///////////////////////////////////////////////////////////////////////////////
//
// Simulates optical Rayleigh scattering, as SNOMAN did. This class
// simulates Rayleigh scattering. It should be used in preference to
// the Geant4 G4SNOMANOpRayleigh class as it will calculate mean free
// paths for all materials not just water. It should only be used when
// simulating RAT in a mode to match SNOMAN.
//
// Author: P G Jones <p.g.jones@qmul.ac.uk>
//
// REVISION HISTORY:
//     2014-01-08 : P G Jones - New file.
//
///////////////////////////////////////////////////////////////////////////////
#ifndef __RAT_SNOMANOpRayleigh_hh__
#define __RAT_SNOMANOpRayleigh_hh__

#include <G4VDiscreteProcess.hh>
#include <G4OpticalPhoton.hh>

class G4PhysicsTable;
class G4MaterialPropertiesTable;

namespace RAT
{

class SNOMANOpRayleigh : public G4VDiscreteProcess
{
public:
  // Construct the class
  //
  // processName: optional, defaults to SNOMANOpRayleigh
  // type: optional, defaults to fOptical
  SNOMANOpRayleigh( const G4String& processName = "SNOMANOpRayleigh",
                    G4ProcessType type = fOptical );

  // Deletes the physics table
  ~SNOMANOpRayleigh();

  // Returns true if this code is applicable to the particle type
  G4bool IsApplicable( const G4ParticleDefinition& particleType ) { return ( &particleType == G4OpticalPhoton::OpticalPhoton() ); }

  // Returns the mean free path for the track in mm
  //
  // previousStepSize and condition are unused
  G4double GetMeanFreePath( const G4Track& track,
                            G4double previousStepSize,
                            G4ForceCondition* condition );

  // Invoke scattering to the track
  //
  // returns a particle change description
  G4VParticleChange* PostStepDoIt( const G4Track& track,
                                   const G4Step& step );
private:
  // Builds the physics table, i.e. a table of mean free paths
  void BuildThePhysicsTable();

  // Calculates the mean free paths for a material as a function of photon energy
  //
  // returns the mean free path vector
  G4PhysicsOrderedFreeVector* CalculateRayleighMeanFreePaths( G4Material* const material ) const;

  G4PhysicsTable* fPhysicsTable; // The physics table used
};

} //::RAT

#endif