/*
 * Bittorrent Client using Qt and libtorrent.
 * Copyright (C) 2014  Vladimir Golovnev <glassez@yandex.ru>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * In addition, as a special exception, the copyright holders give permission to
 * link this program with the OpenSSL project's "OpenSSL" library (or with
 * modified versions of it that use the same license as the "OpenSSL" library),
 * and distribute the linked executables. You must obey the GNU General Public
 * License in all respects for all of the code used other than "OpenSSL".  If you
 * modify file(s), you may extend this exception to your version of the file(s),
 * but you are not obligated to do so. If you do not wish to do so, delete this
 * exception statement from your version.
 */

#include "webapplication.h"

#include <algorithm>
#include <functional>
#include <queue>
#include <stdexcept>
#include <vector>

#include <QDateTime>
#include <QDebug>
#include <QFile>
#include <QFileInfo>
#include <QJsonDocument>
#include <QMimeDatabase>
#include <QMimeType>
#include <QRegExp>
#include <QUrl>

#include "base/global.h"
#include "base/http/httperror.h"
#include "base/iconprovider.h"
#include "base/logger.h"
#include "base/preferences.h"
#include "base/utils/bytearray.h"
#include "base/utils/fs.h"
#include "base/utils/misc.h"
#include "base/utils/random.h"
#include "base/utils/string.h"
#include "api/apierror.h"
#include "api/appcontroller.h"
#include "api/authcontroller.h"
#include "api/logcontroller.h"
#include "api/rsscontroller.h"
#include "api/searchcontroller.h"
#include "api/synccontroller.h"
#include "api/torrentscontroller.h"
#include "api/transfercontroller.h"

constexpr int MAX_ALLOWED_FILESIZE = 10 * 1024 * 1024;

const QString PATH_PREFIX_IMAGES {QStringLiteral("/images/")};
const QString WWW_FOLDER {QStringLiteral(":/www")};
const QString PUBLIC_FOLDER {QStringLiteral("/public")};
const QString PRIVATE_FOLDER {QStringLiteral("/private")};

namespace
{
    QStringMap parseCookie(const QString &cookieStr)
    {
        // [rfc6265] 4.2.1. Syntax
        QStringMap ret;
        const QVector<QStringRef> cookies = cookieStr.splitRef(';', QString::SkipEmptyParts);

        for (const auto &cookie : cookies) {
            const int idx = cookie.indexOf('=');
            if (idx < 0)
                continue;

            const QString name = cookie.left(idx).trimmed().toString();
            const QString value = Utils::String::unquote(cookie.mid(idx + 1).trimmed()).toString();
            ret.insert(name, value);
        }
        return ret;
    }

    inline QUrl urlFromHostHeader(const QString &hostHeader)
    {
        if (!hostHeader.contains(QLatin1String("://")))
            return QUrl(QLatin1String("http://") + hostHeader);
        return hostHeader;
    }

    QString getCachingInterval(QString contentType)
    {
        contentType = contentType.toLower();

        if (contentType.startsWith(QLatin1String("image/")))
            return QLatin1String("private, max-age=604800");  // 1 week

        if ((contentType == Http::CONTENT_TYPE_CSS)
            || (contentType == Http::CONTENT_TYPE_JS)) {
            // short interval in case of program update
            return QLatin1String("private, max-age=43200");  // 12 hrs
        }

        return QLatin1String("no-store");
    }
}

WebApplication::WebApplication(QObject *parent)
    : QObject(parent)
{
    registerAPIController(QLatin1String("app"), new AppController(this, this));
    registerAPIController(QLatin1String("auth"), new AuthController(this, this));
    registerAPIController(QLatin1String("log"), new LogController(this, this));
    registerAPIController(QLatin1String("rss"), new RSSController(this, this));
    registerAPIController(QLatin1String("search"), new SearchController(this, this));
    registerAPIController(QLatin1String("sync"), new SyncController(this, this));
    registerAPIController(QLatin1String("torrents"), new TorrentsController(this, this));
    registerAPIController(QLatin1String("transfer"), new TransferController(this, this));

    declarePublicAPI(QLatin1String("auth/login"));

    configure();
    connect(Preferences::instance(), &Preferences::changed, this, &WebApplication::configure);
}

