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

#include "PrimaryGeneratorAction.hh"

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

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

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PrimaryGeneratorAction::PrimaryGeneratorAction(DetectorConstruction* det) : fDetector(det)
{
  G4int n_particle = 1;
  fParticleGun = new G4ParticleGun(n_particle);
  SetDefaultKinematic();

  // create a messenger for this class
  fGunMessenger = new PrimaryGeneratorMessenger(this);
}

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

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void PrimaryGeneratorAction::SetDefaultKinematic()
{
  // default particle kinematic
  //
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  G4ParticleDefinition* particle = particleTable->FindParticle("e-");
  fParticleGun->SetParticleDefinition(particle);
  fParticleGun->SetParticleMomentumDirection(G4ThreeVector(1., 0., 0.));
  fParticleGun->SetParticleEnergy(30. * MeV);
  G4double x0 = -0.4999 * (fDetector->GetWorldSizeX());
  fParticleGun->SetParticlePosition(G4ThreeVector(x0, 0.0, 0.0));
}

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

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