Timed task scheduler using boost asio

timed_scheduler.hpp

//
// Created by agiu on 1/4/23.
//

#ifndef INCLUDE_TIMED_SCHEDULER_HPP
#define INCLUDE_TIMED_SCHEDULER_HPP

#include <boost/asio/io_context.hpp>
#include <boost/system/error_code.hpp>
#include <boost/asio/steady_timer.hpp>

template<typename io_context>
class scheduler : public std::enable_shared_from_this<scheduler<io_context>> {
    using boost_ec = boost::system::error_code;
    using timer_sptr = std::shared_ptr<boost::asio::steady_timer>;
    using task_completion_handler = std::function<void(const boost_ec &)>;

    io_context &_io_ctx;

    struct task {
        timer_sptr _timer;

        explicit task(const timer_sptr &timer) : _timer(timer) {}
    };

    mutable std::mutex mtx_tasks;
    std::unordered_map <uint16_t, task> _tasks;

public:
    explicit scheduler(io_context &io_ctx) : _io_ctx(io_ctx) {};

    uint16_t add_task(std::chrono::milliseconds expire_after, task_completion_handler &&cb) {
        std::lock_guard<std::mutex> g(mtx_tasks);

        const auto task_id = static_cast<uint16_t>(_tasks.size());

        auto weak_self = std::weak_ptr<scheduler>(this->shared_from_this());
        const auto timer = std::make_shared<boost::asio::steady_timer>(_io_ctx);
        timer->expires_after(expire_after);
        timer->async_wait([weak_self, timer, task_id, handler = std::forward<task_completion_handler>(cb)](
                const boost_ec &ec) {            
                handler(ec);
                
            if (auto self = weak_self.lock()) {
                std::lock_guard<std::mutex> g(self->mtx_tasks);
                self->_tasks.erase(task_id);
            }
        });
        _tasks.emplace(task_id, task{timer});

        return task_id;
    };

    void cancel_task(uint16_t task_id) {
        std::lock_guard<std::mutex> g(mtx_tasks);

        const auto find_it = _tasks.find(task_id);

        if (find_it == _tasks.end())
            return;

        const auto &task = find_it->second;
        task._timer->cancel();
    };
};

#endif //INCLUDE_TIMED_SCHEDULER_HPP