#ifndef QUATERNION_H
#define QUATERNION_H

#pragma once
struct Vector3;

extern "C" {
	typedef struct Quat {
		float x;
		float y;
		float z;
		float w;
	} Quat;
	void CopyQuat(const Quat& q1, Quat& q2);
}


/// <summary>
/// A quaternion
/// </summary>
struct Quaternion : Quat {
public:
	/// <summary>
	/// Create a new identity quaternion
	/// </summary>
	Quaternion();
	/// <summary>
	/// create a new quaternion with the given values
	/// </summary>
	/// <param name="_x">x axis value</param>
	/// <param name="_y">y axis value</param>
	/// <param name="_z">z axis value</param>
	/// <param name="_w">w axis value</param>
	Quaternion(float _x, float _y, float _z, float _w);
	/// <summary>
	/// Create a quaternion from C-style Quat
	/// </summary>
	/// <param name="q"></param>
	Quaternion(Quat q);
	~Quaternion();

	/// <summary>
	/// An identity quaternion
	/// </summary>
	const static Quaternion identity;

	void Normalize();
	static Quaternion Normalize(const Quaternion& q);
	static void Normalize(const Quaternion& q, Quaternion& result);

	static Vector3 ToAngles(const Quaternion& q1);

	Vector3 operator *(const Vector3& p) const;
	Quaternion operator *(const Quaternion& r2) const;

	bool operator ==(const Quaternion& q);

	static Quaternion Inverse(Quaternion r);

	static Quaternion LookRotation(const Vector3& forward, const Vector3& upwards);
	static Quaternion LookRotation(const Vector3& forward);

	static Quaternion FromToRotation(Vector3 fromDirection, Vector3 toDirection);

	static Quaternion RotateTowards(const Quaternion& from, const Quaternion& to, float maxDegreesDelta);
	static Quaternion AngleAxis(float angle, const Vector3& axis);
	void ToAngleAxis(float* angle, Vector3* axis);
	static void ToAxisAngleRad(const Quaternion& q, Vector3* const axis, float* angle);
	static float Angle(Quaternion a, Quaternion b);
	static Quaternion Slerp(const Quaternion& a, const Quaternion& b, float t);
	static Quaternion SlerpUnclamped(const Quaternion& a, const Quaternion& b, float t);

	static Quaternion Euler(float x, float y, float z);
	static Quaternion Euler(Vector3 euler);
	static Quaternion FromEulerRad(Vector3 euler);
	static float GetAngleAround(Vector3 axis, Quaternion rotation);
	static Quaternion GetRotationAround(Vector3 axis, Quaternion rotation);
	static void GetSwingTwist(Vector3 axis, Quaternion rotation, Quaternion* swing, Quaternion* twist);

protected:
	float GetLength() const;
	float GetLengthSquared() const;
	static float GetLengthSquared(const Quaternion& q);

	static float Dot(Quaternion a, Quaternion b);

public:
	Vector3 xyz() const;
};

//#include "Vector3.h"


#endif