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//
/// \file PrimaryGeneratorAction.cc
/// \brief Implementation of the PrimaryGeneratorAction class
//
//

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

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PrimaryGeneratorAction::
PrimaryGeneratorAction( const DetectorConstruction* pDetector ) :
  fPointerDetectorConstruction( pDetector )
{
  G4int n_particle = 1;
  fParticleGun = new G4ParticleGun( n_particle );
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  //***LOOKHERE*** Default particle and energy
  fParticleGun->SetParticleDefinition( particleTable->FindParticle( "geantino" ) );
  fParticleGun->SetParticleEnergy( 10.0*GeV );
  SetGunPosition();
}

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

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void PrimaryGeneratorAction::SetGunPosition() const {
  // Shoot the particle in the middle between the world and the target layer
  G4double targetThickness =
    ( fPointerDetectorConstruction ? fPointerDetectorConstruction->GetThickness() : 0.0 );
  G4double gunPosition = -0.55*targetThickness;  //***LOOKHERE*** default gun position
                                                 //               along the z-axis
  G4cout << G4endl << "PrimaryGenerationAction::SetGunPosition() : gun position along z = " 
         << gunPosition << " mm " << G4endl << G4endl;  
  fParticleGun->SetParticlePosition( G4ThreeVector( 0.0, 0.0, gunPosition ) );
}

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void PrimaryGeneratorAction::GeneratePrimaries( G4Event* anEvent ) {
  G4ThreeVector v( 0.0, 0.0, 1.0 );  //***LOOKHERE*** default shoot along the z-axis
  fParticleGun->SetParticleMomentumDirection( v );
  fParticleGun->GeneratePrimaryVertex( anEvent );
}

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