rx-distinct.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_DISTINCT_HPP)
#define RXCPP_OPERATORS_RX_DISTINCT_HPP

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

namespace rxcpp {

namespace operators {

namespace detail {

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

template<class... AN>
struct distinct_invalid : public rxo::operator_base<distinct_invalid_arguments<AN...>> {
    using type = observable<distinct_invalid_arguments<AN...>, distinct_invalid<AN...>>;
};
template<class... AN>
using distinct_invalid_t = typename distinct_invalid<AN...>::type;

template<class T>
struct distinct
{
    typedef rxu::decay_t<T> source_value_type;

    template<class Subscriber>
    struct distinct_observer
    {
        typedef distinct_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 std::unordered_set<source_value_type, rxcpp::filtered_hash<source_value_type>> remembered;

        distinct_observer(dest_type d)
                : dest(d)
        {
        }
        void on_next(source_value_type v) const {
            if (remembered.empty() || remembered.count(v) == 0) {
                remembered.insert(v);
                dest.on_next(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<value_type, this_type>> make(dest_type d) {
            return make_subscriber<value_type>(d, this_type(d));
        }
    };

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

}

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

}

template<>
struct member_overload<distinct_tag>
{
    template<class Observable,
            class SourceValue = rxu::value_type_t<Observable>,
            class Enabled = rxu::enable_if_all_true_type_t<
                is_observable<Observable>,
                is_hashable<SourceValue>>,
            class Distinct = rxo::detail::distinct<SourceValue>>
    static auto member(Observable&& o)
    -> decltype(o.template lift<SourceValue>(Distinct())) {
        return  o.template lift<SourceValue>(Distinct());
    }

    template<class... AN>
    static operators::detail::distinct_invalid_t<AN...> member(AN...) {
        std::terminate();
        return {};
        static_assert(sizeof...(AN) == 10000, "distinct takes no arguments");
    }
};

}

#endif