WebApplication::~WebApplication()
{
    // cleanup sessions data
    qDeleteAll(m_sessions);
}

void WebApplication::sendWebUIFile()
{
    const QStringList pathItems {request().path.split('/', QString::SkipEmptyParts)};
    if (pathItems.contains(".") || pathItems.contains(".."))
        throw InternalServerErrorHTTPError();

    if (!m_isAltUIUsed) {
        if (request().path.startsWith(PATH_PREFIX_IMAGES)) {
            const QString imageFilename {request().path.mid(PATH_PREFIX_IMAGES.size())};
            sendFile(QLatin1String(":/icons/") + imageFilename);
            return;
        }
    }

    const QString path {
        (request().path != QLatin1String("/")
                ? request().path
                : (session()
                   ? QLatin1String("/index.html")
                   : QLatin1String("/login.html")))
    };

    QString localPath {
        m_rootFolder
                + (session() ? PRIVATE_FOLDER : PUBLIC_FOLDER)
                + path
    };

    QFileInfo fileInfo {localPath};

    if (!fileInfo.exists() && session()) {
        // try to send public file if there is no private one
        localPath = m_rootFolder + PUBLIC_FOLDER + path;
        fileInfo.setFile(localPath);
    }

    if (m_isAltUIUsed) {
#ifdef Q_OS_UNIX
        if (!Utils::Fs::isRegularFile(localPath)) {
            status(500, "Internal Server Error");
            print(tr("Unacceptable file type, only regular file is allowed."), Http::CONTENT_TYPE_TXT);
            return;
        }
#endif

        while (fileInfo.filePath() != m_rootFolder) {
            if (fileInfo.isSymLink())
                throw InternalServerErrorHTTPError(tr("Symlinks inside alternative UI folder are forbidden."));

            fileInfo.setFile(fileInfo.path());
        }
    }

    sendFile(localPath);
}

void WebApplication::translateDocument(QString &data)
{
    const QRegularExpression regex("QBT_TR\\((([^\\)]|\\)(?!QBT_TR))+)\\)QBT_TR\\[CONTEXT=([a-zA-Z_][a-zA-Z0-9_]*)\\]");

    const bool isTranslationNeeded = !m_currentLocale.startsWith("en")
            || m_currentLocale.startsWith("en_AU") || m_currentLocale.startsWith("en_GB")
            || !m_translator.isEmpty();

    int i = 0;
    bool found = true;
    while (i < data.size() && found) {
        QRegularExpressionMatch regexMatch;
        i = data.indexOf(regex, i, &regexMatch);
        if (i >= 0) {
            const QString sourceText = regexMatch.captured(1);
            const QString context = regexMatch.captured(3);

            QString translation = sourceText;
            if (isTranslationNeeded) {
                const QString loadedText = m_translator.translate(context.toUtf8().constData(), sourceText.toUtf8().constData(), nullptr, 1);
                if (!loadedText.isEmpty())
                    translation = loadedText;
            }

            // Use HTML code for quotes to prevent issues with JS
            translation.replace('\'', "&#39;");
            translation.replace('\"', "&#34;");

            data.replace(i, regexMatch.capturedLength(), translation);
            i += translation.length();
        }
        else {
            found = false; // no more translatable strings
        }

        data.replace(QLatin1String("${LANG}"), m_currentLocale.left(2));
        data.replace(QLatin1String("${VERSION}"), QBT_VERSION);
    }
}

WebSession *WebApplication::session()
{
    return m_currentSession;
}

const Http::Request &WebApplication::request() const
{
    return m_request;
}

const Http::Environment &WebApplication::env() const
{
    return m_env;
}

void WebApplication::doProcessRequest()
{
    QString scope, action;

    const auto findAPICall = [&]() -> bool
    {
        QRegularExpressionMatch match = m_apiPathPattern.match(request().path);
        if (!match.hasMatch()) return false;

        action = match.captured(QLatin1String("action"));
        scope = match.captured(QLatin1String("scope"));
        return true;
    };

    const auto findLegacyAPICall = [&]() -> bool
    {
        QRegularExpressionMatch match = m_apiLegacyPathPattern.match(request().path);
        if (!match.hasMatch()) return false;

        struct APICompatInfo
        {
            QString scope;
            QString action;
            std::function<void ()> convertFunc;
        };
        const QMap<QString, APICompatInfo> APICompatMapping {
            {"sync/maindata", {"sync", "maindata", nullptr}},
            {"sync/torrent_peers", {"sync", "torrentPeers", nullptr}},

