rx-distinct_until_changed.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_UNTIL_CHANGED_HPP)
#define RXCPP_OPERATORS_RX_DISTINCT_UNTIL_CHANGED_HPP

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

namespace rxcpp {

namespace operators {

namespace detail {

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

template<class... AN>
struct distinct_until_changed_invalid : public rxo::operator_base<distinct_until_changed_invalid_arguments<AN...>> {
    using type = observable<distinct_until_changed_invalid_arguments<AN...>, distinct_until_changed_invalid<AN...>>;
};
template<class... AN>
using distinct_until_changed_invalid_t = typename distinct_until_changed_invalid<AN...>::type;

template<class T, class BinaryPredicate>
struct distinct_until_changed
{
    typedef rxu::decay_t<T> source_value_type;
    typedef rxu::decay_t<BinaryPredicate> predicate_type;

    predicate_type pred;

    distinct_until_changed(predicate_type p)
    : pred(std::move(p))
    {
    }

    template<class Subscriber>
    struct distinct_until_changed_observer
    {
        typedef distinct_until_changed_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;
        predicate_type pred;
        mutable rxu::detail::maybe<source_value_type> remembered;

        distinct_until_changed_observer(dest_type d, predicate_type pred)
            : dest(std::move(d))
            , pred(std::move(pred))
        {
        }
        void on_next(source_value_type v) const {
            if (remembered.empty() || !pred(v, remembered.get())) {
                remembered.reset(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_type> make(dest_type d, predicate_type p) {
            return make_subscriber<value_type>(d, this_type(d, std::move(p)));
        }
    };

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

}

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

}

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

    template<class Observable,
            class BinaryPredicate,
            class SourceValue = rxu::value_type_t<Observable>,
            class Enabled = rxu::enable_if_all_true_type_t<
            is_observable<Observable>>,
            class DistinctUntilChanged = rxo::detail::distinct_until_changed<SourceValue, BinaryPredicate>>
    static auto member(Observable&& o, BinaryPredicate&& pred)
    -> decltype(o.template lift<SourceValue>(DistinctUntilChanged(std::forward<BinaryPredicate>(pred)))) {
        return  o.template lift<SourceValue>(DistinctUntilChanged(std::forward<BinaryPredicate>(pred)));
    }

    template<class... AN>
    static operators::detail::distinct_until_changed_invalid_t<AN...> member(AN...) {
        std::terminate();
        return {};
        static_assert(sizeof...(AN) == 10000, "distinct_until_changed takes (optional BinaryPredicate)");
    }
};

}

#endif