/*
 * jignle-s5b.cpp - Jingle SOCKS5 transport
 * Copyright (C) 2019  Sergey Ilinykh
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library.  If not, see <https://www.gnu.org/licenses/>.
 *
 */

#include "jingle-s5b.h"

#include "ice176.h"
#include "jingle-session.h"
#include "jingle.h"
#include "s5b.h"
#include "socks.h"
#include "xmpp/jid/jid.h"
#include "xmpp_client.h"
#include "xmpp_serverinfomanager.h"

#include <QElapsedTimer>
#include <QNetworkInterface>
#include <QTimer>
#if QT_VERSION >= QT_VERSION_CHECK(5, 10, 0)
#include <QRandomGenerator>
#endif

namespace XMPP { namespace Jingle { namespace S5B {
    const QString NS(QStringLiteral("urn:xmpp:jingle:transports:s5b:1"));

    static QString makeKey(const QString &sid, const Jid &j1, const Jid &j2)
    {
        auto data = QString::fromLatin1(
            QCryptographicHash::hash((sid + j1.full() + j2.full()).toUtf8(), QCryptographicHash::Sha1).toHex());
        qDebug() << "Generated key from:" << sid << j1.full() << j2.full() << " = " << data;
        return data;
    }

    class Connection : public XMPP::Jingle::Connection {
        Q_OBJECT

        QList<NetworkDatagram> datagrams;
        SocksClient *          client = nullptr;
        Transport::Mode        mode   = Transport::Tcp;

    public:
        void setSocksClient(SocksClient *client, Transport::Mode mode)
        {
            if (!client || !client->isOpen()) {
                qCritical("Failed to set closed SockClient connection %p", client);
                return;
            }

            this->client = client;
            this->mode   = mode;

            connect(client, &SocksClient::readyRead, this, &Connection::readyRead);
            connect(client, &SocksClient::bytesWritten, this, &Connection::bytesWritten);
            connect(client, &SocksClient::aboutToClose, this, &Connection::aboutToClose);
            setOpenMode(client->openMode());
            emit connected();
        }

        TransportFeatures features() const
        {
            return TransportFeature::Fast | TransportFeature::DataOriented | TransportFeature::StreamOriented
                | TransportFeature::Ordered | TransportFeature::Reliable;
        }

        bool hasPendingDatagrams() const { return datagrams.size() > 0; }

        NetworkDatagram readDatagram(qint64 maxSize = -1)
        {
            Q_UNUSED(maxSize) // TODO or not?
            return datagrams.size() ? datagrams.takeFirst() : NetworkDatagram();
        }

        qint64 bytesAvailable() const
        {
            if (client)
                return client->bytesAvailable();
            else
                return 0;
        }

        qint64 bytesToWrite() const { return client ? client->bytesToWrite() : 0; }

        void close()
        {
            if (!client) {
                // was never opened
                return;
            }
            client->disconnect(this);
            XMPP::Jingle::Connection::close();
            client->deleteLater();
            client = nullptr;
        }

    protected:
        qint64 writeData(const char *data, qint64 maxSize)
        {
            if (mode == Transport::Tcp)
                return client->write(data, maxSize);
            return 0;
        }

        qint64 readData(char *data, qint64 maxSize)
        {
            if (client)
                return client->read(data, maxSize);
            else
                return 0;
        }

    private:
        friend class Transport;
        void enqueueIncomingUDP(const QByteArray &data)
        {
            datagrams.append(NetworkDatagram { data });
            emit readyRead();
        }
    };

    class V6LinkLocalSocksConnector : public QObject {
        Q_OBJECT

        QMap<QString, SocksClient *> clients;
        SocksClient *                client = nullptr;

    public:
        using QObject::QObject;

        void connectToHost(const QHostAddress &proxyHost, int proxyPort, const QString &host, bool udpMode)
        {
            auto const interfaces = QNetworkInterface::allInterfaces();
            for (const QNetworkInterface &ni : interfaces) {
                if (!(ni.flags() & (QNetworkInterface::IsUp | QNetworkInterface::IsRunning))) {
                    continue;
                }
                if (ni.flags() & QNetworkInterface::IsLoopBack) {
                    continue;
                }
                QList<QNetworkAddressEntry> entries = ni.addressEntries();
                for (const QNetworkAddressEntry &na : entries) {
                    QHostAddress ha = na.ip();
                    if (ha.protocol() == QAbstractSocket::IPv6Protocol &&
#if QT_VERSION >= QT_VERSION_CHECK(5, 11, 0)
                        ha.isLinkLocal()
#else
                        XMPP::Ice176::isIPv6LinkLocalAddress(ha)
#endif
                            ) // && proxyHost.isInSubnet(ha, na.prefixLength())
                    {
                        auto client = new SocksClient(this);
                        clients.insert(ni.name(), client);
                        break;
                    }
                }
            }

            if (!clients.size()) {
                emit ready();
                return;
            }

            QHostAddress ph(proxyHost);
            for (auto it = clients.begin(); it != clients.end(); ++it) {
                QString      name   = it.key();
                SocksClient *client = it.value();
                connect(client, &SocksClient::connected, this, [this, name, client]() {
                    this->client = client;
                    clients.remove(name);
                    qDeleteAll(clients);
                    emit ready();
                });
                connect(
                    client, &SocksClient::error, this,
                    [this, name, client](int error) {
                        Q_UNUSED(error)
                        clients.remove(name);
                        delete client;
                        if (clients.isEmpty()) {
                            emit ready();
                        }
                    },
                    Qt::QueuedConnection);
                ph.setScopeId(name);
                client->connectToHost(ph.toString(), proxyPort, host, 0, udpMode);
            }
        }

        SocksClient *takeClient()
        {
            auto c = client;
            if (c) {
                c->setParent(nullptr);
                client = nullptr;
            }
            return c;
        }

    signals:
        void ready();
    };

    class Candidate::Private : public QObject, public QSharedData {
        Q_OBJECT
    public:
        ~Private()
        {
            if (server && transport) {
                server->unregisterKey(transport->directAddr());
            }
            delete socksClient;
        }

        QPointer<Transport> transport;
        QString             cid;
        QString             host;
        Jid                 jid;
        quint16             port     = 0;
        quint32             priority = 0;
        Candidate::Type     type     = Candidate::Direct;
        Candidate::State    state    = Candidate::New;

        QSharedPointer<S5BServer> server;
        SocksClient *             socksClient = nullptr;

        QString toString() const
        {
            QString extra;
            if (type == Tunnel || type == Assisted || type == Direct) {
                extra = QString("host=%1:%2").arg(host, QString::number(port));
            } else if (type == Proxy) {
                extra = QString("proxy=%1 host=%2:%3").arg(jid.full(), host, QString::number(port));
            }
            return QString("Cadidate(type=%1 cid=%2 state=%3 %4)")
                .arg(typeText(type), cid, Candidate::stateText(state), extra);
        }

        void connectToHost(const QString &key, State successState, QObject *callbackContext,
                           std::function<void(bool)> callback, bool isUdp)
        {
            QHostAddress ha(host);
            if (!ha.isNull() && ha.protocol() == QAbstractSocket::IPv6Protocol && ha.scopeId().isEmpty() &&
#if QT_VERSION >= QT_VERSION_CHECK(5, 11, 0)
                ha.isLinkLocal()
#else
                XMPP::Ice176::isIPv6LinkLocalAddress(ha)
#endif
            ) {
                qDebug() << "connect to " << toString() << "with key=" << key << "using V6LinkLocalSocksConnector";
                // we have link local address without scope. We have to enumerate all possible scopes.
                auto v6llConnector = new V6LinkLocalSocksConnector(this);
                connect(v6llConnector, &V6LinkLocalSocksConnector::ready, callbackContext,
                        [this, v6llConnector, callback, successState]() {
                            socksClient = v6llConnector->takeClient();
                            delete v6llConnector;
                            if (state == Candidate::Discarded) {
                                return;
                            }

