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

   This file is part of the JUCE framework.
   Copyright (c) Raw Material Software Limited

   JUCE is an open source framework subject to commercial or open source
   licensing.

   By downloading, installing, or using the JUCE framework, or combining the
   JUCE framework with any other source code, object code, content or any other
   copyrightable work, you agree to the terms of the JUCE End User Licence
   Agreement, and all incorporated terms including the JUCE Privacy Policy and
   the JUCE Website Terms of Service, as applicable, which will bind you. If you
   do not agree to the terms of these agreements, we will not license the JUCE
   framework to you, and you must discontinue the installation or download
   process and cease use of the JUCE framework.

   JUCE End User Licence Agreement: https://juce.com/legal/juce-8-licence/
   JUCE Privacy Policy: https://juce.com/juce-privacy-policy
   JUCE Website Terms of Service: https://juce.com/juce-website-terms-of-service/

   Or:

   You may also use this code under the terms of the AGPLv3:
   https://www.gnu.org/licenses/agpl-3.0.en.html

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

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

namespace juce
{

#define JNI_CLASS_MEMBERS(METHOD, STATICMETHOD, FIELD, STATICFIELD, CALLBACK) \
DECLARE_JNI_CLASS (AndroidAudioManager, "android/media/AudioManager")
#undef JNI_CLASS_MEMBERS

//==============================================================================
#ifndef SL_ANDROID_DATAFORMAT_PCM_EX
 #define SL_ANDROID_DATAFORMAT_PCM_EX                   ((SLuint32) 0x00000004)
#endif

#ifndef SL_ANDROID_PCM_REPRESENTATION_FLOAT
 #define SL_ANDROID_PCM_REPRESENTATION_FLOAT            ((SLuint32) 0x00000003)
#endif

#ifndef SL_ANDROID_RECORDING_PRESET_UNPROCESSED
 #define SL_ANDROID_RECORDING_PRESET_UNPROCESSED        ((SLuint32) 0x00000005)
#endif

//==============================================================================
struct PCMDataFormatEx final : SLDataFormat_PCM
{
    SLuint32 representation;
};

//==============================================================================
template <typename T> struct IntfIID;
template <> struct IntfIID<SLObjectItf_>                   { static SLInterfaceID_ iid; };
template <> struct IntfIID<SLEngineItf_>                   { static SLInterfaceID_ iid; };
template <> struct IntfIID<SLOutputMixItf_>                { static SLInterfaceID_ iid; };
template <> struct IntfIID<SLPlayItf_>                     { static SLInterfaceID_ iid; };
template <> struct IntfIID<SLRecordItf_>                   { static SLInterfaceID_ iid; };
template <> struct IntfIID<SLAndroidSimpleBufferQueueItf_> { static SLInterfaceID_ iid; };
template <> struct IntfIID<SLAndroidConfigurationItf_>     { static SLInterfaceID_ iid; };

SLInterfaceID_ IntfIID<SLObjectItf_>::iid                   = { 0x79216360, 0xddd7, 0x11db, 0xac16, {0x00, 0x02, 0xa5, 0xd5, 0xc5, 0x1b} };
SLInterfaceID_ IntfIID<SLEngineItf_>::iid                   = { 0x8d97c260, 0xddd4, 0x11db, 0x958f, {0x00, 0x02, 0xa5, 0xd5, 0xc5, 0x1b} };
SLInterfaceID_ IntfIID<SLOutputMixItf_>::iid                = { 0x97750f60, 0xddd7, 0x11db, 0x92b1, {0x00, 0x02, 0xa5, 0xd5, 0xc5, 0x1b} };
SLInterfaceID_ IntfIID<SLPlayItf_>::iid                     = { 0xef0bd9c0, 0xddd7, 0x11db, 0xbf49, {0x00, 0x02, 0xa5, 0xd5, 0xc5, 0x1b} };
SLInterfaceID_ IntfIID<SLRecordItf_>::iid                   = { 0xc5657aa0, 0xdddb, 0x11db, 0x82f7, {0x00, 0x02, 0xa5, 0xd5, 0xc5, 0x1b} };
SLInterfaceID_ IntfIID<SLAndroidSimpleBufferQueueItf_>::iid = { 0x198e4940, 0xc5d7, 0x11df, 0xa2a6, {0x00, 0x02, 0xa5, 0xd5, 0xc5, 0x1b} };
SLInterfaceID_ IntfIID<SLAndroidConfigurationItf_>::iid     = { 0x89f6a7e0, 0xbeac, 0x11df, 0x8b5c, {0x00, 0x02, 0xa5, 0xd5, 0xc5, 0x1b} };

template <typename SLObjectType>
static void destroyObject (SLObjectType object)
{
    if (object != nullptr && *object != nullptr)
        (*object)->Destroy (object);
}

struct SLObjectItfFree
{
    void operator() (SLObjectItf obj) const noexcept
    {
        destroyObject (obj);
    }
};

//==============================================================================
// Some life-time and type management of OpenSL objects
class SlObjectRef
{
public:
    //==============================================================================
    SlObjectRef() noexcept {}
    SlObjectRef (const SlObjectRef& obj) noexcept : cb (obj.cb) {}
    SlObjectRef (SlObjectRef&& obj) noexcept : cb (std::move (obj.cb)) { obj.cb = nullptr; }
    explicit SlObjectRef (SLObjectItf o) : cb (new ControlBlock (o)) {}

    //==============================================================================
    SlObjectRef& operator= (const SlObjectRef& r) noexcept  { cb = r.cb; return *this; }
    SlObjectRef& operator= (SlObjectRef&& r) noexcept       { cb = std::move (r.cb); r.cb = nullptr; return *this; }
    SlObjectRef& operator= (std::nullptr_t) noexcept        { cb = nullptr; return *this; }

    //==============================================================================
    const SLObjectItf_* operator*() noexcept                { return *cb->ptr.get(); }
    SLObjectItf operator->() noexcept                       { return (cb == nullptr ? nullptr :  cb->ptr.get()); }
    operator SLObjectItf() noexcept                         { return (cb == nullptr ? nullptr :  cb->ptr.get()); }

