src/Protocol/ActivityPub/Processor.php

   1 <?php
   2 /**
   3  * @copyright Copyright (C) 2010-2021, the Friendica project
   4  *
   5  * @license GNU AGPL version 3 or any later version
   6  *
   7  * This program is free software: you can redistribute it and/or modify
   8  * it under the terms of the GNU Affero General Public License as
   9  * published by the Free Software Foundation, either version 3 of the
  10  * License, or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU Affero General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Affero General Public License
  18  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  19  *
  20  */
  21
  22 namespace Friendica\Protocol\ActivityPub;
  23
  24 use Friendica\Content\PageInfo;
  25 use Friendica\Content\Text\BBCode;
  26 use Friendica\Content\Text\HTML;
  27 use Friendica\Content\Text\Markdown;
  28 use Friendica\Core\Logger;
  29 use Friendica\Core\Protocol;
  30 use Friendica\Database\DBA;
  31 use Friendica\DI;
  32 use Friendica\Model\APContact;
  33 use Friendica\Model\Contact;
  34 use Friendica\Model\Conversation;
  35 use Friendica\Model\Event;
  36 use Friendica\Model\GServer;
  37 use Friendica\Model\Item;
  38 use Friendica\Model\ItemURI;
  39 use Friendica\Model\Mail;
  40 use Friendica\Model\Tag;
  41 use Friendica\Model\User;
  42 use Friendica\Model\Post;
  43 use Friendica\Protocol\Activity;
  44 use Friendica\Protocol\ActivityPub;
  45 use Friendica\Protocol\Relay;
  46 use Friendica\Util\DateTimeFormat;
  47 use Friendica\Util\JsonLD;
  48 use Friendica\Util\Strings;
  49
  50 /**
  51  * ActivityPub Processor Protocol class
  52  */
  53 class Processor
  54 {
  55         /**
  56          * Converts mentions from Pleroma into the Friendica format
  57          *
  58          * @param string $body
  59          *
  60          * @return string converted body
  61          */
  62         private static function convertMentions($body)
  63         {
  64                 $URLSearchString = "^\[\]";
  65                 $body = preg_replace("/\[url\=([$URLSearchString]*)\]([#@!])(.*?)\[\/url\]/ism", '$2[url=$1]$3[/url]', $body);
  66
  67                 return $body;
  68         }
  69
  70         /**
  71          * Convert the language array into a language JSON
  72          *
  73          * @param array $languages
  74          * @return string language JSON
  75          */
  76         private static function processLanguages(array $languages)
  77         {
  78                 $codes = array_keys($languages);
  79                 $lang = [];
  80                 foreach ($codes as $code) {
  81                         $lang[$code] = 1;
  82                 }
  83
  84                 if (empty($lang)) {
  85                         return '';
  86                 }
  87
  88                 return json_encode($lang);
  89         }
  90         /**
  91          * Replaces emojis in the body
  92          *
  93          * @param array $emojis
  94          * @param string $body
  95          *
  96          * @return string with replaced emojis
  97          */
  98         private static function replaceEmojis($body, array $emojis)
  99         {
 100                 $body = strtr($body,
 101                         array_combine(
 102                                 array_column($emojis, 'name'),
 103                                 array_map(function ($emoji) {
 104                                         return '[class=emoji mastodon][img=' . $emoji['href'] . ']' . $emoji['name'] . '[/img][/class]';
 105                                 }, $emojis)
 106                         )
 107                 );
 108
 109                 return $body;
 110         }
 111
 112         /**
 113          * Store attached media files in the post-media table
 114          *
 115          * @param int $uriid
 116          * @param array $attachment
 117          * @return void
 118          */
 119         private static function storeAttachmentAsMedia(int $uriid, array $attachment)
 120         {
 121                 if (empty($attachment['url'])) {
 122                         return;
 123                 }
 124
 125                 $data = ['uri-id' => $uriid];
 126                 $data['type'] = Post\Media::UNKNOWN;
 127                 $data['url'] = $attachment['url'];
 128                 $data['mimetype'] = $attachment['mediaType'];
 129                 $data['height'] = $attachment['height'] ?? null;
 130                 $data['size'] = $attachment['size'] ?? null;
 131                 $data['preview'] = $attachment['image'] ?? null;
 132                 $data['description'] = $attachment['name'] ?? null;
 133
 134                 Post\Media::insert($data);
 135         }
 136
 137         /**
 138          * Add attachment data to the item array
 139          *
 140          * @param array   $activity
 141          * @param array   $item
 142          *
 143          * @return array array
 144          */
 145         private static function constructAttachList($activity, $item)
 146         {
 147                 if (empty($activity['attachments'])) {
 148                         return $item;
 149                 }
 150
 151                 $leading = '';
 152                 $trailing = '';
 153
 154                 foreach ($activity['attachments'] as $attach) {
 155                         switch ($attach['type']) {
 156                                 case 'link':
 157                                         $data = [
 158                                                 'url'      => $attach['url'],
 159                                                 'type'     => $attach['type'],
 160                                                 'title'    => $attach['title'] ?? '',
 161                                                 'text'     => $attach['desc']  ?? '',
 162                                                 'image'    => $attach['image'] ?? '',
 163                                                 'images'   => [],
 164                                                 'keywords' => [],
 165                                         ];
 166                                         $item['body'] = PageInfo::appendDataToBody($item['body'], $data);
 167                                         break;
 168                                 default:
 169                                         self::storeAttachmentAsMedia($item['uri-id'], $attach);
 170
 171                                         $filetype = strtolower(substr($attach['mediaType'], 0, strpos($attach['mediaType'], '/')));
 172                                         if ($filetype == 'image') {
 173                                                 if (!empty($activity['source'])) {
 174                                                         foreach ([0, 1, 2] as $size) {
 175                                                                 if (preg_match('#/photo/.*-' . $size . '\.#ism', $attach['url']) &&
 176                                                                         strpos(preg_replace('#(/photo/.*)-[012]\.#ism', '$1-' . $size . '.', $activity['source']), $attach['url'])) {
 177                                                                         continue 3;
