throttle.h

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/**********************************************************************
 * LeechCraft - modular cross-platform feature rich internet client.
 * Copyright (C) 2006-2014  Georg Rudoy
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 **********************************************************************/

#pragma once

#include <coroutine>
#include <chrono>
#include <QElapsedTimer>
#include <QTimer>
#include <QVector>
#include "../threadsconfig.h"

namespace LC::Util
{
    class UTIL_THREADS_API Throttle
    {
        QTimer Timer_;
        QElapsedTimer LastInvocation_;
        std::chrono::milliseconds Interval_;

        QVector<std::coroutine_handle<>> Queue_;

        int BackoffFactor_ = 0;

        struct Awaiter
        {
            Throttle& Throttle_;
            std::coroutine_handle<> Handle_ {};

            explicit Awaiter (Throttle& throttle);
            Awaiter (Awaiter&& other) noexcept;

            Awaiter (const Awaiter&) = delete;
            Awaiter& operator= (const Awaiter&) = delete;
            Awaiter& operator= (Awaiter&&) = delete;

            ~Awaiter ();

            bool await_ready () const;
            void await_suspend (std::coroutine_handle<>);
            void await_resume ();
        };
    public:
        explicit Throttle (std::chrono::milliseconds, Qt::TimerType = Qt::TimerType::CoarseTimer);

        std::chrono::milliseconds GetInterval () const;

        void Backoff ();

        Awaiter operator co_await ();
    private:
        void StartTimer (std::chrono::milliseconds);
    };

    using Throttle_ptr = std::shared_ptr<Throttle>;
}