/****************************************************************************
**
** Copyright (C) 2018 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QML preview debug service.
**
** $QT_BEGIN_LICENSE:LGPL$
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** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
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** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
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****************************************************************************/

#include "qqmlpreviewhandler.h"

#include <QtCore/qtimer.h>
#include <QtCore/qsettings.h>
#include <QtCore/qlibraryinfo.h>
#include <QtCore/qtranslator.h>

#include <QtGui/qwindow.h>
#include <QtGui/qguiapplication.h>
#include <QtQuick/qquickwindow.h>
#include <QtQuick/qquickitem.h>
#include <QtQml/qqmlcomponent.h>

#include <private/qquickpixmapcache_p.h>
#include <private/qquickview_p.h>
#include <private/qhighdpiscaling_p.h>

QT_BEGIN_NAMESPACE

struct QuitLockDisabler
{
    const bool quitLockEnabled;

    QuitLockDisabler() : quitLockEnabled(QCoreApplication::isQuitLockEnabled())
    {
        QCoreApplication::setQuitLockEnabled(false);
    }

    ~QuitLockDisabler()
    {
        QCoreApplication::setQuitLockEnabled(quitLockEnabled);
    }
};

QQmlPreviewHandler::QQmlPreviewHandler(QObject *parent) : QObject(parent)
{
    m_dummyItem.reset(new QQuickItem);

    // TODO: Is there a better way to determine this? We want to keep the window alive when possible
    //       as otherwise it will reappear in a different place when (re)loading a file. However,
    //       the file we load might create another window, in which case the eglfs plugin (and
    //       others?) will do a qFatal as it only supports a single window.
    const QString platformName = QGuiApplication::platformName();
    m_supportsMultipleWindows = (platformName == QStringLiteral("windows")
                                 || platformName == QStringLiteral("cocoa")
                                 || platformName == QStringLiteral("xcb")
                                 || platformName == QStringLiteral("wayland"));

    QCoreApplication::instance()->installEventFilter(this);

    m_fpsTimer.setInterval(1000);
    connect(&m_fpsTimer, &QTimer::timeout, this, &QQmlPreviewHandler::fpsTimerHit);
}

QQmlPreviewHandler::~QQmlPreviewHandler()
{
#if QT_CONFIG(translation)
    removeTranslators();
#endif
    clear();
}

static void closeAllWindows()
{
    const QWindowList windows = QGuiApplication::allWindows();
    for (QWindow *window : windows)
        window->close();
}

bool QQmlPreviewHandler::eventFilter(QObject *obj, QEvent *event)
{
    if (m_currentWindow && (event->type() == QEvent::Move) &&
            qobject_cast<QQuickWindow*>(obj) == m_currentWindow) {
        m_lastPosition.takePosition(m_currentWindow);
    }

    return QObject::eventFilter(obj, event);
}

void QQmlPreviewHandler::addEngine(QQmlEngine *qmlEngine)
{
    m_engines.append(qmlEngine);
}

void QQmlPreviewHandler::removeEngine(QQmlEngine *qmlEngine)
{
    const bool found = m_engines.removeOne(qmlEngine);
    Q_ASSERT(found);
    for (QObject *obj : m_createdObjects)
    if (obj && QtQml::qmlEngine(obj) == qmlEngine)
      delete obj;
    m_createdObjects.removeAll(nullptr);
}

void QQmlPreviewHandler::loadUrl(const QUrl &url)
{
    QSharedPointer<QuitLockDisabler> disabler(new QuitLockDisabler);

    clear();
    m_component.reset(nullptr);
    QQuickPixmap::purgeCache();

    const int numEngines = m_engines.count();
    if (numEngines > 1) {
        emit error(QString::fromLatin1("%1 QML engines available. We cannot decide which one "
                                       "should load the component.").arg(numEngines));
        return;
    } else if (numEngines == 0) {
        emit error(QLatin1String("No QML engines found."));
        return;
    }
    m_lastPosition.loadWindowPositionSettings(url);

    QQmlEngine *engine = m_engines.front();
    engine->clearComponentCache();
    m_component.reset(new QQmlComponent(engine, url, this));

    auto onStatusChanged = [disabler, this](QQmlComponent::Status status) {
        switch (status) {
        case QQmlComponent::Null:
        case QQmlComponent::Loading:
            return true; // try again later
        case QQmlComponent::Ready:
            tryCreateObject();
            break;
        case QQmlComponent::Error:
            emit error(m_component->errorString());
            break;
        default:
            Q_UNREACHABLE();
            break;
        }

        disconnect(m_component.data(), &QQmlComponent::statusChanged, this, nullptr);
        return false; // we're done
    };

    if (onStatusChanged(m_component->status()))
        connect(m_component.data(), &QQmlComponent::statusChanged, this, onStatusChanged);
}

void QQmlPreviewHandler::rerun()
{
    if (m_component.isNull() || !m_component->isReady())
        emit error(QLatin1String("Component is not ready."));