 178                                                                 }
 179                                                         }
 180                                                         if (strpos($activity['source'], $attach['url'])) {
 181                                                                 continue 2;
 182                                                         }
 183                                                 }
 184
 185                                                 // image is the preview/thumbnail URL
 186                                                 if (!empty($attach['image'])) {
 187                                                         $media = '[url=' . $attach['url'] . ']';
 188                                                         $attach['url'] = $attach['image'];
 189                                                 } else {
 190                                                         $media = '';
 191                                                 }
 192
 193                                                 if (empty($attach['name'])) {
 194                                                         $media .= '[img]' . $attach['url'] . '[/img]';
 195                                                 } else {
 196                                                         $media .= '[img=' . $attach['url'] . ']' . $attach['name'] . '[/img]';
 197                                                 }
 198
 199                                                 if (!empty($attach['image'])) {
 200                                                         $media .= '[/url]';
 201                                                 }
 202
 203                                                 if ($item['post-type'] == Item::PT_IMAGE) {
 204                                                         $leading .= $media;
 205                                                 } else {
 206                                                         $trailing .= $media;
 207                                                 }
 208                                         } elseif ($filetype == 'audio') {
 209                                                 if (!empty($activity['source']) && strpos($activity['source'], $attach['url'])) {
 210                                                         continue 2;
 211                                                 }
 212
 213                                                 if ($item['post-type'] == Item::PT_AUDIO) {
 214                                                         $leading .= '[audio]' . $attach['url'] . "[/audio]\n";
 215                                                 } else {
 216                                                         $trailing .= '[audio]' . $attach['url'] . "[/audio]\n";
 217                                                 }
 218                                         } elseif ($filetype == 'video') {
 219                                                 if (!empty($activity['source']) && strpos($activity['source'], $attach['url'])) {
 220                                                         continue 2;
 221                                                 }
 222
 223                                                 if ($item['post-type'] == Item::PT_VIDEO) {
 224                                                         $leading .= '[video]' . $attach['url'] . "[/video]\n";
 225                                                 } else {
 226                                                         $trailing .= '[video]' . $attach['url'] . "[/video]\n";
 227                                                 }
 228                                         }
 229                         }
 230                 }
 231
 232                 if (!empty($leading) && !empty(trim($item['body']))) {
 233                         $item['body'] = $leading . "[hr]\n" . $item['body'];
 234                 } elseif (!empty($leading)) {
 235                         $item['body'] = $leading;
 236                 }
 237
 238                 if (!empty($trailing) && !empty(trim($item['body']))) {
 239                         $item['body'] = $item['body'] . "\n[hr]" . $trailing;
 240                 } elseif (!empty($trailing)) {
 241                         $item['body'] = $trailing;
 242                 }
 243
 244                 return $item;
 245         }
 246
 247         /**
 248          * Updates a message
 249          *
 250          * @param array $activity Activity array
 251          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 252          */
 253         public static function updateItem($activity)
 254         {
 255                 $item = Post::selectFirst(['uri', 'uri-id', 'thr-parent', 'gravity', 'post-type'], ['uri' => $activity['id']]);
 256                 if (!DBA::isResult($item)) {
 257                         Logger::warning('No existing item, item will be created', ['uri' => $activity['id']]);
 258                         $item = self::createItem($activity);
 259                         self::postItem($activity, $item);
 260                         return;
 261                 }
 262
 263                 $item['changed'] = DateTimeFormat::utcNow();
 264                 $item['edited'] = DateTimeFormat::utc($activity['updated']);
 265
 266                 $item = self::processContent($activity, $item);
 267
 268                 $item = self::constructAttachList($activity, $item);
 269
 270                 if (empty($item)) {
 271                         return;
 272                 }
 273
 274                 Item::update($item, ['uri' => $activity['id']]);
 275         }
 276
 277         /**
 278          * Prepares data for a message
 279          *
 280          * @param array $activity Activity array
 281          * @return array Internal item
 282          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 283          * @throws \ImagickException
 284          */
 285         public static function createItem($activity)
 286         {
 287                 $item = [];
 288                 $item['verb'] = Activity::POST;
 289                 $item['thr-parent'] = $activity['reply-to-id'];
 290
 291                 if ($activity['reply-to-id'] == $activity['id']) {
 292                         $item['gravity'] = GRAVITY_PARENT;
 293                         $item['object-type'] = Activity\ObjectType::NOTE;
 294                 } else {
 295                         $item['gravity'] = GRAVITY_COMMENT;
 296                         $item['object-type'] = Activity\ObjectType::COMMENT;
 297                 }
 298
 299                 if (empty($activity['directmessage']) && ($activity['id'] != $activity['reply-to-id']) && !Post::exists(['uri' => $activity['reply-to-id']])) {
 300                         Logger::notice('Parent not found. Try to refetch it.', ['parent' => $activity['reply-to-id']]);
 301                         self::fetchMissingActivity($activity['reply-to-id'], $activity);
 302                 }
 303
 304                 $item['diaspora_signed_text'] = $activity['diaspora:comment'] ?? '';
 305
 306                 /// @todo What to do with $activity['context']?
