/*
Bullet Continuous Collision Detection and Physics Library
Copyright (c) 2003-2009 Erwin Coumans  http://bulletphysics.org

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.
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.
*/

#include "btTriangleMeshShape.h"
#include "../../LinearMath/btVector3.h"
#include "../../LinearMath/btQuaternion.h"
#include "btStridingMeshInterface.h"
#include "../../LinearMath/btAabbUtil2.h"
#include "../CollisionShapes/btCollisionMargin.h"

#include <cstring>

btTriangleMeshShape::btTriangleMeshShape(btStridingMeshInterface* meshInterface)
	: btConcaveShape(), m_meshInterface(meshInterface)
{
	m_shapeType = TRIANGLE_MESH_SHAPE_PROXYTYPE;
	if (meshInterface->hasPremadeAabb())
	{
		meshInterface->getPremadeAabb(&m_localAabbMin, &m_localAabbMax);
	}
	else
	{
		recalcLocalAabb();
	}
}

btTriangleMeshShape::~btTriangleMeshShape()
{
}

void btTriangleMeshShape::getAabb(const btTransform& trans, btVector3& aabbMin, btVector3& aabbMax)
{
	btVector3 localHalfExtents = btScalar(0.5) * (m_localAabbMax - m_localAabbMin);
	localHalfExtents += btVector3(getMargin(), getMargin(), getMargin());
	btVector3 localCenter = btScalar(0.5) * (m_localAabbMax + m_localAabbMin);

	btMatrix3x3 abs_b = trans.getBasis().absolute();

	btVector3 center = trans(localCenter);

	btVector3 extent = localHalfExtents.dot3(abs_b[0], abs_b[1], abs_b[2]);
	aabbMin = center - extent;
	aabbMax = center + extent;
}

void btTriangleMeshShape::recalcLocalAabb()
{
	for (int i = 0; i < 3; i++)
	{
		btVector3 vec(btScalar(0.), btScalar(0.), btScalar(0.));
		vec[i] = btScalar(1.);
		btVector3 tmp = localGetSupportingVertex(vec);
		m_localAabbMax[i] = tmp[i] + m_collisionMargin;
		vec[i] = btScalar(-1.);
		tmp = localGetSupportingVertex(vec);
		m_localAabbMin[i] = tmp[i] - m_collisionMargin;
	}
}

class SupportVertexCallback : public btTriangleCallback
{
	btVector3 m_supportVertexLocal;

public:
	btTransform m_worldTrans;
	btScalar m_maxDot;
	btVector3 m_supportVecLocal;

	SupportVertexCallback(const btVector3& supportVecWorld, const btTransform& trans)
		: m_supportVertexLocal(btScalar(0.), btScalar(0.), btScalar(0.)), m_worldTrans(trans), m_maxDot(btScalar(-BT_LARGE_FLOAT))

	{
		m_supportVecLocal = supportVecWorld * m_worldTrans.getBasis();
	}

	virtual void processTriangle(btVector3* triangle, int partId, int triangleIndex)
	{
		(void)partId;
		(void)triangleIndex;
		for (int i = 0; i < 3; i++)
		{
			btScalar dot = m_supportVecLocal.dot(triangle[i]);
			if (dot > m_maxDot)
			{
				m_maxDot = dot;
				m_supportVertexLocal = triangle[i];
			}
		}
	}

	btVector3 GetSupportVertexWorldSpace()
	{
		return m_worldTrans(m_supportVertexLocal);
	}

	btVector3 GetSupportVertexLocal()
	{
		return m_supportVertexLocal;
	}
};

//#define DEBUG_TRIANGLE_MESH

void btTriangleMeshShape::processAllTriangles(btTriangleCallback* callback, const btVector3& aabbMin, const btVector3& aabbMax) const
{
	struct FilteredCallback : public btInternalTriangleIndexCallback
	{
		btTriangleCallback* m_callback;
		btVector3 m_aabbMin;
		btVector3 m_aabbMax;

		FilteredCallback(btTriangleCallback* callback, const btVector3& aabbMin, const btVector3& aabbMax)
			: m_callback(callback),
			  m_aabbMin(aabbMin),
			  m_aabbMax(aabbMax)
		{
		}

		virtual void internalProcessTriangleIndex(btVector3* triangle, int partId, int triangleIndex)
		{
			if (TestTriangleAgainstAabb2(&triangle[0], m_aabbMin, m_aabbMax))
			{
				//check aabb in triangle-space, before doing this
				m_callback->processTriangle(triangle, partId, triangleIndex);
			}
		}
	};

	FilteredCallback filterCallback(callback, aabbMin, aabbMax);

	m_meshInterface->InternalProcessAllTriangles(&filterCallback, aabbMin, aabbMax);
}

void btTriangleMeshShape::calculateLocalInertia(btScalar mass, btVector3& inertia) const
{
	(void)mass;
	//moving concave objects not supported
	btAssert(0);
	inertia.setValue(btScalar(0.), btScalar(0.), btScalar(0.));
}

btVector3 btTriangleMeshShape::localGetSupportingVertex(const btVector3& vec) const
{
	btVector3 supportVertex;

	btTransform ident;
	ident.setIdentity();

	SupportVertexCallback supportCallback(vec, ident);

	btVector3 aabbMax(btScalar(BT_LARGE_FLOAT), btScalar(BT_LARGE_FLOAT), btScalar(BT_LARGE_FLOAT));

	processAllTriangles(&supportCallback, -aabbMax, aabbMax);

	supportVertex = supportCallback.GetSupportVertexLocal();

	return supportVertex;
}