// -*- 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
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___FUNCTIONAL_BIND_H
#define _LIBCPP___FUNCTIONAL_BIND_H

#include <__config>
#include <__functional/invoke.h>
#include <__functional/weak_result_type.h>
#include <__type_traits/decay.h>
#include <__type_traits/is_reference_wrapper.h>
#include <__type_traits/is_void.h>
#include <cstddef>
#include <tuple>

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

_LIBCPP_BEGIN_NAMESPACE_STD

template<class _Tp>
struct is_bind_expression : _If<
    _IsSame<_Tp, __remove_cvref_t<_Tp> >::value,
    false_type,
    is_bind_expression<__remove_cvref_t<_Tp> >
> {};

#if _LIBCPP_STD_VER >= 17
template <class _Tp>
inline constexpr bool is_bind_expression_v = is_bind_expression<_Tp>::value;
#endif

template<class _Tp>
struct is_placeholder : _If<
    _IsSame<_Tp, __remove_cvref_t<_Tp> >::value,
    integral_constant<int, 0>,
    is_placeholder<__remove_cvref_t<_Tp> >
> {};

#if _LIBCPP_STD_VER >= 17
template <class _Tp>
inline constexpr int is_placeholder_v = is_placeholder<_Tp>::value;
#endif

namespace placeholders
{

template <int _Np> struct __ph {};

// C++17 recommends that we implement placeholders as `inline constexpr`, but allows
// implementing them as `extern <implementation-defined>`. Libc++ implements them as
// `extern const` in all standard modes to avoid an ABI break in C++03: making them
// `inline constexpr` requires removing their definition in the shared library to
// avoid ODR violations, which is an ABI break.
//
// In practice, since placeholders are empty, `extern const` is almost impossible
// to distinguish from `inline constexpr` from a usage stand point.
_LIBCPP_EXPORTED_FROM_ABI extern const __ph<1>   _1;
_LIBCPP_EXPORTED_FROM_ABI extern const __ph<2>   _2;
_LIBCPP_EXPORTED_FROM_ABI extern const __ph<3>   _3;
_LIBCPP_EXPORTED_FROM_ABI extern const __ph<4>   _4;
_LIBCPP_EXPORTED_FROM_ABI extern const __ph<5>   _5;
_LIBCPP_EXPORTED_FROM_ABI extern const __ph<6>   _6;
_LIBCPP_EXPORTED_FROM_ABI extern const __ph<7>   _7;
_LIBCPP_EXPORTED_FROM_ABI extern const __ph<8>   _8;
_LIBCPP_EXPORTED_FROM_ABI extern const __ph<9>   _9;
_LIBCPP_EXPORTED_FROM_ABI extern const __ph<10> _10;

} // namespace placeholders

template<int _Np>
struct is_placeholder<placeholders::__ph<_Np> >
    : public integral_constant<int, _Np> {};


#ifndef _LIBCPP_CXX03_LANG

template <class _Tp, class _Uj>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
_Tp&
__mu(reference_wrapper<_Tp> __t, _Uj&)
{
    return __t.get();
}

template <class _Ti, class ..._Uj, size_t ..._Indx>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
typename __invoke_of<_Ti&, _Uj...>::type
__mu_expand(_Ti& __ti, tuple<_Uj...>& __uj, __tuple_indices<_Indx...>)
{
    return __ti(_VSTD::forward<_Uj>(_VSTD::get<_Indx>(__uj))...);
}

template <class _Ti, class ..._Uj>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
typename __enable_if_t
<
    is_bind_expression<_Ti>::value,
    __invoke_of<_Ti&, _Uj...>
>::type
__mu(_Ti& __ti, tuple<_Uj...>& __uj)
{
    typedef typename __make_tuple_indices<sizeof...(_Uj)>::type __indices;
    return _VSTD::__mu_expand(__ti, __uj, __indices());
}

template <bool IsPh, class _Ti, class _Uj>
struct __mu_return2 {};

template <class _Ti, class _Uj>
struct __mu_return2<true, _Ti, _Uj>
{
    typedef typename tuple_element<is_placeholder<_Ti>::value - 1, _Uj>::type type;
};

template <class _Ti, class _Uj>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
typename enable_if
<
    0 < is_placeholder<_Ti>::value,
    typename __mu_return2<0 < is_placeholder<_Ti>::value, _Ti, _Uj>::type
>::type
__mu(_Ti&, _Uj& __uj)
{
    const size_t __indx = is_placeholder<_Ti>::value - 1;
    return _VSTD::forward<typename tuple_element<__indx, _Uj>::type>(_VSTD::get<__indx>(__uj));
}

