//  $Id: physics.cpp 839 2006-10-24 00:01:56Z hiker $
//
//  SuperTuxKart - a fun racing game with go-kart
//  Copyright (C) 2006 Joerg Henrichs
//
//  This program is free software; 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 (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty ofati
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

#include "physics/physics.hpp"

#include "config/user_config.hpp"
#include "network/race_state.hpp"
#include "physics/btKart.hpp"
#include "physics/btUprightConstraint.hpp"
#include "tracks/track.hpp"

// ----------------------------------------------------------------------------
/** Initialise physics.
 *  Create the bullet dynamics world.
 */
Physics::Physics() : btSequentialImpulseConstraintSolver()
{
    m_collision_conf = new btDefaultCollisionConfiguration();
    m_dispatcher     = new btCollisionDispatcher(m_collision_conf);
}   // Physics

//-----------------------------------------------------------------------------
/** The actual initialisation of the physics, which is called after the track
 *  model is loaded. This allows the physics to use the actual track dimension
 *  for the axis sweep.
 */
void Physics::init(const Vec3 &world_min, const Vec3 &world_max)
{
    m_axis_sweep     = new btAxisSweep3(world_min, world_max);
    m_dynamics_world = new btDiscreteDynamicsWorld(m_dispatcher, 
                                                    m_axis_sweep, 
                                                   this,
                                                   m_collision_conf);
    m_dynamics_world->setGravity(btVector3(0.0f, 0.0f, 
                                           -RaceManager::getTrack()->getGravity()));
#ifdef HAVE_GLUT
    if(UserConfigParams::m_bullet_debug)
      {
        m_debug_drawer = new GLDebugDrawer();
        m_debug_drawer->setDebugMode(btIDebugDraw::DBG_DrawWireframe);
        m_dynamics_world->setDebugDrawer(m_debug_drawer);
    }
#endif
}   // init

//-----------------------------------------------------------------------------
Physics::~Physics()
{
#ifdef HAVE_GLUT
    if(UserConfigParams::m_bullet_debug) delete m_debug_drawer;
#endif
    delete m_dynamics_world;
    delete m_axis_sweep;
    delete m_dispatcher;
    delete m_collision_conf;
}   // ~Physics

// -----------------------------------------------------------------------------
/** Adds a kart to the physics engine.
 *  This adds the rigid body, the vehicle, and the upright constraint.
 *  \param kart The kart to add.
 *  \param vehicle The raycast vehicle object.
 */
void Physics::addKart(const Kart *kart)
{
    m_dynamics_world->addRigidBody(kart->getBody());
    m_dynamics_world->addVehicle(kart->getVehicle());
    m_dynamics_world->addConstraint(kart->getUprightConstraint());
}   // addKart

//-----------------------------------------------------------------------------
/** Removes a kart from the physics engine. This is used when rescuing a kart
 *  (and during cleanup).
 *  \param kart The kart to remove.
 */
void Physics::removeKart(const Kart *kart)
{
    m_dynamics_world->removeRigidBody(kart->getBody());
    m_dynamics_world->removeVehicle(kart->getVehicle());
    m_dynamics_world->removeConstraint(kart->getUprightConstraint());
}   // removeKart

//-----------------------------------------------------------------------------
/** Updates the physics simulation and handles all collisions.
 *  \param dt Time step.
 */
void Physics::update(float dt)
{
    // Bullet can report the same collision more than once (up to 4
    // contact points per collision. Additionally, more than one internal
    // substep might be taken, resulting in potentially even more
    // duplicates. To handle this, all collisions (i.e. pair of objects)
    // are stored in a vector, but only one entry per collision pair
    // of objects.
    m_all_collisions.clear();

    // Maximum of three substeps. This will work for framerate down to
    // 20 FPS (bullet default frequency is 60 HZ).
    m_dynamics_world->stepSimulation(dt, 3);

