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

#ifdef QT_GUI_LIB
#  include <QtGui/QGuiApplication>
#else
#  include <QtCore/QCoreApplication>
#endif
#include <QTest>
#include <QAbstractEventDispatcher>
#include <QElapsedTimer>
#include <QTimer>
#include <QThreadPool>

#ifdef DISABLE_GLIB
static bool glibDisabled = []() {
    qputenv("QT_NO_GLIB", "1");
    return true;
}();
#endif

#include <chrono>

#ifndef QTEST_THROW_ON_FAIL
# error This test requires QTEST_THROW_ON_FAIL being active.
#endif

using namespace std::chrono_literals;

static constexpr auto PreciseTimerInterval = 10ms;
static constexpr auto CoarseTimerInterval = 200ms;
static constexpr auto VeryCoarseTimerInterval = 1s;

static constexpr
std::chrono::nanoseconds fudgeInterval(std::chrono::nanoseconds interval, Qt::TimerType timerType)
{
    // Make the intervals have have fractions of milliseconds so we can check
    // that they have been rounded & stored properly (where applicable).
    switch (timerType) {
    case Qt::VeryCoarseTimer:
        // rounds down (floor) to seconds
        return interval + 1010us;
    case Qt::CoarseTimer:
        // rounds up (ceil) to milliseconds
        return interval - 10us;
    case Qt::PreciseTimer:
        // not rounded using QAbstractEventDispatcherV2; rounded up (ceil) on V1
        return interval - 10us;
    }
    Q_UNREACHABLE_RETURN(std::chrono::nanoseconds::min());
}

class tst_QEventDispatcher : public QObject
{
    Q_OBJECT

    QAbstractEventDispatcher *eventDispatcher;

    int receivedEventType = -1;
    int timerIdFromEvent = -1;
    bool doubleTimer = false;

protected:
    bool event(QEvent *e) override;

public:
    inline tst_QEventDispatcher()
        : QObject(),
          eventDispatcher(QAbstractEventDispatcher::instance(thread())),
          isGuiEventDispatcher(QCoreApplication::instance()->inherits("QGuiApplication"))
    { }

private slots:
    void initTestCase();
    void cleanup();

    void registerTimer();

    /* void registerSocketNotifier(); */ // Not implemented here, see tst_QSocketNotifier instead
    /* void registerEventNotifiier(); */ // Not implemented here, see tst_QWinEventNotifier instead
    void sendPostedEvents_data();
    void sendPostedEvents();
    void processEventsOnlySendsQueuedEvents();
    // these two tests need to run before postedEventsPingPong
    void postEventFromThread();
    void postEventFromEventHandler();
    // these tests don't leave the event dispatcher in a reliable state
    void postedEventsPingPong();
    void eventLoopExit();
    void interruptTrampling();

private:
    const bool isGuiEventDispatcher;
};

bool tst_QEventDispatcher::event(QEvent *e)
{
    switch (receivedEventType = e->type()) {
    case QEvent::Timer:
    {
        // sometimes, two timers fire during a single QTRY_xxx wait loop
        if (timerIdFromEvent != -1)
            doubleTimer = true;
        timerIdFromEvent = static_cast<QTimerEvent *>(e)->timerId();
        return true;
    }
    default:
        break;
    }
    return QObject::event(e);
}

// drain the system event queue after the test starts to avoid destabilizing the test functions
void tst_QEventDispatcher::initTestCase()
{
    QDeadlineTimer deadline(CoarseTimerInterval);
    while (!deadline.hasExpired() && eventDispatcher->processEvents(QEventLoop::AllEvents))
        ;
}

// consume pending posted events to avoid impact on the next test function
void tst_QEventDispatcher::cleanup()
{
    eventDispatcher->processEvents(QEventLoop::AllEvents);
}

class TimerManager {
    Q_DISABLE_COPY(TimerManager)

public:
    TimerManager(QAbstractEventDispatcher *eventDispatcher, QObject *parent)
        : m_eventDispatcher(eventDispatcher), m_parent(parent)
    {
    }

    ~TimerManager()
    {
        if (!registeredTimers().isEmpty())
            m_eventDispatcher->unregisterTimers(m_parent);
    }

