/*
    This file is part of the KDE libraries
    SPDX-FileCopyrightText: 2020 Henri Chain <henri.chain@enioka.com>

    SPDX-License-Identifier: LGPL-2.0-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
*/

#include "kiogui_debug.h"
#include "systemdprocessrunner_p.h"

#include "managerinterface.h"
#include "propertiesinterface.h"
#include "unitinterface.h"

#include <QTimer>

#include <algorithm>
#include <mutex>
#include <signal.h>

using namespace org::freedesktop;
using namespace Qt::Literals::StringLiterals;

KProcessRunner::LaunchMode calculateLaunchMode()
{
    // overrides for unit test purposes. These are considered internal, private and may change in the future.
    if (Q_UNLIKELY(qEnvironmentVariableIntValue("_KDE_APPLICATIONS_AS_SERVICE"))) {
        return KProcessRunner::SystemdAsService;
    }
    if (Q_UNLIKELY(qEnvironmentVariableIntValue("_KDE_APPLICATIONS_AS_SCOPE"))) {
        return KProcessRunner::SystemdAsScope;
    }
    if (Q_UNLIKELY(qEnvironmentVariableIntValue("_KDE_APPLICATIONS_AS_FORKING"))) {
        return KProcessRunner::Forking;
    }

    QDBusConnection bus = QDBusConnection::sessionBus();
    auto queryVersionMessage = QDBusMessage::createMethodCall(systemdService, systemdPath, u"org.freedesktop.DBus.Properties"_s, u"Get"_s);
    queryVersionMessage << u"org.freedesktop.systemd1.Manager"_s << u"Version"_s;
    QDBusReply<QDBusVariant> reply = bus.call(queryVersionMessage);
    QVersionNumber systemdVersion = QVersionNumber::fromString(reply.value().variant().toString());
    if (systemdVersion.isNull()) {
        qCWarning(KIO_GUI) << "Failed to determine systemd version, falling back to extremely legacy forking mode.";
        return KProcessRunner::Forking;
    }
    if (systemdVersion.majorVersion() < 250) { // first version with ExitType=cgroup, which won't cleanup when the first process exits
        return KProcessRunner::SystemdAsScope;
    }
    return KProcessRunner::SystemdAsService;
}

KProcessRunner::LaunchMode SystemdProcessRunner::modeAvailable()
{
    static std::once_flag launchModeCalculated;
    static KProcessRunner::LaunchMode launchMode = Forking;
    std::call_once(launchModeCalculated, [] {
        launchMode = calculateLaunchMode();
        qCDebug(KIO_GUI) << "Launching processes via" << launchMode;
        qDBusRegisterMetaType<QVariantMultiItem>();
        qDBusRegisterMetaType<QVariantMultiMap>();
        qDBusRegisterMetaType<TransientAux>();
        qDBusRegisterMetaType<TransientAuxList>();
        qDBusRegisterMetaType<ExecCommand>();
        qDBusRegisterMetaType<ExecCommandList>();
    });
    return launchMode;
}

SystemdProcessRunner::SystemdProcessRunner()
    : KProcessRunner()
{
}

bool SystemdProcessRunner::waitForStarted(int timeout)
{
    if (m_pid || m_exited) {
        return true;
    }
    QEventLoop loop;
    bool success = false;
    loop.connect(this, &KProcessRunner::processStarted, this, [&loop, &success]() {
        loop.quit();
        success = true;
    });
    QTimer::singleShot(timeout, &loop, &QEventLoop::quit);
    QObject::connect(this, &KProcessRunner::error, &loop, &QEventLoop::quit);
    loop.exec();
    return success;
}

static QStringList prepareEnvironment(const QProcessEnvironment &environment)
{
    QProcessEnvironment allowedEnvironment = environment.inheritsFromParent() ? QProcessEnvironment::systemEnvironment() : environment;
    auto allowedBySystemd = [](const QChar c) {
        return c.isDigit() || c.isLetter() || c == u'_';
    };
    for (const auto variables = allowedEnvironment.keys(); const auto &variable : variables) {
        if (!std::ranges::all_of(variable, allowedBySystemd)) {
            qCWarning(KIO_GUI) << "Not passing environment variable" << variable << "to systemd because its name contains illegal characters";
            allowedEnvironment.remove(variable);
        }
    }
    return allowedEnvironment.toStringList();
}

