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#include "connection.h"

#include <QtNetwork>

static const int TransferTimeout = 30 * 1000;

static const int PongTimeout = 60 * 1000;

static const int PingInterval = 5 * 1000;

static const char SeparatorToken = ' ';

Connection::Connection(QObject *parent)

    : QTcpSocket(parent)

{

    greetingMessage = tr("undefined");

    username = tr("unknown");

    state = WaitingForGreeting;

    currentDataType = Undefined;

    numBytesForCurrentDataType = -1;

    transferTimerId = 0;

    isGreetingMessageSent = false;

    pingTimer.setInterval(PingInterval);

    QObject::connect(this, SIGNAL(readyRead()), this, SLOT(processReadyRead()));

    QObject::connect(this, SIGNAL(disconnected()), &pingTimer, SLOT(stop()));

    QObject::connect(&pingTimer, SIGNAL(timeout()), this, SLOT(sendPing()));

    QObject::connect(this, SIGNAL(connected()),

                     this, SLOT(sendGreetingMessage()));

}

QString Connection::name() const

{

    return username;

}

void Connection::setGreetingMessage(const QString &message)

{

    greetingMessage = message;

}

bool Connection::sendMessage(const QString &message)

{

    if (message.isEmpty())

        return false;

    QByteArray msg = message.toUtf8();

    QByteArray data = "MESSAGE " + QByteArray::number(msg.size()) + ' ' + msg;

    return write(data) == data.size();

}

void Connection::timerEvent(QTimerEvent *timerEvent)

{

    if (timerEvent->timerId() == transferTimerId) {

        abort();

        killTimer(transferTimerId);

        transferTimerId = 0;

    }

}

void Connection::processReadyRead()

{

    if (state == WaitingForGreeting) {

        if (!readProtocolHeader())

            return;

        if (currentDataType != Greeting) {

            abort();

            return;

        }

        state = ReadingGreeting;

    }

    if (state == ReadingGreeting) {

        if (!hasEnoughData())

            return;

        buffer = read(numBytesForCurrentDataType);

        if (buffer.size() != numBytesForCurrentDataType) {

            abort();

            return;

        }

        username = QString(buffer) + '@' + peerAddress().toString() + ':'

                   + QString::number(peerPort());

        currentDataType = Undefined;

        numBytesForCurrentDataType = 0;

        buffer.clear();

        if (!isValid()) {

            abort();

            return;

        }

        if (!isGreetingMessageSent)

            sendGreetingMessage();

        pingTimer.start();

        pongTime.start();

        state = ReadyForUse;

        emit readyForUse();

    }

    do {

        if (currentDataType == Undefined) {

            if (!readProtocolHeader())

                return;

        }

        if (!hasEnoughData())

            return;

        processData();

    } while (bytesAvailable() > 0);

}

void Connection::sendPing()

{

    if (pongTime.elapsed() > PongTimeout) {

        abort();

        return;

    }

    write("PING 1 p");

}

void Connection::sendGreetingMessage()

{

    QByteArray greeting = greetingMessage.toUtf8();

    QByteArray data = "GREETING " + QByteArray::number(greeting.size()) + ' ' + greeting;

    if (write(data) == data.size())

        isGreetingMessageSent = true;

}

int Connection::readDataIntoBuffer(int maxSize)

{

    if (maxSize > MaxBufferSize)

        return 0;

    int numBytesBeforeRead = buffer.size();

    if (numBytesBeforeRead == MaxBufferSize) {

        abort();

        return 0;

    }

    while (bytesAvailable() > 0 && buffer.size() < maxSize) {

        buffer.append(read(1));

        if (buffer.endsWith(SeparatorToken))

            break;

    }

    return buffer.size() - numBytesBeforeRead;

}

int Connection::dataLengthForCurrentDataType()

{

    if (bytesAvailable() <= 0 || readDataIntoBuffer() <= 0

            || !buffer.endsWith(SeparatorToken))

        return 0;

    buffer.chop(1);

    int number = buffer.toInt();

    buffer.clear();

    return number;

}

bool Connection::readProtocolHeader()

{

    if (transferTimerId) {

        killTimer(transferTimerId);

        transferTimerId = 0;

    }

    if (readDataIntoBuffer() <= 0) {

        transferTimerId = startTimer(TransferTimeout);

        return false;

    }

    if (buffer == "PING ") {

        currentDataType = Ping;

    } else if (buffer == "PONG ") {

        currentDataType = Pong;

    } else if (buffer == "MESSAGE ") {

        currentDataType = PlainText;

    } else if (buffer == "GREETING ") {

        currentDataType = Greeting;

    } else {

        currentDataType = Undefined;

        abort();

        return false;

    }

    buffer.clear();

    numBytesForCurrentDataType = dataLengthForCurrentDataType();

    return true;

}

bool Connection::hasEnoughData()

{

    if (transferTimerId) {

        QObject::killTimer(transferTimerId);

        transferTimerId = 0;

    }

    if (numBytesForCurrentDataType <= 0)

        numBytesForCurrentDataType = dataLengthForCurrentDataType();

    if (bytesAvailable() < numBytesForCurrentDataType

            || numBytesForCurrentDataType <= 0) {

        transferTimerId = startTimer(TransferTimeout);

        return false;

    }

    return true;

}

void Connection::processData()

{

    buffer = read(numBytesForCurrentDataType);

    if (buffer.size() != numBytesForCurrentDataType) {

        abort();

        return;

    }

    switch (currentDataType) {

    case PlainText:

        emit newMessage(username, QString::fromUtf8(buffer));

        break;

    case Ping:

        write("PONG 1 p");

        break;

    case Pong:

        pongTime.restart();

        break;

    default:

        break;

    }

    currentDataType = Undefined;

    numBytesForCurrentDataType = 0;

    buffer.clear();

}