retry_when.hpp

//                  ReactivePlusPlus library
//
//          Copyright Aleksey Loginov 2023 - 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/AlexInLog/ReactivePlusPlus
//
 
#pragma once
 
#include <rpp/observables/fwd.hpp>
#include <rpp/operators/fwd.hpp>
 
#include <rpp/operators/details/repeating_strategy.hpp>
 
namespace rpp::operators::details
{
    template<rpp::constraint::observer TObserver,
             typename TObservable,
             typename TNotifier>
    struct retry_when_impl_strategy final : public repeating_observer_strategy<TObserver, TObservable, TNotifier>
    {
        using self_type = retry_when_impl_strategy<TObserver, TObservable, TNotifier>;
 
        using repeating_observer_strategy<TObserver, TObservable, TNotifier>::state;
 
        template<typename T>
        void on_next(T&& v) const
        {
            state->observer.on_next(std::forward<T>(v));
        }
 
        void on_error(const std::exception_ptr& err) const
        {
            try
            {
                state->notifier(err).subscribe(repeating_inner_observer_strategy<self_type, TObserver, TObservable, TNotifier>{this->state});
            }
            catch (...)
            {
                state->observer.on_error(std::current_exception());
            }
        }
 
        void on_completed() const
        {
            state->observer.on_completed();
        }
    };
 
    template<rpp::constraint::decayed_type TNotifier>
    struct retry_when_t
    {
        RPP_NO_UNIQUE_ADDRESS TNotifier notifier;
 
        template<rpp::constraint::decayed_type T>
        struct operator_traits
        {
            using result_type = T;
        };
 
        template<rpp::details::observables::constraint::disposables_strategy Prev>
        using updated_optimal_disposables_strategy = rpp::details::observables::fixed_disposables_strategy<1>;
 
        template<rpp::constraint::observer TObserver, typename TObservable>
        void subscribe(TObserver&& observer, TObservable&& observable) const
        {
            const auto d   = disposable_wrapper_impl<repeating_state<std::decay_t<TObserver>, std::decay_t<TObservable>, std::decay_t<TNotifier>>>::make(std::forward<TObserver>(observer), std::forward<TObservable>(observable), notifier);
            auto       ptr = d.lock();
 
            ptr->observer.set_upstream(d.as_weak());
 
            drain<retry_when_impl_strategy<std::decay_t<TObserver>, std::decay_t<TObservable>, std::decay_t<TNotifier>>>(ptr);
        }
    };
} // namespace rpp::operators::details
 
namespace rpp::operators
{
    template<typename TNotifier>
        requires rpp::constraint::observable<std::invoke_result_t<TNotifier, std::exception_ptr>>
    auto retry_when(TNotifier&& notifier)
    {
        return details::retry_when_t<std::decay_t<TNotifier>>{std::forward<TNotifier>(notifier)};
    }
} // namespace rpp::operators