#include "threadpool.h"

namespace dwt {

threadpool::threadpool(unsigned threads)
    : ready_(false), done_(false), joined_(false),
      tasks_(), threads_(), tasks_mtx_(), go_()
{
    for (unsigned i = 0; i < threads; ++i)
        threads_.emplace_back(std::bind(&worker_thread_, this));
}

threadpool::~threadpool()
{
    if (!joined_)
        join_all();
}

void threadpool::done()
{
    std::unique_lock<std::mutex> lock(tasks_mtx_);
    done_ = true;
}

void threadpool::join_all()
{
    if (!done_)
        done();
    for (auto& t: threads_)
        t.join();
    joined_ = true;
}

void threadpool::worker_thread_()
{
    // wait for kickoff, if it hasn't happened yet
    {
        std::unique_lock<std::mutex> lock(tasks_mtx_);
        if (!ready_)
            go_.wait(lock);
    }

    std::packaged_task<void()> current_task;
    while (true) {
        {
            std::unique_lock<std::mutex> lock(tasks_mtx_);
            if (!tasks_.empty()) {
                current_task = std::move(tasks_.front());
                tasks_.pop();
            } else /* tasks_ is empty */ if (done_) {
                break;
            } else /* empty, but not done: try again */ {
                continue;
            }
        }
        current_task();
    }
}

}