    // Now handle the actual collision. Note: rockets can not be removed
    // inside of this loop, since the same rocket might hit more than one
    // other object. So, only a flag is set in the rockets, the actual
    // clean up is then done later in the projectile manager.
    std::vector<CollisionPair>::iterator p;
    for(p=m_all_collisions.begin(); p!=m_all_collisions.end(); ++p)
    {
        if(p->a->is(UserPointer::UP_KART)) {          // kart-kart collision
            Kart *a=p->a->getPointerKart();
            Kart *b=p->b->getPointerKart();
            race_state->addCollision(a->getWorldKartId(),
                                     b->getWorldKartId());
            KartKartCollision(p->a->getPointerKart(), p->b->getPointerKart());
        }  // if kart-kart collision
        else  // now the first object must be a projectile
        {
            if(p->b->is(UserPointer::UP_TRACK))       // must be projectile hit track
            {
                p->a->getPointerFlyable()->hitTrack();
            }
            else if(p->b->is(UserPointer::UP_PHYSICAL_OBJECT))
            {
                p->a->getPointerFlyable()->hit(NULL, p->b->getPointerPhysicalObject());

            }
            else if(p->b->is(UserPointer::UP_KART))   // projectile hit kart
            {
                p->a->getPointerFlyable()->hit(p->b->getPointerKart());
            }
            else                                     // projectile hits projectile
            {      
                p->a->getPointerFlyable()->hit(NULL);
                p->b->getPointerFlyable()->hit(NULL);
            }
        }
    }  // for all p in m_all_collisions
}   // update

//-----------------------------------------------------------------------------
/** Handles the special case of two karts colliding with each other, which means
 *  that bombs must be passed on. If both karts have a bomb, they'll explode
 *  immediately. This function is called from physics::update on the server
 *  (and if no networking is used), and from race_state on the client to replay
 *  what happened on the server.
 *  \param kartA First kart involved in the collision.
 *  \param kartB Second kart involved in the collision.
 */
void Physics::KartKartCollision(Kart *kartA, Kart *kartB)
{
    kartA->crashed(kartB);   // will play crash sound for player karts
    kartB->crashed(kartA);
    Attachment *attachmentA=kartA->getAttachment();
    Attachment *attachmentB=kartB->getAttachment();

    if(attachmentA->getType()==ATTACH_BOMB)
    {
        // If both karts have a bomb, explode them immediately:
        if(attachmentB->getType()==ATTACH_BOMB)
        {
            attachmentA->setTimeLeft(0.0f);
            attachmentB->setTimeLeft(0.0f);
        }
        else  // only A has a bomb, move it to B (unless it was from B)
        {
            if(attachmentA->getPreviousOwner()!=kartB) 
            {
                attachmentA->moveBombFromTo(kartA, kartB);
            }
        }
    }
    else if(attachmentB->getType()==ATTACH_BOMB &&
        attachmentB->getPreviousOwner()!=kartA) 
    {
        attachmentB->moveBombFromTo(kartB, kartA);
    }
}   // KartKartCollision

//-----------------------------------------------------------------------------
/** This function is called at each internal bullet timestep. It is used
 *  here to do the collision handling: using the contact manifolds after a
 *  physics time step might miss some collisions (when more than one internal
 *  time step was done, and the collision is added and removed). So this
 *  function stores all collisions in a list, which is then handled after the
 *  actual physics timestep. This list only stores a collision, if it's not
 *  already in the list, so a collisions which is reported more than once is
 *  nevertheless only handled once.
 *  Parameters: see bullet documentation for details.
 */
btScalar Physics::solveGroup(btCollisionObject** bodies, int numBodies,
                             btPersistentManifold** manifold,int numManifolds,
                             btTypedConstraint** constraints,int numConstraints,
                             const btContactSolverInfo& info, 
                             btIDebugDraw* debugDrawer, btStackAlloc* stackAlloc,
                             btDispatcher* dispatcher) {
    btScalar returnValue=
        btSequentialImpulseConstraintSolver::solveGroup(bodies, numBodies, manifold, 
                                                        numManifolds, constraints, 
                                                        numConstraints, info, 
                                                        debugDrawer, stackAlloc,
                                                        dispatcher);
    int currentNumManifolds = m_dispatcher->getNumManifolds();
    // We can't explode a rocket in a loop, since a rocket might collide with 
    // more than one object, and/or more than once with each object (if there 
    // is more than one collision point). So keep a list of rockets that will
    // be exploded after the collisions
    std::vector<Moveable*> rocketsToExplode;
    for(int i=0; i<currentNumManifolds; i++)
    {               
        btPersistentManifold* contactManifold = m_dynamics_world->getDispatcher()->getManifoldByIndexInternal(i);

        btCollisionObject* objA = static_cast<btCollisionObject*>(contactManifold->getBody0());
        btCollisionObject* objB = static_cast<btCollisionObject*>(contactManifold->getBody1());
        
        int numContacts = contactManifold->getNumContacts();
        if(!numContacts) continue;   // no real collision

