//===----------------------------------------------------------------------===//
//
// 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___CONCEPTS_EQUALITY_COMPARABLE_H
#define _LIBCUDACXX___CONCEPTS_EQUALITY_COMPARABLE_H

#include <cuda/std/detail/__config>

#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

#include <cuda/std/__concepts/boolean_testable.h>
#include <cuda/std/__concepts/common_reference_with.h>
#include <cuda/std/__concepts/concept_macros.h>
#include <cuda/std/__type_traits/common_reference.h>
#include <cuda/std/__type_traits/make_const_lvalue_ref.h>

_LIBCUDACXX_BEGIN_NAMESPACE_STD

#if !defined(_CCCL_NO_CONCEPTS)

// [concept.equalitycomparable]

template <class _Tp, class _Up>
concept __weakly_equality_comparable_with =
  requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
    { __t == __u } -> __boolean_testable;
    { __t != __u } -> __boolean_testable;
    { __u == __t } -> __boolean_testable;
    { __u != __t } -> __boolean_testable;
  };

template <class _Tp>
concept equality_comparable = __weakly_equality_comparable_with<_Tp, _Tp>;

template <class _Tp, class _Up>
concept equality_comparable_with =
  equality_comparable<_Tp> && equality_comparable<_Up>
  && common_reference_with<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>>
  && equality_comparable<common_reference_t<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>>>
  && __weakly_equality_comparable_with<_Tp, _Up>;

#elif !defined(_CCCL_NO_VARIABLE_TEMPLATES) // ^^^ !_CCCL_NO_CONCEPTS ^^^

template <class _Tp>
_CCCL_CONCEPT_FRAGMENT(__with_lvalue_reference_, requires()(typename(__make_const_lvalue_ref<_Tp>)));

template <class _Tp>
_CCCL_CONCEPT _With_lvalue_reference = _CCCL_FRAGMENT(__with_lvalue_reference_, _Tp);

template <class _Tp, class _Up>
_CCCL_CONCEPT_FRAGMENT(
  __weakly_equality_comparable_with_,
  requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u)(
    requires(_With_lvalue_reference<_Tp>),
    requires(_With_lvalue_reference<_Up>),
    requires(__boolean_testable<decltype(__t == __u)>),
    requires(__boolean_testable<decltype(__t != __u)>),
    requires(__boolean_testable<decltype(__u == __t)>),
    requires(__boolean_testable<decltype(__u != __t)>)));

template <class _Tp, class _Up>
_CCCL_CONCEPT __weakly_equality_comparable_with = _CCCL_FRAGMENT(__weakly_equality_comparable_with_, _Tp, _Up);

template <class _Tp>
_CCCL_CONCEPT equality_comparable = __weakly_equality_comparable_with<_Tp, _Tp>;

template <class _Tp, class _Up>
_CCCL_CONCEPT_FRAGMENT(
  __equality_comparable_with_,
  requires()(
    requires(equality_comparable<_Tp>),
    requires(equality_comparable<_Up>),
    requires(common_reference_with<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>>),
    requires(equality_comparable<common_reference_t<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>>>),
    requires(__weakly_equality_comparable_with<_Tp, _Up>)));

template <class _Tp, class _Up>
_CCCL_CONCEPT equality_comparable_with = _CCCL_FRAGMENT(__equality_comparable_with_, _Tp, _Up);

#endif // ^^^ !_CCCL_NO_VARIABLE_TEMPLATES

_LIBCUDACXX_END_NAMESPACE_STD

#endif // _LIBCUDACXX___CONCEPTS_EQUALITY_COMPARABLE_H
