scan.hpp

//                  ReactivePlusPlus library
//
//          Copyright Aleksey Loginov 2022 - present.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          https://www.boost.org/LICENSE_1_0.txt)
//
// Project home: https://github.com/victimsnino/ReactivePlusPlus
//
 
#pragma once
 
#include <rpp/defs.hpp>                                    // RPP_NO_UNIQUE_ADDRESS
#include <rpp/operators/lift.hpp>                          // required due to operator uses lift
#include <rpp/operators/details/subscriber_with_state.hpp> // create_subscriber_with_state
#include <rpp/operators/fwd/scan.hpp>                      // own forwarding
#include <rpp/operators/reduce.hpp>                        // reduce to re-use
#include <rpp/subscribers/constraints.hpp>                 // constraint::subscriber
#include <rpp/utils/functors.hpp>                          // forwarding_on_error
#include <rpp/utils/utilities.hpp>                         // utils::as_const
 
 
IMPLEMENTATION_FILE(scan_tag);
 
namespace rpp::details
{
struct scan_on_next : private reduce_on_next
{
    template<constraint::decayed_type Result, typename AccumulatorFn>
    void operator()(auto&&                                   value,
                    const constraint::subscriber auto&       sub,
                    const reduce_state<Result, AccumulatorFn>& state) const
    {
        reduce_on_next::operator()(std::forward<decltype(value)>(value), sub, state);
        sub.on_next(utils::as_const(state.seed));
    }
};
 
template<constraint::decayed_type Type, constraint::decayed_type Result, scan_accumulator<Result, Type> AccumulatorFn>
struct scan_impl
{
    Result                              initial_value;
    RPP_NO_UNIQUE_ADDRESS AccumulatorFn accumulator;
 
    template<constraint::subscriber_of_type<Result> TSub>
    auto operator()(TSub&& subscriber) const
    {
        auto subscription = subscriber.get_subscription();
        // dynamic_state there to make shared_ptr for observer instead of making shared_ptr for state
        return create_subscriber_with_dynamic_state<Type>(std::move(subscription),
                                                          scan_on_next{},
                                                          utils::forwarding_on_error{},
                                                          utils::forwarding_on_completed{},
                                                          std::forward<TSub>(subscriber),
                                                          reduce_state<Result, AccumulatorFn>{initial_value, accumulator});
    }
};
} // namespace rpp::details