    TimerManager(TimerManager &&) = delete;
    TimerManager &operator=(TimerManager &&) = delete;

    int preciseTimerId() const { return int(m_preciseTimerId); }
    int coarseTimerId() const { return int(m_coarseTimerId); }
    int veryCoarseTimerId() const { return int(m_veryCoarseTimerId); }

    bool foundPrecise() const { return preciseTimerId() > 0; }
    bool foundCoarse() const { return coarseTimerId() > 0; }
    bool foundVeryCoarse() const { return veryCoarseTimerId() > 0; }

    QList<QAbstractEventDispatcher::TimerInfoV2> registeredTimers() const
    {
        return m_eventDispatcher->timersForObject(m_parent);
    }

    void registerAll()
    {
        // start 3 timers, each with the different timer types and different intervals
        auto registerTimer = [&](std::chrono::milliseconds interval, Qt::TimerType timerType) {
            return m_eventDispatcher->registerTimer(fudgeInterval(interval, timerType), timerType,
                                                    m_parent);
        };
        m_preciseTimerId = registerTimer(PreciseTimerInterval, Qt::PreciseTimer);
        m_coarseTimerId = registerTimer(CoarseTimerInterval, Qt::CoarseTimer);
        m_veryCoarseTimerId = registerTimer(VeryCoarseTimerInterval, Qt::VeryCoarseTimer);
        QVERIFY(foundPrecise());
        QVERIFY(foundCoarse());
        QVERIFY(foundVeryCoarse());
        findTimers();
    }

    void unregister(Qt::TimerId timerId)
    {
        m_eventDispatcher->unregisterTimer(timerId);
        findTimers();
    }

    void unregisterAll()
    {
        m_eventDispatcher->unregisterTimers(m_parent);
        findTimers();
    }

private:
    void findTimers()
    {
        bool foundPrecise = false;
        bool foundCoarse = false;
        bool foundVeryCoarse = false;
        const QList<QAbstractEventDispatcher::TimerInfoV2> timers = registeredTimers();
        for (const QAbstractEventDispatcher::TimerInfoV2 &timerInfo : timers) {
            if (timerInfo.timerId == m_preciseTimerId) {
                // For precise timers, we expect the fudge factor to be present
                QAbstractEventDispatcher::Duration interval =
                        fudgeInterval(PreciseTimerInterval, Qt::PreciseTimer);
#ifdef Q_OS_WIN
                // Windows does not have a nanosecond-resolution timer
                interval = PreciseTimerInterval;
#endif
                QCOMPARE(timerInfo.interval, interval);
                QCOMPARE(timerInfo.timerType, Qt::PreciseTimer);
                foundPrecise = true;
            } else if (timerInfo.timerId == m_coarseTimerId) {
                // For other timers, the fudge factors ought to have been rounded away
                QCOMPARE(timerInfo.interval, CoarseTimerInterval);
                QCOMPARE(timerInfo.timerType, Qt::CoarseTimer);
                foundCoarse = true;
            } else if (timerInfo.timerId == m_veryCoarseTimerId) {
                QCOMPARE(timerInfo.interval, VeryCoarseTimerInterval);
                QCOMPARE(timerInfo.timerType, Qt::VeryCoarseTimer);
                foundVeryCoarse = true;
            }
        }
        if (!foundPrecise)
            m_preciseTimerId = Qt::TimerId::Invalid;
        if (!foundCoarse)
            m_coarseTimerId = Qt::TimerId::Invalid;
        if (!foundVeryCoarse)
            m_veryCoarseTimerId = Qt::TimerId::Invalid;
    }

    QAbstractEventDispatcher *m_eventDispatcher = nullptr;

    Qt::TimerId m_preciseTimerId = Qt::TimerId::Invalid;
    Qt::TimerId m_coarseTimerId = Qt::TimerId::Invalid;
    Qt::TimerId m_veryCoarseTimerId = Qt::TimerId::Invalid;

    QObject *m_parent = nullptr;
};

// test that the eventDispatcher's timer implementation is complete and working
void tst_QEventDispatcher::registerTimer()
{
    TimerManager timers(eventDispatcher, this);
    timers.registerAll();

