rx-flat_map.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_FLATMAP_HPP)
#define RXCPP_OPERATORS_RX_FLATMAP_HPP

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

namespace rxcpp {

namespace operators {

namespace detail {

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

template<class... AN>
struct flat_map_invalid : public rxo::operator_base<flat_map_invalid_arguments<AN...>> {
    using type = observable<flat_map_invalid_arguments<AN...>, flat_map_invalid<AN...>>;
};
template<class... AN>
using flat_map_invalid_t = typename flat_map_invalid<AN...>::type;

template<class Observable, class CollectionSelector, class ResultSelector, class Coordination>
struct flat_map_traits {
    typedef rxu::decay_t<Observable> source_type;
    typedef rxu::decay_t<CollectionSelector> collection_selector_type;
    typedef rxu::decay_t<ResultSelector> result_selector_type;
    typedef rxu::decay_t<Coordination> coordination_type;

    typedef typename source_type::value_type source_value_type;

    struct tag_not_valid {};
    template<class CV, class CCS>
    static auto collection_check(int) -> decltype((*(CCS*)nullptr)(*(CV*)nullptr));
    template<class CV, class CCS>
    static tag_not_valid collection_check(...);

    static_assert(!std::is_same<decltype(collection_check<source_value_type, collection_selector_type>(0)), tag_not_valid>::value, "flat_map CollectionSelector must be a function with the signature observable(flat_map::source_value_type)");

    typedef rxu::decay_t<decltype((*(collection_selector_type*)nullptr)((*(source_value_type*)nullptr)))> collection_type;

    static_assert(is_observable<collection_type>::value, "flat_map CollectionSelector must return an observable");

    typedef typename collection_type::value_type collection_value_type;

    template<class CV, class CCV, class CRS>
    static auto result_check(int) -> decltype((*(CRS*)nullptr)(*(CV*)nullptr, *(CCV*)nullptr));
    template<class CV, class CCV, class CRS>
    static tag_not_valid result_check(...);

    static_assert(!std::is_same<decltype(result_check<source_value_type, collection_value_type, result_selector_type>(0)), tag_not_valid>::value, "flat_map ResultSelector must be a function with the signature flat_map::value_type(flat_map::source_value_type, flat_map::collection_value_type)");

    typedef rxu::decay_t<decltype((*(result_selector_type*)nullptr)(*(source_value_type*)nullptr, *(collection_value_type*)nullptr))> value_type;
};

template<class Observable, class CollectionSelector, class ResultSelector, class Coordination>
struct flat_map
    : public operator_base<rxu::value_type_t<flat_map_traits<Observable, CollectionSelector, ResultSelector, Coordination>>>
{
    typedef flat_map<Observable, CollectionSelector, ResultSelector, Coordination> this_type;
    typedef flat_map_traits<Observable, CollectionSelector, ResultSelector, Coordination> traits;

    typedef typename traits::source_type source_type;
    typedef typename traits::collection_selector_type collection_selector_type;
    typedef typename traits::result_selector_type result_selector_type;

    typedef typename traits::source_value_type source_value_type;
    typedef typename traits::collection_type collection_type;
    typedef typename traits::collection_value_type collection_value_type;

    typedef typename traits::coordination_type coordination_type;
    typedef typename coordination_type::coordinator_type coordinator_type;

    struct values
    {
        values(source_type o, collection_selector_type s, result_selector_type rs, coordination_type sf)
            : source(std::move(o))
            , selectCollection(std::move(s))
            , selectResult(std::move(rs))
            , coordination(std::move(sf))
        {
        }
        source_type source;
        collection_selector_type selectCollection;
        result_selector_type selectResult;
        coordination_type coordination;
    };
    values initial;

    flat_map(source_type o, collection_selector_type s, result_selector_type rs, coordination_type sf)
        : initial(std::move(o), std::move(s), std::move(rs), std::move(sf))
    {
    }

    template<class Subscriber>
    void on_subscribe(Subscriber scbr) const {
        static_assert(is_subscriber<Subscriber>::value, "subscribe must be passed a subscriber");

        typedef Subscriber output_type;

        struct state_type
            : public std::enable_shared_from_this<state_type>
            , public values
        {
            state_type(values i, coordinator_type coor, output_type oarg)
                : values(std::move(i))
                , pendingCompletions(0)
                , coordinator(std::move(coor))
                , out(std::move(oarg))
            {
            }
            // on_completed on the output must wait until all the
            // subscriptions have received on_completed
            int pendingCompletions;
            coordinator_type coordinator;
            output_type out;
        };

        auto coordinator = initial.coordination.create_coordinator(scbr.get_subscription());

