/*****************************************************************************************
 *                                                                                       *
 * OpenSpace                                                                             *
 *                                                                                       *
 * Copyright (c) 2014-2016                                                               *
 *                                                                                       *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this  *
 * software and associated documentation files (the "Software"), to deal in the Software *
 * without restriction, including without limitation the rights to use, copy, modify,    *
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to    *
 * permit persons to whom the Software is furnished to do so, subject to the following   *
 * conditions:                                                                           *
 *                                                                                       *
 * The above copyright notice and this permission notice shall be included in all copies *
 * or substantial portions of the Software.                                              *
 *                                                                                       *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,   *
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A         *
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT    *
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF  *
 * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE  *
 * OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                                         *
 ****************************************************************************************/



#include <glm/glm.hpp>
#include <memory>
#include <ostream>
#include <thread>
#include <queue>

#include <modules/globebrowsing/other/concurrentqueue.h>
#include <modules/globebrowsing/other/threadpool.h>

#include <ghoul/misc/assert.h>
#include <iostream>



namespace openspace {

    Worker::Worker(ThreadPool& pool)
        : pool(pool)
    {

    }

    void Worker::operator()() {
        std::function<void()> task;
        while (true) {

            // acquire lock
            {
                std::unique_lock<std::mutex> lock(pool.queue_mutex);

                // look for a work item
                while (!pool.stop && pool.tasks.empty()) {
                    // if there are none wait for notification
                    pool.condition.wait(lock);
                }

                if (pool.stop) { // exit if the pool is stopped
                    return;
                }

                // get the task from the queue
                task = pool.tasks.front();
                pool.tasks.pop_front();

            }// release lock

            // execute the task
            task();
        }

        
    }





    ThreadPool::ThreadPool(size_t numThreads)
        : stop(false)
    {
        for (size_t i = 0; i < numThreads; ++i) {
            workers.push_back(std::thread(Worker(*this)));
        }
    }

    // the destructor joins all threads
    ThreadPool::~ThreadPool() {
        // stop all threads
        stop = true;
        condition.notify_all();

        // join them
        for (size_t i = 0; i < workers.size(); ++i) {
            workers[i].join();
        }
    }
    

    // add new work item to the pool
    void ThreadPool::enqueue(std::function<void()> f) {
        { // acquire lock
            std::unique_lock<std::mutex> lock(queue_mutex);

            // add the task
            tasks.push_back(f);
        } // release lock

          // wake up one thread
        condition.notify_one();
    }

    void ThreadPool::clearTasks() {
        { // acquire lock
            std::unique_lock<std::mutex> lock(queue_mutex);
            tasks.clear();
        } // release lock
    }


} // namespace openspace