/*
 * breezewindowmanager.cpp
 * pass some window mouse press/release/move event actions to window manager
 * Largely inspired from BeSpin style
 *
 * SPDX-FileCopyrightText: 2007 Thomas Luebking <thomas.luebking@web.de>
 * SPDX-FileCopyrightText: 2014 Hugo Pereira Da Costa <hugo.pereira@free.fr>
 *
 * SPDX-License-Identifier: GPL-2.0-or-later OR MIT
 */

#include "breezewindowmanager.h"
#include "breezepropertynames.h"
#include "breezehelper.h"

#include <QComboBox>
#include <QDialog>
#include <QDockWidget>
#include <QGraphicsView>
#include <QGroupBox>
#include <QLabel>
#include <QListView>
#include <QMainWindow>
#include <QMdiSubWindow>
#include <QMenuBar>
#include <QMouseEvent>
#include <QProgressBar>
#include <QScreen>
#include <QScrollBar>
#include <QStatusBar>
#include <QStyle>
#include <QStyleOptionGroupBox>
#include <QTabBar>
#include <QTabWidget>
#include <QToolBar>
#include <QToolButton>
#include <QTreeView>

#include <QTextStream>

// needed to deal with device pixel ratio
#include <QWindow>

#if BREEZE_HAVE_QTQUICK
// needed to enable dragging from QQuickWindows
#include <QQuickWindow>
#include <QQuickRenderControl>
#endif

namespace Util
{
    template<class T>
        inline T makeT( std::initializer_list<typename T::key_type>&& reference )
    {
        return T( std::move( reference ) );
    }
}

namespace Breeze
{

    //* provide application-wise event filter
    /**
    it us used to unlock dragging and make sure event look is properly restored
    after a drag has occurred
    */
    class AppEventFilter: public QObject
    {

        public:

        //* constructor
        explicit AppEventFilter( WindowManager* parent ):
            QObject( parent ),
            _parent( parent )
        {}

        //* event filter
        bool eventFilter( QObject* object, QEvent* event ) override
        {

            if( event->type() == QEvent::MouseButtonRelease )
            {

                // stop drag timer
                if( _parent->_dragTimer.isActive() )
                { _parent->resetDrag(); }

                // unlock
                if( _parent->isLocked() )
                { _parent->setLocked( false ); }

            }

            if( !_parent->enabled() ) return false;

            /*
            if a drag is in progress, the widget will not receive any event
            we trigger on the first MouseMove or MousePress events that are received
            by any widget in the application to detect that the drag is finished
            */
            if( _parent->_dragInProgress && _parent->_target && ( event->type() == QEvent::MouseMove || event->type() == QEvent::MouseButtonPress ) )
            { return appMouseEvent( object, event ); }

            return false;

        }

        protected:

        //* application-wise event.
        /** needed to catch end of XMoveResize events */
        bool appMouseEvent( QObject*, QEvent* event )
        {

            Q_UNUSED( event );

            /*
            post some mouseRelease event to the target, in order to counter balance
            the mouse press that triggered the drag. Note that it triggers a resetDrag
            */
            QMouseEvent mouseEvent( QEvent::MouseButtonRelease, _parent->_dragPoint, Qt::LeftButton, Qt::LeftButton, Qt::NoModifier );
            qApp->sendEvent( _parent->_target.data(), &mouseEvent );

            return false;

        }

        private:

        //* parent
        WindowManager* _parent = nullptr;

    };

    //_____________________________________________________________
    WindowManager::WindowManager( QObject* parent ):
        QObject( parent )
    {

        // install application wise event filter
        _appEventFilter = new AppEventFilter( this );
        qApp->installEventFilter( _appEventFilter );

    }

    //_____________________________________________________________
    void WindowManager::initialize()
    {

        setEnabled( StyleConfigData::windowDragMode() != StyleConfigData::WD_NONE );
        setDragMode( StyleConfigData::windowDragMode() );
        setDragDistance( QApplication::startDragDistance() );
        setDragDelay( QApplication::startDragTime() );

        initializeWhiteList();
        initializeBlackList();

    }

    //_____________________________________________________________
    void WindowManager::registerWidget( QWidget* widget )
    {

        if( isBlackListed( widget ) || isDragable( widget ) || widget->inherits( "QQuickWidget" ) )
        {

            /*
            install filter for dragable widgets.
            also install filter for blacklisted widgets
            to be able to catch the relevant events and prevent
            the drag to happen
            */
            widget->removeEventFilter( this );
            widget->installEventFilter( this );