    // check that all 3 are present in the eventDispatcher's registeredTimer() list
    QCOMPARE(timers.registeredTimers().size(), 3);
    QVERIFY(timers.foundPrecise());
    QVERIFY(timers.foundCoarse());
    QVERIFY(timers.foundVeryCoarse());

#ifdef Q_OS_DARWIN
    /*
        We frequently experience flaky failures on macOS. Assumption is that this is
        due to undeterministic VM scheduling, making us process events for significantly
        longer than expected and resulting in timers firing in undefined order.
        To detect this condition, we use a QElapsedTimer, and skip the test.
    */
    QElapsedTimer elapsedTimer;
    elapsedTimer.start();
#endif

    // process events, waiting for the next event... this should only fire the precise timer
    receivedEventType = -1;
    timerIdFromEvent = -1;
    doubleTimer = false;
    QTRY_COMPARE_WITH_TIMEOUT(receivedEventType, int(QEvent::Timer), PreciseTimerInterval * 2);

#ifdef Q_OS_DARWIN
    if (doubleTimer)
        QSKIP("Double timer during a single timeout - aborting test as flaky on macOS");
    if (timerIdFromEvent != timers.preciseTimerId()
        && elapsedTimer.durationElapsed() > PreciseTimerInterval * 3)
        QSKIP("Ignore flaky test behavior due to VM scheduling on macOS");
#endif

    QCOMPARE(timerIdFromEvent, timers.preciseTimerId());
    // now unregister it and make sure it's gone
    timers.unregister(Qt::TimerId(timers.preciseTimerId()));
    QCOMPARE(timers.registeredTimers().size(), 2);
    QVERIFY(!timers.foundPrecise());
    QVERIFY(timers.foundCoarse());
    QVERIFY(timers.foundVeryCoarse());

    // do the same again for the coarse timer
    receivedEventType = -1;
    timerIdFromEvent = -1;
    doubleTimer = false;
    QTRY_COMPARE_WITH_TIMEOUT(receivedEventType, int(QEvent::Timer), CoarseTimerInterval * 2);

#ifdef Q_OS_DARWIN
    if (doubleTimer)
        QSKIP("Double timer during a single timeout - aborting test as flaky on macOS");
    if (timerIdFromEvent != timers.coarseTimerId()
        && elapsedTimer.durationElapsed() > CoarseTimerInterval * 3)
        QSKIP("Ignore flaky test behavior due to VM scheduling on macOS");
#endif

    QCOMPARE(timerIdFromEvent, timers.coarseTimerId());
    // now unregister it and make sure it's gone
    timers.unregister(Qt::TimerId(timers.coarseTimerId()));
    QCOMPARE(timers.registeredTimers().size(), 1);
    QVERIFY(!timers.foundPrecise());
    QVERIFY(!timers.foundCoarse());
    QVERIFY(timers.foundVeryCoarse());

    // not going to wait for the VeryCoarseTimer, would take too long, just unregister it
    timers.unregisterAll();
    QVERIFY(timers.registeredTimers().isEmpty());
}

void tst_QEventDispatcher::sendPostedEvents_data()
{
    QTest::addColumn<int>("processEventsFlagsInt");

    QTest::newRow("WaitForMoreEvents") << int(QEventLoop::WaitForMoreEvents);
    QTest::newRow("AllEvents") << int(QEventLoop::AllEvents);
}

// test that the eventDispatcher sends posted events correctly
void tst_QEventDispatcher::sendPostedEvents()
{
    QFETCH(int, processEventsFlagsInt);
    QEventLoop::ProcessEventsFlags processEventsFlags = QEventLoop::ProcessEventsFlags(processEventsFlagsInt);

    QDeadlineTimer deadline(200ms);
    while (!deadline.hasExpired()) {
        receivedEventType = -1;
        QCoreApplication::postEvent(this, new QEvent(QEvent::User));

        // event shouldn't be delivered as a result of posting
        QCOMPARE(receivedEventType, -1);

