// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

#include "qhttpnetworkconnection_p.h"
#include "qhttp2protocolhandler_p.h"

#include "http2/http2frames_p.h"
#include "http2/bitstreams_p.h"

#include <private/qnoncontiguousbytedevice_p.h>

#include <QtNetwork/qabstractsocket.h>

#include <QtCore/qloggingcategory.h>
#include <QtCore/qendian.h>
#include <QtCore/qdebug.h>
#include <QtCore/qlist.h>
#include <QtCore/qnumeric.h>
#include <QtCore/qurl.h>

#include <qhttp2configuration.h>

#ifndef QT_NO_NETWORKPROXY
#include <QtNetwork/qnetworkproxy.h>
#endif

#include <qcoreapplication.h>

#include <algorithm>
#include <vector>
#include <optional>

QT_BEGIN_NAMESPACE

using namespace Qt::StringLiterals;

namespace
{

HPack::HttpHeader build_headers(const QHttpNetworkRequest &request, quint32 maxHeaderListSize,
                                bool useProxy)
{
    using namespace HPack;

    HttpHeader header;
    header.reserve(300);

    // 1. Before anything - mandatory fields, if they do not fit into maxHeaderList -
    // then stop immediately with error.
    const auto auth = request.url().authority(QUrl::FullyEncoded | QUrl::RemoveUserInfo).toLatin1();
    header.emplace_back(":authority", auth);
    header.emplace_back(":method", request.methodName());
    header.emplace_back(":path", request.uri(useProxy));
    header.emplace_back(":scheme", request.url().scheme().toLatin1());

    HeaderSize size = header_size(header);
    if (!size.first) // Ooops!
        return HttpHeader();

    if (size.second > maxHeaderListSize)
        return HttpHeader(); // Bad, we cannot send this request ...

    const QHttpHeaders requestHeader = request.header();
    for (qsizetype i = 0; i < requestHeader.size(); ++i) {
        const auto name = requestHeader.nameAt(i);
        const auto value = requestHeader.valueAt(i);
        const HeaderSize delta = entry_size(name, value);
        if (!delta.first) // Overflow???
            break;
        if (std::numeric_limits<quint32>::max() - delta.second < size.second)
            break;
        size.second += delta.second;
        if (size.second > maxHeaderListSize)
            break;

        if (name == "connection"_L1 || name == "host"_L1 || name == "keep-alive"_L1
            || name == "proxy-connection"_L1 || name == "transfer-encoding"_L1) {
            continue; // Those headers are not valid (section 3.2.1) - from QSpdyProtocolHandler
        }
        // TODO: verify with specs, which fields are valid to send ....
        //
        // Note: RFC 7450 8.1.2 (HTTP/2) states that header field names must be lower-cased
        // prior to their encoding in HTTP/2; header name fields in QHttpHeaders are already
        // lower-cased
        header.emplace_back(QByteArray{name.data(), name.size()},
                            QByteArray{value.data(), value.size()});
    }

    return header;
}

QUrl urlkey_from_request(const QHttpNetworkRequest &request)
{
    QUrl url;

    url.setScheme(request.url().scheme());
    url.setAuthority(request.url().authority(QUrl::FullyEncoded | QUrl::RemoveUserInfo));
    url.setPath(QLatin1StringView(request.uri(false)));

    return url;
}

}// Unnamed namespace

// Since we anyway end up having this in every function definition:
using namespace Http2;

QHttp2ProtocolHandler::QHttp2ProtocolHandler(QHttpNetworkConnectionChannel *channel)
    : QAbstractProtocolHandler(channel),
      decoder(HPack::FieldLookupTable::DefaultSize),
      encoder(HPack::FieldLookupTable::DefaultSize, true)
{
    Q_ASSERT(channel && m_connection);
    continuedFrames.reserve(20);

    const auto h2Config = m_connection->http2Parameters();
    maxSessionReceiveWindowSize = h2Config.sessionReceiveWindowSize();
    pushPromiseEnabled = h2Config.serverPushEnabled();
    streamInitialReceiveWindowSize = h2Config.streamReceiveWindowSize();
    encoder.setCompressStrings(h2Config.huffmanCompressionEnabled());

    if (!channel->ssl && m_connection->connectionType() != QHttpNetworkConnection::ConnectionTypeHTTP2Direct) {
        // We upgraded from HTTP/1.1 to HTTP/2. channel->request was already sent
        // as HTTP/1.1 request. The response with status code 101 triggered
        // protocol switch and now we are waiting for the real response, sent
        // as HTTP/2 frames.
        Q_ASSERT(channel->reply);
        const quint32 initialStreamID = createNewStream(HttpMessagePair(channel->request, channel->reply),
                                                        true /* uploaded by HTTP/1.1 */);
        Q_ASSERT(initialStreamID == 1);
        Stream &stream = activeStreams[initialStreamID];
        stream.state = Stream::halfClosedLocal;
    }
}

void QHttp2ProtocolHandler::handleConnectionClosure()
{
    // The channel has just received RemoteHostClosedError and since it will
    // not try (for HTTP/2) to re-connect, it's time to finish all replies
    // with error.

    // Maybe we still have some data to read and can successfully finish
    // a stream/request?
    _q_receiveReply();

    // Finish all still active streams. If we previously had GOAWAY frame,
    // we probably already closed some (or all) streams with ContentReSend
    // error, but for those still active, not having any data to finish,
    // we now report RemoteHostClosedError.
    const auto errorString = QCoreApplication::translate("QHttp", "Connection closed");
    for (auto it = activeStreams.begin(), eIt = activeStreams.end(); it != eIt; ++it)
        finishStreamWithError(it.value(), QNetworkReply::RemoteHostClosedError, errorString);

    // Make sure we'll never try to read anything later:
    activeStreams.clear();
    goingAway = true;
}

void QHttp2ProtocolHandler::ensureClientPrefaceSent()
{
    if (!prefaceSent)
        sendClientPreface();
}

void QHttp2ProtocolHandler::_q_uploadDataReadyRead()
{
    if (!sender()) // QueuedConnection, firing after sender (byte device) was deleted.
        return;

    auto data = qobject_cast<QNonContiguousByteDevice *>(sender());
    Q_ASSERT(data);
    const qint32 streamID = streamIDs.value(data);
    Q_ASSERT(streamID != 0);
    Q_ASSERT(activeStreams.contains(streamID));
    auto &stream = activeStreams[streamID];

    if (!sendDATA(stream)) {
        finishStreamWithError(stream, QNetworkReply::UnknownNetworkError, "failed to send DATA"_L1);
        sendRST_STREAM(streamID, INTERNAL_ERROR);
        markAsReset(streamID);
        deleteActiveStream(streamID);
    }
}

void QHttp2ProtocolHandler::_q_replyDestroyed(QObject *reply)
{
    const quint32 streamID = streamIDs.take(reply);
    if (activeStreams.contains(streamID)) {
        sendRST_STREAM(streamID, CANCEL);
        markAsReset(streamID);
        deleteActiveStream(streamID);
    }
}

void QHttp2ProtocolHandler::_q_uploadDataDestroyed(QObject *uploadData)
{
    streamIDs.remove(uploadData);
}

void QHttp2ProtocolHandler::_q_readyRead()
{
    if (!goingAway || activeStreams.size())
        _q_receiveReply();
}

void QHttp2ProtocolHandler::_q_receiveReply()
{
    Q_ASSERT(m_socket);
    Q_ASSERT(m_channel);

    if (goingAway && activeStreams.isEmpty()) {
        m_channel->close();
        return;
    }

    while (!goingAway || activeStreams.size()) {
        const auto result = frameReader.read(*m_socket);
        switch (result) {
        case FrameStatus::incompleteFrame:
            return;
        case FrameStatus::protocolError:
            return connectionError(PROTOCOL_ERROR, "invalid frame");
        case FrameStatus::sizeError:
            return connectionError(FRAME_SIZE_ERROR, "invalid frame size");
        default:
            break;
        }

