//
// ********************************************************************
// * License and Disclaimer                                           *
// *                                                                  *
// * The  Geant4 software  is  copyright of the Copyright Holders  of *
// * the Geant4 Collaboration.  It is provided  under  the terms  and *
// * conditions of the Geant4 Software License,  included in the file *
// * LICENSE and available at  http://cern.ch/geant4/license .  These *
// * include a list of copyright holders.                             *
// *                                                                  *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work  make  any representation or  warranty, express or implied, *
// * regarding  this  software system or assume any liability for its *
// * use.  Please see the license in the file  LICENSE  and URL above *
// * for the full disclaimer and the limitation of liability.         *
// *                                                                  *
// * This  code  implementation is the result of  the  scientific and *
// * technical work of the GEANT4 collaboration.                      *
// * By using,  copying,  modifying or  distributing the software (or *
// * any work based  on the software)  you  agree  to acknowledge its *
// * use  in  resulting  scientific  publications,  and indicate your *
// * acceptance of all terms of the Geant4 Software license.          *
// ********************************************************************
//
/// \file PrimaryGeneratorAction.cc
/// \brief Implementation of the B2::PrimaryGeneratorAction class

#include "PrimaryGeneratorAction.hh"

#include "G4Box.hh"
#include "G4LogicalVolume.hh"
#include "G4LogicalVolumeStore.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4SystemOfUnits.hh"
#include "globals.hh"

namespace B2
{

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

PrimaryGeneratorAction::PrimaryGeneratorAction()
{
  G4int nofParticles = 1;
  fParticleGun = new G4ParticleGun(nofParticles);

  // default particle kinematic

  G4ParticleDefinition* particleDefinition =
    G4ParticleTable::GetParticleTable()->FindParticle("proton");

  fParticleGun->SetParticleDefinition(particleDefinition);
  fParticleGun->SetParticleMomentumDirection(G4ThreeVector(0., 0., 1.));
  fParticleGun->SetParticleEnergy(3.0 * GeV);
}

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

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

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

void PrimaryGeneratorAction::GeneratePrimaries(G4Event* event)
{
  // This function is called at the begining of event

  // In order to avoid dependence of PrimaryGeneratorAction
  // on DetectorConstruction class we get world volume
  // from G4LogicalVolumeStore.

  G4double worldZHalfLength = 0;
  G4LogicalVolume* worldLV = G4LogicalVolumeStore::GetInstance()->GetVolume("World");
  G4Box* worldBox = nullptr;
  if (worldLV) worldBox = dynamic_cast<G4Box*>(worldLV->GetSolid());
  if (worldBox)
    worldZHalfLength = worldBox->GetZHalfLength();
  else {
    G4cerr << "World volume of box not found." << G4endl;
    G4cerr << "Perhaps you have changed geometry." << G4endl;
    G4cerr << "The gun will be place in the center." << G4endl;
  }

  // Starting a primary particle close to the world boundary.
  //
  fParticleGun->SetParticlePosition(G4ThreeVector(0., 0., -worldZHalfLength + 1 * um));

  fParticleGun->GeneratePrimaryVertex(event);
}

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

}  // namespace B2
