1<?php
2
3namespace Drupal\Core\Cache\Context;
4
5use Drupal\Core\Cache\CacheableMetadata;
6
7/**
8 * Defines the HeadersCacheContext service, for "per header" caching.
9 *
10 * Cache context ID: 'headers' (to vary by all headers).
11 * Calculated cache context ID: 'headers:%name', e.g. 'headers:X-Something' (to
12 * vary by the 'X-Something' header).
13 */
14class HeadersCacheContext extends RequestStackCacheContextBase implements CalculatedCacheContextInterface {
15
16  /**
17   * {@inheritdoc}
18   */
19  public static function getLabel() {
20    return t('HTTP headers');
21  }
22
23  /**
24   * {@inheritdoc}
25   */
26  public function getContext($header = NULL) {
27    if ($header === NULL) {
28      $headers = $this->requestStack->getCurrentRequest()->headers->all();
29      // Order headers by name to have less cache variations.
30      ksort($headers);
31      $result = '';
32      foreach ($headers as $name => $value) {
33        if ($result) {
34          $result .= '&';
35        }
36        // Sort values to minimize cache variations.
37        sort($value);
38        $result .= $name . '=' . implode(',', $value);
39      }
40      return $result;
41    }
42    elseif ($this->requestStack->getCurrentRequest()->headers->has($header)) {
43      $value = $this->requestStack->getCurrentRequest()->headers->get($header);
44      if ($value !== '') {
45        return $value;
46      }
47      return '?valueless?';
48    }
49    return '';
50  }
51
52  /**
53   * {@inheritdoc}
54   */
55  public function getCacheableMetadata($header = NULL) {
56    return new CacheableMetadata();
57  }
58
59}
60