        // take a copy of the values for each subscription
        auto state = std::make_shared<state_type>(initial, std::move(coordinator), std::move(scbr));

        composite_subscription outercs;

        // when the out observer is unsubscribed all the
        // inner subscriptions are unsubscribed as well
        state->out.add(outercs);

        auto source = on_exception(
            [&](){return state->coordinator.in(state->source);},
            state->out);
        if (source.empty()) {
            return;
        }

        ++state->pendingCompletions;
        // this subscribe does not share the observer subscription
        // so that when it is unsubscribed the observer can be called
        // until the inner subscriptions have finished
        auto sink = make_subscriber<source_value_type>(
            state->out,
            outercs,
        // on_next
            [state](source_value_type st) {

                composite_subscription innercs;

                // when the out observer is unsubscribed all the
                // inner subscriptions are unsubscribed as well
                auto innercstoken = state->out.add(innercs);

                innercs.add(make_subscription([state, innercstoken](){
                    state->out.remove(innercstoken);
                }));

                auto selectedCollection = state->selectCollection(st);
                auto selectedSource = state->coordinator.in(selectedCollection);

                ++state->pendingCompletions;
                // this subscribe does not share the source subscription
                // so that when it is unsubscribed the source will continue
                auto sinkInner = make_subscriber<collection_value_type>(
                    state->out,
                    innercs,
                // on_next
                    [state, st](collection_value_type ct) {
                        auto selectedResult = state->selectResult(st, std::move(ct));
                        state->out.on_next(std::move(selectedResult));
                    },
                // on_error
                    [state](std::exception_ptr e) {
                        state->out.on_error(e);
                    },
                //on_completed
                    [state](){
                        if (--state->pendingCompletions == 0) {
                            state->out.on_completed();
                        }
                    }
                );

                auto selectedSinkInner = state->coordinator.out(sinkInner);
                selectedSource.subscribe(std::move(selectedSinkInner));
            },
        // on_error
            [state](std::exception_ptr e) {
                state->out.on_error(e);
            },
        // on_completed
            [state]() {
                if (--state->pendingCompletions == 0) {
                    state->out.on_completed();
                }
            }
        );

        auto selectedSink = on_exception(
            [&](){return state->coordinator.out(sink);},
            state->out);
        if (selectedSink.empty()) {
            return;
        }

        source->subscribe(std::move(selectedSink.get()));

    }
};

}

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

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

}

template<>
struct member_overload<flat_map_tag>
{
    template<class Observable, class CollectionSelector,
        class CollectionSelectorType = rxu::decay_t<CollectionSelector>,
        class SourceValue = rxu::value_type_t<Observable>,
        class CollectionType = rxu::result_of_t<CollectionSelectorType(SourceValue)>,
        class ResultSelectorType = rxu::detail::take_at<1>,
        class Enabled = rxu::enable_if_all_true_type_t<
            all_observables<Observable, CollectionType>>,
        class FlatMap = rxo::detail::flat_map<rxu::decay_t<Observable>, rxu::decay_t<CollectionSelector>, ResultSelectorType, identity_one_worker>,
        class CollectionValueType = rxu::value_type_t<CollectionType>,
        class Value = rxu::result_of_t<ResultSelectorType(SourceValue, CollectionValueType)>,
        class Result = observable<Value, FlatMap>
    >
    static Result member(Observable&& o, CollectionSelector&& s) {
        return Result(FlatMap(std::forward<Observable>(o), std::forward<CollectionSelector>(s), ResultSelectorType(), identity_current_thread()));
    }

