#include <stdio.h>
#include <windows.h>
#include <initguid.h>
#include <mmdeviceapi.h>
#include <audioclient.h>

/*
 * Compile with:
 * gcc -std=c11 -Wall -c foo.c -o foo.o
 * gcc foo.o -lgdi32 -lole32 -o foo
 *
 * Creates foo.exe
 */

int main()
{
  REFERENCE_TIME hnsRequestedDuration = 10000000;
  IMMDeviceEnumerator *dev_enum = NULL;
  IMMDevice *device = NULL;
  IAudioClient *client = NULL;
  WAVEFORMATEX *format = NULL;
  unsigned int frames = 0;

  CoInitialize(NULL);
  CoCreateInstance(&CLSID_MMDeviceEnumerator, NULL, CLSCTX_ALL,
                   &IID_IMMDeviceEnumerator, (void **)&dev_enum);
  if (!dev_enum)
  {
    fprintf(stderr, "Failed to get device enumerator.\n");
    fflush(stderr);
    return 1;
  }
  
  dev_enum->lpVtbl->GetDefaultAudioEndpoint(dev_enum, eRender, eConsole,
                                            &device);
  if (!device)
  {
    fprintf(stderr, "Failed to get device.\n");
    fflush(stderr);
    dev_enum->lpVtbl->Release(dev_enum);
    return 1;
  }

  device->lpVtbl->Activate(device, &IID_IAudioClient, CLSCTX_ALL, NULL,
                           (void **)&client);
  if (!client)
  {
    fprintf(stderr, "Failed to get client.\n");
    fflush(stderr);
    dev_enum->lpVtbl->Release(dev_enum);
    device->lpVtbl->Release(device);
    return 1;
  }

  client->lpVtbl->GetMixFormat(client, &format);
  if (!format)
  {
    fprintf(stderr, "Failed to get mix format.\n");
    fflush(stderr);
    dev_enum->lpVtbl->Release(dev_enum);
    device->lpVtbl->Release(device);
    client->lpVtbl->Release(client);
    return 1;
  }

  if (client->lpVtbl->Initialize(client, AUDCLNT_SHAREMODE_SHARED, 0,
                                 hnsRequestedDuration, 0, format, NULL) == S_OK)
  {
    WAVEFORMATEXTENSIBLE *ex = NULL;
    fprintf(stdout,
            "%s\n"
            "channels         : %u\n"
            "samples/sec      : %lu\n"
            "avg. bytes/sec   : %lu\n"
            "block align      : %u\n"
            "bits/sample      : %u\n",
            (format->wFormatTag == WAVE_FORMAT_EXTENSIBLE
             ? "Wave Format Extensible"
             : (format->wFormatTag == WAVE_FORMAT_MPEG
                ? "Mpeg1 Wave Format"
                : (format->wFormatTag == WAVE_FORMAT_MPEGLAYER3
                   ? "Mpeg Layer3 Wave Format"
                   : "Unknown format"))),
            format->nChannels,
            format->nSamplesPerSec,
            format->nAvgBytesPerSec,
            format->nBlockAlign,
            format->wBitsPerSample);
    switch(format->wFormatTag)
    {
    case WAVE_FORMAT_EXTENSIBLE:
      ex = (WAVEFORMATEXTENSIBLE *)format;
      fprintf(stdout,
              "valid bits/sample: %u\n"
              "samples/block    : %u\n",
              ex->Samples.wValidBitsPerSample,
              ex->Samples.wSamplesPerBlock);
      break;
    case WAVE_FORMAT_MPEG:
      break;
    case WAVE_FORMAT_MPEGLAYER3:
      break;
    default:
      break;
    }
  }
  else
  {
    fprintf(stderr, "Failed to initialize client.\n");
    fflush(stderr);
    dev_enum->lpVtbl->Release(dev_enum);
    device->lpVtbl->Release(device);
    client->lpVtbl->Release(client);
    return 1;
  }

  fprintf(stdout, "\n");
  if (client->lpVtbl->GetBufferSize(client, &frames) == S_OK)
    fprintf(stdout, "%u frames in buffer.\n", frames);
  else
    fprintf(stderr, "Failed to get buffer size.\n");

  if (client->lpVtbl->GetCurrentPadding(client, &frames) == S_OK)
    fprintf(stdout, "%u frames padding.\n", frames);
  else
    fprintf(stderr, "Failed to get padding.\n");
  
  fflush(stderr);
  fflush(stdout);

  dev_enum->lpVtbl->Release(dev_enum);
  device->lpVtbl->Release(device);
  client->lpVtbl->Release(client);
  
  return 0;
}