    //==============================================================================
    bool operator== (nullptr_t) const noexcept              { return (cb == nullptr || cb->ptr == nullptr); }
    bool operator!= (nullptr_t) const noexcept              { return (cb != nullptr && cb->ptr != nullptr); }

private:
    //==============================================================================
    struct ControlBlock final : ReferenceCountedObject
    {
        ControlBlock() = default;
        ControlBlock (SLObjectItf o) : ptr (o) {}

        std::unique_ptr<const SLObjectItf_* const, SLObjectItfFree> ptr;
    };

    ReferenceCountedObjectPtr<ControlBlock> cb;
};

template <typename T>
class SlRef final : public SlObjectRef
{
public:
    //==============================================================================
    SlRef() noexcept {}
    SlRef (const SlRef& r) noexcept : SlObjectRef (r), type (r.type) {}
    SlRef (SlRef&& r) noexcept : SlObjectRef (std::move (r)), type (r.type) { r.type = nullptr; }

    //==============================================================================
    SlRef& operator= (const SlRef& r)  noexcept { SlObjectRef::operator= (r); type = r.type; return *this; }
    SlRef& operator= (SlRef&& r) noexcept       { SlObjectRef::operator= (std::move (r)); type = r.type; r.type = nullptr; return *this; }
    SlRef& operator= (std::nullptr_t) noexcept  { SlObjectRef::operator= (nullptr); type = nullptr; return *this; }

    //==============================================================================
    T* const operator*() noexcept               { return *type; }
    T* const* operator->() noexcept             { return type; }
    operator T* const*() noexcept               { return type; }

    //==============================================================================
    static SlRef cast (SlObjectRef&  base)      { return SlRef (base); }
    static SlRef cast (SlObjectRef&& base)      { return SlRef (std::move (base)); }

private:
    SlRef (SlObjectRef& base) : SlObjectRef (base)
    {
        if (auto obj = SlObjectRef::operator->())
        {
            auto err = (*obj)->GetInterface (obj, &IntfIID<T>::iid, &type);

            if (type != nullptr && err == SL_RESULT_SUCCESS)
                return;
        }

        *this = nullptr;
    }

    SlRef (SlObjectRef&& base) : SlObjectRef (std::move (base))
    {
        if (auto obj = SlObjectRef::operator->())
        {
            auto err = (*obj)->GetInterface (obj, &IntfIID<T>::iid, &type);
            base = nullptr;

            if (type != nullptr && err == SL_RESULT_SUCCESS)
                return;
        }

        *this = nullptr;
    }

    T* const* type = nullptr;
};

//==============================================================================
template <typename T> struct BufferHelpers {};

template <>
struct BufferHelpers<int16>
{
    enum { isFloatingPoint = 0 };

    static void initPCMDataFormat (PCMDataFormatEx& dataFormat, int numChannels, double sampleRate)
    {
        dataFormat.formatType     = SL_DATAFORMAT_PCM;
        dataFormat.numChannels    = (SLuint32) numChannels;
        dataFormat.samplesPerSec  = (SLuint32) (sampleRate * 1000);
        dataFormat.bitsPerSample  = SL_PCMSAMPLEFORMAT_FIXED_16;
        dataFormat.containerSize  = SL_PCMSAMPLEFORMAT_FIXED_16;
        dataFormat.channelMask    = (numChannels == 1) ? SL_SPEAKER_FRONT_CENTER :
                                                        (SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT);
        dataFormat.endianness     = SL_BYTEORDER_LITTLEENDIAN;
        dataFormat.representation = 0;
    }

    static void prepareCallbackBuffer (AudioBuffer<float>&, int16*) {}

    using LittleEndianInt16 = AudioData::Format<AudioData::Int16,   AudioData::LittleEndian>;
    using NativeFloat32     = AudioData::Format<AudioData::Float32, AudioData::NativeEndian>;

    static void convertFromOpenSL (const int16* srcInterleaved, AudioBuffer<float>& audioBuffer)
    {
        const auto numChannels = audioBuffer.getNumChannels();

        AudioData::deinterleaveSamples (AudioData::InterleavedSource<LittleEndianInt16> { reinterpret_cast<const uint16*> (srcInterleaved), numChannels },
                                        AudioData::NonInterleavedDest<NativeFloat32>    { audioBuffer.getArrayOfWritePointers(),            numChannels },
                                        audioBuffer.getNumSamples());
    }

    static void convertToOpenSL (const AudioBuffer<float>& audioBuffer, int16* dstInterleaved)
    {
        const auto numChannels = audioBuffer.getNumChannels();

        AudioData::interleaveSamples (AudioData::NonInterleavedSource<NativeFloat32> { audioBuffer.getArrayOfReadPointers(),       numChannels },
                                      AudioData::InterleavedDest<LittleEndianInt16>  { reinterpret_cast<uint16*> (dstInterleaved), numChannels },
                                      audioBuffer.getNumSamples());
    }

};

template <>
struct BufferHelpers<float>
{
    enum { isFloatingPoint = 1 };

    static void initPCMDataFormat (PCMDataFormatEx& dataFormat, int numChannels, double sampleRate)
    {
        dataFormat.formatType     = SL_ANDROID_DATAFORMAT_PCM_EX;
        dataFormat.numChannels    = (SLuint32) numChannels;
        dataFormat.samplesPerSec  = (SLuint32) (sampleRate * 1000);
        dataFormat.bitsPerSample  = 32;
        dataFormat.containerSize  = 32;
        dataFormat.channelMask    = (numChannels == 1) ? SL_SPEAKER_FRONT_CENTER :
                                                        (SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT);
        dataFormat.endianness     = SL_BYTEORDER_LITTLEENDIAN;
        dataFormat.representation = SL_ANDROID_PCM_REPRESENTATION_FLOAT;
    }

    static void prepareCallbackBuffer (AudioBuffer<float>& audioBuffer, float* native)
    {
        if (audioBuffer.getNumChannels() == 1)
            audioBuffer.setDataToReferTo (&native, 1, audioBuffer.getNumSamples());
    }

    using LittleEndianFloat32 = AudioData::Format<AudioData::Float32, AudioData::LittleEndian>;
    using NativeFloat32       = AudioData::Format<AudioData::Float32, AudioData::NativeEndian>;

    static void convertFromOpenSL (const float* srcInterleaved, AudioBuffer<float>& audioBuffer)
    {
        const auto numChannels = audioBuffer.getNumChannels();

        if (numChannels == 1)
        {
            jassert (srcInterleaved == audioBuffer.getWritePointer (0));
            return;
        }

