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