            {"login", {"auth", "login", nullptr}},
            {"logout", {"auth", "logout", nullptr}},

            {"command/shutdown", {"app", "shutdown", nullptr}},
            {"query/preferences", {"app", "preferences", nullptr}},
            {"command/setPreferences", {"app", "setPreferences", nullptr}},
            {"command/getSavePath", {"app", "defaultSavePath", nullptr}},

            {"query/getLog", {"log", "main", nullptr}},
            {"query/getPeerLog", {"log", "peers", nullptr}},

            {"query/torrents", {"torrents", "info", nullptr}},
            {"query/propertiesGeneral", {"torrents", "properties", nullptr}},
            {"query/propertiesTrackers", {"torrents", "trackers", nullptr}},
            {"query/propertiesWebSeeds", {"torrents", "webseeds", nullptr}},
            {"query/propertiesFiles", {"torrents", "files", nullptr}},
            {"query/getPieceHashes", {"torrents", "pieceHashes", nullptr}},
            {"query/getPieceStates", {"torrents", "pieceStates", nullptr}},
            {"command/resume", {"torrents", "resume", [this]() { m_params["hashes"] = m_params.take("hash"); }}},
            {"command/pause", {"torrents", "pause", [this]() { m_params["hashes"] = m_params.take("hash"); }}},
            {"command/recheck", {"torrents", "recheck", [this]() { m_params["hashes"] = m_params.take("hash"); }}},
            {"command/resumeAll", {"torrents", "resume", [this]() { m_params["hashes"] = "all"; }}},
            {"command/pauseAll", {"torrents", "pause", [this]() { m_params["hashes"] = "all"; }}},
            {"command/rename", {"torrents", "rename", nullptr}},
            {"command/download", {"torrents", "add", nullptr}},
            {"command/upload", {"torrents", "add", nullptr}},
            {"command/delete", {"torrents", "delete", [this]() { m_params["deleteFiles"] = "false"; }}},
            {"command/deletePerm", {"torrents", "delete", [this]() { m_params["deleteFiles"] = "true"; }}},
            {"command/addTrackers", {"torrents", "addTrackers", nullptr}},
            {"command/setFilePrio", {"torrents", "filePrio", nullptr}},
            {"command/setCategory", {"torrents", "setCategory", nullptr}},
            {"command/addCategory", {"torrents", "createCategory", nullptr}},
            {"command/removeCategories", {"torrents", "removeCategories", nullptr}},
            {"command/getTorrentsUpLimit", {"torrents", "uploadLimit", nullptr}},
            {"command/getTorrentsDlLimit", {"torrents", "downloadLimit", nullptr}},
            {"command/setTorrentsUpLimit", {"torrents", "setUploadLimit", nullptr}},
            {"command/setTorrentsDlLimit", {"torrents", "setDownloadLimit", nullptr}},
            {"command/increasePrio", {"torrents", "increasePrio", nullptr}},
            {"command/decreasePrio", {"torrents", "decreasePrio", nullptr}},
            {"command/topPrio", {"torrents", "topPrio", nullptr}},
            {"command/bottomPrio", {"torrents", "bottomPrio", nullptr}},
            {"command/setLocation", {"torrents", "setLocation", nullptr}},
            {"command/setAutoTMM", {"torrents", "setAutoManagement", nullptr}},
            {"command/setSuperSeeding", {"torrents", "setSuperSeeding", nullptr}},
            {"command/setForceStart", {"torrents", "setForceStart", nullptr}},
            {"command/toggleSequentialDownload", {"torrents", "toggleSequentialDownload", nullptr}},
            {"command/toggleFirstLastPiecePrio", {"torrents", "toggleFirstLastPiecePrio", nullptr}},

