ROOTGeometryNavigator.h

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#ifndef LARCOREALG_GEOMETRY_ROOTGEOMETRYNAVIGATOR_H
#define LARCOREALG_GEOMETRY_ROOTGEOMETRYNAVIGATOR_H

// LArSoft libraries
#include "larcorealg/CoreUtils/counter.h" // geo::...::makeFromCoords()
#include "larcorealg/Geometry/GeoNodePath.h"

// ROOT libraries
#include "TGeoManager.h"
#include "TGeoNode.h"
#include "TGeoVolume.h"

// C++ standard library
#include <cassert>
#include <utility> // std::forward()

namespace geo {

  class ROOTGeometryNavigator;

} // namespace geo

//------------------------------------------------------------------------------
class geo::ROOTGeometryNavigator {

  TGeoNode const* fTopNode = nullptr;

public:
  ROOTGeometryNavigator(TGeoManager const& manager) : fTopNode(manager.GetTopNode()) {}

  template <typename Op>
  bool apply(GeoNodePath& path, Op&& op) const;

  template <typename Op>
  bool apply(TGeoNode const* node, Op&& op) const;

  template <typename Op>
  bool apply(Op&& op) const;

}; // geo::ROOTGeometryNavigator

//------------------------------------------------------------------------------
//--- template implementation
//------------------------------------------------------------------------------
template <typename Op>
bool geo::ROOTGeometryNavigator::apply(GeoNodePath& path, Op&& op) const
{
  if (!op(path)) return false;

  TGeoNode const* node = path.current();
  TGeoVolume const* pVolume = node->GetVolume();
  if (pVolume) { // is it even possible not to?
    int const nDaughters = pVolume->GetNdaughters();
    for (int iDaughter : util::counter<int>(nDaughters)) {
      TGeoNode const* pDaughter = pVolume->GetNode(iDaughter);
      if (!pDaughter) continue; // fishy...

      path.append(pDaughter);
      if (!apply(path, std::forward<Op>(op))) return false;
      path.pop();
    } // for
  }   // if we have a volume

  return true;
}

//------------------------------------------------------------------------------
template <typename Op>
bool geo::ROOTGeometryNavigator::apply(TGeoNode const* node, Op&& op) const
{
  GeoNodePath path{node};
  return apply(path, std::forward<Op>(op));
}

//------------------------------------------------------------------------------
template <typename Op>
bool geo::ROOTGeometryNavigator::apply(Op&& op) const
{
  assert(fTopNode);
  return apply(fTopNode, std::forward<Op>(op));
}

//------------------------------------------------------------------------------

#endif // LARCOREALG_GEOMETRY_ROOTGEOMETRYNAVIGATOR_H