/*

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

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* 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();

	qDebug() << "starting kinetic timer at " << m_initialPos << ", at " << m_actualTime;  

}

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);

    qDebug() << "kineticScroll(): elapsed: " << t << ", m_kineticSteps: " << m_kineticSteps << 

                ", m_kineticScrollTime: " << m_kineticScrollTime <<

                ", decelX: "<< decelX << ", decelY: " << decelY << ", m_initialSpeed: " << m_initialSpeed;

    if (m_initialSpeed.x()) {

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

        qDebug() << "vx: " << vx;

        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;

        qDebug() << "vy: " << vy;

        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) {

        qDebug() << "kineticScroll(): scroll from " << scrollPos << " to " << distPos;

        m_scrollable->scrollTo(distPos);

    }

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

        qDebug() << "kineticScroll(): stopping timer";

        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;

}