/*
 *  Copyright 2008-2013 NVIDIA Corporation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#pragma once

#include <thrust/detail/config.h>

#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
#  pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
#  pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
#  pragma system_header
#endif // no system header

THRUST_NAMESPACE_BEGIN

namespace detail
{

struct execution_policy_marker
{};

// execution_policy_base serves as a guard against
// infinite recursion in thrust entry points:
//
// template<typename DerivedPolicy>
// void foo(const thrust::detail::execution_policy_base<DerivedPolicy> &s)
// {
//   using thrust::system::detail::generic::foo;
//
//   foo(thrust::detail::derived_cast(thrust::detail::strip_const(s));
// }
//
// foo is not recursive when
// 1. DerivedPolicy is derived from thrust::execution_policy below
// 2. generic::foo takes thrust::execution_policy as a parameter
template <typename DerivedPolicy>
struct execution_policy_base : execution_policy_marker
{};

template <typename DerivedPolicy>
constexpr THRUST_HOST_DEVICE execution_policy_base<DerivedPolicy>&
strip_const(const execution_policy_base<DerivedPolicy>& x)
{
  return const_cast<execution_policy_base<DerivedPolicy>&>(x);
}

template <typename DerivedPolicy>
constexpr THRUST_HOST_DEVICE DerivedPolicy& derived_cast(execution_policy_base<DerivedPolicy>& x)
{
  return static_cast<DerivedPolicy&>(x);
}

template <typename DerivedPolicy>
constexpr THRUST_HOST_DEVICE const DerivedPolicy& derived_cast(const execution_policy_base<DerivedPolicy>& x)
{
  return static_cast<const DerivedPolicy&>(x);
}

} // namespace detail

template <typename DerivedPolicy>
struct execution_policy : thrust::detail::execution_policy_base<DerivedPolicy>
{};

THRUST_NAMESPACE_END