 307                 if (empty($activity['directmessage']) && ($item['gravity'] != GRAVITY_PARENT) && !Post::exists(['uri' => $item['thr-parent']])) {
 308                         Logger::info('Parent not found, message will be discarded.', ['thr-parent' => $item['thr-parent']]);
 309                         return [];
 310                 }
 311
 312                 $item['network'] = Protocol::ACTIVITYPUB;
 313                 $item['author-link'] = $activity['author'];
 314                 $item['author-id'] = Contact::getIdForURL($activity['author']);
 315                 $item['owner-link'] = $activity['actor'];
 316                 $item['owner-id'] = Contact::getIdForURL($activity['actor']);
 317
 318                 if (in_array(0, $activity['receiver']) && !empty($activity['unlisted'])) {
 319                         $item['private'] = Item::UNLISTED;
 320                 } elseif (in_array(0, $activity['receiver'])) {
 321                         $item['private'] = Item::PUBLIC;
 322                 } else {
 323                         $item['private'] = Item::PRIVATE;
 324                 }
 325
 326                 if (!empty($activity['raw'])) {
 327                         $item['source'] = $activity['raw'];
 328                         $item['protocol'] = Conversation::PARCEL_ACTIVITYPUB;
 329                         $item['conversation-href'] = $activity['context'] ?? '';
 330                         $item['conversation-uri'] = $activity['conversation'] ?? '';
 331
 332                         if (isset($activity['push'])) {
 333                                 $item['direction'] = $activity['push'] ? Conversation::PUSH : Conversation::PULL;
 334                         }
 335                 }
 336
 337                 if (!empty($activity['from-relay'])) {
 338                         $item['direction'] = Conversation::RELAY;
 339                 }
 340
 341                 if ($activity['object_type'] == 'as:Article') {
 342                         $item['post-type'] = Item::PT_ARTICLE;
 343                 } elseif ($activity['object_type'] == 'as:Audio') {
 344                         $item['post-type'] = Item::PT_AUDIO;
 345                 } elseif ($activity['object_type'] == 'as:Document') {
 346                         $item['post-type'] = Item::PT_DOCUMENT;
 347                 } elseif ($activity['object_type'] == 'as:Event') {
 348                         $item['post-type'] = Item::PT_EVENT;
 349                 } elseif ($activity['object_type'] == 'as:Image') {
 350                         $item['post-type'] = Item::PT_IMAGE;
 351                 } elseif ($activity['object_type'] == 'as:Page') {
 352                         $item['post-type'] = Item::PT_PAGE;
 353                 } elseif ($activity['object_type'] == 'as:Video') {
 354                         $item['post-type'] = Item::PT_VIDEO;
 355                 } else {
 356                         $item['post-type'] = Item::PT_NOTE;
 357                 }
 358
 359                 $item['isForum'] = false;
 360
 361                 if (!empty($activity['thread-completion'])) {
 362                         if ($activity['thread-completion'] != $item['owner-id']) {
 363                                 $actor = Contact::getById($activity['thread-completion'], ['url']);
 364                                 $item['causer-link'] = $actor['url'];
 365                                 $item['causer-id'] = $activity['thread-completion'];
 366                                 Logger::info('Use inherited actor as causer.', ['id' => $item['owner-id'], 'activity' => $activity['thread-completion'], 'owner' => $item['owner-link'], 'actor' => $actor['url']]);
 367                         } else {
 368                                 // Store the original actor in the "causer" fields to enable the check for ignored or blocked contacts
 369                                 $item['causer-link'] = $item['owner-link'];
 370                                 $item['causer-id'] = $item['owner-id'];
 371                                 Logger::info('Use actor as causer.', ['id' => $item['owner-id'], 'actor' => $item['owner-link']]);
 372                         }
 373
 374                         $item['owner-link'] = $item['author-link'];
 375                         $item['owner-id'] = $item['author-id'];
 376                 } else {
 377                         $actor = APContact::getByURL($item['owner-link'], false);
 378                         $item['isForum'] = ($actor['type'] == 'Group');
 379                 }
 380
 381                 $item['uri'] = $activity['id'];
 382
 383                 $item['created'] = DateTimeFormat::utc($activity['published']);
 384                 $item['edited'] = DateTimeFormat::utc($activity['updated']);
 385                 $guid = $activity['sc:identifier'] ?: self::getGUIDByURL($item['uri']);
 386                 $item['guid'] = $activity['diaspora:guid'] ?: $guid;
 387
 388                 $item['uri-id'] = ItemURI::insert(['uri' => $item['uri'], 'guid' => $item['guid']]);
 389                 if (empty($item['uri-id'])) {
 390                         Logger::warning('Unable to get a uri-id for an item uri', ['uri' => $item['uri'], 'guid' => $item['guid']]);
 391                         return [];
 392                 }
 393
 394                 $item = self::processContent($activity, $item);
 395                 if (empty($item)) {
 396                         Logger::info('Message was not processed');
 397                         return [];
 398                 }
 399
 400                 $item['plink'] = $activity['alternate-url'] ?? $item['uri'];
 401
 402                 $item = self::constructAttachList($activity, $item);
 403
 404                 // We received the post via AP, so we set the protocol of the server to AP
 405                 $contact = Contact::getById($item['author-id'], ['gsid']);
 406                 if (!empty($contact['gsid'])) {
 407                         GServer::setProtocol($contact['gsid'], Post\DeliveryData::ACTIVITYPUB);
 408                 }
 409
 410                 if ($item['author-id'] != $item['owner-id']) {
 411                         $contact = Contact::getById($item['owner-id'], ['gsid']);
 412                         if (!empty($contact['gsid'])) {
 413                                 GServer::setProtocol($contact['gsid'], Post\DeliveryData::ACTIVITYPUB);
 414                         }
 415                 }
 416
 417                 return $item;
 418         }
 419
 420         /**
 421          * Delete items
 422          *
 423          * @param array $activity
 424          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 425          * @throws \ImagickException
 426          */
 427         public static function deleteItem($activity)
 428         {
 429                 $owner = Contact::getIdForURL($activity['actor']);
 430
 431                 Logger::info('Deleting item', ['object' => $activity['object_id'], 'owner'  => $owner]);
 432                 Item::markForDeletion(['uri' => $activity['object_id'], 'owner-id' => $owner]);
 433         }
 434
 435         /**
 436          * Prepare the item array for an activity
 437          *
 438          * @param array $activity Activity array
 439          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 440          * @throws \ImagickException
 441          */
 442         public static function addTag($activity)
 443         {
 444                 if (empty($activity['object_content']) || empty($activity['object_id'])) {
 445                         return;
 446                 }
 447
 448                 foreach ($activity['receiver'] as $receiver) {
 449                         $item = Post::selectFirst(['id', 'uri-id', 'origin', 'author-link'], ['uri' => $activity['target_id'], 'uid' => $receiver]);
 450                         if (!DBA::isResult($item)) {
