abstract class FileCache

abstract class FileCache extends CacheProvider {

  /**
   * @var string Cache directory.
   */
  protected $directory;

  /**
   * @var string Cache file extension.
   */
  protected $extension;

  /**
   * Constructor
   *
   * @param string $directory Cache directory.
   * @param string $directory Cache file extension.
   *
   * @throws \InvalidArgumentException
   */
  public function __construct($directory, $extension = null) {
    if (!is_dir($directory) && !@mkdir($directory, 0777, true)) {
      throw new \InvalidArgumentException(sprintf('The directory "%s" does not exist and could not be created.', $directory));
    }
    if (!is_writable($directory)) {
      throw new \InvalidArgumentException(sprintf('The directory "%s" is not writable.', $directory));
    }
    $this->directory = realpath($directory);
    $this->extension = $extension ?: $this->extension;
  }

  /**
   * Gets the cache directory.
   *
   * @return string
   */
  public function getDirectory() {
    return $this->directory;
  }

  /**
   * Gets the cache file extension.
   *
   * @return string
   */
  public function getExtension() {
    return $this->extension;
  }

  /**
   * @return string
   */
  protected function getFilename($id) {
    $path = implode(str_split(md5($id), 12), DIRECTORY_SEPARATOR);
    $path = $this->directory . DIRECTORY_SEPARATOR . $path;
    return $path . DIRECTORY_SEPARATOR . $id . $this->extension;
  }

  /**
   * {@inheritdoc}
   */
  protected function doDelete($id) {
    return unlink($this
      ->getFilename($id));
  }

  /**
   * {@inheritdoc}
   */
  protected function doFlush() {
    $pattern = '/^.+\\' . $this->extension . '$/i';
    $iterator = new \RecursiveDirectoryIterator($this->directory);
    $iterator = new \RecursiveIteratorIterator($iterator);
    $iterator = new \RegexIterator($iterator, $pattern);
    foreach ($iterator as $name => $file) {
      unlink($name);
    }
    return true;
  }

  /**
   * {@inheritdoc}
   */
  protected function doGetStats() {
    return null;
  }

}