        AudioData::deinterleaveSamples (AudioData::InterleavedSource<LittleEndianFloat32> { srcInterleaved,                        numChannels },
                                        AudioData::NonInterleavedDest<NativeFloat32>      { audioBuffer.getArrayOfWritePointers(), numChannels },
                                        audioBuffer.getNumSamples());
    }

    static void convertToOpenSL (const AudioBuffer<float>& audioBuffer, float* dstInterleaved)
    {
        const auto numChannels = audioBuffer.getNumChannels();

        if (numChannels == 1)
        {
            jassert (dstInterleaved == audioBuffer.getReadPointer (0));
            return;
        }

        AudioData::interleaveSamples (AudioData::NonInterleavedSource<NativeFloat32>  { audioBuffer.getArrayOfReadPointers(), numChannels },
                                      AudioData::InterleavedDest<LittleEndianFloat32> { dstInterleaved,                       numChannels },
                                      audioBuffer.getNumSamples());
    }
};

//==============================================================================
using CreateEngineFunc = SLresult (*) (SLObjectItf*, SLuint32, const SLEngineOption*,
                                       SLuint32, const SLInterfaceID*, const SLboolean*);

struct OpenSLEngineHolder
{
    OpenSLEngineHolder()
    {
        if (auto createEngine = (CreateEngineFunc) slLibrary.getFunction ("slCreateEngine"))
        {
            SLObjectItf obj = nullptr;
            auto err = createEngine (&obj, 0, nullptr, 0, nullptr, nullptr);

            if (err != SL_RESULT_SUCCESS || obj == nullptr || *obj == nullptr
                || (*obj)->Realize (obj, 0) != SL_RESULT_SUCCESS)
            {
                destroyObject (obj);
            }

            engine = SlRef<SLEngineItf_>::cast (SlObjectRef (obj));
        }
    }

    DynamicLibrary slLibrary { "libOpenSLES.so" };
    SlRef<SLEngineItf_> engine;
};

OpenSLEngineHolder& getEngineHolder()
{
    static OpenSLEngineHolder holder;
    return holder;
}

//==============================================================================
class SLRealtimeThread;

//==============================================================================
class OpenSLAudioIODevice final : public AudioIODevice
{
public:
    //==============================================================================
    template <typename T>
    class OpenSLSessionT;

    //==============================================================================
    // CRTP
    template <typename T, class Child, typename RunnerObjectType>
    struct OpenSLQueueRunner
    {
        OpenSLQueueRunner (OpenSLSessionT<T>& sessionToUse, int numChannelsToUse)
            : owner (sessionToUse),
              numChannels (numChannelsToUse),
              nativeBuffer (static_cast<size_t> (numChannels * owner.bufferSize * owner.numBuffers)),
              scratchBuffer (numChannelsToUse, owner.bufferSize),
              sampleBuffer (scratchBuffer.getArrayOfWritePointers(), numChannelsToUse, owner.bufferSize)
        {}

        ~OpenSLQueueRunner()
        {
            if (config != nullptr && javaProxy != nullptr)
            {
                javaProxy.clear();
                (*config)->ReleaseJavaProxy (config, /*SL_ANDROID_JAVA_PROXY_ROUTING*/1);
            }
        }

        bool init()
        {
            runner = crtp().createPlayerOrRecorder();

            if (runner == nullptr)
                return false;

            const bool supportsJavaProxy = (getAndroidSDKVersion() >= 24);

            if (supportsJavaProxy)
            {
                // may return nullptr on some platforms - that's ok
                config = SlRef<SLAndroidConfigurationItf_>::cast (runner);

                if (config != nullptr)
                {
                    jobject audioRoutingJni;
                    auto status = (*config)->AcquireJavaProxy (config, /*SL_ANDROID_JAVA_PROXY_ROUTING*/1,
                                                               &audioRoutingJni);

                    if (status == SL_RESULT_SUCCESS && audioRoutingJni != nullptr)
                        javaProxy = GlobalRef (LocalRef<jobject> (getEnv()->NewLocalRef (audioRoutingJni)));
                }
            }

            queue = SlRef<SLAndroidSimpleBufferQueueItf_>::cast (runner);

            if (queue == nullptr)
                return false;

            return ((*queue)->RegisterCallback (queue, staticFinished, this) == SL_RESULT_SUCCESS);
        }

        void clear()
        {
            nextBlock.set (0);
            numBlocksOut.set (0);

            zeromem (nativeBuffer.get(), static_cast<size_t> (owner.bufferSize * numChannels * owner.numBuffers) * sizeof (T));
            scratchBuffer.clear();
            (*queue)->Clear (queue);
        }

        void enqueueBuffer()
        {
            (*queue)->Enqueue (queue, getCurrentBuffer(), static_cast<SLuint32> (getBufferSizeInSamples() * sizeof (T)));
            ++numBlocksOut;
        }

        bool isBufferAvailable() const         { return (numBlocksOut.get() < owner.numBuffers); }
        T* getNextBuffer()                     { nextBlock.set ((nextBlock.get() + 1) % owner.numBuffers); return getCurrentBuffer(); }
        T* getCurrentBuffer()                  { return nativeBuffer.get() + (static_cast<size_t> (nextBlock.get()) * getBufferSizeInSamples()); }
        size_t getBufferSizeInSamples() const  { return static_cast<size_t> (owner.bufferSize * numChannels); }

        void finished (SLAndroidSimpleBufferQueueItf)
        {
            --numBlocksOut;
            owner.doSomeWorkOnAudioThread();
        }

        static void staticFinished (SLAndroidSimpleBufferQueueItf caller, void *pContext)
        {
            reinterpret_cast<OpenSLQueueRunner*> (pContext)->finished (caller);
        }

        // get the "this" pointer for CRTP
        Child&       crtp()       { return * ((Child*) this); }
        const Child& crtp() const { return * ((Child*) this); }

        OpenSLSessionT<T>& owner;

