/*
* 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;
}