        }

    }

    #if BREEZE_HAVE_QTQUICK
    //_____________________________________________________________
    void WindowManager::registerQuickItem( QQuickItem* item )
    {
        if ( !item ) return;

        if( auto window = item->window() )
        {
            auto contentItem = window->contentItem();
            contentItem->setAcceptedMouseButtons( Qt::LeftButton );
            contentItem->removeEventFilter( this );
            contentItem->installEventFilter( this );
        }

    }
    #endif

    //_____________________________________________________________
    void WindowManager::unregisterWidget( QWidget* widget )
    { if( widget ) widget->removeEventFilter( this ); }

    //_____________________________________________________________
    void WindowManager::initializeWhiteList()
    {

        _whiteList = Util::makeT<ExceptionSet>({
            ExceptionId( QStringLiteral( "MplayerWindow" ) ),
            ExceptionId( QStringLiteral( "ViewSliders@kmix" ) ),
            ExceptionId( QStringLiteral( "Sidebar_Widget@konqueror" ) )
        });

        foreach( const QString& exception, StyleConfigData::windowDragWhiteList() )
        {
            ExceptionId id( exception );
            if( !id.className().isEmpty() )
            { _whiteList.insert( ExceptionId( exception ) ); }
        }
    }

    //_____________________________________________________________
    void WindowManager::initializeBlackList()
    {

        _blackList = Util::makeT<ExceptionSet>({
            ExceptionId( QStringLiteral( "CustomTrackView@kdenlive" ) ),
            ExceptionId( QStringLiteral( "MuseScore" ) ),
            ExceptionId( QStringLiteral( "KGameCanvasWidget" ) )
        });

        foreach( const QString& exception, StyleConfigData::windowDragBlackList() )
        {
            ExceptionId id( exception );
            if( !id.className().isEmpty() )
            { _blackList.insert( ExceptionId( exception ) ); }
        }

    }

    //_____________________________________________________________
    bool WindowManager::eventFilter( QObject* object, QEvent* event )
    {
        if( !enabled() ) return false;

        switch ( event->type() )
        {
            case QEvent::MouseButtonPress:
            return mousePressEvent( object, event );
            break;

            case QEvent::MouseMove:
            if ( object == _target.data()
                #if BREEZE_HAVE_QTQUICK
                || object == _quickTarget.data()
                #endif
               ) return mouseMoveEvent( object, event );
            break;

            case QEvent::MouseButtonRelease:
            if ( _target
                #if BREEZE_HAVE_QTQUICK
                || _quickTarget
                #endif
               ) return mouseReleaseEvent( object, event );
            break;

            default:
            break;

        }

        return false;

    }

    //_____________________________________________________________
    void WindowManager::timerEvent( QTimerEvent* event )
    {

        if( event->timerId() == _dragTimer.timerId() )
        {

            _dragTimer.stop();
            setLocked( false );
            if( _target ) startDrag( _target.data()->window()->windowHandle() );
            #if BREEZE_HAVE_QTQUICK
            else if( _quickTarget ) {
                _quickTarget.data()->ungrabMouse();
                startDrag( _quickTarget.data()->window() );
            }
            #endif
            resetDrag();
        } else {

            return QObject::timerEvent( event );

        }

    }

    //_____________________________________________________________
    bool WindowManager::mousePressEvent( QObject* object, QEvent* event )
    {

        // cast event and check buttons/modifiers
        auto mouseEvent = static_cast<QMouseEvent*>( event );
        if (mouseEvent->source() != Qt::MouseEventNotSynthesized)
        { return false; }
        if( !( mouseEvent->modifiers() == Qt::NoModifier && mouseEvent->button() == Qt::LeftButton ) )
        { return false; }

        // If we are in a QQuickWidget we don't want to ever do dragging from a qwidget in the
        // hyerarchy, but only from an internal item, if any. If any event handler will manage
        // the event, we don't want the drag to start
        if( object->inherits( "QQuickWidget" ) ) {
            _eventInQQuickWidget = true;
            event->setAccepted(false);
            return false;
        }

        // check lock
        if( isLocked() ) return false;
        else setLocked( true );

