// @(#)root/mathcore:$Name:  $:$Id: CylindricalEta3D.h,v 1.2 2005/09/19 16:43:07 brun Exp $
// Authors: W. Brown, M. Fischler, L. Moneta    2005  

 /**********************************************************************
  *                                                                    *
  * Copyright (c) 2005 , LCG ROOT MathLib Team  and                    *
  *                      FNAL LCG ROOT MathLib Team                    *
  *                                                                    *
  *                                                                    *
  **********************************************************************/

// Header file for class CylindricalEta3D
// 
// Created by: Lorenzo Moneta  at Mon May 30 11:58:46 2005
// Major revamp:  M. Fischler  at Fri Jun 10 2005
// 
// Last update: $Id: CylindricalEta3D.h,v 1.2 2005/09/19 16:43:07 brun Exp $
// 
#ifndef ROOT_Math_GenVector_CylindricalEta3D 
#define ROOT_Math_GenVector_CylindricalEta3D  1

#include "Math/GenVector/etaMax.h"

#include <cmath>
#include <limits>

#if defined(__MAKECINT__) || defined(G__DICTIONARY) 
#include "Math/GenVector/GenVector_exception.h"
#include "Math/GenVector/Polar3D.h"
#include "Math/GenVector/CylindricalEta3D.h"
#endif
 

namespace ROOT { 

  namespace Math { 

  /** 
      Class describing a cylindrical coordinate system based on eta (pseudorapidity) instead of z.  
      The base coordinates are rho (transverse component) , eta and phi
  
      @ingroup GenVector
   */ 

template <class T> 
class CylindricalEta3D { 

public : 

  typedef T Scalar;

  /**
     Default constructor with rho=eta=phi=0
   */
  CylindricalEta3D() : fRho(0), fEta(0), fPhi(0) {  }

  /**
     Construct from rho eta and phi values
   */
  CylindricalEta3D(Scalar rho, Scalar eta, Scalar phi) :  
  				fRho(rho), fEta(eta), fPhi(phi) {  }

  /**
     Construct from any Vector or coordinate system implementing 
     Rho(), Eta() and Phi()
    */ 
  template <class CoordSystem > 
  explicit CylindricalEta3D( const CoordSystem & v ) : 
    	fRho(v.Rho() ),  fEta(v.Eta() ),  fPhi(v.Phi() )  
  {  
    static Scalar bigEta = 
    			-.3 *std::log(std::numeric_limits<Scalar>::epsilon());
    if ( fabs(fEta) > bigEta ) {
      fRho *= v.Z()/Z(); // This gives a small absolute adjustment in rho,
    		 	 // which, for large eta, results in a significant
			 // improvement in the faithfullness of reproducing z.
    }
  } 

  // no reason for a custom destructor  ~Cartesian3D() {}

  /**
     Set internal data based on an array of 3 Scalar numbers
   */ 
  void SetCoordinates( const Scalar src[] ) 
  			{ fRho=src[0]; fEta=src[1]; fPhi=src[2]; }

  /**
     get internal data into an array of 3 Scalar numbers
   */ 
  void GetCoordinates( Scalar dest[] ) const 
  			{ dest[0] = fRho; dest[1] = fEta; dest[2] = fPhi; }

  /**
     Set internal data based on 3 Scalar numbers
   */ 
  void SetCoordinates(Scalar  rho, Scalar  eta, Scalar  phi) 
  			{ fRho=rho; fEta=eta; fPhi=phi; }

  /**
     get internal data into 3 Scalar numbers
   */ 
  void GetCoordinates(Scalar& rho, Scalar& eta, Scalar& phi) const 
  			{rho=fRho; eta=fEta; phi=fPhi;}  				

  private:
    inline static double pi() { return 3.14159265358979323; } 
  public:
   
  // accessors
 
  T Rho()   const { return fRho; }
  T Eta()   const { return fEta; } 
  T Phi()   const { return fPhi; }
  T X()     const { return fRho*std::cos(fPhi); }
  T Y()     const { return fRho*std::sin(fPhi); }
  T Z()     const { return fRho >  0 ? fRho*std::sinh(fEta) : 
                           fEta == 0 ? 0                    :
                           fEta >  0 ? fEta - etaMax<T>()   :
		                       fEta + etaMax<T>()   ; }
  T R()     const { return fRho > 0          ? fRho*std::cosh(fEta) :
  		           fEta >  etaMax<T>() ?  fEta - etaMax<T>()   :
 		           fEta < -etaMax<T>() ? -fEta - etaMax<T>()   :
			                             0		   ; }
  T Mag2()  const { return R()*R();              }
  T Perp2() const { return fRho*fRho;            }
  T Theta() const { return  fRho >  0 ? 2* std::atan( std::exp( - fEta ) ) :
  			   (fEta >= 0 ? 0 :
			    pi() );  }
 
