/*

Copyright (C) 2017 Xenakios

This program is free software; you can redistribute it and/or modify
it under the terms of version 3 of the GNU General Public License
as published by the Free Software Foundation.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License (version 3) for more details.

www.gnu.org/licenses

*/

#include "ps3_BufferingAudioSource.h"

MyBufferingAudioSource::MyBufferingAudioSource(PositionableAudioSource* s,
                                            TimeSliceThread& thread,
                                            bool deleteSourceWhenDeleted,
                                            int bufferSizeSamples,
                                            int numChannels,
                                            bool prefillBufferOnPrepareToPlay)
    : source (s, deleteSourceWhenDeleted),
      backgroundThread (thread),
      numberOfSamplesToBuffer (jmax (1024, bufferSizeSamples)),
      numberOfChannels (numChannels),
      prefillBuffer (prefillBufferOnPrepareToPlay)
{
    jassert (source != nullptr);

    jassert (numberOfSamplesToBuffer > 1024); // not much point using this class if you're
                                              //  not using a larger buffer..
}

MyBufferingAudioSource::~MyBufferingAudioSource()
{
    releaseResources();
}

//==============================================================================
void MyBufferingAudioSource::prepareToPlay (int samplesPerBlockExpected, double newSampleRate)
{
    auto bufferSizeNeeded = jmax (samplesPerBlockExpected * 2, numberOfSamplesToBuffer);

    if (newSampleRate != sampleRate
         || bufferSizeNeeded != buffer.getNumSamples()
         || ! isPrepared)
    {
        backgroundThread.removeTimeSliceClient (this);

        isPrepared = true;
        sampleRate = newSampleRate;

        source->prepareToPlay (samplesPerBlockExpected, newSampleRate);

        buffer.setSize (numberOfChannels, bufferSizeNeeded);
        buffer.clear();

        bufferValidStart = 0;
        bufferValidEnd = 0;

        backgroundThread.addTimeSliceClient (this);

        do
        {
            backgroundThread.moveToFrontOfQueue (this);
            Thread::sleep (5);
        }
        while (prefillBuffer
         && (bufferValidEnd - bufferValidStart < jmin (((int) newSampleRate) / 4, buffer.getNumSamples() / 2)));
    }
}

void MyBufferingAudioSource::releaseResources()
{
    isPrepared = false;
    backgroundThread.removeTimeSliceClient (this);

    buffer.setSize (numberOfChannels, 0);

    // MSVC2015 seems to need this if statement to not generate a warning during linking.
    // As source is set in the constructor, there is no way that source could
    // ever equal this, but it seems to make MSVC2015 happy.
    if (source != this)
        source->releaseResources();
}

void MyBufferingAudioSource::getNextAudioBlock (const AudioSourceChannelInfo& info)
{
    const ScopedLock sl (bufferStartPosLock);

    auto start = bufferValidStart.load();
    auto end   = bufferValidEnd.load();
    auto pos   = nextPlayPos.load();

    auto validStart = (int) (jlimit (start, end, pos) - pos);
    auto validEnd   = (int) (jlimit (start, end, pos + info.numSamples) - pos);

    if (validStart == validEnd)
    {
        // total cache miss
        info.clearActiveBufferRegion();
    }
    else
    {
        if (validStart > 0)
            info.buffer->clear (info.startSample, validStart);  // partial cache miss at start

        if (validEnd < info.numSamples)
            info.buffer->clear (info.startSample + validEnd,
                                info.numSamples - validEnd);    // partial cache miss at end

        if (validStart < validEnd)
        {
            for (int chan = jmin (numberOfChannels, info.buffer->getNumChannels()); --chan >= 0;)
            {
                jassert (buffer.getNumSamples() > 0);
                auto startBufferIndex = (int) ((validStart + nextPlayPos) % buffer.getNumSamples());
                auto endBufferIndex   = (int) ((validEnd + nextPlayPos)   % buffer.getNumSamples());

                if (startBufferIndex < endBufferIndex)
                {
                    info.buffer->copyFrom (chan, info.startSample + validStart,
                                           buffer,
                                           chan, startBufferIndex,
                                           validEnd - validStart);
                }
                else
                {
                    auto initialSize = buffer.getNumSamples() - startBufferIndex;

                    info.buffer->copyFrom (chan, info.startSample + validStart,
                                           buffer,
                                           chan, startBufferIndex,
                                           initialSize);

                    info.buffer->copyFrom (chan, info.startSample + validStart + initialSize,
                                           buffer,
                                           chan, 0,
                                           (validEnd - validStart) - initialSize);
                }
            }
        }

        nextPlayPos += info.numSamples;
    }
}

bool MyBufferingAudioSource::waitForNextAudioBlockReady (const AudioSourceChannelInfo& info, uint32 timeout)
{
    if (!source || source->getTotalLength() <= 0)
        return false;

    if (nextPlayPos + info.numSamples < 0)
        return true;

