Integrating Dokuwiki with Drupal - possible?

OK, here's what I have so far (doesn't yet work).
drupal_ext.class.php:

<?php

class auth_drupal_ext extends auth_basic {
  var $url;
  var $db_prefix = '';
  var $session_id;

  function auth_drupal_ext() {
    global $conf;

    $this->cando['external'] = true;

    // Drupal is using ini_set in the $drupal_file
    $ini = ini_get("error_reporting");
    ini_set("error_reporting", 0);

    //now we can load the file without PHP complaining
    $drupal_file = $conf['auth']['drupal']['file'];
    include ($drupal_file);

    ini_set("error_reporting", $ini);

    //Following Drupal variables are interesting for us:
    //  $db_url, $db_prefix
//    $this->url = parse_url($db_url);
    $this->url = parse_url(is_array($db_url) ? $db_url['default'] : $db_url);
    $this->url['path'] = substr($this->url['path'], 1);
    $this->db_prefix = $db_prefix;

    //Decode url-encoded information in the db connection string
    $this->url['user'] = urldecode($this->url['user']);
    // Test if database url has a password.
    if(isset($this->url['pass'])) {
      $this->url['pass'] = urldecode($this->url['pass']);
    } else {
      $this->url['pass'] = '';
    }

    $this->url['host'] = urldecode($this->url['host']);
    $this->url['path'] = urldecode($this->url['path']);
    $this->session_id = ini_get('session.cookie_domain');
  }

  /**
    Strip the leading at-sign from role names.
   @param $role The original role name.
   @return string The role name without any preceding at-sign.
  */
  function _tg($role) {
    return preg_replace("/^@/", "", $role);
  }

  /**
   * Authenticate the user using Drupal session information.  User must login
   * via the Drupal interface; no login work is done here.
   *
   * @param   string  $user    Ignored.
   * @param   string  $pass    Ignored.
   * @param   bool    $sticky  Ignored.
   * @return bool             true on successful auth
   * @todo Drupal roles aren't recognized.  Only the super-user in Drupal has
   * Dokuwiki admin rights.
   */
  function trustExternal($user,$pass,$sticky=false) {
    global $conf;
    global $USERINFO;

    $logged_in = false;

    $link = mysql_connect($this->url['host'], $this->url['user'], $this->url['pass']);
    if (!$link) {
      msg('Could not connect: ' . mysql_error());
      return;
    }

    if (!mysql_select_db($this->url['path'], $link)) {
      msg('Cannot select the database: ' . mysql_error());
      mysql_close($link);
      return;
    }

    $query = 'SELECT u.uid,u.name,u.mail,s.hostname,s.timestamp FROM '.$this->db_prefix.
            'users u INNER JOIN '.$this->db_prefix.'sessions s ON u.uid=s.uid WHERE s.sid="'.
            $_COOKIE['PHPSESSID'].'" && u.status=1';

    $result = mysql_query($query);

    if ($result) {
      $tmp = mysql_fetch_row($result);
      if ($tmp) {
        $uid = $tmp[0];
        $USERINFO['name'] = $tmp[1];
        $USERINFO['mail'] = $tmp[2];
        $USERINFO['pass'] = '';

        $_SERVER['REMOTE_USER'] = $tmp[1];
        $_SESSION[DOKU_COOKIE]['auth']['user'] = $tmp[1];
        $_SESSION[DOKU_COOKIE]['auth']['buid'] = auth_browseruid();
        $_SESSION[DOKU_COOKIE]['auth']['info'] = $USERINFO;

        /* now for the roles */
        if ($uid == 1) {/* super user, everything's allowed */
          $USERINFO['grps'] = array($this->_tg($conf['superuser']), $this->_tg($conf['defaultgroup']));
        } else {
          $query = 'SELECT r.name FROM '.$this->db_prefix.'users_roles u INNER JOIN '.
                  $this->db_prefix.'role r WHERE u.uid='.$uid.' && u.rid=r.rid';
          $result = mysql_query($query);

          if ($result) {
            $tmp = mysql_fetch_row($result);
            if ($tmp) {
              $USERINFO['grps'] = array($tmp[0], $this->_tg($conf['defaultgroup']));
            }
          } else {
            msg('Error querying the database [' . mysql_error() . ']');
          }
        }

        $logged_in = true;
      }
    } else {
      msg('Error querying the database [' . mysql_error() . ']');
    }

    mysql_close($link);

    return $logged_in;
  }
}
?>

...and here's my addition to local.php:

$conf['useacl'] = 1;
$conf['authtype'] = 'drupal_ext';
$conf['passcrypt'] = 'md5';
$conf['superuser'] = '@wiki_admin';
$conf['userewrite'] = '1';
$conf['auth']['drupal']['file'] = '/file/system/path/to/settings.php';

...lastly, here's my additions to the default Dokuwiki .htaccess file:

# drupal integration additions
RewriteCond %{QUERY_STRING} \bdo=login\b [NC]
RewriteRule ^.* /user/login [L]

RewriteCond %{QUERY_STRING} \bdo=logout\b [NC]
RewriteRule ^.* /logout [L]

Can anyone see why all this isn't working?

OH! I should also mention that I serve Drupal out of /
and I server Dokuwiki out of /wiki

Thank you for all your time and consideration.

--chuck