/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

   JUCE is an open source library subject to commercial or open-source
   licensing.

   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

class ThreadPool::ThreadPoolThread  : public Thread
{
public:
    ThreadPoolThread (ThreadPool& p, size_t stackSize = 0)
       : Thread ("Pool", stackSize), currentJob (nullptr), pool (p)
    {
    }

    void run() override
    {
        while (! threadShouldExit())
            if (! pool.runNextJob (*this))
                wait (500);
    }

    ThreadPoolJob* volatile currentJob;
    ThreadPool& pool;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (ThreadPoolThread)
};

//==============================================================================
ThreadPoolJob::ThreadPoolJob (const String& name)
    : jobName (name), pool (nullptr),
      shouldStop (false), isActive (false), shouldBeDeleted (false)
{
}

ThreadPoolJob::~ThreadPoolJob()
{
    // you mustn't delete a job while it's still in a pool! Use ThreadPool::removeJob()
    // to remove it first!
    jassert (pool == nullptr || ! pool->contains (this));
}

String ThreadPoolJob::getJobName() const
{
    return jobName;
}

void ThreadPoolJob::setJobName (const String& newName)
{
    jobName = newName;
}

void ThreadPoolJob::signalJobShouldExit()
{
    shouldStop = true;
}

ThreadPoolJob* ThreadPoolJob::getCurrentThreadPoolJob()
{
    if (ThreadPool::ThreadPoolThread* t = dynamic_cast<ThreadPool::ThreadPoolThread*> (Thread::getCurrentThread()))
        return t->currentJob;

    return nullptr;
}

//==============================================================================
ThreadPool::ThreadPool (const int numThreads, size_t threadStackSize)
{
    jassert (numThreads > 0); // not much point having a pool without any threads!

    createThreads (numThreads, threadStackSize);
}

ThreadPool::ThreadPool()
{
    createThreads (SystemStats::getNumCpus());
}

ThreadPool::~ThreadPool()
{
    removeAllJobs (true, 5000);
    stopThreads();
}

void ThreadPool::createThreads (int numThreads, size_t threadStackSize)
{
    for (int i = jmax (1, numThreads); --i >= 0;)
        threads.add (new ThreadPoolThread (*this, threadStackSize));

    for (int i = threads.size(); --i >= 0;)
        threads.getUnchecked(i)->startThread();
}

void ThreadPool::stopThreads()
{
    for (int i = threads.size(); --i >= 0;)
        threads.getUnchecked(i)->signalThreadShouldExit();

    for (int i = threads.size(); --i >= 0;)
        threads.getUnchecked(i)->stopThread (500);
}

void ThreadPool::addJob (ThreadPoolJob* const job, const bool deleteJobWhenFinished)
{
    jassert (job != nullptr);
    jassert (job->pool == nullptr);

    if (job->pool == nullptr)
    {
        job->pool = this;
        job->shouldStop = false;
        job->isActive = false;
        job->shouldBeDeleted = deleteJobWhenFinished;

        {
            const ScopedLock sl (lock);
            jobs.add (job);
        }

        for (int i = threads.size(); --i >= 0;)
            threads.getUnchecked(i)->notify();
    }
}

int ThreadPool::getNumJobs() const
{
    return jobs.size();
}

int ThreadPool::getNumThreads() const
{
    return threads.size();
}

ThreadPoolJob* ThreadPool::getJob (const int index) const
{
    const ScopedLock sl (lock);
    return jobs [index];
}

bool ThreadPool::contains (const ThreadPoolJob* const job) const
{
    const ScopedLock sl (lock);
    return jobs.contains (const_cast<ThreadPoolJob*> (job));
}

bool ThreadPool::isJobRunning (const ThreadPoolJob* const job) const
{
    const ScopedLock sl (lock);
    return jobs.contains (const_cast<ThreadPoolJob*> (job)) && job->isActive;
}

bool ThreadPool::waitForJobToFinish (const ThreadPoolJob* const job, const int timeOutMs) const
{
    if (job != nullptr)
    {
        const uint32 start = Time::getMillisecondCounter();

        while (contains (job))
        {
            if (timeOutMs >= 0 && Time::getMillisecondCounter() >= start + (uint32) timeOutMs)
                return false;

            jobFinishedSignal.wait (2);
        }
    }

    return true;
}

bool ThreadPool::removeJob (ThreadPoolJob* const job,
                            const bool interruptIfRunning,
                            const int timeOutMs)
{
    bool dontWait = true;
    OwnedArray<ThreadPoolJob> deletionList;

