//
// ********************************************************************
// * 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.          *
// ********************************************************************
//
// This is the modified version of the example electromagnetic/TestEm7/src/PrimaryGeneratorAction.cc

#include "PrimaryGeneratorAction.hh"
#include "DetectorConstruction.hh"
#include "PrimaryGeneratorMessenger.hh"
#include "G4Event.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4ParticleDefinition.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"

PrimaryGeneratorAction::PrimaryGeneratorAction(DetectorConstruction* det)
:G4VUserPrimaryGeneratorAction(),                                              
 fParticleGun(0),
 fDetector(det),
 fRndmBeam(0),
 fEbeamCumul(0),       
 fGunMessenger(0)
{
  fParticleGun  = new G4ParticleGun(1);
  G4ParticleDefinition* particle
           = G4ParticleTable::GetParticleTable()->FindParticle("proton");
  fParticleGun->SetParticleDefinition(particle);
  fParticleGun->SetParticleEnergy(160*MeV);  
  fParticleGun->SetParticleMomentumDirection(G4ThreeVector(1.,0.,0.));
    
  //create a messenger for this class
  fGunMessenger = new PrimaryGeneratorMessenger(this);  
}

PrimaryGeneratorAction::~PrimaryGeneratorAction()
{
  delete fParticleGun;
  delete fGunMessenger;  
}

void PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  //this function is called at the begining of event
  G4double x0 = -0.5*(fDetector->GetAbsorSizeX());
  G4double y0 = 0.*cm, z0 = 0.*cm;
    
  //randomize the beam, if requested.
  if (fRndmBeam > 0.) 
    {
      if (fRndmBeam > fDetector->GetAbsorSizeYZ())
        fRndmBeam = fDetector->GetAbsorSizeYZ(); 
      G4double rbeam = 0.5*fRndmBeam;
      y0 = (2*G4UniformRand()-1.)*rbeam;
      z0 = (2*G4UniformRand()-1.)*rbeam;
    }
  fParticleGun->SetParticlePosition(G4ThreeVector(x0,y0,z0));  
  fParticleGun->GeneratePrimaryVertex(anEvent);
  
  fEbeamCumul += fParticleGun->GetParticleEnergy(); 
}