class TwigFactory

class TwigFactory {

  /**
   * Returns a fully initialized Twig_Environment object.
   *
   * This constructs and configures a Twig_Environment. It also adds Drupal
   * specific Twig_NodeVisitors, filters and functions.
   *
   * To retrieve the system wide Twig_Environment object you should use:
   * @code
   *   $twig = drupal_container()->get('twig');
   * @endcode
   * This will retrieve the Twig_Environment object from the DIC.
   *
   * @return Twig_Environment
   *   The fully initialized Twig_Environment object.
   *
   * @see twig_render
   * @see TwigNodeVisitor
   * @see TwigReference
   * @see TwigReferenceFunction
   */
  public static function get() {

    // @todo Maybe we will have our own loader later.
    $loader = new \Twig_Loader_Filesystem(DRUPAL_ROOT);
    $twig = new TwigEnvironment($loader, array(
      // This is saved / loaded via drupal_php_storage().
      // All files can be refreshed by clearing caches.
      // @todo ensure garbage collection of expired files.
      'cache' => TRUE,
      'base_template_class' => 'Drupal\\Core\\Template\\TwigTemplate',
      // @todo Remove in followup issue
      // @see http://drupal.org/node/1712444.
      'autoescape' => FALSE,
      // @todo Remove in followup issue
      // @see http://drupal.org/node/1806538.
      'strict_variables' => FALSE,
      // @todo Maybe make debug mode dependent on "production mode" setting.
      'debug' => TRUE,
      // @todo Make auto reload mode dependent on "production mode" setting.
      'auto_reload' => FALSE,
    ));

    // The node visitor is needed to wrap all variables with
    // render -> twig_render() function.
    $twig
      ->addNodeVisitor(new TwigNodeVisitor());
    $twig
      ->addTokenParser(new TwigFunctionTokenParser('hide'));
    $twig
      ->addTokenParser(new TwigFunctionTokenParser('show'));

    // @todo Figure out what to do about debugging functions.
    // @see http://drupal.org/node/1804998
    $twig
      ->addExtension(new \Twig_Extension_Debug());
    $reference_functions = array(
      'hide' => 'twig_hide',
      'render' => 'twig_render',
      'show' => 'twig_show',
    );
    $filters = array(
      't' => 't',
    );

    // These functions will receive a TwigReference object, if a render array is detected
    foreach ($reference_functions as $function => $php_function) {
      $twig
        ->addFunction($function, new TwigReferenceFunction($php_function));
    }
    foreach ($filters as $filter => $php_function) {
      $twig
        ->addFilter($filter, new \Twig_Filter_Function($php_function));
    }

    // @todo Remove URL function once http://drupal.org/node/1778610 is resolved.
    $twig
      ->addFunction('url', new \Twig_Function_Function('url'));
    return $twig;
  }

}