<?php
  
  namespace Guzzle\Batch;
  
  use Guzzle\Common\Exception\InvalidArgumentException;
  
  /**
   * BatchInterface decorator used to call a method each time flush is called
   */
  class NotifyingBatch extends AbstractBatchDecorator
  {
      /** @var mixed Callable to call */
      protected $callable;
  
      /**
       * @param BatchInterface $decoratedBatch Batch object to decorate
       * @param mixed          $callable       Callable to call
       *
       * @throws InvalidArgumentException
       */
      public function __construct(BatchInterface $decoratedBatch, $callable)
      {
          if (!is_callable($callable)) {
              throw new InvalidArgumentException('The passed argument is not callable');
          }
  
          $this->callable = $callable;
          parent::__construct($decoratedBatch);
      }
  
      public function flush()
      {
          $items = $this->decoratedBatch->flush();
          call_user_func($this->callable, $items);
  
          return $items;
      }
  }