#ifndef LINE2D_H
#define LINE2D_H

//#include <KLib/geo/Line.h>
#include "Point2.h"
#include "Ray2.h"

class Line2 {

public:

	Point2 p1;

	Point2 p2;

public:

	/** empty ctor */
	Line2() : p1(), p2() {;}

	/** value ctor */
	Line2(const Point2 p1, const Point2 p2) : p1(p1), p2(p2) {;}

	/** value ctor */
	Line2(const float x1, const float y1, const float x2, const float y2) : p1(x1,y1), p2(x2,y2) {;}


	Line2 operator * (const float v) const {return Line2(p1*v, p2*v);}

//	bool getSegmentIntersection(const Line& other) const {
//		static K::Point p;
//		return K::Line::getSegmentIntersection(other, p);
//	}


	float getAngle() const {
		return std::atan2(p2.y-p1.y, p2.x-p1.x);
	}

	void reverse() {
		std::swap(p1, p2);
	}

	float getLength() const {
		return p1.getDistance(p2);
	}

	/** keep the starting point, but make the line longer by the given length */
	Line2 longerAtEnd(const float l) {
		Point2 dir = p2-p1;
		return Line2(p1, p1+dir+dir.normalized()*l);
	}

	/** keep the ending point, but make the line longer by the given length */
	Line2 longerAtStart(const float l) {
		Point2 dir = p1-p2;
		return Line2(p2, p2+dir+dir.normalized()*l);
	}

	/** get intersection between these two lines (unlimited length!) */
	bool getLineIntersection(const Line2& other, Point2& result) const {

		    double bx = p2.x - p1.x;
			double by = p2.y - p1.y;

			double dx = other.p2.x - other.p1.x;
			double dy = other.p2.y - other.p1.y;

			double b_dot_d_perp = bx*dy - by*dx;

			if(b_dot_d_perp == 0) {return false;}

			double cx = other.p1.x - p1.x;
			double cy = other.p1.y - p1.y;
			double t = (cx*dy - cy*dx) / b_dot_d_perp;

			result.x = p1.x + t * bx;
			result.y = p1.y + t * by;

			return true;

	}

	bool getSegmentIntersection(const Line2& other) const {

		const float p0_x = p1.x, p1_x = p2.x, p2_x = other.p1.x, p3_x = other.p2.x;
		const float p0_y = p1.y, p1_y = p2.y, p2_y = other.p1.y, p3_y = other.p2.y;

		const float s1_x = p1_x - p0_x;
		const float s1_y = p1_y - p0_y;
		const float s2_x = p3_x - p2_x;
		const float s2_y = p3_y - p2_y;

		const float s = (-s1_y * (p0_x - p2_x) + s1_x * (p0_y - p2_y)) / (-s2_x * s1_y + s1_x * s2_y);
		const float t = ( s2_x * (p0_y - p2_y) - s2_y * (p0_x - p2_x)) / (-s2_x * s1_y + s1_x * s2_y);

		if (s >= 0 && s <= 1 && t >= 0 && t <= 1) {
				// Collision detected
//				if (i_x != NULL)
//					*i_x = p0_x + (t * s1_x);
//				if (i_y != NULL)
//					*i_y = p0_y + (t * s1_y);
				return true;
		}

		return false; // No collision



//		const double delta = 0.0000001;

//		const double bx = p2.x - p1.x;
//		const double by = p2.y - p1.y;

//		const double dx = other.p2.x - other.p1.x;
//		const double dy = other.p2.y - other.p1.y;

//		const double b_dot_d_perp = bx*dy - by*dx;

//		if (std::abs(b_dot_d_perp) == 0) {return false;}

//		const double cx = other.p1.x - p1.x;
//		const double cy = other.p1.y - p1.y;

//		const double t = (cx * dy - cy * dx) / b_dot_d_perp;
//		if(t < 0+delta || t > 1-delta) {
//			return false;}

//		const double u = (cx * by - cy * bx) / b_dot_d_perp;
//		if(u < 0+delta || u > 1-delta) {
//			return false;}

//		return true;

	}

	bool getSegmentIntersection(const Line2& other, Point2& result) const {

		const float delta = 0.000001;

		const float bx = p2.x - p1.x;
		const float by = p2.y - p1.y;

		const float dx = other.p2.x - other.p1.x;
		const float dy = other.p2.y - other.p1.y;

		const float b_dot_d_perp = bx*dy - by*dx;

		if(b_dot_d_perp == 0) {return false;}

		const float cx = other.p1.x - p1.x;
		const float cy = other.p1.y - p1.y;

		const float t = (cx * dy - cy * dx) / b_dot_d_perp;
		if(t < 0+delta || t > 1-delta) {
			return false;}

		const float u = (cx * by - cy * bx) / b_dot_d_perp;
		if(u < 0+delta || u > 1-delta) {
			return false;}

		result.x = p1.x + t * bx;
		result.y = p1.y + t * by;

		return true;