 451                                 // We don't fetch missing content for this purpose
 452                                 continue;
 453                         }
 454
 455                         if (($item['author-link'] != $activity['actor']) && !$item['origin']) {
 456                                 Logger::info('Not origin, not from the author, skipping update', ['id' => $item['id'], 'author' => $item['author-link'], 'actor' => $activity['actor']]);
 457                                 continue;
 458                         }
 459
 460                         Tag::store($item['uri-id'], Tag::HASHTAG, $activity['object_content'], $activity['object_id']);
 461                         Logger::info('Tagged item', ['id' => $item['id'], 'tag' => $activity['object_content'], 'uri' => $activity['target_id'], 'actor' => $activity['actor']]);
 462                 }
 463         }
 464
 465         /**
 466          * Prepare the item array for an activity
 467          *
 468          * @param array  $activity Activity array
 469          * @param string $verb     Activity verb
 470          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 471          * @throws \ImagickException
 472          */
 473         public static function createActivity($activity, $verb)
 474         {
 475                 $item = self::createItem($activity);
 476                 $item['verb'] = $verb;
 477                 $item['thr-parent'] = $activity['object_id'];
 478                 $item['gravity'] = GRAVITY_ACTIVITY;
 479                 unset($item['post-type']);
 480                 $item['object-type'] = Activity\ObjectType::NOTE;
 481
 482                 $item['diaspora_signed_text'] = $activity['diaspora:like'] ?? '';
 483
 484                 self::postItem($activity, $item);
 485         }
 486
 487         /**
 488          * Create an event
 489          *
 490          * @param array $activity Activity array
 491          * @param array $item
 492          * @throws \Exception
 493          */
 494         public static function createEvent($activity, $item)
 495         {
 496                 $event['summary']   = HTML::toBBCode($activity['name']);
 497                 $event['desc']      = HTML::toBBCode($activity['content']);
 498                 $event['start']     = $activity['start-time'];
 499                 $event['finish']    = $activity['end-time'];
 500                 $event['nofinish']  = empty($event['finish']);
 501                 $event['location']  = $activity['location'];
 502                 $event['adjust']    = $activity['adjust'] ?? true;
 503                 $event['cid']       = $item['contact-id'];
 504                 $event['uid']       = $item['uid'];
 505                 $event['uri']       = $item['uri'];
 506                 $event['edited']    = $item['edited'];
 507                 $event['private']   = $item['private'];
 508                 $event['guid']      = $item['guid'];
 509                 $event['plink']     = $item['plink'];
 510                 $event['network']   = $item['network'];
 511                 $event['protocol']  = $item['protocol'];
 512                 $event['direction'] = $item['direction'];
 513                 $event['source']    = $item['source'];
 514
 515                 $condition = ['uri' => $item['uri'], 'uid' => $item['uid']];
 516                 $ev = DBA::selectFirst('event', ['id'], $condition);
 517                 if (DBA::isResult($ev)) {
 518                         $event['id'] = $ev['id'];
 519                 }
 520
 521                 $event_id = Event::store($event);
 522                 Logger::info('Event was stored', ['id' => $event_id]);
 523         }
 524
 525         /**
 526          * Process the content
 527          *
 528          * @param array $activity Activity array
 529          * @param array $item
 530          * @return array|bool Returns the item array or false if there was an unexpected occurrence
 531          * @throws \Exception
 532          */
 533         private static function processContent($activity, $item)
 534         {
 535                 if (!empty($activity['mediatype']) && ($activity['mediatype'] == 'text/markdown')) {
 536                         $item['title'] = Markdown::toBBCode($activity['name']);
 537                         $content = Markdown::toBBCode($activity['content']);
 538                 } elseif (!empty($activity['mediatype']) && ($activity['mediatype'] == 'text/bbcode')) {
 539                         $item['title'] = $activity['name'];
 540                         $content = $activity['content'];
 541                 } else {
 542                         // By default assume "text/html"
 543                         $item['title'] = HTML::toBBCode($activity['name']);
 544                         $content = HTML::toBBCode($activity['content']);
 545                 }
 546
 547                 if (!empty($activity['languages'])) {
 548                         $item['language'] = self::processLanguages($activity['languages']);
 549                 }
 550
 551                 if (!empty($activity['emojis'])) {
 552                         $content = self::replaceEmojis($content, $activity['emojis']);
 553                 }
 554
 555                 $content = self::convertMentions($content);
 556
 557                 if (!empty($activity['source'])) {
 558                         $item['body'] = $activity['source'];
 559                         $item['raw-body'] = $content;
 560                 } else {
 561                         if (empty($activity['directmessage']) && ($item['thr-parent'] != $item['uri']) && ($item['gravity'] == GRAVITY_COMMENT)) {
 562                                 $item_private = !in_array(0, $activity['item_receiver']);
 563                                 $parent = Post::selectFirst(['id', 'uri-id', 'private', 'author-link', 'alias'], ['uri' => $item['thr-parent']]);
 564                                 if (!DBA::isResult($parent)) {
 565                                         Logger::warning('Unknown parent item.', ['uri' => $item['thr-parent']]);
 566                                         return false;
 567                                 }
 568                                 if ($item_private && ($parent['private'] != Item::PRIVATE)) {
 569                                         Logger::warning('Item is private but the parent is not. Dropping.', ['item-uri' => $item['uri'], 'thr-parent' => $item['thr-parent']]);
 570                                         return false;
 571                                 }
 572
 573                                 $content = self::removeImplicitMentionsFromBody($content, $parent);
 574                         }
 575                         $item['content-warning'] = HTML::toBBCode($activity['summary']);
 576                         $item['raw-body'] = $item['body'] = $content;
 577                 }
 578
 579                 self::storeFromBody($item);
 580                 self::storeTags($item['uri-id'], $activity['tags']);
 581
 582                 $item['location'] = $activity['location'];
 583
 584                 if (!empty($activity['latitude']) && !empty($activity['longitude'])) {
 585                         $item['coord'] = $activity['latitude'] . ' ' . $activity['longitude'];
 586                 }
 587
 588                 $item['app'] = $activity['generator'];
 589
 590                 return $item;
 591         }
 592
 593         /**
 594          * Store hashtags and mentions
 595          *
 596          * @param array $item
 597          */
 598         private static function storeFromBody(array $item)
 599         {
 600                 // Make sure to delete all existing tags (can happen when called via the update functionality)
 601                 DBA::delete('post-tag', ['uri-id' => $item['uri-id']]);
 602