        Q_ASSERT(result == FrameStatus::goodFrame);

        inboundFrame = std::move(frameReader.inboundFrame());

        const auto frameType = inboundFrame.type();
        if (continuationExpected && frameType != FrameType::CONTINUATION)
            return connectionError(PROTOCOL_ERROR, "CONTINUATION expected");

        switch (frameType) {
        case FrameType::DATA:
            handleDATA();
            break;
        case FrameType::HEADERS:
            handleHEADERS();
            break;
        case FrameType::PRIORITY:
            handlePRIORITY();
            break;
        case FrameType::RST_STREAM:
            handleRST_STREAM();
            break;
        case FrameType::SETTINGS:
            handleSETTINGS();
            break;
        case FrameType::PUSH_PROMISE:
            handlePUSH_PROMISE();
            break;
        case FrameType::PING:
            handlePING();
            break;
        case FrameType::GOAWAY:
            handleGOAWAY();
            break;
        case FrameType::WINDOW_UPDATE:
            handleWINDOW_UPDATE();
            break;
        case FrameType::CONTINUATION:
            handleCONTINUATION();
            break;
        case FrameType::LAST_FRAME_TYPE:
            // 5.1 - ignore unknown frames.
            break;
        }
    }
}

bool QHttp2ProtocolHandler::sendRequest()
{
    if (goingAway) {
        // Stop further calls to this method: we have received GOAWAY
        // so we cannot create new streams.
        m_channel->emitFinishedWithError(QNetworkReply::ProtocolUnknownError,
                                         "GOAWAY received, cannot start a request");
        m_channel->h2RequestsToSend.clear();
        return false;
    }

    // Process 'fake' (created by QNetworkAccessManager::connectToHostEncrypted())
    // requests first:
    auto &requests = m_channel->h2RequestsToSend;
    for (auto it = requests.begin(), endIt = requests.end(); it != endIt;) {
        const auto &pair = *it;
        if (pair.first.isPreConnect()) {
            m_connection->preConnectFinished();
            emit pair.second->finished();
            it = requests.erase(it);
            if (!requests.size()) {
                // Normally, after a connection was established and H2
                // was negotiated, we send a client preface. connectToHostEncrypted
                // though is not meant to send any data, it's just a 'preconnect'.
                // Thus we return early:
                return true;
            }
        } else {
            ++it;
        }
    }

    if (!prefaceSent && !sendClientPreface())
        return false;

    if (!requests.size())
        return true;

    m_channel->state = QHttpNetworkConnectionChannel::WritingState;
    // Check what was promised/pushed, maybe we do not have to send a request
    // and have a response already?

    for (auto it = requests.begin(), endIt = requests.end(); it != endIt;) {
        const auto key = urlkey_from_request(it->first).toString();
        if (!promisedData.contains(key)) {
            ++it;
            continue;
        }
        // Woo-hoo, we do not have to ask, the answer is ready for us:
        HttpMessagePair message = *it;
        it = requests.erase(it);
        initReplyFromPushPromise(message, key);
    }

    const auto isClientSide = [](const auto &pair) -> bool { return (pair.first & 1) == 1; };
    const auto activeClientSideStreams = std::count_if(
            activeStreams.constKeyValueBegin(), activeStreams.constKeyValueEnd(), isClientSide);
    const qint64 streamsToUse = qBound(0, qint64(maxConcurrentStreams) - activeClientSideStreams,
                                       requests.size());
    auto it = requests.begin();
    for (qint64 i = 0; i < streamsToUse; ++i) {
        const qint32 newStreamID = createNewStream(*it);
        if (!newStreamID) {
            // TODO: actually we have to open a new connection.
            qCCritical(QT_HTTP2, "sendRequest: out of stream IDs");
            break;
        }

        it = requests.erase(it);

        Stream &newStream = activeStreams[newStreamID];
        if (!sendHEADERS(newStream)) {
            finishStreamWithError(newStream, QNetworkReply::UnknownNetworkError,
                                  "failed to send HEADERS frame(s)"_L1);
            deleteActiveStream(newStreamID);
            continue;
        }

        if (newStream.data() && !sendDATA(newStream)) {
            finishStreamWithError(newStream, QNetworkReply::UnknownNetworkError,
                                  "failed to send DATA frame(s)"_L1);
            sendRST_STREAM(newStreamID, INTERNAL_ERROR);
            markAsReset(newStreamID);
            deleteActiveStream(newStreamID);
        }
    }

    m_channel->state = QHttpNetworkConnectionChannel::IdleState;

    return true;
}


bool QHttp2ProtocolHandler::sendClientPreface()
{
     // 3.5 HTTP/2 Connection Preface
    Q_ASSERT(m_socket);

    if (prefaceSent)
        return true;

    const qint64 written = m_socket->write(Http2::Http2clientPreface,
                                           Http2::clientPrefaceLength);
    if (written != Http2::clientPrefaceLength)
        return false;

    // 6.5 SETTINGS
    frameWriter.setOutboundFrame(Http2::configurationToSettingsFrame(m_connection->http2Parameters()));
    Q_ASSERT(frameWriter.outboundFrame().payloadSize());

    if (!frameWriter.write(*m_socket))
        return false;

    sessionReceiveWindowSize = maxSessionReceiveWindowSize;
    // We only send WINDOW_UPDATE for the connection if the size differs from the
    // default 64 KB:
    const auto delta = maxSessionReceiveWindowSize - Http2::defaultSessionWindowSize;
    if (delta && !sendWINDOW_UPDATE(Http2::connectionStreamID, delta))
        return false;

    prefaceSent = true;
    waitingForSettingsACK = true;

    return true;
}

bool QHttp2ProtocolHandler::sendSETTINGS_ACK()
{
    Q_ASSERT(m_socket);

    if (!prefaceSent && !sendClientPreface())
        return false;

    frameWriter.start(FrameType::SETTINGS, FrameFlag::ACK, Http2::connectionStreamID);

    return frameWriter.write(*m_socket);
}

bool QHttp2ProtocolHandler::sendHEADERS(Stream &stream)
{
    using namespace HPack;

    frameWriter.start(FrameType::HEADERS, FrameFlag::PRIORITY | FrameFlag::END_HEADERS,
                      stream.streamID);

    if (!stream.data()) {
        frameWriter.addFlag(FrameFlag::END_STREAM);
        stream.state = Stream::halfClosedLocal;
    } else {
        stream.state = Stream::open;
    }

    frameWriter.append(quint32()); // No stream dependency in Qt.
    frameWriter.append(stream.weight());

    bool useProxy = false;
#ifndef QT_NO_NETWORKPROXY
    useProxy = m_connection->d_func()->networkProxy.type() != QNetworkProxy::NoProxy;
#endif
    if (stream.request().withCredentials()) {
        m_connection->d_func()->createAuthorization(m_socket, stream.request());
        stream.request().d->needResendWithCredentials = false;
    }
    const auto headers = build_headers(stream.request(), maxHeaderListSize, useProxy);
    if (!headers.size()) // nothing fits into maxHeaderListSize
        return false;

