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#include "turbulenceaffector.h"
#include "particle.h"
#include <cmath>
#include <cstdlib>
#include <QDebug>
QT_BEGIN_NAMESPACE

TurbulenceAffector::TurbulenceAffector(QSGItem *parent) :
    ParticleAffector(parent),
    m_strength(10), m_lastT(0), m_frequency(64), m_gridSize(10), m_field(0), m_inited(false)
{
    //TODO: Update grid on size change
}

TurbulenceAffector::~TurbulenceAffector()
{
    if (m_field) {
        for(int i=0; i<m_gridSize; i++)
            free(m_field[i]);
        free(m_field);
    }
}

static qreal magnitude(qreal x, qreal y)
{
    return sqrt(x*x + y*y);
}

void TurbulenceAffector::setSize(int arg)
{
    if (m_gridSize != arg) {
        if(m_field){ //deallocate and then reallocate grid
            for(int i=0; i<m_gridSize; i++)
                free(m_field[i]);
            free(m_field);
            m_system = 0;
        }
        m_gridSize = arg;
        emit sizeChanged(arg);
    }
}

void TurbulenceAffector::ensureInit()
{
    if(m_inited)
        return;
    m_inited = true;
    m_field = (QPointF**)malloc(m_gridSize * sizeof(QPointF*));
    for(int i=0; i<m_gridSize; i++)
        m_field[i]  = (QPointF*)malloc(m_gridSize * sizeof(QPointF));
    for(int i=0; i<m_gridSize; i++)
        for(int j=0; j<m_gridSize; j++)
            m_field[i][j] = QPointF();
    m_spacing = QPointF(width()/m_gridSize, height()/m_gridSize);
    m_magSum = magnitude(m_spacing.x(), m_spacing.y())*2;
}

void TurbulenceAffector::mapUpdate()
{
    QPoint pos(rand() % m_gridSize, rand() % m_gridSize);
    QPointF vector(m_strength  - (((qreal)rand() / RAND_MAX) * m_strength*2),
                   m_strength  - (((qreal)rand() / RAND_MAX) * m_strength*2));
    for(int i = 0; i < m_gridSize; i++){
        for(int j = 0; j < m_gridSize; j++){
            qreal dist = magnitude(i-pos.x(), j-pos.y());
            m_field[i][j] += vector/(dist + 1);
            if(magnitude(m_field[i][j].x(), m_field[i][j].y()) > m_strength){
                //Speed limit
                qreal theta = atan2(m_field[i][j].y(), m_field[i][j].x());
                m_field[i][j].setX(m_strength * cos(theta));
                m_field[i][j].setY(m_strength * sin(theta));
            }
        }
    }
}


void TurbulenceAffector::affectSystem(qreal dt)
{
    if(!m_system || !m_active)
        return;
    ensureInit();
    qreal period = 1.0/m_frequency;
    qreal time = m_system->m_timeInt / 1000.0;
    while( m_lastT < time ){
        mapUpdate();
        m_lastT += period;
    }

    foreach(ParticleData *d, m_system->m_data){
        if(!d || !activeGroup(d->group))
            return;
        qreal fx = 0.0;
        qreal fy = 0.0;
        QPointF pos = QPointF(d->curX() - x(), d->curY() - y());//TODO: Offset
        QPointF nodePos = QPointF(pos.x() / m_spacing.x(), pos.y() / m_spacing.y());
        QSet<QPair<int, int> > nodes;
        nodes << qMakePair((int)ceil(nodePos.x()), (int)ceil(nodePos.y()));
        nodes << qMakePair((int)ceil(nodePos.x()), (int)floor(nodePos.y()));
        nodes << qMakePair((int)floor(nodePos.x()), (int)ceil(nodePos.y()));
        nodes << qMakePair((int)floor(nodePos.x()), (int)floor(nodePos.y()));
        typedef QPair<int, int> intPair;
        foreach(const intPair &p, nodes){
            if(!QRect(0,0,m_gridSize-1,m_gridSize-1).contains(QPoint(p.first, p.second)))
                continue;
            qreal dist = magnitude(pos.x() - p.first*m_spacing.x(), pos.y() - p.second*m_spacing.y());//TODO: Mathematically valid
            fx += m_field[p.first][p.second].x() * ((m_magSum - dist)/m_magSum);//Proportionally weight nodes
            fy += m_field[p.first][p.second].y() * ((m_magSum - dist)/m_magSum);
        }
        if(fx || fy){
            d->setInstantaneousSX(d->curSX()+ fx * dt);
            d->setInstantaneousSY(d->curSY()+ fy * dt);
            m_system->m_needsReset << d;
        }
    }
}

QT_END_NAMESPACE