                            if (socksClient) {
                                state = successState;
                                qDebug() << "connected: " << toString() << "socks client (ipv6)" << socksClient;
                                callback(true);
                                return;
                            }
                            state = Candidate::Discarded;
                            qDebug() << "failed to connect: " << toString() << "no socks client (ipv6)";
                            callback(false);
                        });
                v6llConnector->connectToHost(ha, port, key, isUdp);
            } else {
                socksClient = new SocksClient;
                qDebug() << "connect to " << toString() << "with key=" << key << " and socks client" << socksClient;
                connect(socksClient, &SocksClient::connected, callbackContext, [this, callback, successState]() {
                    if (state == Candidate::Discarded) {
                        return;
                    }
                    state = successState;
                    qDebug() << "connected: " << toString() << "socks client" << socksClient;
                    callback(true);
                });
                connect(socksClient, &SocksClient::error, callbackContext, [this, callback](int error) {
                    Q_UNUSED(error)
                    if (state == Candidate::Discarded) {
                        return;
                    }
                    state = Candidate::Discarded;
                    qDebug() << "failed to connect: " << toString() << "socks client" << socksClient;
                    callback(false);
                });
                // connect(&t, SIGNAL(timeout()), SLOT(trySendUDP()));

                socksClient->connectToHost(host, port, key, 0, isUdp);
            }
        }

        void setupIncomingSocksClient()
        {
            connect(socksClient, &SocksClient::error, this, [this](int error) {
                Q_UNUSED(error)
                state = Candidate::Discarded;
            });
        }
    };

    Candidate::Candidate() { }

    Candidate::Candidate(Transport *transport, const QDomElement &el)
    {
        bool    ok;
        QString host(el.attribute(QStringLiteral("host")));
        Jid     jid(el.attribute(QStringLiteral("jid")));
        auto    portStr = el.attribute(QStringLiteral("port"));
        quint16 port    = 0;
        if (!portStr.isEmpty()) {
            port = portStr.toUShort(&ok);
            if (!ok) {
                return; // make the whole candidate invalid
            }
        }
        auto priorityStr = el.attribute(QStringLiteral("priority"));
        if (priorityStr.isEmpty()) {
            return;
        }
        quint32 priority = priorityStr.toUInt(&ok);
        if (!ok) {
            return; // make the whole candidate invalid
        }
        QString cid = el.attribute(QStringLiteral("cid"));
        if (cid.isEmpty()) {
            return;
        }

        QString ct = el.attribute(QStringLiteral("type"));
        if (ct.isEmpty()) {
            ct = QStringLiteral("direct");
        }
        static QMap<QString, Type> types { { QStringLiteral("assisted"), Assisted },
                                           { QStringLiteral("direct"), Direct },
                                           { QStringLiteral("proxy"), Proxy },
                                           { QStringLiteral("tunnel"), Tunnel } };
        auto                       candidateType = types.value(ct);
        if (ct.isEmpty() || candidateType == None) {
            return;
        }

        if ((candidateType == Proxy && !jid.isValid()) || (candidateType != Proxy && (host.isEmpty() || !port))) {
            return;
        }

        auto d       = new Private;
        d->transport = transport;
        d->cid       = cid;
        d->host      = host;
        d->jid       = jid;
        d->port      = port;
        d->priority  = priority;
        d->type      = candidateType;
        d->state     = New;
        this->d      = d;
    }

    Candidate::Candidate(const Candidate &other) : d(other.d) { }

    Candidate::Candidate(Transport *transport, const Jid &proxy, const QString &cid, quint16 localPreference) :
        d(new Private)
    {
        d->transport = transport;
        d->cid       = cid;
        d->jid       = proxy;
        d->priority  = (ProxyPreference << 16) + localPreference;
        d->type      = Proxy;
        d->state     = Probing; // it's probing because it's a local side proxy and host and port are unknown
    }

    Candidate::Candidate(Transport *transport, const TcpPortServer::Ptr &server, const QString &cid,
                         quint16 localPreference) :
        d(new Private)
    {
        Type type = None;
        switch (server->portType()) {
        case TcpPortServer::Direct:
            type = Candidate::Direct;
            break;
        case TcpPortServer::NatAssited:
            type = Candidate::Assisted;
            break;
        case TcpPortServer::Tunneled:
            type = Candidate::Tunnel;
            break;
        case TcpPortServer::NoType:
            break;
        }

        if (type == None) {
            d.reset();
            return;
        }

        d->transport = transport;
        d->server    = server.staticCast<S5BServer>();
        d->cid       = cid;
        d->host      = server->publishHost();
        d->port      = server->publishPort();
        d->type      = type;
        static const quint32 priorities[]
            = { 0, ProxyPreference, TunnelPreference, AssistedPreference, DirectPreference };
        if (type >= Type(0) && type <= Direct) {
            d->priority = (priorities[type] << 16) + localPreference;
        } else {
            d->priority = 0;
        }

        d->state = New;
    }

    Candidate::~Candidate() { }

    Candidate::Type Candidate::type() const { return d->type; }

    const char *Candidate::typeText(Candidate::Type t)
    {
        switch (t) {
        case None:
            return "Unibitialized";
        case Proxy:
            return "Proxy";
        case Tunnel:
            return "Tunnel";
        case Assisted:
            return "Assisted";
        case Direct:
            return "Direct";
        }
        return "Unknown";
    }

    QString Candidate::cid() const { return d->cid; }

    Jid Candidate::jid() const { return d->jid; }

    QString Candidate::host() const { return d->host; }

    void Candidate::setHost(const QString &host) { d->host = host; }

    quint16 Candidate::port() const { return d->port; }

    void Candidate::setPort(quint16 port) { d->port = port; }

    quint16 Candidate::localPort() const { return quint16(d->server ? d->server->serverPort() : 0); }

    QHostAddress Candidate::localAddress() const { return d->server ? d->server->serverAddress() : QHostAddress(); }

    Candidate::State Candidate::state() const { return d->state; }

    void Candidate::setState(Candidate::State s)
    {
        // don't close sockets here since pending events may change state machine or remote side and closed socket
        // may break it
        d->state = s;
    }

    const char *Candidate::stateText(Candidate::State s)
    {
        switch (s) {
        case New:
            return "New";
        case Probing:
            return "Probing";
        case Pending:
            return "Pending";
        case Unacked:
            return "Unacked";
        case Accepted:
            return "Accepted";
        case Activating:
            return "Activating";
        case Active:
            return "Active";
        case Discarded:
            return "Discarded";
        }
        return nullptr;
    }

    quint32 Candidate::priority() const { return d->priority; }

    QDomElement Candidate::toXml(QDomDocument *doc) const
    {
        auto e = doc->createElement(QStringLiteral("candidate"));
        e.setAttribute(QStringLiteral("cid"), d->cid);
        if (d->type == Proxy) {
            e.setAttribute(QStringLiteral("jid"), d->jid.full());
        }
        if (!d->host.isEmpty() && d->port) {
            e.setAttribute(QStringLiteral("host"), d->host);
            e.setAttribute(QStringLiteral("port"), d->port);
        }
        e.setAttribute(QStringLiteral("priority"), d->priority);

        static const char *types[] = { "proxy", "tunnel", "assisted" }; // same order as in enum
        if (d->type && d->type < Direct) {
            e.setAttribute(QStringLiteral("type"), QLatin1String(types[d->type - 1]));
        }
        return e;
    }

    QString Candidate::toString() const
    {
        if (d) {
            return d->toString();
        } else
            return QString("Candidate(null)");
    }

    // connect to the host and sets successState on success or discards the cadidate.
    // If the candidate was discarded before the connection is finished, then the passed callback won't be called.
    void Candidate::connectToHost(const QString &key, State successState, QObject *callbackContext,
                                  std::function<void(bool)> callback, bool isUdp)
    {
        d->connectToHost(key, successState, callbackContext, callback, isUdp);
    }

    bool Candidate::incomingConnection(SocksClient *sc)
    {
        qDebug() << "incoming connection on" << d->cid << "candidate with socks client" << sc;
        if (d->socksClient) {
            return false;
        }
        d->socksClient = sc;
        d->setupIncomingSocksClient();
        return true;
    }

