src/Protocol/ActivityPub/Processor.php

   1 <?php
   2 /**
   3  * @copyright Copyright (C) 2010-2022, 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\Text\BBCode;
  25 use Friendica\Content\Text\HTML;
  26 use Friendica\Content\Text\Markdown;
  27 use Friendica\Core\Logger;
  28 use Friendica\Core\Protocol;
  29 use Friendica\Core\System;
  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          * Extracts the tag character (#, @, !) from mention links
  57          *
  58          * @param string $body
  59          * @return string
  60          */
  61         protected static function normalizeMentionLinks(string $body): string
  62         {
  63                 return preg_replace('%\[url=([^\[\]]*)]([#@!])(.*?)\[/url]%ism', '$2[url=$1]$3[/url]', $body);
  64         }
  65
  66         /**
  67          * Convert the language array into a language JSON
  68          *
  69          * @param array $languages
  70          * @return string language JSON
  71          */
  72         private static function processLanguages(array $languages)
  73         {
  74                 $codes = array_keys($languages);
  75                 $lang = [];
  76                 foreach ($codes as $code) {
  77                         $lang[$code] = 1;
  78                 }
  79
  80                 if (empty($lang)) {
  81                         return '';
  82                 }
  83
  84                 return json_encode($lang);
  85         }
  86         /**
  87          * Replaces emojis in the body
  88          *
  89          * @param array $emojis
  90          * @param string $body
  91          *
  92          * @return string with replaced emojis
  93          */
  94         private static function replaceEmojis(int $uri_id, $body, array $emojis)
  95         {
  96                 $body = strtr($body,
  97                         array_combine(
  98                                 array_column($emojis, 'name'),
  99                                 array_map(function ($emoji) {
 100                                         return '[emoji=' . $emoji['href'] . ']' . $emoji['name'] . '[/emoji]';
 101                                 }, $emojis)
 102                         )
 103                 );
 104
 105                 // We store the emoji here to be able to avoid storing it in the media
 106                 foreach ($emojis as $emoji) {
 107                         Post\Link::getByLink($uri_id, $emoji['href']);
 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'] ?? null;
 129                 $data['height'] = $attachment['height'] ?? null;
 130                 $data['width'] = $attachment['width'] ?? null;
 131                 $data['size'] = $attachment['size'] ?? null;
 132                 $data['preview'] = $attachment['image'] ?? null;
 133                 $data['description'] = $attachment['name'] ?? null;
 134
 135                 Post\Media::insert($data);
 136         }
 137
 138         /**
 139          * Stire attachment data
 140          *
 141          * @param array   $activity
 142          * @param array   $item
 143          */
 144         private static function storeAttachments($activity, $item)
 145         {
 146                 if (empty($activity['attachments'])) {
 147                         return;
 148                 }
 149
 150                 foreach ($activity['attachments'] as $attach) {
 151                         self::storeAttachmentAsMedia($item['uri-id'], $attach);
 152                 }
 153         }
 154
 155         /**
 156          * Updates a message
 157          *
 158          * @param array $activity Activity array
 159          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 160          */
 161         public static function updateItem($activity)
 162         {
 163                 $item = Post::selectFirst(['uri', 'uri-id', 'thr-parent', 'gravity', 'post-type'], ['uri' => $activity['id']]);
 164                 if (!DBA::isResult($item)) {
 165                         Logger::warning('No existing item, item will be created', ['uri' => $activity['id']]);
 166                         $item = self::createItem($activity);
 167                         self::postItem($activity, $item);
 168                         return;
 169                 }
 170
 171                 $item['changed'] = DateTimeFormat::utcNow();
 172                 $item['edited'] = DateTimeFormat::utc($activity['updated']);
 173
 174                 $item = self::processContent($activity, $item);
 175
 176                 self::storeAttachments($activity, $item);
 177
