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/// \file OpNovice/src/OpNovicePrimaryGeneratorAction.cc
/// \brief Implementation of the OpNovicePrimaryGeneratorAction class
//
//
//
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#include "OpNovicePrimaryGeneratorAction.hh"
#include "OpNovicePrimaryGeneratorMessenger.hh"
#include "G4Event.hh"
#include "G4ParticleDefinition.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"

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OpNovicePrimaryGeneratorAction::OpNovicePrimaryGeneratorAction()
  : G4VUserPrimaryGeneratorAction()
  , fParticleGun(nullptr)
{
  G4int n_particle = 1;
  fParticleGun     = new G4ParticleGun(n_particle);
  // create a messenger for this class
  fGunMessenger = new OpNovicePrimaryGeneratorMessenger(this);
  // default kinematic
  //
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  G4ParticleDefinition* particle = particleTable->FindParticle("e+");

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

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

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void OpNovicePrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  fParticleGun->GeneratePrimaryVertex(anEvent);
}

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

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void OpNovicePrimaryGeneratorAction::SetOptPhotonPolar(G4double angle)
{
  if(fParticleGun->GetParticleDefinition()->GetParticleName() !=
     "opticalphoton")
  {
    G4ExceptionDescription ed;
    ed << "Warning: the particleGun is not an opticalphoton";
    G4Exception("OpNovicePrimaryGeneratorAction::SetOptPhotonPolar()",
                "OpNovice_010", JustWarning, ed);
    return;
  }

  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);
}
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