class Extension

class Extension {

  /**
   * The type of the extension (e.g., 'module').
   *
   * @var string
   */
  protected $type;

  /**
   * The relative pathname of the extension (e.g., 'core/modules/node/node.info.yml').
   *
   * @var string
   */
  protected $pathname;

  /**
   * The filename of the main extension file (e.g., 'node.module').
   *
   * @var string|null
   */
  protected $filename;

  /**
   * An SplFileInfo instance for the extension's info file.
   *
   * Note that SplFileInfo is a PHP resource and resources cannot be serialized.
   *
   * @var \SplFileInfo
   */
  protected $splFileInfo;

  /**
   * The app root.
   *
   * @var string
   */
  protected $root;

  /**
   * Constructs a new Extension object.
   *
   * @param string $root
   *   The app root.
   * @param string $type
   *   The type of the extension; e.g., 'module'.
   * @param string $pathname
   *   The relative path and filename of the extension's info file; e.g.,
   *   'core/modules/node/node.info.yml'.
   * @param string $filename
   *   (optional) The filename of the main extension file; e.g., 'node.module'.
   */
  public function __construct($root, $type, $pathname, $filename = NULL) {

    // @see \Drupal\Core\Theme\ThemeInitialization::getActiveThemeByName()
    assert($pathname === 'core/core.info.yml' || $pathname[0] !== '/' && file_exists($root . '/' . $pathname), sprintf('The file specified by the given app root, relative path and file name (%s) do not exist.', $root . '/' . $pathname));
    $this->root = $root;
    $this->type = $type;
    $this->pathname = $pathname;
    $this->filename = $filename;
  }

  /**
   * Returns the type of the extension.
   *
   * @return string
   */
  public function getType() {
    return $this->type;
  }

  /**
   * Returns the internal name of the extension.
   *
   * @return string
   */
  public function getName() {
    return basename($this->pathname, '.info.yml');
  }

  /**
   * Returns the relative path of the extension.
   *
   * @return string
   */
  public function getPath() {
    return dirname($this->pathname);
  }

  /**
   * Returns the relative path and filename of the extension's info file.
   *
   * @return string
   */
  public function getPathname() {
    return $this->pathname;
  }

  /**
   * Returns the filename of the extension's info file.
   *
   * @return string
   */
  public function getFilename() {
    return basename($this->pathname);
  }

  /**
   * Returns the relative path of the main extension file, if any.
   *
   * @return string|null
   */
  public function getExtensionPathname() {
    if ($this->filename) {
      return $this
        ->getPath() . '/' . $this->filename;
    }
  }

  /**
   * Returns the name of the main extension file, if any.
   *
   * @return string|null
   */
  public function getExtensionFilename() {
    return $this->filename;
  }

  /**
   * Loads the main extension file, if any.
   *
   * @return bool
   *   TRUE if this extension has a main extension file, FALSE otherwise.
   */
  public function load() {
    if ($this->filename) {
      include_once $this->root . '/' . $this
        ->getPath() . '/' . $this->filename;
      return TRUE;
    }
    return FALSE;
  }

  /**
   * Re-routes method calls to SplFileInfo.
   *
   * Offers all SplFileInfo methods to consumers; e.g., $extension->getMTime().
   */
  public function __call($method, array $args) {
    if (!isset($this->splFileInfo)) {
      $this->splFileInfo = new \SplFileInfo($this->root . '/' . $this->pathname);
    }
    return call_user_func_array([
      $this->splFileInfo,
      $method,
    ], $args);
  }

  /**
   * Magic method implementation to serialize the extension object.
   *
   * @return array
   *   The names of all variables that should be serialized.
   */
  public function __sleep() {

    // @todo \Drupal\Core\Extension\ThemeExtensionList is adding custom
    //   properties to the Extension object.
    $properties = get_object_vars($this);

    // Don't serialize the app root, since this could change if the install is
    // moved. Don't serialize splFileInfo because it can not be.
    unset($properties['splFileInfo'], $properties['root']);
    return array_keys($properties);
  }

  /**
   * Magic method implementation to unserialize the extension object.
   */
  public function __wakeup() {

    // Get the app root from the container.
    $this->root = \Drupal::hasService('app.root') ? \Drupal::root() : DRUPAL_ROOT;
  }

}