// @(#)root/mathcore:$Id$
// Authors: W. Brown, M. Fischler, L. Moneta    2005  

 /**********************************************************************
  *                                                                    *
  * Copyright (c) 2005 ROOT FNAL MathLib Team                          *
  *                                                                    *
  *                                                                    *
  **********************************************************************/

// Header file for BoostY
// 
// Created by: Mark Fischler  Mon Nov 1  2005
// 
// Last update: $Id$
// 
#ifndef ROOT_Math_GenVector_BoostY
#define ROOT_Math_GenVector_BoostY 1

#include "Math/GenVector/LorentzVector.h"
#include "Math/GenVector/PxPyPzE4D.h"
#include "Math/GenVector/DisplacementVector3D.h"
#include "Math/GenVector/Cartesian3D.h"

namespace ROOT {

namespace Math {

//__________________________________________________________________________________________
   /**
      Class representing a Lorentz Boost along the Y axis, by beta. 
      For efficiency, gamma is held as well. 

      @ingroup GenVector      
   */

class BoostY {

public:

   typedef double Scalar;

   enum ELorentzRotationMatrixIndex {
      kLXX =  0, kLXY =  1, kLXZ =  2, kLXT =  3
    , kLYX =  4, kLYY =  5, kLYZ =  6, kLYT =  7
    , kLZX =  8, kLZY =  9, kLZZ = 10, kLZT = 11
    , kLTX = 12, kLTY = 13, kLTZ = 14, kLTT = 15
   };

   enum EBoostMatrixIndex {
      kXX =  0, kXY =  1, kXZ =  2, kXT =  3
      , kYY =  4, kYZ =  5, kYT =  6
      , kZZ =  7, kZT =  8
      , kTT =  9
   };

   // ========== Constructors and Assignment =====================

   /**
      Default constructor (identity transformation)
   */
   BoostY();

   /**
      Construct given a Scalar beta_y
   */
   explicit BoostY(Scalar beta_y) { SetComponents(beta_y); }


   // The compiler-generated copy ctor, copy assignment, and dtor are OK.

   /**
      Re-adjust components to eliminate small deviations from a perfect
      orthosyplectic matrix.
   */
   void Rectify();

   // ======== Components ==============

   /**
      Set components from a Scalar beta_y
   */
   void
   SetComponents (Scalar beta_y);

   /**
      Get components into a Scalar beta_y
   */
   void
   GetComponents (Scalar& beta_y) const;


   /** 
       Retrieve the beta of the Boost 
   */ 
   Scalar Beta() const { return fBeta; }

   /** 
       Retrieve the gamma of the Boost 
   */ 
   Scalar Gamma() const { return fGamma; }

   /** 
       Set the given beta of the Boost 
   */ 
   void  SetBeta(Scalar beta) { SetComponents(beta); }
   
   /**
      The beta vector for this boost
   */
   typedef  DisplacementVector3D<Cartesian3D<double>, DefaultCoordinateSystemTag > XYZVector; 
   XYZVector BetaVector() const;

   /**
      Get elements of internal 4x4 symmetric representation, into a data
      array suitable for direct use as the components of a LorentzRotation
      Note -- 16 Scalars will be written into the array; if the array is not
      that large, then this will lead to undefined behavior.
   */
   void 
   GetLorentzRotation (Scalar r[]) const; 
  
   // =========== operations ==============

   /**
      Lorentz transformation operation on a Minkowski ('Cartesian') 
      LorentzVector
   */
   LorentzVector< ROOT::Math::PxPyPzE4D<double> >
   operator() (const LorentzVector< ROOT::Math::PxPyPzE4D<double> > & v) const;
  
   /**
      Lorentz transformation operation on a LorentzVector in any 
      coordinate system
   */
   template <class CoordSystem>
   LorentzVector<CoordSystem>
   operator() (const LorentzVector<CoordSystem> & v) const {
      LorentzVector< PxPyPzE4D<double> > xyzt(v);
      LorentzVector< PxPyPzE4D<double> > r_xyzt = operator()(xyzt);
      return LorentzVector<CoordSystem> ( r_xyzt );
   }

   /**
      Lorentz transformation operation on an arbitrary 4-vector v.
      Preconditions:  v must implement methods x(), y(), z(), and t()
      and the arbitrary vector type must have a constructor taking (x,y,z,t)
   */
   template <class Foreign4Vector>
   Foreign4Vector
   operator() (const Foreign4Vector & v) const {
      LorentzVector< PxPyPzE4D<double> > xyzt(v);
      LorentzVector< PxPyPzE4D<double> > r_xyzt = operator()(xyzt);
      return Foreign4Vector ( r_xyzt.X(), r_xyzt.Y(), r_xyzt.Z(), r_xyzt.T() );
   }

   /**
      Overload operator * for rotation on a vector
   */
   template <class A4Vector>
   inline
   A4Vector operator* (const A4Vector & v) const
   {
      return operator()(v);
   }

   /**
      Invert a BoostY in place
   */
   void Invert();

   /**
      Return inverse of  a rotation
   */
   BoostY Inverse() const;

   /**
      Equality/inequality operators
   */
   bool operator == (const BoostY & rhs) const {
      if( fBeta  != rhs.fBeta  ) return false;
      if( fGamma != rhs.fGamma ) return false;
      return true;
   }
   bool operator != (const BoostY & rhs) const {
      return ! operator==(rhs);
   }

private:

   Scalar fBeta;    // beta Y of the Boost
   Scalar fGamma;   // gamma of the Boost 

};  // BoostY

// ============ Class BoostY ends here ============

/**
   Stream Output and Input
*/
   // TODO - I/O should be put in the manipulator form 

   std::ostream & operator<< (std::ostream & os, const BoostY & b);


} //namespace Math
} //namespace ROOT







#endif /* ROOT_Math_GenVector_BoostY  */