// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// 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
// SPDX-FileCopyrightText: Copyright (c) 2023 NVIDIA CORPORATION & AFFILIATES
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCUDACXX___ITERATOR_MERGEABLE_H
#define _LIBCUDACXX___ITERATOR_MERGEABLE_H

#ifndef __cuda_std__
#include <__config>
#endif // __cuda_std__

#include "../__functional/identity.h"
#include "../__functional/ranges_operations.h"
#include "../__iterator/concepts.h"
#include "../__iterator/projected.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

_LIBCUDACXX_BEGIN_NAMESPACE_STD

#if _LIBCUDACXX_STD_VER > 17

template <class _Input1, class _Input2, class _Output,
          class _Comp = _CUDA_VRANGES::less, class _Proj1 = identity, class _Proj2 = identity>
concept mergeable =
    input_iterator<_Input1> &&
    input_iterator<_Input2> &&
    weakly_incrementable<_Output> &&
    indirectly_copyable<_Input1, _Output> &&
    indirectly_copyable<_Input2, _Output> &&
    indirect_strict_weak_order<_Comp, projected<_Input1, _Proj1>, projected<_Input2, _Proj2>>;

#elif _LIBCUDACXX_STD_VER > 14

template <class _Input1, class _Input2, class _Output,
          class _Comp, class _Proj1, class _Proj2>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __mergeable_,
  requires()(
    requires(input_iterator<_Input1>),
    requires(input_iterator<_Input2>),
    requires(weakly_incrementable<_Output>),
    requires(indirectly_copyable<_Input1, _Output>),
    requires(indirectly_copyable<_Input2, _Output>),
    requires(indirect_strict_weak_order<_Comp, projected<_Input1, _Proj1>, projected<_Input2, _Proj2>>)
  ));

template <class _Input1, class _Input2, class _Output,
          class _Comp = _CUDA_VRANGES::less, class _Proj1 = identity, class _Proj2 = identity>
_LIBCUDACXX_CONCEPT mergeable =
    _LIBCUDACXX_FRAGMENT(__mergeable_, _Input1, _Input2, _Output, _Comp, _Proj1, _Proj2);

#endif // _LIBCUDACXX_STD_VER > 14

_LIBCUDACXX_END_NAMESPACE_STD

#endif // _LIBCUDACXX___ITERATOR_MERGEABLE_H