///////////////////////////////////////////////////////////////////////////////////////////////////
// OpenGL Mathematics Copyright (c) 2005 - 2011 G-Truc Creation (www.g-truc.net)
///////////////////////////////////////////////////////////////////////////////////////////////////
// Created : 2007-04-03
// Updated : 2009-01-20
// Licence : This source is under MIT licence
// File    : glm/gtx/intersect.inl
///////////////////////////////////////////////////////////////////////////////////////////////////

#include <cfloat>
#include <limits>

namespace glm{
namespace gtx{
namespace intersect{

template <typename genType>
inline bool intersectRayTriangle
(
	genType const & orig, genType const & dir,
	genType const & v0, genType const & v1, genType const & v2,
	genType & baryPosition
)
{
	genType e1 = v1 - v0;
	genType e2 = v2 - v0;

	genType p = glm::cross(dir, e2);

	typename genType::value_type a = glm::dot(e1, p);

	typename genType::value_type Epsilon = std::numeric_limits<typename genType::value_type>::epsilon();
	if(a < Epsilon)
		return false;

	typename genType::value_type f = typename genType::value_type(1.0f) / a;

	genType s = orig - v0;
	baryPosition.x = f * glm::dot(s, p);
	if(baryPosition.x < typename genType::value_type(0.0f))
		return false;
	if(baryPosition.x > typename genType::value_type(1.0f))
		return false;

	genType q = glm::cross(s, e1);
	baryPosition.y = f * glm::dot(dir, q);
	if(baryPosition.y < typename genType::value_type(0.0f))
		return false;
	if(baryPosition.y + baryPosition.x > typename genType::value_type(1.0f))
		return false;

	baryPosition.z = f * glm::dot(e2, q);

	return baryPosition.z >= typename genType::value_type(0.0f);
}

//template <typename genType>
//inline bool intersectRayTriangle
//(
//	genType const & orig, genType const & dir,
//	genType const & vert0, genType const & vert1, genType const & vert2,
//	genType & position
//)
//{
//	typename genType::value_type Epsilon = std::numeric_limits<typename genType::value_type>::epsilon();
//
//	genType edge1 = vert1 - vert0;
//	genType edge2 = vert2 - vert0;
//
//	genType pvec = cross(dir, edge2);
//
//	float det = dot(edge1, pvec);
//	if(det < Epsilon)
//		return false;
//
//	genType tvec = orig - vert0;
//
//	position.y = dot(tvec, pvec);
//	if (position.y < typename genType::value_type(0) || position.y > det)
//		return typename genType::value_type(0);
//
//	genType qvec = cross(tvec, edge1);
//
//	position.z = dot(dir, qvec);
//	if (position.z < typename genType::value_type(0) || position.y + position.z > det)
//		return typename genType::value_type(0);
//
//	position.x = dot(edge2, qvec);
//	position *= typename genType::value_type(1) / det;
//
//	return typename genType::value_type(1);
//}

template <typename genType>
inline bool intersectLineTriangle
(
	genType const & orig, genType const & dir,
	genType const & vert0, genType const & vert1, genType const & vert2,
	genType & position
)
{
    typename genType::value_type Epsilon = std::numeric_limits<typename genType::value_type>::epsilon();

	genType edge1 = vert1 - vert0;
	genType edge2 = vert2 - vert0;

	genType pvec = cross(dir, edge2);

	float det = dot(edge1, pvec);

	if (det > -Epsilon && det < Epsilon)
		return false;
	float inv_det = typename genType::value_type(1) / det;

	genType tvec = orig - vert0;

	position.y = dot(tvec, pvec) * inv_det;
	if (position.y < typename genType::value_type(0) || position.y > typename genType::value_type(1))
		return false;

	genType qvec = cross(tvec, edge1);

	position.z = dot(dir, qvec) * inv_det;
	if (position.z < typename genType::value_type(0) || position.y + position.z > typename genType::value_type(1))
		return false;

	position.x = dot(edge2, qvec) * inv_det;

	return true;
}

template <typename genType>
inline bool intersectRaySphere
(
	genType const & rayStarting, genType const & rayDirection,
	genType const & sphereCenter, typename genType::value_type sphereRadius,
	genType & position, genType & normal
)
{
	typename genType::value_type Epsilon = std::numeric_limits<typename genType::value_type>::epsilon();

	typename genType::value_type a = dot(rayDirection, rayDirection);
	typename genType::value_type b = typename genType::value_type(2) * dot(rayStarting, rayDirection);
	typename genType::value_type c = dot(rayStarting, rayStarting) - sphereRadius * sphereRadius;
	typename genType::value_type d = b * b - typename genType::value_type(4) * a * c;
	typename genType::value_type e = sqrt(d);
	typename genType::value_type x1 = (-b - e) / (typename genType::value_type(2) * a);
	typename genType::value_type x2 = (-b + e) / (typename genType::value_type(2) * a);

	if(x1 > Epsilon)
	{
		position = rayStarting + rayDirection * sphereRadius;
		normal = (position - sphereCenter) / sphereRadius;
		return true;
	}
	else if(x2 > Epsilon)
	{
		position = rayStarting + rayDirection * sphereRadius;
		normal = (position - sphereCenter) / sphereRadius;
		return true;
	}
	return false;
}

template <typename genType>
inline bool intersectLineSphere
(
	genType const & point0, genType const & point1,
	genType const & center, typename genType::value_type radius,
	genType & position, genType & normal
)
{
	typename genType::value_type Epsilon = std::numeric_limits<typename genType::value_type>::epsilon();

    genType dir = point1 - point0;
    typename genType::value_type a = dot(dir, dir);
	typename genType::value_type b = typename genType::value_type(2) * dot(center, dir);
	typename genType::value_type c = dot(center, center) - radius * radius;
	typename genType::value_type d = b * b - typename genType::value_type(4) * a * c;
	typename genType::value_type e = sqrt(d);
	typename genType::value_type x1 = (-b - e) / (typename genType::value_type(2) * a);
	typename genType::value_type x2 = (-b + e) / (typename genType::value_type(2) * a);

	if(x1 > Epsilon)
	{
		position = center + dir * radius;
		normal = (position - center) / radius;
		return true;
	}
	else if(x2 > Epsilon)
	{
		position = center + dir * radius;
		normal = (position - center) / radius;
		return true;
	}
	return false;
}

}//namespace intersect
}//namespace gtx
}//namespace glm
