/****************************************************************************
Copyright (c) 2013-2016 Chukong Technologies Inc.
Copyright (c) 2017-2023 Xiamen Yaji Software Co., Ltd.

http://www.cocos2d-x.org

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,
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****************************************************************************/

#pragma once

#include "application/ApplicationManager.h"

#include <condition_variable>
#include <functional>
#include <future>
#include <memory>
#include <mutex>
#include <queue>
#include <stdexcept>
#include <thread>
#include <vector>

/**
* @addtogroup base
* @{
*/
namespace cc {

/**
 * @class AsyncTaskPool
 * @brief This class allows to perform background operations without having to manipulate threads.
 * @js NA
 */
class CC_DLL AsyncTaskPool {
public:
    using TaskCallBack = std::function<void(void *)>;

    enum class TaskType {
        TASK_IO,
        TASK_NETWORK,
        TASK_OTHER,
        TASK_MAX_TYPE,
    };

    /**
     * Returns the shared instance of the async task pool.
     */
    static AsyncTaskPool *getInstance();

    /**
     * Destroys the async task pool.
     */
    static void destroyInstance();

    AsyncTaskPool();
    ~AsyncTaskPool();

    /**
     * Stop tasks.
     *
     * @param type Task type you want to stop.
     */
    void stopTasks(TaskType type);

    /**
     * Enqueue a asynchronous task.
     *
     * @param type task type is io task, network task or others, each type of task has a thread to deal with it.
     * @param callback callback when the task is finished. The callback is called in the main thread instead of task thread.
     * @param callbackParam parameter used by the callback.
     * @param f task can be lambda function.
     * @lua NA
     */
    template <class F>
    inline void enqueue(TaskType type, const TaskCallBack &callback, void *callbackParam, F &&f);

protected:
    // thread tasks internally used
    class ThreadTasks {
        struct AsyncTaskCallBack {
            TaskCallBack callback;
            void *callbackParam;
        };

    public:
        ThreadTasks() {
            _thread = std::thread(
                [this] {
                    for (;;) {
                        std::function<void()> task;
                        AsyncTaskCallBack callback;
                        {
                            std::unique_lock<std::mutex> lock(this->_queueMutex);
                            this->_condition.wait(lock,
                                                  [this] { return this->_stop || !this->_tasks.empty(); });
                            if (this->_stop && this->_tasks.empty()) {
                                return;
                            }
                            task = std::move(this->_tasks.front());
                            callback = std::move(this->_taskCallBacks.front());
                            this->_tasks.pop();
                            this->_taskCallBacks.pop();
                        }

                        task();
                        CC_CURRENT_ENGINE()->getScheduler()->performFunctionInCocosThread([&, callback] { callback.callback(callback.callbackParam); });
                    }
                });
        }
        ~ThreadTasks() {
            {
                std::unique_lock<std::mutex> lock(_queueMutex);
                _stop = true;

                while (!_tasks.empty()) {
                    _tasks.pop();
                }
                while (!_taskCallBacks.empty()) {
                    _taskCallBacks.pop();
                }
            }
            _condition.notify_all();
            _thread.join();
        }
        void clear() {
            std::unique_lock<std::mutex> lock(_queueMutex);
            while (!_tasks.empty()) {
                _tasks.pop();
            }
            while (!_taskCallBacks.empty()) {
                _taskCallBacks.pop();
            }
        }
        template <class F>
        void enqueue(const TaskCallBack &callback, void *callbackParam, F &&f) {
            auto task = f; //std::bind(std::forward<F>(f), std::forward<Args>(args)...);

            {
                std::unique_lock<std::mutex> lock(_queueMutex);

                // don't allow enqueueing after stopping the pool
                if (_stop) {
                    CC_ASSERT(0 && "already stop");
                    return;
                }

                AsyncTaskCallBack taskCallBack;
                taskCallBack.callback = callback;
                taskCallBack.callbackParam = callbackParam;
                _tasks.emplace([task]() { task(); });
                _taskCallBacks.emplace(taskCallBack);
            }
            _condition.notify_one();
        }

    private:
        // need to keep track of thread so we can join them
        std::thread _thread;
        // the task queue
        std::queue<std::function<void()>> _tasks;
        std::queue<AsyncTaskCallBack> _taskCallBacks;

        // synchronization
        std::mutex _queueMutex;
        std::condition_variable _condition;
        bool _stop{false};
    };

    //tasks
    ThreadTasks _threadTasks[static_cast<int>(TaskType::TASK_MAX_TYPE)];

    static AsyncTaskPool *sAsyncTaskPool;
};

inline void AsyncTaskPool::stopTasks(TaskType type) {
    auto &threadTask = _threadTasks[static_cast<int>(type)];
    threadTask.clear();
}

template <class F>
inline void AsyncTaskPool::enqueue(AsyncTaskPool::TaskType type, const TaskCallBack &callback, void *callbackParam, F &&f) {
    auto &threadTask = _threadTasks[static_cast<int>(type)];

    threadTask.enqueue(callback, callbackParam, f);
}

} // namespace cc
// end group
/// @}