    // Compress in-place:
    BitOStream outputStream(frameWriter.outboundFrame().buffer);
    if (!encoder.encodeRequest(outputStream, headers))
        return false;

    return frameWriter.writeHEADERS(*m_socket, maxFrameSize);
}

bool QHttp2ProtocolHandler::sendDATA(Stream &stream)
{
    Q_ASSERT(maxFrameSize > frameHeaderSize);
    Q_ASSERT(m_socket);
    Q_ASSERT(stream.data());

    const auto &request = stream.request();
    auto reply = stream.reply();
    Q_ASSERT(reply);
    const auto replyPrivate = reply->d_func();
    Q_ASSERT(replyPrivate);

    auto slot = std::min<qint32>(sessionSendWindowSize, stream.sendWindow);
    while (replyPrivate->totallyUploadedData < request.contentLength() && slot) {
        qint64 chunkSize = 0;
        const uchar *src =
            reinterpret_cast<const uchar *>(stream.data()->readPointer(slot, chunkSize));

        if (chunkSize == -1)
            return false;

        if (!src || !chunkSize) {
            // Stream is not suspended by the flow control,
            // we do not have data ready yet.
            return true;
        }

        frameWriter.start(FrameType::DATA, FrameFlag::EMPTY, stream.streamID);
        const qint32 bytesWritten = qint32(std::min<qint64>(slot, chunkSize));

        if (!frameWriter.writeDATA(*m_socket, maxFrameSize, src, bytesWritten))
            return false;

        stream.data()->advanceReadPointer(bytesWritten);
        stream.sendWindow -= bytesWritten;
        sessionSendWindowSize -= bytesWritten;
        replyPrivate->totallyUploadedData += bytesWritten;
        emit reply->dataSendProgress(replyPrivate->totallyUploadedData,
                                     request.contentLength());
        slot = std::min(sessionSendWindowSize, stream.sendWindow);
    }

    if (replyPrivate->totallyUploadedData == request.contentLength()) {
        frameWriter.start(FrameType::DATA, FrameFlag::END_STREAM, stream.streamID);
        frameWriter.setPayloadSize(0);
        frameWriter.write(*m_socket);
        stream.state = Stream::halfClosedLocal;
        stream.data()->disconnect(this);
        removeFromSuspended(stream.streamID);
    } else if (!stream.data()->atEnd()) {
        addToSuspended(stream);
    }

    return true;
}

bool QHttp2ProtocolHandler::sendWINDOW_UPDATE(quint32 streamID, quint32 delta)
{
    Q_ASSERT(m_socket);

    frameWriter.start(FrameType::WINDOW_UPDATE, FrameFlag::EMPTY, streamID);
    frameWriter.append(delta);
    return frameWriter.write(*m_socket);
}

bool QHttp2ProtocolHandler::sendRST_STREAM(quint32 streamID, quint32 errorCode)
{
    Q_ASSERT(m_socket);

    frameWriter.start(FrameType::RST_STREAM, FrameFlag::EMPTY, streamID);
    frameWriter.append(errorCode);
    return frameWriter.write(*m_socket);
}

bool QHttp2ProtocolHandler::sendGOAWAY(quint32 errorCode)
{
    Q_ASSERT(m_socket);

    frameWriter.start(FrameType::GOAWAY, FrameFlag::EMPTY, connectionStreamID);
    frameWriter.append(quint32(connectionStreamID));
    frameWriter.append(errorCode);
    return frameWriter.write(*m_socket);
}

void QHttp2ProtocolHandler::handleDATA()
{
    Q_ASSERT(inboundFrame.type() == FrameType::DATA);

    const auto streamID = inboundFrame.streamID();
    if (streamID == connectionStreamID)
        return connectionError(PROTOCOL_ERROR, "DATA on stream 0x0");

    if (!activeStreams.contains(streamID) && !streamWasReset(streamID))
        return connectionError(ENHANCE_YOUR_CALM, "DATA on invalid stream");

    if (qint32(inboundFrame.payloadSize()) > sessionReceiveWindowSize)
        return connectionError(FLOW_CONTROL_ERROR, "Flow control error");

    sessionReceiveWindowSize -= inboundFrame.payloadSize();

    auto it = activeStreams.find(streamID);
    if (it != activeStreams.end()) {
        Stream &stream = it.value();

        if (qint32(inboundFrame.payloadSize()) > stream.recvWindow) {
            finishStreamWithError(stream, QNetworkReply::ProtocolFailure, "flow control error"_L1);
            sendRST_STREAM(streamID, FLOW_CONTROL_ERROR);
            markAsReset(streamID);
            deleteActiveStream(streamID);
        } else {
            stream.recvWindow -= inboundFrame.payloadSize();
            // Uncompress data if needed and append it ...
            updateStream(stream, inboundFrame);

            if (inboundFrame.flags().testFlag(FrameFlag::END_STREAM)) {
                finishStream(stream);
                deleteActiveStream(stream.streamID);
            } else if (stream.recvWindow < streamInitialReceiveWindowSize / 2) {
                QMetaObject::invokeMethod(this, "sendWINDOW_UPDATE", Qt::QueuedConnection,
                                          Q_ARG(quint32, stream.streamID),
                                          Q_ARG(quint32, streamInitialReceiveWindowSize - stream.recvWindow));
                stream.recvWindow = streamInitialReceiveWindowSize;
            }
        }
    }

    if (sessionReceiveWindowSize < maxSessionReceiveWindowSize / 2) {
        QMetaObject::invokeMethod(this, "sendWINDOW_UPDATE", Qt::QueuedConnection,
                                  Q_ARG(quint32, connectionStreamID),
                                  Q_ARG(quint32, maxSessionReceiveWindowSize - sessionReceiveWindowSize));
        sessionReceiveWindowSize = maxSessionReceiveWindowSize;
    }
}

void QHttp2ProtocolHandler::handleHEADERS()
{
    Q_ASSERT(inboundFrame.type() == FrameType::HEADERS);

    const auto streamID = inboundFrame.streamID();
    if (streamID == connectionStreamID)
        return connectionError(PROTOCOL_ERROR, "HEADERS on 0x0 stream");

    if (!activeStreams.contains(streamID) && !streamWasReset(streamID))
        return connectionError(ENHANCE_YOUR_CALM, "HEADERS on invalid stream");

    const auto flags = inboundFrame.flags();
    if (flags.testFlag(FrameFlag::PRIORITY)) {
        handlePRIORITY();
        if (goingAway)
            return;
    }

    const bool endHeaders = flags.testFlag(FrameFlag::END_HEADERS);
    continuedFrames.clear();
    continuedFrames.push_back(std::move(inboundFrame));
    if (!endHeaders) {
        continuationExpected = true;
        return;
    }

    handleContinuedHEADERS();
}

void QHttp2ProtocolHandler::handlePRIORITY()
{
    Q_ASSERT(inboundFrame.type() == FrameType::PRIORITY ||
             inboundFrame.type() == FrameType::HEADERS);

    const auto streamID = inboundFrame.streamID();
    if (streamID == connectionStreamID)
        return connectionError(PROTOCOL_ERROR, "PIRORITY on 0x0 stream");

    if (!activeStreams.contains(streamID) && !streamWasReset(streamID))
        return connectionError(ENHANCE_YOUR_CALM, "PRIORITY on invalid stream");

    quint32 streamDependency = 0;
    uchar weight = 0;
    const bool noErr = inboundFrame.priority(&streamDependency, &weight);
    Q_UNUSED(noErr);
    Q_ASSERT(noErr);


    const bool exclusive = streamDependency & 0x80000000;
    streamDependency &= ~0x80000000;

