class CachedFormulaLoader

class CachedFormulaLoader implements FormulaLoaderInterface {
  private $loader;
  private $configCache;
  private $debug;

  /**
   * Constructor.
   *
   * When the loader is in debug mode it will ensure the cached formulae
   * are fresh before returning them.
   *
   * @param FormulaLoaderInterface $loader      A formula loader
   * @param ConfigCache            $configCache A config cache
   * @param Boolean                $debug       The debug mode
   */
  public function __construct(FormulaLoaderInterface $loader, ConfigCache $configCache, $debug = false) {
    $this->loader = $loader;
    $this->configCache = $configCache;
    $this->debug = $debug;
  }
  public function load(ResourceInterface $resources) {
    if (!$resources instanceof IteratorResourceInterface) {
      $resources = array(
        $resources,
      );
    }
    $formulae = array();
    foreach ($resources as $resource) {
      $id = (string) $resource;
      if (!$this->configCache
        ->has($id) || $this->debug && !$resource
        ->isFresh($this->configCache
        ->getTimestamp($id))) {
        $formulae += $this->loader
          ->load($resource);
        $this->configCache
          ->set($id, $formulae);
      }
      else {
        $formulae += $this->configCache
          ->get($id);
      }
    }
    return $formulae;
  }

}