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// Author: Ivana Hrivnacova, IJCLab IN2P3/CNRS, 04/07/2012

#ifndef G4MergeMode_h
#define G4MergeMode_h 1

#include "globals.hh"
#include "G4Exception.hh"

#include <functional>
#include <cmath>

// Enumeration for definition available binning schemes

enum class G4MergeMode {
  kAddition,        // "Or" if boolean type
  kMultiplication,  // "And" if boolean type
  kMaximum,         // "Or" if boolean type
  kMinimum          // "And" if boolean type
};

// Generic merge function
template <typename T>
using G4MergeFunction = std::function<T(const T&, const T&)>;

// Utility functions
namespace  G4Accumulables {

G4MergeMode GetMergeMode(const G4String& mergeModeName);

template <typename T>
G4MergeFunction<T> GetMergeFunction(G4MergeMode mergeMode)
{
  switch ( mergeMode ) {
    case G4MergeMode::kAddition:
      return std::plus<T>();

    case G4MergeMode::kMultiplication:
      return std::multiplies<T>();

    case G4MergeMode::kMaximum:
      return [](const T& x, const T& y) { return std::max(x,y); };

    case G4MergeMode::kMinimum:
      return [](const T& x, const T& y) { return std::min(x,y); };
  }

  // Must never get here, but we need a return to satisfy MSVC
  G4Exception("G4Accumulables::GetMergeFunction<T>",
            "Analysis_F001", FatalException,
            "Undefined merge mode");
  return [](const T&, const T&) { return T(); };
}

template <G4bool>
G4MergeFunction<G4bool> GetMergeFunction(G4MergeMode mergeMode)
{
  switch ( mergeMode ) {
    case G4MergeMode::kAddition:
    case G4MergeMode::kMaximum:
      // return std::bind([](const T& x, const T& y) { return x + y; });
      return [](const G4bool& x, const G4bool& y) { return x || y; };

    case G4MergeMode::kMultiplication:
    case G4MergeMode::kMinimum:
      return [](const G4bool& x, const G4bool& y) { return x && y; };
  }
}

}

#endif
