on_error_resume_next.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/operators/fwd.hpp>
 
#include <rpp/defs.hpp>
#include <rpp/operators/details/strategy.hpp>
 
namespace rpp::operators::details
{
    template<rpp::constraint::observer TObserver>
    struct on_error_resume_next_disposable final : public rpp::composite_disposable
    {
        on_error_resume_next_disposable(TObserver&& observer)
            : rpp::composite_disposable{}
            , observer(std::move(observer))
        {
        }
 
        RPP_NO_UNIQUE_ADDRESS TObserver observer;
    };
 
    template<rpp::constraint::observer TObserver>
    struct on_error_resume_next_inner_observer_strategy
    {
        static constexpr auto preferred_disposables_mode = rpp::details::observers::disposables_mode::None;
 
        std::shared_ptr<TObserver> observer;
 
        template<typename T>
        void on_next(T&& v) const
        {
            observer->on_next(std::forward<T>(v));
        }
 
        void on_error(const std::exception_ptr& err) const
        {
            observer->on_error(err);
        }
 
        void on_completed() const
        {
            observer->on_completed();
        }
 
        void set_upstream(const disposable_wrapper& d) { observer->set_upstream(d); }
 
        bool is_disposed() const { return observer->is_disposed(); }
    };
 
 
    template<rpp::constraint::observer TObserver, rpp::constraint::decayed_type Selector>
    struct on_error_resume_next_observer_strategy
    {
        static constexpr auto preferred_disposables_mode = rpp::details::observers::disposables_mode::None;
 
        on_error_resume_next_observer_strategy(TObserver&& observer, const Selector& selector)
            : state{init_state(std::move(observer))}
            , selector{selector}
        {
        }
 
        std::shared_ptr<on_error_resume_next_disposable<TObserver>> state;
        RPP_NO_UNIQUE_ADDRESS Selector                              selector;
 
        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
            {
                selector(err).subscribe(on_error_resume_next_inner_observer_strategy<TObserver>{std::shared_ptr<TObserver>(state, &state->observer)});
            }
            catch (...)
            {
                state->observer.on_error(std::current_exception());
            }
            state->dispose();
        }
 
        void on_completed() const
        {
            state->observer.on_completed();
        }
 
        void set_upstream(const disposable_wrapper& d) const
        {
            state->add(d);
        }
 
        bool is_disposed() const { return state->is_disposed(); }
 
        static std::shared_ptr<on_error_resume_next_disposable<TObserver>> init_state(TObserver&& observer)
        {
            const auto d   = disposable_wrapper_impl<on_error_resume_next_disposable<TObserver>>::make(std::move(observer));
            auto       ptr = d.lock();
            ptr->observer.set_upstream(d.as_weak());
            return ptr;
        }
    };
 
    template<rpp::constraint::decayed_type Selector>
    struct on_error_resume_next_t : lift_operator<on_error_resume_next_t<Selector>, Selector>
    {
        using lift_operator<on_error_resume_next_t<Selector>, Selector>::lift_operator;
 
        template<rpp::constraint::decayed_type T>
        struct operator_traits
        {
            using selector_observable_result_type =
                rpp::utils::extract_observable_type_t<std::invoke_result_t<Selector, std::exception_ptr>>;
 
            static_assert(
                rpp::constraint::decayed_same_as<selector_observable_result_type, T>,
                "Selector observable result type is not the same as T");
 
            using result_type = T;
 
            template<rpp::constraint::observer_of_type<result_type> TObserver>
            using observer_strategy = on_error_resume_next_observer_strategy<TObserver, Selector>;
        };
 
        template<rpp::details::observables::constraint::disposables_strategy Prev>
        using updated_optimal_disposables_strategy = rpp::details::observables::default_disposables_strategy;
    };
} // namespace rpp::operators::details
 
namespace rpp::operators
{
     * @see https://reactivex.io/documentation/operators/catch.html
     */
    template<typename Selector>
        requires rpp::constraint::observable<std::invoke_result_t<Selector, std::exception_ptr>>
    auto on_error_resume_next(Selector&& selector)
    {
        return details::on_error_resume_next_t<std::decay_t<Selector>>{std::forward<Selector>(selector)};
    }
} // namespace rpp::operators