 178                 if (empty($item)) {
 179                         return;
 180                 }
 181
 182                 Item::update($item, ['uri' => $activity['id']]);
 183
 184                 if ($activity['object_type'] == 'as:Event') {
 185                         $posts = Post::select(['event-id', 'uid'], ["`uri` = ? AND `event-id` > ?", $activity['id'], 0]);
 186                         while ($post = DBA::fetch($posts)) {
 187                                 self::updateEvent($post['event-id'], $activity);
 188                         }
 189                 }
 190         }
 191
 192         /**
 193          * Update an existing event
 194          *
 195          * @param int $event_id
 196          * @param array $activity
 197          */
 198         private static function updateEvent(int $event_id, array $activity)
 199         {
 200                 $event = DBA::selectFirst('event', [], ['id' => $event_id]);
 201
 202                 $event['edited']   = DateTimeFormat::utc($activity['updated']);
 203                 $event['summary']  = HTML::toBBCode($activity['name']);
 204                 $event['desc']     = HTML::toBBCode($activity['content']);
 205                 $event['start']    = $activity['start-time'];
 206                 $event['finish']   = $activity['end-time'];
 207                 $event['nofinish'] = empty($event['finish']);
 208                 $event['location'] = $activity['location'];
 209
 210                 Logger::info('Updating event', ['uri' => $activity['id'], 'id' => $event_id]);
 211                 Event::store($event);
 212         }
 213
 214         /**
 215          * Prepares data for a message
 216          *
 217          * @param array $activity Activity array
 218          * @return array Internal item
 219          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 220          * @throws \ImagickException
 221          */
 222         public static function createItem($activity)
 223         {
 224                 $item = [];
 225                 $item['verb'] = Activity::POST;
 226                 $item['thr-parent'] = $activity['reply-to-id'];
 227
 228                 if ($activity['reply-to-id'] == $activity['id']) {
 229                         $item['gravity'] = GRAVITY_PARENT;
 230                         $item['object-type'] = Activity\ObjectType::NOTE;
 231                 } else {
 232                         $item['gravity'] = GRAVITY_COMMENT;
 233                         $item['object-type'] = Activity\ObjectType::COMMENT;
 234                 }
 235
 236                 if (empty($activity['directmessage']) && ($activity['id'] != $activity['reply-to-id']) && !Post::exists(['uri' => $activity['reply-to-id']])) {
 237                         Logger::notice('Parent not found. Try to refetch it.', ['parent' => $activity['reply-to-id']]);
 238                         self::fetchMissingActivity($activity['reply-to-id'], $activity);
 239                 }
 240
 241                 $item['diaspora_signed_text'] = $activity['diaspora:comment'] ?? '';
 242
 243                 /// @todo What to do with $activity['context']?
 244                 if (empty($activity['directmessage']) && ($item['gravity'] != GRAVITY_PARENT) && !Post::exists(['uri' => $item['thr-parent']])) {
 245                         Logger::info('Parent not found, message will be discarded.', ['thr-parent' => $item['thr-parent']]);
 246                         return [];
 247                 }
 248
 249                 $item['network'] = Protocol::ACTIVITYPUB;
 250                 $item['author-link'] = $activity['author'];
 251                 $item['author-id'] = Contact::getIdForURL($activity['author']);
 252                 $item['owner-link'] = $activity['actor'];
 253                 $item['owner-id'] = Contact::getIdForURL($activity['actor']);
 254
 255                 if (in_array(0, $activity['receiver']) && !empty($activity['unlisted'])) {
 256                         $item['private'] = Item::UNLISTED;
 257                 } elseif (in_array(0, $activity['receiver'])) {
 258                         $item['private'] = Item::PUBLIC;
 259                 } else {
 260                         $item['private'] = Item::PRIVATE;
 261                 }
 262
 263                 if (!empty($activity['raw'])) {
 264                         $item['source'] = $activity['raw'];
 265                         $item['protocol'] = Conversation::PARCEL_ACTIVITYPUB;
 266                         $item['conversation-href'] = $activity['context'] ?? '';
 267                         $item['conversation-uri'] = $activity['conversation'] ?? '';
