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/// \file SplitProcess.cc
/// \brief Implementation of the SplitProcess class
///
/// Implementation of the variance reduction particle split 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
// The Geant4-DNA web site is available at http://geant4-dna.org
//

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#include "SplitProcess.hh"

#include "UserTrackInformation.hh"

#include "G4LogicalVolume.hh"
#include "G4Region.hh"
#include "G4RegionStore.hh"
#include "G4TouchableHandle.hh"
#include "G4Track.hh"
#include "G4VParticleChange.hh"

#include <vector>

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SplitProcess::SplitProcess(G4String regName, G4int nsplit) : fRegionName(regName), fNSplit(nsplit)
{
  fRegion = G4RegionStore::GetInstance()->FindOrCreateRegion(fRegionName);
}

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SplitProcess::~SplitProcess() {}

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G4VParticleChange* SplitProcess::PostStepDoIt(const G4Track& track, const G4Step& step)
{
  G4VParticleChange* particleChange(0);

  if (step.GetPreStepPoint()->GetTouchableHandle()->GetVolume()->GetLogicalVolume()->GetRegion()
      != fRegion)
  {
    particleChange = pRegProcess->PostStepDoIt(track, step);
    assert(0 != particleChange);
    return particleChange;
  }

  if (fNSplit == 1) {
    particleChange = pRegProcess->PostStepDoIt(track, step);
    assert(0 != particleChange);
    return particleChange;
  }

  UserTrackInformation* parentInformation =
    (UserTrackInformation*)(step.GetTrack()->GetUserInformation());
  G4int initialSplitTrackID = parentInformation->GetSplitTrackID();

  if (initialSplitTrackID > 1) {
    particleChange = pRegProcess->PostStepDoIt(track, step);
    assert(0 != particleChange);
    return particleChange;
  }

  G4double weight = track.GetWeight() / fNSplit;
  G4int splitTrackID = 3;

  std::vector<G4Track*> secondaries;
  std::vector<G4int> vSplitTrack;

  for (int i = 0; i < fNSplit; i++) {
    particleChange = pRegProcess->PostStepDoIt(track, step);
    assert(0 != particleChange);
    particleChange->SetVerboseLevel(0);
    G4Track* newTrack = new G4Track(*(particleChange->GetSecondary(0)));

    secondaries.push_back(newTrack);
    vSplitTrack.push_back(splitTrackID);

    splitTrackID++;
  }

  parentInformation->SetSplitTrackID(2);

  particleChange->SetNumberOfSecondaries(secondaries.size());
  particleChange->SetSecondaryWeightByProcess(true);

  std::vector<G4Track*>::iterator iter = secondaries.begin();
  G4int i = 0;
  while (iter != secondaries.end()) {
    G4Track* newTrack = *iter;
    newTrack->SetWeight(weight);

    UserTrackInformation* secondaryInformation = new UserTrackInformation();
    secondaryInformation->SetSplitTrackID(vSplitTrack[i]);
    newTrack->SetUserInformation(secondaryInformation);

    particleChange->AddSecondary(newTrack);

    iter++;
    i++;
  }

  return particleChange;
}

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