#include <chrono>
#include <cstdlib>
#include <iostream>
#include <string_view>
#include <system_error>
#include <thread>
#include <vector>
#include <charconv>
#include <random>

int main( int argc, char ** argv )
{
  int numThreads = {};
  if ( argc < 2 )
  {
    numThreads = 5;
  }
  else
  {
    std::string_view numThreadArg( argv[ 1 ] );
    if ( auto [ p, ec ] = std::from_chars( numThreadArg.begin(),
                                           numThreadArg.end(),
                                           numThreads );
         ec != std::errc() )
    {
      std::cerr << "Usage " << argv[ 0 ] << " <number of threads>\n";
      return 2;
    }
  }

  std::cout << "Creating " << numThreads << " threads" << '\n';

  std::vector<std::thread> threads{};
  threads.reserve( numThreads );

  auto eng = std::default_random_engine() ;
  auto dist = std::uniform_int_distribution<int>( 250, 1000 );

  for ( int i = 0; i < numThreads; ++i )
  {
    using namespace std::chrono_literals;
    threads.emplace_back( [&,tnum=i]() {
      std::cout << "Started thread " << tnum << '\n';
      std::this_thread::sleep_for(
        5s + std::chrono::milliseconds( dist( eng ) ) );
      std::cout << "Completed thread " << tnum << '\n';
    });
  }


  for ( int i = 0; i < numThreads; ++i )
  {
    threads[ i ].join();
  }

  return 0;
}