        SlRef<RunnerObjectType> runner;
        SlRef<SLAndroidSimpleBufferQueueItf_> queue;
        SlRef<SLAndroidConfigurationItf_> config;
        GlobalRef javaProxy;

        int numChannels;

        HeapBlock<T> nativeBuffer;
        AudioBuffer<float> scratchBuffer, sampleBuffer;

        Atomic<int> nextBlock { 0 }, numBlocksOut { 0 };
    };

    //==============================================================================
    template <typename T>
    struct OpenSLQueueRunnerPlayer final : OpenSLQueueRunner<T, OpenSLQueueRunnerPlayer<T>, SLPlayItf_>
    {
        using Base = OpenSLQueueRunner<T, OpenSLQueueRunnerPlayer<T>, SLPlayItf_>;

        OpenSLQueueRunnerPlayer (OpenSLSessionT<T>& sessionToUse, int numChannelsToUse)
            : Base (sessionToUse, numChannelsToUse)
        {}

        SlRef<SLPlayItf_> createPlayerOrRecorder()
        {
            SLDataLocator_AndroidSimpleBufferQueue queueLocator = { SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, static_cast<SLuint32> (Base::owner.numBuffers) };
            SLDataLocator_OutputMix outputMix = { SL_DATALOCATOR_OUTPUTMIX, Base::owner.outputMix };

            PCMDataFormatEx dataFormat;
            BufferHelpers<T>::initPCMDataFormat (dataFormat, Base::numChannels, Base::owner.sampleRate);

            SLDataSource source = { &queueLocator, &dataFormat };
            SLDataSink   sink   = { &outputMix,    nullptr };

            SLInterfaceID queueInterfaces[] = { &IntfIID<SLAndroidSimpleBufferQueueItf_>::iid, &IntfIID<SLAndroidConfigurationItf_>::iid };
            SLboolean interfaceRequired[] = {SL_BOOLEAN_TRUE, SL_BOOLEAN_FALSE};

            SLObjectItf obj = nullptr;

            auto& holder = getEngineHolder();

            if (auto e = *holder.engine)
            {
                auto status = e->CreateAudioPlayer (holder.engine, &obj, &source, &sink, 2,
                                                    queueInterfaces, interfaceRequired);

                if (status != SL_RESULT_SUCCESS || obj == nullptr || (*obj)->Realize (obj, 0) != SL_RESULT_SUCCESS)
                {
                    destroyObject (obj);
                    return {};
                }
            }

            return SlRef<SLPlayItf_>::cast (SlObjectRef (obj));
        }

        void setState (bool running)    { (*Base::runner)->SetPlayState (Base::runner, running ? SL_PLAYSTATE_PLAYING : SL_PLAYSTATE_STOPPED); }
    };

    template <typename T>
    struct OpenSLQueueRunnerRecorder final : public OpenSLQueueRunner<T, OpenSLQueueRunnerRecorder<T>, SLRecordItf_>
    {
        using Base = OpenSLQueueRunner<T, OpenSLQueueRunnerRecorder<T>, SLRecordItf_>;

        OpenSLQueueRunnerRecorder (OpenSLSessionT<T>& sessionToUse, int numChannelsToUse)
            : Base (sessionToUse, numChannelsToUse)
        {}

        SlRef<SLRecordItf_> createPlayerOrRecorder()
        {
            SLDataLocator_IODevice ioDeviceLocator = { SL_DATALOCATOR_IODEVICE, SL_IODEVICE_AUDIOINPUT, SL_DEFAULTDEVICEID_AUDIOINPUT, nullptr };
            SLDataLocator_AndroidSimpleBufferQueue queueLocator = { SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, static_cast<SLuint32> (Base::owner.numBuffers) };

            PCMDataFormatEx dataFormat;
            BufferHelpers<T>::initPCMDataFormat (dataFormat, Base::numChannels, Base::owner.sampleRate);

            SLDataSource source = { &ioDeviceLocator, nullptr };
            SLDataSink   sink   = { &queueLocator,    &dataFormat };

            SLInterfaceID queueInterfaces[] = { &IntfIID<SLAndroidSimpleBufferQueueItf_>::iid, &IntfIID<SLAndroidConfigurationItf_>::iid };
            SLboolean interfaceRequired[] = { SL_BOOLEAN_TRUE, SL_BOOLEAN_FALSE };

            SLObjectItf obj = nullptr;

            auto& holder = getEngineHolder();

            if (auto e = *holder.engine)
            {
                auto status = e->CreateAudioRecorder (holder.engine, &obj, &source, &sink, 2, queueInterfaces, interfaceRequired);

                if (status != SL_RESULT_SUCCESS || obj == nullptr || (*obj)->Realize (obj, 0) != SL_RESULT_SUCCESS)
                {
                    destroyObject (obj);
                    return {};
                }
            }

            return SlRef<SLRecordItf_>::cast (SlObjectRef (obj));
        }

        bool setAudioPreprocessingEnabled (bool shouldEnable)
        {
            if (Base::config != nullptr)
            {
                const bool supportsUnprocessed = (getAndroidSDKVersion() >= 25);
                const SLuint32 recordingPresetValue
                    = (shouldEnable ? SL_ANDROID_RECORDING_PRESET_GENERIC
                                    : (supportsUnprocessed ? SL_ANDROID_RECORDING_PRESET_UNPROCESSED
                                                           : SL_ANDROID_RECORDING_PRESET_VOICE_RECOGNITION));

                auto status = (*Base::config)->SetConfiguration (Base::config, SL_ANDROID_KEY_RECORDING_PRESET,
                                                                 &recordingPresetValue, sizeof (recordingPresetValue));

                return (status == SL_RESULT_SUCCESS);
            }

            return false;
        }

        void setState (bool running)    { (*Base::runner)->SetRecordState (Base::runner, running ? SL_RECORDSTATE_RECORDING
                                                                                                 : SL_RECORDSTATE_STOPPED); }
    };

