Chris@0: <?php
Chris@0: 
Chris@0: namespace Drupal\Component\Utility;
Chris@0: 
Chris@0: /**
Chris@0:  * Provides user agent related utility functions.
Chris@0:  *
Chris@0:  * @ingroup utility
Chris@0:  */
Chris@0: class UserAgent {
Chris@0: 
Chris@0:   /**
Chris@0:    * Identifies user agent language from the Accept-language HTTP header.
Chris@0:    *
Chris@0:    * The algorithm works as follows:
Chris@0:    * - map user agent language codes to available language codes.
Chris@0:    * - order all user agent language codes by qvalue from high to low.
Chris@0:    * - add generic user agent language codes if they aren't already specified
Chris@0:    *   but with a slightly lower qvalue.
Chris@0:    * - find the most specific available language code with the highest qvalue.
Chris@0:    * - if 2 or more languages are having the same qvalue, respect the order of
Chris@0:    *   them inside the $languages array.
Chris@0:    *
Chris@0:    * We perform user agent accept-language parsing only if page cache is
Chris@0:    * disabled, otherwise we would cache a user-specific preference.
Chris@0:    *
Chris@0:    * @param string $http_accept_language
Chris@0:    *   The value of the "Accept-Language" HTTP header.
Chris@0:    * @param array $langcodes
Chris@0:    *   An array of available language codes to pick from.
Chris@0:    * @param array $mappings
Chris@0:    *   (optional) Custom mappings to support user agents that are sending non
Chris@0:    *   standard language codes. No mapping is assumed by default.
Chris@0:    *
Chris@0:    * @return string
Chris@0:    *   The selected language code or FALSE if no valid language can be
Chris@0:    *   identified.
Chris@0:    */
Chris@0:   public static function getBestMatchingLangcode($http_accept_language, $langcodes, $mappings = []) {
Chris@0:     // The Accept-Language header contains information about the language
Chris@0:     // preferences configured in the user's user agent / operating system.
Chris@0:     // RFC 2616 (section 14.4) defines the Accept-Language header as follows:
Chris@0:     //   Accept-Language = "Accept-Language" ":"
Chris@0:     //                  1#( language-range [ ";" "q" "=" qvalue ] )
Chris@0:     //   language-range  = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )
Chris@0:     // Samples: "hu, en-us;q=0.66, en;q=0.33", "hu,en-us;q=0.5"
Chris@0:     $ua_langcodes = [];
Chris@0:     if (preg_match_all('@(?<=[, ]|^)([a-zA-Z-]+|\*)(?:;q=([0-9.]+))?(?:$|\s*,\s*)@', trim($http_accept_language), $matches, PREG_SET_ORDER)) {
Chris@0:       foreach ($matches as $match) {
Chris@0:         if ($mappings) {
Chris@0:           $langcode = strtolower($match[1]);
Chris@0:           foreach ($mappings as $ua_langcode => $standard_langcode) {
Chris@0:             if ($langcode == $ua_langcode) {
Chris@0:               $match[1] = $standard_langcode;
Chris@0:             }
Chris@0:           }
Chris@0:         }
Chris@0:         // We can safely use strtolower() here, tags are ASCII.
Chris@0:         // RFC2616 mandates that the decimal part is no more than three digits,
Chris@0:         // so we multiply the qvalue by 1000 to avoid floating point
Chris@0:         // comparisons.
Chris@0:         $langcode = strtolower($match[1]);
Chris@0:         $qvalue = isset($match[2]) ? (float) $match[2] : 1;
Chris@0:         // Take the highest qvalue for this langcode. Although the request
Chris@0:         // supposedly contains unique langcodes, our mapping possibly resolves
Chris@0:         // to the same langcode for different qvalues. Keep the highest.
