//
// ********************************************************************
// * License and Disclaimer                                           *
// *                                                                  *
// * The  Geant4 software  is  copyright of the Copyright Holders  of *
// * the Geant4 Collaboration.  It is provided  under  the terms  and *
// * conditions of the Geant4 Software License,  included in the file *
// * LICENSE and available at  http://cern.ch/geant4/license .  These *
// * include a list of copyright holders.                             *
// *                                                                  *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work  make  any representation or  warranty, express or implied, *
// * regarding  this  software system or assume any liability for its *
// * use.  Please see the license in the file  LICENSE  and URL above *
// * for the full disclaimer and the limitation of liability.         *
// *                                                                  *
// * This  code  implementation is the result of  the  scientific and *
// * technical work of the GEANT4 collaboration.                      *
// * By using,  copying,  modifying or  distributing the software (or *
// * any work based  on the software)  you  agree  to acknowledge its *
// * use  in  resulting  scientific  publications,  and indicate your *
// * acceptance of all terms of the Geant4 Software license.          *
// ********************************************************************
//
// G4RToEConvForPositron class implementation
//
// Author: H.Kurashige, 05 October 2002 - First implementation
// --------------------------------------------------------------------

#include "G4RToEConvForPositron.hh"
#include "G4ParticleDefinition.hh"
#include "G4ParticleTable.hh"
#include "G4Material.hh"
#include "G4PhysicsLogVector.hh"

#include "G4ios.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"

// --------------------------------------------------------------------
G4RToEConvForPositron::G4RToEConvForPositron() 
  : G4VRangeToEnergyConverter()
{    
  theParticle = G4ParticleTable::GetParticleTable()->FindParticle("e+");
  if (theParticle == nullptr)
  {
#ifdef G4VERBOSE
    if (GetVerboseLevel()>0)
    {
      G4cout << "G4RToEConvForPositron::G4RToEConvForPositron() - ";
      G4cout << "Positron is not defined !!" << G4endl;
    }
#endif
  }
  else
  {
    Mass = theParticle->GetPDGMass();
  }
}

// --------------------------------------------------------------------
G4RToEConvForPositron::~G4RToEConvForPositron()
{ 
}

// **********************************************************************
// ************************* ComputeLoss ********************************
// **********************************************************************
G4double G4RToEConvForPositron::ComputeLoss(G4double AtomicNumber,
                                            G4double KineticEnergy) 
{
  const G4double cbr1=0.02, cbr2=-5.7e-5, cbr3=1., cbr4=0.072;
  const G4double Tlow=10.*keV, Thigh=1.*GeV;

  // calculate dE/dx for electrons
  if( std::fabs(AtomicNumber-Z)>0.1 )
  {
    Z = AtomicNumber;
    taul = Tlow/Mass;
    ionpot = 1.6e-5*MeV*std::exp(0.9*std::log(Z))/Mass;
    ionpotlog = std::log(ionpot);
  } 

  G4double tau = KineticEnergy/Mass;
  G4double dEdx;

  if(tau<taul)
  {
    G4double t1 = taul+1.;
    G4double t2 = taul+2.;
    G4double tsq = taul*taul;
    G4double beta2 = taul*t2/(t1*t1);
    G4double     f = 2.*std::log(taul)
                   -(6.*taul+1.5*tsq-taul*(1.-tsq/3.)/t2
                     -tsq*(0.5-tsq/12.)/(t2*t2))/(t1*t1);
    dEdx = (std::log(2.*taul+4.)-2.*ionpotlog+f)/beta2;
    dEdx = twopi_mc2_rcl2*Z*dEdx;
    G4double clow = dEdx*std::sqrt(taul);
    dEdx = clow/std::sqrt(KineticEnergy/Mass);
  }
  else
  {
    G4double t1 = tau+1.;
    G4double t2 = tau+2.;
    G4double tsq = tau*tau;
    G4double beta2 = tau*t2/(t1*t1);
    G4double f = 2.*std::log(tau)
               - (6.*tau+1.5*tsq-tau*(1.-tsq/3.)/t2
                  -tsq*(0.5-tsq/12.)/(t2*t2))/(t1*t1);
    dEdx = (std::log(2.*tau+4.)-2.*ionpotlog+f)/beta2;
    dEdx = twopi_mc2_rcl2*Z*dEdx;

    // loss from bremsstrahlung follows
    G4double cbrem = (cbr1+cbr2*Z)
                   * (cbr3+cbr4*std::log(KineticEnergy/Thigh));
    cbrem = Z*(Z+1.)*cbrem*tau/beta2;
    cbrem *= bremfactor;
    dEdx += twopi_mc2_rcl2*cbrem;
  }
  return dEdx;
}