    //==============================================================================
    class OpenSLSession
    {
    public:
        OpenSLSession (int numInputChannels, int numOutputChannels,
                       double samleRateToUse, int bufferSizeToUse,
                       int numBuffersToUse)
            : inputChannels (numInputChannels), outputChannels (numOutputChannels),
              sampleRate (samleRateToUse), bufferSize (bufferSizeToUse), numBuffers (numBuffersToUse)
        {
            jassert (numInputChannels > 0 || numOutputChannels > 0);

            if (outputChannels > 0)
            {
                auto& holder = getEngineHolder();
                SLObjectItf obj = nullptr;

                auto err = (*holder.engine)->CreateOutputMix (holder.engine, &obj, 0, nullptr, nullptr);

                if (err != SL_RESULT_SUCCESS || obj == nullptr || *obj == nullptr
                     || (*obj)->Realize (obj, 0) != SL_RESULT_SUCCESS)
                {
                    destroyObject (obj);
                    return;
                }

                outputMix = SlRef<SLOutputMixItf_>::cast (SlObjectRef (obj));
            }
        }

        virtual ~OpenSLSession() {}

        virtual bool openedOK() const    { return (outputChannels == 0 || outputMix != nullptr); }
        virtual void start()             { stop(); jassert (callback.get() != nullptr); running = true; }
        virtual void stop()              { running = false; }

        virtual bool setAudioPreprocessingEnabled (bool shouldEnable) = 0;
        virtual bool supportsFloatingPoint() const noexcept = 0;
        virtual int getXRunCount() const noexcept = 0;

        void setCallback (AudioIODeviceCallback* callbackToUse)
        {
            if (! running)
            {
                callback.set (callbackToUse);
                return;
            }

            // don't set callback to null! stop the playback instead!
            jassert (callbackToUse != nullptr);

            // spin-lock until we can set the callback
            for (;;)
            {
                auto old = callback.get();

                if (old == callbackToUse)
                    break;

                if (callback.compareAndSetBool (callbackToUse, old))
                    break;

                Thread::sleep (1);
            }
        }

        void process (const float* const* inputChannelData, float* const* outputChannelData)
        {
            if (auto* cb = callback.exchange (nullptr))
            {
                cb->audioDeviceIOCallbackWithContext (inputChannelData, inputChannels, outputChannelData, outputChannels, bufferSize, {});
                callback.set (cb);
            }
            else
            {
                for (int i = 0; i < outputChannels; ++i)
                    zeromem (outputChannelData[i], sizeof (float) * static_cast<size_t> (bufferSize));
            }
        }

        static OpenSLSession* create (int numInputChannels, int numOutputChannels,
                                      double samleRateToUse, int bufferSizeToUse,
                                      int numBuffersToUse);

        //==============================================================================
        int inputChannels, outputChannels;
        double sampleRate;
        int bufferSize, numBuffers;
        bool running = false, audioProcessingEnabled = true;

        SlRef<SLOutputMixItf_> outputMix;

        Atomic<AudioIODeviceCallback*> callback { nullptr };
    };

    template <typename T>
    class OpenSLSessionT final : public OpenSLSession
    {
    public:
        OpenSLSessionT (int numInputChannels, int numOutputChannels,
                        double samleRateToUse, int bufferSizeToUse,
                        int numBuffersToUse)
            : OpenSLSession (numInputChannels, numOutputChannels,
                             samleRateToUse, bufferSizeToUse, numBuffersToUse)
        {
            jassert (numInputChannels > 0 || numOutputChannels > 0);

            if (OpenSLSession::openedOK())
            {
                if (inputChannels > 0)
                {
                    recorder.reset (new OpenSLQueueRunnerRecorder<T> (*this, inputChannels));

                    if (! recorder->init())
                    {
                        recorder = nullptr;
                        return;
                    }
                }

                if (outputChannels > 0)
                {
                    player.reset (new OpenSLQueueRunnerPlayer<T> (*this, outputChannels));

                    if (! player->init())
                    {
                        player = nullptr;
                        return;
                    }

                    const bool supportsUnderrunCount = (getAndroidSDKVersion() >= 24);
                    getUnderrunCount = supportsUnderrunCount ? getEnv()->GetMethodID (AudioTrack, "getUnderrunCount", "()I") : nullptr;
                }
            }
        }

        bool openedOK() const override
        {
            return OpenSLSession::openedOK() && (inputChannels == 0  || recorder != nullptr)
                                             && (outputChannels == 0 || player   != nullptr);
        }

        void start() override
        {
            OpenSLSession::start();

            guard.set (0);

            if (inputChannels > 0)
                recorder->clear();

            if (outputChannels > 0)
                player->clear();

            // first enqueue all buffers
            for (int i = 0; i < numBuffers; ++i)
                doSomeWorkOnAudioThread();

            if (inputChannels > 0)
                recorder->setState (true);

            if (outputChannels > 0)
                player->setState (true);
        }

        void stop() override
        {
            OpenSLSession::stop();

            while (! guard.compareAndSetBool (1, 0))
                Thread::sleep (1);

            if (inputChannels > 0)
                recorder->setState (false);

            if (outputChannels > 0)
                player->setState (false);

            guard.set (0);
        }

        bool setAudioPreprocessingEnabled (bool shouldEnable) override
        {
            if (shouldEnable != audioProcessingEnabled)
            {
                audioProcessingEnabled = shouldEnable;

                if (recorder != nullptr)
                    return recorder->setAudioPreprocessingEnabled (audioProcessingEnabled);
            }

            return true;
        }

        int getXRunCount() const noexcept override
        {
            if (player != nullptr && player->javaProxy != nullptr && getUnderrunCount != nullptr)
                return getEnv()->CallIntMethod (player->javaProxy, getUnderrunCount);

            return -1;
        }

        bool supportsFloatingPoint() const noexcept override          { return (BufferHelpers<T>::isFloatingPoint != 0); }

        void doSomeWorkOnAudioThread()
        {
            // only the player or the recorder should enter this section at any time
            if (guard.compareAndSetBool (1, 0))
            {
                // are there enough buffers available to process some audio
                if ((inputChannels == 0 || recorder->isBufferAvailable()) && (outputChannels == 0 || player->isBufferAvailable()))
                {
                    T* recorderBuffer = (inputChannels  > 0 ? recorder->getNextBuffer() : nullptr);
                    T* playerBuffer   = (outputChannels > 0 ? player->getNextBuffer()   : nullptr);

                    const float* const* inputChannelData = nullptr;
                    float* const* outputChannelData = nullptr;

                    if (recorderBuffer != nullptr)
                    {
                        BufferHelpers<T>::prepareCallbackBuffer (recorder->sampleBuffer, recorderBuffer);
                        BufferHelpers<T>::convertFromOpenSL (recorderBuffer, recorder->sampleBuffer);

