCharacterFromMatch(Match match) {
  final text = match.match;
  final entity = match[1];
  final decimalNumber = match[2];
  final hexadecimalNumber = match[3];

  // Entity references, see
  // https://spec.commonmark.org/0.30/#entity-references.
  if (entity != null) {
    return htmlEntitiesMap[text] ?? text;
  }

  // Decimal numeric character references, see
  // https://spec.commonmark.org/0.30/#decimal-numeric-character-references.
  else if (decimalNumber != null) {
    final decimalValue = int.parse(decimalNumber);
    int hexValue;
    if (decimalValue < 1114112 && decimalValue > 1) {
      hexValue = int.parse(decimalValue.toRadixString(16), radix: 16);
    } else {
      hexValue = 0xFFFd;
    }

    return String.fromCharCode(hexValue);
  }

  // Hexadecimal numeric character references, see
  // https://spec.commonmark.org/0.30/#hexadecimal-numeric-character-references.
  else if (hexadecimalNumber != null) {
    var hexValue = int.parse(hexadecimalNumber, radix: 16);
    if (hexValue > 0x10ffff || hexValue == 0) {
      hexValue = 0xFFFd;
    }
    return String.fromCharCode(hexValue);
  }

  return text;
}