#pragma once
#ifndef THREAD_POOL_H
#define THREAD_POOL_H

#include <vector>
#include <queue>
#include <thread>
#include <atomic>
#include <condition_variable>
#include <future>
#include <functional>
#include <stdexcept>

namespace std
{
#define MAX_THREAD_NUM 256

//线程池,可以提交变参函数或拉姆达表达式的匿名函数执行,可以获取执行返回值
//不支持类成员函数, 支持类静态成员函数或全局函数,Opteron()函数等
class threadpool
{
  using Task = std::function<void()>;
  // 线程池
  std::vector<std::thread> pool;
  // 任务队列
  std::queue<Task> tasks;
  // 同步
  std::mutex m_lock;
  // 条件阻塞
  std::condition_variable cv_task;
  // 是否关闭提交
  std::atomic<bool> stoped;
  //空闲线程数量
  std::atomic<int> idlThrNum;

public:
  inline threadpool(unsigned short size = 4) :stoped{ false }
  {
    idlThrNum = size < 1 ? 1 : size;
    for (size = 0; size < idlThrNum; ++size)
    {  //初始化线程数量
      pool.emplace_back(
        [this]
        { // 工作线程函数
          while(!this->stoped)
          {
            std::function<void()> task;
            {  // 获取一个待执行的 task
              std::unique_lock<std::mutex> lock{ this->m_lock };// unique_lock 相比 lock_guard 的好处是：可以随时 unlock() 和 lock()
              this->cv_task.wait(lock,
                [this] {
                  return this->stoped.load() || !this->tasks.empty();
                }
              ); // wait 直到有 task
              if (this->stoped && this->tasks.empty())
                return;
              task = std::move(this->tasks.front()); // 取一个 task
              this->tasks.pop();
            }
            idlThrNum--;
            task();
            idlThrNum++;
          }
        }
      );
    }
  }
  inline ~threadpool()
  {
    stoped.store(true);
    cv_task.notify_all(); // 唤醒所有线程执行
    for (std::thread& thread : pool) {
      //thread.detach(); // 让线程“自生自灭”
      if(thread.joinable())
        thread.join(); // 等待任务结束， 前提：线程一定会执行完
    }
  }

public:
  // 提交一个任务
  // 调用.get()获取返回值会等待任务执行完,获取返回值
  // 有两种方法可以实现调用类成员，
  // 一种是使用  bind： .commit(std::bind(&Dog::sayHello, &dog));
  // 一种是用 mem_fn： .commit(std::mem_fn(&Dog::sayHello), &dog)
  template<class F, class... Args>
  auto commit(F&& f, Args&&... args) ->std::future<decltype(f(args...))>
  {
    if (stoped.load())  // stop == true ??
      throw std::runtime_error("commit on ThreadPool is stopped.");

    using RetType = decltype(f(args...)); // typename std::result_of<F(Args...)>::type, 函数 f 的返回值类型
    auto task = std::make_shared<std::packaged_task<RetType()> >(
      std::bind(std::forward<F>(f), std::forward<Args>(args)...)
      );  // wtf !
    std::future<RetType> future = task->get_future();
    {  // 添加任务到队列
      std::lock_guard<std::mutex> lock{ m_lock };//对当前块的语句加锁 lock_guard 是 mutex 的 stack 封装类，构造的时候 lock()，析构的时候 unlock()
      tasks.emplace(
        [task]()
        { // push(Task{...})
          (*task)();
        }
      );
    }
    cv_task.notify_one(); // 唤醒一个线程执行

    return future;
  }

  //空闲线程数量
  int idlCount() { return idlThrNum; }

};

}

#endif

#include "threadpool.h"
#include <iostream>

void fun1(int slp)
{
  printf(" hello, fun1 ! %d\n" ,std::this_thread::get_id());
  if (slp>0) {
    printf(" ======= fun1 sleep %d ========= %d\n",slp, std::this_thread::get_id());
    std::this_thread::sleep_for(std::chrono::milliseconds(slp));
  }
}

struct gfun {
  int operator()(int n) {
    printf("%d hello, gfun ! %d\n" ,n, std::this_thread::get_id() );
    return 42;
  }
};

class A { 
public:
  static int Afun(int n = 0) {  //函数必须是 static 的才能直接使用线程池
    std::cout << n << " hello, Afun ! " << std::this_thread::get_id() << std::endl;
    return n;
  }

  static std::string Bfun(int n, std::string str, char c) {
    std::cout << n << " hello, Bfun ! "<< str.c_str() <<" " << (int)c <<" " << std::this_thread::get_id() << std::endl;
    return str;
  }
};

int main()
  try {
    std::threadpool executor{ 50 };
    A a;
    std::future<void> ff = executor.commit(fun1,0);
    std::future<int> fg = executor.commit(gfun{},0);
    std::future<int> gg = executor.commit(a.Afun, 9999); //IDE提示错误,但可以编译运行
    std::future<std::string> gh = executor.commit(A::Bfun, 9998,"mult args", 123);
    std::future<std::string> fh = executor.commit([]()->std::string { std::cout << "hello, fh ! " << std::this_thread::get_id() << std::endl; return "hello,fh ret !"; });

    std::cout << " ======= sleep ========= " << std::this_thread::get_id() << std::endl;
    std::this_thread::sleep_for(std::chrono::microseconds(900));

    for (int i = 0; i < 50; i++) {
      executor.commit(fun1,i*100 );
    }
    std::cout << " ======= commit all ========= " << std::this_thread::get_id()<< " idlsize="<<executor.idlCount() << std::endl;

    std::cout << " ======= sleep ========= " << std::this_thread::get_id() << std::endl;
    std::this_thread::sleep_for(std::chrono::seconds(3));

    ff.get(); //调用.get()获取返回值会等待线程执行完,获取返回值
    std::cout << fg.get() << " " << fh.get().c_str()<< " " << std::this_thread::get_id() << std::endl;

    std::cout << " ======= sleep ========= " << std::this_thread::get_id() << std::endl;
    std::this_thread::sleep_for(std::chrono::seconds(3));

    std::cout << " ======= fun1,55 ========= " << std::this_thread::get_id() << std::endl;
    executor.commit(fun1,55).get();  //调用.get()获取返回值会等待线程执行完

    std::cout << "end... " << std::this_thread::get_id() << std::endl;


    std::threadpool pool(4);
    std::vector< std::future<int> > results;

    for (int i = 0; i < 8; ++i) {
      results.emplace_back(
        pool.commit([i] {
          std::cout << "hello " << i << std::endl;
          std::this_thread::sleep_for(std::chrono::seconds(1));
          std::cout << "world " << i << std::endl;
          return i*i;
        })
      );
    }
    std::cout << " ======= commit all2 ========= " << std::this_thread::get_id() << std::endl;

    for (auto && result : results)
      std::cout << result.get() << ' ';
    std::cout << std::endl;
    return 0;
  }
catch (std::exception& e) {
  std::cout << "some unhappy happened... " << std::this_thread::get_id() << e.what() << std::endl;
}