#pragma once
/////////////////////////////////////////////////////////////////////
// ThreadPool.h - Enqueue work items to run on one of a collection //
//                of threads, created at startup.                  //
//                                                                 //
// Jim Fawcett, CSE687 - Object Oriented Design, Spring 2016       //
/////////////////////////////////////////////////////////////////////
/*
* Threadpool makes copy of each work item on the heap in case it
* changes before executing.  Copy is deleted after execution.
*
* This means that work items have to be copyable.
*/
#include <functional>
#include <vector>
#include <thread>
#include <mutex>
#include <memory>
#include "../Cpp11-BlockingQueue/Cpp11-BlockingQueue.h"

class ThreadPool
{
public:
  using CallObj = std::function<void()>;

  ThreadPool(size_t n=8);
  ThreadPool(const ThreadPool&) = delete;
  ThreadPool& operator=(const ThreadPool&) = delete;

  void workItem(CallObj* pCo);
  void wait();
  std::mutex& mutex();
  ~ThreadPool();
private:
  BlockingQueue<CallObj*> Q_;
  std::vector<std::thread> threads_;
  std::mutex mtx_;    // lock shared by all threads in pool
};

inline std::mutex& ThreadPool::mutex() { return mtx_; }