scheduler.h

// Copyright (c) 2014-2026 Savoir-faire Linux Inc.
// SPDX-License-Identifier: MIT
#pragma once
 
#include "utils.h"
 
#include <functional>
#include <map>
 
namespace dht {

class Scheduler
{
public:
    struct Job
    {
        Job(std::function<void()>&& f, time_point t)
            : do_(std::move(f))
            , t_(t)
        {}
        std::function<void()> do_;
        const time_point t_;
        void cancel() { do_ = {}; }
    };

    Sp<Scheduler::Job> add(time_point t, std::function<void()>&& job_func)
    {
        auto job = std::make_shared<Job>(std::move(job_func), t);
        if (t != time_point::max())
            timers.emplace(std::move(t), job);
        return job;
    }

    void edit(Sp<Scheduler::Job>& job, time_point t)
    {
        if (not job)
            return;
        // std::function move doesn't garantee to leave the object empty.
        // Force clearing old value.
        auto task = std::move(job->do_);
        cancel(job);
        job = add(t, std::move(task));
    }
 
    bool cancel(Sp<Scheduler::Job>& job)
    {
        if (job) {
            job->cancel();
            for (auto r = timers.equal_range(job->t_); r.first != r.second; ++r.first) {
                if (r.first->second == job) {
                    timers.erase(r.first);
                    job.reset();
                    return true;
                }
            }
        }
        return false;
    }

    time_point run()
    {
        while (not timers.empty()) {
            auto timer = timers.begin();
            /*
             * Running jobs scheduled before "now" prevents run+rescheduling
             * loops before this method ends. It is garanteed by the fact that a
             * job will at least be scheduled for "now" and not before.
             */
            if (timer->first > now)
                break;
 
            auto job = std::move(timer->second);
            timers.erase(timer);
 
            if (job->do_)
                job->do_();
        }
        return getNextJobTime();
    }
 
    inline time_point getNextJobTime() const { return timers.empty() ? time_point::max() : timers.begin()->first; }

    inline const time_point& time() const { return now; }
    inline time_point syncTime() { return (now = clock::now()); }
    inline void syncTime(const time_point& n) { now = n; }
 
private:
    time_point now {clock::now()};
    std::multimap<time_point, Sp<Job>> timers {}; /* the jobs ordered by time */
};
 
} // namespace dht