  // setters (only for data members) 

  /**
     set all the data members ( rho, eta, phi) 
   */ 
  void setValues(T rho, T eta, T phi) { 
    fRho = rho;  
    fEta = eta;  
    fPhi = phi;   
  }
  
  /** 
      set the rho coordinate value keeping eta and phi constant
   */ 
  void SetRho(T rho) { 
        fRho = rho;      
  }

  /** 
      set the eta coordinate value keeping rho and phi constant
   */ 
  void SetEta(T eta) { 
        fEta = eta;      
  }

  /** 
      set the phi coordinate value keeping rho and eta constant
   */ 
  void SetPhi(T phi) { 
        fPhi = phi;      
  }

  /**
     scale by a scalar quantity a -- 
     for cylindrical eta coords, as long as a >= 0, only rho changes!
  */ 
  void Scale (T a) { 
    if (a < 0) {
      Negate();
      a = -a;
    }
    // angles do not change when scaling by a positive quantity
    if (fRho > 0) {
      fRho *= a;   
    } else if ( fEta >  etaMax<T>() ) {
      fEta =  ( fEta-etaMax<T>())*a + etaMax<T>();
    } else if ( fEta < -etaMax<T>() ) {  
      fEta =  ( fEta+etaMax<T>())*a - etaMax<T>();
    } // when rho==0 and eta is not above etaMax, vector represents 0 
      // and remains unchanged
  }

  /**
     negate the vector
  */ 
  void Negate ( ) { 
    fPhi = ( fPhi > 0 ? fPhi - pi() : fPhi + pi() );
    fEta = -fEta;
  }

  // assignment operators
  /**
    generic assignment operator from any coordinate system 
  */ 
  template <class CoordSystem > 
  CylindricalEta3D & operator= ( const CoordSystem & c ) { 
    fRho = c.Rho();  
    fEta = c.Eta(); 
    fPhi = c.Phi(); 
    return *this;
  }

  /**
    Exact component-by-component equality 
    Note: Peculiar representaions of the zero vector such as (0,1,0) will
    not test as equal to one another.     
    */  
  bool operator==(const CylindricalEta3D & rhs) const {
    return fRho == rhs.fRho && fEta == rhs.fEta && fPhi == rhs.fPhi;
  }
  bool operator!= (const CylindricalEta3D & rhs) const 
  						{return !(operator==(rhs));}
  

  // ============= Compatibility section ==================
  
  // The following make this coordinate system look enough like a CLHEP
  // vector that an assignment member template can work with either
  T x() const { return X();}
  T y() const { return Y();}
  T z() const { return Z(); } 
  
  // ============= Specializations for improved speed ==================

  // (none)

#if defined(__MAKECINT__) || defined(G__DICTIONARY) 

  // ====== Set member functions for coordinates in other systems =======

  void SetX(Scalar x) {  
    GenVector_exception e("CylindricalEta3D::SetX() is not supposed to be called");
    Throw(e);
    Cartesian3D<Scalar> v(*this); v.SetX(x); 
    *this = CylindricalEta3D<Scalar>(v);
  }
  void SetY(Scalar y) {  
    GenVector_exception e("CylindricalEta3D::SetY() is not supposed to be called");
    Throw(e);
    Cartesian3D<Scalar> v(*this); v.SetY(y); 
    *this = CylindricalEta3D<Scalar>(v);
  }
  void SetZ(Scalar z) {  
    GenVector_exception e("CylindricalEta3D::SetZ() is not supposed to be called");
    Throw(e);
    Cartesian3D<Scalar> v(*this); v.SetZ(z); 
    *this = CylindricalEta3D<Scalar>(v);
  }
  void SetR(Scalar r) {  
    GenVector_exception e("CylindricalEta3D::SetR() is not supposed to be called");
    Throw(e);
    Polar3D<Scalar> v(*this); v.SetR(r); 
    *this = CylindricalEta3D<Scalar>(v);
  }
  void SetTheta(Scalar theta) {  
    GenVector_exception e("CylindricalEta3D::SetTheta() is not supposed to be called");
    Throw(e);
    Polar3D<Scalar> v(*this); v.SetTheta(theta); 
    *this = CylindricalEta3D<Scalar>(v);
  }

#endif


private:
  T fRho;
  T fEta;
  T fPhi;

};

  } // end namespace Math

} // end namespace ROOT


#endif /* ROOT_Math_GenVector_CylindricalEta3D  */