Chris@0:         $ua_langcodes[$langcode] = max(
Chris@0:           (int) ($qvalue * 1000),
Chris@0:           (isset($ua_langcodes[$langcode]) ? $ua_langcodes[$langcode] : 0)
Chris@0:         );
Chris@0:       }
Chris@0:     }
Chris@0: 
Chris@0:     // We should take pristine values from the HTTP headers, but Internet
Chris@0:     // Explorer from version 7 sends only specific language tags (eg. fr-CA)
Chris@0:     // without the corresponding generic tag (fr) unless explicitly configured.
Chris@0:     // In that case, we assume that the lowest value of the specific tags is the
Chris@0:     // value of the generic language to be as close to the HTTP 1.1 spec as
Chris@0:     // possible.
Chris@0:     // See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4 and
Chris@0:     // http://blogs.msdn.com/b/ie/archive/2006/10/17/accept-language-header-for-internet-explorer-7.aspx
Chris@0:     asort($ua_langcodes);
Chris@0:     foreach ($ua_langcodes as $langcode => $qvalue) {
Chris@0:       // For Chinese languages the generic tag is either zh-hans or zh-hant, so
Chris@0:       // we need to handle this separately, we can not split $langcode on the
Chris@0:       // first occurrence of '-' otherwise we get a non-existing language zh.
Chris@0:       // All other languages use a langcode without a '-', so we can safely
Chris@0:       // split on the first occurrence of it.
Chris@0:       if (strlen($langcode) > 7 && (substr($langcode, 0, 7) == 'zh-hant' || substr($langcode, 0, 7) == 'zh-hans')) {
Chris@0:         $generic_tag = substr($langcode, 0, 7);
Chris@0:       }
Chris@0:       else {
Chris@0:         $generic_tag = strtok($langcode, '-');
Chris@0:       }
Chris@0:       if (!empty($generic_tag) && !isset($ua_langcodes[$generic_tag])) {
Chris@0:         // Add the generic langcode, but make sure it has a lower qvalue as the
Chris@0:         // more specific one, so the more specific one gets selected if it's
Chris@0:         // defined by both the user agent and us.
Chris@0:         $ua_langcodes[$generic_tag] = $qvalue - 0.1;
Chris@0:       }
Chris@0:     }
Chris@0: 
Chris@0:     // Find the added language with the greatest qvalue, following the rules
Chris@0:     // of RFC 2616 (section 14.4). If several languages have the same qvalue,
Chris@0:     // prefer the one with the greatest weight.
Chris@0:     $best_match_langcode = FALSE;
Chris@0:     $max_qvalue = 0;
Chris@0:     foreach ($langcodes as $langcode_case_sensitive) {
Chris@0:       // Language tags are case insensitive (RFC2616, sec 3.10).
Chris@0:       $langcode = strtolower($langcode_case_sensitive);
Chris@0: 
Chris@0:       // If nothing matches below, the default qvalue is the one of the wildcard
Chris@0:       // language, if set, or is 0 (which will never match).
Chris@0:       $qvalue = isset($ua_langcodes['*']) ? $ua_langcodes['*'] : 0;
Chris@0: 
Chris@0:       // Find the longest possible prefix of the user agent supplied language
Chris@0:       // ('the language-range') that matches this site language ('the language
Chris@0:       // tag').
Chris@0:       $prefix = $langcode;
Chris@0:       do {
Chris@0:         if (isset($ua_langcodes[$prefix])) {
Chris@0:           $qvalue = $ua_langcodes[$prefix];
Chris@0:           break;
Chris@0:         }
Chris@0:       } while ($prefix = substr($prefix, 0, strrpos($prefix, '-')));
Chris@0: 
Chris@0:       // Find the best match.
Chris@0:       if ($qvalue > $max_qvalue) {
Chris@0:         $best_match_langcode = $langcode_case_sensitive;
Chris@0:         $max_qvalue = $qvalue;
Chris@0:       }
Chris@0:     }
Chris@0: 
Chris@0:     return $best_match_langcode;
Chris@0:   }
Chris@0: 
Chris@0: }