/*
 * © Copyright 2014 – Urheberrechtshinweis
 * Alle Rechte vorbehalten / All Rights Reserved
 *
 * Programmcode ist urheberrechtlich geschuetzt.
 * Das Urheberrecht liegt, soweit nicht ausdruecklich anders gekennzeichnet, bei Frank Ebner.
 * Keine Verwendung ohne explizite Genehmigung.
 * (vgl. § 106 ff UrhG / § 97 UrhG)
 */

#ifndef TRIANGLE3_H
#define TRIANGLE3_H

#include "Point3.h"
#include "Ray3.h"

struct Triangle3 {

	Point3 p1;
	Point3 p2;
	Point3 p3;

public:

	/** empty ctor */
	Triangle3() : p1(), p2(), p3() {;}

	/** ctor */
	Triangle3(Point3 p1, Point3 p2, Point3 p3) : p1(p1), p2(p2), p3(p3) {;}


//	Point3 cross(Point3 b, Point3 c) const {
//		return Point3(
//			b.y*c.z - c.y*b.z,
//			b.z*c.x - c.z*b.x,
//			b.x*c.y - c.x*b.y
//		);
//	}

//	float dot(Point3 b, Point3 c) const {
//		return b.x*c.x + b.y*c.y + b.z*c.z;
//	}

	Triangle3 operator - (const Point3 o) const {
		return Triangle3(p1-o, p2-o, p3-o);
	}
	Triangle3& operator += (const Point3 o) {
		p1 += o;
		p2 += o;
		p3 += o;
		return *this;
	}
	Triangle3& operator -= (const Point3 o) {
		p1 -= o;
		p2 -= o;
		p3 -= o;
		return *this;
	}

	/** scale using 3 individual components */
	Triangle3& operator *= (const Point3 o) {
		p1 *= o;
		p2 *= o;
		p3 *= o;
		return *this;
	}

	/** switch between CW<->CCW */
	void reverse() {
		std::swap(p2, p3);
	}

	void rotate_deg(const Point3 rot) {
		p1 = p1.rot(rot.x/180.0f*M_PI, rot.y/180.0f*M_PI, rot.z/180.0f*M_PI);
		p2 = p2.rot(rot.x/180.0f*M_PI, rot.y/180.0f*M_PI, rot.z/180.0f*M_PI);
		p3 = p3.rot(rot.x/180.0f*M_PI, rot.y/180.0f*M_PI, rot.z/180.0f*M_PI);
	}

//	void ensureCCW() {
//		Point3 norm = cross(p3-p1, p2-p1);
//		if (norm.z < 0) {
//			reverse();
//		}
//	}

	Point3 getNormal() const {
		return cross( p2-p1, p3-p1 ).normalized();
	}


	// http://www.lighthouse3d.com/tutorials/maths/ray-triangle-intersection/
	bool intersects(const Ray3& ray, Point3& pos) const {

		const Point3 e1 = p2-p1;
		const Point3 e2 = p3-p1;

		const Point3 h = cross(ray.dir, e2);
		const double a = dot(e1, h);

		if (a > -0.00001 && a < 0.00001) {return false;}

		const double f = 1/a;

		const Point3 s = ray.start - p1;
		const double u = f * dot(s,h);

		if (u < 0.0 || u > 1.0) {return false;}

		const Point3 q = cross(s, e1);
		const double v = f * dot(ray.dir, q);

		if (v < 0.0 || u + v > 1.0) {return false;}
		const double t = f * dot(e2,q);


		if (t > 0.00001) {
			pos = ray.start + (ray.dir * t);
			return true;
		}

		return false;

	}

	/** add some slight delta to prevent rounding issues */
	bool intersectsDelta(const Ray3& ray, const double delta, Point3& pos) const {

		const Point3 e1 = p2-p1;
		const Point3 e2 = p3-p1;

		// make delta an absolute value (independent of the triangle's size)
		// larger triangle -> smaller delta, as u,v are [0:1]
		//double deltaU = delta/e2.length();
		//double deltaV = delta/e1.length();

		const double deltaU = delta;
		const double deltaV = delta;

		const Point3 h = cross(ray.dir, e2);
		const double a = dot(e1, h);

		if (a > -0.00001 && a < 0.00001) {return false;}

		const double f = 1/a;

		const Point3 s = ray.start - p1;
		const double u = f * dot(s,h);

		if (u < 0.0-deltaU || u > 1.0+deltaU) {return false;}

		const Point3 q = cross(s, e1);
		const double v = f * dot(ray.dir, q);

		if (v < 0.0-deltaV || u + v > 1.0+deltaV) {return false;}
		const double t = f * dot(e2,q);


		if (t > 0.00001) {
			pos = ray.start + (ray.dir * t);
			return true;
		}

		return true;

	}

	/** perform some sanity checks */
	bool isValid() const {
		if (p1 == p2) {return false;}
		if (p1 == p3) {return false;}
		if (p2 == p3) {return false;}
		return true;
	}

/*
	int rayIntersectsTriangle(float *p, float *d,
				float *v0, float *v1, float *v2) {

		float e1[3],e2[3],h[3],s[3],q[3];
		float a,f,u,v;

		//crossProduct(h,d,e2);
		a = innerProduct(e1,h);

		if (a > -0.00001 && a < 0.00001)
			return(false);

		f = 1/a;
		vector(s,p,v0);
		u = f * (innerProduct(s,h));

		if (u < 0.0 || u > 1.0)
			return(false);

		crossProduct(q,s,e1);
		v = f * innerProduct(d,q);

		if (v < 0.0 || u + v > 1.0)
			return(false);

		// at this stage we can compute t to find out where
		// the intersection point is on the line
		t = f * innerProduct(e2,q);

		if (t > 0.00001) // ray intersection
			return(true);

		else // this means that there is a line intersection
			 // but not a ray intersection
			 return (false);

	}
*/
};

#endif // TRIANGLE3_H