	}


	bool getSegmentIntersectionInt(const Line2& other, Point2& result) const {

		int mul = 100;

		const float p0_x = std::round(p1.x*mul), p1_x = std::round(p2.x*mul), p2_x = std::round(other.p1.x*mul), p3_x = std::round(other.p2.x*mul);
		const float p0_y = std::round(p1.y*mul), p1_y = std::round(p2.y*mul), p2_y = std::round(other.p1.y*mul), p3_y = std::round(other.p2.y*mul);

		const float s1_x = p1_x - p0_x;
		const float s1_y = p1_y - p0_y;
		const float s2_x = p3_x - p2_x;
		const float s2_y = p3_y - p2_y;

		const float s = (-s1_y * (p0_x - p2_x) + s1_x * (p0_y - p2_y)) / (-s2_x * s1_y + s1_x * s2_y);
		const float t = ( s2_x * (p0_y - p2_y) - s2_y * (p0_x - p2_x)) / (-s2_x * s1_y + s1_x * s2_y);

		if (s >= 0 && s <= 1 && t >= 0 && t <= 1) {
			result.x = (p0_x + (t * s1_x)) / mul;
			result.y = (p0_y + (t * s1_y)) / mul;
			return true;
		}

		return false;

	}

	/** does the line intersect with the given ray? */
	bool intersects(const Ray2& ray, Point2& result) const {

		//https://stackoverflow.com/questions/563198/how-do-you-detect-where-two-line-segments-intersect/565282#565282

		const float p0_x = p1.x, p1_x = p2.x;
		const float p0_y = p1.y, p1_y = p2.y;

		const float p2_x = ray.start.x;//, p3_x = other.p2.x;
		const float p2_y = ray.start.y;//, p3_y = other.p2.y;

		const float s1_x = p1_x - p0_x;
		const float s1_y = p1_y - p0_y;

		const float s2_x = ray.dir.x;		// p3_x - p2_x;
		const float s2_y = ray.dir.y;		// p3_y - p2_y;

		// ray_start + s * ray_dir
		const float s = (-s1_y * (p0_x - p2_x) + s1_x * (p0_y - p2_y)) / (-s2_x * s1_y + s1_x * s2_y);

		// before the ray's start?
		if (s < 0) {return false;}

		// line.p1 + t * (line.p2-line.p1)
		const float t = ( s2_x * (p0_y - p2_y) - s2_y * (p0_x - p2_x)) / (-s2_x * s1_y + s1_x * s2_y);

		// t must be between 0 and 1, otherwise we are before the line's start / after the line's end
		if (t < 0 || t > 1) {return false;}

		// intersection
		result.x = (p0_x + (t * s1_x));
		result.y = (p0_y + (t * s1_y));
		return true;

	}


};


static inline bool intersects(const Line2& l1, const Line2& l2, bool limit, Point2& pos, float* _u = nullptr) {

	// (sx1,sy1) + (dx1, dy1)*u  =  (sx2, sy2) + (dx2, dy2)*v
	// solve((c+d*v-a)/b = (g+h*v-e)/f, v)
	// solve((a+b*u-c)/d = (e+f*u-g)/h, u)
	// bf != 0
	// dh != 0
	// df != bh			// kollinear (b/d != f/h)

	const float sx1 = l1.p1.x;	// a
	const float sy1 = l1.p1.y;	// e

	const float dx1 = l1.p2.x - l1.p1.x;	// b
	const float dy1 = l1.p2.y - l1.p1.y;	// f

	const float sx2 = l2.p1.x; // c
	const float sy2 = l2.p1.y; // g

	const float dx2 = l2.p2.x - l2.p1.x; // d
	const float dy2 = l2.p2.y - l2.p1.y; // h

	// collinear?
	const float a1 = dx2*dy1;
	const float a2 = dx1*dy2;
	if (std::abs(a1-a2) < 0.0001) {return false;}

	const float v = (dy1*(sx1-sx2) + dx1*(sy2-sy1)) / (dx2*dy1 - dx1*dy2);
	const float u = (dy2*(sx1-sx2) + dx2*(sy2-sy1)) / (dx2*dy1 - dx1*dy2);

	//const float x = sx2 + v*dx2;
	//const float y = sy2 + v*dy2;

	const float x = sx1 + u*dx1;
	const float y = sy1 + u*dy1;

	if (!limit || (u >= 0 && v >= 0 && u <= 1 && v <= 1)) {
		pos = Point2(x,y);
		if (_u) {*_u = u;}
		return true;
	}

	return false;

}




#endif // LINE2D_H