    QuitLockDisabler disabler;
    Q_UNUSED(disabler);
    clear();
    tryCreateObject();
}

void QQmlPreviewHandler::zoom(qreal newFactor)
{
    m_zoomFactor = newFactor;
    QTimer::singleShot(0, this, &QQmlPreviewHandler::doZoom);
}

void QQmlPreviewHandler::doZoom()
{
    if (!m_currentWindow)
        return;
    if (qFuzzyIsNull(m_zoomFactor)) {
        emit error(QString::fromLatin1("Zooming with factor: %1 will result in nothing " \
                                       "so it will be ignored.").arg(m_zoomFactor));
        return;
    }

    bool resetZoom = false;
    if (m_zoomFactor < 0) {
        resetZoom = true;
        m_zoomFactor = 1.0;
    }

    m_currentWindow->setGeometry(m_currentWindow->geometry());

    m_lastPosition.takePosition(m_currentWindow, QQmlPreviewPosition::InitializePosition);
    m_currentWindow->destroy();

    for (QScreen *screen : QGuiApplication::screens())
        QHighDpiScaling::setScreenFactor(screen, m_zoomFactor);
    if (resetZoom)
        QHighDpiScaling::updateHighDpiScaling();

    m_currentWindow->show();
    m_lastPosition.initLastSavedWindowPosition(m_currentWindow);
}

#if QT_CONFIG(translation)
void QQmlPreviewHandler::removeTranslators()
{
    if (!m_qtTranslator.isNull()) {
        QCoreApplication::removeTranslator(m_qtTranslator.get());
        m_qtTranslator.reset();
    }

    if (m_qmlTranslator.isNull()) {
        QCoreApplication::removeTranslator(m_qmlTranslator.get());
        m_qmlTranslator.reset();
    }
}

void QQmlPreviewHandler::language(const QUrl &context, const QLocale &locale)
{
    removeTranslators();

    m_qtTranslator.reset(new QTranslator(this));
    if (m_qtTranslator->load(locale, QLatin1String("qt"), QLatin1String("_"),
                           QLibraryInfo::location(QLibraryInfo::TranslationsPath))) {
        QCoreApplication::installTranslator(m_qtTranslator.get());
    }

    m_qmlTranslator.reset(new QTranslator(this));
    if (m_qmlTranslator->load(locale, QLatin1String("qml"), QLatin1String("_"),
                              context.toLocalFile() + QLatin1String("/i18n"))) {
        QCoreApplication::installTranslator(m_qmlTranslator.get());
    }

    for (QQmlEngine *engine : qAsConst(m_engines))
        engine->retranslate();
}
#endif

void QQmlPreviewHandler::clear()
{
    qDeleteAll(m_createdObjects);
    m_createdObjects.clear();
    setCurrentWindow(nullptr);
}

Qt::WindowFlags fixFlags(Qt::WindowFlags flags)
{
    // If only the type flag is given, some other window flags are automatically assumed. When we
    // add a flag, we need to make those explicit.
    switch (flags) {
    case Qt::Window:
        return flags | Qt::WindowTitleHint | Qt::WindowSystemMenuHint | Qt::WindowCloseButtonHint
                | Qt::WindowMinimizeButtonHint | Qt::WindowMaximizeButtonHint;
    case Qt::Dialog:
    case Qt::Tool:
        return flags | Qt::WindowTitleHint | Qt::WindowSystemMenuHint | Qt::WindowCloseButtonHint;
    default:
        return flags;
    }
}

void QQmlPreviewHandler::showObject(QObject *object)
{
    if (QWindow *window = qobject_cast<QWindow *>(object)) {
        setCurrentWindow(qobject_cast<QQuickWindow *>(window));
        for (QWindow *otherWindow : QGuiApplication::allWindows()) {
            if (QQuickWindow *quickWindow = qobject_cast<QQuickWindow *>(otherWindow)) {
                if (quickWindow == m_currentWindow)
                    continue;
                quickWindow->setVisible(false);
                quickWindow->setFlags(quickWindow->flags() & ~Qt::WindowStaysOnTopHint);
            }
        }
    } else if (QQuickItem *item = qobject_cast<QQuickItem *>(object)) {
        setCurrentWindow(nullptr);
        for (QWindow *window : QGuiApplication::allWindows()) {
            if (QQuickWindow *quickWindow = qobject_cast<QQuickWindow *>(window)) {
                if (m_currentWindow != nullptr) {
                    emit error(QLatin1String("Multiple QQuickWindows available. We cannot "
                                             "decide which one to use."));
                    return;
                }
                setCurrentWindow(quickWindow);
            } else {
                window->setVisible(false);
                window->setFlag(Qt::WindowStaysOnTopHint, false);
            }
        }

        if (m_currentWindow == nullptr) {
            setCurrentWindow(new QQuickWindow);
            m_createdObjects.append(m_currentWindow.data());
        }

        for (QQuickItem *oldItem : m_currentWindow->contentItem()->childItems())
            oldItem->setParentItem(m_dummyItem.data());

