dart: filter shortcodes

main.dart

String filterShortcodes(String input,
    {String opening = '[', String closing = ']'}) {
  assert(opening.runes.length == 1);
  assert(closing.runes.length == 1);
  final openingRune = opening.runes.first;
  final closingRune = closing.runes.first;
  bool filter = false;
  final buf = StringBuffer();
  for (final rune in input.runes) {
    if (filter == false && rune == openingRune) {
      filter = true;
    } else if (filter == true && rune == closingRune) {
      filter = false;
    } else if (!filter) {
      buf.write(String.fromCharCode(rune));
    }
  }
  return buf.toString();
}

void main() {
  var input = '<p>[var @ example] <h1>Title</h1>[visual compose]</p>';
  print(filterShortcodes(input));
}