src/Util/JsonLD.php

   1 <?php
   2 /**
   3  * @file src/Util/JsonLD.php
   4  */
   5 namespace Friendica\Util;
   6
   7 use Friendica\Core\Cache;
   8 use Friendica\Core\Logger;
   9 use Exception;
  10
  11 /**
  12  * @brief This class contain methods to work with JsonLD data
  13  */
  14 class JsonLD
  15 {
  16         /**
  17          * @brief Loader for LD-JSON validation
  18          *
  19          * @param $url
  20          *
  21          * @return mixed the loaded data
  22          * @throws \JsonLdException
  23          */
  24         public static function documentLoader($url)
  25         {
  26                 $recursion = 0;
  27
  28                 $x = debug_backtrace();
  29                 if ($x) {
  30                         foreach ($x as $n) {
  31                                 if ($n['function'] === __FUNCTION__)  {
  32                                         $recursion ++;
  33                                 }
  34                         }
  35                 }
  36
  37                 if ($recursion > 5) {
  38                         Logger::error('jsonld bomb detected at: ' . $url);
  39                         exit();
  40                 }
  41
  42                 $result = Cache::get('documentLoader:' . $url);
  43                 if (!is_null($result)) {
  44                         return $result;
  45                 }
  46
  47                 $data = jsonld_default_document_loader($url);
  48                 Cache::set('documentLoader:' . $url, $data, Cache::DAY);
  49                 return $data;
  50         }
  51
  52         /**
  53          * @brief Normalises a given JSON array
  54          *
  55          * @param array $json
  56          *
  57          * @return mixed|bool normalized JSON string
  58          * @throws Exception
  59          */
  60         public static function normalize($json)
  61         {
  62                 jsonld_set_document_loader('Friendica\Util\JsonLD::documentLoader');
  63
  64                 $jsonobj = json_decode(json_encode($json, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE));
  65
  66                 try {
  67                         $normalized = jsonld_normalize($jsonobj, array('algorithm' => 'URDNA2015', 'format' => 'application/nquads'));
  68                 }
  69                 catch (Exception $e) {
  70                         $normalized = false;
  71                         Logger::error('normalise error');
  72                         // Sooner or later we should log some details as well - but currently this leads to memory issues
  73                         // Logger::log('normalise error:' . substr(print_r($e, true), 0, 10000), Logger::DEBUG);
  74                 }
  75
  76                 return $normalized;
  77         }
  78
  79         /**
  80          * @brief Compacts a given JSON array
  81          *
  82          * @param array $json
  83          *
  84          * @return array Compacted JSON array
  85          * @throws Exception
  86          */
  87         public static function compact($json)
  88         {
  89                 jsonld_set_document_loader('Friendica\Util\JsonLD::documentLoader');
  90
  91                 $context = (object)['as' => 'https://www.w3.org/ns/activitystreams#',
  92                         'w3id' => 'https://w3id.org/security#',
  93                         'ldp' => (object)['@id' => 'http://www.w3.org/ns/ldp#', '@type' => '@id'],
  94                         'vcard' => (object)['@id' => 'http://www.w3.org/2006/vcard/ns#', '@type' => '@id'],
  95                         'dfrn' => (object)['@id' => 'http://purl.org/macgirvin/dfrn/1.0/', '@type' => '@id'],
  96                         'diaspora' => (object)['@id' => 'https://diasporafoundation.org/ns/', '@type' => '@id'],
  97                         'ostatus' => (object)['@id' => 'http://ostatus.org#', '@type' => '@id'],
  98                         'dc' => (object)['@id' => 'http://purl.org/dc/terms/', '@type' => '@id'],
  99                         'toot' => (object)['@id' => 'http://joinmastodon.org/ns#', '@type' => '@id']];
 100
 101                 // Preparation for adding possibly missing content to the context
 102                 if (!empty($json['@context']) && is_string($json['@context'])) {
 103                         $json['@context'] = [$json['@context']];
 104                 }
 105
 106                 // Workaround for servers with missing context
 107                 // See issue https://github.com/nextcloud/social/issues/330
 108                 if (!empty($json['@context']) && is_array($json['@context'])) {
 109                         $json['@context'][] = 'https://w3id.org/security/v1';
 110                 }
 111
 112                 // Trying to avoid memory problems with large content fields
 113                 if (!empty($json['object']['source']['content'])) {
 114                         $content = $json['object']['source']['content'];
 115                         $json['object']['source']['content'] = '';
 116                 }
 117
 118                 $jsonobj = json_decode(json_encode($json, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE));
 119
 120                 try {
 121                         $compacted = jsonld_compact($jsonobj, $context);
 122                 }
 123                 catch (Exception $e) {
 124                         $compacted = false;
 125                         Logger::error('compacting error');
 126                         // Sooner or later we should log some details as well - but currently this leads to memory issues
 127                         // Logger::log('compacting error:' . substr(print_r($e, true), 0, 10000), Logger::DEBUG);
 128                 }
 129
 130                 $json = json_decode(json_encode($compacted, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE), true);
 131
 132                 if (isset($json['as:object']['as:source']['as:content']) && !empty($content)) {
 133                         $json['as:object']['as:source']['as:content'] = $content;
 134                 }
 135
 136                 return $json;
 137         }
 138
 139         /**
 140          * @brief Fetches an element array from a JSON array
 141          *
 142          * @param $array
 143          * @param $element
 144          * @param $key
 145          *
 146          * @return array fetched element
 147          */
 148         public static function fetchElementArray($array, $element, $key = '@id')
 149         {
 150                 if (empty($array)) {
 151                         return null;
 152                 }
 153
 154                 if (!isset($array[$element])) {
 155                         return null;
 156                 }
 157
 158                 // If it isn't an array yet, make it to one
 159                 if (!is_int(key($array[$element]))) {
 160                         $array[$element] = [$array[$element]];
 161                 }
 162
 163                 $elements = [];
 164
 165                 foreach ($array[$element] as $entry) {
 166                         if (!is_array($entry)) {
 167                                 $elements[] = $entry;
 168                         } elseif (isset($entry[$key])) {
 169                                 $elements[] = $entry[$key];
 170                         } elseif (!empty($entry) || !is_array($entry)) {
 171                                 $elements[] = $entry;
 172                         }
 173                 }
 174
 175                 return $elements;
 176         }
 177
 178         /**
 179          * @brief Fetches an element from a JSON array
 180          *
 181          * @param $array
 182          * @param $element
 183          * @param $key
 184          * @param $type
 185          * @param $type_value
 186          *
 187          * @return string fetched element
 188          */
 189         public static function fetchElement($array, $element, $key = '@id', $type = null, $type_value = null)
 190         {
 191                 if (empty($array)) {
 192                         return null;
 193                 }
 194
 195                 if (!isset($array[$element])) {
 196                         return null;
 197                 }
 198
 199                 if (!is_array($array[$element])) {
 200                         return $array[$element];
 201                 }
 202
 203                 if (is_null($type) || is_null($type_value)) {
 204                         $element_array = self::fetchElementArray($array, $element, $key);
 205                         if (is_null($element_array)) {
 206                                 return null;
 207                         }
 208
 209                         return array_shift($element_array);
 210                 }
 211
 212                 $element_array = self::fetchElementArray($array, $element);
 213                 if (is_null($element_array)) {
 214                         return null;
 215                 }
 216
 217                 foreach ($element_array as $entry) {
 218                         if (isset($entry[$key]) && isset($entry[$type]) && ($entry[$type] == $type_value)) {
 219                                 return $entry[$key];
 220                         }
 221                 }
 222
 223                 return null;
 224         }
 225 }