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

#include "PrimaryGeneratorAction.hh"

#include "PrimaryGeneratorMessenger.hh"

#include "G4Event.hh"
#include "G4OpticalPhoton.hh"
#include "G4ParticleDefinition.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

PrimaryGeneratorAction::PrimaryGeneratorAction()
  : G4VUserPrimaryGeneratorAction(), fParticleGun(nullptr)
{
  G4int n_particle = 1;
  fParticleGun = new G4ParticleGun(n_particle);

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

  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  G4ParticleDefinition* particle = particleTable->FindParticle("e+");

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

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

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

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

void PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  if (fRandomDirection) {
    G4double theta = CLHEP::halfpi * G4UniformRand();
    G4double phi = CLHEP::twopi * G4UniformRand();
    G4double x = std::cos(theta);
    G4double y = std::sin(theta) * std::sin(phi);
    G4double z = std::sin(theta) * std::cos(phi);
    G4ThreeVector dir(x, y, z);
    fParticleGun->SetParticleMomentumDirection(dir);
  }
  if (fParticleGun->GetParticleDefinition() == G4OpticalPhoton::OpticalPhotonDefinition()) {
    if (fPolarized)
      SetOptPhotonPolar(fPolarization);
    else
      SetOptPhotonPolar();
  }
  fParticleGun->GeneratePrimaryVertex(anEvent);
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

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

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

void PrimaryGeneratorAction::SetOptPhotonPolar(G4double angle)
{
  if (fParticleGun->GetParticleDefinition() != G4OpticalPhoton::OpticalPhotonDefinition()) {
    G4ExceptionDescription ed;
    ed << "The particleGun is not an opticalphoton.";
    G4Exception("PrimaryGeneratorAction::SetOptPhotonPolar", "OpNovice2_004", JustWarning, ed);
    return;
  }

  fPolarized = true;
  fPolarization = angle;

  G4ThreeVector normal(1., 0., 0.);
  G4ThreeVector kphoton = fParticleGun->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;
  fParticleGun->SetParticlePolarization(polar);
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void PrimaryGeneratorAction::SetRandomDirection(G4bool val)
{
  fRandomDirection = val;
}