// systemd performs substitution of $ variables, we don't want this
// $ should be replaced with $$
static QStringList escapeArguments(const QStringList &in)
{
    QStringList escaped = in;
    std::transform(escaped.begin(), escaped.end(), escaped.begin(), [](QString &item) {
        return item.replace(QLatin1Char('$'), QLatin1String("$$"));
    });
    return escaped;
}

void SystemdProcessRunner::startProcess()
{
    // As specified in "XDG standardization for applications" in https://systemd.io/DESKTOP_ENVIRONMENTS/
    m_serviceName = QStringLiteral("app-%1@%2.service").arg(escapeUnitName(resolveServiceAlias()), QUuid::createUuid().toString(QUuid::Id128));

    // Watch for new services
    m_manager = new systemd1::Manager(systemdService, systemdPath, QDBusConnection::sessionBus(), this);
    m_manager->Subscribe();
    connect(m_manager, &systemd1::Manager::UnitNew, this, &SystemdProcessRunner::handleUnitNew);

    // Watch for service creation job error
    connect(m_manager,
            &systemd1::Manager::JobRemoved,
            this,
            [this](uint jobId, const QDBusObjectPath &jobPath, const QString &unitName, const QString &result) {
                Q_UNUSED(jobId)
                if (jobPath.path() == m_jobPath && unitName == m_serviceName && result != QLatin1String("done")) {
                    qCWarning(KIO_GUI) << "Failed to launch process as service:" << m_serviceName << ", result " << result;
                    // result=failed is not a fatal error, service is actually created in this case
                    if (result != QLatin1String("failed")) {
                        systemdError(result);
                    }
                }
            });

    const QStringList argv = escapeArguments(m_process->program());

    // Ask systemd for a new transient service
    const auto startReply =
        m_manager->StartTransientUnit(m_serviceName,
                                      QStringLiteral("fail"), // mode defines what to do in the case of a name conflict, in this case, just do nothing
                                      {
                                          // Properties of the transient service unit
                                          {QStringLiteral("Type"), QStringLiteral("simple")},
                                          {QStringLiteral("ExitType"), QStringLiteral("cgroup")},
                                          {QStringLiteral("Slice"), QStringLiteral("app.slice")},
                                          {QStringLiteral("Description"), m_description},
                                          {QStringLiteral("SourcePath"), m_desktopFilePath},
                                          {QStringLiteral("AddRef"), true}, // Asks systemd to avoid garbage collecting the service if it immediately crashes,
                                                                            // so we can be notified (see https://github.com/systemd/systemd/pull/3984)
                                          {QStringLiteral("Environment"), prepareEnvironment(m_process->processEnvironment())},
                                          {QStringLiteral("WorkingDirectory"), m_process->workingDirectory()},
                                          {QStringLiteral("ExecStart"), QVariant::fromValue(ExecCommandList{{m_process->program().first(), argv, false}})},
                                      },
                                      {} // aux is currently unused and should be passed as empty array.
        );
    connect(new QDBusPendingCallWatcher(startReply, this), &QDBusPendingCallWatcher::finished, this, [this](QDBusPendingCallWatcher *watcher) {
        QDBusPendingReply<QDBusObjectPath> reply = *watcher;
        watcher->deleteLater();
        if (reply.isError()) {
            qCWarning(KIO_GUI) << "Failed to launch process as service:" << m_serviceName << reply.error().name() << reply.error().message();
            return systemdError(reply.error().message());
        }
        qCDebug(KIO_GUI) << "Successfully asked systemd to launch process as service:" << m_serviceName;
        m_jobPath = reply.argumentAt<0>().path();
    });
}

