/*

* Copyright (c) 2010 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

*

* This program is free software: you can redistribute it and/or modify

* it under the terms of the GNU Lesser General Public License as published by

* the Free Software Foundation, version 2.1 of the License.

*

* This program 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 Lesser General Public License for more details.

*

* You should have received a copy of the GNU Lesser General Public License

* along with this program.  If not,

* see "http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html/".

*

* Description:

*

*/

#include <QTimer>

#include <QTime>

#include <QPoint>

#include <QDebug>

#include "KineticHelper.h"

KineticHelper::KineticHelper(KineticScrollable* scrollable, qreal decel, int kineticTimeout) :

     m_scrollable(scrollable),

     m_decel(decel),

     m_kineticTimeout(kineticTimeout)

{

    m_kineticTimer = new QTimer(this);

    QObject::connect(m_kineticTimer, SIGNAL(timeout()), this, SLOT(kineticScroll()));

    m_kineticTimer->setSingleShot(false);

}

KineticHelper::~KineticHelper()

{

    delete m_kineticTimer;

}

bool KineticHelper::isScrolling()

{

    return m_kineticTimer->isActive();

}

void KineticHelper::startScrolling()

{

    m_initialSpeed = m_scrollable->getInitialSpeed() * 1000;

    m_initialPos = m_scrollable->getInitialPosition();

    if (m_kineticTimer->isActive()) {

        m_kineticTimer->stop();

    }

    m_kineticSteps = 0;

    m_kineticScrollTime = 0.0;

    m_kineticTimer->start(m_kineticTimeout);

    m_actualTime = QTime::currentTime();

    m_actualTime.start();

}

void KineticHelper::kineticScroll()

{

    if (++m_kineticSteps == 1) return;

    qreal decelX = m_initialSpeed.x() > 0 ? (-1) * m_decel : m_decel;

    qreal decelY = m_initialSpeed.y() > 0 ? (-1) * m_decel : m_decel;

    qreal dx = 0;

    qreal dy = 0;

    qreal vx = 0;

    qreal vy = 0;

    int t = m_actualTime.elapsed();

    m_kineticScrollTime += (((qreal)t) / 1000);

    if (m_initialSpeed.x()) {

        vx = m_initialSpeed.x() + decelX * m_kineticScrollTime;

        if (vx * m_initialSpeed.x() < 0) {

            dx = 0;

            vx = 0;

        }

        else {

            dx = m_kineticScrollTime * m_initialSpeed.x() +

                0.5 * decelX * m_kineticScrollTime * m_kineticScrollTime;

        }

    }

    if (m_initialSpeed.y()) {

        vy = m_initialSpeed.y() + decelY * m_kineticScrollTime;

        if (vy * m_initialSpeed.y() < 0) {

            dy = 0;

            vy = 0;

        }

        else {

            dy = m_kineticScrollTime * m_initialSpeed.y() +

                 0.5 * decelY * m_kineticScrollTime * m_kineticScrollTime;

        }

    }

    QPoint scrollPos = m_scrollable->getScrollPosition();

    QPoint distPos = m_initialPos + QPointF(dx, dy).toPoint();

    if (vx != 0 || vy != 0) {

        m_scrollable->scrollTo(distPos);

    }

    if ((vx == 0 && vy == 0) || scrollPos == m_scrollable->getScrollPosition()) {

        stopScrolling();

    }

}

void KineticHelper::stopScrolling()

{

    if (m_kineticTimer && m_kineticTimer->isActive()) {

        m_kineticTimer->stop();

        m_initialSpeed.setX(0.0);

        m_initialSpeed.setY(0.0);

    }

    m_kineticSteps = 0;

}