public function setAuthConfig($config)
  {
    if (is_string($config)) {
      if (!file_exists($config)) {
        throw new InvalidArgumentException(sprintf('file "%s" does not exist', $config));
      }

      $json = file_get_contents($config);

      if (!$config = json_decode($json, true)) {
        throw new LogicException('invalid json for auth config');
      }
    }

    $key = isset($config['installed']) ? 'installed' : 'web';
    if (isset($config['type']) && $config['type'] == 'service_account') {
      // application default credentials
      $this->useApplicationDefaultCredentials();

      // set the information from the config
      $this->setClientId($config['client_id']);
      $this->config['client_email'] = $config['client_email'];
      $this->config['signing_key'] = $config['private_key'];
      $this->config['signing_algorithm'] = 'HS256';
    } elseif (isset($config[$key])) {
      // old-style
      $this->setClientId($config[$key]['client_id']);
      $this->setClientSecret($config[$key]['client_secret']);
      if (isset($config[$key]['redirect_uris'])) {
        $this->setRedirectUri($config[$key]['redirect_uris'][0]);
      }
    } else {
      // new-style
      $this->setClientId($config['client_id']);
      $this->setClientSecret($config['client_secret']);
      if (isset($config['redirect_uris'])) {
        $this->setRedirectUri($config['redirect_uris'][0]);
      }
    }
  }