Matcher.h

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#ifndef UtilAlgos_Matcher_h
#define UtilAlgos_Matcher_h
/* \class Matcher
 *
 * \author Luca Lista, INFN
 *
 */
#include "FWCore/Framework/interface/EDProducer.h"
#include "FWCore/ParameterSet/interface/ParameterSet.h"
#include "FWCore/Utilities/interface/InputTag.h"
#include "CommonTools/UtilAlgos/interface/DeltaR.h"
#include "FWCore/Framework/interface/Event.h"
#include "DataFormats/Common/interface/Handle.h"
#include "DataFormats/Common/interface/AssociationMap.h"
#include "DataFormats/Common/interface/OneToOne.h"
#include "DataFormats/Common/interface/getRef.h"

namespace reco {
  namespace modules {
    template<typename C1, typename C2, typename M = edm::AssociationMap<edm::OneToOne<C1, C2> > >
    class MatcherBase : public edm::EDProducer {
    public:
      MatcherBase( const edm::ParameterSet & );
      ~MatcherBase();

    protected:
      typedef typename C1::value_type T1;
      typedef typename C2::value_type T2;
      typedef M MatchMap;

    private:
      void produce( edm::Event&, const edm::EventSetup&) override;
      edm::InputTag src_;
      edm::InputTag matched_;
      double distMin_;
      virtual double matchDistance( const T1 &, const T2 & ) const = 0;
      virtual bool select( const T1 &, const T2 & ) const = 0;
    };

    template<typename C1, typename C2,
             typename S, typename D = DeltaR<typename C1::value_type, typename C2::value_type>,
             typename M =  edm::AssociationMap<edm::OneToOne<C1, C2> > >
    class Matcher : public MatcherBase<C1, C2, M> {
    public:
      Matcher(  const edm::ParameterSet & cfg ) : 
    MatcherBase<C1, C2, M>( cfg ),
        select_( reco::modules::make<S>( cfg ) ), 
    distance_( reco::modules::make<D>( cfg ) ) { }
      ~Matcher() { }
    private:
      typedef typename MatcherBase<C1, C2, M>::T1 T1;
      typedef typename MatcherBase<C1, C2, M>::T2 T2;
      typedef typename MatcherBase<C1, C2, M>::MatchMap MatchMap;

      double matchDistance( const T1 & c1, const T2 & c2 ) const {
    return distance_( c1, c2 );
      }
      bool select( const T1 & c1, const T2 & c2 ) const { 
    return select_( c1, c2 ); 
      }
      S select_;
      D distance_;
    };

    namespace helper {
      typedef std::pair<size_t, double> MatchPair;

      struct SortBySecond {
    bool operator()( const MatchPair & p1, const MatchPair & p2 ) const {
      return p1.second < p2.second;
    } 
      };
    }

    template<typename C1, typename C2, typename M>
    MatcherBase<C1, C2, M>::MatcherBase( const edm::ParameterSet & cfg ) :
      src_( cfg.template getParameter<edm::InputTag>( "src" ) ),
      matched_( cfg.template getParameter<edm::InputTag>( "matched" ) ), 
      distMin_( cfg.template getParameter<double>( "distMin" ) ) {
      produces<MatchMap>();
    }

    template<typename C1, typename C2, typename M>
    MatcherBase<C1, C2, M>::~MatcherBase() { }

    template<typename C1, typename C2, typename M>    
    void MatcherBase<C1, C2, M>::produce( edm::Event& evt, const edm::EventSetup& ) {
      using namespace edm;
      using namespace std;
      Handle<C2> matched;  
      evt.getByLabel( matched_, matched );
      Handle<C1> cands;  
      evt.getByLabel( src_, cands );
      typedef typename MatchMap::ref_type ref_type;
      typedef typename ref_type::key_type key_ref_type;
      typedef typename ref_type::value_type value_ref_type;
      auto_ptr<MatchMap> matchMap( new MatchMap( ref_type( key_ref_type( cands ), 
                               value_ref_type( matched ) ) ) );
      for( size_t c = 0; c != cands->size(); ++ c ) {
    const T1 & cand = (*cands)[ c ];
    vector<helper::MatchPair> v;
    for( size_t m = 0; m != matched->size(); ++ m ) {
      const T2 & match = ( * matched )[ m ];
      if ( select( cand, match ) ) {
        double dist = matchDistance( cand, match );
        if ( dist < distMin_ ) v.push_back( make_pair( m, dist ) );
      }
    }
    if ( v.size() > 0 ) {
      size_t mMin = min_element( v.begin(), v.end(), helper::SortBySecond() )->first;
      typedef typename MatchMap::key_type key_type;
      typedef typename MatchMap::data_type data_type;
      matchMap->insert( edm::getRef( cands, c ), edm::getRef( matched, mMin ) );
    }
      }
      evt.put( matchMap );
    }    
    
  }
}

#endif