///                 _   _      _
/// __  ____ _ _ __| |_(_) ___| | ___
/// \ \/ / _` | '__| __| |/ __| |/ _ \
///  >  < (_| | |  | |_| | (__| |  __/
/// /_/\_\__,_|_|   \__|_|\___|_|\___|
///
/// Copyright (c) 1997 - Ognjen 'xolatile' Milan Robovic
///
/// xolatile@chud.cyou - xarticle - Forgiving, kind and nice general static 3D particle system.
///
/// This program is free software, free as in freedom and as in free beer, you can redistribute it and/or modify it under the terms of the GNU
/// General Public License as published by the Free Software Foundation, either version 3 of the License, or any later version if you wish...
///
/// This program is distributed in the hope that it will be useful, but it is probably not, and without any warranty, without even the implied
/// warranty of merchantability or fitness for a particular purpose, because it is pointless. Please see the GNU (Geenoo) General Public License
/// for more details, if you dare, it is a lot of text that nobody wants to read...

typedef struct {
	natural         count;
	natural         limit;
	natural       * sprite;
	real      * life;
	natural       * colour_in;
	natural       * colour_out;
	vector_3 * * position;
	vector_3 * * target;
	vector_3 * * speed;
} particle_structure;

static particle_structure * particle_initialize (natural limit) {
	particle_structure * particle = allocate (sizeof (* particle));

	particle->limit = limit;

	particle->sprite     = allocate (limit * sizeof (* particle->sprite));
	particle->life       = allocate (limit * sizeof (* particle->life));
	particle->colour_in  = allocate (limit * sizeof (* particle->colour_in));
	particle->colour_out = allocate (limit * sizeof (* particle->colour_out));
	particle->position   = allocate (limit * sizeof (* particle->position));
	particle->target     = allocate (limit * sizeof (* particle->target));
	particle->speed      = allocate (limit * sizeof (* particle->speed));

	for (natural index = 0; index < limit; ++index) {
		particle->life [index] = 0.0f;

		particle->position [index] = allocate (sizeof (* * particle->position));
		particle->target   [index] = allocate (sizeof (* * particle->target));
		particle->speed    [index] = allocate (sizeof (* * particle->speed));

		vector_3_nullify (particle->position [index]);
		vector_3_nullify (particle->target   [index]);
		vector_3_nullify (particle->speed    [index]);
	}

	return (particle);
}

static particle_structure * particle_deinitialize (particle_structure * particle) {
	for (natural index = 0; index < particle->count; ++index) {
		particle->position [index] = deallocate (particle->position [index]);
		particle->target   [index] = deallocate (particle->target   [index]);
		particle->speed    [index] = deallocate (particle->speed    [index]);
	}

	particle->sprite     = deallocate (particle->sprite);
	particle->life       = deallocate (particle->life);
	particle->colour_in  = deallocate (particle->colour_in);
	particle->colour_out = deallocate (particle->colour_out);
	particle->position   = deallocate (particle->position);
	particle->target     = deallocate (particle->target);
	particle->speed      = deallocate (particle->speed);

	return (deallocate (particle));
}

static procedure particle_append (particle_structure * particle, natural sprite, real life, natural colour_in, natural colour_out, vector_3 * position,
                             vector_3 * target, vector_3 * speed) {
	if (particle->count + 1 >= particle->limit) return;

	++particle->count;

	natural current = particle->count - 1;

	particle->sprite     [current] = sprite;
	particle->life       [current] = life;
	particle->colour_in  [current] = colour_in;
	particle->colour_out [current] = colour_out;

	vector_3_copy (particle->position [current], position);
	vector_3_copy (particle->target   [current], target);
	vector_3_copy (particle->speed    [current], speed);
}

static procedure particle_switch (particle_structure * particle, natural this, natural with) {
	exchange_natural     (& particle->sprite     [this], & particle->sprite     [with]);
	exchange_real    (& particle->life       [this], & particle->life       [with]);
	exchange_natural     (& particle->colour_in  [this], & particle->colour_in  [with]);
	exchange_natural     (& particle->colour_out [this], & particle->colour_out [with]);
	vector_3_exchange (  particle->position   [this],   particle->position   [with]);
	vector_3_exchange (  particle->target     [this],   particle->target     [with]);
	vector_3_exchange (  particle->speed      [this],   particle->speed      [with]);
}

static procedure particle_remove (particle_structure * particle, natural index) {
	if (index >= particle->count) return;

	particle_switch (particle, index, particle->count - 1);

	--particle->count;
}

static procedure particle_effect_splash (particle_structure * particle, natural sprite, real life, natural colour_in, natural colour_out,
                                    vector_3 * position, natural ray_count, real ray_force, real ray_error) {
	for (natural ray = 0; ray < ray_count; ++ray) {
		vector_3 target = {
			//~position->x + random_real (- ray_force, + ray_force),
			//~position->y + random_real (- ray_force, + ray_force),
			//~position->z + random_real (- ray_force, + ray_force) + random_real (- ray_error, + ray_error)
			//~random_real (- ray_force, + ray_force),
			//~random_real (- ray_force, + ray_force),
			//~random_real (- ray_force, + ray_force)
			 0.0f, 0.0f, 0.0f
		};

		vector_3 speed = {
			random_real (- ray_force, + ray_force),
			random_real (- ray_force, + ray_force),
			random_real (- ray_force, + ray_force)
		};

		life += random_real (- 1.0f, + 1.0f);

		particle_append (particle, sprite, life, colour_in, colour_out, position, & target, & speed);
	}
}

static procedure particle_effect_evaporate (particle_structure * particle, natural sprite, real life, natural colour_in, natural colour_out,
                                       vector_3 * position, natural ray_count, real ray_force, real ray_error) {
	for (natural ray = 0; ray < ray_count; ++ray) {
		vector_3 target = {
			random_real (0.0f, + ray_force / 6.0f),
			random_real (0.0f, + ray_force / 1.0f),
			random_real (0.0f, + ray_force / 6.0f),
		};

		vector_3 speed = {
			random_real (- ray_force, + ray_force),
			random_real (- ray_force, + ray_force),
			random_real (- ray_force, + ray_force)
		};

		life += random_real (- 1.0f, + 1.0f);

		particle_append (particle, sprite, life, colour_in, colour_out, position, & target, & speed);
	}
}

static procedure particle_synchronize (particle_structure * particle, natural framerate) {
	for (natural index = 0; index < particle->count; ++index) {
		particle->life [index] -= 1.0f / (real) framerate;

		if (particle->life [index] < 0.0f) {
			particle_remove (particle, index);
		}

		vector_3_add (particle->position [index], particle->speed  [index]);
		vector_3_add (particle->speed    [index], particle->target [index]);
		//~vector_3_add (particle->position [index], particle->target [index]);
	}
}