    if (! isLooping() && nextPlayPos > getTotalLength())
        return true;

    auto now = Time::getMillisecondCounter();
    auto startTime = now;

    auto elapsed = (now >= startTime ? now - startTime
                                     : (std::numeric_limits<uint32>::max() - startTime) + now);

    while (elapsed <= timeout)
    {
        {
            const ScopedLock sl (bufferStartPosLock);

            auto start = bufferValidStart.load();
            auto end   = bufferValidEnd.load();
            auto pos   = nextPlayPos.load();

            auto validStart = static_cast<int> (jlimit (start, end, pos) - pos);
            auto validEnd   = static_cast<int> (jlimit (start, end, pos + info.numSamples) - pos);

            if (validStart <= 0 && validStart < validEnd && validEnd >= info.numSamples)
                return true;
        }

        if (elapsed < timeout  && (! bufferReadyEvent.wait (static_cast<int> (timeout - elapsed))))
            return false;

        now = Time::getMillisecondCounter();
        elapsed = (now >= startTime ? now - startTime
                                    : (std::numeric_limits<uint32>::max() - startTime) + now);
    }

    return false;
}

int64 MyBufferingAudioSource::getNextReadPosition() const
{
    jassert (source->getTotalLength() > 0);
    auto pos = nextPlayPos.load();

    return (source->isLooping() && nextPlayPos > 0)
                    ? pos % source->getTotalLength()
                    : pos;
}

void MyBufferingAudioSource::setNextReadPosition (int64 newPosition)
{
    const ScopedLock sl (bufferStartPosLock);

    nextPlayPos = newPosition;
    backgroundThread.moveToFrontOfQueue (this);
}

bool MyBufferingAudioSource::readNextBufferChunk()
{
    int64 newBVS, newBVE, sectionToReadStart, sectionToReadEnd;

    {
        const ScopedLock sl (bufferStartPosLock);

        if (wasSourceLooping != isLooping())
        {
            wasSourceLooping = isLooping();
            bufferValidStart = 0;
            bufferValidEnd = 0;
        }

        newBVS = jmax ((int64) 0, nextPlayPos.load());
        newBVE = newBVS + buffer.getNumSamples() - 4;
        sectionToReadStart = 0;
        sectionToReadEnd = 0;

        const int maxChunkSize = 2048;

        if (newBVS < bufferValidStart || newBVS >= bufferValidEnd)
        {
            newBVE = jmin (newBVE, newBVS + maxChunkSize);

            sectionToReadStart = newBVS;
            sectionToReadEnd = newBVE;

            bufferValidStart = 0;
            bufferValidEnd = 0;
        }
        else if (std::abs ((int) (newBVS - bufferValidStart)) > 512
                  || std::abs ((int) (newBVE - bufferValidEnd)) > 512)
        {
            newBVE = jmin (newBVE, bufferValidEnd + maxChunkSize);

            sectionToReadStart = bufferValidEnd;
            sectionToReadEnd = newBVE;

            bufferValidStart = newBVS;
            bufferValidEnd = jmin (bufferValidEnd.load(), newBVE);
        }
    }

    if (sectionToReadStart == sectionToReadEnd)
        return false;

    jassert (buffer.getNumSamples() > 0);
    auto bufferIndexStart = (int) (sectionToReadStart % buffer.getNumSamples());
    auto bufferIndexEnd   = (int) (sectionToReadEnd   % buffer.getNumSamples());

    if (bufferIndexStart < bufferIndexEnd)
    {
        readBufferSection (sectionToReadStart,
                           (int) (sectionToReadEnd - sectionToReadStart),
                           bufferIndexStart);
    }
    else
    {
        auto initialSize = buffer.getNumSamples() - bufferIndexStart;

        readBufferSection (sectionToReadStart,
                           initialSize,
                           bufferIndexStart);

        readBufferSection (sectionToReadStart + initialSize,
                           (int) (sectionToReadEnd - sectionToReadStart) - initialSize,
                           0);
    }

    {
        const ScopedLock sl2 (bufferStartPosLock);

        bufferValidStart = newBVS;
        bufferValidEnd = newBVE;
    }

    bufferReadyEvent.signal();
    return true;
}

void MyBufferingAudioSource::readBufferSection (int64 start, int length, int bufferOffset)
{
    if (source->getNextReadPosition() != start)
        source->setNextReadPosition (start);

    AudioSourceChannelInfo info (&buffer, bufferOffset, length);
    source->getNextAudioBlock (info);
}

int MyBufferingAudioSource::useTimeSlice()
{
    return readNextBufferChunk() ? 1 : 100;
}

double MyBufferingAudioSource::getPercentReady()
{
	if (bufferValidEnd == bufferValidStart)
		return 0.0;
	if (numberOfSamplesToBuffer == 0)
		return 0.0;
	return 1.0 / numberOfSamplesToBuffer * (bufferValidEnd - bufferValidStart);
}