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

   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 Timer::TimerThread  : private Thread,
                            private DeletedAtShutdown,
                            private AsyncUpdater
{
public:
    typedef CriticalSection LockType; // (mysteriously, using a SpinLock here causes problems on some XP machines..)

    TimerThread()
        : Thread ("Juce Timer"),
          firstTimer (nullptr)
    {
        triggerAsyncUpdate();
    }

    ~TimerThread() noexcept
    {
        signalThreadShouldExit();
        callbackArrived.signal();
        stopThread (4000);

        jassert (instance == this || instance == nullptr);
        if (instance == this)
            instance = nullptr;
    }

    void run() override
    {
        uint32 lastTime = Time::getMillisecondCounter();
        MessageManager::MessageBase::Ptr messageToSend (new CallTimersMessage());

        while (! threadShouldExit())
        {
            const uint32 now = Time::getMillisecondCounter();

            const int elapsed = (int) (now >= lastTime ? (now - lastTime)
                                                       : (std::numeric_limits<uint32>::max() - (lastTime - now)));
            lastTime = now;

            const int timeUntilFirstTimer = getTimeUntilFirstTimer (elapsed);

            if (timeUntilFirstTimer <= 0)
            {
                if (callbackArrived.wait (0))
                {
                    // already a message in flight - do nothing..
                }
                else
                {
                    messageToSend->post();

                    if (! callbackArrived.wait (300))
                    {
                        // Sometimes our message can get discarded by the OS (e.g. when running as an RTAS
                        // when the app has a modal loop), so this is how long to wait before assuming the
                        // message has been lost and trying again.
                        messageToSend->post();
                    }

                    continue;
                }
            }

            // don't wait for too long because running this loop also helps keep the
            // Time::getApproximateMillisecondTimer value stay up-to-date
            wait (jlimit (1, 100, timeUntilFirstTimer));
        }
    }

    void callTimers()
    {
        // avoid getting stuck in a loop if a timer callback repeatedly takes too long
        const uint32 timeout = Time::getMillisecondCounter() + 100;

        const LockType::ScopedLockType sl (lock);

        while (firstTimer != nullptr && firstTimer->timerCountdownMs <= 0)
        {
            Timer* const t = firstTimer;
            t->timerCountdownMs = t->timerPeriodMs;

            removeTimer (t);
            addTimer (t);

            const LockType::ScopedUnlockType ul (lock);

            JUCE_TRY
            {
                t->timerCallback();
            }
            JUCE_CATCH_EXCEPTION

            if (Time::getMillisecondCounter() > timeout)
                break;
        }

        callbackArrived.signal();
    }

    void callTimersSynchronously()
    {
        if (! isThreadRunning())
        {
            // (This is relied on by some plugins in cases where the MM has
            // had to restart and the async callback never started)
            cancelPendingUpdate();
            triggerAsyncUpdate();
        }

        callTimers();
    }

    static inline void add (Timer* const tim) noexcept
    {
        if (instance == nullptr)
            instance = new TimerThread();

        instance->addTimer (tim);
    }

    static inline void remove (Timer* const tim) noexcept
    {
        if (instance != nullptr)
            instance->removeTimer (tim);
    }

    static inline void resetCounter (Timer* const tim, const int newCounter) noexcept
    {
        if (instance != nullptr)
        {
            tim->timerCountdownMs = newCounter;
            tim->timerPeriodMs = newCounter;

            if ((tim->nextTimer != nullptr && tim->nextTimer->timerCountdownMs < tim->timerCountdownMs)
                 || (tim->previousTimer != nullptr && tim->previousTimer->timerCountdownMs > tim->timerCountdownMs))
            {
                instance->removeTimer (tim);
                instance->addTimer (tim);
            }
        }
    }

    static TimerThread* instance;
    static LockType lock;

private:
    Timer* volatile firstTimer;
    WaitableEvent callbackArrived;

    struct CallTimersMessage  : public MessageManager::MessageBase
    {
        CallTimersMessage() {}

        void messageCallback() override
        {
            if (instance != nullptr)
                instance->callTimers();
        }
    };

