src/Util/JsonLD.php

   1 <?php
   2 /**
   3  * @file src/Util/JsonLD.php
   4  */
   5 namespace Friendica\Util;
   6
   7 use Friendica\Core\Cache\Cache;
   8 use Friendica\Core\Logger;
   9 use Exception;
  10 use Friendica\DI;
  11
  12 /**
  13  * @brief This class contain methods to work with JsonLD data
  14  */
  15 class JsonLD
  16 {
  17         /**
  18          * @brief Loader for LD-JSON validation
  19          *
  20          * @param $url
  21          *
  22          * @return mixed the loaded data
  23          * @throws \JsonLdException
  24          */
  25         public static function documentLoader($url)
  26         {
  27                 $recursion = 0;
  28
  29                 $x = debug_backtrace();
  30                 if ($x) {
  31                         foreach ($x as $n) {
  32                                 if ($n['function'] === __FUNCTION__)  {
  33                                         $recursion ++;
  34                                 }
  35                         }
  36                 }
  37
  38                 if ($recursion > 5) {
  39                         Logger::error('jsonld bomb detected at: ' . $url);
  40                         exit();
  41                 }
  42
  43                 $result = DI::cache()->get('documentLoader:' . $url);
  44                 if (!is_null($result)) {
  45                         return $result;
  46                 }
  47
  48                 $data = jsonld_default_document_loader($url);
  49                 DI::cache()->set('documentLoader:' . $url, $data, Cache::DAY);
  50                 return $data;
  51         }
  52
  53         /**
  54          * @brief Normalises a given JSON array
  55          *
  56          * @param array $json
  57          *
  58          * @return mixed|bool normalized JSON string
  59          * @throws Exception
  60          */
  61         public static function normalize($json)
  62         {
  63                 jsonld_set_document_loader('Friendica\Util\JsonLD::documentLoader');
  64
  65                 $jsonobj = json_decode(json_encode($json, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE));
  66
  67                 try {
  68                         $normalized = jsonld_normalize($jsonobj, array('algorithm' => 'URDNA2015', 'format' => 'application/nquads'));
  69                 }
  70                 catch (Exception $e) {
  71                         $normalized = false;
  72                         $messages = [];
  73                         $currentException = $e;
  74                         do {
  75                                 $messages[] = $currentException->getMessage();
  76                         } while($currentException = $currentException->getPrevious());
  77
  78                         Logger::warning('JsonLD normalize error');
  79                         Logger::notice('JsonLD normalize error', ['messages' => $messages]);
  80                         Logger::info('JsonLD normalize error', ['trace' => $e->getTraceAsString()]);
  81                         Logger::debug('JsonLD normalize error', ['jsonobj' => $jsonobj]);
  82                 }
  83
  84                 return $normalized;
  85         }
  86
  87         /**
  88          * @brief Compacts a given JSON array
  89          *
  90          * @param array $json
  91          *
  92          * @return array Compacted JSON array
  93          * @throws Exception
  94          */
  95         public static function compact($json)
  96         {
  97                 jsonld_set_document_loader('Friendica\Util\JsonLD::documentLoader');
  98
  99                 $context = (object)['as' => 'https://www.w3.org/ns/activitystreams#',
 100                         'w3id' => 'https://w3id.org/security#',
 101                         'ldp' => (object)['@id' => 'http://www.w3.org/ns/ldp#', '@type' => '@id'],
 102                         'vcard' => (object)['@id' => 'http://www.w3.org/2006/vcard/ns#', '@type' => '@id'],
 103                         'dfrn' => (object)['@id' => 'http://purl.org/macgirvin/dfrn/1.0/', '@type' => '@id'],
 104                         'diaspora' => (object)['@id' => 'https://diasporafoundation.org/ns/', '@type' => '@id'],
 105                         'ostatus' => (object)['@id' => 'http://ostatus.org#', '@type' => '@id'],
 106                         'dc' => (object)['@id' => 'http://purl.org/dc/terms/', '@type' => '@id'],
 107                         'toot' => (object)['@id' => 'http://joinmastodon.org/ns#', '@type' => '@id'],
 108                         'litepub' => (object)['@id' => 'http://litepub.social/ns#', '@type' => '@id']];
 109
 110                 // Preparation for adding possibly missing content to the context
 111                 if (!empty($json['@context']) && is_string($json['@context'])) {
 112                         $json['@context'] = [$json['@context']];
 113                 }
 114
