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                         $messages = [];
  72                         $currentException = $e;
  73                         do {
  74                                 $messages[] = $currentException->getMessage();
  75                         } while($currentException = $currentException->getPrevious());
  76
  77                         Logger::warning('JsonLD normalize error');
  78                         Logger::notice('JsonLD normalize error', ['messages' => $messages]);
  79                         Logger::info('JsonLD normalize error', ['trace' => $e->getTraceAsString()]);
  80                         Logger::debug('JsonLD normalize error', ['jsonobj' => $jsonobj]);
  81                 }
  82
  83                 return $normalized;
  84         }
  85
  86         /**
  87          * @brief Compacts a given JSON array
  88          *
  89          * @param array $json
  90          *
  91          * @return array Compacted JSON array
  92          * @throws Exception
  93          */
  94         public static function compact($json)
  95         {
  96                 jsonld_set_document_loader('Friendica\Util\JsonLD::documentLoader');
  97
  98                 $context = (object)['as' => 'https://www.w3.org/ns/activitystreams#',
  99                         'w3id' => 'https://w3id.org/security#',
 100                         'ldp' => (object)['@id' => 'http://www.w3.org/ns/ldp#', '@type' => '@id'],
 101                         'vcard' => (object)['@id' => 'http://www.w3.org/2006/vcard/ns#', '@type' => '@id'],
 102                         'dfrn' => (object)['@id' => 'http://purl.org/macgirvin/dfrn/1.0/', '@type' => '@id'],
 103                         'diaspora' => (object)['@id' => 'https://diasporafoundation.org/ns/', '@type' => '@id'],
 104                         'ostatus' => (object)['@id' => 'http://ostatus.org#', '@type' => '@id'],
 105                         'dc' => (object)['@id' => 'http://purl.org/dc/terms/', '@type' => '@id'],
 106                         'toot' => (object)['@id' => 'http://joinmastodon.org/ns#', '@type' => '@id'],
 107                         'litepub' => (object)['@id' => 'http://litepub.social/ns#', '@type' => '@id']];
 108
 109                 // Preparation for adding possibly missing content to the context
 110                 if (!empty($json['@context']) && is_string($json['@context'])) {
 111                         $json['@context'] = [$json['@context']];
 112                 }
 113
 114                 // Workaround for servers with missing context
 115                 // See issue https://github.com/nextcloud/social/issues/330
 116                 if (!empty($json['@context']) && is_array($json['@context'])) {
 117                         $json['@context'][] = 'https://w3id.org/security/v1';
 118                 }
 119
 120                 // Trying to avoid memory problems with large content fields
 121                 if (!empty($json['object']['source']['content'])) {
 122                         $content = $json['object']['source']['content'];
 123                         $json['object']['source']['content'] = '';
 124                 }
 125
 126                 $jsonobj = json_decode(json_encode($json, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE));
 127
 128                 try {
 129                         $compacted = jsonld_compact($jsonobj, $context);
 130                 }
 131                 catch (Exception $e) {
 132                         $compacted = false;
 133                         Logger::error('compacting error');
 134                         // Sooner or later we should log some details as well - but currently this leads to memory issues
 135                         // Logger::log('compacting error:' . substr(print_r($e, true), 0, 10000), Logger::DEBUG);
 136                 }
 137
 138                 $json = json_decode(json_encode($compacted, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE), true);
 139
 140                 if (isset($json['as:object']['as:source']['as:content']) && !empty($content)) {
 141                         $json['as:object']['as:source']['as:content'] = $content;
 142                 }
 143
 144                 return $json;
 145         }
 146
 147         /**
 148          * @brief Fetches an element array from a JSON array
 149          *
 150          * @param $array
 151          * @param $element
 152          * @param $key
 153          *
 154          * @return array fetched element
 155          */
 156         public static function fetchElementArray($array, $element, $key = '@id')
 157         {
 158                 if (empty($array)) {
 159                         return null;
 160                 }
 161
 162                 if (!isset($array[$element])) {
 163                         return null;
 164                 }
 165
 166                 // If it isn't an array yet, make it to one
 167                 if (!is_int(key($array[$element]))) {
 168                         $array[$element] = [$array[$element]];
 169                 }
 170
 171                 $elements = [];
 172
 173                 foreach ($array[$element] as $entry) {
 174                         if (!is_array($entry)) {
 175                                 $elements[] = $entry;
 176                         } elseif (isset($entry[$key])) {
 177                                 $elements[] = $entry[$key];
 178                         } elseif (!empty($entry) || !is_array($entry)) {
 179                                 $elements[] = $entry;
 180                         }
 181                 }
 182
 183                 return $elements;
 184         }
 185
 186         /**
 187          * @brief Fetches an element from a JSON array
 188          *
 189          * @param $array
 190          * @param $element
 191          * @param $key
 192          * @param $type
 193          * @param $type_value
 194          *
 195          * @return string fetched element
 196          */
 197         public static function fetchElement($array, $element, $key = '@id', $type = null, $type_value = null)
 198         {
 199                 if (empty($array)) {
 200                         return null;
 201                 }
 202
 203                 if (!isset($array[$element])) {
 204                         return null;
 205                 }
 206
 207                 if (!is_array($array[$element])) {
 208                         return $array[$element];
 209                 }
 210
 211                 if (is_null($type) || is_null($type_value)) {
 212                         $element_array = self::fetchElementArray($array, $element, $key);
 213                         if (is_null($element_array)) {
 214                                 return null;
 215                         }
 216
 217                         return array_shift($element_array);
 218                 }
 219
 220                 $element_array = self::fetchElementArray($array, $element);
 221                 if (is_null($element_array)) {
 222                         return null;
 223                 }
 224
 225                 foreach ($element_array as $entry) {
 226                         if (isset($entry[$key]) && isset($entry[$type]) && ($entry[$type] == $type_value)) {
 227                                 return $entry[$key];
 228                         }
 229                 }
 230
 231                 return null;
 232         }
 233 }