class Memory

class Memory implements QueueInterface {
  
  /**
   * The queue data.
   *
   * @var array
   */
  protected $queue;
  
  /**
   * Counter for item ids.
   *
   * @var int
   */
  protected $idSequence;
  
  /**
   * Constructs a Memory object.
   *
   * @param string $name
   *   An arbitrary string. The name of the queue to work with.
   */
  public function __construct($name) {
    $this->queue = [];
    $this->idSequence = 0;
  }
  
  /**
   * {@inheritdoc}
   */
  public function createItem($data) {
    $item = new \stdClass();
    $item->item_id = $this->idSequence++;
    $item->data = $data;
    $item->created = \Drupal::time()->getCurrentTime();
    $item->expire = 0;
    $this->queue[$item->item_id] = $item;
    return $item->item_id;
  }
  
  /**
   * {@inheritdoc}
   */
  public function numberOfItems() {
    return count($this->queue);
  }
  
  /**
   * {@inheritdoc}
   */
  public function claimItem($lease_time = 30) {
    foreach ($this->queue as $key => $item) {
      if ($item->expire == 0) {
        $item->expire = \Drupal::time()->getCurrentTime() + $lease_time;
        $this->queue[$key] = $item;
        return $item;
      }
    }
    return FALSE;
  }
  
  /**
   * {@inheritdoc}
   */
  public function deleteItem($item) {
    unset($this->queue[$item->item_id]);
  }
  
  /**
   * {@inheritdoc}
   */
  public function releaseItem($item) {
    if (isset($this->queue[$item->item_id]) && $this->queue[$item->item_id]->expire != 0) {
      $this->queue[$item->item_id]->expire = 0;
      return TRUE;
    }
    return FALSE;
  }
  
  /**
   * {@inheritdoc}
   */
  public function createQueue() {
    // Nothing needed here.
  }
  
  /**
   * {@inheritdoc}
   */
  public function deleteQueue() {
    $this->queue = [];
    $this->idSequence = 0;
  }

}