    SocksClient *Candidate::takeSocksClient()
    {
        qDebug() << "taking socks client" << d->socksClient << "from " << d->cid << "candidate";
        if (!d->socksClient) {
            return nullptr;
        }
        auto c         = d->socksClient;
        d->socksClient = nullptr;
        d->disconnect(c);
        return c;
    }

    void Candidate::deleteSocksClient()
    {
        if (d->socksClient) {
            qDebug("deleting socks client %p", d->socksClient);
            d->socksClient->disconnect();
            delete d->socksClient;
            d->socksClient = nullptr;
        }
    }

    TcpPortServer::Ptr Candidate::server() const { return d->server.staticCast<TcpPortServer>(); }

    bool Candidate::isConnected() const { return d->socksClient != nullptr; }

    bool Candidate::operator==(const Candidate &other) const { return d.data() == other.d.data(); }

    // ------------------------------------------------------------------
    // Transport::Private
    // ------------------------------------------------------------------
    class Transport::Private {
    public:
        enum PendingActions { NewCandidate = 1, CandidateUsed = 2, CandidateError = 4, Activated = 8, ProxyError = 16 };

        Transport *                  q                            = nullptr;
        bool                         p2pAllowed                   = true;
        bool                         offerSent                    = false;
        bool                         waitingAck                   = true;
        bool                         aborted                      = false;
        bool                         remoteReportedCandidateError = false;
        bool                         localReportedCandidateError  = false;
        bool                         proxyDiscoveryInProgress     = false; // if we have valid proxy requests
        quint16                      pendingActions               = 0;
        int                          proxiesInDiscoCount          = 0;
        QStringList                  localCandidatesTrack;
        std::map<QString, Candidate> localCandidates; // cid to candidate mapping
        std::map<QString, Candidate> remoteCandidates;
        Candidate localUsedCandidate;  // we received "candidate-used" for this candidate from localCandidates list
        Candidate remoteUsedCandidate; // we sent "candidate-used" for this candidate from remoteCandidates list
        QString   dstaddr;  // an address for xmpp proxy as it comes from remote. each side calculates it like sha1(sid
                            // + local jid + remote jid)
        QString directAddr; // like dstaddr but for direct connection. Basically it's sha1(sid + initiator jid +
                            // responder jid)
        QString            sid;
        Transport::Mode    mode = Transport::Tcp;
        QTimer             probingTimer;
        QTimer             negotiationFinishTimer;
        QElapsedTimer      lastConnectionStart;
        size_t             blockSize = 8192;
        TcpPortDiscoverer *disco     = nullptr;

        QSharedPointer<Connection> connection;

        // udp stuff
        bool         udpInitialized;
        quint16      udpPort;
        QHostAddress udpAddress;

        Private() : connection(QSharedPointer<Connection>::create()) { }

        inline Jid remoteJid() const { return q->_pad->session()->peer(); }

        QString generateCid() const
        {
            QString cid;
            do {
#if QT_VERSION >= QT_VERSION_CHECK(5, 10, 0)
                cid = QString("%1").arg(QRandomGenerator::global()->generate() & 0xffff, 4, 16, QChar('0'));
#else
                cid = QString("%1").arg(qrand() & 0xffff, 4, 16, QChar('0'));
#endif
            } while (localCandidates.count(cid) || remoteCandidates.count(cid));
            return cid;
        }

        bool isDup(const Candidate &c) const
        {
            for (auto const &[_, rc] : remoteCandidates) {
                if (c.host() == rc.host() && c.port() == rc.port()) {
                    return true;
                }
            }
            return false;
        }

        // queries proxy's host/port and sends the candidate to remote
        void queryS5BProxy(const Jid &j, const QString &cid)
        {
            proxiesInDiscoCount++;
            auto query = new JT_S5B(q->_pad->session()->manager()->client()->rootTask());
            connect(query, &JT_S5B::finished, q, [this, query, cid]() {
                if (!proxyDiscoveryInProgress) {
                    return;
                }
                bool candidateUpdated = false;
                auto it               = localCandidates.find(cid);
                if (it != localCandidates.end() && it->second.state() == Candidate::Probing) {
                    auto &c  = it->second;
                    auto  sh = query->proxyInfo();
                    if (query->success() && !sh.host().isEmpty() && sh.port()) {
                        // it can be discarded by this moment (e.g. got success on a higher priority
                        // candidate). so we have to check.
                        c.setHost(sh.host());
                        c.setPort(quint16(sh.port()));
                        c.setState(Candidate::New);
                        candidateUpdated = true;
                        pendingActions |= Private::NewCandidate;
                    } else {
                        c.setState(Candidate::Discarded);
                    }
                }
                proxiesInDiscoCount--;
                if (!proxiesInDiscoCount) {
                    proxyDiscoveryInProgress = false;
                }
                if (candidateUpdated) {
                    emit q->updated();
                } else if (!proxiesInDiscoCount) {
                    // it's possible it was our last hope and probaby we have to send candidate-error now.
                    checkAndFinishNegotiation();
                }
            });
            query->requestProxyInfo(j);
            query->go(true);
        }

        void discoS5BProxy()
        {
            auto m     = static_cast<Manager *>(q->_pad->manager());
            Jid  proxy = m->userProxy();
            if (proxy.isValid()) {
                Candidate c(q, proxy, generateCid());
                if (!isDup(c)) {
                    qDebug("new local candidate: %s", qPrintable(c.toString()));
                    localCandidates.emplace(c.cid(), c);
                    queryS5BProxy(c.jid(), c.cid());
                }
            }

            proxyDiscoveryInProgress            = true;
            QList<QSet<QString>> featureOptions = { { "http://jabber.org/protocol/bytestreams" } };
            q->_pad->session()->manager()->client()->serverInfoManager()->queryServiceInfo(
                QStringLiteral("proxy"), QStringLiteral("bytestreams"), featureOptions,
                QRegExp("proxy.*|socks.*|stream.*|s5b.*"), ServerInfoManager::SQ_CheckAllOnNoMatch,
                [this](const QList<DiscoItem> &items) {
                    if (!proxyDiscoveryInProgress) { // check if new results are ever/still expected
                        // seems like we have successful connection via higher priority channel. so nobody cares
                        // about proxy
                        return;
                    }
                    auto m         = static_cast<Manager *>(q->_pad->manager());
                    Jid  userProxy = m->userProxy();

                    bool userProxyFound = !userProxy.isValid();
                    for (const auto &i : items) {
                        quint16 localPref = 0;
                        if (!userProxyFound && i.jid() == userProxy) {
                            localPref      = 1;
                            userProxyFound = true;
                            continue;
                        }
                        Candidate c(q, i.jid(), generateCid(), localPref);
                        localCandidates.emplace(c.cid(), c);
                        qDebug("new local candidate: %s", qPrintable(c.toString()));
                        queryS5BProxy(i.jid(), c.cid());
                    }
                    if (!userProxyFound) {
                        Candidate c(q, userProxy, generateCid(), 1);
                        localCandidates.emplace(c.cid(), c);
                        qDebug("new local candidate: %s", qPrintable(c.toString()));
                        queryS5BProxy(userProxy, c.cid());
                    } else if (items.count() == 0) {
                        // seems like we don't have any proxy
                        proxyDiscoveryInProgress = false;
                        checkAndFinishNegotiation();
                    }
                });
        }

        void tryConnectToRemoteCandidate()
        {
            if (q->_state < State::Accepted) {
                return; // will come back later
            }
            quint64          maxProbingPrio = 0;
            quint64          maxNewPrio     = 0;
            Candidate        maxProbing;
            QList<Candidate> maxNew; // keeps highest (same) priority New candidates

