//
//  Lol Engine
//
//  Copyright © 2010—2019 Sam Hocevar <sam@hocevar.net>
//
//  Lol Engine is free software. It comes without any warranty, to
//  the extent permitted by applicable law. You can redistribute it
//  and/or modify it under the terms of the Do What the Fuck You Want
//  to Public License, Version 2, as published by the WTFPL Task Force.
//  See http://www.wtfpl.net/ for more details.
//

#include <lol/engine-internal.h>

namespace lol
{

/*
 * Emitter implementation class
 */

class EmitterData
{
    friend class Emitter;

    static const int MAX_PARTICLES = 1000;

private:
    TileSet *tileset;
    vec3 gravity;
    int particles[MAX_PARTICLES];
    vec3 positions[MAX_PARTICLES];
    vec3 velocities[MAX_PARTICLES];
    int nparticles;
};

/*
 * Public Emitter class
 */

Emitter::Emitter(TileSet *tileset, vec3 gravity)
  : data(new EmitterData())
{
    data->tileset = tileset;
    data->gravity = gravity;
    data->nparticles = 0;
}

void Emitter::tick_game(float seconds)
{
    for (int i = 0; i < data->nparticles; i++)
    {
        vec3 oldvelocity = data->velocities[i];
        data->velocities[i] += seconds * data->gravity;
        data->positions[i] += seconds * 0.5f
                                      * (oldvelocity + data->velocities[i]);
        if (data->positions[i].y < -100)
        {
            data->particles[i] = data->particles[data->nparticles - 1];
            data->positions[i] = data->positions[data->nparticles - 1];
            data->velocities[i] = data->velocities[data->nparticles - 1];
            data->nparticles--;
        }
    }

    entity::tick_game(seconds);
}

void Emitter::tick_draw(float seconds, Scene &scene)
{
    entity::tick_draw(seconds, scene);

    for (int i = 0; i < data->nparticles; i++)
        scene.AddTile(data->tileset, data->particles[i],
                      data->positions[i], vec2(1.0f), 0.0f);
}

void Emitter::AddParticle(int id, vec3 pos, vec3 vel)
{
    if (data->nparticles >= EmitterData::MAX_PARTICLES)
        return;

    data->particles[data->nparticles] = id;
    data->positions[data->nparticles] = pos;
    data->velocities[data->nparticles] = vel;
    data->nparticles++;
}

Emitter::~Emitter()
{
    delete data;
}

} /* namespace lol */