AssetQueryString.php

<?php

declare (strict_types=1);
namespace Drupal\Core\Asset;

use Drupal\Component\Datetime\TimeInterface;
use Drupal\Core\State\StateInterface;

/**
 * Stores a cache busting query string service for asset URLs.
 *
 * The string changes on every update or full cache flush, forcing browsers to
 * load a new copy of the files, as the URL changed.
 */
class AssetQueryString implements AssetQueryStringInterface {
  
  /**
   * The key used for state.
   */
  const STATE_KEY = 'asset.css_js_query_string';
  
  /**
   * Creates a new AssetQueryString instance.
   *
   * @param \Drupal\Core\State\StateInterface $state
   *   State service.
   * @param \Drupal\Component\Datetime\TimeInterface $time
   *   System time service.
   */
  public function __construct(protected StateInterface $state, protected TimeInterface $time) {
  }
  
  /**
   * {@inheritdoc}
   */
  public function reset() : void {
    // The timestamp is converted to base 36 in order to make it more compact.
    $this->state
      ->set(self::STATE_KEY, base_convert(strval($this->time
      ->getRequestTime()), 10, 36));
  }
  
  /**
   * {@inheritdoc}
   */
  public function get() : string {
    return $this->state
      ->get(self::STATE_KEY, '0');
  }

}