            /*
             We have to find highest-priority already connecting candidate and highest-priority new candidate.
             If already-connecting is not found then start connecting to new if it's found.
             If both already-connecting and new are found then
                if new candidate has higher priority or the same priority then start connecting
                else ensure the new candidate starts connecting in 200ms after previous connection attempt
                     (if it's in future then reschedule this call for future)
             In all the other cases just return and wait for events.
            */

            qDebug("tryConnectToRemoteCandidate()");
            for (auto &[cid, c] : remoteCandidates) {
                if (c.state() == Candidate::New) {
                    if (c.priority() > maxNewPrio) {
                        maxNew = QList<Candidate>();
                        maxNew.append(c);
                        maxNewPrio = c.priority();
                    } else if (c.priority() == maxNewPrio) {
                        maxNew.append(c);
                    }
                }
                if (c.state() == Candidate::Probing && c.priority() > maxProbingPrio) {
                    maxProbing     = c;
                    maxProbingPrio = c.priority();
                }
            }
            if (maxNew.isEmpty()) {
                qDebug("  tryConnectToRemoteCandidate() no maxNew candidates");
                return; // nowhere to connect
            }

            // check if we have to hang on for a little if a higher priority candidate is Probing
            if (maxProbing) {
                if (maxNewPrio < maxProbing.priority()) {
                    if (probingTimer.isActive()) {
                        qDebug("  tryConnectToRemoteCandidate() timer is already active. let's wait");
                        return; // we will come back here soon
                    }
                    qint64 msToFuture = 200 - lastConnectionStart.elapsed();
                    if (msToFuture > 0) { // seems like we have to rescheduler for future
                        probingTimer.start(int(msToFuture));
                        qDebug("  tryConnectToRemoteCandidate() too early. timer started. let's wait");
                        return;
                    }
                }
            }
            probingTimer.start(200); // for the next candidate if any

            // now we have to connect to maxNew candidates
            for (auto &mnc : maxNew) {
                lastConnectionStart.start();
                QString key = mnc.type() == Candidate::Proxy ? dstaddr : directAddr;
                mnc.setState(Candidate::Probing);
                mnc.connectToHost(
                    key, Candidate::Pending, q,
                    [this, mnc](bool success) {
                        // candidate's status had to be changed by connectToHost, so we don't set it again
                        if (success) {
                            // let's reject candidates which are meaningless to try
                            bool hasUnckeckedNew = false;
                            for (auto &[cid, c] : remoteCandidates) {
                                if (c.state() == Candidate::New) {
                                    if (c.priority() <= mnc.priority()) {
                                        c.setState(Candidate::Discarded);
                                    } else {
                                        hasUnckeckedNew = true;
                                    }
                                }
                            }
                            if (!hasUnckeckedNew) {
                                pendingActions &= ~Private::NewCandidate; // just if we had it for example after
                                                                          // proxy discovery
                            }
                            setLocalProbingMinimalPreference(mnc.priority() >> 16);
                            updateMinimalPriorityOnConnected();
                        }
                        checkAndFinishNegotiation();
                    },
                    mode == Transport::Udp);
            }
        }

        /**
         * @brief limitTcpDiscoByMinimalPreference take upper part of candidate preference (type preference)
         *        and drops lower priority pending local servers disco
         * @param preference
         */
        void setLocalProbingMinimalPreference(quint32 preference)
        {
            if (proxyDiscoveryInProgress && preference > Candidate::ProxyPreference) {
                proxyDiscoveryInProgress = false; // doesn't make sense anymore
            }

            // and now local ports discoverer..
            if (!disco) {
                return;
            }
            TcpPortServer::PortTypes types = TcpPortServer::NoType;
            if (p2pAllowed) {
                types |= TcpPortServer::Direct;
                if (preference >= Candidate::AssistedPreference) {
                    types |= TcpPortServer::NatAssited;
                }
                if (preference >= Candidate::TunnelPreference) {
                    types |= TcpPortServer::Tunneled;
                }
            }
            disco->setTypeMask(types);
            if (disco->isDepleted()) {
                delete disco;
                disco = nullptr;
            }
        }

        bool hasUnaknowledgedLocalCandidates() const
        {
            // now ensure all local were sent to remote and no hope left
            if (proxyDiscoveryInProgress || (disco && !disco->isDepleted())) {
                qDebug("still has: either s5b proxy or host candidates disco in progress");
                return true;
            }

            // now local candidates
            for (const auto &[_, c] : localCandidates) {
                auto s = c.state();
                if (s == Candidate::Probing || s == Candidate::New || s == Candidate::Unacked) {
                    qDebug("still has: a local candidte cid=%s in %s state", qPrintable(c.cid()),
                           qPrintable(c.stateText(s)));
                    return true;
                }
            }

            return false;
        }

        Candidate preferredUsedCandidate() const
        {
            if (localUsedCandidate) {
                if (remoteUsedCandidate) {
                    if (localUsedCandidate.priority() == remoteUsedCandidate.priority()) {
                        if (q->_pad->session()->role() == Origin::Initiator) {
                            qDebug("Both sides have condidate-used with same priority. Our(inititator) selection is "
                                   "preferred");
                            return remoteUsedCandidate;
                        }
                        qDebug("Both sides have condidate-used with same priority. Remote(initiator) selection is "
                               "preferred");
                        return localUsedCandidate;
                    }
                    return localUsedCandidate.priority() > remoteUsedCandidate.priority() ? localUsedCandidate
                                                                                          : remoteUsedCandidate;
                }
                return localUsedCandidate;
            }
            return remoteUsedCandidate;
        }

        // We come here when both sides reported either candidate-used or candidate-error
        void onBothSidesFinished()
        {
            // so remote seems to be finished too.
            // tell application about it and it has to change its state immediatelly
            auto c          = preferredUsedCandidate();
            bool bothErrors = localReportedCandidateError && remoteReportedCandidateError;
            if (!bothErrors && c) {
                if (c.state() != Candidate::Active) {
                    if (c.type() == Candidate::Proxy) { // local proxy
                        // If it's proxy, first it has to be activated
                        if (c == localUsedCandidate) {
                            if (c.state() == Candidate::Activating) {
                                qDebug("The proxy cid=%s is still activating", qPrintable(c.cid()));
                                return;
                            }
                            // it's our side who offered proxy. so we have to connect to it and activate
                            auto key = makeKey(sid, q->_pad->session()->manager()->client()->jid(),
                                               q->_pad->session()->peer());

                            qDebug("Connect to proxy offered by local side (cid=%s) and activate it",
                                   qPrintable(c.cid()));
                            c.setState(Candidate::Activating);
                            c.connectToHost(
                                key, Candidate::Activating, q,
                                [this, c](bool success) {
                                    if (!success) {
                                        pendingActions |= Private::ProxyError;
                                        emit q->updated();
                                        return;
                                    }

                                    auto query = new JT_S5B(q->_pad->session()->manager()->client()->rootTask());
                                    connect(query, &JT_S5B::finished, q, [this, c, query]() {
                                        if (c.state() != Candidate::Activating) {
                                            qDebug("Proxy candidate cid=%s was changed state while we were "
                                                   "trying "
                                                   "to activate(activate) it. Ignore the result",
                                                   qPrintable(c.cid()));
                                            return;
                                        }
                                        if (!query->success()) {
                                            pendingActions |= Private::ProxyError;
                                            emit q->updated();
                                            return;
                                        }
                                        pendingActions |= Private::Activated;
                                        localUsedCandidate.setState(Candidate::Active);
                                        emit q->updated();
                                        handleConnected(localUsedCandidate);
                                    });
                                    query->requestActivation(localUsedCandidate.jid(), sid, q->_pad->session()->peer());
                                    query->go(true);
                                },
                                mode == Transport::Udp);
                        } // else so it's remote proxy. let's just wait for <activated> from remote
                    } else {
                        c.setState(Candidate::Active);
                    }
                }
                if (c.state() == Candidate::Active) {
                    handleConnected(c);
                } else
                    qDebug("checkAndFinishNegotiation not finished: preferred is not Active");
            } else { // both sides reported candidate error
                q->onFinish(Reason::Condition::ConnectivityError, QLatin1String("both sides reported candidate error"));
            }
        }

        void sendCandidateUsedOrError()
        {
            qDebug("checkAndFinishNegotiation not finished: trying to send condidate-used/error if any");
            // if we are here then neither candidate-used nor candidate-error was sent to remote,
            // but we can send it now.
            // first let's check if we can send candidate-used
            bool    allRemoteDiscarded          = true;
            bool    hasConnectedRemoteCandidate = false;
            QString states;
            for (const auto &[_, c] : remoteCandidates) {
                auto s = c.state();
                states += QString("\n%1").arg(c.toString());
                if (s != Candidate::Discarded) {
                    allRemoteDiscarded = false;
                }
                if (s == Candidate::Pending) { // connected but not yet sent
                    hasConnectedRemoteCandidate = true;
                }
            }
            qDebug().noquote() << "Candidates dump:" << states;

