MsTrackSeeder.h

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
#ifndef MUONTRACKFINDINGTOOLS_MSTRACKSEEDER_H
#define MUONTRACKFINDINGTOOLS_MSTRACKSEEDER_H
 
#include "AthenaBaseComps/AthMessaging.h"
 
#include "GaudiKernel/SystemOfUnits.h"
#include "Acts/Utilities/KDTree.hpp"
 
 
#include "xAODMuon/MuonSegmentContainer.h"
#include "MuonTrackEvent/MsTrackSeed.h"
#include "MuonReadoutGeometryR4/MuonDetectorManager.h"
#include "MuonRecToolInterfacesR4/ISegmentSelectionTool.h"
#include "ActsGeometry/ATLASMagneticFieldWrapper.h"
 
 
namespace MuonR4{
    class MsTrackSeeder: public AthMessaging {
        public:
            struct Config{
                double barrelRadius{7.*Gaudi::Units::m};
                double barrelLength{25.*Gaudi::Units::m};
                double endcapDiscZ{15.*Gaudi::Units::m};
                double endcapDiscRadius{13.*Gaudi::Units::m};
                double seedHalfLength{25.*Gaudi::Units::cm};
                const MuonGMR4::MuonDetectorManager* detMgr{};
                const ISegmentSelectionTool* selector{nullptr};
                std::set<double> fieldExtpSteps{0.,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1};
            };

            using SearchTree_t = Acts::KDTree<3, const xAOD::MuonSegment*, double, std::array, 6>;
            using Location = MsTrackSeed::Location;
            using SectorProjector = ExpandedSector::SectorProjector;
            using VecOpt_t = std::optional<Amg::Vector3D>;
            enum class SeedCoords : std::uint8_t{
                eDetSection,
                eSector,
                ePosOnCylinder
            };

            MsTrackSeeder(const std::string& msgName, Config&& cfg);   
            SearchTree_t constructTree(const ActsTrk::GeometryContext& gctx,
                                       const xAOD::MuonSegmentContainer& segments) const;
            Amg::Vector2D expressOnCylinder(const ActsTrk::GeometryContext& gctx, 
                                            const xAOD::MuonSegment& segment,
                                            const Location loc,
                                            const ExpandedSector sector) const;
            Amg::Vector3D projectOntoPhiPlane(const ActsTrk::GeometryContext& gctx, 
                                              const xAOD::MuonSegment& segment,
                                              const double projectPhi) const;
            double estimateTwoStationP(const xAOD::MuonSegment& segment1,
                                   const xAOD::MuonSegment& segment2,
                                   const AtlasFieldCacheCondObj& magField) const;
            double estimateQtimesP(const ActsTrk::GeometryContext& gctx,
                                   const AtlasFieldCacheCondObj& magField,
                                   const MsTrackSeed& seed) const;
            bool withinBounds(const Amg::Vector2D& projPos,
                              const Location loc) const;
            std::unique_ptr<MsTrackSeedContainer> findTrackSeeds(const EventContext& ctx,
                                                                 const ActsTrk::GeometryContext& gctx,
                                                                 const xAOD::MuonSegmentContainer& segments) const;
            const MuonGMR4::SpectrometerSector* envelope(const xAOD::MuonSegment& segment) const;
        private:
            using PosMomPair_t = std::pair<Amg::Vector3D, Amg::Vector3D>;
            std::pair<double, unsigned> averageBField(const PosMomPair_t& start,
                                                      const PosMomPair_t& end,
                                                      const AtlasFieldCacheCondObj& magField,
                                                      const bool skipFirst) const;

            std::optional<double> calculateRadius(VecOpt_t&& pI, VecOpt_t&& pM, VecOpt_t&& pO,
                                                  const Amg::Vector3D& planeNorm) const;

            using TreeRawVec_t = SearchTree_t::vector_t;
            void appendSegment(const ActsTrk::GeometryContext& gctx,
                               const xAOD::MuonSegment* segment,
                               const Location loc,
                               TreeRawVec_t& outContainer) const;
            std::unique_ptr<MsTrackSeedContainer> resolveOverlaps(MsTrackSeedContainer&& unresolved) const;
 
            Config m_cfg{};
    };
}
 
 
#endif