#ifndef __JDIRECTION2D__
#define __JDIRECTION2D__

#include <cmath>

#include "JGeometry2D/JAngle2D.hh"
#include "JGeometry2D/JPoint2D.hh"
#include "JGeometry2D/JRotation2D.hh"


namespace JGEOMETRY2D {


  /**
   * Data structure for direction in two dimensions.
   */
  class JDirection2D :
    public JAngle2D 
  {
  public:
    /**
     * Default constructor.
     */
    JDirection2D() :
      JAngle2D()
    {}


    /**
     * Constructor.
     *
     * \param  phi      phi angle [rad]
     */
    JDirection2D(const double phi) :
      JAngle2D(phi)
    {}


    /**
     * Constructor.
     *
     * \param  vector   vector
     */
    JDirection2D(JVector2D vector) :
      JAngle2D(atan2(vector.getY(),vector.getX()))
    {}


    /**
     * Constructor.
     *
     * \param  x        x value
     * \param  y        y value
     */
    JDirection2D(const double x,
		 const double y) :
      JAngle2D()
    {
      __phi = atan2(y,x);
    }


    /**
     * Transform.
     *
     * \param  R        matrix
     */
    JDirection2D& transform(const JMatrix2D& R)
    {
      *this = JPoint2D(*this).transform(R);

      return *this;
    }


    /**
     * Rotate.
     *
     * \param  R        rotation matrix
     */
    JDirection2D& rotate(const JRotation2D& R)
    {
      *this = JPoint2D(*this).rotate(R);

      return *this;
    }


    /**
     * Rotate back.
     *
     * \param  R        rotation matrix
     */
    JDirection2D& rotate_back(const JRotation2D& R)
    {
      *this = JPoint2D(*this).rotate_back(R);

      return *this;
    }
  };


  /**
   * Dot product.
   *
   * \param  first     JDirection2D
   * \param  second    JDirection2D
   * \return           dot product
   */
  inline double dot(const JDirection2D& first,
                    const JDirection2D& second)
  {
    return
      first.getDX() * second.getDX() + 
      first.getDY() * second.getDY();
  }
}

#endif