template <class _Ti, class _Uj>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
typename enable_if
<
    !is_bind_expression<_Ti>::value &&
    is_placeholder<_Ti>::value == 0 &&
    !__is_reference_wrapper<_Ti>::value,
    _Ti&
>::type
__mu(_Ti& __ti, _Uj&)
{
    return __ti;
}

template <class _Ti, bool IsReferenceWrapper, bool IsBindEx, bool IsPh,
          class _TupleUj>
struct __mu_return_impl;

template <bool _Invokable, class _Ti, class ..._Uj>
struct __mu_return_invokable  // false
{
    typedef __nat type;
};

template <class _Ti, class ..._Uj>
struct __mu_return_invokable<true, _Ti, _Uj...>
{
    typedef typename __invoke_of<_Ti&, _Uj...>::type type;
};

template <class _Ti, class ..._Uj>
struct __mu_return_impl<_Ti, false, true, false, tuple<_Uj...> >
    : public __mu_return_invokable<__invokable<_Ti&, _Uj...>::value, _Ti, _Uj...>
{
};

template <class _Ti, class _TupleUj>
struct __mu_return_impl<_Ti, false, false, true, _TupleUj>
{
    typedef typename tuple_element<is_placeholder<_Ti>::value - 1,
                                   _TupleUj>::type&& type;
};

template <class _Ti, class _TupleUj>
struct __mu_return_impl<_Ti, true, false, false, _TupleUj>
{
    typedef typename _Ti::type& type;
};

template <class _Ti, class _TupleUj>
struct __mu_return_impl<_Ti, false, false, false, _TupleUj>
{
    typedef _Ti& type;
};

template <class _Ti, class _TupleUj>
struct __mu_return
    : public __mu_return_impl<_Ti,
                              __is_reference_wrapper<_Ti>::value,
                              is_bind_expression<_Ti>::value,
                              0 < is_placeholder<_Ti>::value &&
                              is_placeholder<_Ti>::value <= tuple_size<_TupleUj>::value,
                              _TupleUj>
{
};

template <class _Fp, class _BoundArgs, class _TupleUj>
struct __is_valid_bind_return
{
    static const bool value = false;
};

template <class _Fp, class ..._BoundArgs, class _TupleUj>
struct __is_valid_bind_return<_Fp, tuple<_BoundArgs...>, _TupleUj>
{
    static const bool value = __invokable<_Fp,
                    typename __mu_return<_BoundArgs, _TupleUj>::type...>::value;
};

template <class _Fp, class ..._BoundArgs, class _TupleUj>
struct __is_valid_bind_return<_Fp, const tuple<_BoundArgs...>, _TupleUj>
{
    static const bool value = __invokable<_Fp,
                    typename __mu_return<const _BoundArgs, _TupleUj>::type...>::value;
};

template <class _Fp, class _BoundArgs, class _TupleUj,
          bool = __is_valid_bind_return<_Fp, _BoundArgs, _TupleUj>::value>
struct __bind_return;

template <class _Fp, class ..._BoundArgs, class _TupleUj>
struct __bind_return<_Fp, tuple<_BoundArgs...>, _TupleUj, true>
{
    typedef typename __invoke_of
    <
        _Fp&,
        typename __mu_return
        <
            _BoundArgs,
            _TupleUj
        >::type...
    >::type type;
};

template <class _Fp, class ..._BoundArgs, class _TupleUj>
struct __bind_return<_Fp, const tuple<_BoundArgs...>, _TupleUj, true>
{
    typedef typename __invoke_of
    <
        _Fp&,
        typename __mu_return
        <
            const _BoundArgs,
            _TupleUj
        >::type...
    >::type type;
};

template <class _Fp, class _BoundArgs, size_t ..._Indx, class _Args>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
typename __bind_return<_Fp, _BoundArgs, _Args>::type
__apply_functor(_Fp& __f, _BoundArgs& __bound_args, __tuple_indices<_Indx...>,
                _Args&& __args)
{
    return _VSTD::__invoke(__f, _VSTD::__mu(_VSTD::get<_Indx>(__bound_args), __args)...);
}

