/*
* Copyright 2009-2017 Alibaba Cloud All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

#include "Executor.h"
#include <alibabacloud/core/Runnable.h>

using namespace AlibabaCloud;

Executor *Executor::self_ = nullptr;

Executor::Executor() :
	cvMutex_(),
	shutdown_(true),
	tasksQueue_(),
	tasksQueueMutex_(),
	thread_()
{
	self_ = this;
}

Executor::~Executor()
{
	self_ = nullptr;
	shutdown();
}

Executor * Executor::instance()
{
	return self_;
}

bool Executor::start()
{
	if (!isShutdown())
		return true;

	auto threadMain = [this]()
	{
		while (!shutdown_)
		{
			while (!tasksQueue_.empty())
			{
				Runnable *task = nullptr;
				{
					std::lock_guard<std::mutex> lock(tasksQueueMutex_);
					if (!tasksQueue_.empty())
					{
						task = tasksQueue_.front();
						tasksQueue_.pop();
					}
				}

				if (task) {
					task->run();
					delete task;
				}
			}

			if (!shutdown_) {
				std::unique_lock<std::mutex> lk(cvMutex_);
				cv_.wait(lk);
			}
		}
	};

	shutdown_ = false;
	thread_ = std::thread(threadMain);
	return true;
}

bool Executor::isShutdown()const
{
	return shutdown_;
}

void Executor::execute(Runnable* task)
{
	if (isShutdown())
		return;

	std::lock_guard<std::mutex> locker(tasksQueueMutex_);
	tasksQueue_.push(task);
	wakeUp();
}

void Executor::wakeUp()
{
	std::unique_lock<std::mutex> lk(cvMutex_);
	cv_.notify_one();
}

void Executor::shutdown()
{
	if (isShutdown())
		return;
	
	{
		std::lock_guard<std::mutex> locker(tasksQueueMutex_);
		while (tasksQueue_.size() > 0) {
			auto task = tasksQueue_.front();
			delete task;
			tasksQueue_.pop();
		}
	}

	shutdown_ = true;
	wakeUp();

	if (thread_.joinable())
		thread_.join();
}