fromDucFormatExtern function

Implementation

String? fromDucFormatExtern(String duc, [void Function()? onBad]) {
  try {
    int version = int.parse(duc.substring(0, 1));
    if (version != EPHEMERAL_MODELS_VERSION) {
      Debug().info(
          "Encountered a version mismatch in DUC (Received:$version =/= Local:$EPHEMERAL_MODELS_VERSION) . Failing parse.");
      if (onBad != null) {
        onBad.call();
      }
      return null;
    }
    duc = duc.substring(1);
    String data = utf8.decode(gzip.decode(base64.decode(duc)));
    if (data.substring(0, _keyword.length) != _keyword) {
      return null; // L bozo issue
    } else {
      return data.substring(_keyword.length);
    }
  } on Exception catch (_) {
    return null;
  }
}