continuable/include/continuable/detail/connection/connection-all.hpp

/*

                        /~` _  _ _|_. _     _ |_ | _
                        \_,(_)| | | || ||_|(_||_)|(/_

                    https://github.com/Naios/continuable
                                   v4.0.0

  Copyright(c) 2015 - 2019 Denis Blank <denis.blank at outlook dot com>

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files(the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions :

  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
**/

#ifndef CONTINUABLE_DETAIL_CONNECTION_ALL_HPP_INCLUDED
#define CONTINUABLE_DETAIL_CONNECTION_ALL_HPP_INCLUDED

#include <atomic>
#include <memory>
#include <mutex>
#include <tuple>
#include <type_traits>
#include <utility>
#include <continuable/continuable-primitives.hpp>
#include <continuable/detail/connection/connection-aggregated.hpp>
#include <continuable/detail/connection/connection.hpp>
#include <continuable/detail/core/annotation.hpp>
#include <continuable/detail/core/base.hpp>
#include <continuable/detail/core/types.hpp>
#include <continuable/detail/utility/traits.hpp>

namespace cti {
namespace detail {
namespace connection {
namespace all {
/// Caches the partial results and invokes the callback when all results
/// are arrived. This class is thread safe.
template <typename Callback, typename Result>
class result_submitter
    : public std::enable_shared_from_this<result_submitter<Callback, Result>>,
      public util::non_movable {

  Callback callback_;
  Result result_;

  std::atomic<std::size_t> left_;
  std::once_flag flag_;

  // Invokes the callback with the cached result
  void invoke() {
    assert((left_ == 0U) && "Expected that the submitter is finished!");
    std::atomic_thread_fence(std::memory_order_acquire);

    // Call the final callback with the cleaned result
    std::call_once(flag_, [&] {
      aggregated::finalize_data(std::move(callback_), std::move(result_));
    });
  }

  // Completes one result
  void complete_one() {
    assert((left_ > 0U) && "Expected that the submitter isn't finished!");

    auto const current = --left_;
    if (!current) {
      invoke();
    }
  }

  template <typename Box>
  struct partial_all_callback {
    Box* box;
    std::shared_ptr<result_submitter> me;

    template <typename... Args>
    void operator()(Args&&... args) && {

      // Assign the result to the target
      box->assign(std::forward<decltype(args)>(args)...);

      // Complete one result
      me->complete_one();
    }

    template <typename... PartialArgs>
    void operator()(exception_arg_t tag, exception_t exception) && {
      // We never complete the connection, but we forward the first error
      // which was raised.
      std::call_once(me->flag_, std::move(me->callback_), tag,
                     std::move(exception));
    }
  };

public:
  explicit result_submitter(Callback callback, Result&& result)
      : callback_(std::move(callback)), result_(std::move(result)), left_(1) {
  }

  /// Creates a submitter which submits it's result into the storage
  template <typename Box>
  auto create_callback(Box* box) {
    left_.fetch_add(1, std::memory_order_seq_cst);
    return partial_all_callback<std::decay_t<Box>>{box,
                                                   this->shared_from_this()};
  }

  /// Initially the counter is created with an initial count of 1 in order
  /// to prevent that the connection is finished before all callbacks
  /// were registered.
  void accept() {
    complete_one();
  }

  constexpr auto& head() noexcept {
    return result_;
  }
};

template <typename Submitter>
struct continuable_dispatcher {
  std::shared_ptr<Submitter>& submitter;

  template <typename Box, std::enable_if_t<aggregated::is_continuable_box<
                              std::decay_t<Box>>::value>* = nullptr>
  void operator()(Box&& box) const {
    // Retrieve a callback from the submitter and attach it to the continuable
    box.fetch().next(submitter->create_callback(std::addressof(box))).done();
  }
};
} // namespace all

struct connection_strategy_all_tag {};
template <>
struct is_connection_strategy<connection_strategy_all_tag> // ...
    : std::true_type {};

/// Finalizes the all logic of a given connection
template <>
struct connection_finalizer<connection_strategy_all_tag> {
  /// Finalizes the all logic of a given connection
  template <typename Connection>
  static auto finalize(Connection&& connection, util::ownership ownership) {
    // Create the target result from the connection
    auto result =
        aggregated::box_continuables(std::forward<Connection>(connection));

    auto signature = aggregated::hint_of_data<decltype(result)>();

    return base::attorney::create_from(
        [result = std::move(result)](auto&& callback) mutable {
          using submitter_t =
              all::result_submitter<std::decay_t<decltype(callback)>,
                                    std::decay_t<decltype(result)>>;

          // Create the shared state which holds the result
          // and the final callback
          auto state = std::make_shared<submitter_t>(
              std::forward<decltype(callback)>(callback), std::move(result));

          // Dispatch the continuables and store its partial result
          // in the whole result
          traverse_pack(all::continuable_dispatcher<submitter_t>{state},
                        state->head());

          // Finalize the connection if all results arrived in-place
          state->accept();
        },
        signature, std::move(ownership));
  }
};
} // namespace connection

/// Specialization for a connection annotation
template <>
struct annotation_trait<connection::connection_strategy_all_tag>
    : connection::connection_annotation_trait<
          connection::connection_strategy_all_tag> {};

} // namespace detail
} // namespace cti

#endif // CONTINUABLE_DETAIL_CONNECTION_ALL_HPP_INCLUDED