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//===----------------------------------------------------------------------===//
//
// 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___UTILITY_PAIR_H
#define _LIBCPP___UTILITY_PAIR_H

#include <__compare/common_comparison_category.h>
#include <__compare/synth_three_way.h>
#include <__concepts/different_from.h>
#include <__config>
#include <__fwd/array.h>
#include <__fwd/pair.h>
#include <__fwd/tuple.h>
#include <__tuple/sfinae_helpers.h>
#include <__tuple/tuple_element.h>
#include <__tuple/tuple_indices.h>
#include <__tuple/tuple_size.h>
#include <__type_traits/common_reference.h>
#include <__type_traits/common_type.h>
#include <__type_traits/conditional.h>
#include <__type_traits/decay.h>
#include <__type_traits/integral_constant.h>
#include <__type_traits/is_assignable.h>
#include <__type_traits/is_constructible.h>
#include <__type_traits/is_convertible.h>
#include <__type_traits/is_implicitly_default_constructible.h>
#include <__type_traits/is_nothrow_assignable.h>
#include <__type_traits/is_nothrow_constructible.h>
#include <__type_traits/is_reference.h>
#include <__type_traits/is_same.h>
#include <__type_traits/is_swappable.h>
#include <__type_traits/is_trivially_relocatable.h>
#include <__type_traits/nat.h>
#include <__type_traits/remove_cvref.h>
#include <__type_traits/unwrap_ref.h>
#include <__utility/declval.h>
#include <__utility/forward.h>
#include <__utility/move.h>
#include <__utility/piecewise_construct.h>
#include <cstddef>

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _T1, class _T2>
struct _LIBCPP_TEMPLATE_VIS pair {
  using first_type  = _T1;
  using second_type = _T2;

_T1 first;
  _T2 second;

_LIBCPP_HIDE_FROM_ABI pair(pair const&) = default;
  _LIBCPP_HIDE_FROM_ABI pair(pair&&)      = default;

// When we are requested for pair to be trivially copyable by the ABI macro, we use defaulted members
  // if it is both legal to do it (i.e. no references) and we have a way to actually implement it, which requires
  // the __enable_if__ attribute before C++20.

#ifdef _LIBCPP_ABI_TRIVIALLY_COPYABLE_PAIR
// FIXME: This should really just be a static constexpr variable. It's in a struct to avoid gdb printing the value
  // when printing a pair
  struct __has_defaulted_members {
    static const bool value = !is_reference<first_type>::value && !is_reference<second_type>::value;
  };

_LIBCPP_HIDE_FROM_ABI constexpr pair& operator=(const pair&)
    requires (__has_defaulted_members::value && is_copy_assignable<first_type>::value && is_copy_assignable<second_type>::value)
  = default;

_LIBCPP_HIDE_FROM_ABI constexpr pair& operator=(const pair&)
    requires (__has_defaulted_members::value && !(is_copy_assignable<first_type>::value && is_copy_assignable<second_type>::value))
  = delete;

_LIBCPP_HIDE_FROM_ABI constexpr pair& operator=(pair&&)
    requires (__has_defaulted_members::value && is_move_assignable<first_type>::value && is_move_assignable<second_type>::value)
  = default;

//   _LIBCPP_HIDE_FROM_ABI constexpr pair& operator=(pair&&)
//     requires (__has_defaulted_members::value && !(is_move_assignable<first_type>::value && is_move_assignable<second_type>::value))
//   = delete;
#else
  struct __has_defaulted_members {
    static const bool value = false;
  };
#endif

struct _CheckArgs {
    template <int&...>
    static _LIBCPP_HIDE_FROM_ABI constexpr bool __enable_implicit_default() {
      return __is_implicitly_default_constructible<_T1>::value && __is_implicitly_default_constructible<_T2>::value;
    }

template <int&...>
    static _LIBCPP_HIDE_FROM_ABI constexpr bool __enable_default() {
      return is_default_constructible<_T1>::value && is_default_constructible<_T2>::value;
    }

template <class _U1, class _U2>
    static _LIBCPP_HIDE_FROM_ABI constexpr bool __is_pair_constructible() {
      return is_constructible<first_type, _U1>::value && is_constructible<second_type, _U2>::value;
    }

template <class _U1, class _U2>
    static _LIBCPP_HIDE_FROM_ABI constexpr bool __is_implicit() {
      return is_convertible<_U1, first_type>::value && is_convertible<_U2, second_type>::value;
    }
  };

template <bool _MaybeEnable>
  using _CheckArgsDep _LIBCPP_NODEBUG =
      typename conditional< _MaybeEnable, _CheckArgs, __check_tuple_constructor_fail>::type;

