// ThreadPool.cpp

#include <thread>
#include <chrono>
#include <iostream>
#include <sstream>
#include "ThreadPool.h"
#include "../Logger/Logger.h"
#include "../Utilities/Utilities.h"

using Show = StaticLogger<0>;
using DebugLog = StaticLogger<1>;

ThreadPool::ThreadPool(size_t n)
{
  CallObj threadProc = [this]()
  {
    while (true)
    {
      CallObj* pCo = Q_.deQ();
      if (pCo == nullptr)
      {
        DebugLog::write("\n--deQed nullptr in ThreadPool");
        Q_.enQ(nullptr);
        break;
      }
      (*pCo)();
      delete pCo;  // this is a copy on heap so delete
    }
    DebugLog::write(
      "\n  thread " + 
      Utilities::Converter<std::thread::id>::toString(std::this_thread::get_id()) + 
      " terminating"
    );
  };
  for (size_t i = 0; i < n; ++i)
  {
    std::thread t(threadProc);
    threads_.push_back(std::move(t));
    DebugLog::write(
      "\n--starting threadpool thread " + 
      Utilities::Converter<std::thread::id>::toString(t.get_id())
    );
  }
}

void ThreadPool::workItem(CallObj* pCo)
{
  if (pCo == nullptr)
  {
    DebugLog::write("\n  enqueuing nullptr in threadpool");
    Q_.enQ(pCo);
    return;
  }
  CallObj* pCnew = new CallObj(*pCo);  // make copy as orig may change
  Q_.enQ(pCnew);
  DebugLog::write(
    "\n--threadpool queue size = " + 
    Utilities::Converter<size_t>::toString(Q_.size())
  );
}

void ThreadPool::wait()
{
  DebugLog::write(
    "\n  entering wait with queue size = " + 
    Utilities::Converter<size_t>::toString(Q_.size())
  );
  for (auto& thrd : threads_)
    thrd.join();
  DebugLog::write(
    "\n--leaving wait with queue size = " + 
    Utilities::Converter<size_t>::toString(Q_.size())
  );
}

ThreadPool::~ThreadPool()
{
  for (auto& thrd : threads_)
  {
    if (thrd.joinable())
      thrd.join();
  }
}

//----< test stub >--------------------------------------------------

#ifdef TEST_THREADPOOL

#include <iostream>
using namespace std::chrono_literals;
using namespace Utilities;
using Utils = StringHelper;

int main()
{
  Show::attach(&std::cout);
  Show::start();
  DebugLog::attach(&std::cout);
  //DebugLog::start();

  Utils::Title("Testing ThreadPool");

  ThreadPool trpl(8);

  ThreadPool::CallObj co = [&trpl]() { 
    Show::write(
      "\n  hello from thread " + 
      Utilities::Converter<std::thread::id>::toString(std::this_thread::get_id())
    ); 
  };

  for (size_t i = 0; i < 20; ++i)
    trpl.workItem(&co);
  trpl.workItem(nullptr);
  trpl.wait();

  //std::cout << "\n\n";
}

#endif