            // if we have connection to remote candidate it's time to send it
            if (hasConnectedRemoteCandidate) {
                pendingActions |= Private::CandidateUsed;
                qDebug("sendCandidateUsedOrError: sending used");
                emit q->updated();
                return;
            }

            if (allRemoteDiscarded) {
                pendingActions |= Private::CandidateError;
                qDebug("sendCandidateUsedOrError: sending error");
                emit q->updated();
                return;
            }

            qDebug("checkAndFinishNegotiation not finished: there are more remote candidates to try");
            // apparently we haven't connected anywhere but there are more remote candidates to try
        }

        void checkAndFinishNegotiation()
        {
            // Why we can't send candidate-used/error right when this happens:
            // so the situation: we discarded all remote candidates (failed to connect)
            // but we have some local candidates which are still in Probing state (upnp for example)
            // if we send candidate-error while we have unsent candidates this may trigger transport failure.
            // So for candidate-error two conditions have to be met 1) all remote failed 2) all local were sent no
            // more local candidates are expected to be discovered

            if (q->_state != State::Connecting) { // if not started or already finished
                qDebug("checkAndFinishNegotiation not finished: q->_state != State::Connecting");
                return;
            }

            // sort out already handled states or states which will bring us here a little later
            if (waitingAck || pendingActions || hasUnaknowledgedLocalCandidates()) {
                // waitingAck some query waits for ack and in the callback this func will be called again
                // pendingActions means we reported to app we have data to send but the app didn't take this data
                // yet, but as soon as it's taken it will switch to waitingAck. And with unacknowledged local
                // candidates we can't send used/error as well as report connected()/failure() until tried them all
                qDebug("checkAndFinishNegotiation not finished: waitingAck=%d || pendingActions=%x || "
                       "hasUnaknowledgedLocalCandidates()=%d",
                       int(waitingAck), int(pendingActions), int(hasUnaknowledgedLocalCandidates()));
                return;
            }

            bool localFinished  = localReportedCandidateError || remoteUsedCandidate;
            bool remoteFinished = remoteReportedCandidateError || localUsedCandidate;

            if (!localFinished || !remoteFinished) {
                qDebug("checkAndFinishNegotiation: local=%s remote=%s", localFinished ? "finished" : "in-progress",
                       remoteFinished ? "finished" : "in-progress");
                if (!localFinished)
                    sendCandidateUsedOrError();
                return;
            }

            onBothSidesFinished();
        }

        // take used-candidate with highest priority and discard all with lower. also update used candidates
        // themselves
        void updateMinimalPriorityOnConnected()
        {
            quint32 prio = 0;
            if (localUsedCandidate && localUsedCandidate.state() != Candidate::Discarded) {
                prio = localUsedCandidate.priority();
            }
            // find highest priority within connected remote candidates
            for (const auto &[_, c] : remoteCandidates) {
                if (c.state() != Candidate::Discarded && c.state() >= Candidate::Pending && c.priority() > prio) {
                    prio = c.priority();
                }
            }

            for (auto &[_, c] : localCandidates) {
                if (c.priority() < prio && c.state() != Candidate::Discarded) {
                    c.setState(Candidate::Discarded);
                }
            }
            for (auto &[_, c] : remoteCandidates) {
                if (c.priority() < prio && c.state() != Candidate::Discarded) {
                    c.setState(Candidate::Discarded);
                }
            }
            prio >>= 16;
            setLocalProbingMinimalPreference(prio);
            // if we discarded "used" candidates then reset them to invalid
            if (localUsedCandidate && localUsedCandidate.state() == Candidate::Discarded) {
                localUsedCandidate = Candidate();
            }
            if (remoteUsedCandidate && remoteUsedCandidate.state() == Candidate::Discarded) {
                remoteUsedCandidate = Candidate();
            }
            if (localUsedCandidate && remoteUsedCandidate) {
                if (q->_pad->session()->role() == Origin::Initiator) {
                    // i'm initiator. see 2.4.4
                    localUsedCandidate.setState(Candidate::Discarded);
                    localUsedCandidate           = Candidate();
                    remoteReportedCandidateError = true; // as a sign of completeness even if not true
                } else {
                    remoteUsedCandidate.setState(Candidate::Discarded);
                    remoteUsedCandidate         = Candidate();
                    localReportedCandidateError = true; // as a sign of completeness even if not true
                }
            }

            // now check and reset NewCandidate pending action
            bool haveNewCandidates = false;
            for (auto &[_, c] : remoteCandidates) {
                if (c.state() == Candidate::New) {
                    haveNewCandidates = true;
                    break;
                }
            }
            if (!haveNewCandidates) {
                pendingActions &= ~NewCandidate;
            }

            negotiationFinishTimer.start();
        }

        void onLocalServerDiscovered()
        {
            bool        hasNewCandidates = false;
            const auto &servers          = disco->takeServers();
            for (const auto &serv : servers) {
                auto s5bserv = serv.staticCast<S5BServer>();
                s5bserv->registerKey(directAddr);
                Candidate c(q, serv, generateCid());
                if (c.isValid() && !isDup(c) && c.priority()) {
                    QObject::connect(s5bserv.data(), &S5BServer::incomingConnection, q,
                                     [this, c](SocksClient *sc, const QString &key) mutable {
                                         if (!connection->client && key == directAddr
                                             && (c.state() == Candidate::Pending || c.state() == Candidate::Unacked)) {
                                             c.incomingConnection(sc);
                                             c.server().data()->disconnect(q); // drop this connection.
                                             if (mode == Transport::Udp)
                                                 sc->grantUDPAssociate("", 0);
                                             else
                                                 sc->grantConnect();
                                             return;
                                         }
                                         qDebug("Reject incoming socks5 connection with key %s (%s)", qPrintable(key),
                                                connection->client ? "already has connection" : "key mismatch");
                                         sc->requestDeny();
                                         sc->deleteLater();
                                     });
                    QObject::connect(
                        s5bserv.data(), &S5BServer::incomingUdp, q,
                        [this, c](bool isInit, const QHostAddress &addr, int sourcePort, const QString &key,
                                  const QByteArray &data) {
                            if (mode != Transport::Mode::Udp || !connection->client) {
                                return false;
                            }

                            if (isInit) {
                                // TODO probably we could create a Connection here and put all the params inside
                                if (udpInitialized)
                                    return false; // only init once

                                // lock on to this sender
                                udpAddress     = addr;
                                udpPort        = quint16(sourcePort);
                                udpInitialized = true;

                                // reply that initialization was successful
                                q->_pad->session()->manager()->client()->s5bManager()->jtPush()->sendUDPSuccess(
                                    q->_pad->session()->peer(), key); // TODO fix ->->->
                                return true;
                            }

                            // not initialized yet?  something went wrong
                            if (!udpInitialized)
                                return false;

                            // must come from same source as when initialized
                            if (addr != udpAddress || sourcePort != udpPort)
                                return false;