 603                 Tag::storeFromBody($item['uri-id'], $item['body'], '@!');
 604         }
 605
 606         /**
 607          * Generate a GUID out of an URL
 608          *
 609          * @param string $url message URL
 610          * @return string with GUID
 611          */
 612         private static function getGUIDByURL(string $url)
 613         {
 614                 $parsed = parse_url($url);
 615
 616                 $host_hash = hash('crc32', $parsed['host']);
 617
 618                 unset($parsed["scheme"]);
 619                 unset($parsed["host"]);
 620
 621                 $path = implode("/", $parsed);
 622
 623                 return $host_hash . '-'. hash('fnv164', $path) . '-'. hash('joaat', $path);
 624         }
 625
 626         /**
 627          * Creates an item post
 628          *
 629          * @param array $activity Activity data
 630          * @param array $item     item array
 631          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 632          * @throws \ImagickException
 633          */
 634         public static function postItem(array $activity, array $item)
 635         {
 636                 if (empty($item)) {
 637                         return;
 638                 }
 639
 640                 $stored = false;
 641                 ksort($activity['receiver']);
 642
 643                 foreach ($activity['receiver'] as $receiver) {
 644                         if ($receiver == -1) {
 645                                 continue;
 646                         }
 647
 648                         $item['uid'] = $receiver;
 649
 650                         $type = $activity['reception_type'][$receiver] ?? Receiver::TARGET_UNKNOWN;
 651                         switch($type) {
 652                                 case Receiver::TARGET_TO:
 653                                         $item['post-reason'] = Item::PR_TO;
 654                                         break;
 655                                 case Receiver::TARGET_CC:
 656                                         $item['post-reason'] = Item::PR_CC;
 657                                         break;
 658                                 case Receiver::TARGET_BTO:
 659                                         $item['post-reason'] = Item::PR_BTO;
 660                                         break;
 661                                 case Receiver::TARGET_BCC:
 662                                         $item['post-reason'] = Item::PR_BCC;
 663                                         break;
 664                                 case Receiver::TARGET_FOLLOWER:
 665                                         $item['post-reason'] = Item::PR_FOLLOWER;
 666                                         break;
 667                                 case Receiver::TARGET_ANSWER:
 668                                         $item['post-reason'] = Item::PR_COMMENT;
 669                                         break;
 670                                 case Receiver::TARGET_GLOBAL:
 671                                         $item['post-reason'] = Item::PR_GLOBAL;
 672                                         break;
 673                                 default:
 674                                         $item['post-reason'] = Item::PR_NONE;
 675                         }
 676
 677                         if (!empty($activity['from-relay'])) {
 678                                 $item['post-reason'] = Item::PR_RELAY;
 679                         } elseif (!empty($activity['thread-completion'])) {
 680                                 $item['post-reason'] = Item::PR_FETCHED;
 681                         }
 682
 683                         if ($item['isForum'] ?? false) {
 684                                 $item['contact-id'] = Contact::getIdForURL($activity['actor'], $receiver);
 685                         } else {
 686                                 $item['contact-id'] = Contact::getIdForURL($activity['author'], $receiver);
 687                         }
 688
 689                         if (($receiver != 0) && empty($item['contact-id'])) {
 690                                 $item['contact-id'] = Contact::getIdForURL($activity['author']);
 691                         }
 692
 693                         if (!empty($activity['directmessage'])) {
 694                                 self::postMail($activity, $item);
 695                                 continue;
 696                         }
 697
 698                         if (DI::pConfig()->get($receiver, 'system', 'accept_only_sharer', false) && ($receiver != 0) && ($item['gravity'] == GRAVITY_PARENT)) {
 699                                 $skip = !Contact::isSharingByURL($activity['author'], $receiver);
 700
 701                                 if ($skip && (($activity['type'] == 'as:Announce') || ($item['isForum'] ?? false))) {
 702                                         $skip = !Contact::isSharingByURL($activity['actor'], $receiver);
 703                                 }
 704
 705                                 if ($skip) {
 706                                         Logger::info('Skipping post', ['uid' => $receiver, 'url' => $item['uri']]);
 707                                         continue;
 708                                 }
 709
 710                                 Logger::info('Accepting post', ['uid' => $receiver, 'url' => $item['uri']]);
 711                         }
 712
 713                         if (($item['gravity'] != GRAVITY_ACTIVITY) && ($activity['object_type'] == 'as:Event')) {
 714                                 self::createEvent($activity, $item);
 715                         }
 716
 717                         $item_id = Item::insert($item);
 718                         if ($item_id) {
 719                                 Logger::info('Item insertion successful', ['user' => $item['uid'], 'item_id' => $item_id]);
 720                         } else {
 721                                 Logger::notice('Item insertion aborted', ['user' => $item['uid']]);
 722                         }
 723
 724                         if ($item['uid'] == 0) {
 725                                 $stored = $item_id;
 726                         }
 727                 }
 728
 729                 // Store send a follow request for every reshare - but only when the item had been stored
 730                 if ($stored && ($item['private'] != Item::PRIVATE) && ($item['gravity'] == GRAVITY_PARENT) && ($item['author-link'] != $item['owner-link'])) {
 731                         $author = APContact::getByURL($item['owner-link'], false);
 732                         // We send automatic follow requests for reshared messages. (We don't need though for forum posts)
 733                         if ($author['type'] != 'Group') {
 734                                 Logger::info('Send follow request', ['uri' => $item['uri'], 'stored' => $stored, 'to' => $item['author-link']]);
 735                                 ActivityPub\Transmitter::sendFollowObject($item['uri'], $item['author-link']);
 736                         }
 737                 }
 738         }
 739
 740         /**
 741          * Store tags and mentions into the tag table
 742          *
 743          * @param integer $uriid
 744          * @param array $tags
 745          */
 746         private static function storeTags(int $uriid, array $tags = null)
 747         {
 748                 foreach ($tags as $tag) {
 749                         if (empty($tag['name']) || empty($tag['type']) || !in_array($tag['type'], ['Mention', 'Hashtag'])) {
 750                                 continue;
 751                         }
 752
 753                         $hash = substr($tag['name'], 0, 1);
 754
 755                         if ($tag['type'] == 'Mention') {
 756                                 if (in_array($hash, [Tag::TAG_CHARACTER[Tag::MENTION],
