//============================================================================
//  Copyright (c) Kitware, Inc.
//  All rights reserved.
//  See LICENSE.txt for details.
//  This software is distributed WITHOUT ANY WARRANTY; without even
//  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
//  PURPOSE.  See the above copyright notice for more information.
//
//  Copyright 2014 National Technology & Engineering Solutions of Sandia, LLC (NTESS).
//  Copyright 2014 UT-Battelle, LLC.
//  Copyright 2014 Los Alamos National Security.
//
//  Under the terms of Contract DE-NA0003525 with NTESS,
//  the U.S. Government retains certain rights in this software.
//
//  Under the terms of Contract DE-AC52-06NA25396 with Los Alamos National
//  Laboratory (LANL), the U.S. Government retains certain rights in
//  this software.
//============================================================================
#ifndef vtk_m_exec_arg_FetchTagExecObject_h
#define vtk_m_exec_arg_FetchTagExecObject_h

#include <vtkm/exec/arg/AspectTagDefault.h>
#include <vtkm/exec/arg/Fetch.h>

#include <vtkm/exec/ExecutionObjectBase.h>

#include <type_traits>

namespace vtkm
{
namespace exec
{
namespace arg
{

/// \brief \c Fetch tag for execution objects.
///
/// \c FetchTagExecObject is a tag used with the \c Fetch class to retrieve
/// execution objects. For safety, execution objects are read-only. \c
/// FetchTagExecObject is almost always used in conjunction with \c
/// TransportTagExecObject and vice versa.
///
struct FetchTagExecObject
{
};

template <typename ThreadIndicesType, typename ExecObjectType>
struct Fetch<vtkm::exec::arg::FetchTagExecObject,
             vtkm::exec::arg::AspectTagDefault,
             ThreadIndicesType,
             ExecObjectType>
{
  // If you get a compile error here, it means you tried to use an object that
  // is not an execution object as an argument that is expected to be one. All
  // execution objects are expected to inherit from
  // vtkm::exec::ExecutionObjectBase.
  static_assert(
    std::is_base_of<vtkm::exec::ExecutionObjectBase, ExecObjectType>::value,
    "All execution objects are expected to inherit from vtkm::exec::ExecutionObjectBase");

  using ValueType = ExecObjectType;

  VTKM_SUPPRESS_EXEC_WARNINGS
  VTKM_EXEC
  ValueType Load(const ThreadIndicesType& vtkmNotUsed(indices),
                 const ExecObjectType& execObject) const
  {
    return execObject;
  }

  VTKM_EXEC
  void Store(const ThreadIndicesType&, const ExecObjectType&, const ValueType&) const
  {
    // Store is a no-op for this fetch.
  }
};
}
}
} // namespace vtkm::exec::arg

#endif //vtk_m_exec_arg_FetchTagExecObject_h
