//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___ALGORITHM_PSTL_MERGE_H
#define _LIBCPP___ALGORITHM_PSTL_MERGE_H

#include <__config>
#include <__functional/operations.h>
#include <__iterator/cpp17_iterator_concepts.h>
#include <__pstl/configuration.h>
#include <__type_traits/enable_if.h>
#include <__type_traits/is_execution_policy.h>
#include <__type_traits/remove_cvref.h>
#include <__utility/move.h>
#include <optional>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _ExecutionPolicy,
          class _ForwardIterator1,
          class _ForwardIterator2,
          class _ForwardOutIterator,
          class _Comp                                         = std::less<>,
          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator>
__merge(_ExecutionPolicy&&,
        _ForwardIterator1 __first1,
        _ForwardIterator1 __last1,
        _ForwardIterator2 __first2,
        _ForwardIterator2 __last2,
        _ForwardOutIterator __result,
        _Comp __comp = {}) noexcept {
  using _Backend = typename __select_backend<_RawPolicy>::type;
  return std::__pstl_merge<_RawPolicy>(
      _Backend{},
      std::move(__first1),
      std::move(__last1),
      std::move(__first2),
      std::move(__last2),
      std::move(__result),
      std::move(__comp));
}

template <class _ExecutionPolicy,
          class _ForwardIterator1,
          class _ForwardIterator2,
          class _ForwardOutIterator,
          class _Comp                                         = std::less<>,
          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator
merge(_ExecutionPolicy&& __policy,
      _ForwardIterator1 __first1,
      _ForwardIterator1 __last1,
      _ForwardIterator2 __first2,
      _ForwardIterator2 __last2,
      _ForwardOutIterator __result,
      _Comp __comp = {}) {
  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "merge requires ForwardIterators");
  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "merge requires ForwardIterators");
  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(_ForwardOutIterator, decltype(*__first1), "merge requires an OutputIterator");
  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(_ForwardOutIterator, decltype(*__first2), "merge requires an OutputIterator");
  auto __res = std::__merge(
      __policy,
      std::move(__first1),
      std::move(__last1),
      std::move(__first2),
      std::move(__last2),
      std::move(__result),
      std::move(__comp));
  if (!__res)
    std::__throw_bad_alloc();
  return *std::move(__res);
}

_LIBCPP_END_NAMESPACE_STD

#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17

_LIBCPP_POP_MACROS

#endif // _LIBCPP___ALGORITHM_PSTL_MERGE_H