/**
* Validates that a cache entry is fresh.
*
* The original request is used as a template for a conditional
* GET request with the backend.
*
* @param Symfony\Components\HttpFoundation\Request $request A Request instance
* @param Symfony\Components\HttpFoundation\Response $entry A Response instance to validate
*
* @return Symfony\Components\HttpFoundation\Response A Response instance
*/
protected function validate(Request $request, $entry)
{
$subRequest = clone $request;
// send no head requests because we want content
$subRequest->setMethod('get');
// add our cached last-modified validator
$subRequest->headers->set('if_modified_since', $entry->headers->get('Last-Modified'));
// Add our cached etag validator to the environment.
// We keep the etags from the client to handle the case when the client
// has a different private valid entry which is not cached here.
$cachedEtags = array($entry->getEtag());
$requestEtags = $request->getEtags();
$etags = array_unique(array_merge($cachedEtags, $requestEtags));
$subRequest->headers->set('if_none_match', $etags ? implode(', ', $etags) : '');
$response = $this->forward($subRequest, false, $entry);
if (304 == $response->getStatusCode()) {
$this->record($request, 'valid');
// return the response and not the cache entry if the response is valid but not cached
$etag = $response->getEtag();
if ($etag && in_array($etag, $requestEtags) && !in_array($etag, $cachedEtags)) {
return $response;
}
$entry = clone $entry;
$entry->headers->delete('Date');
foreach (array('Date', 'Expires', 'Cache-Control', 'ETag', 'Last-Modified') as $name) {
if ($response->headers->has($name)) {
$entry->headers->set($name, $response->headers->get($name));
}
}
$response = $entry;
} else {
$this->record($request, 'invalid');
}
if ($response->isCacheable()) {
$this->store($request, $response);
}
return $response;
}
