AScheduler.h

/*
 * AUI Framework - Declarative UI toolkit for modern C++20
 * Copyright (C) 2020-2024 Alex2772 and Contributors
 *
 * SPDX-License-Identifier: MPL-2.0
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
 
#pragma once
 
#include <chrono>
#include <functional>
#include <list>
#include "AUI/Reflect/AEnumerate.h"
#include <AUI/Thread/AMutex.h>
#include <AUI/Thread/AConditionVariable.h>
#include <AUI/Thread/IEventLoop.h>
#include <AUI/Util/ABitField.h>
 

AUI_ENUM_FLAG(ASchedulerIteration) {
    NONE = 0,

    DONT_BLOCK_INFINITELY = 0b1,

    DONT_BLOCK_TIMED = 0b10,

    DONT_BLOCK = DONT_BLOCK_INFINITELY | DONT_BLOCK_TIMED,
};

class API_AUI_CORE AScheduler: public IEventLoop {
private:
    using SchedulerDuration = std::chrono::microseconds;
 
    struct Timer {
        std::chrono::milliseconds timeout;
        std::chrono::high_resolution_clock::time_point nextExecution;
        std::function<void()> callback;
    };
 
    struct Task {
        std::chrono::high_resolution_clock::time_point executionTime;
        std::function<void()> callback;
        _weak<Timer> timer;
    };
public:
    using TimerHandle = _weak<Timer>;
 
    AScheduler();

    bool iteration(ABitField<ASchedulerIteration> flag = ASchedulerIteration::NONE);
 
    void notifyProcessMessages() override;
    void loop() override;
 
    template<typename Duration>
    void enqueue(Duration timeout, std::function<void()> callback) {
        std::unique_lock lock(mSync);
        Task asTask = {
                std::chrono::duration_cast<SchedulerDuration>(timeout) + currentTime(),
                std::move(callback)
        };
        enqueueTask(std::move(asTask));
        mCV.notify_all();
    }

    template<typename Duration>
    TimerHandle timer(Duration timeout, std::function<void()> callback) {
        auto millis = std::chrono::duration_cast<std::chrono::milliseconds>(timeout);
        Timer t = {
                millis,
                millis + currentTime(),
                std::move(callback)
        };
        auto asTimer = _new<Timer>(std::move(t));
 
        std::unique_lock lock(mSync);
        mTimers.push_back(asTimer);
        enqueueTimer(asTimer);
        return asTimer;
    }
 
 
    void removeTimer(const TimerHandle& t);
 
    [[nodiscard]]
    bool emptyTasks() const noexcept {
        return mTasks.empty();
    }
 
    void stop() {
        mIsRunning = false;
        mCV.notify_all();
    }
 
 
private:
    AMutex mSync;
    AConditionVariable mCV;
    bool mIsRunning = false;
 
    std::list<Task> mTasks;
    std::list<_<Timer>> mTimers;
 
    static std::chrono::high_resolution_clock::time_point currentTime() noexcept {
        return std::chrono::high_resolution_clock::now();
    }
 
    void enqueueTimer(const _<Timer>& timer) {
        Task t = {
                timer->nextExecution,
                [this, timer]() {
                    timer->callback();
                    std::unique_lock lock(mSync);
                    enqueueTimer(timer);
                },
                timer
        };
        timer->nextExecution += timer->timeout;
        enqueueTask(std::move(t));
    }
 
 
    void enqueueTask(Task&& asTask) {
        auto whereToInsert = std::find_if(mTasks.begin(), mTasks.end(), [&](const Task& rhs) {
            return asTask.executionTime < rhs.executionTime;
        });
 
        mTasks.insert(whereToInsert, std::move(asTask));
        mCV.notify_all();
    }
 
};