 757                                         Tag::TAG_CHARACTER[Tag::EXCLUSIVE_MENTION],
 758                                         Tag::TAG_CHARACTER[Tag::IMPLICIT_MENTION]])) {
 759                                         $tag['name'] = substr($tag['name'], 1);
 760                                 }
 761                                 $type = Tag::IMPLICIT_MENTION;
 762
 763                                 if (!empty($tag['href'])) {
 764                                         $apcontact = APContact::getByURL($tag['href']);
 765                                         if (!empty($apcontact['name']) || !empty($apcontact['nick'])) {
 766                                                 $tag['name'] = $apcontact['name'] ?: $apcontact['nick'];
 767                                         }
 768                                 }
 769                         } elseif ($tag['type'] == 'Hashtag') {
 770                                 if ($hash == Tag::TAG_CHARACTER[Tag::HASHTAG]) {
 771                                         $tag['name'] = substr($tag['name'], 1);
 772                                 }
 773                                 $type = Tag::HASHTAG;
 774                         }
 775
 776                         if (empty($tag['name'])) {
 777                                 continue;
 778                         }
 779
 780                         Tag::store($uriid, $type, $tag['name'], $tag['href']);
 781                 }
 782         }
 783
 784         /**
 785          * Creates an mail post
 786          *
 787          * @param array $activity Activity data
 788          * @param array $item     item array
 789          * @return int|bool New mail table row id or false on error
 790          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 791          */
 792         private static function postMail($activity, $item)
 793         {
 794                 if (($item['gravity'] != GRAVITY_PARENT) && !DBA::exists('mail', ['uri' => $item['thr-parent'], 'uid' => $item['uid']])) {
 795                         Logger::info('Parent not found, mail will be discarded.', ['uid' => $item['uid'], 'uri' => $item['thr-parent']]);
 796                         return false;
 797                 }
 798
 799                 Logger::info('Direct Message', $item);
 800
 801                 $msg = [];
 802                 $msg['uid'] = $item['uid'];
 803
 804                 $msg['contact-id'] = $item['contact-id'];
 805
 806                 $contact = Contact::getById($item['contact-id'], ['name', 'url', 'photo']);
 807                 $msg['from-name'] = $contact['name'];
 808                 $msg['from-url'] = $contact['url'];
 809                 $msg['from-photo'] = $contact['photo'];
 810
 811                 $msg['uri'] = $item['uri'];
 812                 $msg['created'] = $item['created'];
 813
 814                 $parent = DBA::selectFirst('mail', ['parent-uri', 'title'], ['uri' => $item['thr-parent']]);
 815                 if (DBA::isResult($parent)) {
 816                         $msg['parent-uri'] = $parent['parent-uri'];
 817                         $msg['title'] = $parent['title'];
 818                 } else {
 819                         $msg['parent-uri'] = $item['thr-parent'];
 820
 821                         if (!empty($item['title'])) {
 822                                 $msg['title'] = $item['title'];
 823                         } elseif (!empty($item['content-warning'])) {
 824                                 $msg['title'] = $item['content-warning'];
 825                         } else {
 826                                 // Trying to generate a title out of the body
 827                                 $title = $item['body'];
 828
 829                                 while (preg_match('#^(@\[url=([^\]]+)].*?\[\/url]\s)(.*)#is', $title, $matches)) {
 830                                         $title = $matches[3];
 831                                 }
 832
 833                                 $title = trim(HTML::toPlaintext(BBCode::convert($title, false, BBCode::API, true), 0));
 834
 835                                 if (strlen($title) > 20) {
 836                                         $title = substr($title, 0, 20) . '...';
 837                                 }
 838
 839                                 $msg['title'] = $title;
 840                         }
 841                 }
 842                 $msg['body'] = $item['body'];
 843
 844                 return Mail::insert($msg);
 845         }
 846
 847         /**
 848          * Fetches missing posts
 849          *
 850          * @param string $url         message URL
 851          * @param array  $child       activity array with the child of this message
 852          * @param string $relay_actor Relay actor
 853          * @return string fetched message URL
 854          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 855          */
 856         public static function fetchMissingActivity(string $url, array $child = [], string $relay_actor = '')
 857         {
 858                 if (!empty($child['receiver'])) {
 859                         $uid = ActivityPub\Receiver::getFirstUserFromReceivers($child['receiver']);
 860                 } else {
 861                         $uid = 0;
 862                 }
 863
 864                 $object = ActivityPub::fetchContent($url, $uid);
 865                 if (empty($object)) {
 866                         Logger::log('Activity ' . $url . ' was not fetchable, aborting.');
 867                         return '';
 868                 }
 869
 870                 if (empty($object['id'])) {
 871                         Logger::log('Activity ' . $url . ' has got not id, aborting. ' . json_encode($object));
 872                         return '';
 873                 }
 874
 875                 if (!empty($object['actor'])) {
 876                         $object_actor = $object['actor'];
 877                 } elseif (!empty($object['attributedTo'])) {
 878                         $object_actor = $object['attributedTo'];
 879                         if (is_array($object_actor)) {
 880                                 $compacted = JsonLD::compact($object);
 881                                 $object_actor = JsonLD::fetchElement($compacted, 'as:attributedTo', '@id');
 882                         }
 883                 } else {
 884                         // Shouldn't happen
 885                         $object_actor = '';
 886                 }
 887
 888                 $signer = [$object_actor];
 889
 890                 if (!empty($child['author'])) {
 891                         $actor = $child['author'];
 892                         $signer[] = $actor;
 893                 } else {
 894                         $actor = $object_actor;
 895                 }
 896
 897                 if (!empty($object['published'])) {
 898                         $published = $object['published'];
 899                 } elseif (!empty($child['published'])) {
 900                         $published = $child['published'];
 901                 } else {
 902                         $published = DateTimeFormat::utcNow();
 903                 }
 904
 905                 $activity = [];
 906                 $activity['@context'] = $object['@context'] ?? ActivityPub::CONTEXT;
 907                 unset($object['@context']);
 908                 $activity['id'] = $object['id'];
 909                 $activity['to'] = $object['to'] ?? [];
 910                 $activity['cc'] = $object['cc'] ?? [];
 911                 $activity['actor'] = $actor;
 912                 $activity['object'] = $object;
 913                 $activity['published'] = $published;
 914                 $activity['type'] = 'Create';
 915
 916                 $ldactivity = JsonLD::compact($activity);
 917
 918                 if (!empty($relay_actor)) {