        #if BREEZE_HAVE_QTQUICK
        // check QQuickItem - we can immediately start drag, because QQuickWindow's contentItem
        // only receives mouse events that weren't handled by children
        if( auto item = qobject_cast<QQuickItem*>( object ) )
        {
            _quickTarget = item;
            _dragPoint = mouseEvent->pos();
            _globalDragPoint = mouseEvent->globalPos();

            if( _dragTimer.isActive() ) _dragTimer.stop();
            _dragTimer.start( _dragDelay, this );

            return true;
        }
        #endif

        if (_eventInQQuickWidget) {
            event->setAccepted(true);
            return false;
        }
        _eventInQQuickWidget = false;

        // cast to widget
        auto widget = static_cast<QWidget*>( object );

        // check if widget can be dragged from current position
        if( isBlackListed( widget ) || !canDrag( widget ) ) return false;

        // retrieve widget's child at event position
        auto position( mouseEvent->pos() );
        auto child = widget->childAt( position );
        if( !canDrag( widget, child, position ) ) return false;

        // save target and drag point
        _target = widget;
        _dragPoint = position;
        _globalDragPoint = mouseEvent->globalPos();
        _dragAboutToStart = true;

        // send a move event to the current child with same position
        // if received, it is caught to actually start the drag
        auto localPoint( _dragPoint );
        if( child ) localPoint = child->mapFrom( widget, localPoint );
        else child = widget;
        QMouseEvent localMouseEvent( QEvent::MouseMove, localPoint, Qt::LeftButton, Qt::LeftButton, Qt::NoModifier );
        qApp->sendEvent( child, &localMouseEvent );

        // never eat event
        return false;

    }

    //_____________________________________________________________
    bool WindowManager::mouseMoveEvent( QObject* object, QEvent* event )
    {

        Q_UNUSED( object );

        // stop timer
        if( _dragTimer.isActive() ) _dragTimer.stop();

        // cast event and check drag distance
        auto mouseEvent = static_cast<QMouseEvent*>( event );
        if (mouseEvent->source() != Qt::MouseEventNotSynthesized)
        { return false; }
        if( !_dragInProgress )
        {

            if( _dragAboutToStart )
            {
                if( mouseEvent->pos() == _dragPoint )
                {
                    // start timer,
                    _dragAboutToStart = false;
                    if( _dragTimer.isActive() ) _dragTimer.stop();
                    _dragTimer.start( _dragDelay, this );

                } else resetDrag();

            } else if( QPoint( mouseEvent->globalPos() - _globalDragPoint ).manhattanLength() >= _dragDistance ) {

                _dragTimer.start( 0, this );

            }

            return true;

        } else return false;

    }

    //_____________________________________________________________
    bool WindowManager::mouseReleaseEvent( QObject* object, QEvent* event )
    {

        Q_UNUSED( object );
        Q_UNUSED( event );
        resetDrag();
        return false;
    }

    //_____________________________________________________________
    bool WindowManager::isDragable( QWidget* widget )
    {

        // check widget
        if( !widget ) return false;

        // accepted default types
        if(
            ( qobject_cast<QDialog*>( widget ) && widget->isWindow() ) ||
            ( qobject_cast<QMainWindow*>( widget ) && widget->isWindow() ) ||
            qobject_cast<QGroupBox*>( widget ) )
        { return true; }

        // more accepted types, provided they are not dock widget titles
        if( ( qobject_cast<QMenuBar*>( widget ) ||
            qobject_cast<QTabBar*>( widget ) ||
            qobject_cast<QStatusBar*>( widget ) ||
            qobject_cast<QToolBar*>( widget ) ) &&
            !isDockWidgetTitle( widget ) )
        { return true; }

        if( widget->inherits( "KScreenSaver" ) && widget->inherits( "KCModule" ) )
        { return true; }

        if( isWhiteListed( widget ) )
        { return true; }

        // flat toolbuttons
        if( auto toolButton = qobject_cast<QToolButton*>( widget ) )
        { if( toolButton->autoRaise() ) return true; }

        // viewports
        /*
        one needs to check that
        1/ the widget parent is a scrollarea
        2/ it matches its parent viewport
        3/ the parent is not blacklisted
        */
        if( auto listView = qobject_cast<QListView*>( widget->parentWidget() ) )
        { if( listView->viewport() == widget && !isBlackListed( listView ) ) return true; }

        if( auto treeView = qobject_cast<QTreeView*>( widget->parentWidget() ) )
        { if( treeView->viewport() == widget && !isBlackListed( treeView ) ) return true; }

