<?php
  
  /*
   * This file is part of the Assetic package, an OpenSky project.
   *
   * (c) 2010-2014 OpenSky Project Inc
   *
   * For the full copyright and license information, please view the LICENSE
   * file that was distributed with this source code.
   */
  
  namespace Assetic\Extension\Twig;
  
  use Assetic\ValueSupplierInterface;
  
  /**
   * Container for values initialized lazily from a ValueSupplierInterface.
   *
   * @author Christophe Coevoet <stof@notk.org>
   */
  class ValueContainer implements \ArrayAccess, \IteratorAggregate, \Countable
  {
      private $values;
      private $valueSupplier;
  
      public function __construct(ValueSupplierInterface $valueSupplier)
      {
          $this->valueSupplier = $valueSupplier;
      }
  
      public function offsetExists($offset)
      {
          $this->initialize();
  
          return array_key_exists($offset, $this->values);
      }
  
      public function offsetGet($offset)
      {
          $this->initialize();
  
          if (!array_key_exists($offset, $this->values)) {
              throw new \OutOfRangeException(sprintf('The variable "%s" does not exist.', $offset));
          }
  
          return $this->values[$offset];
      }
  
      public function offsetSet($offset, $value)
      {
          throw new \BadMethodCallException('The ValueContainer is read-only.');
      }
  
      public function offsetUnset($offset)
      {
          throw new \BadMethodCallException('The ValueContainer is read-only.');
      }
  
      public function getIterator()
      {
          $this->initialize();
  
          return new \ArrayIterator($this->values);
      }
  
      public function count()
      {
          $this->initialize();
  
          return count($this->values);
      }
  
      private function initialize()
      {
          if (null === $this->values) {
              $this->values = $this->valueSupplier->getValues();
          }
      }
  }