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//
// $Id: G4SCProcessorStand.cc,v 1.2 2004/12/01 19:37:15 vnivanch Exp $
// GEANT4 tag $Name: geant4-07-01 $
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:     G4SCProcessorStand
//
// Author:        Vladimir Ivanchenko
//
// Creation date: 10.05.2002
//
// Modifications:
//
// 09-12-02 remove warning (V.Ivanchenko)
// 23-12-02 change interface in order to move to cut per region (V.Ivanchenko)
// 26-12-02 Secondary production moved to derived classes (V.Ivanchenko)
// 27-01-03 Make models region aware (V.Ivanchenko)
// 13-02-03 Add name (V.Ivanchenko)
//
//
// -------------------------------------------------------------------
//
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#include "G4SCProcessorStand.hh"
#include "G4Electron.hh"
#include "G4Positron.hh"
#include "G4Navigator.hh"
#include "G4TransportationManager.hh"
#include "G4EmModelManager.hh"
#include "G4MaterialCutsCouple.hh"
#include "G4VEmModel.hh"
#include "Randomize.hh"
#include "G4Step.hh"

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using namespace std;

G4SCProcessorStand::G4SCProcessorStand(const G4String& nam)
  : G4VSubCutoffProcessor(nam),
    theLambdaSubTable(0),
    thePositron(G4Positron::Positron())
{}

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G4SCProcessorStand::~G4SCProcessorStand()
{}

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void G4SCProcessorStand::Initialise(const G4ParticleDefinition* p,
                                    const G4ParticleDefinition* sp,
                                    const G4DataVector* vCuts,
                                    const G4DataVector* vSubCuts)
{
  particle = p;
  secondaryParticle = sp;
  navigator = (G4TransportationManager::GetTransportationManager())
                                       ->GetNavigatorForTracking();
  theCuts = vCuts;
  theSubCuts = vSubCuts;
  initialMass= particle->GetPDGMass();

}

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vector<G4Track*>*  G4SCProcessorStand::SampleSecondaries(
                    const G4Step&    step,
			  G4double&  tmax,
                          G4double&  meanLoss,
                          G4VEmModel* currentModel)
{
  G4bool b;
  const G4Track* track = step.GetTrack();
  const G4MaterialCutsCouple* couple = track->GetMaterialCutsCouple();

  size_t index = couple->GetIndex();
  G4double subcut = (*theSubCuts)[index];

  if(subcut >= tmax) return 0;

  G4double cut = (*theCuts)[index];
  G4double rcut   = couple->GetProductionCuts()->GetProductionCut(1);


  const G4DynamicParticle* dp = track->GetDynamicParticle();
  G4double ekin  = dp->GetKineticEnergy();
  G4double effChargeFactor = 1.0;
  G4double massRatio = 1.0;
  G4double mass = initialMass;

  if(dp->GetDefinition() != particle) {
    mass = dp->GetMass();
    massRatio = initialMass/mass;
    G4double q = particle->GetPDGCharge()/dp->GetCharge();
    effChargeFactor = q*q;
  }

  G4double cross = (*theLambdaSubTable)[index]->GetValue(ekin*massRatio, b);

  if(0.0 >= cross) return 0;

  G4StepPoint* pre = step.GetPreStepPoint();
  G4double presafety  = pre->GetSafety();
  G4ThreeVector postpoint = step.GetPostStepPoint()->GetPosition();
  G4double postsafety = navigator->ComputeSafety(postpoint);
  G4double safety = min(presafety,postsafety);
  if(safety >= rcut) return 0;


  G4ThreeVector prepoint = pre->GetPosition();
  G4ThreeVector dr = postpoint - prepoint;
  G4double pretime = step.GetPreStepPoint()->GetGlobalTime();
  G4double fragment = 0.0;
  G4double dt = 0.0;
  G4double length = step.GetStepLength();
  G4double inv_v = (ekin + mass)/(c_light*dp->GetTotalMomentum());

  vector<G4Track*>* vtr = new vector<G4Track*>;

  do {

    G4double del = G4UniformRand()*effChargeFactor / cross;
    fragment += del/length;
    if (fragment > 1.0) break;

    dt += del * inv_v;
    vector<G4DynamicParticle*>* newp =
           currentModel->SampleSecondaries(couple, dp, subcut, cut);
    if (newp) {

      G4DynamicParticle* p;
      G4int nNew = newp->size();
      for (G4int i=0; i<nNew; i++) {

	p = (*newp)[i];
        G4double e = p->GetKineticEnergy();
        if (p->GetDefinition() == thePositron) e += electron_mass_c2;

        if (e <= meanLoss) {
          meanLoss  -= e;
          G4Track* t = new G4Track(p, pretime + dt, prepoint + fragment*dr);
          vtr->push_back(t);

        } else {

          delete p;
        }
      }
    }
  } while (fragment < 1.0);

  return vtr;
}

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