/**********************************************************************
 * $Id: cpl_worker_thread_pool.h 1df63aa4d30bc389133c38822002d5ecfb91c314 2020-05-21 11:30:55 +0200 Even Rouault $
 *
 * Project:  CPL - Common Portability Library
 * Purpose:  CPL worker thread pool
 * Author:   Even Rouault, <even dot rouault at spatialys dot com>
 *
 **********************************************************************
 * Copyright (c) 2015, Even Rouault, <even dot rouault at spatialys dot com>
 *
 * 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.
 ****************************************************************************/

#ifndef CPL_WORKER_THREAD_POOL_H_INCLUDED_
#define CPL_WORKER_THREAD_POOL_H_INCLUDED_

#include "cpl_multiproc.h"
#include "cpl_list.h"

#include <condition_variable>
#include <memory>
#include <mutex>
#include <vector>

/**
 * \file cpl_worker_thread_pool.h
 *
 * Class to manage a pool of worker threads.
 * @since GDAL 2.1
 */

#ifndef DOXYGEN_SKIP
struct CPLWorkerThreadJob;
class CPLWorkerThreadPool;

struct CPLWorkerThread
{
    CPL_DISALLOW_COPY_ASSIGN(CPLWorkerThread)
    CPLWorkerThread() = default;

    CPLThreadFunc        pfnInitFunc = nullptr;
    void                *pInitData = nullptr;
    CPLWorkerThreadPool *poTP = nullptr;
    CPLJoinableThread   *hThread = nullptr;
    bool                 bMarkedAsWaiting = false;

    std::mutex              m_mutex{};
    std::condition_variable m_cv{};
};

typedef enum
{
    CPLWTS_OK,
    CPLWTS_STOP,
    CPLWTS_ERROR
} CPLWorkerThreadState;
#endif  // ndef DOXYGEN_SKIP

class CPLJobQueue;

/** Pool of worker threads */
class CPL_DLL CPLWorkerThreadPool
{
        CPL_DISALLOW_COPY_ASSIGN(CPLWorkerThreadPool)

        std::vector<std::unique_ptr<CPLWorkerThread>> aWT{};
        std::mutex              m_mutex{};
        std::condition_variable m_cv{};
        volatile CPLWorkerThreadState eState = CPLWTS_OK;
        CPLList* psJobQueue = nullptr;
        volatile int nPendingJobs = 0;

        CPLList* psWaitingWorkerThreadsList = nullptr;
        int nWaitingWorkerThreads = 0;

        static void WorkerThreadFunction(void* user_data);

        void DeclareJobFinished();
        CPLWorkerThreadJob* GetNextJob(CPLWorkerThread* psWorkerThread);

    public:
        CPLWorkerThreadPool();
       ~CPLWorkerThreadPool();


        bool Setup(int nThreads,
                   CPLThreadFunc pfnInitFunc,
                   void** pasInitData);
        bool Setup(int nThreads,
                   CPLThreadFunc pfnInitFunc,
                   void** pasInitData,
                   bool bWaitallStarted);

        std::unique_ptr<CPLJobQueue> CreateJobQueue();

        bool SubmitJob(CPLThreadFunc pfnFunc, void* pData);
        bool SubmitJobs(CPLThreadFunc pfnFunc, const std::vector<void*>& apData);
        void WaitCompletion(int nMaxRemainingJobs = 0);
        void WaitEvent();

        /** Return the number of threads setup */
        int GetThreadCount() const { return static_cast<int>(aWT.size()); }
};

/** Job queue */
class CPL_DLL CPLJobQueue
{
        CPL_DISALLOW_COPY_ASSIGN(CPLJobQueue)
        CPLWorkerThreadPool* m_poPool = nullptr;
        std::mutex m_mutex{};
        std::condition_variable m_cv{};
        int m_nPendingJobs = 0;

        static void JobQueueFunction(void*);
        void DeclareJobFinished();

//! @cond Doxygen_Suppress
protected:
        friend class CPLWorkerThreadPool;
        explicit CPLJobQueue(CPLWorkerThreadPool* poPool);
//! @endcond

public:
        ~CPLJobQueue();

        /** Return the owning worker thread pool */
        CPLWorkerThreadPool* GetPool() { return m_poPool; }

        bool SubmitJob(CPLThreadFunc pfnFunc, void* pData);
        void WaitCompletion(int nMaxRemainingJobs = 0);
};

#endif // CPL_WORKER_THREAD_POOL_H_INCLUDED_