PrepDataToSimHitAssocAlg.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
#include "PrepDataToSimHitAssocAlg.h"
 
#include "StoreGate/WriteDecorHandle.h"
#include "xAODMuonPrepData/UtilFunctions.h"
#include "xAODMuonPrepData/RpcMeasurement.h"
#include "xAODMuonPrepData/TgcStrip.h"
#include "xAODMuonPrepData/sTgcMeasurement.h"
#include "xAODMuonPrepData/MMCluster.h"
#include "xAODMuonViews/ChamberViewer.h"
#include <span>
namespace MuonR4{
    StatusCode PrepDataToSimHitAssocAlg::initialize() {
        ATH_CHECK(m_simHitsKey.initialize());
        ATH_CHECK(m_prdHitKey.initialize());
        ATH_CHECK(m_decorKey.initialize());
        ATH_CHECK(m_idHelperSvc.retrieve());
        ATH_CHECK(m_geoCtxKey.initialize());
        return StatusCode::SUCCESS;
    }    
    StatusCode PrepDataToSimHitAssocAlg::execute(const EventContext & ctx) const {
        const ActsGeometryContext* gctx{nullptr};
        const xAOD::MuonSimHitContainer* simHits{nullptr};
        const xAOD::UncalibratedMeasurementContainer* measurements{nullptr};
        ATH_CHECK(SG::get(gctx, m_geoCtxKey, ctx));
        ATH_CHECK(SG::get(simHits, m_simHitsKey, ctx));
        ATH_CHECK(SG::get(measurements, m_prdHitKey, ctx));
 
        xAOD::ChamberViewer prdViewer{*measurements};
        xAOD::ChamberViewer simHitViewer{*simHits, m_idHelperSvc.get(), xAOD::ChamberView::Mode::DetElement};
        SG::WriteDecorHandle<xAOD::UncalibratedMeasurementContainer, LinkType> decorHandle{m_decorKey, ctx};
        if (measurements->empty()){
            return StatusCode::SUCCESS;
        }
        do {
            const Identifier chambId = xAOD::identify(prdViewer.at(0));
            const IdentifierHash viewHash = m_idHelperSvc->detElementHash(chambId);
            decorHandle(*prdViewer.at(0)) = LinkType{};
 
            if ((simHitViewer.size() == 0 || m_idHelperSvc->detElementHash(simHitViewer.at(0)->identify()) > viewHash)  && 
                 !simHitViewer.loadView(chambId)) {
                ATH_MSG_DEBUG("No simHit view for " << m_idHelperSvc->toStringDetEl(chambId));
                continue;
            } else if (m_idHelperSvc->detElementHash(simHitViewer.at(0)->identify())  < viewHash \
                      && !simHitViewer.next([viewHash, this](const xAOD::MuonSimHit* hit){
                        return m_idHelperSvc->detElementHash(hit->identify()) == viewHash;
                      })) {
                continue;
            }
            ATH_MSG_VERBOSE("Container size "<<simHits->size()<<" viewer size: "<<simHitViewer.size()<<" view hash: "<<viewHash);
            std::unordered_set<Identifier> prds{};
            for (const xAOD::UncalibratedMeasurement* measurement : prdViewer) {
                const xAOD::MuonSimHit* bestSimHit{nullptr};
                switch (measurement->type()) {
                    case xAOD::UncalibMeasType::MdtDriftCircleType: {
                        const Identifier prdId{xAOD::identify(measurement)};                
                        xAOD::MuonSimHitContainer::const_iterator matching_itr = 
                            std::ranges::find_if(simHitViewer,[&prdId](const xAOD::MuonSimHit* hit){
                                return hit->identify() == prdId;
                            });
                        if (matching_itr != simHitViewer.end()) {
                            bestSimHit =(*matching_itr);
                        }
                        break;
                    } case xAOD::UncalibMeasType::MMClusterType: {
                        prds.clear();
                        const auto* mmHit = static_cast<const xAOD::MMCluster*>(measurement);
                        const MmIdHelper& mmIdHelper{m_idHelperSvc->mmIdHelper()};
                        const int ml = mmIdHelper.multilayer(mmHit->identify());
                        for (const uint16_t strip : mmHit->stripNumbers()) {
                            prds.insert(mmIdHelper.channelID(mmHit->identify(), ml, mmHit->gasGap(), strip));
                        }
                        xAOD::MuonSimHitContainer::const_iterator matching_itr = 
                            std::ranges::find_if(simHitViewer,[&prds](const xAOD::MuonSimHit* hit){
                                return prds.count(hit->identify());
                            });
                        if (matching_itr != simHitViewer.end()) {
                            bestSimHit =(*matching_itr);
                        }
                        break;
                    } case xAOD::UncalibMeasType::RpcStripType:
                      case xAOD::UncalibMeasType::TgcStripType:
                      case xAOD::UncalibMeasType::sTgcStripType: {
                    const Identifier prdId{xAOD::identify(measurement)};
                    const MuonGMR4::MuonReadoutElement* readOutEle = xAOD::muonReadoutElement(measurement);
                    const Amg::Transform3D& locToGlob{readOutEle->localToGlobalTrans(*gctx, readOutEle->layerHash(prdId))};
                    
                    const Identifier gasGapId = m_idHelperSvc->gasGapId(prdId);
                    Amg::Vector3D locPos{Amg::Vector3D::Zero()};
                    if (measurement->numDimensions() == 1) {
                        locPos = measurement->localPosition<1>().x() * Amg::Vector3D::UnitX();
                    } else {
                        locPos.block<2,1>(0,0) = xAOD::toEigen(measurement->localPosition<2>());
                    }
                    double closestDistance{m_PullCutOff};
                    for ( const xAOD::MuonSimHit* simHit : simHitViewer) {
                        if (gasGapId != m_idHelperSvc->gasGapId(simHit->identify())) {
                            continue; 
                        }
                        const IdentifierHash simLayHash{readOutEle->layerHash(simHit->identify())};
                        const Amg::Transform3D globToLoc{readOutEle->globalToLocalTrans(*gctx, simLayHash) *locToGlob};
                        const Amg::Vector3D prdPos = globToLoc * locPos;
                        double dist{0.};
                        if (measurement->numDimensions() == 1) {
                            dist = std::abs(prdPos.x() - simHit->localPosition().x()) 
                                 / std::sqrt(measurement->localCovariance<1>()(0,0));
                        } else{
                            const Amg::Vector2D diff = (prdPos - xAOD::toEigen(simHit->localPosition())).block<2,1>(0,0);
                            dist = std::sqrt(diff.dot(xAOD::toEigen(measurement->localCovariance<2>()).inverse() * diff));
                        }
                        if (dist < closestDistance) {
                            closestDistance = dist;
                            bestSimHit = simHit;
                        }
                    }
                    break;
                } default: {
                    ATH_MSG_FATAL("Non muon measurement is parsed");
                    return StatusCode::FAILURE;
                }
            }
            if (!bestSimHit) {
                continue;
            }
            decorHandle(*measurement) = LinkType{*simHits, bestSimHit->index()};
            }
 
        } while (prdViewer.next());
        
        return StatusCode::SUCCESS;
    }
}