    // Ignore this for now ...
    // Can be used for streams (re)prioritization - 5.3
    Q_UNUSED(exclusive);
    Q_UNUSED(weight);
}

void QHttp2ProtocolHandler::handleRST_STREAM()
{
    Q_ASSERT(inboundFrame.type() == FrameType::RST_STREAM);

    // "RST_STREAM frames MUST be associated with a stream.
    // If a RST_STREAM frame is received with a stream identifier of 0x0,
    // the recipient MUST treat this as a connection error (Section 5.4.1)
    // of type PROTOCOL_ERROR.
    const auto streamID = inboundFrame.streamID();
    if (streamID == connectionStreamID)
        return connectionError(PROTOCOL_ERROR, "RST_STREAM on 0x0");

    if (!(streamID & 0x1)) {
        // RST_STREAM on a promised stream:
        // since we do not keep track of such streams,
        // just ignore.
        return;
    }

    if (streamID >= nextID) {
        // "RST_STREAM frames MUST NOT be sent for a stream
        // in the "idle" state. .. the recipient MUST treat this
        // as a connection error (Section 5.4.1) of type PROTOCOL_ERROR."
        return connectionError(PROTOCOL_ERROR, "RST_STREAM on idle stream");
    }

    if (!activeStreams.contains(streamID)) {
        // 'closed' stream, ignore.
        return;
    }

    Q_ASSERT(inboundFrame.dataSize() == 4);

    Stream &stream = activeStreams[streamID];
    finishStreamWithError(stream, qFromBigEndian<quint32>(inboundFrame.dataBegin()));
    markAsReset(stream.streamID);
    deleteActiveStream(stream.streamID);
}

void QHttp2ProtocolHandler::handleSETTINGS()
{
    // 6.5 SETTINGS.
    Q_ASSERT(inboundFrame.type() == FrameType::SETTINGS);

    if (inboundFrame.streamID() != connectionStreamID)
        return connectionError(PROTOCOL_ERROR, "SETTINGS on invalid stream");

    if (inboundFrame.flags().testFlag(FrameFlag::ACK)) {
        if (!waitingForSettingsACK)
            return connectionError(PROTOCOL_ERROR, "unexpected SETTINGS ACK");
        waitingForSettingsACK = false;
        return;
    }

    if (inboundFrame.dataSize()) {
        auto src = inboundFrame.dataBegin();
        for (const uchar *end = src + inboundFrame.dataSize(); src != end; src += 6) {
            const Settings identifier = Settings(qFromBigEndian<quint16>(src));
            const quint32 intVal = qFromBigEndian<quint32>(src + 2);
            if (!acceptSetting(identifier, intVal)) {
                // If not accepted - we finish with connectionError.
                return;
            }
        }
    }

    sendSETTINGS_ACK();
}


void QHttp2ProtocolHandler::handlePUSH_PROMISE()
{
    // 6.6 PUSH_PROMISE.
    Q_ASSERT(inboundFrame.type() == FrameType::PUSH_PROMISE);

    if (!pushPromiseEnabled && prefaceSent && !waitingForSettingsACK) {
        // This means, server ACKed our 'NO PUSH',
        // but sent us PUSH_PROMISE anyway.
        return connectionError(PROTOCOL_ERROR, "unexpected PUSH_PROMISE frame");
    }

    const auto streamID = inboundFrame.streamID();
    if (streamID == connectionStreamID) {
        return connectionError(PROTOCOL_ERROR,
                               "PUSH_PROMISE with invalid associated stream (0x0)");
    }

    if (!activeStreams.contains(streamID) && !streamWasReset(streamID)) {
        return connectionError(ENHANCE_YOUR_CALM,
                               "PUSH_PROMISE with invalid associated stream");
    }

    const auto reservedID = qFromBigEndian<quint32>(inboundFrame.dataBegin());
    if ((reservedID & 1) || reservedID <= lastPromisedID ||
        reservedID > Http2::lastValidStreamID) {
        return connectionError(PROTOCOL_ERROR,
                               "PUSH_PROMISE with invalid promised stream ID");
    }

    lastPromisedID = reservedID;

    if (!pushPromiseEnabled) {
        // "ignoring a PUSH_PROMISE frame causes the stream state to become
        // indeterminate" - let's send RST_STREAM frame with REFUSE_STREAM code.
        resetPromisedStream(inboundFrame, Http2::REFUSE_STREAM);
    }

    const bool endHeaders = inboundFrame.flags().testFlag(FrameFlag::END_HEADERS);
    continuedFrames.clear();
    continuedFrames.push_back(std::move(inboundFrame));

    if (!endHeaders) {
        continuationExpected = true;
        return;
    }

    handleContinuedHEADERS();
}

void QHttp2ProtocolHandler::handlePING()
{
    // Since we're implementing a client and not
    // a server, we only reply to a PING, ACKing it.
    Q_ASSERT(inboundFrame.type() == FrameType::PING);
    Q_ASSERT(m_socket);

    if (inboundFrame.streamID() != connectionStreamID)
        return connectionError(PROTOCOL_ERROR, "PING on invalid stream");

    if (inboundFrame.flags() & FrameFlag::ACK)
        return connectionError(PROTOCOL_ERROR, "unexpected PING ACK");

    Q_ASSERT(inboundFrame.dataSize() == 8);

    frameWriter.start(FrameType::PING, FrameFlag::ACK, connectionStreamID);
    frameWriter.append(inboundFrame.dataBegin(), inboundFrame.dataBegin() + 8);
    frameWriter.write(*m_socket);
}

void QHttp2ProtocolHandler::handleGOAWAY()
{
    // 6.8 GOAWAY

    Q_ASSERT(inboundFrame.type() == FrameType::GOAWAY);
    // "An endpoint MUST treat a GOAWAY frame with a stream identifier
    // other than 0x0 as a connection error (Section 5.4.1) of type PROTOCOL_ERROR."
    if (inboundFrame.streamID() != connectionStreamID)
        return connectionError(PROTOCOL_ERROR, "GOAWAY on invalid stream");

    const auto src = inboundFrame.dataBegin();
    quint32 lastStreamID = qFromBigEndian<quint32>(src);
    const quint32 errorCode = qFromBigEndian<quint32>(src + 4);

    if (!lastStreamID) {
        // "The last stream identifier can be set to 0 if no
        // streams were processed."
        lastStreamID = 1;
    } else if (!(lastStreamID & 0x1)) {
        // 5.1.1 - we (client) use only odd numbers as stream identifiers.
        return connectionError(PROTOCOL_ERROR, "GOAWAY with invalid last stream ID");
    } else if (lastStreamID >= nextID) {
        // "A server that is attempting to gracefully shut down a connection SHOULD
        // send an initial GOAWAY frame with the last stream identifier set to 2^31-1
        // and a NO_ERROR code."
        if (lastStreamID != Http2::lastValidStreamID || errorCode != HTTP2_NO_ERROR)
            return connectionError(PROTOCOL_ERROR, "GOAWAY invalid stream/error code");
    } else {
        lastStreamID += 2;
    }

    goingAway = true;

    // For the requests (and streams) we did not start yet, we have to report an
    // error.
    m_channel->emitFinishedWithError(QNetworkReply::ProtocolUnknownError,
                                     "GOAWAY received, cannot start a request");
    // Also, prevent further calls to sendRequest:
    m_channel->h2RequestsToSend.clear();

    QNetworkReply::NetworkError error = QNetworkReply::NoError;
    QString message;
    qt_error(errorCode, error, message);

