#define PIPE_OUT 0
#define PIPE_IN 1

// based on https://github.com/tsoding/musializer/blob/master/src/ffmpeg_linux.c
typedef struct{
  int out_fd;
  pid_t pid;
} FFMPEG;

bool ffmpeg_start_screen_capture(
    FFMPEG* self,
    unsigned int pos_x,
    unsigned int pos_y,
    unsigned int res_x,
    unsigned int res_y
){
  int pipefd[2];
  if(pipe(pipefd) < 0){
    TraceLog(LOG_ERROR, "ffmpeg failed to init pipe");
    return false;
  }

  pid_t child = fork();
  if(child < 0){
    TraceLog(LOG_ERROR, "ffmpeg failed to fork()");
    return false;
  }

  if(child == 0){
    if(dup2(pipefd[PIPE_IN], STDOUT_FILENO) < 0){
      TraceLog(LOG_ERROR, "ffmpeg failed to bind parent pipe to child stdout");
      return false;
    }
    close(pipefd[PIPE_OUT]);

    // redirects ffmpeg logging
#if 1
    int null_fd = open("/dev/null", O_WRONLY);
    if(null_fd < 0){
      TraceLog(LOG_ERROR, "ffmpeg failed to open null pipe");
      return false;
    }
    if(dup2(null_fd, STDERR_FILENO) < 0){
      TraceLog(LOG_ERROR, "ffmpeg failed to bind null pipe to child stderr");
      return false;
    }
#endif

    char res_arg[128];
    snprintf(res_arg, sizeof(res_arg), "%ux%u", res_x, res_y);
    char scale_arg[256];
    int res = snprintf(scale_arg, sizeof(res_arg), "scale=%u:%u", res_x, res_y);
    assert(res > 10);
    char pos_arg[128];
    snprintf(pos_arg, sizeof(res_arg), ":0.0+%u,%u", pos_x, pos_y);

    fprintf(stderr, "scale_arg res: %d\n", res);
    fprintf(stderr, "scale_arg: %s\n", res_arg);
    int ret = execlp(
      "ffmpeg",
      "ffmpeg",
      "-video_size", "1920x1080",//res_arg,
      "-framerate", "30",
      "-f", "x11grab",
      "-i", pos_arg,
      "-f", "rawvideo",
      "-vf", scale_arg,
      "-pix_fmt","rgba",
      "-an",
      "-",
      NULL
    );
    if (ret < 0) {
      TraceLog(LOG_ERROR, "FFMPEG CHILD: could not run ffmpeg as a child process: %s", strerror(errno));
      exit(1);
    }
    assert(0 && "unreachable");
    exit(1);
  }

  self->pid = child;
  self->out_fd = pipefd[PIPE_OUT];
  return true;
}

void ffmpeg_read(FFMPEG* self, unsigned char* buffer, unsigned int res_x, unsigned int res_y){
  int frame_size = res_x * res_y * sizeof(Color);
  while(frame_size > 0){
    int res = read(self->out_fd, buffer, frame_size);
    if(res < 0){
      TraceLog(LOG_ERROR, "ffmpeg read error: %s", strerror(errno));
      exit(1);
    }
    frame_size-=res;
    buffer+=res;
  }
}

void ffmpeg_stop(FFMPEG* self){
  close(self->out_fd);
  kill(self->pid, SIGTERM);
  waitpid(self->pid, NULL, 0);
}