parseHandshakeResponse method

ParseHandshakeResponseResult parseHandshakeResponse(Object? data)

Parse the handshake reponse data: either a string (json) or a Uint8List (binary) of the handshake response data.

Implementation

ParseHandshakeResponseResult parseHandshakeResponse(Object? data) {
  HandshakeResponseMessage responseMessage;
  String messageData;
  Object? remainingData;

  if (data is Uint8List) {
    // Format is binary but still need to read JSON text from handshake response
    int separatorIndex = data.indexOf(TextMessageFormat.RecordSeparatorCode);
    if (separatorIndex == -1) {
      throw new GeneralError("Message is incomplete.");
    }

    // content before separator is handshake response
    // optional content after is additional messages
    final responseLength = separatorIndex + 1;
    messageData = utf8.decode(data.sublist(0, responseLength));
    remainingData = (data.length > responseLength)
        ? data.sublist(responseLength, data.length)
        : null;
  } else {
    final String textData = data as String;
    final separatorIndex =
        textData.indexOf(TextMessageFormat.recordSeparator);
    if (separatorIndex == -1) {
      throw new GeneralError("Message is incomplete.");
    }

    // content before separator is handshake response
    // optional content after is additional messages
    final responseLength = separatorIndex + 1;
    messageData = textData.substring(0, responseLength);
    remainingData = (textData.length > responseLength)
        ? textData.substring(responseLength)
        : null;
  }

  // At this point we should have just the single handshake message
  final messages = TextMessageFormat.parse(messageData);
  final response =
      HandshakeResponseMessage.fromJson(json.decode(messages[0]));

  // NOTE: The fromJson should have thrown an error before this check would be required.
  // if (response.type) {
  //     throw new Error("Expected a handshake response from the server.");
  // }

  responseMessage = response;

  // multiple messages could have arrived with handshake
  // return additional data to be parsed as usual, or null if all parsed
  return ParseHandshakeResponseResult(remainingData, responseMessage);
}