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

   This file is part of the JUCE library.
   Copyright (c) 2016 - ROLI Ltd.

   Permission is granted to use this software 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.

   THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD
   TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
   OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
   USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
   TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   OF THIS SOFTWARE.

   -----------------------------------------------------------------------------

   To release a closed-source product which uses other parts of JUCE not
   licensed under the ISC terms, commercial licenses are available: visit
   www.juce.com for more information.

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

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);
}
