#include "ReflectorProcess.hh"

MyReflectorProcess::MyReflectorProcess(const G4String& processName) : G4VDiscreteProcess(processName)
{
}

MyReflectorProcess::~MyReflectorProcess()
{
}

G4double MyReflectorProcess::GetMeanFreePath(const G4Track&, G4double,
                                              G4ForceCondition* condition)
{
  *condition = Forced;
  return DBL_MAX;
}

G4VParticleChange* MyReflectorProcess::PostStepDoIt(const G4Track& aTrack,
                                                    const G4Step& aStep)
{
  aParticleChange.Initialize(aTrack);

  const G4Step* pStep = &aStep;
  const G4Step* hStep = G4ParallelWorldProcess::GetHyperStep();
  if(hStep != nullptr)
    pStep = hStep;

  const G4Track* pTrack = &aTrack;
  G4StepPoint*   PreS   = pStep->GetPreStepPoint();
  G4StepPoint*   PostS  = pStep->GetPostStepPoint();

  if (PreS->GetPhysicalVolume()->GetName()!="physBoxIn")
  {
    return G4VDiscreteProcess::PostStepDoIt(aTrack, aStep);
  }

  if (PostS->GetStepStatus()!=fGeomBoundary)
  {
    return G4VDiscreteProcess::PostStepDoIt(aTrack, aStep);
  }
  G4ThreeVector  PrePos       = PreS->GetPosition();
  G4ThreeVector  PostPos      = PostS->GetPosition();
  G4ThreeVector  fOldMomentum = PostS->GetMomentumDirection();
  G4ThreeVector  fNewMomentum = PostS->GetMomentumDirection();

  G4bool valid = false;
  G4Navigator* trackNavigator = G4TransportationManager::GetTransportationManager()->GetNavigatorForTracking();
  G4ThreeVector normal = trackNavigator->GetGlobalExitNormal(PostPos, &valid);
  G4ThreeVector pPerp  = normal*(fNewMomentum.dot(normal));

  fNewMomentum = fNewMomentum - 2*pPerp;
  aParticleChange.ProposeMomentumDirection(fNewMomentum);

  return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
}