workerthreadbase.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 <functional>
#include <atomic>
#include <QThread>
#include <QMutex>
#include <QMutexLocker>
#include <QFutureInterface>
#include <QFuture>
#include <QList>
#include "futures.h"
#include "threadsconfig.h"

namespace LC::Util
{
    class UTIL_THREADS_API WorkerThreadBase : public QThread
    {
        Q_OBJECT

        std::atomic_bool IsPaused_ { false };

        QMutex FunctionsMutex_;
        QList<std::function<void ()>> Functions_;
    public:
        using QThread::QThread;

        void SetPaused (bool);

        template<typename F>
        QFuture<std::invoke_result_t<F>> ScheduleImpl (F func)
        {
            QFutureInterface<std::invoke_result_t<F>> iface;
            iface.reportStarted ();

            auto reporting = [func, iface] () mutable
            {
                ReportFutureResult (iface, func);
            };

            {
                QMutexLocker locker { &FunctionsMutex_ };
                Functions_ << reporting;
            }

            emit rotateFuncs ();

            return iface.future ();
        }

        template<typename F, typename... Args>
        QFuture<std::invoke_result_t<F, Args...>> ScheduleImpl (F f, Args&&... args)
        {
            return ScheduleImpl ([f, args...] () mutable { return std::invoke (f, args...); });
        }

        virtual size_t GetQueueSize ();
    protected:
        void run () final;

        virtual void Initialize () = 0;
        virtual void Cleanup () = 0;
    private:
        void RotateFuncs ();
    signals:
        void rotateFuncs ();
    };

    namespace detail
    {
        template<typename WorkerType>
        struct InitializerBase
        {
            virtual std::unique_ptr<WorkerType> Initialize () = 0;

            virtual ~InitializerBase () = default;
        };

        template<typename WorkerType, typename... Args>
        struct Initializer final : InitializerBase<WorkerType>
        {
            std::tuple<Args...> Args_;

            Initializer (std::tuple<Args...>&& tuple)
            : Args_ { std::move (tuple) }
            {
            }

            std::unique_ptr<WorkerType> Initialize () override
            {
                return std::apply ([] (auto&&... args) { return std::make_unique<WorkerType> (std::forward<Args> (args)...); }, Args_);
            }
        };

        template<typename WorkerType>
        struct Initializer<WorkerType> final : InitializerBase<WorkerType>
        {
            std::unique_ptr<WorkerType> Initialize () override
            {
                return std::make_unique<WorkerType> ();
            }
        };
    }

    template<typename WorkerType>
    class WorkerThread : public WorkerThreadBase
    {
        unsigned long QuitWait_ = 2000;
    protected:
        using W = WorkerType;

        std::unique_ptr<WorkerType> Worker_;

        std::unique_ptr<detail::InitializerBase<WorkerType>> Initializer_;
    public:
        WorkerThread (QObject *parent = nullptr)
        : WorkerThreadBase { parent }
        , Initializer_ { std::make_unique<detail::Initializer<WorkerType>> () }
        {
        }

        template<typename... Args>
        WorkerThread (QObject *parent, const Args&... args)
        : WorkerThreadBase { parent }
        , Initializer_ { std::make_unique<detail::Initializer<WorkerType, std::decay_t<Args>...>> (std::tuple<std::decay_t<Args>...> { args... }) }
        {
        }

        template<
                typename Head,
                typename... Rest,
                typename = std::enable_if_t<
                        !std::is_base_of<QObject, std::remove_pointer_t<std::decay_t<Head>>>::value
                    >
            >
        WorkerThread (const Head& head, const Rest&... rest)
        : WorkerThread { static_cast<QObject*> (nullptr), head, rest... }
        {
        }

        ~WorkerThread ()
        {
            quit ();
            wait (QuitWait_);

            if (isRunning ())
                qWarning () << Q_FUNC_INFO
                        << "thread is still running";
        }

        void SetQuitWait (unsigned long wait)
        {
            QuitWait_ = wait;
        }

        using WorkerThreadBase::ScheduleImpl;

        template<typename F, typename... Args>
        QFuture<std::invoke_result_t<F, WorkerType*, Args...>> ScheduleImpl (F f, Args&&... args)
        {
            const auto fWrapped = [f, this] (auto... args) mutable { return std::invoke (f, Worker_.get (), args...); };
            return WorkerThreadBase::ScheduleImpl (fWrapped, std::forward<Args> (args)...);
        }
    protected:
        void Initialize () override
        {
            Worker_ = Initializer_->Initialize ();

            Initializer_.reset ();
        }

        void Cleanup () override
        {
            Worker_.reset ();
        }
    };
}