            {"query/transferInfo", {"transfer", "info", nullptr}},
            {"command/alternativeSpeedLimitsEnabled", {"transfer", "speedLimitsMode", nullptr}},
            {"command/toggleAlternativeSpeedLimits", {"transfer", "toggleSpeedLimitsMode", nullptr}},
            {"command/getGlobalUpLimit", {"transfer", "uploadLimit", nullptr}},
            {"command/getGlobalDlLimit", {"transfer", "downloadLimit", nullptr}},
            {"command/setGlobalUpLimit", {"transfer", "setUploadLimit", nullptr}},
            {"command/setGlobalDlLimit", {"transfer", "setDownloadLimit", nullptr}}
        };

        const QString legacyAction {match.captured(QLatin1String("action"))};
        const APICompatInfo compatInfo = APICompatMapping.value(legacyAction);

        scope = compatInfo.scope;
        action = compatInfo.action;
        if (compatInfo.convertFunc)
            compatInfo.convertFunc();

        const QString hash {match.captured(QLatin1String("hash"))};
        if (!hash.isEmpty())
            m_params[QLatin1String("hash")] = hash;

        return true;
    };

    if (!findAPICall())
        findLegacyAPICall();

    APIController *controller = m_apiControllers.value(scope);
    if (!controller) {
        if (request().path == QLatin1String("/version/api")) {
            print(QString::number(COMPAT_API_VERSION), Http::CONTENT_TYPE_TXT);
            return;
        }

        if (request().path == QLatin1String("/version/api_min")) {
            print(QString::number(COMPAT_API_VERSION_MIN), Http::CONTENT_TYPE_TXT);
            return;
        }

        if (request().path == QLatin1String("/version/qbittorrent")) {
            print(QString(QBT_VERSION), Http::CONTENT_TYPE_TXT);
            return;
        }

        sendWebUIFile();
    }
    else {
        if (!session() && !isPublicAPI(scope, action))
            throw ForbiddenHTTPError();

        DataMap data;
        for (const Http::UploadedFile &torrent : request().files)
            data[torrent.filename] = torrent.data;

        try {
            const QVariant result = controller->run(action, m_params, data);
            switch (result.userType()) {
            case QMetaType::QString:
                print(result.toString(), Http::CONTENT_TYPE_TXT);
                break;
            case QMetaType::QJsonDocument:
                print(result.toJsonDocument().toJson(QJsonDocument::Compact), Http::CONTENT_TYPE_JSON);
                break;
            default:
                print(result.toString(), Http::CONTENT_TYPE_TXT);
                break;
            }
        }
        catch (const APIError &error) {
            // re-throw as HTTPError
            switch (error.type()) {
            case APIErrorType::AccessDenied:
                throw ForbiddenHTTPError(error.message());
            case APIErrorType::BadData:
                throw UnsupportedMediaTypeHTTPError(error.message());
            case APIErrorType::BadParams:
                throw BadRequestHTTPError(error.message());
            case APIErrorType::Conflict:
                throw ConflictHTTPError(error.message());
            case APIErrorType::NotFound:
                throw NotFoundHTTPError(error.message());
            default:
                Q_ASSERT(false);
            }
        }
    }
}

void WebApplication::configure()
{
    const auto *pref = Preferences::instance();

    const bool isAltUIUsed = pref->isAltWebUiEnabled();
    const QString rootFolder = Utils::Fs::expandPathAbs(
                !isAltUIUsed ? WWW_FOLDER : pref->getWebUiRootFolder());
    if ((isAltUIUsed != m_isAltUIUsed) || (rootFolder != m_rootFolder)) {
        m_isAltUIUsed = isAltUIUsed;
        m_rootFolder = rootFolder;
        m_translatedFiles.clear();
        if (!m_isAltUIUsed)
            LogMsg(tr("Using built-in Web UI."));
        else
            LogMsg(tr("Using custom Web UI. Location: \"%1\".").arg(m_rootFolder));
    }

    const QString newLocale = pref->getLocale();
    if (m_currentLocale != newLocale) {
        m_currentLocale = newLocale;
        m_translatedFiles.clear();
        if (m_translator.load(m_rootFolder + QLatin1String("/translations/webui_") + m_currentLocale)) {
            LogMsg(tr("Web UI translation for selected locale (%1) is successfully loaded.")
                   .arg(m_currentLocale));
        }
        else {
            LogMsg(tr("Couldn't load Web UI translation for selected locale (%1). Falling back to default (en).")
                   .arg(m_currentLocale), Log::WARNING);
        }
    }