        // since there is a pending posted event, this should not actually block, it should send the posted event and return
        QVERIFY(eventDispatcher->processEvents(processEventsFlags));
        // event shouldn't be delivered as a result of posting
        QCOMPARE(receivedEventType, int(QEvent::User));
    }
}

class ProcessEventsOnlySendsQueuedEvents : public QObject
{
    Q_OBJECT
public:
    int eventsReceived;

    inline ProcessEventsOnlySendsQueuedEvents() : eventsReceived(0) {}

    bool event(QEvent *event) override
    {
        ++eventsReceived;

        if (event->type() == QEvent::User)
             QCoreApplication::postEvent(this, new QEvent(QEvent::Type(QEvent::User + 1)));

        return QObject::event(event);
    }
public slots:
    void timerFired()
    {
        QCoreApplication::postEvent(this, new QEvent(QEvent::Type(QEvent::User + 1)));
    }
};

void tst_QEventDispatcher::processEventsOnlySendsQueuedEvents()
{
    ProcessEventsOnlySendsQueuedEvents object;

    // Posted events during event processing should be handled on
    // the next processEvents iteration.
    QCoreApplication::postEvent(&object, new QEvent(QEvent::User));
    QCoreApplication::processEvents();
    QCOMPARE(object.eventsReceived, 1);
    QCoreApplication::processEvents();
    QCOMPARE(object.eventsReceived, 2);

    // The same goes for posted events during timer processing
    QTimer::singleShot(0, &object, SLOT(timerFired()));
    QCoreApplication::processEvents();
    QCOMPARE(object.eventsReceived, 3);
    QCoreApplication::processEvents();
    QCOMPARE(object.eventsReceived, 4);
}

void tst_QEventDispatcher::postEventFromThread()
{
    QThreadPool *threadPool = QThreadPool::globalInstance();
    QAtomicInt hadToQuit = false;
    QAtomicInt done = false;

    int threadCount = 500;
    const int timeout = (1000
#if defined(QT_GUI_LIB)
        // Aggressively posting events may on some platforms rate limit us to
        // the display's refresh rate, so give us enough time if that happens.
        + ((1000.0 / qGuiApp->primaryScreen()->refreshRate()) * threadCount)
#endif
    );

    threadPool->start([&]{
        int loop = timeout / 10;
        while (!done && --loop)
            QThread::sleep(std::chrono::milliseconds{10});
        if (done)
            return;
        hadToQuit = true;
        QCoreApplication::eventDispatcher()->wakeUp();
    });

    struct EventReceiver : public QObject {
        bool event(QEvent* event) override {
            if (event->type() == QEvent::User)
                return true;
            return QObject::event(event);
        }
    } receiver;

    while (!hadToQuit && --threadCount) {
        threadPool->start([&receiver]{
            QCoreApplication::postEvent(&receiver, new QEvent(QEvent::User));
        });

        QAbstractEventDispatcher::instance()->processEvents(QEventLoop::WaitForMoreEvents);
    }
    done = true;

    QVERIFY(!hadToQuit);
    QVERIFY(threadPool->waitForDone());
}

void tst_QEventDispatcher::postEventFromEventHandler()
{
    QThreadPool *threadPool = QThreadPool::globalInstance();
    QAtomicInt hadToQuit = false;
    QAtomicInt done = false;

    threadPool->start([&]{
        int loop = 250 / 10; // give it 250ms
        while (!done && --loop)
            QThread::sleep(std::chrono::milliseconds{10});
        if (done)
            return;
        hadToQuit = true;
        QCoreApplication::eventDispatcher()->wakeUp();
    });

    struct EventReceiver : public QObject {
        int i = 0;
        bool event(QEvent* event) override
        {
            if (event->type() == QEvent::User) {
                ++i;
                if (i < 2)
                    QCoreApplication::postEvent(this, new QEvent(QEvent::User));
                return true;
            }
            return QObject::event(event);
        }
    } receiver;
    QCoreApplication::postEvent(&receiver, new QEvent(QEvent::User));
    while (receiver.i < 2)
        QAbstractEventDispatcher::instance()->processEvents(QEventLoop::WaitForMoreEvents);
    done = true;

    const QByteArrayView eventDispatcherName(QAbstractEventDispatcher::instance()->metaObject()->className());
    qDebug() << eventDispatcherName;
    // QEventDispatcherWin32 and QWindowsGuiEventDispatcher do not do this correctly.
    const bool knownToFail = eventDispatcherName.contains("Win32")
                          || eventDispatcherName.contains("WindowsGui");

    if (knownToFail)
        QEXPECT_FAIL("", eventDispatcherName.constData(), Continue);

