//============================================================================
//  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 Sandia Corporation.
//  Copyright 2014 UT-Battelle, LLC.
//  Copyright 2014 Los Alamos National Security.
//
//  Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
//  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_WorkIndex_h
#define vtk_m_exec_arg_WorkIndex_h

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

namespace vtkm {
namespace exec {
namespace arg {

/// \brief Aspect tag to use for getting the work index.
///
/// The \c AspectTagWorkIndex aspect tag causes the \c Fetch class to ignore
/// whatever data is in the associated execution object and return the index.
///
struct AspectTagWorkIndex {  };

/// \brief The \c ExecutionSignature tag to use to get the work index
///
/// When a worklet is dispatched, it broken into pieces defined by the input
/// domain and scheduled on independent threads. This tag in the \c
/// ExecutionSignature passes the index for this work. \c WorkletBase contains
/// a typedef that points to this class.
///
struct WorkIndex : vtkm::exec::arg::ExecutionSignatureTagBase
{
  // The index does not really matter because the fetch is going to ignore it.
  // However, it still has to point to a valid parameter in the
  // ControlSignature because the templating is going to grab a fetch tag
  // whether we use it or not. 1 should be guaranteed to be valid since you
  // need at least one argument for the input domain.
  static const vtkm::IdComponent INDEX = 1;
  typedef vtkm::exec::arg::AspectTagWorkIndex AspectTag;
};

template<typename FetchTag, typename ThreadIndicesType, typename ExecObjectType>
struct Fetch<FetchTag,
             vtkm::exec::arg::AspectTagWorkIndex,
             ThreadIndicesType,
             ExecObjectType>
{
  typedef vtkm::Id ValueType;

  VTKM_EXEC
  vtkm::Id Load(const ThreadIndicesType &indices, const ExecObjectType &) const
  {
    return indices.GetGlobalIndex(); 
  }

  VTKM_EXEC
  void Store(const ThreadIndicesType &,
             const ExecObjectType &,
             const ValueType &) const
  {
    // Store is a no-op.
  }
};

}
}
} // namespace vtkm::exec::arg

#endif //vtk_m_exec_arg_WorkIndex_h