                        inputChannelData = recorder->sampleBuffer.getArrayOfReadPointers();
                    }

                    if (playerBuffer != nullptr)
                    {
                        BufferHelpers<T>::prepareCallbackBuffer (player->sampleBuffer, playerBuffer);
                        outputChannelData = player->sampleBuffer.getArrayOfWritePointers();
                    }

                    process (inputChannelData, outputChannelData);

                    if (recorderBuffer != nullptr)
                        recorder->enqueueBuffer();

                    if (playerBuffer != nullptr)
                    {
                        BufferHelpers<T>::convertToOpenSL (player->sampleBuffer, playerBuffer);
                        player->enqueueBuffer();
                    }
                }

                guard.set (0);
            }
        }

        //==============================================================================
        std::unique_ptr<OpenSLQueueRunnerPlayer<T>> player;
        std::unique_ptr<OpenSLQueueRunnerRecorder<T>> recorder;
        Atomic<int> guard;
        jmethodID getUnderrunCount = nullptr;
    };

    //==============================================================================
    OpenSLAudioIODevice (const String& deviceName)  : AudioIODevice (deviceName, openSLTypeName)
    {
        // OpenSL has piss-poor support for determining latency, so the only way I can find to
        // get a number for this is by asking the AudioTrack/AudioRecord classes..
        AndroidAudioIODevice javaDevice (deviceName);

        // this is a total guess about how to calculate the latency, but seems to vaguely agree
        // with the devices I've tested.. YMMV
        inputLatency  = (javaDevice.minBufferSizeIn  * 2) / 3;
        outputLatency = (javaDevice.minBufferSizeOut * 2) / 3;

        const int64 longestLatency = jmax (inputLatency, outputLatency);
        const int64 totalLatency = inputLatency + outputLatency;
        inputLatency  = (int) ((longestLatency * inputLatency)  / totalLatency) & ~15;
        outputLatency = (int) ((longestLatency * outputLatency) / totalLatency) & ~15;

        // You can only create this class if you are sure that your hardware supports OpenSL
        jassert (getEngineHolder().slLibrary.getNativeHandle() != nullptr);
    }

    ~OpenSLAudioIODevice() override
    {
        close();
    }

    bool openedOk() const       { return session != nullptr; }

    StringArray getOutputChannelNames() override
    {
        StringArray s;
        s.add ("Left");
        s.add ("Right");
        return s;
    }

    StringArray getInputChannelNames() override
    {
        StringArray s;
        s.add ("Audio Input");
        return s;
    }

    Array<double> getAvailableSampleRates() override
    {
        // see https://developer.android.com/ndk/guides/audio/opensl-for-android.html

        static const double rates[] = { 8000.0, 11025.0, 12000.0, 16000.0,
                                        22050.0, 24000.0, 32000.0, 44100.0, 48000.0 };

        Array<double> retval (rates, numElementsInArray (rates));

        // make sure the native sample rate is part of the list
        double native = AndroidHighPerformanceAudioHelpers::getNativeSampleRate();

        if (native != 0.0 && ! retval.contains (native))
            retval.add (native);

        return retval;
    }

    Array<int> getAvailableBufferSizes() override
    {
        return AndroidHighPerformanceAudioHelpers::getAvailableBufferSizes (AndroidHighPerformanceAudioHelpers::getNativeBufferSizeHint(),
                                                                            getAvailableSampleRates());
    }

    String open (const BigInteger& inputChannels,
                 const BigInteger& outputChannels,
                 double requestedSampleRate,
                 int bufferSize) override
    {
        close();

        lastError.clear();

        sampleRate = (int) (requestedSampleRate > 0 ? requestedSampleRate : AndroidHighPerformanceAudioHelpers::getNativeSampleRate());
        auto preferredBufferSize = (bufferSize > 0) ? bufferSize : getDefaultBufferSize();

        audioBuffersToEnqueue = [this, preferredBufferSize]
        {
            using namespace AndroidHighPerformanceAudioHelpers;

            auto nativeBufferSize = getNativeBufferSizeHint();

            if (canUseHighPerformanceAudioPath (nativeBufferSize, preferredBufferSize, sampleRate))
                return preferredBufferSize / nativeBufferSize;


            return 1;
        }();

        actualBufferSize = preferredBufferSize / audioBuffersToEnqueue;

        jassert ((actualBufferSize * audioBuffersToEnqueue) == preferredBufferSize);

        activeOutputChans = outputChannels;
        activeOutputChans.setRange (2, activeOutputChans.getHighestBit(), false);
        auto numOutputChannels = activeOutputChans.countNumberOfSetBits();

        activeInputChans = inputChannels;
        activeInputChans.setRange (1, activeInputChans.getHighestBit(), false);
        auto numInputChannels = activeInputChans.countNumberOfSetBits();

        if (numInputChannels > 0 && (! RuntimePermissions::isGranted (RuntimePermissions::recordAudio)))
        {
            // If you hit this assert, you probably forgot to get RuntimePermissions::recordAudio
            // before trying to open an audio input device. This is not going to work!
            jassertfalse;
            lastError = "Error opening OpenSL input device: the app was not granted android.permission.RECORD_AUDIO";
        }

        session.reset (OpenSLSession::create (numInputChannels, numOutputChannels,
                                              sampleRate, actualBufferSize, audioBuffersToEnqueue));
        if (session != nullptr)
        {
            session->setAudioPreprocessingEnabled (audioProcessingEnabled);
        }
        else
        {
            if (numInputChannels > 0 && numOutputChannels > 0 && RuntimePermissions::isGranted (RuntimePermissions::recordAudio))
            {
                // New versions of the Android emulator do not seem to support audio input anymore on OS X
                activeInputChans = BigInteger (0);
                numInputChannels = 0;

                session.reset (OpenSLSession::create (numInputChannels, numOutputChannels,
                                                      sampleRate, actualBufferSize, audioBuffersToEnqueue));
            }
        }

