// if s1 starts with s2 returns true, else false
// len is the length of s1
// s2 should be null-terminated
static bool starts_with(const char *s1, int len, const char *s2)
{
  int n = 0;
  while (*s2 && n < len) {
    if (*s1++ != *s2++)
      return false;
    n++;
  }
  return *s2 == 0;
}

// convert escape sequence to event, and return consumed bytes on success (failure == 0)
static int parse_escape_seq(struct tb_event *event, const char *buf, int len)
{
  if (len >= 6 && starts_with(buf, len, "\033[M")) {

    switch (buf[3] & 3) {
    case 0:
      if (buf[3] == 0x60)
        event->key = TB_KEY_MOUSE_WHEEL_UP;
      else
        event->key = TB_KEY_MOUSE_LEFT;
      break;
    case 1:
      if (buf[3] == 0x61)
        event->key = TB_KEY_MOUSE_WHEEL_DOWN;
      else
        event->key = TB_KEY_MOUSE_MIDDLE;
      break;
    case 2:
      event->key = TB_KEY_MOUSE_RIGHT;
      break;
    case 3:
      event->key = TB_KEY_MOUSE_RELEASE;
      break;
    default:
      return -6;
    }
    event->type = TB_EVENT_MOUSE; // TB_EVENT_KEY by default

    // the coord is 1,1 for upper left
    event->x = (uint8_t)buf[4] - 1 - 32;
    event->y = (uint8_t)buf[5] - 1 - 32;

    return 6;
  }

  // it's pretty simple here, find 'starts_with' match and return
  // success, else return failure
  int i;
  for (i = 0; keys[i]; i++) {
    if (starts_with(buf, len, keys[i])) {
      event->ch = 0;
      event->key = 0xFFFF-i;
      return strlen(keys[i]);
    }
  }
  return 0;
}

static bool extract_event(struct tb_event *event, struct bytebuffer *inbuf)
{
  const char *buf = inbuf->buf;
  const int len = inbuf->len;
  if (len == 0)
    return false;

  if (buf[0] == '\033') {
    int n = parse_escape_seq(event, buf, len);
    if (n != 0) {
      bool success = true;
      if (n < 0) {
        success = false;
        n = -n;
      }
      bytebuffer_truncate(inbuf, n);
      return success;
    } else {
      // it's not escape sequence; assume it's esc
      event->ch = 0;
      event->key = TB_KEY_ESC;
      bytebuffer_truncate(inbuf, 1);
      return true;
    }
  }

  // if we're here, this is not an escape sequence and not an alt sequence
  // so, it's a FUNCTIONAL KEY or a UNICODE character

  // first of all check if it's a functional key
  if ((unsigned char)buf[0] <= TB_KEY_SPACE ||
      (unsigned char)buf[0] == TB_KEY_BACKSPACE2)
  {
    // fill event, pop buffer, return success */
    event->ch = 0;
    event->key = (uint16_t)buf[0];
    bytebuffer_truncate(inbuf, 1);
    return true;
  }

  // feh... we got utf8 here

  // check if there is all bytes
  if (len >= tb_utf8_char_length(buf[0])) {
    /* everything ok, fill event, pop buffer, return success */
    tb_utf8_char_to_unicode(&event->ch, buf);
    event->key = 0;
    bytebuffer_truncate(inbuf, tb_utf8_char_length(buf[0]));
    return true;
  }

  // event isn't recognized, perhaps there is not enough bytes in utf8
  // sequence
  return false;
}