    // Even if the GOAWAY frame contains NO_ERROR we must send an error
    // when terminating streams to ensure users can distinguish from a
    // successful completion.
    if (errorCode == HTTP2_NO_ERROR) {
        error = QNetworkReply::ContentReSendError;
        message = "Server stopped accepting new streams before this stream was established"_L1;
    }

    for (quint32 id = lastStreamID; id < nextID; id += 2) {
        const auto it = activeStreams.find(id);
        if (it != activeStreams.end()) {
            Stream &stream = *it;
            finishStreamWithError(stream, error, message);
            markAsReset(id);
            deleteActiveStream(id);
        } else {
            removeFromSuspended(id);
        }
    }

    if (!activeStreams.size())
        closeSession();
}

void QHttp2ProtocolHandler::handleWINDOW_UPDATE()
{
    Q_ASSERT(inboundFrame.type() == FrameType::WINDOW_UPDATE);


    const quint32 delta = qFromBigEndian<quint32>(inboundFrame.dataBegin());
    const bool valid = delta && delta <= quint32(std::numeric_limits<qint32>::max());
    const auto streamID = inboundFrame.streamID();

    if (streamID == Http2::connectionStreamID) {
        qint32 sum = 0;
        if (!valid || qAddOverflow(sessionSendWindowSize, qint32(delta), &sum))
            return connectionError(PROTOCOL_ERROR, "WINDOW_UPDATE invalid delta");
        sessionSendWindowSize = sum;
    } else {
        auto it = activeStreams.find(streamID);
        if (it == activeStreams.end()) {
            // WINDOW_UPDATE on closed streams can be ignored.
            return;
        }
        Stream &stream = it.value();
        qint32 sum = 0;
        if (!valid || qAddOverflow(stream.sendWindow, qint32(delta), &sum)) {
            finishStreamWithError(stream, QNetworkReply::ProtocolFailure,
                                  "invalid WINDOW_UPDATE delta"_L1);
            sendRST_STREAM(streamID, PROTOCOL_ERROR);
            markAsReset(streamID);
            deleteActiveStream(streamID);
            return;
        }
        stream.sendWindow = sum;
    }

    // Since we're in _q_receiveReply at the moment, let's first handle other
    // frames and resume suspended streams (if any) == start sending our own frame
    // after handling these frames, since one them can be e.g. GOAWAY.
    QMetaObject::invokeMethod(this, "resumeSuspendedStreams", Qt::QueuedConnection);
}

void QHttp2ProtocolHandler::handleCONTINUATION()
{
    Q_ASSERT(inboundFrame.type() == FrameType::CONTINUATION);
    Q_ASSERT(continuedFrames.size()); // HEADERS frame must be already in.

    if (inboundFrame.streamID() != continuedFrames.front().streamID())
        return connectionError(PROTOCOL_ERROR, "CONTINUATION on invalid stream");

    const bool endHeaders = inboundFrame.flags().testFlag(FrameFlag::END_HEADERS);
    continuedFrames.push_back(std::move(inboundFrame));

    if (!endHeaders)
        return;

    continuationExpected = false;
    handleContinuedHEADERS();
}

void QHttp2ProtocolHandler::handleContinuedHEADERS()
{
    // 'Continued' HEADERS can be: the initial HEADERS/PUSH_PROMISE frame
    // with/without END_HEADERS flag set plus, if no END_HEADERS flag,
    // a sequence of one or more CONTINUATION frames.
    Q_ASSERT(continuedFrames.size());
    const auto firstFrameType = continuedFrames[0].type();
    Q_ASSERT(firstFrameType == FrameType::HEADERS ||
             firstFrameType == FrameType::PUSH_PROMISE);

    const auto streamID = continuedFrames[0].streamID();

    const auto streamIt = activeStreams.find(streamID);
    if (firstFrameType == FrameType::HEADERS) {
        if (streamIt != activeStreams.end()) {
            Stream &stream = streamIt.value();
            if (stream.state != Stream::halfClosedLocal
                && stream.state != Stream::remoteReserved
                && stream.state != Stream::open) {
                // We can receive HEADERS on streams initiated by our requests
                // (these streams are in halfClosedLocal or open state) or
                // remote-reserved streams from a server's PUSH_PROMISE.
                finishStreamWithError(stream, QNetworkReply::ProtocolFailure,
                                      "HEADERS on invalid stream"_L1);
                sendRST_STREAM(streamID, CANCEL);
                markAsReset(streamID);
                deleteActiveStream(streamID);
                return;
            }
        } else if (!streamWasReset(streamID)) {
            return connectionError(PROTOCOL_ERROR, "HEADERS on invalid stream");
        }
        // Else: we cannot just ignore our peer's HEADERS frames - they change
        // HPACK context - even though the stream was reset; apparently the peer
        // has yet to see the reset.
    }

    std::vector<uchar> hpackBlock(Http2::assemble_hpack_block(continuedFrames));
    const bool hasHeaderFields = !hpackBlock.empty();
    if (hasHeaderFields) {
        HPack::BitIStream inputStream{&hpackBlock[0], &hpackBlock[0] + hpackBlock.size()};
        if (!decoder.decodeHeaderFields(inputStream))
            return connectionError(COMPRESSION_ERROR, "HPACK decompression failed");
    } else if (firstFrameType == FrameType::PUSH_PROMISE) {
        // It could be a PRIORITY sent in HEADERS - already handled by this
        // point in handleHEADERS. If it was PUSH_PROMISE (HTTP/2 8.2.1):
        // "The header fields in PUSH_PROMISE and any subsequent CONTINUATION
        // frames MUST be a valid and complete set of request header fields
        // (Section 8.1.2.3) ... If a client receives a PUSH_PROMISE that does
        // not include a complete and valid set of header fields or the :method
        // pseudo-header field identifies a method that is not safe, it MUST
        // respond with a stream error (Section 5.4.2) of type PROTOCOL_ERROR."
        resetPromisedStream(continuedFrames[0], Http2::PROTOCOL_ERROR);
        return;
    }

    switch (firstFrameType) {
    case FrameType::HEADERS:
        if (streamIt != activeStreams.end()) {
            Stream &stream = streamIt.value();
            if (hasHeaderFields)
                updateStream(stream, decoder.decodedHeader());
            // Needs to resend the request; we should finish and delete the current stream
            const bool needResend = stream.request().d->needResendWithCredentials;
            // No DATA frames. Or needs to resend.
            if (continuedFrames[0].flags() & FrameFlag::END_STREAM || needResend) {
                finishStream(stream);
                deleteActiveStream(stream.streamID);
            }
        }
        break;
    case FrameType::PUSH_PROMISE:
        if (!tryReserveStream(continuedFrames[0], decoder.decodedHeader()))
            resetPromisedStream(continuedFrames[0], Http2::PROTOCOL_ERROR);
        break;
    default:
        break;
    }
}

bool QHttp2ProtocolHandler::acceptSetting(Http2::Settings identifier, quint32 newValue)
{
    if (identifier == Settings::HEADER_TABLE_SIZE_ID) {
        if (newValue > maxAcceptableTableSize) {
            connectionError(PROTOCOL_ERROR, "SETTINGS invalid table size");
            return false;
        }
        encoder.setMaxDynamicTableSize(newValue);
    }

    if (identifier == Settings::INITIAL_WINDOW_SIZE_ID) {
        // For every active stream - adjust its window
        // (and handle possible overflows as errors).
        if (newValue > quint32(std::numeric_limits<qint32>::max())) {
            connectionError(FLOW_CONTROL_ERROR, "SETTINGS invalid initial window size");
            return false;
        }

        const qint32 delta = qint32(newValue) - streamInitialSendWindowSize;
        streamInitialSendWindowSize = newValue;

        std::vector<quint32> brokenStreams;
        brokenStreams.reserve(activeStreams.size());
        for (auto &stream : activeStreams) {
            qint32 sum = 0;
            if (qAddOverflow(stream.sendWindow, delta, &sum)) {
                brokenStreams.push_back(stream.streamID);
                continue;
            }
            stream.sendWindow = sum;
        }

        for (auto id : brokenStreams) {
            auto &stream = activeStreams[id];
            finishStreamWithError(stream, QNetworkReply::ProtocolFailure,
                                  "SETTINGS window overflow"_L1);
            sendRST_STREAM(id, PROTOCOL_ERROR);
            markAsReset(id);
            deleteActiveStream(id);
        }