template <bool _Dummy = true, __enable_if_t<_CheckArgsDep<_Dummy>::__enable_default(), int> = 0>
  explicit(!_CheckArgsDep<_Dummy>::__enable_implicit_default()) _LIBCPP_HIDE_FROM_ABI constexpr pair() noexcept(
      is_nothrow_default_constructible<first_type>::value && is_nothrow_default_constructible<second_type>::value)
      : first(), second() {}

template <
#  if _LIBCPP_STD_VER >= 23 // http://wg21.link/P1951
      class _U1 = _T1,
      class _U2 = _T2,
#  else
      class _U1,
      class _U2,
#  endif
      __enable_if_t<_CheckArgs::template __is_pair_constructible<_U1, _U2>(), int> = 0 >
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 explicit(!_CheckArgs::template __is_implicit<_U1, _U2>())
      pair(_U1&& __u1, _U2&& __u2) noexcept(is_nothrow_constructible<first_type, _U1>::value &&
                                            is_nothrow_constructible<second_type, _U2>::value)
      : first(std::forward<_U1>(__u1)), second(std::forward<_U2>(__u2)) {
  }

template <class _U1,
            class _U2,
            __enable_if_t<_CheckArgs::template __is_pair_constructible<_U1 const&, _U2 const&>(), int> = 0>
  _LIBCPP_HIDE_FROM_ABI
  _LIBCPP_CONSTEXPR_SINCE_CXX14 explicit(!_CheckArgs::template __is_implicit<_U1 const&, _U2 const&>())
      pair(pair<_U1, _U2> const& __p) noexcept(is_nothrow_constructible<first_type, _U1 const&>::value &&
                                               is_nothrow_constructible<second_type, _U2 const&>::value)
      : first(__p.first), second(__p.second) {}

template <class _U1, class _U2, __enable_if_t<_CheckArgs::template __is_pair_constructible<_U1, _U2>(), int> = 0>
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 explicit(!_CheckArgs::template __is_implicit<_U1, _U2>())
      pair(pair<_U1, _U2>&& __p) noexcept(is_nothrow_constructible<first_type, _U1&&>::value &&
                                          is_nothrow_constructible<second_type, _U2&&>::value)
      : first(std::forward<_U1>(__p.first)), second(std::forward<_U2>(__p.second)) {}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair&
  operator=(__conditional_t<!__has_defaulted_members::value && is_copy_assignable<first_type>::value &&
                                is_copy_assignable<second_type>::value,
                            pair,
                            __nat> const& __p) noexcept(is_nothrow_copy_assignable<first_type>::value &&
                                                        is_nothrow_copy_assignable<second_type>::value) {
    first  = __p.first;
    second = __p.second;
    return *this;
  }

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair&
  operator=(__conditional_t<!__has_defaulted_members::value && is_move_assignable<first_type>::value &&
                                is_move_assignable<second_type>::value,
                            pair,
                            __nat>&& __p) noexcept(is_nothrow_move_assignable<first_type>::value &&
                                                   is_nothrow_move_assignable<second_type>::value) {
    first  = std::forward<first_type>(__p.first);
    second = std::forward<second_type>(__p.second);
    return *this;
  }

template <
      class _U1,
      class _U2,
      __enable_if_t<is_assignable<first_type&, _U1 const&>::value && is_assignable<second_type&, _U2 const&>::value,
                    int> = 0>
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair& operator=(pair<_U1, _U2> const& __p) {
    first  = __p.first;
    second = __p.second;
    return *this;
  }

template <class _U1,
            class _U2,
            __enable_if_t<is_assignable<first_type&, _U1>::value && is_assignable<second_type&, _U2>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair& operator=(pair<_U1, _U2>&& __p) {
    first  = std::forward<_U1>(__p.first);
    second = std::forward<_U2>(__p.second);
    return *this;
  }

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void swap(pair& __p)
      _NOEXCEPT_(__is_nothrow_swappable_v<first_type>&& __is_nothrow_swappable_v<second_type>) {
    using std::swap;
    swap(first, __p.first);
    swap(second, __p.second);
  }

#if _LIBCPP_STD_VER >= 23
  _LIBCPP_HIDE_FROM_ABI constexpr void swap(const pair& __p) const
      noexcept(__is_nothrow_swappable_v<const first_type> && __is_nothrow_swappable_v<const second_type>) {
    using std::swap;
    swap(first, __p.first);
    swap(second, __p.second);
  }
#endif

private:
#ifndef _LIBCPP_CXX03_LANG
  template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  pair(piecewise_construct_t,
       tuple<_Args1...>& __first_args,
       tuple<_Args2...>& __second_args,
       __tuple_indices<_I1...>,
       __tuple_indices<_I2...>)
      : first(std::forward<_Args1>(std::get<_I1>(__first_args))...),
        second(std::forward<_Args2>(std::get<_I2>(__second_args))...) {}
#endif
};

