BestMatchContainer.h

/**************************************************************************
 * basf2 (Belle II Analysis Software Framework)                           *
 * Author: The Belle II Collaboration                                     *
 *                                                                        *
 * See git log for contributors and copyright holders.                    *
 * This file is licensed under LGPL-3.0, see LICENSE.md.                  *
 **************************************************************************/
#pragma once
 
/* C++ headers. */
#include <functional>
#include <optional>
 
namespace Belle2 {
  template <class TItem, class TEstimator >
  class BestMatchContainer {
  public:
 
    typedef std::function< bool(TEstimator, TEstimator)> EstimatorComparison;
 
    bool add(TItem item, TEstimator est,
             EstimatorComparison estComparison
    = [](TEstimator currentBest, TEstimator newEst) {return newEst < currentBest;}
            )
    {
      if (!hasMatch()) {
        // not best match yet, take this one !
        setBestMatch(item, est);
        return true;
      }
 
      if (estComparison(m_bestEstimator, est)) {
        setBestMatch(item, est);
        return true;
      }
 
      // best match was not updated
      return false;
    }
 
    bool hasMatch() const
    {
      return static_cast<bool>(m_bestMatch);
    }
 
    TItem const& getBestMatch() const
    {
      return *m_bestMatch;
    }
 
  private:
 
    void setBestMatch(TItem item, TEstimator est)
    {
      m_bestMatch = item;
      m_bestEstimator = est;
    }
 
    std::optional<TItem> m_bestMatch;
 
    TEstimator m_bestEstimator = TEstimator();
  };
 
} //Belle2