//********************************************************
// The following code example is taken from the book
//  C++20 - The Complete Guide
//  by Nicolai M. Josuttis (www.josuttis.com)
//  http://www.cppstd20.com
//
// The code is licensed under a
//  Creative Commons Attribution 4.0 International License
//  http://creativecommons.org/licenses/by/4.0/
//********************************************************


#include <iostream>
#include <chrono>
#include <thread>
#include <semaphore>
using namespace std::literals;  // for duration literals

int main()
{
  int sharedData;
  std::binary_semaphore dataReady{0};  // signal there is data to process 
  std::binary_semaphore dataDone{0};   // signal processing is done

  // start threads to read and process values by value:
  std::jthread process{[&] (std::stop_token st) {
                         while(!st.stop_requested()) {
                           // wait until the next value is ready:
                           // - timeout after 1s to check stop_token
                           if (dataReady.try_acquire_for(1s)) {
                             int data = sharedData;

                             // process it:
                             std::cout << "[process] read " << data << std::endl;
                             std::this_thread::sleep_for(data * 0.5s);
                             std::cout << "[process]      done" << std::endl;

                             // signal processing done:
                             dataDone.release();
                           }
                           else {
                             std::cout << "[process] timeout" << std::endl;
                           }
                         }
                       }};

  // generate a couple of values:
  for (int i = 0; i < 10; ++i) {
    // store next value:
    std::cout << "[main] store " << i << std::endl;
    sharedData = i;

    // signal to start processing:
    dataReady.release();

    // wait until processing is done:
    dataDone.acquire();
    std::cout << "[main] processing done\n" << std::endl;
  }
  // end of loop signals stop
}