/*
 * Copyright 2012-2013 Tri-Edge AI <triedgeai@gmail.com>
 * Copyright 2014 Haiku, Inc. All rights reserved.
 *
 * Distributed under the terms of the MIT license.
 *
 * Authors:
 *              Tri-Edge AI
 *              John Scipione, jscipione@gmail.com
 */



#include "GravitySource.h"

#include "Particle.h"

#include <stdlib.h>


#define frand() ((float)rand() / (float)RAND_MAX)


GravitySource::GravitySource()
{
        x = 0.0f;
        y = 0.0f;
        z = 0.0f;
        r = 0.0f;

        vx = 0.0f;
        vy = 0.0f;
        vz = 0.0f;

        tx = frand() * 30.0f - 15.0f;
        ty = frand() * 30.0f - 15.0f;
        tz = frand() * 10.0f - 5.0f;
}


void
GravitySource::Tick()
{
        float dx = tx - x;
        float dy = ty - y;
        float dz = tz - z;

        float d = dx * dx + dy * dy + dz * dz;

        vx += dx * 0.003f;
        vy += dy * 0.003f;
        vz += dz * 0.003f;

        x += vx;
        y += vy;
        z += vz;

        vx *= 0.98f;
        vy *= 0.98f;
        vz *= 0.98f;

        if (dx * dx + dy * dy + dz * dz < 1.0f) {
                tx = frand() * 20.0f - 10.0f;
                ty = frand() * 20.0f - 10.0f;
                tz = frand() * 10.0f - 5.0f;
        }

        for (int32 i = 0; i < Particle::list->CountItems(); i++) {
                Particle* p = Particle::list->ItemAt(i);
                dx = x - p->x;
                dy = y - p->y;
                dz = z - p->z;

                d = dx * dx + dy * dy + dz * dz;

                p->vx += dx / d * 0.25f;
                p->vy += dy / d * 0.25f;
                p->vz += dz / d * 0.25f;
                p->vr += 1.0f / d;
        }
}