ExpectedHitUtils.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
#include "ActsGeometry/ActsDetectorElement.h"
#include "InDetIdentifier/PixelID.h"
#include "InDetIdentifier/SCT_ID.h"
#include "InDetReadoutGeometry/SiDetectorElement.h"
 
#include "ActsEvent/ExpectedHitUtils.h"
 
namespace ActsTrk::detail {
 
  std::array<unsigned int,4> expectedLayerPattern(const EventContext& ctx,
                                                  const IExtrapolationTool &extrapolator,
                                                  const Acts::BoundTrackParameters& perigee_parameters,
                                                  double pathLimit) {
    std::array<unsigned int,4> expected_layer_pattern {0u,0u,0u,0u};
    auto result = extrapolator.propagationSteps(ctx,
                                                perigee_parameters,
                                                Acts::Direction::Forward(),
                                                pathLimit);
    if (!result.ok()) {
        return expected_layer_pattern;
    }
    for (const Acts::detail::Step &step : result->first ) {
        // @TODO boundary check ?, does layer number match layer numbering in athena ?
        // @TODO filter out dead modules
        if (!step.geoID.sensitive()) {
            continue;
        }
        const auto* actsDetEl = getActsDetectorElement(step.surface);
        if (actsDetEl) {
          addToExpectedLayerPattern(expected_layer_pattern, *actsDetEl);
        }
        
    }
    
 
    return expected_layer_pattern;
  }
 
  void addToExpectedLayerPattern(std::array<unsigned int,4>& pattern, const ActsDetectorElement& detElement) {
    const InDetDD::SiDetectorElement *
      detEl = dynamic_cast<const InDetDD::SiDetectorElement *>(detElement.upstreamDetectorElement());
    if (detEl) {
      if (detEl->isPixel()) {
        InDetDD::DetectorType type = detEl->design().type();
        unsigned int pattern_idx = type==InDetDD::PixelBarrel ? 0 : 1;
        const PixelID* pixel_id = static_cast<const PixelID *>(detEl->getIdHelper());
        pattern[pattern_idx] |= (1<< pixel_id->layer_disk(detEl->identify()) );
      }
      else if (detEl->isSCT()) {
        // @TODO SCT/strip layer number should be shifted by total number of pixel layers ...
        const SCT_ID* sct_id = static_cast<const SCT_ID *>(detEl->getIdHelper());
        unsigned int pattern_idx = detEl->isBarrel() ? 2 : 3;
        pattern[pattern_idx] |= (1<< sct_id->layer_disk(detEl->identify()) );
      }
    }
  }
}