//
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//
// $Id$
//
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#include "PrimaryGeneratorAction.hh"

#include "PrimaryGeneratorMessenger.hh"
#include "DetectorConstruction.hh"

#include "G4SystemOfUnits.hh"
#include "G4Event.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4ParticleDefinition.hh"
#include "Randomize.hh"

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PrimaryGeneratorAction::PrimaryGeneratorAction(DetectorConstruction* det)
:Detector(det)
{
  G4int n_particle = 1;
  particleGun  = new G4ParticleGun(n_particle);
  SetDefaultKinematic();
  beam = 0.*mm;
  
  //create a messenger for this class
  gunMessenger = new PrimaryGeneratorMessenger(this);
}

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

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void PrimaryGeneratorAction::SetDefaultKinematic()
{
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  G4String particleName;
  G4ParticleDefinition* particle
                    = particleTable->FindParticle(particleName="e-");
  particleGun->SetParticleDefinition(particle);
  particleGun->SetParticleMomentumDirection(G4ThreeVector(1.,0.,0.));
  particleGun->SetParticleEnergy(1.*GeV);
  G4double position = -0.5*(Detector->GetWorldSizeX());
  particleGun->SetParticlePosition(G4ThreeVector(position,0.*mm,0.*mm));
}

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void PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  //this function is called at the begining of event
  //
  //randomize beam, if requested.
  //
  if (beam > 0.) 
    {
      G4ThreeVector position = particleGun->GetParticlePosition();    
      G4double maxYZ = 0.49*(Detector->GetCalorSizeYZ());
      G4double x0 = position.x();
      G4double y0 = position.y() + (G4UniformRand()-0.5)*beam;
      G4double z0 = position.z() + (G4UniformRand()-0.5)*beam;
      if (std::abs(y0) > maxYZ) y0 = maxYZ;
      if (std::abs(z0) > maxYZ) z0 = maxYZ;      
      particleGun->SetParticlePosition(G4ThreeVector(x0,y0,z0));
      particleGun->GeneratePrimaryVertex(anEvent);
      particleGun->SetParticlePosition(position);      
    }
  else  particleGun->GeneratePrimaryVertex(anEvent);
}

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