        UserPointer *upA        = (UserPointer*)(objA->getUserPointer());
        UserPointer *upB        = (UserPointer*)(objB->getUserPointer());

        // FIXME: Must be a moving physics object
        // FIXME: A rocket should explode here!

        if(!upA || !upB) continue;
        // 1) object A is a track
        // =======================
        if(upA->is(UserPointer::UP_TRACK)) 
        { 
            if(upB->is(UserPointer::UP_FLYABLE))   // 1.1 projectile hits track
                m_all_collisions.push_back(upB, upA);
            else if(upB->is(UserPointer::UP_KART))
            {
                Kart *kart=upB->getPointerKart();
                race_state->addCollision(kart->getWorldKartId());
                kart->crashed(NULL);
            }
        }
        // 2) object a is a kart
        // =====================
        else if(upA->is(UserPointer::UP_KART))
        {
            if(upB->is(UserPointer::UP_TRACK))
            {
                Kart *kart = upA->getPointerKart();
                race_state->addCollision(kart->getWorldKartId());
                kart->crashed(NULL);   // Kart hit track
            }
            else if(upB->is(UserPointer::UP_FLYABLE))
                m_all_collisions.push_back(upB, upA);   // 2.1 projectile hits kart
            else if(upB->is(UserPointer::UP_KART))
                m_all_collisions.push_back(upA, upB);   // 2.2 kart hits kart
        }
        // 3) object is a projectile
        // =========================
        else if(upA->is(UserPointer::UP_FLYABLE))
        {
            if(upB->is(UserPointer::UP_TRACK          ) ||   // 3.1) projectile hits track
               upB->is(UserPointer::UP_FLYABLE        ) ||   // 3.2) projectile hits projectile
               upB->is(UserPointer::UP_PHYSICAL_OBJECT) ||   // 3.3) projectile hits projectile
               upB->is(UserPointer::UP_KART           )   )  // 3.4) projectile hits kart
            {
                m_all_collisions.push_back(upA, upB);
            }
        } 
        else if(upA->is(UserPointer::UP_PHYSICAL_OBJECT))
        {
            if(upB->is(UserPointer::UP_FLYABLE)) 
            {
                m_all_collisions.push_back(upB, upA);
            }
        }
        else assert("Unknown user pointer");            // 4) Should never happen
    }   // for i<numManifolds

    return returnValue;
}   // solveGroup

// -----------------------------------------------------------------------------
/** A debug draw function to show the track and all karts.                    */
void Physics::draw()
{
    int num_objects = m_dynamics_world->getNumCollisionObjects();
    for(int i=0; i<num_objects; i++)
    {
        btCollisionObject *obj = m_dynamics_world->getCollisionObjectArray()[i];
        btRigidBody* body = btRigidBody::upcast(obj);
        if(!body) continue;
        float m[16];
        btVector3 wireColor(1,0,0);
        btDefaultMotionState *myMotion = (btDefaultMotionState*)body->getMotionState();
        if(myMotion) 
        {
            myMotion->m_graphicsWorldTrans.getOpenGLMatrix(m);
            // Karts need culling GL_FRONT (not sure why), otherwise they appear to
            // rotate incorrectly due to incorrect culling
            UserPointer *up = (UserPointer*)body->getUserPointer();
            if(up->is(UserPointer::UP_KART))
                glCullFace(GL_FRONT);
            debugDraw(m, obj->getCollisionShape(), wireColor);
        }
    }  // for i
}   // draw

// -----------------------------------------------------------------------------
/** Helper function for Physics::draw(). It calls the shape drawer from
 *  bullet to render the actual object.
 *  \param m OpenGL matrix to apply.
 *  \param s Collision shape to drwa.
 *  \param color Colour to use.
 */
void Physics::debugDraw(float m[16], btCollisionShape *s, const btVector3 color)
{
#ifdef HAVE_GLUT
    m_shape_drawer.drawOpenGL(m, s, color, 0);
    //                               btIDebugDraw::DBG_DrawWireframe);
    //                               btIDebugDraw::DBG_DrawAabb);
#endif
}   // debugDraw

// -----------------------------------------------------------------------------

/* EOF */