        DBG ("OpenSL: numInputChannels = " << numInputChannels
             << ", numOutputChannels = " << numOutputChannels
             << ", nativeBufferSize = " << AndroidHighPerformanceAudioHelpers::getNativeBufferSizeHint()
             << ", nativeSampleRate = " << AndroidHighPerformanceAudioHelpers::getNativeSampleRate()
             << ", actualBufferSize = " << actualBufferSize
             << ", audioBuffersToEnqueue = " << audioBuffersToEnqueue
             << ", sampleRate = " << sampleRate
             << ", supportsFloatingPoint = " << (session != nullptr && session->supportsFloatingPoint() ? "true" : "false"));

        if (session == nullptr)
            lastError = "Unknown error initializing opensl session";

        deviceOpen = (session != nullptr);
        return lastError;
    }

    void close() override
    {
        stop();
        session = nullptr;
        callback = nullptr;
    }

    int getOutputLatencyInSamples() override            { return outputLatency; }
    int getInputLatencyInSamples() override             { return inputLatency; }
    bool isOpen() override                              { return deviceOpen; }
    int getCurrentBufferSizeSamples() override          { return actualBufferSize * audioBuffersToEnqueue; }
    int getCurrentBitDepth() override                   { return (session != nullptr && session->supportsFloatingPoint() ? 32 : 16); }
    BigInteger getActiveOutputChannels() const override { return activeOutputChans; }
    BigInteger getActiveInputChannels() const override  { return activeInputChans; }
    String getLastError() override                      { return lastError; }
    bool isPlaying() override                           { return callback != nullptr; }
    int getXRunCount() const noexcept override          { return (session != nullptr ? session->getXRunCount() : -1); }

    int getDefaultBufferSize() override
    {
        return AndroidHighPerformanceAudioHelpers::getDefaultBufferSize (AndroidHighPerformanceAudioHelpers::getNativeBufferSizeHint(),
                                                                         getCurrentSampleRate());
    }

    double getCurrentSampleRate() override
    {
        return (sampleRate == 0.0 ? AndroidHighPerformanceAudioHelpers::getNativeSampleRate() : sampleRate);
    }

    void start (AudioIODeviceCallback* newCallback) override
    {
        if (session != nullptr && callback != newCallback)
        {
            auto oldCallback = callback;

            if (newCallback != nullptr)
                newCallback->audioDeviceAboutToStart (this);

            if (oldCallback != nullptr)
            {
                // already running
                if (newCallback == nullptr)
                    stop();
                else
                    session->setCallback (newCallback);

                oldCallback->audioDeviceStopped();
            }
            else
            {
                jassert (newCallback != nullptr);

                // session hasn't started yet
                session->setCallback (newCallback);
                session->start();
            }

            callback = newCallback;
        }
    }

    void stop() override
    {
        if (session != nullptr && callback != nullptr)
        {
            callback = nullptr;
            session->stop();
            session->setCallback (nullptr);
        }
    }

    bool setAudioPreprocessingEnabled (bool shouldAudioProcessingBeEnabled) override
    {
        audioProcessingEnabled = shouldAudioProcessingBeEnabled;

        if (session != nullptr)
            session->setAudioPreprocessingEnabled (audioProcessingEnabled);

        return true;
    }

    static const char* const openSLTypeName;

private:
    //==============================================================================
    friend class SLRealtimeThread;

    //==============================================================================
    int actualBufferSize = 0, sampleRate = 0, audioBuffersToEnqueue = 0;
    int inputLatency, outputLatency;
    bool deviceOpen = false, audioProcessingEnabled = true;
    String lastError;
    BigInteger activeOutputChans, activeInputChans;
    AudioIODeviceCallback* callback = nullptr;

    std::unique_ptr<OpenSLSession> session;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (OpenSLAudioIODevice)
};

OpenSLAudioIODevice::OpenSLSession* OpenSLAudioIODevice::OpenSLSession::create (int numInputChannels, int numOutputChannels,
                                                                                double samleRateToUse, int bufferSizeToUse,
                                                                                int numBuffersToUse)
{
    std::unique_ptr<OpenSLSession> retval;
    auto sdkVersion = getAndroidSDKVersion();

    // SDK versions 21 and higher should natively support floating point...
    if (sdkVersion >= 21)
    {
        retval.reset (new OpenSLSessionT<float> (numInputChannels, numOutputChannels, samleRateToUse,
                                                 bufferSizeToUse, numBuffersToUse));

        // ...however, some devices lie so re-try without floating point
        if (retval != nullptr && (! retval->openedOK()))
            retval = nullptr;
    }

    if (retval == nullptr)
    {
        retval.reset (new OpenSLSessionT<int16> (numInputChannels, numOutputChannels, samleRateToUse,
                                                 bufferSizeToUse, numBuffersToUse));

        if (retval != nullptr && (! retval->openedOK()))
            retval = nullptr;
    }

    return retval.release();
}

//==============================================================================
class OpenSLAudioDeviceType final : public AudioIODeviceType
{
public:
    OpenSLAudioDeviceType()  : AudioIODeviceType (OpenSLAudioIODevice::openSLTypeName) {}

    //==============================================================================
    void scanForDevices() override {}

    StringArray getDeviceNames (bool) const override                             { return StringArray (OpenSLAudioIODevice::openSLTypeName); }
    int getDefaultDeviceIndex (bool) const override                              { return 0; }
    int getIndexOfDevice (AudioIODevice* device, bool) const override            { return device != nullptr ? 0 : -1; }
    bool hasSeparateInputsAndOutputs() const override                            { return false; }

    AudioIODevice* createDevice (const String& outputDeviceName,
                                 const String& inputDeviceName) override
    {
        std::unique_ptr<OpenSLAudioIODevice> dev;

        if (outputDeviceName.isNotEmpty() || inputDeviceName.isNotEmpty())
            dev.reset (new OpenSLAudioIODevice (outputDeviceName.isNotEmpty() ? outputDeviceName
                                                                              : inputDeviceName));

        return dev.release();
    }

    static bool isOpenSLAvailable()
    {
        DynamicLibrary library;
        return library.open ("libOpenSLES.so");
    }

