class StaticLayout

class StaticLayout extends PluginBase implements LayoutInterface {

  /**
   * Overrides Drupal\Component\Plugin\PluginBase::__construct().
   */
  public function __construct(array $configuration, $plugin_id, DiscoveryInterface $discovery) {

    // Get definition by discovering the declarative information.
    $definition = $discovery
      ->getDefinition($plugin_id);
    foreach ($definition['regions'] as $region => $title) {
      if (!isset($configuration['regions'][$region])) {
        $configuration['regions'][$region] = array();
      }
    }
    parent::__construct($configuration, $plugin_id, $discovery);
  }

  /**
   * Implements Drupal\layout\Plugin\LayoutInterface::getRegions().
   */
  public function getRegions() {
    $definition = $this
      ->getDefinition();
    return $definition['regions'];
  }

  /**
   * Returns the list of CSS files associated with this layout.
   */
  public function getStylesheetFiles() {
    $definition = $this
      ->getDefinition();
    return isset($definition['stylesheets']) ? $definition['stylesheets'] : array();
  }

  /**
   * Returns the list of administrative CSS files associated with this layout.
   */
  public function getAdminStylesheetFiles() {
    $definition = $this
      ->getDefinition();

    // Fall back on regular CSS for the admin page if admin CSS not provided.
    return isset($definition['admin stylesheets']) ? $definition['admin stylesheets'] : $this
      ->getStylesheetFiles();
  }

  /**
   * Returns the list of JS files associated with this layout.
   */
  public function getScriptFiles() {
    $definition = $this
      ->getDefinition();
    return isset($definition['scripts']) ? $definition['scripts'] : array();
  }

  /**
   * Returns the list of administrative JS files associated with this layout.
   */
  public function getAdminScriptFiles() {
    $definition = $this
      ->getDefinition();
    return isset($definition['admin scripts']) ? $definition['admin scripts'] : $this
      ->getScriptFiles();
  }

  /**
   * Implements Drupal\layout\Plugin\LayoutInterface::renderLayout().
   */
  public function renderLayout($admin = FALSE, $regions = array()) {
    $definition = $this
      ->getDefinition();

    // Assemble a render array with the regions and attached CSS/JS.
    $build = array(
      '#theme' => $definition['theme'],
      '#content' => array(),
    );

    // Render all regions needed for this layout.
    foreach ($this
      ->getRegions() as $region => $info) {

      // Initialize regions which were not provided as empty.
      $build['#content'][$region] = empty($regions[$region]) ? '' : $regions[$region];
    }

    // Fill in attached CSS and JS files based on metadata.
    if (!$admin) {
      $build['#attached'] = array(
        'css' => $this
          ->getStylesheetFiles(),
        'js' => $this
          ->getScriptFiles(),
      );
    }
    else {
      $build['#attached'] = array(
        'css' => $this
          ->getAdminStylesheetFiles(),
        'js' => $this
          ->getAdminScriptFiles(),
      );
    }

    // Include the path of the definition in all CSS and JS files.
    foreach (array(
      'css',
      'js',
    ) as $type) {
      foreach ($build['#attached'][$type] as &$filename) {
        $filename = $definition['path'] . '/' . $filename;
      }
    }
    return drupal_render($build);
  }

}