/* === This file is part of Tomahawk Player - <http://tomahawk-player.org> ===
 *
 *   Copyright 2010-2011, Leo Franchi <lfranchi@kde.org>
 *
 *   Tomahawk 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 3 of the License, or
 *   (at your option) any later version.
 *
 *   Tomahawk 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 Tomahawk. If not, see <http://www.gnu.org/licenses/>.
 */

#include "WidgetDragFilter.h"

#include "utils/Logger.h"

#include <QMouseEvent>
#include <QApplication>
#include <QMenuBar>

WidgetDragFilter::WidgetDragFilter( QObject* parent )
    : QObject( parent )
    , m_dragStarted( false )
{
    Q_ASSERT( parent->isWidgetType() );
    m_target = QPointer<QWidget>(static_cast<QWidget*>(parent));
    m_target.data()->installEventFilter( this );
}


bool
WidgetDragFilter::eventFilter( QObject* obj, QEvent* event )
{
    if ( m_target.isNull() || m_target.data() != obj )
        return false;

    if ( event->type() == QEvent::MouseButtonPress )
    {
        QMouseEvent *mouseEvent = static_cast<QMouseEvent*>( event );
        if ( !canDrag( obj, mouseEvent ) )
            return false;
        if ( !( mouseEvent->modifiers() == Qt::NoModifier && mouseEvent->button() == Qt::LeftButton ) )
            return false;

        m_dragPoint = mouseEvent->pos();
        m_dragStarted = true;
        return false;
    }
    else if ( event->type() == QEvent::MouseMove )
    {
        if ( !m_dragStarted )
            return false;

        QMouseEvent* e = static_cast<QMouseEvent* >(event);
        if ( !canDrag( obj, e ) )
        {
            m_dragStarted = false;
            return false;
        }

        if ( e->buttons().testFlag( Qt::LeftButton ) )
        {
            m_target.data()->window()->move( m_target.data()->window()->pos() + ( e->pos() - m_dragPoint ) );
            return true;
        }
    }
    else if ( event->type() == QEvent::MouseButtonRelease )
        m_dragStarted = false;

    return false;
}


/**
 * Make sure we can really drag this widget. Checks inspired by Oxygen's oxygenwindowmanager.cpp
 */
bool
WidgetDragFilter::canDrag( QObject* obj, QMouseEvent* ev ) const
{
    if ( !obj->isWidgetType() )
        return false;

    QWidget* w = static_cast< QWidget* >( obj );

    if ( QWidget::mouseGrabber() )
        return false;

    if ( w->cursor().shape() != Qt::ArrowCursor )
        return false;

    // Now we check various things about the child position and mouse
    QPoint position( ev->pos() );
    QWidget* child = w->childAt( position );

    if ( child && child->cursor().shape() != Qt::ArrowCursor )
        return false;

    // Don't want to drag menubars when selecting an action
    if ( QMenuBar* menuBar = qobject_cast<QMenuBar*>( w ) )
    {
        // 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 ( QAction* action = menuBar->actionAt( position ) )
        {
            if ( action->isSeparator() )
                return true;
            if ( action->isEnabled() )
                return false;
        }
    }

    return true;
}