 919                         $ldactivity['thread-completion'] = $ldactivity['from-relay'] = Contact::getIdForURL($relay_actor);
 920                 } elseif (!empty($child['thread-completion'])) {
 921                         $ldactivity['thread-completion'] = $child['thread-completion'];
 922                 } else {
 923                         $ldactivity['thread-completion'] = Contact::getIdForURL($actor);
 924                 }
 925
 926                 if (!empty($relay_actor) && !self::acceptIncomingMessage($ldactivity, $object['id'])) {
 927                         return '';
 928                 }
 929
 930                 ActivityPub\Receiver::processActivity($ldactivity, json_encode($activity), $uid, true, false, $signer);
 931
 932                 Logger::notice('Activity had been fetched and processed.', ['url' => $url, 'object' => $activity['id']]);
 933
 934                 return $activity['id'];
 935         }
 936
 937         /**
 938          * Test if incoming relay messages should be accepted
 939          *
 940          * @param array $activity activity array
 941          * @param string $id      object ID
 942          * @return boolean true if message is accepted
 943          */
 944         private static function acceptIncomingMessage(array $activity, string $id)
 945         {
 946                 if (empty($activity['as:object'])) {
 947                         Logger::info('No object field in activity - accepted', ['id' => $id]);
 948                         return true;
 949                 }
 950
 951                 $replyto = JsonLD::fetchElement($activity['as:object'], 'as:inReplyTo', '@id');
 952                 $uriid = ItemURI::getIdByURI($replyto);
 953                 if (Post::exists(['uri-id' => $uriid])) {
 954                         Logger::info('Post is a reply to an existing post - accepted', ['id' => $id, 'uri-id' => $uriid, 'replyto' => $replyto]);
 955                         return true;
 956                 }
 957
 958                 $attributed_to = JsonLD::fetchElement($activity['as:object'], 'as:attributedTo', '@id');
 959                 $authorid = Contact::getIdForURL($attributed_to);
 960
 961                 $body = HTML::toBBCode(JsonLD::fetchElement($activity['as:object'], 'as:content', '@value'));
 962
 963                 $messageTags = [];
 964                 $tags = Receiver::processTags(JsonLD::fetchElementArray($activity['as:object'], 'as:tag') ?? []);
 965                 if (!empty($tags)) {
 966                         foreach ($tags as $tag) {
 967                                 if ($tag['type'] != 'Hashtag') {
 968                                         continue;
 969                                 }
 970                                 $messageTags[] = ltrim(mb_strtolower($tag['name']), '#');
 971                         }
 972                 }
 973
 974                 return Relay::isSolicitedPost($messageTags, $body, $authorid, $id, Protocol::ACTIVITYPUB);
 975         }
 976
 977         /**
 978          * perform a "follow" request
 979          *
 980          * @param array $activity
 981          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 982          * @throws \ImagickException
 983          */
 984         public static function followUser($activity)
 985         {
 986                 $uid = User::getIdForURL($activity['object_id']);
 987                 if (empty($uid)) {
 988                         return;
 989                 }
 990
 991                 $owner = User::getOwnerDataById($uid);
 992                 if (empty($owner)) {
 993                         return;
 994                 }
 995
 996                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 997                 if (!empty($cid)) {
 998                         self::switchContact($cid);
 999                         DBA::update('contact', ['hub-verify' => $activity['id'], 'protocol' => Protocol::ACTIVITYPUB], ['id' => $cid]);
1000                 }
1001
1002                 $item = ['author-id' => Contact::getIdForURL($activity['actor']),
1003                         'author-link' => $activity['actor']];
1004
1005                 // Ensure that the contact has got the right network type
1006                 self::switchContact($item['author-id']);
1007
1008                 $result = Contact::addRelationship($owner, [], $item, false, $activity['content'] ?? '');
1009                 if ($result === true) {
1010                         ActivityPub\Transmitter::sendContactAccept($item['author-link'], $activity['id'], $owner['uid']);
1011                 }
1012
1013                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1014                 if (empty($cid)) {
1015                         return;
1016                 }
1017
1018                 if (empty($contact)) {
1019                         DBA::update('contact', ['hub-verify' => $activity['id'], 'protocol' => Protocol::ACTIVITYPUB], ['id' => $cid]);
1020                 }
1021
1022                 Logger::log('Follow user ' . $uid . ' from contact ' . $cid . ' with id ' . $activity['id']);
1023         }
1024
1025         /**
1026          * Update the given profile
1027          *
1028          * @param array $activity
1029          * @throws \Exception
1030          */
1031         public static function updatePerson($activity)
1032         {
1033                 if (empty($activity['object_id'])) {
1034                         return;
1035                 }
1036
1037                 Logger::info('Updating profile', ['object' => $activity['object_id']]);
1038                 Contact::updateFromProbeByURL($activity['object_id']);
1039         }
1040
1041         /**
1042          * Delete the given profile
1043          *
1044          * @param array $activity
1045          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1046          */
1047         public static function deletePerson($activity)
1048         {
1049                 if (empty($activity['object_id']) || empty($activity['actor'])) {
1050                         Logger::info('Empty object id or actor.');
1051                         return;
1052                 }
1053
1054                 if ($activity['object_id'] != $activity['actor']) {
1055                         Logger::info('Object id does not match actor.');
1056                         return;
1057                 }
1058
1059                 $contacts = DBA::select('contact', ['id'], ['nurl' => Strings::normaliseLink($activity['object_id'])]);
1060                 while ($contact = DBA::fetch($contacts)) {
1061                         Contact::remove($contact['id']);
1062                 }
1063                 DBA::close($contacts);
1064
1065                 Logger::info('Deleted contact', ['object' => $activity['object_id']]);
1066         }
1067
1068         /**
1069          * Accept a follow request
1070          *
1071          * @param array $activity
1072          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1073          * @throws \ImagickException
1074          */
1075         public static function acceptFollowUser($activity)
1076         {
1077                 $uid = User::getIdForURL($activity['object_actor']);
1078                 if (empty($uid)) {
1079                         return;
1080                 }
1081
1082                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1083                 if (empty($cid)) {
1084                         Logger::info('No contact found', ['actor' => $activity['actor']]);
1085                         return;
1086                 }
1087
1088                 self::switchContact($cid);
1089
1090                 $fields = ['pending' => false];
1091
1092                 $contact = DBA::selectFirst('contact', ['rel'], ['id' => $cid]);
1093                 if ($contact['rel'] == Contact::FOLLOWER) {
1094                         $fields['rel'] = Contact::FRIEND;
