//============================================================================
//  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_ExecutionSignatureTagBase_h
#define vtk_m_exec_arg_ExecutionSignatureTagBase_h

#include <vtkm/StaticAssert.h>
#include <vtkm/internal/ExportMacros.h>

#include <type_traits>

namespace vtkm {
namespace exec {
namespace arg {

/// \brief The base class for all tags used in an \c ExecutionSignature.
///
/// If a new \c ExecutionSignature tag is created, it must be derived from this
/// class in some way. This helps identify \c ExecutionSignature tags in the \c
/// VTKM_IS_EXECUTION_SIGNATURE_TAG macro and allows checking the validity of
/// an \c ExecutionSignature.
///
/// In addition to inheriting from this base class, an \c ExecutionSignature
/// tag must define a \c static \c const \c vtkm::IdComponent named \c INDEX
/// that points to a parameter in the \c ControlSignature and a \c typedef
/// named \c AspectTag that defines the aspect of the fetch.
///
struct ExecutionSignatureTagBase {  };

namespace internal {

template<typename ExecutionSignatureTag>
struct ExecutionSignatureTagCheck
{
  static const bool Valid =
      std::is_base_of<
          vtkm::exec::arg::ExecutionSignatureTagBase, ExecutionSignatureTag>::
        value;
};

} // namespace internal

/// Checks that the argument is a proper tag for an \c ExecutionSignature. This
/// is a handy concept check when modifying tags or dispatching to make sure
/// that a template argument is actually an \c ExecutionSignature tag. (You can
/// get weird errors elsewhere in the code when a mistake is made.)
///
#define VTKM_IS_EXECUTION_SIGNATURE_TAG(tag) \
  VTKM_STATIC_ASSERT_MSG( \
    ::vtkm::exec::arg::internal::ExecutionSignatureTagCheck<tag>::Valid, \
    "Provided a type that is not a valid ExecutionSignature tag.")

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

#endif //vtk_m_exec_arg_ExecutionSignatureTagBase_h
