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//
//  ---------------------------------------------------------------
//  GEANT4 template class header
//  Class Description:
//      This class delegates which singletons a task references
//  ---------------------------------------------------------------
//  Author: Jonathan Madsen
//  ---------------------------------------------------------------

#include "G4AutoLock.hh"
#include "G4Threading.hh"

#include <functional>
#include <map>
#include <memory>
#include <set>
#include <thread>
#include <tuple>
#include <type_traits>
#include <vector>

namespace G4Traits
{
  template <typename T>
  struct TaskSingletonKey
  {
    using type         = G4int;
    using compare_type = std::less<type>;
  };
}  // namespace G4Traits

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

/// \class G4TaskSingletonEvaluator
/// \brief This structure must be specialized and use overloads to the
/// constructor
///
template <typename T>
struct G4TaskSingletonEvaluator;

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

template <typename T>
class G4TaskSingletonDelegator;

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

template <typename T>
class G4TaskSingletonData
{
  using key_type     = typename G4Traits::TaskSingletonKey<T>::type;
  using compare_type = typename G4Traits::TaskSingletonKey<T>::compare_type;

  friend struct G4TaskSingletonEvaluator<T>;
  friend class G4TaskSingletonDelegator<T>;
  using this_type = G4TaskSingletonData<T>;

 private:
  static std::unique_ptr<this_type>& GetInstance()
  {
    static auto _instance = std::unique_ptr<this_type>(new this_type);
    return _instance;
  }

 private:
  std::map<key_type, T*, compare_type> m_data;
};

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

template <typename T>
struct G4TaskSingletonEvaluator
{
  using key_type  = typename G4Traits::TaskSingletonKey<T>::type;
  using data_type = G4TaskSingletonData<T>;

  template <typename... Args>
  G4TaskSingletonEvaluator(key_type&, Args&&...)
  {
    throw std::runtime_error("Not specialized!");
  }
};

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

template <typename T>
class G4TaskSingletonDelegator
{
 public:
  using pointer        = T*;
  using evaluator_type = G4TaskSingletonEvaluator<T>;
  using data_type      = G4TaskSingletonData<T>;
  using key_type       = typename G4Traits::TaskSingletonKey<T>;

  template <typename... Args>
  static void Configure(Args&&... args)
  {
    auto& _data = data_type::GetInstance();
    evaluator_type _eval(std::forward<Args>(args)...);
    auto _ptr = _data->m_data.at(_eval.index);
    _eval.modifier(_ptr);
    T::SetInstance(_data->m_data.at(_key));
  }
};

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