MuonSimHitHelpers.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#include <MuonTruthHelpers/MuonSimHitHelpers.h>
#include <xAODMuon/MuonSegmentContainer.h>
#include <xAODMuonSimHit/MuonSimHitContainer.h>
#include <xAODTruth/TruthParticleContainer.h>
#include <xAODMeasurementBase/UncalibratedMeasurementContainer.h>
#include <MuonSpacePoint/SpacePoint.h>
#include <MuonSpacePoint/CalibratedSpacePoint.h>
#include <MuonPatternEvent/Segment.h>
#include <AthLinks/ElementLink.h>
#include <xAODMuonPrepData/sTgcMeasurement.h>
#include <xAODMuonPrepData/CombinedMuonStrip.h>
 
namespace {
    using SegLink_t = ElementLink<xAOD::MuonSegmentContainer>;
    using SimHitLink_t = ElementLink<xAOD::MuonSimHitContainer>;
    using PrdLink_t = ElementLink<xAOD::UncalibratedMeasurementContainer>;
 
    using PrdLinkVec_t = std::vector<PrdLink_t>;
    using SimHitLinkVec_t = std::vector<SimHitLink_t>;
    using SegLinkVec_t = std::vector<SegLink_t>;
 
}
 
namespace MuonR4 {
    const xAOD::MuonSimHit* getTruthMatchedHit(const xAOD::MuonMeasurement& prdHit) {
        static const SG::ConstAccessor<SimHitLink_t> acc("simHitLink");
        if (acc.isAvailable(prdHit)){
            const SimHitLink_t& link{acc(prdHit)};
            if (link.isValid()) {
                return (*link);
            }
        }
        return nullptr;
    }
 
    std::unordered_set<const xAOD::MuonSimHit*> getMatchingSimHits(const xAOD::MuonSegment& segment) {
 
        static const SG::ConstAccessor<SimHitLinkVec_t> acc_simLink{"simHitLinks"};
        static const SG::ConstAccessor<PrdLinkVec_t> acc_prdLink{"prdLinks"};
        std::unordered_set<const xAOD::MuonSimHit*> hits{};
        if (acc_simLink.isAvailable(segment)){
            hits.reserve(acc_simLink(segment).size());
            for (const SimHitLink_t& link : acc_simLink(segment)) {
                if (link.isValid()) {
                    hits.insert(*link);
                }
            }
        } else if (acc_prdLink.isAvailable(segment)){
            for (const PrdLink_t& link : acc_prdLink(segment)) {
                if(!link.isValid()){
                    continue;
                }
                const auto* prdHit = dynamic_cast<const xAOD::MuonMeasurement*>(*link);
                if (!prdHit) {
                    continue;
                }
 
                std::vector<const xAOD::MuonMeasurement*> prds{prdHit};
 
                // The segment links the eta & phi prds of a gas gap through a combined strip
                // This is necessary e.g for sTGC as the simHitLink decoration takes places on the original prd container, whereas CombinedMuonStrip is built later in the segment conversion
                if (const auto* cmb = dynamic_cast<const xAOD::CombinedMuonStrip*>(prdHit)) {
                    prds = {cmb->primaryStrip(), cmb->secondaryStrip()};
                }
 
                for (const xAOD::MuonMeasurement* prd : prds) {
                    const xAOD::MuonSimHit* hit = prd ? getTruthMatchedHit(*prd) : nullptr;
                    if (hit) {
                        hits.insert(hit);
                    }
                }
            }
        }
        return hits;
    }
 
    std::unordered_set<const xAOD::MuonSimHit*> getMatchingSimHits(const std::vector<const SpacePoint*>& spacePoints) {
        std::unordered_set<const xAOD::MuonSimHit*> hits{};
        for (const SpacePoint* sp : spacePoints) {
            const xAOD::MuonSimHit* primHit{getTruthMatchedHit(*sp->primaryMeasurement())};
            const xAOD::MuonSimHit* secHit{sp->dimension() == 2 ? getTruthMatchedHit(*sp->secondaryMeasurement()) : nullptr};
            if(primHit){
                hits.insert(primHit);
            }
            if (secHit && secHit != primHit) {
                hits.insert(secHit);
            }
        }
        return hits;
    }
 
