//----------------------------------------------------
// mqmutex.cc: mutex using message queues
//----------------------------------------------------

#include "check.h"

#include <atomic>
#include <fcntl.h>
#include <iostream>
#include <latch>
#include <mqueue.h>
#include <random>
#include <string>
#include <thread>

//----------------------------------------------------

using namespace std::literals;

//----------------------------------------------------

const size_t N = 32;
std::latch latch(N);
std::atomic<bool> stop = false;

//----------------------------------------------------

namespace mq
{
    class mutex
    {
    public:
        mutex()
        {
            std::string path = "/" + std::to_string(std::random_device{}());
            mq_attr attr = {0, 1, 1, 0};
            id = check(
                mq_open(path.c_str(), O_CREAT | O_EXCL | O_RDWR, 0666, &attr));
            unlock();
        }
        ~mutex() { check(mq_close(id)); }
        void lock() { check(mq_receive(id, &msg, 1, 0)); }
        void unlock() { check(mq_send(id, &msg, 1, 0)); }

    private:
        mqd_t id;
        char msg = '\0';
    };
} // namespace mq

mq::mutex m;

//----------------------------------------------------

void seccion_critica()
{
    std::cout << "[" << std::this_thread::get_id() << "]: ";
    for (size_t i = 0; i < 10; ++i)
        std::cout << i;
    std::cout << '\n';
}

//----------------------------------------------------

void hebra()
{
    latch.arrive_and_wait();
    while (!stop)
    {
        std::lock_guard<mq::mutex> l(m);
        if (!stop)
            seccion_critica();
    }
}

//----------------------------------------------------

int main()
{
    std::jthread threads[N];

    for (auto &i: threads)
        i = std::jthread(hebra);

    std::this_thread::sleep_for(75ms);
    stop = true;
}

//----------------------------------------------------