#define _BSD_SOURCE
#include <endian.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

typedef struct WAV_hdr
{
  uint32_t chunk_id;
  uint32_t chunk_size;
  uint32_t format;

  uint32_t subchunk1_id;
  uint32_t subchunk1_size;
  uint16_t audio_format;
  uint16_t num_channels;
  uint32_t sample_rate;
  uint32_t byte_rate;
  uint16_t block_align;
  uint16_t bits_per_sample;

  uint32_t subchunk2_id;
  uint32_t subchunk2_size;
} WAV_hdr_t;


static int usage(const char *progname)
{
  fprintf(stderr, "usage: %s [-f outfile]\n, where:", progname);
  fprintf(stderr, "\t-f outfile: file to write audio to in WAV format.\n");
  exit(1);
}


int main(int argc, char **argv)
{
  mode_t mode = S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP;
  int fd;
  const char *outfile = "/tmp/audio.wav";
  int outfd;
  uint8_t buf[8192];
  WAV_hdr_t hdr;
  ssize_t len, totlen=0;
  int num_no_data = -1;
  int c;

  memset(buf, 0, sizeof(buf));
  memset(&hdr, 0, sizeof(hdr));

  while ((c = getopt(argc, argv, "f:")) != -1) {
    switch (c) {
      case 'f':
        outfile = optarg;
        break;
      default:
        usage(argv[0]);
        break;
    }
  }

  if ((fd = open("/tmp/rcu_audio_pcm", O_RDONLY)) < 0) {
    perror("open /tmp/rcu_audio_pcm");
    exit(1);
  }

  if ((outfd = open(outfile, O_RDWR|O_CREAT|O_TRUNC, mode)) < 0) {
    fprintf(stderr, "Unable to open %s for writing.\n", outfile);
    exit(1);
  }

  if ((len = write(outfd, &hdr, sizeof(WAV_hdr_t))) != sizeof(WAV_hdr_t)) {
    fprintf(stderr, "Incorrect size for WAV header: %zd != %zd\n",
      len, sizeof(WAV_hdr_t));
    exit(1);
  }

  while (1) {
    len = read(fd, buf, sizeof(buf));
    if (len > 0) {
      totlen += len;
      if (write(outfd, buf, len) != len) {
        fprintf(stderr, "short write!\n");
        exit(1);
      }
      num_no_data = 0;
    } else if (len < 0) {
      perror("read");
      exit(1);
    } else if (len == 0) {
      if (num_no_data >= 5) {
        break;
      }
      sleep(1);
      if (num_no_data >= 0) {
        num_no_data++;
      }
    }
  }

  lseek(outfd, 0, SEEK_SET);

  #define BITS_PER_SAMPLE 16
  #define SAMPLES_PER_SECOND  16000
  /* http://soundfile.sapp.org/doc/WaveFormat/ */
  hdr.chunk_id = htole32(0x46464952);  // "RIFF"
  hdr.chunk_size = htole32(36 + totlen);
  hdr.format = htole32(0x45564157);  // "WAVE"

  hdr.subchunk1_id = htole32(0x20746d66);  // "fmt "
  hdr.subchunk1_size = htole32(16);
  hdr.audio_format = htole16(1);
  hdr.num_channels = htole16(1);
  hdr.sample_rate = htole32(SAMPLES_PER_SECOND);
  hdr.byte_rate = htole32(SAMPLES_PER_SECOND * 1 * BITS_PER_SAMPLE/8);
  hdr.block_align = htole16(1 * BITS_PER_SAMPLE/8);
  hdr.bits_per_sample = htole16(BITS_PER_SAMPLE);

  hdr.subchunk2_id = htole32(0x61746164);  // "data"
  hdr.subchunk2_size = htole32(totlen);
  if ((len = write(outfd, &hdr, sizeof(WAV_hdr_t))) != sizeof(WAV_hdr_t)) {
    fprintf(stderr, "Incorrect size for WAV header: %zd != %zd\n",
      len, sizeof(WAV_hdr_t));
    exit(1);
  }

  exit(0);
}