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//
// G4BOptrForceCollision
//
// Class Description:
//
// A G4VBiasingOperator that implements a "force collision" a la
// MCNP. This is meant for neutral particles.
// When the track enters the volume, it is cloned. One copy makes
// a forced free flight up to the volume exit. The other copy makes
// a forced collision inside the volume.
//
// Author: Marc Verderi, November 2013.
// --------------------------------------------------------------------
#ifndef G4BOptrForceCollision_hh
#define G4BOptrForceCollision_hh 1

#include "G4VBiasingOperator.hh"
#include "G4ThreeVector.hh"

#include <vector>
#include <map>

class G4BOptnForceFreeFlight;
class G4BOptnForceCommonTruncatedExp;
class G4BOptnCloning;
class G4VProcess;
class G4BiasingProcessInterface;
class G4ParticleDefinition;
class G4BOptrForceCollisionTrackData;

class G4BOptrForceCollision : public G4VBiasingOperator
{
  public:

    G4BOptrForceCollision(const G4String& particleToForce,
                          const G4String& name="ForceCollision");
    G4BOptrForceCollision(const G4ParticleDefinition* particleToForce,
                          const G4String& name="ForceCollision");
    ~G4BOptrForceCollision();
  
    virtual void Configure() final;
    virtual void ConfigureForWorker() final;
    virtual void StartRun() final;
    virtual void StartTracking( const G4Track* track ) final;
    virtual void ExitBiasing( const G4Track*, const G4BiasingProcessInterface* ) final {};
    virtual void EndTracking() final;

    // -- operation applied:
    void OperationApplied( const G4BiasingProcessInterface* callingProcess,
                                 G4BiasingAppliedCase biasingCase,
                                 G4VBiasingOperation* operationApplied,
                           const G4VParticleChange* particleChangeProduced ) final;
    void OperationApplied( const G4BiasingProcessInterface* callingProcess,
                                 G4BiasingAppliedCase biasingCase,
                                 G4VBiasingOperation* occurenceOperationApplied,
                                 G4double weightForOccurenceInteraction,
                                 G4VBiasingOperation* finalStateOperationApplied,
                           const G4VParticleChange* particleChangeProduced ) final;

  private:

    // -- Mandatory from base class :
    virtual G4VBiasingOperation*
    ProposeNonPhysicsBiasingOperation(const G4Track* track,
                         const G4BiasingProcessInterface* callingProcess) final;
    virtual G4VBiasingOperation*
    ProposeOccurenceBiasingOperation(const G4Track* track,
                         const G4BiasingProcessInterface* callingProcess) final;
    virtual G4VBiasingOperation*
    ProposeFinalStateBiasingOperation(const G4Track* track,
                         const G4BiasingProcessInterface* callingProcess) final;

  private:

    G4int fForceCollisionModelID = 0;
    const G4Track* fCurrentTrack = nullptr;
    G4BOptrForceCollisionTrackData* fCurrentTrackData = nullptr;
    std::map< const G4BiasingProcessInterface*, G4BOptnForceFreeFlight* > fFreeFlightOperations;
    G4BOptnForceCommonTruncatedExp* fSharedForceInteractionOperation = nullptr;
    G4BOptnCloning* fCloningOperation = nullptr;
    G4double fInitialTrackWeight = -1.0;
    G4bool fSetup = true;
    const G4ParticleDefinition* fParticleToBias = nullptr;
};

#endif