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#include "qsgpointattractor_p.h"
#include <cmath>
#include <QDebug>
QT_BEGIN_NAMESPACE
QSGPointAttractorAffector::QSGPointAttractorAffector(QSGItem *parent) :
    QSGParticleAffector(parent), m_strength(0.0), m_x(0), m_y(0)
  , m_physics(Velocity), m_proportionalToDistance(Linear)
{
}

bool QSGPointAttractorAffector::affectParticle(QSGParticleData *d, qreal dt)
{
    if (m_strength == 0.0)
        return false;
    qreal dx = m_y - d->curX();
    qreal dy = m_x - d->curY();
    qreal r = sqrt((dx*dx) + (dy*dy));
    qreal theta = atan2(dy,dx);
    qreal ds = 0;
    switch (m_proportionalToDistance){
    case Quadratic:
        ds = (m_strength / qMax<qreal>(1.,r*r)) * dt;
        break;
    case Linear://also default
    default:
        ds = (m_strength / qMax<qreal>(1.,r)) * dt;
    }
    dx = ds * cos(theta);
    dy = ds * sin(theta);
    switch (m_physics){
    case Position:
        d->x = (d->x + dx);
        d->y = (d->y + dy);
        break;
    case Acceleration:
        d->setInstantaneousAX(d->ax + dx);
        d->setInstantaneousAY(d->ay + dy);
        break;
    case Velocity: //also default
    default:
        d->setInstantaneousSX(d->sx + dx);
        d->setInstantaneousSY(d->sy + dy);
    }

    return true;
}
QT_END_NAMESPACE