#if _LIBCPP_STD_VER >= 17
template <class _T1, class _T2>
pair(_T1, _T2) -> pair<_T1, _T2>;
#endif

// [pairs.spec], specialized algorithms

template <class _T1, class _T2, class _U1, class _U2>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
operator==(const pair<_T1, _T2>& __x, const pair<_U1, _U2>& __y) {
  return __x.first == __y.first && __x.second == __y.second;
}

#if _LIBCPP_STD_VER >= 20

template <class _T1, class _T2, class _U1, class _U2>
_LIBCPP_HIDE_FROM_ABI constexpr common_comparison_category_t< __synth_three_way_result<_T1, _U1>,
                                                              __synth_three_way_result<_T2, _U2> >
operator<=>(const pair<_T1, _T2>& __x, const pair<_U1, _U2>& __y) {
  if (auto __c = std::__synth_three_way(__x.first, __y.first); __c != 0) {
    return __c;
  }
  return std::__synth_three_way(__x.second, __y.second);
}

#else // _LIBCPP_STD_VER >= 20

template <class _T1, class _T2, class _U1, class _U2>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
operator!=(const pair<_T1, _T2>& __x, const pair<_U1, _U2>& __y) {
  return !(__x == __y);
}

template <class _T1, class _T2, class _U1, class _U2>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
operator<(const pair<_T1, _T2>& __x, const pair<_U1, _U2>& __y) {
  return __x.first < __y.first || (!(__y.first < __x.first) && __x.second < __y.second);
}

template <class _T1, class _T2, class _U1, class _U2>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
operator>(const pair<_T1, _T2>& __x, const pair<_U1, _U2>& __y) {
  return __y < __x;
}

template <class _T1, class _T2, class _U1, class _U2>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
operator>=(const pair<_T1, _T2>& __x, const pair<_U1, _U2>& __y) {
  return !(__x < __y);
}

template <class _T1, class _T2, class _U1, class _U2>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
operator<=(const pair<_T1, _T2>& __x, const pair<_U1, _U2>& __y) {
  return !(__y < __x);
}

#endif // _LIBCPP_STD_VER >= 20

#if _LIBCPP_STD_VER >= 23
template <class _T1, class _T2, class _U1, class _U2, template <class> class _TQual, template <class> class _UQual>
  requires requires {
    typename pair<common_reference_t<_TQual<_T1>, _UQual<_U1>>, common_reference_t<_TQual<_T2>, _UQual<_U2>>>;
  }
struct basic_common_reference<pair<_T1, _T2>, pair<_U1, _U2>, _TQual, _UQual> {
  using type = pair<common_reference_t<_TQual<_T1>, _UQual<_U1>>, common_reference_t<_TQual<_T2>, _UQual<_U2>>>;
};

template <class _T1, class _T2, class _U1, class _U2>
  requires requires { typename pair<common_type_t<_T1, _U1>, common_type_t<_T2, _U2>>; }
struct common_type<pair<_T1, _T2>, pair<_U1, _U2>> {
  using type = pair<common_type_t<_T1, _U1>, common_type_t<_T2, _U2>>;
};
#endif // _LIBCPP_STD_VER >= 23

template <class _T1, class _T2, __enable_if_t<__is_swappable_v<_T1> && __is_swappable_v<_T2>, int> = 0>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
    _NOEXCEPT_(__is_nothrow_swappable_v<_T1>&& __is_nothrow_swappable_v<_T2>) {
  __x.swap(__y);
}

#if _LIBCPP_STD_VER >= 23
template <class _T1, class _T2>
  requires(__is_swappable_v<const _T1> && __is_swappable_v<const _T2>)
_LIBCPP_HIDE_FROM_ABI constexpr void
swap(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) noexcept(noexcept(__x.swap(__y))) {
  __x.swap(__y);
}
#endif

template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR_SINCE_CXX14 pair<typename __unwrap_ref_decay<_T1>::type, typename __unwrap_ref_decay<_T2>::type>
make_pair(_T1&& __t1, _T2&& __t2) {
  return pair<typename __unwrap_ref_decay<_T1>::type, typename __unwrap_ref_decay<_T2>::type>(
      std::forward<_T1>(__t1), std::forward<_T2>(__t2));
}

template <class _T1, class _T2>
struct _LIBCPP_TEMPLATE_VIS tuple_size<pair<_T1, _T2> > : public integral_constant<size_t, 2> {};

