#ifndef ANGLE_H
#define ANGLE_H

#include <cmath>
#include "../Assertions.h"
#include "Point2.h"

struct Angle {


public:

	/** get the radians from (x1,y1) to (x2,y2) between 0 (to-the-right) and <2_PI */
	static float getRAD_2PI(const float x1, const float y1, const float x2, const float y2) {
		Assert::isFalse( (x1==x2)&&(y1==y2), "(x1,y1) must not equal (x2,y2)!!");
		const float tmp = std::atan2(y2-y1, x2-x1);
		return (tmp < 0) ? (tmp + 2*M_PI) : (tmp);
	}

	/** get the radians from (0,0) to (p.x,p.y) between 0 (to-the-right) and <2_PI */
	static float getRAD_2PI(const Point2& p) {
		return getRAD_2PI(0, 0, p.x, p.y);
	}

	/** get the degrees from (x1,y1) to (x2,y2) between 0 (to-the-right) and <360 */
	static float getDEG_360(const float x1, const float y1, const float x2, const float y2) {
		return radToDeg(getRAD_2PI(x1,y1,x2,y2));
	}


	/**
	 * gets the angular difference between
	 * - the given radians [0:2PI]
	 * - as a change-in-direction between [0:PI]
	 */
	static float getDiffRAD_2PI_PI(const float r1, const float r2) {
		Assert::isBetween(r1, 0.0f, (float)(2*M_PI), "r1 out of bounds");
		Assert::isBetween(r2, 0.0f, (float)(2*M_PI), "r2 out of bounds");
		float tmp = std::abs(r1-r2);
		return (tmp <= M_PI) ? (tmp) : (2*M_PI-tmp);
	}

	/**
	 * gets the angular difference between
	 * - the given radians [0:2PI]
	 * - as a change-in-direction between [-PI:+PI]
	 */
	static float getSignedDiffRAD_2PI(const float r1, const float r2) {
		Assert::isBetween(r1, 0.0f, (float)(2*M_PI), "r1 out of bounds");				// [0:360] deg
		Assert::isBetween(r2, 0.0f, (float)(2*M_PI), "r2 out of bounds");				// [0:360] deg
		float diff = r1-r2;
		if		(diff > +M_PI) {diff = -(2*M_PI - diff);}
		else if	(diff < -M_PI) {diff = +(2*M_PI + diff);}
		Assert::isBetween(diff, (float)-M_PI, (float)(+M_PI), "result out of bounds");	// [-180:+180] deg
		return diff;
	}

	/** convert degrees to radians */
	static constexpr inline float degToRad(const float deg) {
		return deg / 180.0f * M_PI;
	}

	/** convert radians to degrees */
	static constexpr inline float radToDeg(const float rad) {
		return rad * 180.0f / M_PI;
	}

	/** get a pointer vector (length 1) pointing to the given angle (in radians) */
	static Point2 getPointer(const float rad) {
		const float x = cos(rad);
		const float y = sin(rad);
		return Point2(x,y);
	}

};

#endif // ANGLE_H