 268
 269                         if (isset($activity['push'])) {
 270                                 $item['direction'] = $activity['push'] ? Conversation::PUSH : Conversation::PULL;
 271                         }
 272                 }
 273
 274                 if (!empty($activity['from-relay'])) {
 275                         $item['direction'] = Conversation::RELAY;
 276                 }
 277
 278                 if ($activity['object_type'] == 'as:Article') {
 279                         $item['post-type'] = Item::PT_ARTICLE;
 280                 } elseif ($activity['object_type'] == 'as:Audio') {
 281                         $item['post-type'] = Item::PT_AUDIO;
 282                 } elseif ($activity['object_type'] == 'as:Document') {
 283                         $item['post-type'] = Item::PT_DOCUMENT;
 284                 } elseif ($activity['object_type'] == 'as:Event') {
 285                         $item['post-type'] = Item::PT_EVENT;
 286                 } elseif ($activity['object_type'] == 'as:Image') {
 287                         $item['post-type'] = Item::PT_IMAGE;
 288                 } elseif ($activity['object_type'] == 'as:Page') {
 289                         $item['post-type'] = Item::PT_PAGE;
 290                 } elseif ($activity['object_type'] == 'as:Question') {
 291                         $item['post-type'] = Item::PT_POLL;
 292                 } elseif ($activity['object_type'] == 'as:Video') {
 293                         $item['post-type'] = Item::PT_VIDEO;
 294                 } else {
 295                         $item['post-type'] = Item::PT_NOTE;
 296                 }
 297
 298                 $item['isForum'] = false;
 299
 300                 if (!empty($activity['thread-completion'])) {
 301                         if ($activity['thread-completion'] != $item['owner-id']) {
 302                                 $actor = Contact::getById($activity['thread-completion'], ['url']);
 303                                 $item['causer-link'] = $actor['url'];
 304                                 $item['causer-id'] = $activity['thread-completion'];
 305                                 Logger::info('Use inherited actor as causer.', ['id' => $item['owner-id'], 'activity' => $activity['thread-completion'], 'owner' => $item['owner-link'], 'actor' => $actor['url']]);
 306                         } else {
 307                                 // Store the original actor in the "causer" fields to enable the check for ignored or blocked contacts
 308                                 $item['causer-link'] = $item['owner-link'];
 309                                 $item['causer-id']   = $item['owner-id'];
 310                                 Logger::info('Use actor as causer.', ['id' => $item['owner-id'], 'actor' => $item['owner-link']]);
 311                         }
 312
 313                         $item['owner-link'] = $item['author-link'];
 314                         $item['owner-id'] = $item['author-id'];
 315                 } else {
 316                         $actor = APContact::getByURL($item['owner-link'], false);
 317                         $item['isForum'] = ($actor['type'] == 'Group');
 318                 }
 319
 320                 $item['uri'] = $activity['id'];
 321
 322                 if (empty($activity['published']) || empty($activity['updated'])) {
 323                         DI::logger()->notice('published or updated keys are empty for activity', ['activity' => $activity, 'callstack' => System::callstack(10)]);
 324                 }
 325
 326                 $item['created'] = DateTimeFormat::utc($activity['published'] ?? 'now');
 327                 $item['edited'] = DateTimeFormat::utc($activity['updated'] ?? 'now');
 328                 $guid = $activity['sc:identifier'] ?: self::getGUIDByURL($item['uri']);
 329                 $item['guid'] = $activity['diaspora:guid'] ?: $guid;
 330
 331                 $item['uri-id'] = ItemURI::insert(['uri' => $item['uri'], 'guid' => $item['guid']]);
 332                 if (empty($item['uri-id'])) {
 333                         Logger::warning('Unable to get a uri-id for an item uri', ['uri' => $item['uri'], 'guid' => $item['guid']]);
 334                         return [];
 335                 }
 336
 337                 $item = self::processContent($activity, $item);
 338                 if (empty($item)) {
 339                         Logger::info('Message was not processed');
 340                         return [];
 341                 }
 342
 343                 $item['plink'] = $activity['alternate-url'] ?? $item['uri'];
