/**
* Evaluate preconditions found in this request based on the given values and create an appropriate
* HTTP response if an HTTP/1.1 304 Not Modified response should be sent.
*
* You can pass an ETag, a modification time or bot of these to the method, every precondition
* that is not NULL will be checked.
*
* @param EntityTag $etag The ETag of the requested resource.
* @param \DateTimeInterface $lastModified Date of the last modification of the requested resource.
* @return HttpResponse An HTTP 304 response or NULL if the client cache is invalid.
*/
public function evaluatePreconditions(EntityTag $etag = NULL, \DateTimeInterface $lastModified = NULL)
{
$response = new HttpResponse();
if ($etag !== NULL) {
if ($this->hasHeader('If-None-Match')) {
$valid = $this->firstHeader(function (IfNoneMatchHeader $match) use($etag) {
return $match->isWildcard() || $match->getEntityTag() == $etag;
});
if ($valid) {
$response->setStatus(Http::CODE_NOT_MODIFIED);
$response->setReason(Http::getReason(Http::CODE_NOT_MODIFIED));
$response->setHeader(new ETagHeader($etag));
}
}
}
if ($lastModified !== NULL) {
$unmodified = false;
if ($this->hasHeader('If-Modified-Since')) {
$unmodified = $this->firstHeader(function (IfModifiedSinceHeader $since) use($lastModified) {
return $since->getDate() >= $lastModified;
});
}
if ($unmodified) {
$response->setStatus(Http::CODE_NOT_MODIFIED);
$response->setReason(Http::getReason(Http::CODE_NOT_MODIFIED));
$response->setHeader(new LastModifiedHeader($lastModified));
}
}
return $response->isRedirect() ? $response : NULL;
}
