NewtonTrkDistanceFinder.h

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/*
  Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef TRKVERTEXSEEDFINDERUTILS_NEWTONTRKDISTANCEFINDER_H
#define TRKVERTEXSEEDFINDERUTILS_NEWTONTRKDISTANCEFINDER_H
 
#include "GaudiKernel/ToolHandle.h"
#include "TrkVertexSeedFinderUtils/SeedFinderParamDefs.h"
#include "AthenaBaseComps/AthAlgTool.h"
#include "MagFieldConditions/AtlasFieldCacheCondObj.h"
#include <variant>
 
namespace Trk
{

 
  static const InterfaceID IID_NewtonTrkDistanceFinder("NewtonTrkDistanceFinder", 1, 1);
  
  class NewtonTrkDistanceFinder final: public AthAlgTool
  {
  public:
 
    static const InterfaceID& interfaceID()
      {
        return IID_NewtonTrkDistanceFinder;
      };
 
    
    //default constructor due to Athena interface
    NewtonTrkDistanceFinder(const std::string& t, const std::string& n, const IInterface*  p);
    
    
    //
    //destructor
    virtual ~NewtonTrkDistanceFinder();
 
    virtual StatusCode initialize() override;
    virtual StatusCode finalize() override;
 
    // GetClosestPoints returns either the resulting TwoPoints,
    // or an error string on failure.
    
    std::variant<TwoPoints, std::string>
    GetClosestPoints(const Perigee & a, const Perigee & b) const {
      //with the constractur of PointOnTrackPar a track is constructed with, as seed, 
    //directly the point of closest approach (see for info PointOnTrack.h)
      return GetClosestPoints(PointOnTrack(a),PointOnTrack(b));
    }
  
    std::variant<TwoPoints, std::string>
    GetClosestPoints(const PointOnTrack &, const PointOnTrack &) const;
 
    std::variant<TwoPoints, std::string>
    GetClosestPoints(const TwoTracks & twotracks) const {
      return GetClosestPoints(twotracks.getFirstPerigee(),twotracks.getSecondPerigee());
    }
  
    std::variant<TwoPoints, std::string>
    GetClosestPoints(const TwoPointOnTrack & twopointontrack) const {
      return GetClosestPoints(twopointontrack.first,twopointontrack.second);
    }
    
  private:
  //parameters for precision
  double m_precision;//as job option
  double m_maxloopnumber;//as job option
 
  //variables for magnetic field service needed to retrieve the correct Bz
  SG::ReadCondHandleKey<AtlasFieldCacheCondObj> m_fieldCacheCondObjInputKey 
        {this, "AtlasFieldCacheCondObj", "fieldCondObj", "Name of the Magnetic Field conditions object key"};
 
  };
 
}
 
#endif