CaloRectangle.h

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#ifndef RecoCaloTools_Navigation_CaloRectangle_H
#define RecoCaloTools_Navigation_CaloRectangle_H

#include "Geometry/CaloTopology/interface/CaloSubdetectorTopology.h"
#include "Geometry/CaloTopology/interface/CaloTopology.h"

/*
 * CaloRectangle is a class to create a rectangular range of DetIds around a
 * central DetId. Meant to be used for range-based loops to calculate cluster
 * shape variables.
 */

struct CaloRectangle {
    const int iEtaOrIXMin;
    const int iEtaOrIXMax;
    const int iPhiOrIYMin;
    const int iPhiOrIYMax;

    template<class T>
    auto operator()(T home, CaloTopology const& topology);

};

template<class T>
T offsetBy(T start, CaloSubdetectorTopology const& topo, int dIEtaOrIX, int dIPhiOrIY)
{
    for(int i = 0; i < std::abs(dIEtaOrIX) && start != T(0); i++) {
        start = dIEtaOrIX > 0 ? topo.goEast(start) : topo.goWest(start);
    }

    for(int i = 0; i < std::abs(dIPhiOrIY) && start != T(0); i++) {
        start = dIPhiOrIY > 0 ? topo.goNorth(start) : topo.goSouth(start);
    }
    return start;
}

template<class T>
class CaloRectangleRange {

  public:

    class Iterator {

      public:

        Iterator(T const& home, int iEtaOrIX, int iPhiOrIY, CaloRectangle const rectangle, CaloSubdetectorTopology const& topology)
          : home_(home)
          , rectangle_(rectangle)
          , topology_(topology)
          , iEtaOrIX_(iEtaOrIX)
          , iPhiOrIY_(iPhiOrIY)
        {}

        Iterator& operator++() {
            if(iPhiOrIY_ == rectangle_.iPhiOrIYMax) {
                iPhiOrIY_ = rectangle_.iPhiOrIYMin;
                iEtaOrIX_++;
            } else ++iPhiOrIY_;
            return *this;
        }

        int iEtaOrIX() const { return iEtaOrIX_; }
        int iPhiOrIY() const { return iPhiOrIY_; }

        bool operator==(Iterator const& other) const { return iEtaOrIX_ == other.iEtaOrIX() && iPhiOrIY_ == other.iPhiOrIY(); }
        bool operator!=(Iterator const& other) const { return iEtaOrIX_ != other.iEtaOrIX() || iPhiOrIY_ != other.iPhiOrIY(); }

        T operator*() const { return offsetBy(home_, topology_, iEtaOrIX_, iPhiOrIY_); }

      private:

        const T home_;

        const CaloRectangle rectangle_;
        CaloSubdetectorTopology const& topology_;

        int iEtaOrIX_;
        int iPhiOrIY_;
    };

  public:
    CaloRectangleRange(CaloRectangle rectangle, T home, CaloTopology const& topology)
      : home_(home)
      , rectangle_(rectangle)
      , topology_(*topology.getSubdetectorTopology(home))
    {}

   CaloRectangleRange(int size, T home, CaloTopology const& topology)
      : home_(home)
      , rectangle_{-size, size, -size, size}
      , topology_(*topology.getSubdetectorTopology(home))
    {}

    auto begin() {
        return Iterator(home_, rectangle_.iEtaOrIXMin, rectangle_.iPhiOrIYMin, rectangle_, topology_);
    }
    auto end() {
        return Iterator(home_, rectangle_.iEtaOrIXMax + 1, rectangle_.iPhiOrIYMin, rectangle_, topology_);
    }

  private:
    const T home_;
    const CaloRectangle rectangle_;
    CaloSubdetectorTopology const& topology_;
};

template<class T>
auto CaloRectangle::operator()(T home, CaloTopology const& topology) {
    return CaloRectangleRange<T>(*this, home, topology);
}

#endif