include/unifex/with_query_value.hpp

/*
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * Licensed under the Apache License Version 2.0 with LLVM Exceptions
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *   https://llvm.org/LICENSE.txt
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#pragma once

#include <unifex/get_allocator.hpp>
#include <unifex/receiver_concepts.hpp>
#include <unifex/sender_concepts.hpp>
#include <unifex/tag_invoke.hpp>
#include <unifex/bind_back.hpp>

#include <unifex/detail/prologue.hpp>

namespace unifex {
namespace _with_query_value {

template <typename CPO, typename Value, typename Receiver>
struct _receiver_wrapper {
  class type;
};
template <typename CPO, typename Value, typename Receiver>
using receiver_wrapper = typename _receiver_wrapper<CPO, Value, Receiver>::type;

template <typename CPO, typename Value, typename Receiver>
class _receiver_wrapper<CPO, Value, Receiver>::type {
 public:
  template <typename Receiver2>
  explicit type(Receiver2 &&receiver, const Value& val)
    : receiver_((Receiver2 &&) receiver)
    , val_(&val) {}

 private:
  friend const Value &tag_invoke(CPO, const type &r) noexcept {
    return *r.val_;
  }

  template(typename OtherCPO, typename Self, typename... Args)
    (requires same_as<remove_cvref_t<Self>, type> AND
              callable<OtherCPO, member_t<Self, Receiver>, Args...>)
  friend auto tag_invoke(OtherCPO cpo, Self&& self, Args&&... args)
      noexcept(is_nothrow_callable_v<OtherCPO, member_t<Self, Receiver>, Args...>)
      -> callable_result_t<OtherCPO, member_t<Self, Receiver>, Args...> {
    return static_cast<OtherCPO&&>(cpo)(static_cast<Self&&>(self).receiver_, static_cast<Args&&>(args)...);
  }

  Receiver receiver_;
  const Value* val_;
};

template <typename CPO, typename Value, typename Sender, typename Receiver>
struct _op {
  class type;
};
template <typename CPO, typename Value, typename Sender, typename Receiver>
using operation = typename _op<CPO, Value, Sender, remove_cvref_t<Receiver>>::type;

template <typename CPO, typename Value, typename Sender, typename Receiver>
class _op<CPO, Value, Sender, Receiver>::type {
 public:
  template <typename Receiver2, typename Value2>
  explicit type(Sender &&sender, Receiver2 &&receiver, Value2 &&value)
    : value_((Value2 &&) value)
    , innerOp_(
          connect((Sender &&) sender,
                  receiver_wrapper<CPO, Value, Receiver>{
                      (Receiver2 &&) receiver, value_})) {}

  void start() & noexcept {
    unifex::start(innerOp_);
  }

 private:
  UNIFEX_NO_UNIQUE_ADDRESS Value value_;
  /*UNIFEX_NO_UNIQUE_ADDRESS*/
  connect_result_t<Sender, receiver_wrapper<CPO, Value, Receiver>> innerOp_;
};

template <typename CPO, typename Value, typename Sender>
struct _sender {
  class type;
};
template <typename CPO, typename Value, typename Sender>
using sender =
    typename _sender<CPO, std::decay_t<Value>, remove_cvref_t<Sender>>::type;

template <typename CPO, typename Value, typename Sender>
class _sender<CPO, Value, Sender>::type {
public:
  template <template <typename...> class Variant,
            template <typename...> class Tuple>
  using value_types = sender_value_types_t<Sender, Variant, Tuple>;

  template <template <typename...> class Variant>
  using error_types = sender_error_types_t<Sender, Variant>;

  static constexpr bool sends_done = sender_traits<Sender>::sends_done;

  template <typename Sender2, typename Value2>
  explicit type(Sender2 &&sender, Value2 &&value)
    : sender_((Sender2 &&) sender), value_((Value &&) value) {}

  template(typename Self, typename Receiver)
    (requires same_as<remove_cvref_t<Self>, type> AND
      constructible_from<Value, member_t<Self, Value>> AND
      sender_to<
        member_t<Self, Sender>,
        receiver_wrapper<CPO, Value, remove_cvref_t<Receiver>>>)
  friend auto tag_invoke(tag_t<unifex::connect>, Self&& s, Receiver &&receiver)
      noexcept(std::is_nothrow_constructible_v<Value, member_t<Self, Value>> &&
               is_nothrow_connectable_v<
                  member_t<Self, Sender>,
                  receiver_wrapper<CPO, Value, remove_cvref_t<Receiver>>>)
      -> operation<CPO, Value, member_t<Self, Sender>, Receiver> {
    return operation<CPO, Value, member_t<Self, Sender>, Receiver>{
        static_cast<Self&&>(s).sender_,
        static_cast<Receiver &&>(receiver),
        static_cast<Self&&>(s).value_};
  }

private:
  Sender sender_;
  Value value_;
};
} // namespace _with_query_value

namespace _with_query_value_cpo {
  inline const struct _fn {
    template <typename Sender, typename CPO, typename Value>
    _with_query_value::sender<CPO, Value, Sender>
    operator()(Sender &&sender, CPO, Value &&value) const {
      static_assert(
          std::is_empty_v<CPO>,
          "with_query_value() does not support stateful CPOs");
      return _with_query_value::sender<CPO, Value, Sender>{
          (Sender &&) sender,
          (Value &&) value};
    }
    template <typename CPO, typename Value>
    constexpr auto operator()(const CPO&, Value&& value) const
        noexcept(is_nothrow_callable_v<
          tag_t<bind_back>, _fn, CPO, Value>)
        -> bind_back_result_t<_fn, CPO, Value> {
      return bind_back(*this, CPO{}, (Value&&)value);
    }
  } with_query_value {};
} // namespace _with_query_value_cpo
using _with_query_value_cpo::with_query_value;

} // namespace unifex

#include <unifex/detail/epilogue.hpp>