                            connection->enqueueIncomingUDP(data); // man_udpReady
                            return true;
                        });
                    localCandidates.emplace(c.cid(), c);
                    qDebug("new local candidate: %s", qPrintable(c.toString()));
                    pendingActions |= NewCandidate;
                    hasNewCandidates = true;
                }
            }
            if (hasNewCandidates) {
                emit q->updated();
            }
        }

        void handleConnected(Candidate &connCand)
        {
            connection->setSocksClient(connCand.takeSocksClient(), mode);
            probingTimer.stop();
            negotiationFinishTimer.stop();
            proxyDiscoveryInProgress = false;
            for (auto &[_, rc] : remoteCandidates) {
                if (rc != connCand && rc.state() == Candidate::Probing) {
                    rc.deleteSocksClient();
                }
            }
            QTimer::singleShot(0, q, [this]() {
                for (const auto &[cid, candidate] : localCandidates) {
                    if (candidate.state() == Candidate::Discarded)
                        localCandidatesTrack.append(cid);
                }
                localCandidates.clear();
                remoteCandidates.clear();
                q->setState(State::Active);
            });
        }

        void handleNegotiationTimeout()
        {
            // probingTimer.stop();
            proxyDiscoveryInProgress = false;
            for (auto &[_, rc] : remoteCandidates) {
                if (rc.state() <= Candidate::Probing) {
                    rc.setState(Candidate::Discarded);
                }
            }
            for (auto &[_, rc] : localCandidates) {
                if (rc.state() <= Candidate::Probing) {
                    rc.setState(Candidate::Discarded);
                }
            }
            checkAndFinishNegotiation();
        }

        bool handleIncomingCandidate(const QDomElement &transportEl)
        {
            QString candidateTag(QStringLiteral("candidate"));
            bool    handled     = false;
            bool    reallyAdded = false;
            for (QDomElement ce = transportEl.firstChildElement(candidateTag); !ce.isNull();
                 ce             = ce.nextSiblingElement(candidateTag)) {
                Candidate c(q, ce);
                if (!c) {
                    throw Stanza::Error(Stanza::Error::Cancel, Stanza::Error::BadRequest);
                }
                if (!p2pAllowed && c.type() != Candidate::Proxy) {
                    qDebug("new remote candidate discarded with forbidden p2p: %s", qPrintable(c));
                } else {
                    qDebug("new remote candidate: %s", qPrintable(c.toString()));
                    remoteCandidates.emplace(c.cid(), c); // TODO check for collisions!
                    reallyAdded = true;
                }
                handled = true;
            }
            if (reallyAdded) {
                pendingActions &= ~CandidateError;
                localReportedCandidateError = false;
                QTimer::singleShot(0, q, [this]() { tryConnectToRemoteCandidate(); });
            }
            return handled;
        }

        bool handleIncomingCandidateUsed(const QDomElement &transportEl)
        {
            QDomElement el = transportEl.firstChildElement(QStringLiteral("candidate-used"));
            if (!el.isNull()) {
                auto cid = QStringLiteral("cid");
                auto it  = localCandidates.find(el.attribute(cid));
                if (it == localCandidates.end()) {
                    if (localCandidatesTrack.contains(cid))
                        return true; // likely discarded as not needed anymore
                    throw Stanza::Error(Stanza::Error::Cancel, Stanza::Error::ItemNotFound,
                                        QString("failed to find incoming candidate-used candidate %1").arg(cid));
                }
                auto &cUsed = it->second;
                if (cUsed.state() == Candidate::Pending) {
                    if (cUsed.type() != Candidate::Proxy && !cUsed.isConnected()) {
                        throw Stanza::Error(
                            Stanza::Error::Cancel, Stanza::Error::NotAcceptable,
                            QString("incoming candidate-used refers a candidate w/o active socks connection: %1")
                                .arg(QString(cUsed)));
                    }
                    cUsed.setState(Candidate::Accepted);
                    localUsedCandidate = cUsed;
                    updateMinimalPriorityOnConnected();
                    QTimer::singleShot(0, q, [this]() { checkAndFinishNegotiation(); });
                } else {
                    // we already rejected the candidate and either remote side already knows about it or will soon
                    // it's possible for example if we were able to connect to higher priority candidate, so
                    // we have o pretend like remote couldn't select anything better but finished already, in other
                    // words like if it sent candidate-error.
                    localUsedCandidate           = Candidate();
                    remoteReportedCandidateError = true;
                }
                return true;
            }
            return false;
        }

        bool handleIncomingCandidateError(const QDomElement &transportEl)
        {
            auto el = transportEl.firstChildElement(QStringLiteral("candidate-error"));
            if (!el.isNull()) {
                remoteReportedCandidateError = true;
                for (auto &[_, c] : localCandidates) {
                    if (c.state() == Candidate::Pending) {
                        c.setState(Candidate::Discarded);
                    }
                }
                qDebug("recv candidate-error: all local pending candidates were discarded");
                QTimer::singleShot(0, q, [this]() { checkAndFinishNegotiation(); });
                return true;
            }
            return false;
        }

        bool handleIncomingActivated(const QDomElement &transportEl)
        {
            auto el = transportEl.firstChildElement(QStringLiteral("activated"));
            if (!el.isNull()) {
                QString cid = el.attribute(QStringLiteral("cid"));
                if (cid.isEmpty()) {
                    throw Stanza::Error(Stanza::Error::Cancel, Stanza::Error::ItemNotFound,
                                        "failed to find incoming activated candidate");
                }
                auto c = remoteUsedCandidate;
                if (!(c.cid() == cid && c.type() == Candidate::Proxy && c.state() == Candidate::Accepted)) {
                    qDebug("Received <activated> on a candidate in an inappropriate state. Ignored.");
                    return true;
                }
                c.setState(Candidate::Active);
                handleConnected(c);
                return true;
            }
            return false;
        }

        bool handleIncomingProxyError(const QDomElement &transportEl)
        {
            auto el = transportEl.firstChildElement(QStringLiteral("proxy-error"));
            if (!el.isNull()) {
                auto it = localCandidates.find(el.attribute(QStringLiteral("cid")));
                if (it == localCandidates.end()) {
                    throw Stanza::Error(Stanza::Error::Cancel, Stanza::Error::ItemNotFound,
                                        "failed to find incoming proxy-error candidate");
                }
                auto &c = it->second;
                if (c != localUsedCandidate || c.state() != Candidate::Accepted) {
                    qDebug("Received <proxy-error> on a candidate in an inappropriate state. Ignored.");
                    return true;
                }

                // if we got proxy-error then the transport has to be considered failed according to spec
                // so never send proxy-error while we have unaknowledged local non-proxy candidates,
                // but we have to follow the standard.

                // Discard everything
                for (auto &[_, c] : localCandidates) {
                    c.setState(Candidate::Discarded);
                }
                for (auto &[_, c] : remoteCandidates) {
                    c.setState(Candidate::Discarded);
                }
                proxyDiscoveryInProgress = false;
                delete disco;

                QTimer::singleShot(0, q, [this]() {
                    q->onFinish(Reason::Condition::ConnectivityError, QLatin1String("got proxy error from the peer"));
                });
                return true;
            }
            return false;
        }
    };

    Transport::Transport(const TransportManagerPad::Ptr &pad, Origin creator) :
        XMPP::Jingle::Transport(pad, creator), d(new Private)
    {
        d->q = this;
        d->probingTimer.setSingleShot(true);
        d->negotiationFinishTimer.setSingleShot(true);
        d->negotiationFinishTimer.setInterval(5000); // TODO select the value smart way
        connect(&d->probingTimer, &QTimer::timeout, this, [this]() { d->tryConnectToRemoteCandidate(); });
        connect(&d->negotiationFinishTimer, &QTimer::timeout, this, [this]() { d->handleNegotiationTimeout(); });
        connect(_pad->manager(), &TransportManager::abortAllRequested, this, [this]() {
            d->aborted = true;
            onFinish(Reason::Condition::Cancel);
        });
    }

