/********************************************************************************
* ReactPhysics3D physics library, http://www.reactphysics3d.com                 *
* Copyright (c) 2010-2016 Daniel Chappuis                                       *
*********************************************************************************
*                                                                               *
* This software is provided 'as-is', without any express or implied warranty.   *
* In no event will the authors be held liable for any damages arising from the  *
* use of this software.                                                         *
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* Permission is granted to anyone to use this software for any purpose,         *
* including commercial applications, and to alter it and redistribute it        *
* freely, subject to the following restrictions:                                *
*                                                                               *
* 1. The origin of this software must not be misrepresented; you must not claim *
*    that you wrote the original software. If you use this software in a        *
*    product, an acknowledgment in the product documentation would be           *
*    appreciated but is not required.                                           *
*                                                                               *
* 2. Altered source versions must be plainly marked as such, and must not be    *
*    misrepresented as being the original software.                             *
*                                                                               *
* 3. This notice may not be removed or altered from any source distribution.    *
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********************************************************************************/

// Libraries
#include "SphereVsConvexPolyhedronAlgorithm.h"
#include "GJK/GJKAlgorithm.h"
#include "SAT/SATAlgorithm.h"

// We want to use the ReactPhysics3D namespace
using namespace reactphysics3d;

// Compute the narrow-phase collision detection between a sphere and a convex polyhedron
// This technique is based on the "Robust Contact Creation for Physics Simulations" presentation
// by Dirk Gregorius.
bool SphereVsConvexPolyhedronAlgorithm::testCollision(NarrowPhaseInfo* narrowPhaseInfo, bool reportContacts) {

    assert(narrowPhaseInfo->collisionShape1->getType() == CollisionShapeType::CONVEX_POLYHEDRON ||
        narrowPhaseInfo->collisionShape2->getType() == CollisionShapeType::CONVEX_POLYHEDRON);
    assert(narrowPhaseInfo->collisionShape1->getType() == CollisionShapeType::SPHERE ||
        narrowPhaseInfo->collisionShape2->getType() == CollisionShapeType::SPHERE);

    // First, we run the GJK algorithm
    GJKAlgorithm gjkAlgorithm;
    GJKAlgorithm::GJKResult result = gjkAlgorithm.testCollision(narrowPhaseInfo, reportContacts);

    narrowPhaseInfo->overlappingPair->getLastFrameCollisionInfo().wasUsingGJK = true;
    narrowPhaseInfo->overlappingPair->getLastFrameCollisionInfo().wasUsingSAT = false;

    // If we have found a contact point inside the margins (shallow penetration)
    if (result == GJKAlgorithm::GJKResult::COLLIDE_IN_MARGIN) {

        // Return true
        return true;
    }

    // If we have overlap even without the margins (deep penetration)
    if (result == GJKAlgorithm::GJKResult::INTERPENETRATE) {

        // Run the SAT algorithm to find the separating axis and compute contact point
        SATAlgorithm satAlgorithm;
        bool isColliding =  satAlgorithm.testCollisionSphereVsConvexPolyhedron(narrowPhaseInfo, reportContacts);

        narrowPhaseInfo->overlappingPair->getLastFrameCollisionInfo().wasUsingGJK = false;
        narrowPhaseInfo->overlappingPair->getLastFrameCollisionInfo().wasUsingSAT = true;

        return isColliding;
    }

    return false;
}