observed_value_combinator.hpp

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#pragma once
 
#include <nui/event_system/event_context.hpp>
#include <nui/event_system/observed_value.hpp>
#include <nui/utility/tuple_for_each.hpp>
#include <nui/utility/overloaded.hpp>
#include <nui/concepts.hpp>
 
#include <tuple>
 
namespace Nui
{
    template <typename... ObservedValues>
    class ObservedValueCombinatorBase
    {
      public:
        explicit constexpr ObservedValueCombinatorBase(
            Detail::ObservedAddReference_t<ObservedValues>&&... observedValues)
            : observedValues_{std::forward<Detail::ObservedAddReference_t<ObservedValues>>(observedValues)...}
        {}
        explicit constexpr ObservedValueCombinatorBase(
            std::tuple<Detail::ObservedAddReference_t<ObservedValues>...> observedValues)
            : observedValues_{std::move(observedValues)}
        {}
 
        constexpr void attachEvent(auto eventId) const
        {
            tupleForEach(
                observedValues_,
                Nui::overloaded{
                    [eventId](IsObserved auto const& observed) {
                        observed.attachEvent(eventId);
                    },
                    [eventId](IsWeakObserved auto const& observed) {
                        if (auto shared = observed.lock(); shared)
                            shared->attachEvent(eventId);
                    },
                });
        }
 
        constexpr void attachOneshotEvent(auto eventId) const
        {
            tupleForEach(
                observedValues_,
                Nui::overloaded{
                    [eventId](IsObserved auto const& observed) {
                        observed.attachOneshotEvent(eventId);
                    },
                    [eventId](IsWeakObserved auto const& observed) {
                        if (auto shared = observed.lock(); shared)
                            shared->attachOneshotEvent(eventId);
                    },
                });
        }
 
        constexpr void detachEvent(auto eventId) const
        {
            tupleForEach(
                observedValues_,
                Nui::overloaded{
                    [eventId](IsObserved auto const& observed) {
                        observed.detachEvent(eventId);
                    },
                    [eventId](IsWeakObserved auto const& observed) {
                        if (auto shared = observed.lock(); shared)
                            shared->detachEvent(eventId);
                    },
                });
        }
 
        std::tuple<Detail::ObservedAddReference_t<ObservedValues>...> const& observedValues() &
        {
            return observedValues_;
        }
 
        std::tuple<Detail::ObservedAddReference_t<ObservedValues>...>&& observedValues() &&
        {
            return std::move(
                const_cast<std::tuple<Detail::ObservedAddReference_t<ObservedValues>...>&>(observedValues_));
        }
 
        bool isAnyExpired() const
        {
            const auto isExpired = Nui::overloaded{
                [](IsObserved auto const&) {
                    return false;
                },
                [](IsWeakObserved auto const& observed) {
                    return observed.expired();
                },
            };
 
            return std::apply(
                [isExpired](auto const&... observed) {
                    return (isExpired(observed) || ...);
                },
                observedValues_);
        }
 
      protected:
        const std::tuple<Detail::ObservedAddReference_t<ObservedValues>...> observedValues_;
    };
 
    template <typename... ObservedValues>
    class ObservedValueCombinator;
 
    template <typename RendererType, typename... ObservedValues>
    class ObservedValueCombinatorWithGenerator : public ObservedValueCombinatorBase<ObservedValues...>
    {
      public:
        constexpr ObservedValueCombinatorWithGenerator(
            std::tuple<Detail::ObservedAddReference_t<ObservedValues>...> observedValues,
            RendererType generator)
            : ObservedValueCombinatorBase<ObservedValues...>{std::move(observedValues)}
            , generator_{std::move(generator)}
        {}
 
        ObservedValueCombinator<ObservedValues...> split() &&
        {
            return ObservedValueCombinator<ObservedValues...>{std::move(this->observedValues_)};
        }
 
        constexpr auto value() const
        {
            return generator_();
        }
 
        RendererType generator() const&
        {
            return generator_;
        }
        RendererType generator() &&
        {
            return std::move(generator_);
        }
 
      protected:
        const RendererType generator_;
    };
 
    template <typename RendererType, typename... ObservedValues>
    class ObservedValueCombinatorWithPropertyGenerator
        : public ObservedValueCombinatorWithGenerator<RendererType, ObservedValues...>
    {
      public:
        using ObservedValueCombinatorWithGenerator<RendererType, ObservedValues...>::
            ObservedValueCombinatorWithGenerator;
        ObservedValueCombinatorWithPropertyGenerator(
            ObservedValueCombinatorWithGenerator<RendererType, ObservedValues...>&& other)
            : ObservedValueCombinatorWithGenerator<RendererType, ObservedValues...>{std::move(other)}
        {}
 
        using ObservedValueCombinatorWithGenerator<RendererType, ObservedValues...>::split;
        using ObservedValueCombinatorWithGenerator<RendererType, ObservedValues...>::value;
        using ObservedValueCombinatorWithGenerator<RendererType, ObservedValues...>::generator;
    };
 
    template <typename... ObservedValues>
    class ObservedValueCombinator : public ObservedValueCombinatorBase<ObservedValues...>
    {
      public:
        using ObservedValueCombinatorBase<ObservedValues...>::ObservedValueCombinatorBase;
        using ObservedValueCombinatorBase<ObservedValues...>::observedValues_;
 
        template <typename RendererType>
        requires std::invocable<RendererType>
        constexpr ObservedValueCombinatorWithGenerator<RendererType, ObservedValues...>
        generate(RendererType&& generator)
        {
            return ObservedValueCombinatorWithGenerator<RendererType, ObservedValues...>{
                observedValues_, std::forward<RendererType>(generator)};
        }
 
        template <typename RendererType>
        requires std::invocable<RendererType>
        constexpr ObservedValueCombinatorWithPropertyGenerator<RendererType, ObservedValues...>
        generateProperty(RendererType&& generator)
        {
            return ObservedValueCombinatorWithPropertyGenerator<RendererType, ObservedValues...>{
                observedValues_, std::forward<RendererType>(generator)};
        }
    };
    template <typename... ObservedValues>
    ObservedValueCombinator(ObservedValues&&...)
        -> ObservedValueCombinator<std::decay_t<Detail::ObservedAddReference_t<ObservedValues>>...>;
    template <typename... ObservedValues>
    ObservedValueCombinator(std::tuple<Detail::ObservedAddReference_t<ObservedValues>...>)
        -> ObservedValueCombinator<std::decay_t<Detail::ObservedAddReference_t<ObservedValues>>...>;
 
    template <typename... ObservedValues>
    requires(IsObservedLike<ObservedValues> && ...)
    ObservedValueCombinator<std::decay_t<Detail::ObservedAddReference_t<ObservedValues>>...>
    observe(ObservedValues&&... observedValues)
    {
        return ObservedValueCombinator<std::decay_t<Detail::ObservedAddReference_t<ObservedValues>>...>{
            std::forward<Detail::ObservedAddReference_t<ObservedValues>>(observedValues)...};
    }
}