ChainResponsePolicy.php

<?php

namespace Drupal\Core\PageCache;

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

/**
 * Implements a compound response policy.
 *
 * When evaluating the compound policy, all of the contained rules are applied
 * to the response. The overall result is computed according to the following
 * rules:
 *
 * <ol>
 *   <li>Returns static::DENY if any of the rules evaluated to static::DENY</li>
 *   <li>Otherwise returns NULL</li>
 * </ol>
 */
class ChainResponsePolicy implements ChainResponsePolicyInterface {
    
    /**
     * A list of policy rules to apply when this policy is checked.
     *
     * @var \Drupal\Core\PageCache\ResponsePolicyInterface[]
     */
    protected $rules = [];
    
    /**
     * {@inheritdoc}
     */
    public function check(Response $response, Request $request) {
        foreach ($this->rules as $rule) {
            $result = $rule->check($response, $request);
            if ($result === static::DENY) {
                return $result;
            }
            elseif (isset($result)) {
                throw new \UnexpectedValueException('Return value of ResponsePolicyInterface::check() must be one of ResponsePolicyInterface::DENY or NULL');
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function addPolicy(ResponsePolicyInterface $policy) {
        $this->rules[] = $policy;
        return $this;
    }

}