#include <zlib.h>
#include <QtCore/QtEndian>
#include <QtCore/QMetaEnum>
#include <QtDebug>

#include "toqconnection.h"

static const QBluetoothUuid LISTEN_UUID(QLatin1String("00000001-476D-42C4-BD11-9D377C45694F"));
static const int HEADER_LENGTH = 10;
static const int FIRST_CONNECTION_INTERVAL = 10 * 1000;
// Because the watch will actually try to reconnect to us frequently,
// we can afford to set a relaxed interval here.
static const int RETRY_CONNECTION_INTERVAL = 10 * 60 * 1000;

ToqConnection::ToqConnection(QObject *parent) :
	QObject(parent),
	_server(new QBluetoothServer(QBluetoothServiceInfo::RfcommProtocol, this)),
	_socket(0),
	_reconnectTimer(new QTimer(this)),
	_lastTransactionId(0)
{
	connect(_reconnectTimer, &QTimer::timeout,
			this, &ToqConnection::tryConnect);

	_reconnectTimer->setTimerType(Qt::VeryCoarseTimer);
	_reconnectTimer->setSingleShot(true);

	connect(_server, &QBluetoothServer::newConnection,
			this, &ToqConnection::handleServerConnection);

	QBluetoothServiceInfo service = _server->listen(LISTEN_UUID, "PHubCommServer");
	if (service.isValid()) {
		qDebug() << "Started listening on channel" << service.serverChannel();
	} else {
		qWarning() << "Could not register the server service";
	}
}

ToqConnection::Message::Message(Endpoint source, Endpoint destination, quint16 transactionId, quint32 type, const QJsonDocument &payload)
	: source(source), destination(destination), transactionId(transactionId), type(type),
	  payload(payload.toJson(QJsonDocument::Compact))
{

}

QJsonDocument ToqConnection::Message::toJson() const
{
	QJsonDocument doc;
	QJsonParseError error;

	doc = QJsonDocument::fromJson(payload, &error);
	if (error.error) {
		qWarning() << "Failure while parsing message JSON payload: " << error.errorString();
	}

	return doc;
}

QString ToqConnection::nameOfEndpoint(Endpoint ep)
{
	int index = staticMetaObject.indexOfEnumerator("CoreEndpoints");
	QMetaEnum epEnum = staticMetaObject.enumerator(index);
	const char * ret = epEnum.valueToKey(ep);
	if (ret) {
		return QString::fromLatin1(ret);
	} else {
		return QString::number(ep);
	}
}

quint32 ToqConnection::checksum(const QByteArray &data)
{
	uLong crc = crc32(0L, Z_NULL, 0);
	crc = crc32(crc, reinterpret_cast<const Bytef*>(data.constData()), data.size());
	return crc;
}

quint32 ToqConnection::checksum(QIODevice *dev)
{
	uLong crc = crc32(0L, Z_NULL, 0);
	char buffer[4 * 1024];
	qint64 read;
	while ((read = dev->read(buffer, sizeof(buffer))) > 0) {
		crc = crc32(crc, reinterpret_cast<const Bytef*>(&buffer[0]), read);
	}
	return crc;
}

void ToqConnection::setAddress(const QBluetoothAddress &address)
{
	if (address != _address) {
		_address = address;
		if (isConnected()) {
			_socket->disconnectFromService();
		} else {
			_reconnectTimer->start(FIRST_CONNECTION_INTERVAL);
		}
	}
}

quint16 ToqConnection::newTransactionId()
{
	if (_lastTransactionId >= 0xFFFA) {
		// The last transaction ids (as well as 0) seem to be reserved
		// Avoid using them
		_lastTransactionId = 0;
	}

	return ++_lastTransactionId;
}

void ToqConnection::sendMessage(const Message &msg)
{
	if (_socket) {
		_socket->write(packMessage(msg));
	} else {
		qWarning() << "Discarding message because connection is broken";
	}
}

void ToqConnection::disconnectFromDevice()
{
	if (_socket) {
		_socket->disconnectFromService();
	} else {
		qWarning() << "Not connected";
	}
}

ToqConnection::Message ToqConnection::unpackMessage(const QByteArray &data)
{
	Message msg;