    //==============================================================================
    void addTimer (Timer* const t) noexcept
    {
       #if JUCE_DEBUG
        // trying to add a timer that's already here - shouldn't get to this point,
        // so if you get this assertion, let me know!
        jassert (! timerExists (t));
       #endif

        Timer* i = firstTimer;

        if (i == nullptr || i->timerCountdownMs > t->timerCountdownMs)
        {
            t->nextTimer = firstTimer;
            firstTimer = t;
        }
        else
        {
            while (i->nextTimer != nullptr && i->nextTimer->timerCountdownMs <= t->timerCountdownMs)
                i = i->nextTimer;

            jassert (i != nullptr);

            t->nextTimer = i->nextTimer;
            t->previousTimer = i;
            i->nextTimer = t;
        }

        if (t->nextTimer != nullptr)
            t->nextTimer->previousTimer = t;

        jassert ((t->nextTimer == nullptr || t->nextTimer->timerCountdownMs >= t->timerCountdownMs)
                  && (t->previousTimer == nullptr || t->previousTimer->timerCountdownMs <= t->timerCountdownMs));

        notify();
    }

    void removeTimer (Timer* const t) noexcept
    {
       #if JUCE_DEBUG
        // trying to remove a timer that's not here - shouldn't get to this point,
        // so if you get this assertion, let me know!
        jassert (timerExists (t));
       #endif

        if (t->previousTimer != nullptr)
        {
            jassert (firstTimer != t);
            t->previousTimer->nextTimer = t->nextTimer;
        }
        else
        {
            jassert (firstTimer == t);
            firstTimer = t->nextTimer;
        }

        if (t->nextTimer != nullptr)
            t->nextTimer->previousTimer = t->previousTimer;

        t->nextTimer = nullptr;
        t->previousTimer = nullptr;
    }

    int getTimeUntilFirstTimer (const int numMillisecsElapsed) const
    {
        const LockType::ScopedLockType sl (lock);

        for (Timer* t = firstTimer; t != nullptr; t = t->nextTimer)
            t->timerCountdownMs -= numMillisecsElapsed;

        return firstTimer != nullptr ? firstTimer->timerCountdownMs : 1000;
    }

    void handleAsyncUpdate() override
    {
        startThread (7);
    }

   #if JUCE_DEBUG
    bool timerExists (Timer* const t) const noexcept
    {
        for (Timer* tt = firstTimer; tt != nullptr; tt = tt->nextTimer)
            if (tt == t)
                return true;

        return false;
    }
   #endif

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (TimerThread)
};

Timer::TimerThread* Timer::TimerThread::instance = nullptr;
Timer::TimerThread::LockType Timer::TimerThread::lock;

//==============================================================================
Timer::Timer() noexcept
   : timerCountdownMs (0),
     timerPeriodMs (0),
     previousTimer (nullptr),
     nextTimer (nullptr)
{
}

Timer::Timer (const Timer&) noexcept
   : timerCountdownMs (0),
     timerPeriodMs (0),
     previousTimer (nullptr),
     nextTimer (nullptr)
{
}

Timer::~Timer()
{
    stopTimer();
}

void Timer::startTimer (const int interval) noexcept
{
    // If you're calling this before (or after) the MessageManager is
    // running, then you're not going to get any timer callbacks!
    jassert (MessageManager::getInstanceWithoutCreating() != nullptr);

    const TimerThread::LockType::ScopedLockType sl (TimerThread::lock);

    if (timerPeriodMs == 0)
    {
        timerCountdownMs = interval;
        timerPeriodMs = jmax (1, interval);
        TimerThread::add (this);
    }
    else
    {
        TimerThread::resetCounter (this, interval);
    }
}

void Timer::startTimerHz (int timerFrequencyHz) noexcept
{
    if (timerFrequencyHz > 0)
        startTimer (1000 / timerFrequencyHz);
    else
        stopTimer();
}

void Timer::stopTimer() noexcept
{
    const TimerThread::LockType::ScopedLockType sl (TimerThread::lock);

    if (timerPeriodMs > 0)
    {
        TimerThread::remove (this);
        timerPeriodMs = 0;
    }
}

void JUCE_CALLTYPE Timer::callPendingTimersSynchronously()
{
    if (TimerThread::instance != nullptr)
        TimerThread::instance->callTimersSynchronously();
}
