#include <iostream>
#include <cstdio>
#include <cstdint>
#include <thread>
#include <chrono>

#if defined _WIN32
#include <al.h>
#include <alc.h>
#include <io.h>
#include <fcntl.h>
#else
#include <AL/al.h>
#include <AL/alc.h>
#endif

#pragma comment(lib, "libs/Win64/OpenAL32.lib")

#if 0 || defined _DEBUG
#define AL_CHECK_ERROR(msg) (checkALError(msg))
#else
#define AL_CHECK_ERROR(msg)
#endif

const uint8_t numBuf = 3;
const ALsizei bufSize = 1000;
const ALenum format = AL_FORMAT_MONO8;
const ALsizei freq = 8000;
char readBuf[bufSize]; 

void checkALError(const char * msg)
{
    while (ALuint err = alGetError() != AL_NO_ERROR)
        std::cerr << "Caught AL Error at " << msg << ": " << err << "\n";
}

ALsizei fillBufferFromStdin(ALuint buf)
{
    // read
    const ALsizei bytesRead = (ALsizei) fread(readBuf, sizeof(uint8_t), bufSize, stdin);
    // copy to OpenAL buffer
    alBufferData(buf, format, (void *) readBuf, bytesRead, freq);
    AL_CHECK_ERROR("buffer data");
    return bytesRead;
}

void updateBuffers(ALuint src, ALuint bufs[numBuf])
{
    ALint srcState;
    do
    {
        // wait until a buffer is free
        ALint val = 0;
        do 
        {
            alGetSourcei(src, AL_BUFFERS_PROCESSED, &val);
            AL_CHECK_ERROR("get num processed");
            if (val > 0) break;
            // sleep for a quarter of the duration a buffer plays
            std::this_thread::sleep_for(std::chrono::milliseconds((bufSize / freq) * 1000 / 4));
        } while (true);
        while (val--)
        {
            // remove oldest buffer from queue and get its id
            ALuint buf;
            alSourceUnqueueBuffers(src, 1, &buf);
            AL_CHECK_ERROR("unqueue buffer");
            // fill buffer
            const ALsizei bytesRead = fillBufferFromStdin(buf);
            // add buffer to queue
            alSourceQueueBuffers(src, 1, &buf);
            AL_CHECK_ERROR("queue buffer");
            // if end of stdin was reached, return
            if (bytesRead < bufSize) return;
        }
        // check if source is still playing
        alGetSourcei(src, AL_SOURCE_STATE, &srcState);
    } while (AL_PLAYING == srcState);
}

int main(int argc, char * argv[])
{
    // set stdin to binary mode
#ifdef _WIN32
    _setmode(_fileno(stdin), _O_BINARY);
#else
    freopen(nullptr, "rb", stdin);
#endif

    // initialization: open default device
    ALCdevice * dev = alcOpenDevice(nullptr);
    // reset error state
    AL_CHECK_ERROR("open device");
    // create a context
    ALCcontext * context = alcCreateContext(dev, nullptr);
    AL_CHECK_ERROR("create context");
    alcMakeContextCurrent(context);
    AL_CHECK_ERROR("activate context");
    // create buffers for audio streaming
    ALuint bufs[numBuf];
    alGenBuffers(numBuf, bufs);
    AL_CHECK_ERROR("create buffer");
    // create source to play buffer
    ALuint src;
    alGenSources(1, &src);
    AL_CHECK_ERROR("create source");

    // initially fill buffers
    for (uint8_t i = 0; i < numBuf; ++i) fillBufferFromStdin(bufs[i]);
    alSourceQueueBuffers(src, numBuf, bufs);
    AL_CHECK_ERROR("queue buffer");
    // play source
    alSourcePlay(src);
    AL_CHECK_ERROR("play");
    // fill buffers in loop
    updateBuffers(src, bufs);
    // when stream is read completely, wait until source stops playing
    ALint srcState;
    do
    {
        alGetSourcei(src, AL_SOURCE_STATE, &srcState);
        std::this_thread::sleep_for(std::chrono::milliseconds(10));
    } while (AL_PLAYING == srcState);


    // delete source
    alDeleteSources(1, &src);
    AL_CHECK_ERROR("delete source");
    // delete buffers
    alDeleteBuffers(numBuf, bufs);
    AL_CHECK_ERROR("delete buffer");
    // destroy context
    alcDestroyContext(context);
    AL_CHECK_ERROR("destroy context");
    // close device
    alcCloseDevice(dev);
    AL_CHECK_ERROR("close device");

    std::cout << "Exiting\n";
    return 0;
}