    QVERIFY(!hadToQuit);
    QVERIFY(threadPool->waitForDone());
}


void tst_QEventDispatcher::postedEventsPingPong()
{
    QEventLoop mainLoop;

    // We need to have at least two levels of nested loops
    // for the posted event to get stuck (QTBUG-85981).
    QMetaObject::invokeMethod(this, [this, &mainLoop]() {
        QMetaObject::invokeMethod(this, [&mainLoop]() {
            // QEventLoop::quit() should be invoked on the next
            // iteration of mainLoop.exec().
            QMetaObject::invokeMethod(&mainLoop, &QEventLoop::quit,
                                      Qt::QueuedConnection);
        }, Qt::QueuedConnection);
        mainLoop.processEvents();
    }, Qt::QueuedConnection);

    // We should use Qt::CoarseTimer on Windows, to prevent event
    // dispatcher from sending a posted event.
    QTimer::singleShot(500, Qt::CoarseTimer, &mainLoop, [&mainLoop]() {
        mainLoop.exit(1);
    });

    QCOMPARE(mainLoop.exec(), 0);
}

void tst_QEventDispatcher::eventLoopExit()
{
    // This test was inspired by QTBUG-79477. A particular
    // implementation detail in QCocoaEventDispatcher allowed
    // QEventLoop::exit() to fail to really exit the event loop.
    // Thus this test is a part of the dispatcher auto-test.

    // Imitates QApplication::exec():
    QEventLoop mainLoop;
    // The test itself is a lambda:
    QTimer::singleShot(0, &mainLoop, [&mainLoop]() {
        // Two more single shots, both will be posted as events
        // (zero timeout) and supposed to be processes by the
        // mainLoop:

        QTimer::singleShot(0, &mainLoop, [&mainLoop]() {
            // wakeUp triggers QCocoaEventDispatcher into incrementing
            // its 'serialNumber':
            mainLoop.wakeUp();
            // QCocoaEventDispatcher::processEvents() will process
            // posted events and execute the second lambda defined below:
            QCoreApplication::processEvents();
        });

        QTimer::singleShot(0, &mainLoop, [&mainLoop]() {
            // With QCocoaEventDispatcher this is executed while in the
            // processEvents (see above) and would fail to actually
            // interrupt the loop.
            mainLoop.exit();
        });
    });

    bool timeoutObserved = false;
    QTimer::singleShot(500, &mainLoop, [&timeoutObserved, &mainLoop]() {
        // In case the QEventLoop::exit above failed, we have to bail out
        // early, not wasting time:
        mainLoop.exit();
        timeoutObserved = true;
    });

    mainLoop.exec();
    QVERIFY(!timeoutObserved);
}

// Based on QTBUG-91539: In the event dispatcher on Windows we overwrite the
// interrupt once we start processing events (this pattern is also in the 'unix' dispatcher)
// which would lead the dispatcher to accidentally ignore certain interrupts and,
// as in the bug report, would not quit, leaving the thread alive and running.
void tst_QEventDispatcher::interruptTrampling()
{
    class WorkerThread : public QThread
    {
        void run() override {
            auto dispatcher = eventDispatcher();
            QVERIFY(dispatcher);
            dispatcher->processEvents(QEventLoop::AllEvents);
            QTimer::singleShot(0, dispatcher, [dispatcher]() {
                dispatcher->wakeUp();
            });
            dispatcher->processEvents(QEventLoop::WaitForMoreEvents);
            dispatcher->interrupt();
            dispatcher->processEvents(QEventLoop::WaitForMoreEvents);
        }
    };
    WorkerThread thread;
    thread.start();
    QVERIFY(thread.wait(1000));
    QVERIFY(thread.isFinished());
}

QTEST_MAIN(tst_QEventDispatcher)
#include "tst_qeventdispatcher.moc"
