/********************************************************************************
* ReactPhysics3D physics library, http://code.google.com/p/reactphysics3d/      *
* Copyright (c) 2010 Daniel Chappuis                                            *
*********************************************************************************
*                                                                               *
* Permission is hereby granted, free of charge, to any person obtaining a copy  *
* of this software and associated documentation files (the "Software"), to deal *
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* copies of the Software, and to permit persons to whom the Software is         *
* furnished to do so, subject to the following conditions:                      *
*                                                                               *
* The above copyright notice and this permission notice shall be included in    *
* all copies or substantial portions of the Software.                           *
*                                                                               *
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR    *
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* THE SOFTWARE.                                                                 *
********************************************************************************/

#ifndef SATALGORITHM_H
#define SATALGORITHM_H

// Libraries
#include "NarrowPhaseAlgorithm.h"
#include "../constraint/Contact.h"
#include "../body/OBB.h"

// ReactPhysics3D namespace
namespace reactphysics3d {

/*  -------------------------------------------------------------------
    Class SATAlgorithm :
        This class implements a narrow-phase algorithm. This algorithm
        uses a separating axis theorem (SAT) to check if two bounding
        volumes collide or not. If the
        two bounding volumes collide we have to create a contact object
        to describe the collision contact. The idea is to check if there
        exists an axis where, if we project the two bounding volumes on
        this axis, the two projections are separated. If we find at
        least an axis where the projections of the two bounding volumes
        are separated then we know that the two bounding volumes don't
        intersect.
    -------------------------------------------------------------------
*/
class SATAlgorithm : public NarrowPhaseAlgorithm {
    private :
        bool computeCollisionTest(const OBB* const obb1, const OBB* const obb2, ContactInfo*& contactInfo) const;     // Return true and compute a contact info if the two OBB collide
        double computePenetrationDepth(double min1, double max1, double min2, double max2) const;                     // Compute the penetration depth of two projection intervals                             
        Vector3D computeContactNormal(const Vector3D& axis, const Vector3D& distanceOfOBBs) const;                    // Compute a contact normal

    public :
        SATAlgorithm();           // Constructor
        ~SATAlgorithm();          // Destructor

        virtual bool testCollision(const BoundingVolume* const boundingVolume1, const BoundingVolume* const boundingVolume2, ContactInfo*& contactInfo);      // Return true and compute a contact info if the two bounding volume collide
};

// Return the contact normal with the correct sign (from obb1 toward obb2). "axis" is the axis vector direction where the
// collision occur and "distanceOfOBBs" is the vector (obb2.center - obb1.center).
inline Vector3D SATAlgorithm::computeContactNormal(const Vector3D& axis, const Vector3D& distanceOfOBBs) const {
    if (distanceOfOBBs.scalarProduct(axis) >= 0.0) {
        return axis;
    }
    else {
        return axis.getOpposite();
    }
}

} // End of the ReactPhysics3D namespace

#endif