/**
  * Determine if resource was NOT modified
  * since requester's last check
  *
  * For Concurrency Control (Lost Update Problem)
  * Uses `If-Match` and/or `If-Unmodified-Since`
  */
 public function wasNotModified(ResourceInterface $resource)
 {
     /*
      * Unlike If-None-Match, the spec on If-Match
      * does NOT say if If-Unmodified-Since
      * should be ignored if an ETag was given via
      * If-Match.
      *
      * We'll assume the same behaviour anyway.
      */
     $usesEtags = false;
     // First, ETag Validation
     $etag = str_replace('"', '', $this->getHeader('if-match'));
     if ($etag) {
         $usesEtags = true;
         if ($etag !== $resource->getEtag()) {
             return false;
         }
     }
     // Second, Modification Date Validation
     $ifUnmodifiedSince = $this->getHeader('if-unmodified-since');
     if ($ifUnmodifiedSince && $usesEtags === false) {
         if (strtotime($ifUnmodifiedSince) < $resource->getLastUpdated()->getTimestamp()) {
             return false;
         }
     }
     return true;
 }
 /**
  * Set cache settings (simple for now)
  *
  * @param Fideloper\ResourceCache\Resource\ResourceInterface
  * @param Symfony\Component\HttpFoundation\Response
  * @return Symfony\Component\HttpFoundation\Response
  */
 protected function setCache(ResourceInterface $resource, HttpResponse $response)
 {
     $response->setCache(array('etag' => $resource->getEtag(), 'last_modified' => $resource->getLastUpdated()));
     return $response;
 }