/* -*- mia-c++  -*-
 *
 * This file is part of MIA - a toolbox for medical image analysis 
 * Copyright (c) Leipzig, Madrid 1999-2015 Gert Wollny
 *
 * MIA is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with MIA; if not, see <http://www.gnu.org/licenses/>.
 *
 */

#ifndef mia_3d_quaternion_hh
#define mia_3d_quaternion_hh

#include <ostream>
#include <mia/3d/defines3d.hh>
#include <mia/3d/matrix.hh>
#include <mia/3d/vector.hh>

NS_MIA_BEGIN 

/**
   \ingroup misc 
   \brief a class to implement a quaternion
   
   This class implements some operations of a quaternion. 
   The rotation is implemented as clockwise/left-handed rotation. 

*/

class EXPORT_3D Quaternion {

public: 
        /**
	   The standard constructor that sets all values of the quaternion to zero. 
	*/
	Quaternion(); 

	/**
	   The copy constructor. 
	   \param other 
	 */
	Quaternion(const Quaternion& other) = default; 

	/**
	   This constructor creates a quaternion from three Euler angles that are applied 
	   with the <a href="https://secure.wikimedia.org/wikipedia/en/wiki/Conversion_between_quaternions_and_Euler_angles">x-y-z convention</a>. 
	   \param rot 
	*/
	Quaternion(const C3DDVector& rot); 


	/**
	   This constructor creates a quaternion from a 3x3 rotation matrix. 
	   If mat3x3 is not a true rotation matrix, then this constructor evaluates the 
	   rotation quaternion that best resembles the matrix transformation.
	   \param rot
	*/
	Quaternion(const C3DFMatrix& rot); 

	/**
	   This constructor creates a quaternion from a 3x3 rotation matrix. 
	   If mat3x3 is not a true rotation matrix, then this constructor evaluates the 
	   rotation quaternion that best resembles the matrix transformation.
	   \param rot
	*/
	Quaternion(const C3DDMatrix& rot); 

	/**
	   Constructor to create a quaternion by directly setting its elements. 
	 */
	Quaternion(double w, double  x, double y, double z); 

	/**
	   \param a
	   \param b 
	   \returns true if the quaternions are element-wise equal
	 */
	
	friend bool operator == (const Quaternion& a, const Quaternion& b); 

	/// \returns the norm of the quaternion 
	double norm() const; 

	/// normalizes to quaternion 
	void normalize(); 

	/// \returns the inverse of the quaternion assuming it is normalized 
	Quaternion inverse() const;

	/// \returns the Euler angles that correspond to the rotation described by this quaternion 
	C3DDVector get_euler_angles() const;

	/**
	   in-place adding  
	   \param other 
	   \returns reference to the updated quaternion 
	 */
	Quaternion& operator += (const Quaternion& other); 

	/**
	   in-place substraction 
	   \param other 
	   \returns reference to the updated quaternion 
	 */
	Quaternion& operator -= (const Quaternion& other); 

	/**
	   in-place multiplication 
	   \param other 
	   \returns reference to the updated quaternion 
	 */

	Quaternion& operator *= (const Quaternion& other); 

	/**
	   Print the quaternion to an output stream 
	   \param os the output stream 
	 */
	void print(std::ostream& os) const; 

	/// \returns the w- or $x_0$ component of the quaternion 
	double w() const; 
	
	/// \returns the x- or $x_1$ component of the quaternion 
	double x() const; 
	
	/// \returns the y- or $x_2$ component of the quaternion 
	double y() const; 

	/// \returns the z- or $x_3$ component of the quaternion 
	double z() const; 

	const C3DDMatrix get_rotation_matrix() const; 

	static const Quaternion _1; 

private:
	C3DDVector m_v; 
	double m_w; 
}; 

bool EXPORT_3D operator == (const Quaternion& a, const Quaternion& b); 
bool EXPORT_3D operator != (const Quaternion& a, const Quaternion& b); 




inline double Quaternion::w() const
{
	return m_w; 
}

inline double Quaternion::x() const
{
	return m_v.x; 
}

inline double Quaternion::y() const
{
	return m_v.y; 
}

inline double Quaternion::z() const
{
	return m_v.z; 
}



inline std::ostream& operator << (std::ostream& os, const Quaternion& a) 
{
	a.print(os); 
	return os; 
}

EXPORT_3D std::istream& operator >> (std::istream& os, Quaternion& a); 

NS_MIA_END

#endif