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (OpenSLAudioDeviceType)
};

const char* const OpenSLAudioIODevice::openSLTypeName = "Android OpenSL";


//==============================================================================
bool isOpenSLAvailable()  { return OpenSLAudioDeviceType::isOpenSLAvailable(); }

//==============================================================================
class SLRealtimeThread
{
public:
    static constexpr int numBuffers = 4;

    SLRealtimeThread()
    {
        if (auto createEngine = (CreateEngineFunc) slLibrary.getFunction ("slCreateEngine"))
        {
            SLObjectItf obj = nullptr;
            auto err = createEngine (&obj, 0, nullptr, 0, nullptr, nullptr);

            if (err != SL_RESULT_SUCCESS || obj == nullptr || *obj == nullptr)
                return;

            if ((*obj)->Realize (obj, 0) != SL_RESULT_SUCCESS)
            {
                destroyObject (obj);
                return;
            }

            engine = SlRef<SLEngineItf_>::cast (SlObjectRef (obj));

            if (engine == nullptr)
            {
                destroyObject (obj);
                return;
            }

            obj = nullptr;
            err = (*engine)->CreateOutputMix (engine, &obj, 0, nullptr, nullptr);

            if (err != SL_RESULT_SUCCESS || obj == nullptr || (*obj)->Realize (obj, 0) != SL_RESULT_SUCCESS)
            {
                destroyObject (obj);
                return;
            }

            outputMix = SlRef<SLOutputMixItf_>::cast (SlObjectRef (obj));

            if (outputMix == nullptr)
            {
                destroyObject (obj);
                return;
            }

            SLDataLocator_AndroidSimpleBufferQueue queueLocator = {SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, static_cast<SLuint32> (numBuffers)};
            SLDataLocator_OutputMix outputMixLocator = {SL_DATALOCATOR_OUTPUTMIX, outputMix};

            PCMDataFormatEx dataFormat;
            BufferHelpers<int16>::initPCMDataFormat (dataFormat, 1, AndroidHighPerformanceAudioHelpers::getNativeSampleRate());

            SLDataSource source = { &queueLocator, &dataFormat };
            SLDataSink   sink   = { &outputMixLocator, nullptr };

            SLInterfaceID queueInterfaces[] = { &IntfIID<SLAndroidSimpleBufferQueueItf_>::iid };
            SLboolean trueFlag = SL_BOOLEAN_TRUE;

            obj = nullptr;
            err = (*engine)->CreateAudioPlayer (engine, &obj, &source, &sink, 1, queueInterfaces, &trueFlag);

            if (err != SL_RESULT_SUCCESS || obj == nullptr)
                return;

            if ((*obj)->Realize (obj, 0) != SL_RESULT_SUCCESS)
            {
                destroyObject (obj);
                return;
            }

            player = SlRef<SLPlayItf_>::cast (SlObjectRef (obj));

            if (player == nullptr)
            {
                destroyObject (obj);
                return;
            }

            queue = SlRef<SLAndroidSimpleBufferQueueItf_>::cast (player);
            if (queue == nullptr)
                return;

            if ((*queue)->RegisterCallback (queue, staticFinished, this) != SL_RESULT_SUCCESS)
            {
                queue = nullptr;
                return;
            }

            pthread_cond_init (&threadReady, nullptr);
            pthread_mutex_init (&threadReadyMutex, nullptr);
        }
    }

    bool isOk() const      { return queue != nullptr; }

    pthread_t startThread (void* (*entry) (void*), void* userPtr)
    {
        memset (buffer.get(), 0, static_cast<size_t> (sizeof (int16) * static_cast<size_t> (bufferSize * numBuffers)));

        for (int i = 0; i < numBuffers; ++i)
        {
            int16* dst = buffer.get() + (bufferSize * i);
            (*queue)->Enqueue (queue, dst, static_cast<SLuint32> (static_cast<size_t> (bufferSize) * sizeof (int16)));
        }

        pthread_mutex_lock (&threadReadyMutex);

        threadEntryProc = entry;
        threadUserPtr  = userPtr;

        (*player)->SetPlayState (player, SL_PLAYSTATE_PLAYING);

        pthread_cond_wait (&threadReady, &threadReadyMutex);
        pthread_mutex_unlock (&threadReadyMutex);

        return threadID;
    }

    void finished()
    {
        if (threadEntryProc != nullptr)
        {
            pthread_mutex_lock (&threadReadyMutex);

            threadID = pthread_self();

            pthread_cond_signal (&threadReady);
            pthread_mutex_unlock (&threadReadyMutex);

            threadEntryProc (threadUserPtr);
            threadEntryProc = nullptr;

            (*player)->SetPlayState (player, SL_PLAYSTATE_STOPPED);
            MessageManager::callAsync ([this]() { delete this; });
        }
    }

private:
    //==============================================================================
    static void staticFinished (SLAndroidSimpleBufferQueueItf, void* context)
    {
        static_cast<SLRealtimeThread*> (context)->finished();
    }

    //==============================================================================
    DynamicLibrary slLibrary { "libOpenSLES.so" };

    SlRef<SLEngineItf_>    engine;
    SlRef<SLOutputMixItf_> outputMix;
    SlRef<SLPlayItf_>      player;
    SlRef<SLAndroidSimpleBufferQueueItf_> queue;

    int bufferSize = AndroidHighPerformanceAudioHelpers::getNativeBufferSizeHint();
    HeapBlock<int16> buffer { HeapBlock<int16> (static_cast<size_t> (1 * bufferSize * numBuffers)) };

    void* (*threadEntryProc) (void*) = nullptr;
    void* threadUserPtr              = nullptr;

    pthread_cond_t  threadReady;
    pthread_mutex_t threadReadyMutex;
    pthread_t       threadID;
};

//==============================================================================
RealtimeThreadFactory getAndroidRealtimeThreadFactory()
{
    return [] (void* (*entry) (void*), void* userPtr) -> pthread_t
    {
        auto thread = std::make_unique<SLRealtimeThread>();

        if (! thread->isOk())
            return {};

        auto threadID = thread->startThread (entry, userPtr);

        // the thread will de-allocate itself
        thread.release();

        return threadID;
    };
}

} // namespace juce