 344
 345                 self::storeAttachments($activity, $item);
 346
 347                 // We received the post via AP, so we set the protocol of the server to AP
 348                 $contact = Contact::getById($item['author-id'], ['gsid']);
 349                 if (!empty($contact['gsid'])) {
 350                         GServer::setProtocol($contact['gsid'], Post\DeliveryData::ACTIVITYPUB);
 351                 }
 352
 353                 if ($item['author-id'] != $item['owner-id']) {
 354                         $contact = Contact::getById($item['owner-id'], ['gsid']);
 355                         if (!empty($contact['gsid'])) {
 356                                 GServer::setProtocol($contact['gsid'], Post\DeliveryData::ACTIVITYPUB);
 357                         }
 358                 }
 359
 360                 return $item;
 361         }
 362
 363         /**
 364          * Delete items
 365          *
 366          * @param array $activity
 367          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 368          * @throws \ImagickException
 369          */
 370         public static function deleteItem($activity)
 371         {
 372                 $owner = Contact::getIdForURL($activity['actor']);
 373
 374                 Logger::info('Deleting item', ['object' => $activity['object_id'], 'owner'  => $owner]);
 375                 Item::markForDeletion(['uri' => $activity['object_id'], 'owner-id' => $owner]);
 376         }
 377
 378         /**
 379          * Prepare the item array for an activity
 380          *
 381          * @param array $activity Activity array
 382          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 383          * @throws \ImagickException
 384          */
 385         public static function addTag($activity)
 386         {
 387                 if (empty($activity['object_content']) || empty($activity['object_id'])) {
 388                         return;
 389                 }
 390
 391                 foreach ($activity['receiver'] as $receiver) {
 392                         $item = Post::selectFirst(['id', 'uri-id', 'origin', 'author-link'], ['uri' => $activity['target_id'], 'uid' => $receiver]);
 393                         if (!DBA::isResult($item)) {
 394                                 // We don't fetch missing content for this purpose
 395                                 continue;
 396                         }
 397
 398                         if (($item['author-link'] != $activity['actor']) && !$item['origin']) {
 399                                 Logger::info('Not origin, not from the author, skipping update', ['id' => $item['id'], 'author' => $item['author-link'], 'actor' => $activity['actor']]);
 400                                 continue;
 401                         }
 402
 403                         Tag::store($item['uri-id'], Tag::HASHTAG, $activity['object_content'], $activity['object_id']);
 404                         Logger::info('Tagged item', ['id' => $item['id'], 'tag' => $activity['object_content'], 'uri' => $activity['target_id'], 'actor' => $activity['actor']]);
 405                 }
 406         }
 407
 408         /**
 409          * Prepare the item array for an activity
 410          *
 411          * @param array  $activity Activity array
 412          * @param string $verb     Activity verb
 413          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 414          * @throws \ImagickException
 415          */
 416         public static function createActivity($activity, $verb)
 417         {
 418                 $item = self::createItem($activity);
 419                 $item['verb'] = $verb;
 420                 $item['thr-parent'] = $activity['object_id'];
 421                 $item['gravity'] = GRAVITY_ACTIVITY;
 422                 unset($item['post-type']);
 423                 $item['object-type'] = Activity\ObjectType::NOTE;
 424
 425                 $item['diaspora_signed_text'] = $activity['diaspora:like'] ?? '';
 426
 427                 self::postItem($activity, $item);
 428         }
 429
 430         /**
 431          * Create an event
 432          *
 433          * @param array $activity Activity array
 434          * @param array $item
 435          *
 436          * @return int event id
 437          * @throws \Exception
 438          */
 439         public static function createEvent($activity, $item)
 440         {
 441                 $event['summary']   = HTML::toBBCode($activity['name']);
 442                 $event['desc']      = HTML::toBBCode($activity['content']);