template<class _Fp, class ..._BoundArgs>
class __bind : public __weak_result_type<__decay_t<_Fp> >
{
protected:
    using _Fd = __decay_t<_Fp>;
    typedef tuple<__decay_t<_BoundArgs>...> _Td;
private:
    _Fd __f_;
    _Td __bound_args_;

    typedef typename __make_tuple_indices<sizeof...(_BoundArgs)>::type __indices;
public:
    template <class _Gp, class ..._BA,
              class = typename enable_if
                               <
                                  is_constructible<_Fd, _Gp>::value &&
                                  !is_same<__libcpp_remove_reference_t<_Gp>,
                                           __bind>::value
                               >::type>
      _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
      explicit __bind(_Gp&& __f, _BA&& ...__bound_args)
        : __f_(_VSTD::forward<_Gp>(__f)),
          __bound_args_(_VSTD::forward<_BA>(__bound_args)...) {}

    template <class ..._Args>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
        typename __bind_return<_Fd, _Td, tuple<_Args&&...> >::type
        operator()(_Args&& ...__args)
        {
            return _VSTD::__apply_functor(__f_, __bound_args_, __indices(),
                                  tuple<_Args&&...>(_VSTD::forward<_Args>(__args)...));
        }

    template <class ..._Args>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
        typename __bind_return<const _Fd, const _Td, tuple<_Args&&...> >::type
        operator()(_Args&& ...__args) const
        {
            return _VSTD::__apply_functor(__f_, __bound_args_, __indices(),
                                   tuple<_Args&&...>(_VSTD::forward<_Args>(__args)...));
        }
};

template<class _Fp, class ..._BoundArgs>
struct is_bind_expression<__bind<_Fp, _BoundArgs...> > : public true_type {};

template<class _Rp, class _Fp, class ..._BoundArgs>
class __bind_r
    : public __bind<_Fp, _BoundArgs...>
{
    typedef __bind<_Fp, _BoundArgs...> base;
    typedef typename base::_Fd _Fd;
    typedef typename base::_Td _Td;
public:
    typedef _Rp result_type;


    template <class _Gp, class ..._BA,
              class = typename enable_if
                               <
                                  is_constructible<_Fd, _Gp>::value &&
                                  !is_same<__libcpp_remove_reference_t<_Gp>,
                                           __bind_r>::value
                               >::type>
      _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
      explicit __bind_r(_Gp&& __f, _BA&& ...__bound_args)
        : base(_VSTD::forward<_Gp>(__f),
               _VSTD::forward<_BA>(__bound_args)...) {}

    template <class ..._Args>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
        typename enable_if
        <
            is_convertible<typename __bind_return<_Fd, _Td, tuple<_Args&&...> >::type,
                           result_type>::value || is_void<_Rp>::value,
            result_type
        >::type
        operator()(_Args&& ...__args)
        {
            typedef __invoke_void_return_wrapper<_Rp> _Invoker;
            return _Invoker::__call(static_cast<base&>(*this), _VSTD::forward<_Args>(__args)...);
        }

    template <class ..._Args>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
        typename enable_if
        <
            is_convertible<typename __bind_return<const _Fd, const _Td, tuple<_Args&&...> >::type,
                           result_type>::value || is_void<_Rp>::value,
            result_type
        >::type
        operator()(_Args&& ...__args) const
        {
            typedef __invoke_void_return_wrapper<_Rp> _Invoker;
            return _Invoker::__call(static_cast<base const&>(*this), _VSTD::forward<_Args>(__args)...);
        }
};

template<class _Rp, class _Fp, class ..._BoundArgs>
struct is_bind_expression<__bind_r<_Rp, _Fp, _BoundArgs...> > : public true_type {};

template<class _Fp, class ..._BoundArgs>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
__bind<_Fp, _BoundArgs...>
bind(_Fp&& __f, _BoundArgs&&... __bound_args)
{
    typedef __bind<_Fp, _BoundArgs...> type;
    return type(_VSTD::forward<_Fp>(__f), _VSTD::forward<_BoundArgs>(__bound_args)...);
}

template<class _Rp, class _Fp, class ..._BoundArgs>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
__bind_r<_Rp, _Fp, _BoundArgs...>
bind(_Fp&& __f, _BoundArgs&&... __bound_args)
{
    typedef __bind_r<_Rp, _Fp, _BoundArgs...> type;
    return type(_VSTD::forward<_Fp>(__f), _VSTD::forward<_BoundArgs>(__bound_args)...);
}

#endif // _LIBCPP_CXX03_LANG

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___FUNCTIONAL_BIND_H