rx-filter.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_FILTER_HPP)
#define RXCPP_OPERATORS_RX_FILTER_HPP

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

namespace rxcpp {

namespace operators {

namespace detail {

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

template<class... AN>
struct filter_invalid : public rxo::operator_base<filter_invalid_arguments<AN...>> {
    using type = observable<filter_invalid_arguments<AN...>, filter_invalid<AN...>>;
};
template<class... AN>
using filter_invalid_t = typename filter_invalid<AN...>::type;

template<class T, class Predicate>
struct filter
{
    typedef rxu::decay_t<T> source_value_type;
    typedef rxu::decay_t<Predicate> test_type;
    test_type test;

    filter(test_type t)
        : test(std::move(t))
    {
    }

    template<class Subscriber>
    struct filter_observer
    {
        typedef filter_observer<Subscriber> this_type;
        typedef source_value_type value_type;
        typedef rxu::decay_t<Subscriber> dest_type;
        typedef observer<value_type, this_type> observer_type;
        dest_type dest;
        mutable test_type test;

        filter_observer(dest_type d, test_type t)
            : dest(std::move(d))
            , test(std::move(t))
        {
        }

        template <class Value>
        void on_next(Value&& v) const {
            auto filtered = on_exception([&](){
                    return !this->test(rxu::as_const(v));
                },
                dest);
            if (filtered.empty()) {
                return;
            }
            if (!filtered.get()) {
                dest.on_next(std::forward<Value>(v));
            }
        }
        void on_error(std::exception_ptr e) const {
            dest.on_error(e);
        }
        void on_completed() const {
            dest.on_completed();
        }

        static subscriber<value_type, observer_type> make(dest_type d, test_type t) {
            return make_subscriber<value_type>(d, this_type(d, std::move(t)));
        }
    };

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

}

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

}

template<>
struct member_overload<filter_tag>
{
    template<class Observable, class Predicate,
        class SourceValue = rxu::value_type_t<Observable>,
        class Filter = rxo::detail::filter<SourceValue, rxu::decay_t<Predicate>>>
    static auto member(Observable&& o, Predicate&& p)
        -> decltype(o.template lift<SourceValue>(Filter(std::forward<Predicate>(p)))) {
        return      o.template lift<SourceValue>(Filter(std::forward<Predicate>(p)));
    }

    template<class... AN>
    static operators::detail::filter_invalid_t<AN...> member(const AN&...) {
        std::terminate();
        return {};
        static_assert(sizeof...(AN) == 10000, "filter takes (Predicate)");
    }
};

}

#endif