rx-window.hpp

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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.

#pragma once

#if !defined(RXCPP_OPERATORS_RX_WINDOW_HPP)
#define RXCPP_OPERATORS_RX_WINDOW_HPP

#include "../rx-includes.hpp"

namespace rxcpp {

namespace operators {

namespace detail {

template<class... AN>
struct window_invalid_arguments {};

template<class... AN>
struct window_invalid : public rxo::operator_base<window_invalid_arguments<AN...>> {
    using type = observable<window_invalid_arguments<AN...>, window_invalid<AN...>>;
};
template<class... AN>
using window_invalid_t = typename window_invalid<AN...>::type;

template<class T>
struct window
{
    typedef rxu::decay_t<T> source_value_type;
    typedef observable<source_value_type> value_type;

    struct window_values
    {
        window_values(int c, int s)
            : count(c)
            , skip(s)
        {
        }
        int count;
        int skip;
    };

    window_values initial;

    window(int count, int skip)
        : initial(count, skip)
    {
    }

    template<class Subscriber>
    struct window_observer : public window_values
    {
        typedef window_observer<Subscriber> this_type;
        typedef rxu::decay_t<T> value_type;
        typedef rxu::decay_t<Subscriber> dest_type;
        typedef observer<T, this_type> observer_type;
        dest_type dest;
        mutable int cursor;
        mutable std::deque<rxcpp::subjects::subject<T>> subj;

        window_observer(dest_type d, window_values v)
            : window_values(v)
            , dest(std::move(d))
            , cursor(0)
        {
            subj.push_back(rxcpp::subjects::subject<T>());
            dest.on_next(subj[0].get_observable().as_dynamic());
        }
        void on_next(T v) const {
            for (auto s : subj) {
                s.get_subscriber().on_next(v);
            }

            int c = cursor - this->count + 1;
            if (c >= 0 && c % this->skip == 0) {
                subj[0].get_subscriber().on_completed();
                subj.pop_front();
            }

            if (++cursor % this->skip == 0) {
                subj.push_back(rxcpp::subjects::subject<T>());
                dest.on_next(subj[subj.size() - 1].get_observable().as_dynamic());
            }
        }

        void on_error(std::exception_ptr e) const {
            for (auto s : subj) {
                s.get_subscriber().on_error(e);
            }
            dest.on_error(e);
        }

        void on_completed() const {
            for (auto s : subj) {
                s.get_subscriber().on_completed();
            }
            dest.on_completed();
        }

        static subscriber<T, observer_type> make(dest_type d, window_values v) {
            auto cs = d.get_subscription();
            return make_subscriber<T>(std::move(cs), observer_type(this_type(std::move(d), std::move(v))));
        }
    };

    template<class Subscriber>
    auto operator()(Subscriber dest) const
        -> decltype(window_observer<Subscriber>::make(std::move(dest), initial)) {
        return      window_observer<Subscriber>::make(std::move(dest), initial);
    }
};

}

template<class... AN>
auto window(AN&&... an)
    ->      operator_factory<window_tag, AN...> {
     return operator_factory<window_tag, AN...>(std::make_tuple(std::forward<AN>(an)...));
}

}

template<>
struct member_overload<window_tag>
{
    template<class Observable,
        class Enabled = rxu::enable_if_all_true_type_t<
            is_observable<Observable>>,
        class SourceValue = rxu::value_type_t<Observable>,
        class Window = rxo::detail::window<SourceValue>,
        class Value = rxu::value_type_t<Window>>
    static auto member(Observable&& o, int count, int skip)
        -> decltype(o.template lift<Value>(Window(count, skip))) {
        return      o.template lift<Value>(Window(count, skip));
    }

     template<class Observable,
        class Enabled = rxu::enable_if_all_true_type_t<
            is_observable<Observable>>,
        class SourceValue = rxu::value_type_t<Observable>,
        class Window = rxo::detail::window<SourceValue>,
        class Value = rxu::value_type_t<Window>>
    static auto member(Observable&& o, int count)
        -> decltype(o.template lift<Value>(Window(count, count))) {
        return      o.template lift<Value>(Window(count, count));
    }

    template<class... AN>
    static operators::detail::window_invalid_t<AN...> member(AN...) {
        std::terminate();
        return {};
        static_assert(sizeof...(AN) == 10000, "window takes (Count, optional Skip)");
    }
};

}

#endif