        QMetaObject::invokeMethod(this, "resumeSuspendedStreams", Qt::QueuedConnection);
    }

    if (identifier == Settings::MAX_CONCURRENT_STREAMS_ID)
        maxConcurrentStreams = newValue;

    if (identifier == Settings::MAX_FRAME_SIZE_ID) {
        if (newValue < Http2::minPayloadLimit || newValue > Http2::maxPayloadSize) {
            connectionError(PROTOCOL_ERROR, "SETTINGS max frame size is out of range");
            return false;
        }
        maxFrameSize = newValue;
    }

    if (identifier == Settings::MAX_HEADER_LIST_SIZE_ID) {
        // We just remember this value, it can later
        // prevent us from sending any request (and this
        // will end up in request/reply error).
        maxHeaderListSize = newValue;
    }

    return true;
}

void QHttp2ProtocolHandler::updateStream(Stream &stream, const HPack::HttpHeader &headers,
                                         Qt::ConnectionType connectionType)
{
    const auto httpReply = stream.reply();
    auto &httpRequest = stream.request();
    Q_ASSERT(httpReply || stream.state == Stream::remoteReserved);

    if (!httpReply) {
        // It's a PUSH_PROMISEd HEADERS, no actual request/reply
        // exists yet, we have to cache this data for a future
        // (potential) request.

        // TODO: the part with assignment is not especially cool
        // or beautiful, good that at least QByteArray is implicitly
        // sharing data. To be refactored (std::move).
        Q_ASSERT(promisedData.contains(stream.key));
        PushPromise &promise = promisedData[stream.key];
        promise.responseHeader = headers;
        return;
    }

    const auto httpReplyPrivate = httpReply->d_func();

    // For HTTP/1 'location' is handled (and redirect URL set) when a protocol
    // handler emits channel->allDone(). Http/2 protocol handler never emits
    // allDone, since we have many requests multiplexed in one channel at any
    // moment and we are probably not done yet. So we extract url and set it
    // here, if needed.
    int statusCode = 0;
    for (const auto &pair : headers) {
        const auto &name = pair.name;
        const auto value = QByteArrayView(pair.value);

        // TODO: part of this code copies what SPDY protocol handler does when
        // processing headers. Binary nature of HTTP/2 and SPDY saves us a lot
        // of parsing and related errors/bugs, but it would be nice to have
        // more detailed validation of headers.
        if (name == ":status") {
            statusCode = value.left(3).toInt();
            httpReply->setStatusCode(statusCode);
            m_channel->lastStatus = statusCode; // Mostly useless for http/2, needed for auth
            httpReply->setReasonPhrase(QString::fromLatin1(value.mid(4)));
        } else if (name == ":version") {
            httpReply->setMajorVersion(value.at(5) - '0');
            httpReply->setMinorVersion(value.at(7) - '0');
        } else if (name == "content-length") {
            bool ok = false;
            const qlonglong length = value.toLongLong(&ok);
            if (ok)
                httpReply->setContentLength(length);
        } else {
            const auto binder = name == "set-cookie" ? QByteArrayView("\n") : QByteArrayView(", ");
            httpReply->appendHeaderField(name, QByteArray(pair.value).replace('\0', binder));
        }
    }

    // Discard all informational (1xx) replies with the exception of 101.
    // Also see RFC 9110 (Chapter 15.2)
    if (statusCode == 100 || (102 <= statusCode && statusCode <= 199)) {
        httpReplyPrivate->clearHttpLayerInformation();
        return;
    }

    if (QHttpNetworkReply::isHttpRedirect(statusCode) && httpRequest.isFollowRedirects()) {
        QHttpNetworkConnectionPrivate::ParseRedirectResult result =
                m_connection->d_func()->parseRedirectResponse(httpReply);
        if (result.errorCode != QNetworkReply::NoError) {
            auto errorString = m_connection->d_func()->errorDetail(result.errorCode, m_socket);
            finishStreamWithError(stream, result.errorCode, errorString);
            sendRST_STREAM(stream.streamID, INTERNAL_ERROR);
            markAsReset(stream.streamID);
            return;
        }

        if (result.redirectUrl.isValid())
            httpReply->setRedirectUrl(result.redirectUrl);
    }

    if (httpReplyPrivate->isCompressed() && httpRequest.d->autoDecompress)
        httpReplyPrivate->removeAutoDecompressHeader();

    if (QHttpNetworkReply::isHttpRedirect(statusCode)) {
        // Note: This status code can trigger uploadByteDevice->reset() in
        // QHttpNetworkConnectionChannel::handleStatus. Alas, we have no single
        // request/reply, we multiplex several requests and thus we never simply
        // call 'handleStatus'. If we have a byte-device - we try to reset it
        // here, we don't (and can't) handle any error during reset operation.
        if (stream.data()) {
            stream.data()->reset();
            httpReplyPrivate->totallyUploadedData = 0;
        }
    }

    if (connectionType == Qt::DirectConnection)
        emit httpReply->headerChanged();
    else
        QMetaObject::invokeMethod(httpReply, "headerChanged", connectionType);
}

void QHttp2ProtocolHandler::updateStream(Stream &stream, const Frame &frame,
                                         Qt::ConnectionType connectionType)
{
    Q_ASSERT(frame.type() == FrameType::DATA);
    auto httpReply = stream.reply();
    Q_ASSERT(httpReply || stream.state == Stream::remoteReserved);

    if (!httpReply) {
        Q_ASSERT(promisedData.contains(stream.key));
        PushPromise &promise = promisedData[stream.key];
        // TODO: refactor this to use std::move.
        promise.dataFrames.push_back(frame);
        return;
    }

    if (const auto length = frame.dataSize()) {
        const char *data = reinterpret_cast<const char *>(frame.dataBegin());
        auto replyPrivate = httpReply->d_func();

        replyPrivate->totalProgress += length;

        replyPrivate->responseData.append(QByteArray(data, length));

        if (replyPrivate->shouldEmitSignals()) {
            if (connectionType == Qt::DirectConnection) {
                emit httpReply->readyRead();
                emit httpReply->dataReadProgress(replyPrivate->totalProgress,
                                                 replyPrivate->bodyLength);
            } else {
                QMetaObject::invokeMethod(httpReply, "readyRead", connectionType);
                QMetaObject::invokeMethod(httpReply, "dataReadProgress", connectionType,
                                          Q_ARG(qint64, replyPrivate->totalProgress),
                                          Q_ARG(qint64, replyPrivate->bodyLength));
            }
        }
    }
}

// After calling this function, either the request will be re-sent or
// the reply will be finishedWithError! Do not emit finished() or similar on the
// reply after this!
void QHttp2ProtocolHandler::handleAuthorization(Stream &stream)
{
    auto *httpReply = stream.reply();
    auto *httpReplyPrivate = httpReply->d_func();
    auto &httpRequest = stream.request();

