///////////////////////////////////////////////////////////////////////
// MT3Q7.cpp - Thread results                                        //
//                                                                   //
// Jim Fawcett, CSE687 - Object Oriented Design Midterm, Spring 2018 //
///////////////////////////////////////////////////////////////////////

#include <thread>
#include <future>
#include <iostream>
#include <chrono>

size_t theFirstMeaningOfLife()
{
  std::cout << "\n  The meaning of life: ";
  for (size_t i = 0; i < 5; ++i)
  {
    std::this_thread::sleep_for(std::chrono::milliseconds(500));
    std::cout << "thinking ... ";
  }
  return 42;
}

void theSecondMeaningOfLife(size_t& answer)
{
  std::cout << "\n  The meaning of life: ";
  for (size_t i = 0; i < 5; ++i)
  {
    std::this_thread::sleep_for(std::chrono::milliseconds(300));
    std::cout << "thinking ... ";
  }
  answer = 42;
}

int main()
{
  std::cout << "\n  MT3Q7 - Getting a std::thread result";
  std::cout << "\n ======================================\n";

  // async with future is thread safe by design
  std::future<size_t> fut = std::async(theFirstMeaningOfLife);
  std::cout << "\n  the first meaning of life is: " << fut.get();
  std::cout << "\n";

  // for thread safety, must join before accessing ref value
  size_t mol;
  std::thread t(theSecondMeaningOfLife, std::ref(mol));
  t.join();
  std::cout << "\n  the second meaning of life is: " << mol;

  // prefer the first method
  std::cout << "\n\n";
  return 0;
}