#ifndef __Plane3_H__
#define __Plane3_H__

#include "Vector3.h"


namespace CHCDemoEngine 
{

/** Class describing a plane in 3D space.
*/
class Plane3 
{
public:

	Plane3() {}

	Plane3(const Vector3 &a, const Vector3 &b, const Vector3 &c);
	/** Note: we assume that the normal vector is already normalized.
	*/
	Plane3(const Vector3 &normal, const Vector3 &point);

	inline void ReverseOrientation()
	{
		mNormal *= -1;
		mD *= -1;
	}
	/** Get distance to a point.
	*/
	inline float Distance(const Vector3 &v) const 
	{
		return DotProd(v, mNormal) + mD;
	}

	enum {BACK_SIDE = -1, INTERSECTS = 0, FRONT_SIDE = 1};
	/** Returns 1 if v is on front side, -1 if on back side, 0 if on plane.
	*/
	int Side(const Vector3 &v, float threshold = 1e-6) const;
	/** Finds intersection of line segment between points a and b with plane.
	    @param a start point
		@param b end point
		@param t if not NULL, returns parameter value of intersections
		@param coplanar if not NULL, returns true if plane and line segments are coplanar.
	*/
	Vector3 FindIntersection(const Vector3 &a,
 		                     const Vector3 &b,
							 float *t = NULL,
							 bool *coplanar = NULL) const;

	/** Finds value of intersection parameter t on line segment from a to b.
	    @returns 0 if coplanar, else parameter t
	*/
	float FindT(const Vector3 &a, const Vector3 &b) const;

	operator const float*() const 
	{ 
		return (const float*) this; 
	}

	float& operator[] (const int inx) 
	{
		return (&mNormal.x)[inx];
	}

	const float &operator[] (const int inx) const 
	{
		return *(&mNormal.x + inx);
	}
	/** Transforms the plane  with the matrix m.
	*/
	void Transform(const Matrix4x4 &m);


	///////////
	//-- friends

	friend bool	PlaneIntersection(const Plane3 &a, const Plane3 &b, const Plane3 &c, Vector3 &result);

	friend bool PlaneIntersection(const Plane3 &p1, const Plane3 &p2);
	

	friend std::ostream &operator<<(std::ostream &s, const Plane3 &p) 
	{	
		s << p.mNormal << " " << p.mD;
		return s;
	}


//protected:

	///////////////

	Vector3 mNormal;
	float mD;
};


}
#endif