template <size_t _Ip, class _T1, class _T2>
struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, pair<_T1, _T2> > {
  static_assert(_Ip < 2, "Index out of bounds in std::tuple_element<std::pair<T1, T2>>");
};

template <class _T1, class _T2>
struct _LIBCPP_TEMPLATE_VIS tuple_element<0, pair<_T1, _T2> > {
  using type _LIBCPP_NODEBUG = _T1;
};

template <class _T1, class _T2>
struct _LIBCPP_TEMPLATE_VIS tuple_element<1, pair<_T1, _T2> > {
  using type _LIBCPP_NODEBUG = _T2;
};

template <size_t _Ip>
struct __get_pair;

template <>
struct __get_pair<0> {
  template <class _T1, class _T2>
  static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _T1& get(pair<_T1, _T2>& __p) _NOEXCEPT {
    return __p.first;
  }

template <class _T1, class _T2>
  static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const _T1& get(const pair<_T1, _T2>& __p) _NOEXCEPT {
    return __p.first;
  }

template <class _T1, class _T2>
  static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _T1&& get(pair<_T1, _T2>&& __p) _NOEXCEPT {
    return std::forward<_T1>(__p.first);
  }

template <class _T1, class _T2>
  static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const _T1&& get(const pair<_T1, _T2>&& __p) _NOEXCEPT {
    return std::forward<const _T1>(__p.first);
  }
};

template <>
struct __get_pair<1> {
  template <class _T1, class _T2>
  static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _T2& get(pair<_T1, _T2>& __p) _NOEXCEPT {
    return __p.second;
  }

template <class _T1, class _T2>
  static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const _T2& get(const pair<_T1, _T2>& __p) _NOEXCEPT {
    return __p.second;
  }

template <class _T1, class _T2>
  static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _T2&& get(pair<_T1, _T2>&& __p) _NOEXCEPT {
    return std::forward<_T2>(__p.second);
  }

template <class _T1, class _T2>
  static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const _T2&& get(const pair<_T1, _T2>&& __p) _NOEXCEPT {
    return std::forward<const _T2>(__p.second);
  }
};

template <size_t _Ip, class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 typename tuple_element<_Ip, pair<_T1, _T2> >::type&
get(pair<_T1, _T2>& __p) _NOEXCEPT {
  return __get_pair<_Ip>::get(__p);
}

template <size_t _Ip, class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const typename tuple_element<_Ip, pair<_T1, _T2> >::type&
get(const pair<_T1, _T2>& __p) _NOEXCEPT {
  return __get_pair<_Ip>::get(__p);
}

template <size_t _Ip, class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 typename tuple_element<_Ip, pair<_T1, _T2> >::type&&
get(pair<_T1, _T2>&& __p) _NOEXCEPT {
  return __get_pair<_Ip>::get(std::move(__p));
}

template <size_t _Ip, class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const typename tuple_element<_Ip, pair<_T1, _T2> >::type&&
get(const pair<_T1, _T2>&& __p) _NOEXCEPT {
  return __get_pair<_Ip>::get(std::move(__p));
}

#if _LIBCPP_STD_VER >= 14
template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1& get(pair<_T1, _T2>& __p) _NOEXCEPT {
  return __get_pair<0>::get(__p);
}

template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1 const& get(pair<_T1, _T2> const& __p) _NOEXCEPT {
  return __get_pair<0>::get(__p);
}

template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1&& get(pair<_T1, _T2>&& __p) _NOEXCEPT {
  return __get_pair<0>::get(std::move(__p));
}

template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1 const&& get(pair<_T1, _T2> const&& __p) _NOEXCEPT {
  return __get_pair<0>::get(std::move(__p));
}

template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1& get(pair<_T2, _T1>& __p) _NOEXCEPT {
  return __get_pair<1>::get(__p);
}

template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1 const& get(pair<_T2, _T1> const& __p) _NOEXCEPT {
  return __get_pair<1>::get(__p);
}

template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1&& get(pair<_T2, _T1>&& __p) _NOEXCEPT {
  return __get_pair<1>::get(std::move(__p));
}

template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1 const&& get(pair<_T2, _T1> const&& __p) _NOEXCEPT {
  return __get_pair<1>::get(std::move(__p));
}

#endif // _LIBCPP_STD_VER >= 14

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___UTILITY_PAIR_H

#include <utility>
#include <memory>
#include <cassert>
#include <type_traits>
#include <string_view>

int main(int, char**) {
  // Nico's example
  {
    struct OpIndex {
      int offset_;
    };

using Pair = std::pair<int, const OpIndex>;
    static_assert(!std::is_copy_assignable<Pair>::value);
    static_assert(!std::is_move_assignable<Pair>::value);

static_assert(std::is_trivially_copyable<Pair>::value);
  }

return 0;
}