    Q_ASSERT(httpReply && (httpReply->statusCode() == 401 || httpReply->statusCode() == 407));

    const auto handleAuth = [&, this](QByteArrayView authField, bool isProxy) -> bool {
        Q_ASSERT(httpReply);
        const QByteArrayView auth = authField.trimmed();
        if (auth.startsWith("Negotiate") || auth.startsWith("NTLM")) {
            // @todo: We're supposed to fall back to http/1.1:
            // https://docs.microsoft.com/en-us/iis/get-started/whats-new-in-iis-10/http2-on-iis#when-is-http2-not-supported
            // "Windows authentication (NTLM/Kerberos/Negotiate) is not supported with HTTP/2.
            // In this case IIS will fall back to HTTP/1.1."
            // Though it might be OK to ignore this. The server shouldn't let us connect with
            // HTTP/2 if it doesn't support us using it.
            return false;
        }
        // Somewhat mimics parts of QHttpNetworkConnectionChannel::handleStatus
        bool resend = false;
        const bool authenticateHandled = m_connection->d_func()->handleAuthenticateChallenge(
                m_socket, httpReply, isProxy, resend);
        if (authenticateHandled) {
            if (resend) {
                httpReply->d_func()->eraseData();
                // Add the request back in queue, we'll retry later now that
                // we've gotten some username/password set on it:
                httpRequest.d->needResendWithCredentials = true;
                m_channel->h2RequestsToSend.insert(httpRequest.priority(), stream.httpPair);
                httpReply->d_func()->clearHeaders();
                // If we have data we were uploading we need to reset it:
                if (stream.data()) {
                    stream.data()->reset();
                    httpReplyPrivate->totallyUploadedData = 0;
                }
                // We automatically try to send new requests when the stream is
                // closed, so we don't need to call sendRequest ourselves.
                return true;
            } // else: we're just not resending the request.
            // @note In the http/1.x case we (at time of writing) call close()
            // for the connectionChannel (which is a bit weird, we could surely
            // reuse the open socket outside "connection:close"?), but in http2
            // we only have one channel, so we won't close anything.
        } else {
            // No authentication header or authentication isn't supported, but
            // we got a 401/407 so we cannot succeed. We need to emit signals
            // for headers and data, and then finishWithError.
            emit httpReply->headerChanged();
            emit httpReply->readyRead();
            QNetworkReply::NetworkError error = httpReply->statusCode() == 401
                    ? QNetworkReply::AuthenticationRequiredError
                    : QNetworkReply::ProxyAuthenticationRequiredError;
            finishStreamWithError(stream, QNetworkReply::AuthenticationRequiredError,
                                  m_connection->d_func()->errorDetail(error, m_socket));
        }
        return false;
    };

    // These statuses would in HTTP/1.1 be handled by
    // QHttpNetworkConnectionChannel::handleStatus. But because h2 has
    // multiple streams/requests in a single channel this structure does not
    // map properly to that function.
    bool authOk = true;
    switch (httpReply->statusCode()) {
    case 401:
        authOk = handleAuth(httpReply->headerField("www-authenticate"), false);
        break;
    case 407:
        authOk = handleAuth(httpReply->headerField("proxy-authenticate"), true);
        break;
    default:
        Q_UNREACHABLE();
    }
    if (authOk) {
        markAsReset(stream.streamID);
        deleteActiveStream(stream.streamID);
    } // else: errors handled inside handleAuth
}

// Called when we have received a frame with the END_STREAM flag set
void QHttp2ProtocolHandler::finishStream(Stream &stream, Qt::ConnectionType connectionType)
{
    Q_ASSERT(stream.state == Stream::remoteReserved || stream.reply());

    stream.state = Stream::closed;
    auto httpReply = stream.reply();
    if (httpReply) {
        int statusCode = httpReply->statusCode();
        if (statusCode == 401 || statusCode == 407) {
            // handleAuthorization will either re-send the request or
            // finishWithError. In either case we don't want to emit finished
            // here.
            handleAuthorization(stream);
            return;
        }

        httpReply->disconnect(this);
        if (stream.data())
            stream.data()->disconnect(this);

        if (!stream.request().d->needResendWithCredentials) {
            if (connectionType == Qt::DirectConnection)
                emit httpReply->finished();
            else
                QMetaObject::invokeMethod(httpReply, "finished", connectionType);
        }
    }

    qCDebug(QT_HTTP2) << "stream" << stream.streamID << "closed";
}

void QHttp2ProtocolHandler::finishStreamWithError(Stream &stream, quint32 errorCode)
{
    QNetworkReply::NetworkError error = QNetworkReply::NoError;
    QString message;
    qt_error(errorCode, error, message);
    finishStreamWithError(stream, error, message);
}

void QHttp2ProtocolHandler::finishStreamWithError(Stream &stream, QNetworkReply::NetworkError error,
                                                  const QString &message)
{
    Q_ASSERT(stream.state == Stream::remoteReserved || stream.reply());

    stream.state = Stream::closed;
    if (auto httpReply = stream.reply()) {
        httpReply->disconnect(this);
        if (stream.data())
            stream.data()->disconnect(this);

        // TODO: error message must be translated!!! (tr)
        emit httpReply->finishedWithError(error, message);
    }

    qCWarning(QT_HTTP2) << "stream" << stream.streamID
                        << "finished with error:" << message;
}

quint32 QHttp2ProtocolHandler::createNewStream(const HttpMessagePair &message, bool uploadDone)
{
    const qint32 newStreamID = allocateStreamID();
    if (!newStreamID)
        return 0;

    Q_ASSERT(!activeStreams.contains(newStreamID));

    const auto reply = message.second;
    const auto replyPrivate = reply->d_func();
    replyPrivate->connection = m_connection;
    replyPrivate->connectionChannel = m_channel;
    reply->setHttp2WasUsed(true);
    streamIDs.insert(reply, newStreamID);
    connect(reply, SIGNAL(destroyed(QObject*)),
            this, SLOT(_q_replyDestroyed(QObject*)));

    const Stream newStream(message, newStreamID,
                           streamInitialSendWindowSize,
                           streamInitialReceiveWindowSize);

    if (!uploadDone) {
        if (auto src = newStream.data()) {
            connect(src, SIGNAL(readyRead()), this,
                    SLOT(_q_uploadDataReadyRead()), Qt::QueuedConnection);
            connect(src, &QHttp2ProtocolHandler::destroyed,
                    this, &QHttp2ProtocolHandler::_q_uploadDataDestroyed);
            streamIDs.insert(src, newStreamID);
        }
    }

