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// $Id: ExN06PrimaryGeneratorAction.cc,v 1.6 2006/06/29 17:54:27 gunter Exp $
// GEANT4 tag $Name: geant4-09-03-cand-01 $
//
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#include "ExN06PrimaryGeneratorAction.hh"
#include "ExN06PrimaryGeneratorMessenger.hh"

#include "Randomize.hh"

#include "G4Event.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4ParticleDefinition.hh"

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ExN06PrimaryGeneratorAction::ExN06PrimaryGeneratorAction()
{
  G4int n_particle = 1;
  particleGun = new G4ParticleGun(n_particle);
  
  //create a messenger for this class
  gunMessenger = new ExN06PrimaryGeneratorMessenger(this);
  
  //default kinematic
  //
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  G4ParticleDefinition* particle = particleTable->FindParticle("e+");

  particleGun->SetParticleDefinition(particle);
  particleGun->SetParticleTime(0.0*ns);
  particleGun->SetParticlePosition(G4ThreeVector(0.0*cm,0.0*cm,0.0*cm));
  particleGun->SetParticleMomentumDirection(G4ThreeVector(1.,0.,0.));
  particleGun->SetParticleEnergy(500.0*keV);
}

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ExN06PrimaryGeneratorAction::~ExN06PrimaryGeneratorAction()
{
  delete particleGun;
  delete gunMessenger;
}

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void ExN06PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  particleGun->GeneratePrimaryVertex(anEvent);
}

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void ExN06PrimaryGeneratorAction::SetOptPhotonPolar()
{
 G4double angle = G4UniformRand() * 360.0*deg;
 SetOptPhotonPolar(angle);
}

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void ExN06PrimaryGeneratorAction::SetOptPhotonPolar(G4double angle)
{
 if (particleGun->GetParticleDefinition()->GetParticleName() != "opticalphoton")
   {
     G4cout << "--> warning from PrimaryGeneratorAction::SetOptPhotonPolar() :"
               "the particleGun is not an opticalphoton" << G4endl;
     return;
   }
     	       
 G4ThreeVector normal (1., 0., 0.);
 G4ThreeVector kphoton = particleGun->GetParticleMomentumDirection();
 G4ThreeVector product = normal.cross(kphoton); 
 G4double modul2       = product*product;
 
 G4ThreeVector e_perpend (0., 0., 1.);
 if (modul2 > 0.) e_perpend = (1./std::sqrt(modul2))*product; 
 G4ThreeVector e_paralle    = e_perpend.cross(kphoton);
 
 G4ThreeVector polar = std::cos(angle)*e_paralle + std::sin(angle)*e_perpend;
 particleGun->SetParticlePolarization(polar);
}

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