#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include "world.hh"
#include "body.hh"
#include "view.hh"
#include <stdlib.h>

World::World()
    : _static_friction(0.2), _dynamic_friction(0.2),
      _angular_friction(0.3), _angular_friction_2(1)
{
}

void
World::set_static_friction(double d)
{
    _static_friction = d;
}

void
World::set_dynamic_friction(double d)
{
    _dynamic_friction = d;
}

void
World::set_angular_friction(double d)
{
    if (d < 0)
	d = 0;
    _angular_friction = d;
}

void
World::add(Body *b)
{
    _bodies.push_back(b);
    b->embody(this);
    if (b->movable())
	_moving_bodies.push_back(b);
    if (b->z_plane() > 0)
	_collidable_bodies.push_back(b);
}

void
World::remove(Body *b)
{
    for (int i = 0; i < _moving_bodies.size(); i++)
	if (_moving_bodies[i] == b) {
	    _moving_bodies[i] = _moving_bodies.back();
	    _moving_bodies.pop_back();
	    break;
	}
    for (int i = 0; i < _collidable_bodies.size(); i++)
	if (_collidable_bodies[i] == b) {
	    _collidable_bodies[i] = _collidable_bodies.back();
	    _collidable_bodies.pop_back();
	    break;
	}
    for (int i = 0; i < _bodies.size(); i++)
	if (_bodies[i] == b) {
	    _bodies[i] = _bodies.back();
	    _bodies.pop_back();
	    break;
	}
}

extern "C" {
static int
body_qsorter(const void *thunk1, const void *thunk2)
{
    const Body **b1 = (const Body **)thunk1;
    const Body **b2 = (const Body **)thunk2;
    return (*b1)->move_phase() - (*b2)->move_phase();
}
}

void
World::reset()
{
    for (int i = 0; i < _bodies.size(); i++)
	_bodies[i]->reset();
    if (_bodies.size())
	qsort(&_bodies[0], _bodies.size(), sizeof(Body *), body_qsorter);
}

void
World::trail_snapshot()
{
    for (int i = 0; i < _bodies.size(); i++)
	_bodies[i]->trail_snapshot();
}

void
World::random_place(bool do_movable, bool do_stationary, View *view)
{
    Point ll = view->lower_left();
    Point ur = view->upper_right();
    Point delta = ur - ll;
  
    for (int i = 0; i < _bodies.size(); i++)
	if (_bodies[i]->movable() ? do_movable : do_stationary) {
	    Point p = ll;
	    p.x += ((double)rand() / RAND_MAX) * delta.x;
	    p.y += ((double)rand() / RAND_MAX) * delta.y;
	    double rotation = ((double)rand() / RAND_MAX) * 2*M_PI;
	    _bodies[i]->place(p, rotation);
	}

    reset();
}

void
World::draw(View *v) const
{
    v->clear();
    for (int i = 0; i < _bodies.size(); i++)
	_bodies[i]->draw(v);
    v->expose();
}

#define MOVE_TIME_QUANTUM 0.1
void
World::move() const
{
    for (int i = 0; i < _bodies.size(); i++)
	_bodies[i]->move(MOVE_TIME_QUANTUM);
}

void
World::check_collisions() const
{
    int cs = _collidable_bodies.size();
    if (cs) {
	Body * const *cb = _collidable_bodies.begin();
	for (int i = 0; i < cs - 1; i++)
	    for (int j = i + 1; j < cs; j++)
		if (cb[i]->might_collide(cb[j]))
		    cb[i]->collide(cb[j]);
    }
}