        // Special case for QQuickView, as that keeps a "root" pointer around, and uses it to
        // automatically resize the window or the item.
        if (QQuickView *view = qobject_cast<QQuickView *>(m_currentWindow))
            QQuickViewPrivate::get(view)->setRootObject(item);
        else
            item->setParentItem(m_currentWindow->contentItem());

        m_currentWindow->resize(item->size().toSize());
    } else {
        emit error(QLatin1String("Created object is neither a QWindow nor a QQuickItem."));
    }

    if (m_currentWindow) {
        m_lastPosition.initLastSavedWindowPosition(m_currentWindow);
        m_currentWindow->setFlags(fixFlags(m_currentWindow->flags()) | Qt::WindowStaysOnTopHint);
        m_currentWindow->setVisible(true);
    }
}

void QQmlPreviewHandler::setCurrentWindow(QQuickWindow *window)
{
    if (window == m_currentWindow.data())
        return;

    if (m_currentWindow) {
        disconnect(m_currentWindow.data(), &QQuickWindow::beforeSynchronizing,
                   this, &QQmlPreviewHandler::beforeSynchronizing);
        disconnect(m_currentWindow.data(), &QQuickWindow::afterSynchronizing,
                   this, &QQmlPreviewHandler::afterSynchronizing);
        disconnect(m_currentWindow.data(), &QQuickWindow::beforeRendering,
                   this, &QQmlPreviewHandler::beforeRendering);
        disconnect(m_currentWindow.data(), &QQuickWindow::frameSwapped,
                   this, &QQmlPreviewHandler::frameSwapped);
        m_fpsTimer.stop();
        m_rendering = FrameTime();
        m_synchronizing = FrameTime();
    }

    m_currentWindow = window;

    if (m_currentWindow) {
        connect(m_currentWindow.data(), &QQuickWindow::beforeSynchronizing,
                this, &QQmlPreviewHandler::beforeSynchronizing, Qt::DirectConnection);
        connect(m_currentWindow.data(), &QQuickWindow::afterSynchronizing,
                this, &QQmlPreviewHandler::afterSynchronizing, Qt::DirectConnection);
        connect(m_currentWindow.data(), &QQuickWindow::beforeRendering,
                this, &QQmlPreviewHandler::beforeRendering, Qt::DirectConnection);
        connect(m_currentWindow.data(), &QQuickWindow::frameSwapped,
                this, &QQmlPreviewHandler::frameSwapped, Qt::DirectConnection);
        m_fpsTimer.start();
    }
}

void QQmlPreviewHandler::beforeSynchronizing()
{
    m_synchronizing.beginFrame();
}

void QQmlPreviewHandler::afterSynchronizing()
{

    if (m_rendering.elapsed >= 0)
        m_rendering.endFrame();
    m_synchronizing.recordFrame();
    m_synchronizing.endFrame();
}

void QQmlPreviewHandler::beforeRendering()
{
    m_rendering.beginFrame();
}

void QQmlPreviewHandler::frameSwapped()
{
    m_rendering.recordFrame();
}

void QQmlPreviewHandler::FrameTime::beginFrame()
{
    timer.start();
}

void QQmlPreviewHandler::FrameTime::recordFrame()
{
    elapsed = timer.elapsed();
}

void QQmlPreviewHandler::FrameTime::endFrame()
{
    if (elapsed < min)
        min = static_cast<quint16>(qMax(0ll, elapsed));
    if (elapsed > max)
        max = static_cast<quint16>(qMin(qint64(std::numeric_limits<quint16>::max()), elapsed));
    total = static_cast<quint16>(qBound(0ll, qint64(std::numeric_limits<quint16>::max()),
                                        elapsed + total));
    ++number;
    elapsed = -1;
}

void QQmlPreviewHandler::FrameTime::reset()
{
    min = std::numeric_limits<quint16>::max();
    max = 0;
    total = 0;
    number = 0;
}

void QQmlPreviewHandler::fpsTimerHit()
{
    const FpsInfo info = {
        m_synchronizing.number,
        m_synchronizing.min,
        m_synchronizing.max,
        m_synchronizing.total,

        m_rendering.number,
        m_rendering.min,
        m_rendering.max,
        m_rendering.total
    };

    emit fps(info);

    m_rendering.reset();
    m_synchronizing.reset();
}

void QQmlPreviewHandler::tryCreateObject()
{
    if (!m_supportsMultipleWindows)
        closeAllWindows();
    QObject *object = m_component->create();
    m_createdObjects.append(object);
    showObject(object);
}

QT_END_NAMESPACE