    m_isLocalAuthEnabled = pref->isWebUiLocalAuthEnabled();
    m_isAuthSubnetWhitelistEnabled = pref->isWebUiAuthSubnetWhitelistEnabled();
    m_authSubnetWhitelist = pref->getWebUiAuthSubnetWhitelist();

    m_domainList = pref->getServerDomains().split(';', QString::SkipEmptyParts);
    std::for_each(m_domainList.begin(), m_domainList.end(), [](QString &entry) { entry = entry.trimmed(); });

    m_isClickjackingProtectionEnabled = pref->isWebUiClickjackingProtectionEnabled();
    m_isCSRFProtectionEnabled = pref->isWebUiCSRFProtectionEnabled();
    m_isHostHeaderValidationEnabled = pref->isWebUIHostHeaderValidationEnabled();
    m_isHttpsEnabled = pref->isWebUiHttpsEnabled();
}

void WebApplication::registerAPIController(const QString &scope, APIController *controller)
{
    Q_ASSERT(controller);
    Q_ASSERT(!m_apiControllers.value(scope));

    m_apiControllers[scope] = controller;
}

void WebApplication::declarePublicAPI(const QString &apiPath)
{
    m_publicAPIs << apiPath;
}

void WebApplication::sendFile(const QString &path)
{
    const QDateTime lastModified {QFileInfo(path).lastModified()};

    // find translated file in cache
    auto it = m_translatedFiles.constFind(path);
    if ((it != m_translatedFiles.constEnd()) && (lastModified <= (*it).lastModified)) {
        const QString mimeName {QMimeDatabase().mimeTypeForFileNameAndData(path, (*it).data).name()};
        print((*it).data, mimeName);
        header(Http::HEADER_CACHE_CONTROL, getCachingInterval(mimeName));
        return;
    }

    QFile file {path};
    if (!file.open(QIODevice::ReadOnly)) {
        qDebug("File %s was not found!", qUtf8Printable(path));
        throw NotFoundHTTPError();
    }

    if (file.size() > MAX_ALLOWED_FILESIZE) {
        qWarning("%s: exceeded the maximum allowed file size!", qUtf8Printable(path));
        throw InternalServerErrorHTTPError(tr("Exceeded the maximum allowed file size (%1)!")
                                           .arg(Utils::Misc::friendlyUnit(MAX_ALLOWED_FILESIZE)));
    }

    QByteArray data {file.readAll()};
    file.close();

    const QMimeType mimeType {QMimeDatabase().mimeTypeForFileNameAndData(path, data)};
    const bool isTranslatable {mimeType.inherits(QLatin1String("text/plain"))};

    // Translate the file
    if (isTranslatable) {
        QString dataStr {data};
        translateDocument(dataStr);
        data = dataStr.toUtf8();

        m_translatedFiles[path] = {data, lastModified}; // caching translated file
    }

    print(data, mimeType.name());
    header(Http::HEADER_CACHE_CONTROL, getCachingInterval(mimeType.name()));
}

Http::Response WebApplication::processRequest(const Http::Request &request, const Http::Environment &env)
{
    m_currentSession = nullptr;
    m_request = request;
    m_env = env;
    m_params.clear();
    if (m_request.method == Http::METHOD_GET) {
        // Parse GET parameters
        using namespace Utils::ByteArray;
        for (const QByteArray &param : copyAsConst(splitToViews(m_request.query, "&"))) {
            const int sepPos = param.indexOf('=');
            if (sepPos <= 0) continue; // ignores params without name

            const QString paramName {QString::fromUtf8(param.constData(), sepPos)};
            const int valuePos = sepPos + 1;
            const QString paramValue {
                QString::fromUtf8(param.constData() + valuePos, param.size() - valuePos)};
            m_params[paramName] = paramValue;
        }
    }
    else {
        m_params = m_request.posts;
    }

    // clear response
    clear();

    try {
        // block suspicious requests
        if ((m_isCSRFProtectionEnabled && isCrossSiteRequest(m_request))
            || (m_isHostHeaderValidationEnabled && !validateHostHeader(m_domainList))) {
            throw UnauthorizedHTTPError();
        }

        sessionInitialize();
        doProcessRequest();
    }
    catch (const HTTPError &error) {
        status(error.statusCode(), error.statusText());
        if (!error.message().isEmpty())
            print(error.message(), Http::CONTENT_TYPE_TXT);
    }

    header(Http::HEADER_X_XSS_PROTECTION, "1; mode=block");
    header(Http::HEADER_X_CONTENT_TYPE_OPTIONS, "nosniff");

