#ifndef __JVERSOR2D__
#define __JVERSOR2D__

#include <cmath>

#include "JIO/JSerialisable.hh"
#include "JGeometry2D/JDirection2D.hh"
#include "JGeometry2D/JRotation2D.hh"


namespace JGEOMETRY2D {

  namespace {
    using JIO::JReader;
    using JIO::JWriter;
  }


  /**
   * Data structure for normalised vector in two dimensions.
   */
  class JVersor2D
  {
  public:
    /**
     * Default constructor.
     */
    JVersor2D() :
      __dx(0.0),
      __dy(0.0)
    {}


    /**
     * Constructor.
     *
     * \param  angle    angle
     */
    JVersor2D(const JAngle2D& angle) :
      __dx(angle.getDX()),
      __dy(angle.getDY())
    {}


    /**
     * Constructor.
     *
     * \param  dx       dx value
     * \param  dy       dy value
     */
    JVersor2D(const double dx,
              const double dy) :
      __dx(dx),
      __dy(dy)
    {
      normalise();
    }


    /**
     * Get direction.
     *
     * \return               direction
     */
    const JVersor2D& getDirection() const
    {
      return static_cast<const JVersor2D&>(*this);
    }


    /**
     * Get direction.
     *
     * \return               direction
     */
    JVersor2D& getDirection()
    {
      return static_cast<JVersor2D&>(*this);
    }


    /**
     * Set direction.
     *
     * \param  dir           direction
     */
    void setDirection(const JVersor2D& dir)
    {
      static_cast<JVersor2D&>(*this) = dir;
    }


    /**
     * Read JVersor2D from input.
     *
     * \param  in       JReader
     * \param  versor   JVersor2D
     * \return          JReader
     */
    friend inline JReader& operator>>(JReader& in, JVersor2D& versor)
    {
      JAngle2D angle;

      in >> angle;

      __dx = angle.getDX();
      __dy = angle.getDY();

      return in;
    }


    /**
     * Write JVersor2D to output.
     *
     * \param  out      JWriter
     * \param  versor   JVersor2D
     * \return          JWriter
     */
    friend inline JWriter& operator<<(JWriter& out, const JVersor2D& versor)
    {
      const JDirection2D angle(getDX(), getDY());

      out << static_cast<JAngle2D&>(angle);

      return out;
    }


    /**
     * Type conversion operator.
     *
     * \return          JAngle2D
     */
    operator JDirection2D() const
    {
      return JDirection2D(getDX(), getDY());
    }


    /**
     * Get x direction.
     *
     * \return          x direction
     */
    double getDX() const
    {
      return __dx;
    }


    /**
     * Get y direction.
     *
     * \return          y direction
     */
    double getDY() const
    {
      return __dy;
    }

    
    /**
     * Rotate.
     *
     * \param  R        rotation matrix
     */
    JVersor2D& rotate(const JRotation2D& R)
    {
      R.rotate(__dx, __dy);

      return *this;
    }

    
    /**
     * Rotate back.
     *
     * \param  R        rotation matrix
     */
    JVersor2D& rotate_back(const JRotation2D& R)
    {
      R.rotate_back(__dx, __dy);

      return *this;
    }


    /**
     * Get dot product.
     *
     * \param  versor    JVersor2D
     * \return           dot product
     */
    double getDot(const JVersor2D& versor) const
    {
      return
	getDX() * versor.getDX() + 
	getDY() * versor.getDY();
    }

    /**
     * Normalise versor.
     */
    void normalise()
    {
      const double v = sqrt(getDX()*getDX() + getDY()*getDY());

      if (v != 0.0) {
        __dx /= v;
        __dy /= v;
      }
    }

  protected:
    double __dx;
    double __dy;
  };


  /**
   * Dot product.
   *
   * \param  first     JVersor2D
   * \param  second    JVersor2D
   * \return           dot product
   */
  inline double dot(const JVersor2D& first,
                    const JVersor2D& second)
  {
    return first.getDot(second);
  }
}

#endif