    std::unordered_set<const xAOD::MuonSimHit*> getMatchingSimHits(const std::vector<const CalibratedSpacePoint*>& measurements) {
        std::unordered_set<const xAOD::MuonSimHit*> hits{};
        for (const CalibratedSpacePoint* meas : measurements) {
            const SpacePoint* sp = meas->spacePoint();
            if (!sp) continue;
            const xAOD::MuonSimHit* primHit{getTruthMatchedHit(*sp->primaryMeasurement())};
            const xAOD::MuonSimHit* secHit{sp->dimension() == 2 ? getTruthMatchedHit(*sp->secondaryMeasurement()) : nullptr};
            if(primHit){
                hits.insert(primHit);
            }
            if (secHit && secHit != primHit) {
                hits.insert(secHit);
            }
        }
        return hits;
    }
    std::unordered_set<const xAOD::MuonSimHit*> getMatchingSimHits(const Segment& segment) {
        std::vector<const CalibratedSpacePoint*> calibSps{};
        calibSps.reserve(segment.measurements().size());
        std::ranges::transform(segment.measurements(), std::back_inserter(calibSps), [](const auto& meas){return meas.get();});
        return getMatchingSimHits(calibSps);
    }
    std::unordered_set<const xAOD::MuonSimHit*> getMatchingSimHits(const SpacePointBucket& bucket) {
        std::vector<const SpacePoint*> spacePoints{};
        spacePoints.reserve(bucket.size());
        std::ranges::transform(bucket, std::back_inserter(spacePoints), [](const SpacePointBucket::value_type& sp){return sp.get();});
        return getMatchingSimHits(spacePoints);
    }
    std::unordered_set<const xAOD::MuonSimHit*> getMatchingSimHits(const SegmentSeed& seed) {
        return getMatchingSimHits(seed.getHitsInMax());
    }
    const xAOD::TruthParticle* getTruthMatchedParticle(const xAOD::MuonSegment& segment){
        using TruthLink_t = ElementLink<xAOD::TruthParticleContainer>;
        static const SG::ConstAccessor<TruthLink_t> acc{"truthParticleLink"};
        if (acc.isAvailable(segment)){
            const TruthLink_t& link {acc(segment)};
            if (link.isValid()) {
                return *link;
            }
        }
        return nullptr;
    }
    const xAOD::MuonSegment* getMatchedTruthSegment(const xAOD::MuonSegment& segment) {
        static const SG::ConstAccessor<SegLink_t> acc{"truthSegmentLink"};
        if (acc.isAvailable(segment)) {
            const SegLink_t& link{acc(segment)};
            if (link.isValid()){
                return *link;
            }
        }
        return nullptr;
    }
 
    const xAOD::MuonSegment* getMatchedTruthSegment(const xAOD::MuonSimHit& hit) {
        static const SG::ConstAccessor<SegLink_t> acc{"truthSegmentLink"};
        if (acc.isAvailable(hit)) {
            const SegLink_t& link{acc(hit)};
            if (link.isValid()){
                return *link;
            }
        }
        return nullptr;
    }
    const xAOD::TruthParticle* getTruthMatchedParticle(const xAOD::MuonSimHit& hit) {
        const xAOD::MuonSegment* truthSeg = getMatchedTruthSegment(hit);
        return truthSeg ? getTruthMatchedParticle(*truthSeg) : nullptr;
    }
 
    std::vector<const xAOD::MuonSegment*> getTruthSegments(const xAOD::TruthParticle& truthMuon) {
        static const SG::ConstAccessor<SegLinkVec_t> acc{"truthSegmentLinks"};
        std::vector<const xAOD::MuonSegment*> segments{};
 
        if (!acc.isAvailable(truthMuon)) {
            return segments;
        }
        for (const SegLink_t& link : acc(truthMuon)) {
            segments.emplace_back(*link);
        }
        return segments;
    }
}