/**************************************************************************
**
** Copyright (C) 2017 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Qt Installer Framework.
**
** $QT_BEGIN_LICENSE:GPL-EXCEPT$
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** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 as published by the Free Software
** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
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**************************************************************************/

#include "protocol.h"
#include <QIODevice>

namespace QInstaller {

typedef qint32 PackageSize;

/*!
    Write a packet containing \a command and \a data to \a device.

    \note Both client and server need to have the same endianness.
 */
void sendPacket(QIODevice *device, const QByteArray &command, const QByteArray &data)
{
    // use aliasing for writing payload size into bytes
    char payloadBytes[sizeof(PackageSize)];
    PackageSize *payloadSize = reinterpret_cast<PackageSize*>(&payloadBytes);
    *payloadSize = command.size() + sizeof(char) + data.size();

    QByteArray packet;
    packet.reserve(sizeof(PackageSize) + *payloadSize);
    packet.append(payloadBytes, sizeof(PackageSize));
    packet.append(command);
    packet.append('\0');
    packet.append(data);

    forever {
        const int bytesWritten = device->write(packet);
        Q_ASSERT(bytesWritten >= 0);
        if (bytesWritten == packet.size())
            break;
        packet.remove(0, bytesWritten);
    }
}

/*!
    Reads a packet from \a device, and stores its content into \a command and \a data.

    Returns \c false if the packet in the device buffer is yet incomplete, \c true otherwise.

    \note Both client and server need to have the same endianness.
 */
bool receivePacket(QIODevice *device, QByteArray *command, QByteArray *data)
{
    if (device->bytesAvailable() < static_cast<qint64>(sizeof(PackageSize)))
        return false;

    // read payload size
    char payloadBytes[sizeof(PackageSize)];
    PackageSize *payloadSize = reinterpret_cast<PackageSize*>(&payloadBytes);
    device->read(payloadBytes, sizeof(PackageSize));

    // not enough data yet? back off ...
    if (device->bytesAvailable() < *payloadSize) {
        for (int i = sizeof(PackageSize) - 1; i >= 0; --i)
            device->ungetChar(payloadBytes[i]);
        return false;
    }

    const QByteArray payload = device->read(*payloadSize);
    int separator = payload.indexOf('\0');

    *command = payload.left(separator);
    *data = payload.right(payload.size() - separator - 1);
    return true;
}

} // namespace QInstaller
