<?php
  
  namespace Guzzle\Batch;
  
  use Guzzle\Batch\BatchTransferInterface;
  use Guzzle\Batch\BatchDivisorInterface;
  use Guzzle\Common\Exception\InvalidArgumentException;
  use Guzzle\Service\Command\CommandInterface;
  use Guzzle\Service\Exception\InconsistentClientTransferException;
  
  /**
   * Efficiently transfers multiple commands in parallel per client
   * This class is to be used with {@see Guzzle\Batch\BatchInterface}
   */
  class BatchCommandTransfer implements BatchTransferInterface, BatchDivisorInterface
  {
      /** @var int Size of each command batch */
      protected $batchSize;
  
      /**
       * @param int $batchSize Size of each batch
       */
      public function __construct($batchSize = 50)
      {
          $this->batchSize = $batchSize;
      }
  
      /**
       * Creates batches by grouping commands by their associated client
       * {@inheritdoc}
       */
      public function createBatches(\SplQueue $queue)
      {
          $groups = new \SplObjectStorage();
          foreach ($queue as $item) {
              if (!$item instanceof CommandInterface) {
                  throw new InvalidArgumentException('All items must implement Guzzle\Service\Command\CommandInterface');
              }
              $client = $item->getClient();
              if (!$groups->contains($client)) {
                  $groups->attach($client, new \ArrayObject(array($item)));
              } else {
                  $groups[$client]->append($item);
              }
          }
  
          $batches = array();
          foreach ($groups as $batch) {
              $batches = array_merge($batches, array_chunk($groups[$batch]->getArrayCopy(), $this->batchSize));
          }
  
          return $batches;
      }
  
      public function transfer(array $batch)
      {
          if (empty($batch)) {
              return;
          }
  
          // Get the client of the first found command
          $client = reset($batch)->getClient();
  
          // Keep a list of all commands with invalid clients
          $invalid = array_filter($batch, function ($command) use ($client) {
              return $command->getClient() !== $client;
          });
  
          if (!empty($invalid)) {
              throw new InconsistentClientTransferException($invalid);
          }
  
          $client->execute($batch);
      }
  }