        /*
        catch labels in status bars.
        this is because of kstatusbar
        who captures buttonPress/release events
        */
        if( auto label = qobject_cast<QLabel*>( widget ) )
        {
            if( label->textInteractionFlags().testFlag( Qt::TextSelectableByMouse ) ) return false;

            QWidget* parent = label->parentWidget();
            while( parent )
            {
                if( qobject_cast<QStatusBar*>( parent ) ) return true;
                parent = parent->parentWidget();
            }
        }

        return false;

    }

    //_____________________________________________________________
    bool WindowManager::isBlackListed( QWidget* widget )
    {

        // check against noAnimations property
        const auto propertyValue( widget->property( PropertyNames::noWindowGrab ) );
        if( propertyValue.isValid() && propertyValue.toBool() ) return true;

        // list-based blacklisted widgets
        const auto appName( qApp->applicationName() );
        foreach( const ExceptionId& id, _blackList )
        {
            if( !id.appName().isEmpty() && id.appName() != appName ) continue;
            if( id.className() == QStringLiteral( "*" ) && !id.appName().isEmpty() )
            {
                // if application name matches and all classes are selected
                // disable the grabbing entirely
                setEnabled( false );
                return true;
            }
            if( widget->inherits( id.className().toLatin1().data() ) ) return true;
        }

        return false;
    }

    //_____________________________________________________________
    bool WindowManager::isWhiteListed( QWidget* widget ) const
    {

        const auto appName( qApp->applicationName() );
        foreach( const ExceptionId& id, _whiteList )
        {
            if( !(id.appName().isEmpty() || id.appName() == appName ) ) continue;
            if( widget->inherits( id.className().toLatin1().data() ) ) return true;
        }

        return false;
    }

    //_____________________________________________________________
    bool WindowManager::canDrag( QWidget* widget )
    {

        // check if enabled
        if( !enabled() ) return false;

        // assume isDragable widget is already passed
        // check some special cases where drag should not be effective

        // check mouse grabber
        if( QWidget::mouseGrabber() ) return false;

        /*
        check cursor shape.
        Assume that a changed cursor means that some action is in progress
        and should prevent the drag
        */
        if( widget->cursor().shape() != Qt::ArrowCursor ) return false;

        // accept
        return true;

    }

    //_____________________________________________________________
    bool WindowManager::canDrag( QWidget* widget, QWidget* child, const QPoint& position )
    {

        // retrieve child at given position and check cursor again
        if( child && child->cursor().shape() != Qt::ArrowCursor ) return false;

        /*
        check against children from which drag should never be enabled,
        even if mousePress/Move has been passed to the parent
        */
        if( child && (
            qobject_cast<QComboBox*>(child ) ||
            qobject_cast<QProgressBar*>( child ) ||
            qobject_cast<QScrollBar*>( child ) ) )
        { return false; }

        // tool buttons
        if( auto toolButton = qobject_cast<QToolButton*>( widget ) )
        {
            if( dragMode() == StyleConfigData::WD_MINIMAL && !qobject_cast<QToolBar*>(widget->parentWidget() ) ) return false;
            return toolButton->autoRaise() && !toolButton->isEnabled();
        }

        // check menubar
        if( auto menuBar = qobject_cast<QMenuBar*>( widget ) )
        {

            // do not drag from menubars embedded in Mdi windows
            if( findParent<QMdiSubWindow*>( widget ) ) return false;

            // check if there is an active action
            if( menuBar->activeAction() && menuBar->activeAction()->isEnabled() ) return false;

            // check if action at position exists and is enabled
            if( auto action = menuBar->actionAt( position ) )
            {
                if( action->isSeparator() ) return true;
                if( action->isEnabled() ) return false;
            }

            // return true in all other cases
            return true;

        }

        /*
        in MINIMAL mode, anything that has not been already accepted
        and does not come from a toolbar is rejected
        */
        if( dragMode() == StyleConfigData::WD_MINIMAL )
        {
            if( qobject_cast<QToolBar*>( widget ) ) return true;
            else return false;
        }

        /* following checks are relevant only for WD_FULL mode */

        // tabbar. Make sure no tab is under the cursor
        if( auto tabBar = qobject_cast<QTabBar*>( widget ) )
        { return tabBar->tabAt( position ) == -1; }

        /*
        check groupboxes
        prevent drag if unchecking grouboxes
        */
        if( auto groupBox = qobject_cast<QGroupBox*>( widget ) )
        {
            // non checkable group boxes are always ok
            if( !groupBox->isCheckable() ) return true;

