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

// This example is provided by the Geant4-DNA collaboration
// Any report or published results obtained using the Geant4-DNA software
// shall cite the following Geant4-DNA collaboration publication:
// Med. Phys. 37 (2010) 4692-4708
// Delage et al. PDB4DNA: implementation of DNA geometry from the Protein Data
//                  Bank (PDB) description for Geant4-DNA Monte-Carlo
//                  simulations (submitted to Comput. Phys. Commun.)
// The Geant4-DNA web site is available at http://geant4-dna.org
//
//

#include "PrimaryGeneratorAction.hh"

#include "G4Box.hh"
#include "G4Event.hh"
#include "G4LogicalVolume.hh"
#include "G4LogicalVolumeStore.hh"
#include "G4ParticleDefinition.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4PhysicalConstants.hh"
#include "G4PhysicalVolumeStore.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"

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

PrimaryGeneratorAction::PrimaryGeneratorAction() : G4VUserPrimaryGeneratorAction()
{
  G4int n_particle = 1;
  fpParticleGun = new G4ParticleGun(n_particle);

  // default particle kinematic

  G4ParticleDefinition* particle = G4ParticleTable::GetParticleTable()->FindParticle("e-");
  fpParticleGun->SetParticleDefinition(particle);
  fpParticleGun->SetParticleMomentumDirection(G4ThreeVector(0., 0., 1.));
  fpParticleGun->SetParticleEnergy(0.1 * MeV);
  fpParticleGun->SetParticlePosition(G4ThreeVector(0. * nm, 0. * nm, 0. * nm));
}

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

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

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

void PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  // In order to avoid dependence of PrimaryGeneratorAction
  // on DetectorConstruction class we get world volume
  // from G4LogicalVolumeStore
  //
  G4double boundXHalfLength = 0;
  G4double boundYHalfLength = 0;
  G4double boundZHalfLength = 0;

  G4VPhysicalVolume* boundPV = G4PhysicalVolumeStore::GetInstance()->GetVolume("boundingPV");

  G4ThreeVector boundPos;
  if (boundPV) {
    boundPos = boundPV->GetTranslation();
  }

  G4LogicalVolume* boundLV = G4LogicalVolumeStore::GetInstance()->GetVolume("BoundingLV");

  G4Box* boundBox = 0;
  if (boundLV) {
    boundBox = dynamic_cast<G4Box*>(boundLV->GetSolid());
  }

  if (boundBox) {
    boundXHalfLength = boundBox->GetXHalfLength();
    boundYHalfLength = boundBox->GetYHalfLength();
    boundZHalfLength = boundBox->GetZHalfLength();

    // Set gun position
    // Select a starting position on a sphere including the target volume
    //
    G4double radius =
      std::sqrt(boundXHalfLength * boundXHalfLength + boundYHalfLength * boundYHalfLength
                + boundZHalfLength * boundZHalfLength);
    G4double cosTheta = 2 * G4UniformRand() - 1;
    G4double sinTheta = std::sqrt(1. - cosTheta * cosTheta);
    G4double phi = twopi * G4UniformRand();

    G4ThreeVector positionStart(boundPos.x() + radius * sinTheta * std::cos(phi),
                                boundPos.y() + radius * sinTheta * std::sin(phi),
                                boundPos.z() + radius * cosTheta);

    fpParticleGun->SetParticlePosition(positionStart);

    // Set gun direction
    // To compute the direction, select a point inside the target volume
    //
    G4ThreeVector positionDir(boundPos.x() + boundXHalfLength * (2 * G4UniformRand() - 1),
                              boundPos.y() + boundYHalfLength * (2 * G4UniformRand() - 1),
                              boundPos.z() + boundZHalfLength * (2 * G4UniformRand() - 1));

    fpParticleGun->SetParticleMomentumDirection((positionDir - positionStart).unit());
  }
  else {
    G4cerr << "Bounding volume not found." << G4endl;
    G4cerr << "Default particle kinematic used" << G4endl;
  }

  fpParticleGun->GeneratePrimaryVertex(anEvent);
}
