/*
 * oggdec.c - decodifica um Ogg Vorbis para WAV PCM 16 bits estereo (para o build do TerraTactician Expandoria recomprimir a
 * musica com o wav2ogg de ../pygame-music). Usa o vorbisfile do libvorbis 1.3.7.
 * Copyright (C) 2026 FredyGames. GNU GPL versao 2 ou posterior (como o wav2ogg).
 *
 *   oggdec entrada.ogg saida.wav
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <vorbis/vorbisfile.h>

static void put32(unsigned char *p, unsigned v) { p[0] = v; p[1] = v >> 8; p[2] = v >> 16; p[3] = v >> 24; }

int main(int argc, char **argv) {
  if (argc != 3) { fprintf(stderr, "uso: oggdec entrada.ogg saida.wav\n"); return 2; }
  FILE *in = fopen(argv[1], "rb");
  if (!in) { perror(argv[1]); return 1; }
  OggVorbis_File vf;
  if (ov_open_callbacks(in, &vf, NULL, 0, OV_CALLBACKS_NOCLOSE) < 0) { fprintf(stderr, "nao e Ogg Vorbis\n"); return 1; }
  vorbis_info *vi = ov_info(&vf, -1);
  if (vi->channels != 2) { fprintf(stderr, "precisa de estereo\n"); return 1; }
  unsigned rate = vi->rate;
  size_t cap = 1 << 20, len = 0;
  unsigned char *pcm = malloc(cap);
  char buf[4096];
  int bitstream;
  for (;;) {
    long n = ov_read(&vf, buf, sizeof buf, 0, 2, 1, &bitstream);
    if (n == 0) break;
    if (n < 0) continue;
    if (len + n > cap) { cap *= 2; pcm = realloc(pcm, cap); }
    memcpy(pcm + len, buf, n);
    len += n;
  }
  ov_clear(&vf);
  fclose(in);
  FILE *out = fopen(argv[2], "wb");
  unsigned char h[44] = "RIFF\0\0\0\0WAVEfmt \x10\0\0\0\x01\0\x02\0\0\0\0\0\0\0\0\0\x04\0\x10\0data\0\0\0\0";
  put32(h + 4, 36 + len);
  put32(h + 24, rate);
  put32(h + 28, rate * 4);
  put32(h + 40, len);
  fwrite(h, 1, 44, out);
  fwrite(pcm, 1, len, out);
  fclose(out);
  return 0;
}