            // gather options to retrieve checkbox subcontrol rect
            QStyleOptionGroupBox opt;
            opt.initFrom( groupBox );
            if( groupBox->isFlat() ) opt.features |= QStyleOptionFrame::Flat;
            opt.lineWidth = 1;
            opt.midLineWidth = 0;
            opt.text = groupBox->title();
            opt.textAlignment = groupBox->alignment();
            opt.subControls = (QStyle::SC_GroupBoxFrame | QStyle::SC_GroupBoxCheckBox);
            if (!groupBox->title().isEmpty()) opt.subControls |= QStyle::SC_GroupBoxLabel;

            opt.state |= (groupBox->isChecked() ? QStyle::State_On : QStyle::State_Off);

            // check against groupbox checkbox
            if( groupBox->style()->subControlRect(QStyle::CC_GroupBox, &opt, QStyle::SC_GroupBoxCheckBox, groupBox ).contains( position ) )
            { return false; }

            // check against groupbox label
            if( !groupBox->title().isEmpty() && groupBox->style()->subControlRect(QStyle::CC_GroupBox, &opt, QStyle::SC_GroupBoxLabel, groupBox ).contains( position ) )
            { return false; }

            return true;

        }

        // labels
        if( auto label = qobject_cast<QLabel*>( widget ) )
        { if( label->textInteractionFlags().testFlag( Qt::TextSelectableByMouse ) ) return false; }

        // abstract item views
        QAbstractItemView* itemView( nullptr );
        if(
            ( itemView = qobject_cast<QListView*>( widget->parentWidget() ) ) ||
            ( itemView = qobject_cast<QTreeView*>( widget->parentWidget() ) ) )
        {
            if( widget == itemView->viewport() )
            {
                // QListView
                if( itemView->frameShape() != QFrame::NoFrame ) return false;
                else if(
                    itemView->selectionMode() != QAbstractItemView::NoSelection &&
                    itemView->selectionMode() != QAbstractItemView::SingleSelection &&
                    itemView->model() && itemView->model()->rowCount() ) return false;
                else if( itemView->model() && itemView->indexAt( position ).isValid() ) return false;
            }

        } else if( ( itemView = qobject_cast<QAbstractItemView*>( widget->parentWidget() ) ) ) {


            if( widget == itemView->viewport() )
            {
                // QAbstractItemView
                if( itemView->frameShape() != QFrame::NoFrame ) return false;
                else if( itemView->indexAt( position ).isValid() ) return false;
            }

        } else if( auto graphicsView =  qobject_cast<QGraphicsView*>( widget->parentWidget() ) )  {

            if( widget == graphicsView->viewport() )
            {
                // QGraphicsView
                if( graphicsView->frameShape() != QFrame::NoFrame ) return false;
                else if( graphicsView->dragMode() != QGraphicsView::NoDrag ) return false;
                else if( graphicsView->itemAt( position ) ) return false;
            }

        }

        return true;

    }

    //____________________________________________________________
    void WindowManager::resetDrag()
    {

        _target.clear();
        #if BREEZE_HAVE_QTQUICK
        _quickTarget.clear();
        #endif
        if( _dragTimer.isActive() ) _dragTimer.stop();
        _dragPoint = QPoint();
        _globalDragPoint = QPoint();
        _dragAboutToStart = false;
        _dragInProgress = false;

    }

    //____________________________________________________________
    void WindowManager::startDrag( QWindow* window )
    {

        if( !( enabled() && window ) ) return;
        if( QWidget::mouseGrabber() ) return;

#if BREEZE_HAVE_QTQUICK
        if( _quickTarget )
        {
            if (QQuickWindow *qw = qobject_cast<QQuickWindow *>(window)) {
                QWindow *renderWindow = QQuickRenderControl::renderWindowFor(qw);
                if( renderWindow ) {
                    _dragInProgress = renderWindow->startSystemMove();
                } else {
                    _dragInProgress = window->startSystemMove();
                }
            }
        } else
#endif
        {
            _dragInProgress = window->startSystemMove();
        }

    }

    //____________________________________________________________
    bool WindowManager::isDockWidgetTitle( const QWidget* widget ) const
    {

        if( !widget ) return false;
        if( auto dockWidget = qobject_cast<const QDockWidget*>( widget->parent() ) )
        {

            return widget == dockWidget->titleBarWidget();

        } else return false;

    }

}