    if (job != nullptr)
    {
        const ScopedLock sl (lock);

        if (jobs.contains (job))
        {
            if (job->isActive)
            {
                if (interruptIfRunning)
                    job->signalJobShouldExit();

                dontWait = false;
            }
            else
            {
                jobs.removeFirstMatchingValue (job);
                addToDeleteList (deletionList, job);
            }
        }
    }

    return dontWait || waitForJobToFinish (job, timeOutMs);
}

bool ThreadPool::removeAllJobs (const bool interruptRunningJobs, const int timeOutMs,
                                ThreadPool::JobSelector* const selectedJobsToRemove)
{
    Array <ThreadPoolJob*> jobsToWaitFor;

    {
        OwnedArray<ThreadPoolJob> deletionList;

        {
            const ScopedLock sl (lock);

            for (int i = jobs.size(); --i >= 0;)
            {
                ThreadPoolJob* const job = jobs.getUnchecked(i);

                if (selectedJobsToRemove == nullptr || selectedJobsToRemove->isJobSuitable (job))
                {
                    if (job->isActive)
                    {
                        jobsToWaitFor.add (job);

                        if (interruptRunningJobs)
                            job->signalJobShouldExit();
                    }
                    else
                    {
                        jobs.remove (i);
                        addToDeleteList (deletionList, job);
                    }
                }
            }
        }
    }

    const uint32 start = Time::getMillisecondCounter();

    for (;;)
    {
        for (int i = jobsToWaitFor.size(); --i >= 0;)
        {
            ThreadPoolJob* const job = jobsToWaitFor.getUnchecked (i);

            if (! isJobRunning (job))
                jobsToWaitFor.remove (i);
        }

        if (jobsToWaitFor.size() == 0)
            break;

        if (timeOutMs >= 0 && Time::getMillisecondCounter() >= start + (uint32) timeOutMs)
            return false;

        jobFinishedSignal.wait (20);
    }

    return true;
}

StringArray ThreadPool::getNamesOfAllJobs (const bool onlyReturnActiveJobs) const
{
    StringArray s;
    const ScopedLock sl (lock);

    for (int i = 0; i < jobs.size(); ++i)
    {
        const ThreadPoolJob* const job = jobs.getUnchecked(i);
        if (job->isActive || ! onlyReturnActiveJobs)
            s.add (job->getJobName());
    }

    return s;
}

bool ThreadPool::setThreadPriorities (const int newPriority)
{
    bool ok = true;

    for (int i = threads.size(); --i >= 0;)
        if (! threads.getUnchecked(i)->setPriority (newPriority))
            ok = false;

    return ok;
}

ThreadPoolJob* ThreadPool::pickNextJobToRun()
{
    OwnedArray<ThreadPoolJob> deletionList;

    {
        const ScopedLock sl (lock);

        for (int i = 0; i < jobs.size(); ++i)
        {
            ThreadPoolJob* job = jobs[i];

            if (job != nullptr && ! job->isActive)
            {
                if (job->shouldStop)
                {
                    jobs.remove (i);
                    addToDeleteList (deletionList, job);
                    --i;
                    continue;
                }

                job->isActive = true;
                return job;
            }
        }
    }

    return nullptr;
}

bool ThreadPool::runNextJob (ThreadPoolThread& thread)
{
    if (ThreadPoolJob* const job = pickNextJobToRun())
    {
        ThreadPoolJob::JobStatus result = ThreadPoolJob::jobHasFinished;
        thread.currentJob = job;

        try
        {
            result = job->runJob();
        }
        catch (...)
        {
            jassertfalse; // Your runJob() method mustn't throw any exceptions!
        }

        thread.currentJob = nullptr;

        OwnedArray<ThreadPoolJob> deletionList;

        {
            const ScopedLock sl (lock);

            if (jobs.contains (job))
            {
                job->isActive = false;

                if (result != ThreadPoolJob::jobNeedsRunningAgain || job->shouldStop)
                {
                    jobs.removeFirstMatchingValue (job);
                    addToDeleteList (deletionList, job);

                    jobFinishedSignal.signal();
                }
                else
                {
                    // move the job to the end of the queue if it wants another go
                    jobs.move (jobs.indexOf (job), -1);
                }
            }
        }

        return true;
    }

    return false;
}

void ThreadPool::addToDeleteList (OwnedArray<ThreadPoolJob>& deletionList, ThreadPoolJob* const job) const
{
    job->shouldStop = true;
    job->pool = nullptr;

    if (job->shouldBeDeleted)
        deletionList.add (job);
}
