/*
   core/physics.cc
   This file is part of the Osirion project and is distributed under
   the terms and conditions of the GNU General Public License version 2
*/

#include <cassert>

#include "btBulletDynamicsCommon.h"
#include "BulletCollision/Gimpact/btGImpactCollisionAlgorithm.h"

#include "model/collisionmesh.h"
#include "core/physics.h"
#include "core/zone.h"

namespace core {

/* ---- Bullet collision callbacks --------------------------------- */

//extern ContactAddedCallback              gContactAddedCallback;

/*
 * 	see http://bulletphysics.org/mediawiki-1.5.8/index.php/Collision_Callbacks_and_Triggers
 */

#if (BT_BULLET_VERSION < 281)
// bullet 2.80 or older
bool bullet_contact_added_callback(btManifoldPoint &cp, const btCollisionObject *body0, int partId0, int index0, const btCollisionObject *body1, int partId1, int index1)
{
	Entity *entity0 = static_cast<Entity *>(body0->getUserPointer());
	Entity *entity1 = static_cast<Entity *>(body1->getUserPointer());

#else
// bullet 2.81 or newer
bool bullet_contact_added_callback(btManifoldPoint &cp, const btCollisionObjectWrapper *body0, int partId0, int index0, const btCollisionObjectWrapper *body1, int partId1, int index1)
{
	Entity *entity0 = static_cast<Entity *>(body0->getCollisionObject()->getUserPointer());
	Entity *entity1 = static_cast<Entity *>(body1->getCollisionObject()->getUserPointer());
#endif
	assert(entity0 && entity1);
	
	// FIXME there should probably be an entity flag indiciating wether or not it has a collision callback
	
	if ((entity0->type() == Entity::Dynamic) || (entity0->type() == Entity::Controlable) || (entity0->type() == Entity::Projectile)) {
		static_cast<EntityDynamic *>(entity0)->collision(entity1);
	}
	
	if ((entity1->type() == Entity::Dynamic) || (entity1->type() == Entity::Controlable) || (entity1->type() == Entity::Projectile)) {
		static_cast<EntityDynamic *>(entity1)->collision(entity0);
	}
	
	// the return value should be ignored by bullet.
	return true;
}

//bool bullet_contact_processed_callback(btManifoldPoint& cp,void* body0, void* body1);

//bool bullet_contact_destroyed_callback(void* userPersistentData);

/* ---- Bullet physics engine and algorithms ----------------------- */

btDefaultCollisionConfiguration *Physics::physics_configuration = 0;
btCollisionDispatcher *Physics::physics_dispatcher = 0;
btSequentialImpulseConstraintSolver *Physics::physics_solver = 0;

void Physics::init()
{
	con_print << "^BInitializing physics engine..." << std::endl;
	
	model::CollisionModel::init();

	physics_configuration = new btDefaultCollisionConfiguration();
	physics_dispatcher = new btCollisionDispatcher(physics_configuration);
	btGImpactCollisionAlgorithm::registerAlgorithm(physics_dispatcher);
	physics_solver = new btSequentialImpulseConstraintSolver;
	
	// set custom bullet callbacks
	gContactAddedCallback = bullet_contact_added_callback;
}

void Physics::done()
{
	con_print << "^BShutting down physics engine..." << std::endl;
	
	model::CollisionModel::shutdown();
	
	delete physics_solver;
	delete physics_dispatcher;
	delete physics_configuration;
	
	physics_configuration = 0;
	physics_dispatcher = 0;
	physics_solver = 0;
}

void Physics::frame(const unsigned long elapsed)
{
	const float seconds = (float) elapsed / 1000.0f;
	
	for (core::Zone::Registry::iterator it = core::Zone::registry().begin(); it != core::Zone::registry().end(); it++) {
		(*it).second->physics()->stepSimulation(seconds, 8);
	}
}

} // namespace core