    template<class Observable, class CollectionSelector, class Coordination,
        class CollectionSelectorType = rxu::decay_t<CollectionSelector>,
        class SourceValue = rxu::value_type_t<Observable>,
        class CollectionType = rxu::result_of_t<CollectionSelectorType(SourceValue)>,
        class ResultSelectorType = rxu::detail::take_at<1>,
        class Enabled = rxu::enable_if_all_true_type_t<
            all_observables<Observable, CollectionType>,
            is_coordination<Coordination>>,
        class FlatMap = rxo::detail::flat_map<rxu::decay_t<Observable>, rxu::decay_t<CollectionSelector>, ResultSelectorType, rxu::decay_t<Coordination>>,
        class CollectionValueType = rxu::value_type_t<CollectionType>,
        class Value = rxu::result_of_t<ResultSelectorType(SourceValue, CollectionValueType)>,
        class Result = observable<Value, FlatMap>
    >
    static Result member(Observable&& o, CollectionSelector&& s, Coordination&& cn) {
        return Result(FlatMap(std::forward<Observable>(o), std::forward<CollectionSelector>(s), ResultSelectorType(), std::forward<Coordination>(cn)));
    }

    template<class Observable, class CollectionSelector, class ResultSelector,
        class IsCoordination = is_coordination<ResultSelector>,
        class CollectionSelectorType = rxu::decay_t<CollectionSelector>,
        class SourceValue = rxu::value_type_t<Observable>,
        class CollectionType = rxu::result_of_t<CollectionSelectorType(SourceValue)>,
        class Enabled = rxu::enable_if_all_true_type_t<
            all_observables<Observable, CollectionType>,
            rxu::negation<IsCoordination>>,
        class FlatMap = rxo::detail::flat_map<rxu::decay_t<Observable>, rxu::decay_t<CollectionSelector>, rxu::decay_t<ResultSelector>, identity_one_worker>,
        class CollectionValueType = rxu::value_type_t<CollectionType>,
        class ResultSelectorType = rxu::decay_t<ResultSelector>,
        class Value = rxu::result_of_t<ResultSelectorType(SourceValue, CollectionValueType)>,
        class Result = observable<Value, FlatMap>
    >
    static Result member(Observable&& o, CollectionSelector&& s, ResultSelector&& rs) {
        return Result(FlatMap(std::forward<Observable>(o), std::forward<CollectionSelector>(s), std::forward<ResultSelector>(rs), identity_current_thread()));
    }

    template<class Observable, class CollectionSelector, class ResultSelector, class Coordination,
        class CollectionSelectorType = rxu::decay_t<CollectionSelector>,
        class SourceValue = rxu::value_type_t<Observable>,
        class CollectionType = rxu::result_of_t<CollectionSelectorType(SourceValue)>,
        class Enabled = rxu::enable_if_all_true_type_t<
            all_observables<Observable, CollectionType>,
            is_coordination<Coordination>>,
        class FlatMap = rxo::detail::flat_map<rxu::decay_t<Observable>, rxu::decay_t<CollectionSelector>, rxu::decay_t<ResultSelector>, rxu::decay_t<Coordination>>,
        class CollectionValueType = rxu::value_type_t<CollectionType>,
        class ResultSelectorType = rxu::decay_t<ResultSelector>,
        class Value = rxu::result_of_t<ResultSelectorType(SourceValue, CollectionValueType)>,
        class Result = observable<Value, FlatMap>
    >
    static Result member(Observable&& o, CollectionSelector&& s, ResultSelector&& rs, Coordination&& cn) {
        return Result(FlatMap(std::forward<Observable>(o), std::forward<CollectionSelector>(s), std::forward<ResultSelector>(rs), std::forward<Coordination>(cn)));
    }

    template<class... AN>
    static operators::detail::flat_map_invalid_t<AN...> member(AN...) {
        std::terminate();
        return {};
        static_assert(sizeof...(AN) == 10000, "flat_map takes (CollectionSelector, optional ResultSelector, optional Coordination)");
    }
};

}

#endif