    Transport::~Transport()
    {
        if (d) {
            // TODO unregister sid too
            static_cast<Manager *>(_pad.staticCast<Pad>()->manager())->removeKeyMapping(d->directAddr);
            for (auto &[_, c] : d->remoteCandidates) {
                c.deleteSocksClient();
            }
            for (auto &[_, c] : d->remoteCandidates) {
                auto srv = c.server();
                if (srv) {
                    srv.staticCast<S5BServer>()->unregisterKey(d->directAddr);
                }
            }
        }
    }

    void Transport::prepare()
    {
        qDebug("Prepare local offer");
        setState(State::ApprovedToSend);
        auto m = static_cast<Manager *>(_pad.staticCast<Pad>()->manager());
        if (_creator == _pad->session()->role()) { // I'm creator
            d->sid = _pad.staticCast<Pad>()->generateSid();
        }
        _pad.staticCast<Pad>()->registerSid(d->sid);
        d->directAddr = makeKey(d->sid, _pad.staticCast<Pad>()->session()->initiator(),
                                _pad.staticCast<Pad>()->session()->responder());
        m->addKeyMapping(d->directAddr, this);

        auto scope = _pad.staticCast<Pad>()->discoScope();
        d->disco   = scope->disco(); // FIXME store and handle signal. delete when not needed

        connect(d->disco, &TcpPortDiscoverer::portAvailable, this, [this]() { d->onLocalServerDiscovered(); });
        d->setLocalProbingMinimalPreference(0); // allow all on start

        d->discoS5BProxy();

        if (isRemote() && !notifyIncomingConnection(d->connection)) {
            // our the only connection wasn't accepted
            onFinish(Reason::IncompatibleParameters,
                     QLatin1String("Application didn't accept the only incoming connection"));
            return;
        }
        emit updated();
    }

    // we got content acceptance from any side and now can connect
    void Transport::start()
    {
        qDebug("Starting connecting");
        setState(State::Connecting);
        d->tryConnectToRemoteCandidate();
        // if there is no higher priority candidates than ours but they are already connected then
        d->checkAndFinishNegotiation();
    }

    bool Transport::update(const QDomElement &transportEl)
    {
        // we can just on type of elements in transport-info
        // so return as soon as any type handled. Though it leaves a room for  remote to send invalid transport-info
        auto bs = transportEl.attribute(QString::fromLatin1("block-size"));
        if (!bs.isEmpty()) {
            size_t bsn = bs.toULongLong();
            if (bsn && bsn <= d->blockSize) {
                d->blockSize = bsn;
            }
        }
        bool isNewIncoming = _state == State::Created && isRemote();
        if (isNewIncoming && d->sid.isEmpty()) {
            d->sid = transportEl.attribute(QStringLiteral("sid"));
        }
        auto dstaddr = transportEl.attribute(QStringLiteral("dstaddr"));
        if (!dstaddr.isEmpty()) {
            d->dstaddr = dstaddr;
        }

        try {
            if (d->handleIncomingCandidate(transportEl) || d->handleIncomingCandidateUsed(transportEl)
                || d->handleIncomingCandidateError(transportEl) || d->handleIncomingActivated(transportEl)
                || d->handleIncomingProxyError(transportEl)) {
                if (isNewIncoming) {
                    d->connection->setRemote(true);
                    setState(State::Pending);
                }
                if (_state == State::Pending && _creator == _pad->session()->role()) {
                    // initial acceptance by remote of the local transport
                    setState(State::Accepted);
                }
                return true;
            }
        } catch (XMPP::Stanza::Error &e) {
            qWarning("Transport updated failed: %s", qPrintable(e.toString()));
            _lastError = e;
            return false;
        }

        // Seems like we got an empty transport. It's still valid though.
        QTimer::singleShot(0, this, [this]() { d->checkAndFinishNegotiation(); });

        return true;
    }

    bool Transport::hasUpdates() const { return isValid() && d->pendingActions; }

    OutgoingTransportInfoUpdate Transport::takeOutgoingUpdate(bool ensureTransportElement = false)
    {
        qDebug("taking outgoing update");
        OutgoingTransportInfoUpdate upd;
        if (!isValid()) {
            return upd;
        }

        // check where we make initial offer
        bool noPending = (d->localCandidates.empty() && !d->proxyDiscoveryInProgress
                          && !(d->disco && d->disco->inProgressPortTypes()));
        bool initial   = _state == State::ApprovedToSend && !d->offerSent
            && ((!d->pendingActions && noPending) || d->pendingActions & Private::NewCandidate);

        auto makeUpdate = [this, initial](QDomElement tel, bool expectedSuccess = false,
                                          std::function<void(Task *)> cb = std::function<void(Task *)>()) {
            d->waitingAck = true;
            if (initial) {
                _state = State::Unacked;
            }
            return OutgoingTransportInfoUpdate {
                tel,
                [this, cb, expectedSuccess, trptr = QPointer<Transport>(d->q), initial](Task *task) {
                    if (!trptr)
                        return;
                    d->waitingAck = false;
                    if (expectedSuccess && !task->success()) {
                        d->localCandidates.clear();
                        d->remoteCandidates.clear();
                        onFinish(Reason::Condition::FailedTransport, QLatin1String("iq error"));
                    } else if (cb) {
                        if (initial) {
                            _state = isLocal() ? State::Pending : State::Accepted;
                        }
                        cb(task);
                    }
                }
            };
        };

        auto doc = _pad.staticCast<Pad>()->session()->manager()->client()->doc();

        QDomElement tel = doc->createElementNS(NS, "transport");
        tel.setAttribute(QStringLiteral("sid"), d->sid);

        if (initial) {
            if (_creator == _pad->session()->role() && d->mode != Tcp) {
                tel.setAttribute(QStringLiteral("mode"), "udp");
            }
            tel.setAttribute(QString::fromLatin1("block-size"), qulonglong(d->blockSize));
            d->offerSent = true;
        }

        if (d->pendingActions & Private::NewCandidate) {
            d->pendingActions &= ~Private::NewCandidate;
            bool             useProxy = false;
            QList<Candidate> candidatesToSend;
            for (auto &[_, c] : d->localCandidates) {
                if (c.state() != Candidate::New) {
                    continue;
                }
                if (c.type() == Candidate::Proxy) {
                    useProxy = true;
                }
                qDebug("sending local candidate: cid=%s", qPrintable(c.cid()));
                tel.appendChild(c.toXml(doc));
                candidatesToSend.append(c);
                c.setState(Candidate::Unacked);
            }
            if (useProxy) {
                QString dstaddr = makeKey(d->sid, _pad.staticCast<Pad>()->session()->manager()->client()->jid(),
                                          _pad.staticCast<Pad>()->session()->peer());
                tel.setAttribute(QStringLiteral("dstaddr"), dstaddr);
            }
            if (!candidatesToSend.isEmpty()) {
                upd = makeUpdate(tel, false, [this, candidatesToSend, initial](Task *jt) mutable {
                    if (jt->success()) {
                        for (auto &c : candidatesToSend) {
                            if (c.state() == Candidate::Unacked) {
                                c.setState(Candidate::Pending);
                                qDebug("ack: remote side accepted local candidate: cid=%s", qPrintable(c.cid()));
                            }
                        }
                    } else {
                        for (auto &c : candidatesToSend) {
                            if (c.state() == Candidate::Unacked) {
                                c.setState(Candidate::Discarded);
                                qDebug("ack: remote side discarded local candidate: cid=%s", qPrintable(c.cid()));
                            }
                        }
                        d->updateMinimalPriorityOnConnected();
                    }
                    d->checkAndFinishNegotiation();
                });
            } else {
                qWarning("Got NewCandidate pending action but no candidate to send");
            }
        } else if (d->pendingActions & Private::CandidateUsed) {
            d->pendingActions &= ~Private::CandidateUsed;
            // we should have the only remote candidate in Pending state.
            // all other has to be discarded by priority check
            for (auto &it : d->remoteCandidates) {
                auto &c = it.second;
                if (c.state() != Candidate::Pending) {
                    continue;
                }
                qDebug("sending candidate-used: cid=%s", qPrintable(c.cid()));
                auto el = tel.appendChild(doc->createElement(QStringLiteral("candidate-used"))).toElement();
                el.setAttribute(QStringLiteral("cid"), c.cid());
                c.setState(Candidate::Unacked);