	Q_ASSERT(data.length() >= HEADER_LENGTH);
	const uchar *header = reinterpret_cast<const uchar*>(data.constData());

	quint16 message_length = qFromBigEndian<quint16>(&header[2]);
	Q_ASSERT(data.length() == message_length + HEADER_LENGTH - 4);
	msg.source = header[0];
	msg.destination = header[1];
	msg.transactionId = qFromBigEndian<quint16>(&header[4]);
	msg.type = qFromBigEndian<quint32>(&header[6]);
	msg.payload = data.mid(HEADER_LENGTH);

	return msg;
}

QByteArray ToqConnection::packMessage(const Message &msg)
{
	uchar header[HEADER_LENGTH];

	header[0] = msg.source;
	header[1] = msg.destination;
	qToBigEndian<quint16>(msg.payload.length() + 4, &header[2]);
	qToBigEndian<quint16>(msg.transactionId, &header[4]);
	qToBigEndian<quint32>(msg.type, &header[6]);

	QByteArray data;
	data.reserve(HEADER_LENGTH + msg.payload.length());
	data.append(reinterpret_cast<char*>(&header[0]), HEADER_LENGTH);
	data.append(msg.payload);

	return data;
}

void ToqConnection::setSocket(QBluetoothSocket *socket)
{
	Q_ASSERT(!_socket);
	_socket = socket;
	connect(_socket, &QBluetoothSocket::connected,
			this, &ToqConnection::handleSocketConnected);
	connect(_socket, &QBluetoothSocket::disconnected,
			this, &ToqConnection::handleSocketDisconnected);
	connect(_socket, (void (QBluetoothSocket::*)(QBluetoothSocket::SocketError))&QBluetoothSocket::error,
			this, &ToqConnection::handleSocketError);
	connect(_socket, &QBluetoothSocket::readyRead,
			this, &ToqConnection::handleSocketData);
	if (_socket->state() == QBluetoothSocket::ConnectedState) {
		handleSocketConnected();
	}
}

void ToqConnection::tryConnect()
{
	Q_ASSERT(!_socket);

	QBluetoothSocket *socket =
			new QBluetoothSocket(QBluetoothServiceInfo::RfcommProtocol, this);
	setSocket(socket);

	qDebug() << "Connecting to" << _address.toString();

	socket->connectToService(_address, 1);
}

void ToqConnection::handleServerConnection()
{
	qDebug() << "Got a connection from the server";
	QBluetoothSocket *socket = _server->nextPendingConnection();
	if (_socket) {
		// If we have an existing socket, give priority to the received one.
		qDebug() << "Terminating current connection first";
		_socket->disconnectFromService();
		if (_socket) {
			_socket->deleteLater();
			_socket = 0;
		}
	}
	setSocket(socket);
}

void ToqConnection::handleSocketConnected()
{
	qDebug() << "Connected";
	Q_ASSERT(_socket);
	_reconnectTimer->stop();
	emit connected();
	emit connectedChanged();
}

void ToqConnection::handleSocketDisconnected()
{
	if (_socket) {
		qDebug() << "Disconnected";
		Q_ASSERT(_socket->state() == QBluetoothSocket::UnconnectedState ||
				 _socket->state() == QBluetoothSocket::ClosingState);
		_socket->deleteLater();
		_socket = 0;
		if (!_address.isNull()) {
			_reconnectTimer->start(RETRY_CONNECTION_INTERVAL);
		}
		emit disconnected();
		emit connectedChanged();
	}
}

void ToqConnection::handleSocketError(QBluetoothSocket::SocketError error)
{
	if (_socket) {
		qWarning() << error << _socket->errorString();
		_socket->disconnectFromService();
	}
}

void ToqConnection::handleSocketData()
{
	// Keep attempting to read messages as long as at least a header is present
	while (_socket->bytesAvailable() >= HEADER_LENGTH) {
		// Take a look at the header, but do not remove it from the socket input buffer.
		// We will only remove it once we're sure the entire packet is in the buffer.
		uchar header[HEADER_LENGTH];
		_socket->peek(reinterpret_cast<char*>(header), HEADER_LENGTH);

		quint16 message_length = qFromBigEndian<quint16>(&header[2]);

		// Sanity checks on the message_length
		if (message_length == 0) {
			qWarning() << "received empty message";
			_socket->read(HEADER_LENGTH); // skip this header
			continue; // check if there are additional headers.
		}

		// Now wait for the entire message
		if (_socket->bytesAvailable() < HEADER_LENGTH + message_length - 4) {
			qDebug() << "incomplete msg body in read buffer";
			return; // try again once more data comes in
		}

		// We can now safely remove the message from the input buffer,
		// as we know the entire message is in the input buffer.
		QByteArray data = _socket->read(HEADER_LENGTH + message_length - 4);
		Message msg = unpackMessage(data);
		if (msg.transactionId > _lastTransactionId) _lastTransactionId = msg.transactionId;
		emit messageReceived(msg);
	}
}