#include <iostream>
#include <thread>
#include <mutex>
#include <chrono>

class Loop
{
    std::thread loopThread;
    std::chrono::milliseconds lastBeatTime; 
    unsigned short bpm;
    std::mutex bpmLock;
    bool stopNext;

public:
    bool enabled;

    Loop()
        : bpm(60), stopNext(false), enabled(false), loopThread(&Loop::loop, this)
    {
    }

    ~Loop()
    {
        stopNext = true;
        loopThread.join();
    }

    void setBpm(unsigned short b)
    {
        bpmLock.lock();
        bpm = b;
        bpmLock.unlock();
    }

    unsigned short getBpm()
    {
        bpmLock.lock();
        unsigned short r = bpm;
        bpmLock.unlock();
        return r;
    }

    std::chrono::milliseconds getBeatDuration()
    {
        return std::chrono::milliseconds(
                (long long)((double)60 * 1000 / bpm)
                );
    }

    void start()
    {
        enabled = true;
    }

    void stop()
    {
        enabled = false;
    }

private:
    std::chrono::milliseconds getMillisecondsSinceEpoch()
    {
        std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
        std::chrono::system_clock::duration duration = now.time_since_epoch();
        return std::chrono::duration_cast<std::chrono::milliseconds>(duration);
    }

    void beat() 
    {
        std::cout << "\a" << lastBeatTime.count() << std::endl;
    }

    void loop()
    {
        while(!stopNext) {
            if((getMillisecondsSinceEpoch() - lastBeatTime) >= getBeatDuration()) {
                lastBeatTime = getMillisecondsSinceEpoch();
                beat();
            }
        }
    }
};