    QMetaObject::invokeMethod(reply, "requestSent", Qt::QueuedConnection);

    activeStreams.insert(newStreamID, newStream);

    return newStreamID;
}

void QHttp2ProtocolHandler::addToSuspended(Stream &stream)
{
    qCDebug(QT_HTTP2) << "stream" << stream.streamID
                      << "suspended by flow control";
    const auto priority = stream.priority();
    Q_ASSERT(int(priority) >= 0 && int(priority) < 3);
    suspendedStreams[priority].push_back(stream.streamID);
}

void QHttp2ProtocolHandler::markAsReset(quint32 streamID)
{
    Q_ASSERT(streamID);

    qCDebug(QT_HTTP2) << "stream" << streamID << "was reset";
    // This part is quite tricky: I have to clear this set
    // so that it does not become tOOO big.
    if (recycledStreams.size() > maxRecycledStreams) {
        // At least, I'm erasing the oldest first ...
        recycledStreams.erase(recycledStreams.begin(),
                              recycledStreams.begin() +
                              recycledStreams.size() / 2);
    }

    const auto it = std::lower_bound(recycledStreams.begin(), recycledStreams.end(),
                                     streamID);
    if (it != recycledStreams.end() && *it == streamID)
        return;

    recycledStreams.insert(it, streamID);
}

quint32 QHttp2ProtocolHandler::popStreamToResume()
{
    quint32 streamID = connectionStreamID;
    using QNR = QHttpNetworkRequest;
    const QNR::Priority ranks[] = {QNR::HighPriority,
                                   QNR::NormalPriority,
                                   QNR::LowPriority};

    for (const QNR::Priority rank : ranks) {
        auto &queue = suspendedStreams[rank];
        auto it = queue.begin();
        for (; it != queue.end(); ++it) {
            auto stream = activeStreams.constFind(*it);
            if (stream == activeStreams.cend())
                continue;
            if (stream->sendWindow > 0)
                break;
        }

        if (it != queue.end()) {
            streamID = *it;
            queue.erase(it);
            break;
        }
    }

    return streamID;
}

void QHttp2ProtocolHandler::removeFromSuspended(quint32 streamID)
{
    for (auto &q : suspendedStreams) {
        q.erase(std::remove(q.begin(), q.end(), streamID), q.end());
    }
}

void QHttp2ProtocolHandler::deleteActiveStream(quint32 streamID)
{
    if (const auto it = activeStreams.constFind(streamID); it != activeStreams.cend()) {
        const Stream &stream = it.value();
        if (stream.reply()) {
            stream.reply()->disconnect(this);
            streamIDs.remove(stream.reply());
        }
        if (stream.data()) {
            stream.data()->disconnect(this);
            streamIDs.remove(stream.data());
        }
        activeStreams.erase(it);
    }

    removeFromSuspended(streamID);
    if (m_channel->h2RequestsToSend.size())
        QMetaObject::invokeMethod(this, "sendRequest", Qt::QueuedConnection);
}

bool QHttp2ProtocolHandler::streamWasReset(quint32 streamID) const
{
    const auto it = std::lower_bound(recycledStreams.begin(),
                                     recycledStreams.end(),
                                     streamID);
    return it != recycledStreams.end() && *it == streamID;
}

void QHttp2ProtocolHandler::resumeSuspendedStreams()
{
    while (sessionSendWindowSize > 0) {
        const auto streamID = popStreamToResume();
        if (!streamID)
            return;

        auto it = activeStreams.find(streamID);
        if (it == activeStreams.end())
            continue;
        Stream &stream = it.value();

        if (!sendDATA(stream)) {
            finishStreamWithError(stream, QNetworkReply::UnknownNetworkError,
                                  "failed to send DATA"_L1);
            sendRST_STREAM(streamID, INTERNAL_ERROR);
            markAsReset(streamID);
            deleteActiveStream(streamID);
        }
    }
}

quint32 QHttp2ProtocolHandler::allocateStreamID()
{
    // With protocol upgrade streamID == 1 will become
    // invalid. The logic must be updated.
    if (nextID > Http2::lastValidStreamID)
        return 0;

    const quint32 streamID = nextID;
    nextID += 2;

    return streamID;
}

bool QHttp2ProtocolHandler::tryReserveStream(const Http2::Frame &pushPromiseFrame,
                                             const HPack::HttpHeader &requestHeader)
{
    Q_ASSERT(pushPromiseFrame.type() == FrameType::PUSH_PROMISE);

    const auto url = HPack::makePromiseKeyUrl(requestHeader);
    if (!url.has_value())
        return false;

    Q_ASSERT(activeStreams.contains(pushPromiseFrame.streamID()));
    const Stream &associatedStream = activeStreams[pushPromiseFrame.streamID()];

    const auto associatedUrl = urlkey_from_request(associatedStream.request());
    if (url->adjusted(QUrl::RemovePath) != associatedUrl.adjusted(QUrl::RemovePath))
        return false;

    const auto urlKey = url->toString();
    if (promisedData.contains(urlKey)) // duplicate push promise
        return false;

    const auto reservedID = qFromBigEndian<quint32>(pushPromiseFrame.dataBegin());
    // By this time all sanity checks on reservedID were done already
    // in handlePUSH_PROMISE. We do not repeat them, only those below:
    Q_ASSERT(!activeStreams.contains(reservedID));
    Q_ASSERT(!streamWasReset(reservedID));

    auto &promise = promisedData[urlKey];
    promise.reservedID = reservedID;
    promise.pushHeader = requestHeader;

    activeStreams.insert(reservedID, Stream(urlKey, reservedID, streamInitialReceiveWindowSize));
    return true;
}

void QHttp2ProtocolHandler::resetPromisedStream(const Frame &pushPromiseFrame,
                                                Http2::Http2Error reason)
{
    Q_ASSERT(pushPromiseFrame.type() == FrameType::PUSH_PROMISE);
    const auto reservedID = qFromBigEndian<quint32>(pushPromiseFrame.dataBegin());
    sendRST_STREAM(reservedID, reason);
    markAsReset(reservedID);
}

void QHttp2ProtocolHandler::initReplyFromPushPromise(const HttpMessagePair &message,
                                                     const QString &cacheKey)
{
    Q_ASSERT(promisedData.contains(cacheKey));
    auto promise = promisedData.take(cacheKey);
    Q_ASSERT(message.second);
    message.second->setHttp2WasUsed(true);

    qCDebug(QT_HTTP2) << "found cached/promised response on stream" << promise.reservedID;

    bool replyFinished = false;
    Stream *promisedStream = nullptr;
    if (auto it = activeStreams.find(promise.reservedID); it != activeStreams.end()) {
        promisedStream = &it.value();
        // Ok, we have an active (not closed yet) stream waiting for more frames,
        // let's pretend we requested it:
        promisedStream->httpPair = message;
    } else {
        // Let's pretent we're sending a request now:
        Stream closedStream(message, promise.reservedID,
                            streamInitialSendWindowSize,
                            streamInitialReceiveWindowSize);
        closedStream.state = Stream::halfClosedLocal;
        it = activeStreams.insert(promise.reservedID, closedStream);
        promisedStream = &it.value();
        replyFinished = true;
    }

    Q_ASSERT(promisedStream);

    if (!promise.responseHeader.empty())
        updateStream(*promisedStream, promise.responseHeader, Qt::QueuedConnection);

    for (const auto &frame : promise.dataFrames)
        updateStream(*promisedStream, frame, Qt::QueuedConnection);

    if (replyFinished) {
        // Good, we already have received ALL the frames of that PUSH_PROMISE,
        // nothing more to do.
        finishStream(*promisedStream, Qt::QueuedConnection);
        deleteActiveStream(promisedStream->streamID);
    }
}

void QHttp2ProtocolHandler::connectionError(Http2::Http2Error errorCode,
                                            const char *message)
{
    Q_ASSERT(message);
    Q_ASSERT(!goingAway);

    qCCritical(QT_HTTP2) << "connection error:" << message;

    goingAway = true;
    sendGOAWAY(errorCode);
    const auto error = qt_error(errorCode);
    m_channel->emitFinishedWithError(error, message);

    for (auto &stream: activeStreams)
        finishStreamWithError(stream, error, QLatin1StringView(message));

    closeSession();
}

void QHttp2ProtocolHandler::closeSession()
{
    activeStreams.clear();
    for (auto &q: suspendedStreams)
        q.clear();
    recycledStreams.clear();

    m_channel->close();
}

QT_END_NAMESPACE

#include "moc_qhttp2protocolhandler_p.cpp"