<?php
  
  namespace Guzzle\Batch;
  
  use Guzzle\Batch\BatchTransferInterface;
  use Guzzle\Batch\BatchDivisorInterface;
  use Guzzle\Common\Exception\InvalidArgumentException;
  use Guzzle\Http\Message\RequestInterface;
  
  /**
   * Batch transfer strategy used to efficiently transfer a batch of requests.
   * This class is to be used with {@see Guzzle\Batch\BatchInterface}
   */
  class BatchRequestTransfer implements BatchTransferInterface, BatchDivisorInterface
  {
      /** @var int Size of each command batch */
      protected $batchSize;
  
      /**
       * Constructor used to specify how large each batch should be
       *
       * @param int $batchSize Size of each batch
       */
      public function __construct($batchSize = 50)
      {
          $this->batchSize = $batchSize;
      }
  
      /**
       * Creates batches of requests by grouping requests by their associated curl multi object.
       * {@inheritdoc}
       */
      public function createBatches(\SplQueue $queue)
      {
          // Create batches by client objects
          $groups = new \SplObjectStorage();
          foreach ($queue as $item) {
              if (!$item instanceof RequestInterface) {
                  throw new InvalidArgumentException('All items must implement Guzzle\Http\Message\RequestInterface');
              }
              $client = $item->getClient();
              if (!$groups->contains($client)) {
                  $groups->attach($client, array($item));
              } else {
                  $current = $groups[$client];
                  $current[] = $item;
                  $groups[$client] = $current;
              }
          }
  
          $batches = array();
          foreach ($groups as $batch) {
              $batches = array_merge($batches, array_chunk($groups[$batch], $this->batchSize));
          }
  
          return $batches;
      }
  
      public function transfer(array $batch)
      {
          if ($batch) {
              reset($batch)->getClient()->send($batch);
          }
      }
  }