1095                 }
1096
1097                 $condition = ['id' => $cid];
1098                 DBA::update('contact', $fields, $condition);
1099                 Logger::info('Accept contact request', ['contact' => $cid, 'user' => $uid]);
1100         }
1101
1102         /**
1103          * Reject a follow request
1104          *
1105          * @param array $activity
1106          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1107          * @throws \ImagickException
1108          */
1109         public static function rejectFollowUser($activity)
1110         {
1111                 $uid = User::getIdForURL($activity['object_actor']);
1112                 if (empty($uid)) {
1113                         return;
1114                 }
1115
1116                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1117                 if (empty($cid)) {
1118                         Logger::info('No contact found', ['actor' => $activity['actor']]);
1119                         return;
1120                 }
1121
1122                 self::switchContact($cid);
1123
1124                 if (DBA::exists('contact', ['id' => $cid, 'rel' => Contact::SHARING])) {
1125                         Contact::remove($cid);
1126                         Logger::info('Rejected contact request - contact removed', ['contact' => $cid, 'user' => $uid]);
1127                 } else {
1128                         Logger::info('Rejected contact request', ['contact' => $cid, 'user' => $uid]);
1129                 }
1130         }
1131
1132         /**
1133          * Undo activity like "like" or "dislike"
1134          *
1135          * @param array $activity
1136          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1137          * @throws \ImagickException
1138          */
1139         public static function undoActivity($activity)
1140         {
1141                 if (empty($activity['object_id'])) {
1142                         return;
1143                 }
1144
1145                 if (empty($activity['object_actor'])) {
1146                         return;
1147                 }
1148
1149                 $author_id = Contact::getIdForURL($activity['object_actor']);
1150                 if (empty($author_id)) {
1151                         return;
1152                 }
1153
1154                 Item::markForDeletion(['uri' => $activity['object_id'], 'author-id' => $author_id, 'gravity' => GRAVITY_ACTIVITY]);
1155         }
1156
1157         /**
1158          * Activity to remove a follower
1159          *
1160          * @param array $activity
1161          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1162          * @throws \ImagickException
1163          */
1164         public static function undoFollowUser($activity)
1165         {
1166                 $uid = User::getIdForURL($activity['object_object']);
1167                 if (empty($uid)) {
1168                         return;
1169                 }
1170
1171                 $owner = User::getOwnerDataById($uid);
1172                 if (empty($owner)) {
1173                         return;
1174                 }
1175
1176                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1177                 if (empty($cid)) {
1178                         Logger::info('No contact found', ['actor' => $activity['actor']]);
1179                         return;
1180                 }
1181
1182                 self::switchContact($cid);
1183
1184                 $contact = DBA::selectFirst('contact', [], ['id' => $cid]);
1185                 if (!DBA::isResult($contact)) {
1186                         return;
1187                 }
1188
1189                 Contact::removeFollower($owner, $contact);
1190                 Logger::info('Undo following request', ['contact' => $cid, 'user' => $uid]);
1191         }
1192
1193         /**
1194          * Switches a contact to AP if needed
1195          *
1196          * @param integer $cid Contact ID
1197          * @throws \Exception
1198          */
1199         private static function switchContact($cid)
1200         {
1201                 $contact = DBA::selectFirst('contact', ['network', 'url'], ['id' => $cid]);
1202                 if (!DBA::isResult($contact) || in_array($contact['network'], [Protocol::ACTIVITYPUB, Protocol::DFRN]) || Contact::isLocal($contact['url'])) {
1203                         return;
1204                 }
1205
1206                 Logger::info('Change existing contact', ['cid' => $cid, 'previous' => $contact['network']]);
1207                 Contact::updateFromProbe($cid);
1208         }
1209
1210         /**
1211          * Collects implicit mentions like:
1212          * - the author of the parent item
1213          * - all the mentioned conversants in the parent item
1214          *
1215          * @param array $parent Item array with at least ['id', 'author-link', 'alias']
1216          * @return array
1217          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1218          */
1219         private static function getImplicitMentionList(array $parent)
1220         {
1221                 $parent_terms = Tag::getByURIId($parent['uri-id'], [Tag::MENTION, Tag::IMPLICIT_MENTION, Tag::EXCLUSIVE_MENTION]);
1222
1223                 $parent_author = Contact::getByURL($parent['author-link'], false, ['url', 'nurl', 'alias']);
1224
1225                 $implicit_mentions = [];
1226                 if (empty($parent_author['url'])) {
1227                         Logger::notice('Author public contact unknown.', ['author-link' => $parent['author-link'], 'parent-id' => $parent['id']]);
1228                 } else {
1229                         $implicit_mentions[] = $parent_author['url'];
1230                         $implicit_mentions[] = $parent_author['nurl'];
1231                         $implicit_mentions[] = $parent_author['alias'];
1232                 }
1233
1234                 if (!empty($parent['alias'])) {
1235                         $implicit_mentions[] = $parent['alias'];
1236                 }
1237
1238                 foreach ($parent_terms as $term) {
1239                         $contact = Contact::getByURL($term['url'], false, ['url', 'nurl', 'alias']);
1240                         if (!empty($contact['url'])) {
1241                                 $implicit_mentions[] = $contact['url'];
1242                                 $implicit_mentions[] = $contact['nurl'];
1243                                 $implicit_mentions[] = $contact['alias'];
1244                         }
1245                 }
1246
1247                 return $implicit_mentions;
1248         }
1249
1250         /**
1251          * Strips from the body prepended implicit mentions
1252          *
1253          * @param string $body
1254          * @param array $parent
1255          * @return string
1256          */
1257         private static function removeImplicitMentionsFromBody(string $body, array $parent)
1258         {
1259                 if (DI::config()->get('system', 'disable_implicit_mentions')) {
1260                         return $body;
1261                 }
1262
1263                 $potential_mentions = self::getImplicitMentionList($parent);
1264
1265                 $kept_mentions = [];
1266
1267                 // Extract one prepended mention at a time from the body
1268                 while(preg_match('#^(@\[url=([^\]]+)].*?\[\/url]\s)(.*)#is', $body, $matches)) {
1269                         if (!in_array($matches[2], $potential_mentions)) {
1270                                 $kept_mentions[] = $matches[1];
1271                         }
1272
1273                         $body = $matches[3];
1274                 }
1275
1276                 // Re-appending the kept mentions to the body after extraction
1277                 $kept_mentions[] = $body;
1278
1279                 return implode('', $kept_mentions);
1280         }
1281 }