                upd = makeUpdate(tel, true, [this, c](Task *) mutable {
                    if (c.state() == Candidate::Unacked) {
                        c.setState(Candidate::Accepted);
                        qDebug("ack: sending candidate-used: cid=%s", qPrintable(c.cid()));
                        d->remoteUsedCandidate = c;
                    }
                    d->checkAndFinishNegotiation();
                });
                break;
            }
            if (std::get<0>(upd).isNull()) {
                qWarning("Got CandidateUsed pending action but no pending candidates");
            }
        } else if (d->pendingActions & Private::CandidateError) {
            d->pendingActions &= ~Private::CandidateError;
            qDebug("sending candidate-error");
            // we are here because all remote are already in Discardd state
            tel.appendChild(doc->createElement(QStringLiteral("candidate-error")));
            upd = makeUpdate(tel, true, [this](Task *) mutable {
                d->localReportedCandidateError = true;
                d->checkAndFinishNegotiation();
            });
        } else if (d->pendingActions & Private::Activated) {
            d->pendingActions &= ~Private::Activated;
            if (d->localUsedCandidate) {
                auto cand = d->localUsedCandidate;
                qDebug("sending activated: cid=%s", qPrintable(cand.cid()));
                auto el = tel.appendChild(doc->createElement(QStringLiteral("activated"))).toElement();
                el.setAttribute(QStringLiteral("cid"), cand.cid());
                upd = makeUpdate(tel, true);
            }
        } else if (d->pendingActions & Private::ProxyError) {
            // we send proxy error only for local proxy
            d->pendingActions &= ~Private::ProxyError;
            if (d->localUsedCandidate) {
                auto cand = d->localUsedCandidate;
                tel.appendChild(doc->createElement(QStringLiteral("proxy-error")));
                qDebug("sending proxy error: cid=%s", qPrintable(cand.cid()));
                upd = makeUpdate(tel, true, [this, cand](Task *task) mutable {
                    qDebug("ack: sending proxy error: cid=%s", qPrintable(cand.cid()));
                    if ((cand.state() != Candidate::Accepted || d->localUsedCandidate != cand) && task->success()) {
                        return; // seems like state was changed while we were waiting for an ack
                    }
                    cand.setState(Candidate::Discarded);
                    d->localUsedCandidate = Candidate();
                    _state                = State::Finished;
                    emit failed();
                });
            } else {
                qWarning("Got ProxyError pending action but no local used candidate is not set");
            }
        } else {
            qDebug("sending empty transport-info");
            upd = makeUpdate(tel, false, [this, initial](Task *jt) mutable {
                if (!jt->success()) {
                    if (initial)
                        onFinish(Reason::FailedTransport, QLatin1String("got it error for initial"));
                    else
                        qWarning("Ignored failed IQ response");
                }
            });
        }

        auto &atel = std::get<0>(upd);
        if (atel.isNull() && ensureTransportElement) {
            atel = tel;
        }

        return upd; // TODO
    }

    bool Transport::isValid() const { return d != nullptr; }

    TransportFeatures Transport::features() const { return _pad->manager()->features(); }

    QString Transport::sid() const { return d->sid; }

    QString Transport::directAddr() const { return d->directAddr; }

    int Transport::maxSupportedChannelsPerComponent(TransportFeatures) const { return 1; }

    XMPP::Jingle::Connection::Ptr Transport::addChannel(TransportFeatures features, const QString &id, int)
    {
        // TODO consider features and create connections here.
        Q_UNUSED(features); // no way create something depending on features
        d->connection->setId(id);
        return d->connection;
    }

    QList<XMPP::Jingle::Connection::Ptr> Transport::channels() const
    {
        // return {}; // good to test transport failure
        return { { d->connection } };
    }

    //----------------------------------------------------------------
    // Manager
    //----------------------------------------------------------------

    class Manager::Private {
    public:
        XMPP::Jingle::Manager *jingleManager = nullptr;

        // FIMME it's reuiqred to split transports by direction otherwise we gonna hit conflicts.
        // jid,transport-sid -> transport mapping
        QSet<QPair<Jid, QString>>   sids;
        QHash<QString, Transport *> key2transport;
        Jid                         proxy;
    };

    Manager::Manager(QObject *parent) : TransportManager(parent), d(new Private) { }

    Manager::~Manager()
    {
        if (d->jingleManager)
            d->jingleManager->unregisterTransport(NS);
    }

    TransportFeatures Manager::features() const
    {
        return TransportFeature::Reliable | TransportFeature::Fast | TransportFeature::DataOriented
            | TransportFeature::Ordered;
    }

    void Manager::setJingleManager(XMPP::Jingle::Manager *jm)
    {
        d->jingleManager = jm;
        if (!jm)
            return;
        // ensure S5BManager is initialized
        QTimer::singleShot(0, this, [this]() {
            if (!d->jingleManager) // unregistered that early?
                return;
            auto jt = d->jingleManager->client()->s5bManager()->jtPush();
            connect(jt, &JT_PushS5B::incomingUDPSuccess, this, [this](const Jid &from, const QString &dstaddr) {
                Q_UNUSED(from)
                auto t = d->key2transport.value(dstaddr);
                if (t) {
                    // TODO return t->incomingUDPSuccess(from);
                }
            });
        });
    }

    QSharedPointer<XMPP::Jingle::Transport> Manager::newTransport(const TransportManagerPad::Ptr &pad, Origin creator)
    {
        return QSharedPointer<Transport>::create(pad, creator).staticCast<XMPP::Jingle::Transport>();
    }

    TransportManagerPad *Manager::pad(Session *session) { return new Pad(this, session); }

    QStringList Manager::discoFeatures() const { return { NS }; }

    void Manager::addKeyMapping(const QString &key, Transport *transport) { d->key2transport.insert(key, transport); }

    void Manager::removeKeyMapping(const QString &key) { d->key2transport.remove(key); }

    QString Manager::generateSid(const Jid &remote)
    {
        auto servers = d->jingleManager->client()->tcpPortReserver()->scope(QString::fromLatin1("s5b"))->allServers();
        QString             sid;
        QPair<Jid, QString> key;
        QString             key1;
        QString             key2;
        auto                servChecker = [&](const TcpPortServer::Ptr &s) {
            return s.staticCast<S5BServer>()->hasKey(key1) || s.staticCast<S5BServer>()->hasKey(key2);
        };

        do {
#if QT_VERSION >= QT_VERSION_CHECK(5, 10, 0)
            sid = QString("s5b_%1").arg(QRandomGenerator::global()->bounded(0x10000), 4, 16, QChar('0'));
#else
            sid = QString("s5b_%1").arg(qrand() & 0xffff, 4, 16, QChar('0'));
#endif
            key  = qMakePair(remote, sid);
            key1 = makeKey(sid, remote, d->jingleManager->client()->jid());
            key2 = makeKey(sid, d->jingleManager->client()->jid(), remote);
        } while (d->sids.contains(key) || std::any_of(servers.begin(), servers.end(), servChecker));
        return sid;
    }

    void Manager::registerSid(const Jid &remote, const QString &sid) { d->sids.insert(qMakePair(remote, sid)); }

    Jid Manager::userProxy() const { return d->proxy; }

    void Manager::setUserProxy(const Jid &jid) { d->proxy = jid; }

    //----------------------------------------------------------------
    // Pad
    //----------------------------------------------------------------
    Pad::Pad(Manager *manager, Session *session) : _manager(manager), _session(session)
    {
        auto reserver = _session->manager()->client()->tcpPortReserver();
        _discoScope   = reserver->scope(QString::fromLatin1("s5b"));
    }

    QString Pad::ns() const { return NS; }

    Session *Pad::session() const { return _session; }

    TransportManager *Pad::manager() const { return _manager; }

    QString Pad::generateSid() const { return _manager->generateSid(_session->peer()); }

    void Pad::registerSid(const QString &sid) { return _manager->registerSid(_session->peer(), sid); }
} // namespace S5B
} // namespace Jingle
} // namespace XMPP

#include "jingle-s5b.moc"