    QString csp = QLatin1String("default-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; script-src 'self' 'unsafe-inline'; object-src 'none'; form-action 'self';");
    if (m_isClickjackingProtectionEnabled) {
        header(Http::HEADER_X_FRAME_OPTIONS, "SAMEORIGIN");
        csp += QLatin1String(" frame-ancestors 'self';");
    }
    if (m_isHttpsEnabled) {
        csp += QLatin1String(" upgrade-insecure-requests;");
    }

    header(Http::HEADER_CONTENT_SECURITY_POLICY, csp);

    return response();
}

QString WebApplication::clientId() const
{
    return env().clientAddress.toString();
}

void WebApplication::sessionInitialize()
{
    Q_ASSERT(!m_currentSession);

    const QString sessionId {parseCookie(m_request.headers.value(QLatin1String("cookie"))).value(C_SID)};

    // TODO: Additional session check

    if (!sessionId.isEmpty()) {
        m_currentSession = m_sessions.value(sessionId);
        if (m_currentSession) {
            const qint64 now = QDateTime::currentMSecsSinceEpoch() / 1000;
            if ((now - m_currentSession->m_timestamp) > INACTIVE_TIME) {
                // session is outdated - removing it
                delete m_sessions.take(sessionId);
                m_currentSession = nullptr;
            }
            else {
                m_currentSession->updateTimestamp();
            }
        }
        else {
            qDebug() << Q_FUNC_INFO << "session does not exist!";
        }
    }

    if (!m_currentSession && !isAuthNeeded())
        sessionStart();
}

QString WebApplication::generateSid() const
{
    QString sid;

    do {
        const size_t size = 6;
        quint32 tmp[size];

        for (size_t i = 0; i < size; ++i)
            tmp[i] = Utils::Random::rand();

        sid = QByteArray::fromRawData(reinterpret_cast<const char *>(tmp), sizeof(quint32) * size).toBase64();
    }
    while (m_sessions.contains(sid));

    return sid;
}

bool WebApplication::isAuthNeeded()
{
    if (!m_isLocalAuthEnabled && Utils::Net::isLoopbackAddress(m_env.clientAddress))
        return false;
    if (m_isAuthSubnetWhitelistEnabled && Utils::Net::isIPInRange(m_env.clientAddress, m_authSubnetWhitelist))
        return false;
    return true;
}

bool WebApplication::isPublicAPI(const QString &scope, const QString &action) const
{
    return m_publicAPIs.contains(QString::fromLatin1("%1/%2").arg(scope, action));
}

void WebApplication::sessionStart()
{
    Q_ASSERT(!m_currentSession);

    // remove outdated sessions
    const qint64 now = QDateTime::currentMSecsSinceEpoch() / 1000;
    foreach (const auto session, m_sessions) {
        if ((now - session->timestamp()) > INACTIVE_TIME)
            delete m_sessions.take(session->id());
    }

    m_currentSession = new WebSession(generateSid());
    m_sessions[m_currentSession->id()] = m_currentSession;

    QNetworkCookie cookie(C_SID, m_currentSession->id().toUtf8());
    cookie.setHttpOnly(true);
    cookie.setPath(QLatin1String("/"));
    QByteArray cookieRawForm = cookie.toRawForm();
    if (m_isCSRFProtectionEnabled)
        cookieRawForm.append("; SameSite=Strict");
    header(Http::HEADER_SET_COOKIE, cookieRawForm);
}

void WebApplication::sessionEnd()
{
    Q_ASSERT(m_currentSession);