 115                 // Workaround for servers with missing context
 116                 // See issue https://github.com/nextcloud/social/issues/330
 117                 if (!empty($json['@context']) && is_array($json['@context'])) {
 118                         $json['@context'][] = 'https://w3id.org/security/v1';
 119                 }
 120
 121                 // Trying to avoid memory problems with large content fields
 122                 if (!empty($json['object']['source']['content'])) {
 123                         $content = $json['object']['source']['content'];
 124                         $json['object']['source']['content'] = '';
 125                 }
 126
 127                 $jsonobj = json_decode(json_encode($json, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE));
 128
 129                 try {
 130                         $compacted = jsonld_compact($jsonobj, $context);
 131                 }
 132                 catch (Exception $e) {
 133                         $compacted = false;
 134                         Logger::error('compacting error');
 135                         // Sooner or later we should log some details as well - but currently this leads to memory issues
 136                         // Logger::log('compacting error:' . substr(print_r($e, true), 0, 10000), Logger::DEBUG);
 137                 }
 138
 139                 $json = json_decode(json_encode($compacted, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE), true);
 140
 141                 if (isset($json['as:object']['as:source']['as:content']) && !empty($content)) {
 142                         $json['as:object']['as:source']['as:content'] = $content;
 143                 }
 144
 145                 return $json;
 146         }
 147
 148         /**
 149          * @brief Fetches an element array from a JSON array
 150          *
 151          * @param $array
 152          * @param $element
 153          * @param $key
 154          *
 155          * @return array fetched element
 156          */
 157         public static function fetchElementArray($array, $element, $key = '@id')
 158         {
 159                 if (empty($array)) {
 160                         return null;
 161                 }
 162
 163                 if (!isset($array[$element])) {
 164                         return null;
 165                 }
 166
 167                 // If it isn't an array yet, make it to one
 168                 if (!is_int(key($array[$element]))) {
 169                         $array[$element] = [$array[$element]];
 170                 }
 171
 172                 $elements = [];
 173
 174                 foreach ($array[$element] as $entry) {
 175                         if (!is_array($entry)) {
 176                                 $elements[] = $entry;
 177                         } elseif (isset($entry[$key])) {
 178                                 $elements[] = $entry[$key];
 179                         } elseif (!empty($entry) || !is_array($entry)) {
 180                                 $elements[] = $entry;
 181                         }
 182                 }
 183
 184                 return $elements;
 185         }
 186
 187         /**
 188          * @brief Fetches an element from a JSON array
 189          *
 190          * @param $array
 191          * @param $element
 192          * @param $key
 193          * @param $type
 194          * @param $type_value
 195          *
 196          * @return string fetched element
 197          */
 198         public static function fetchElement($array, $element, $key = '@id', $type = null, $type_value = null)
 199         {
 200                 if (empty($array)) {
 201                         return null;
 202                 }
 203
 204                 if (!isset($array[$element])) {
 205                         return null;
 206                 }
 207
 208                 if (!is_array($array[$element])) {
 209                         return $array[$element];
 210                 }
 211
 212                 if (is_null($type) || is_null($type_value)) {
 213                         $element_array = self::fetchElementArray($array, $element, $key);
 214                         if (is_null($element_array)) {
 215                                 return null;
 216                         }
 217
 218                         return array_shift($element_array);
 219                 }
 220
 221                 $element_array = self::fetchElementArray($array, $element);
 222                 if (is_null($element_array)) {
 223                         return null;
 224                 }
 225
 226                 foreach ($element_array as $entry) {
 227                         if (isset($entry[$key]) && isset($entry[$type]) && ($entry[$type] == $type_value)) {
 228                                 return $entry[$key];
 229                         }
 230                 }
 231
 232                 return null;
 233         }
 234 }