void SystemdProcessRunner::handleProperties(QDBusPendingCallWatcher *watcher)
{
    const QDBusPendingReply<QVariantMap> reply = *watcher;
    watcher->deleteLater();
    if (reply.isError()) {
        qCWarning(KIO_GUI) << "Failed to get properties for service:" << m_serviceName << reply.error().name() << reply.error().message();
        return systemdError(reply.error().message());
    }
    qCDebug(KIO_GUI) << "Successfully retrieved properties for service:" << m_serviceName;
    if (m_exited) {
        return;
    }
    const auto properties = reply.argumentAt<0>();
    if (!m_pid) {
        setPid(properties[QStringLiteral("ExecMainPID")].value<quint32>());
        return;
    }
    const auto activeState = properties[QStringLiteral("ActiveState")].toString();
    if (activeState != QLatin1String("inactive") && activeState != QLatin1String("failed")) {
        return;
    }
    m_exited = true;

    // ExecMainCode/Status correspond to si_code/si_status in the siginfo_t structure
    // ExecMainCode is the signal code: CLD_EXITED (1) means normal exit
    // ExecMainStatus is the process exit code in case of normal exit, otherwise it is the signal number
    const auto signalCode = properties[QStringLiteral("ExecMainCode")].value<qint32>();
    const auto exitCodeOrSignalNumber = properties[QStringLiteral("ExecMainStatus")].value<qint32>();
    const auto exitStatus = signalCode == CLD_EXITED ? QProcess::ExitStatus::NormalExit : QProcess::ExitStatus::CrashExit;

    qCDebug(KIO_GUI) << m_serviceName << "pid=" << m_pid << "exitCode=" << exitCodeOrSignalNumber << "exitStatus=" << exitStatus;
    terminateStartupNotification();
    deleteLater();

    systemd1::Unit unitInterface(systemdService, m_servicePath, QDBusConnection::sessionBus(), this);
    connect(new QDBusPendingCallWatcher(unitInterface.Unref(), this), &QDBusPendingCallWatcher::finished, this, [this](QDBusPendingCallWatcher *watcher) {
        QDBusPendingReply<> reply = *watcher;
        watcher->deleteLater();
        if (reply.isError()) {
            qCWarning(KIO_GUI) << "Failed to unref service:" << m_serviceName << reply.error().name() << reply.error().message();
            return systemdError(reply.error().message());
        }
        qCDebug(KIO_GUI) << "Successfully unref'd service:" << m_serviceName;
    });
}

void SystemdProcessRunner::handleUnitNew(const QString &newName, const QDBusObjectPath &newPath)
{
    if (newName != m_serviceName) {
        return;
    }
    qCDebug(KIO_GUI) << "Successfully launched process as service:" << m_serviceName;

    // Get PID (and possibly exit code) from systemd service properties
    m_servicePath = newPath.path();
    m_serviceProperties = new DBus::Properties(systemdService, m_servicePath, QDBusConnection::sessionBus(), this);
    auto propReply = m_serviceProperties->GetAll(QString());
    connect(new QDBusPendingCallWatcher(propReply, this), &QDBusPendingCallWatcher::finished, this, &SystemdProcessRunner::handleProperties);

    // Watch for status change
    connect(m_serviceProperties, &DBus::Properties::PropertiesChanged, this, [this]() {
        if (m_exited) {
            return;
        }
        qCDebug(KIO_GUI) << "Got PropertiesChanged signal:" << m_serviceName;
        // We need to look at the full list of properties rather than only those which changed
        auto reply = m_serviceProperties->GetAll(QString());
        connect(new QDBusPendingCallWatcher(reply, this), &QDBusPendingCallWatcher::finished, this, &SystemdProcessRunner::handleProperties);
    });
}

void SystemdProcessRunner::systemdError(const QString &message)
{
    Q_EMIT error(message);
    deleteLater();
}

#include "moc_systemdprocessrunner_p.cpp"