    QNetworkCookie cookie(C_SID);
    cookie.setPath(QLatin1String("/"));
    cookie.setExpirationDate(QDateTime::currentDateTime().addDays(-1));

    delete m_sessions.take(m_currentSession->id());
    m_currentSession = nullptr;

    header(Http::HEADER_SET_COOKIE, cookie.toRawForm());
}

bool WebApplication::isCrossSiteRequest(const Http::Request &request) const
{
    // https://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF)_Prevention_Cheat_Sheet#Verifying_Same_Origin_with_Standard_Headers

    const auto isSameOrigin = [](const QUrl &left, const QUrl &right) -> bool
    {
        // [rfc6454] 5. Comparing Origins
        return ((left.port() == right.port())
                // && (left.scheme() == right.scheme())  // not present in this context
                && (left.host() == right.host()));
    };

    const QString targetOrigin = request.headers.value(Http::HEADER_X_FORWARDED_HOST, request.headers.value(Http::HEADER_HOST));
    const QString originValue = request.headers.value(Http::HEADER_ORIGIN);
    const QString refererValue = request.headers.value(Http::HEADER_REFERER);

    if (originValue.isEmpty() && refererValue.isEmpty()) {
        // owasp.org recommends to block this request, but doing so will inevitably lead Web API users to spoof headers
        // so lets be permissive here
        return false;
    }

    // sent with CORS requests, as well as with POST requests
    if (!originValue.isEmpty()) {
        const bool isInvalid = !isSameOrigin(urlFromHostHeader(targetOrigin), originValue);
        if (isInvalid)
            LogMsg(tr("WebUI: Origin header & Target origin mismatch! Source IP: '%1'. Origin header: '%2'. Target origin: '%3'")
                   .arg(m_env.clientAddress.toString(), originValue, targetOrigin)
                   , Log::WARNING);
        return isInvalid;
    }

    if (!refererValue.isEmpty()) {
        const bool isInvalid = !isSameOrigin(urlFromHostHeader(targetOrigin), refererValue);
        if (isInvalid)
            LogMsg(tr("WebUI: Referer header & Target origin mismatch! Source IP: '%1'. Referer header: '%2'. Target origin: '%3'")
                   .arg(m_env.clientAddress.toString(), refererValue, targetOrigin)
                   , Log::WARNING);
        return isInvalid;
    }

    return true;
}

bool WebApplication::validateHostHeader(const QStringList &domains) const
{
    const QUrl hostHeader = urlFromHostHeader(m_request.headers[Http::HEADER_HOST]);
    const QString requestHost = hostHeader.host();

    // (if present) try matching host header's port with local port
    const int requestPort = hostHeader.port();
    if ((requestPort != -1) && (m_env.localPort != requestPort)) {
        LogMsg(tr("WebUI: Invalid Host header, port mismatch. Request source IP: '%1'. Server port: '%2'. Received Host header: '%3'")
               .arg(m_env.clientAddress.toString()).arg(m_env.localPort)
               .arg(m_request.headers[Http::HEADER_HOST])
                , Log::WARNING);
        return false;
    }

    // try matching host header with local address
#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
    const bool sameAddr = m_env.localAddress.isEqual(QHostAddress(requestHost));
#else
    const auto equal = [](const Q_IPV6ADDR &l, const Q_IPV6ADDR &r) -> bool
    {
        for (int i = 0; i < 16; ++i) {
            if (l[i] != r[i])
                return false;
        }
        return true;
    };
    const bool sameAddr = equal(m_env.localAddress.toIPv6Address(), QHostAddress(requestHost).toIPv6Address());
#endif

    if (sameAddr)
        return true;

    // try matching host header with domain list
    for (const auto &domain : domains) {
        QRegExp domainRegex(domain, Qt::CaseInsensitive, QRegExp::Wildcard);
        if (requestHost.contains(domainRegex))
            return true;
    }

    LogMsg(tr("WebUI: Invalid Host header. Request source IP: '%1'. Received Host header: '%2'")
           .arg(m_env.clientAddress.toString(), m_request.headers[Http::HEADER_HOST])
            , Log::WARNING);
    return false;
}

// WebSession

WebSession::WebSession(const QString &sid)
    : m_sid {sid}
{
    updateTimestamp();
}

QString WebSession::id() const
{
    return m_sid;
}

qint64 WebSession::timestamp() const
{
    return m_timestamp;
}

QVariant WebSession::getData(const QString &id) const
{
    return m_data.value(id);
}

void WebSession::setData(const QString &id, const QVariant &data)
{
    m_data[id] = data;
}

void WebSession::updateTimestamp()
{
    m_timestamp = QDateTime::currentMSecsSinceEpoch() / 1000;
}