 443                 $event['start']     = $activity['start-time'];
 444                 $event['finish']    = $activity['end-time'];
 445                 $event['nofinish']  = empty($event['finish']);
 446                 $event['location']  = $activity['location'];
 447                 $event['cid']       = $item['contact-id'];
 448                 $event['uid']       = $item['uid'];
 449                 $event['uri']       = $item['uri'];
 450                 $event['edited']    = $item['edited'];
 451                 $event['private']   = $item['private'];
 452                 $event['guid']      = $item['guid'];
 453                 $event['plink']     = $item['plink'];
 454                 $event['network']   = $item['network'];
 455                 $event['protocol']  = $item['protocol'];
 456                 $event['direction'] = $item['direction'];
 457                 $event['source']    = $item['source'];
 458
 459                 $ev = DBA::selectFirst('event', ['id'], ['uri' => $item['uri'], 'uid' => $item['uid']]);
 460                 if (DBA::isResult($ev)) {
 461                         $event['id'] = $ev['id'];
 462                 }
 463
 464                 $event_id = Event::store($event);
 465
 466                 Logger::info('Event was stored', ['id' => $event_id]);
 467
 468                 return $event_id;
 469         }
 470
 471         /**
 472          * Process the content
 473          *
 474          * @param array $activity Activity array
 475          * @param array $item
 476          * @return array|bool Returns the item array or false if there was an unexpected occurrence
 477          * @throws \Exception
 478          */
 479         private static function processContent($activity, $item)
 480         {
 481                 if (!empty($activity['mediatype']) && ($activity['mediatype'] == 'text/markdown')) {
 482                         $item['title'] = Markdown::toBBCode($activity['name']);
 483                         $content = Markdown::toBBCode($activity['content']);
 484                 } elseif (!empty($activity['mediatype']) && ($activity['mediatype'] == 'text/bbcode')) {
 485                         $item['title'] = $activity['name'];
 486                         $content = $activity['content'];
 487                 } else {
 488                         // By default assume "text/html"
 489                         $item['title'] = HTML::toBBCode($activity['name']);
 490                         $content = HTML::toBBCode($activity['content']);
 491                 }
 492
 493                 if (!empty($activity['languages'])) {
 494                         $item['language'] = self::processLanguages($activity['languages']);
 495                 }
 496
 497                 if (!empty($activity['emojis'])) {
 498                         $content = self::replaceEmojis($item['uri-id'], $content, $activity['emojis']);
 499                 }
 500
 501                 $content = self::addMentionLinks($content, $activity['tags']);
 502
 503                 if (!empty($activity['source'])) {
 504                         $item['body'] = $activity['source'];
 505                         $item['raw-body'] = $content;
 506                         $item['body'] = Item::improveSharedDataInBody($item);
 507                 } else {
 508                         if (empty($activity['directmessage']) && ($item['thr-parent'] != $item['uri']) && ($item['gravity'] == GRAVITY_COMMENT)) {
 509                                 $item_private = !in_array(0, $activity['item_receiver']);
 510                                 $parent = Post::selectFirst(['id', 'uri-id', 'private', 'author-link', 'alias'], ['uri' => $item['thr-parent']]);
 511                                 if (!DBA::isResult($parent)) {
 512                                         Logger::warning('Unknown parent item.', ['uri' => $item['thr-parent']]);
 513                                         return false;
 514                                 }
 515                                 if ($item_private && ($parent['private'] != Item::PRIVATE)) {
 516                                         Logger::warning('Item is private but the parent is not. Dropping.', ['item-uri' => $item['uri'], 'thr-parent' => $item['thr-parent']]);
 517                                         return false;
 518                                 }
 519
 520                                 $content = self::removeImplicitMentionsFromBody($content, $parent);
 521                         }
 522                         $item['content-warning'] = HTML::toBBCode($activity['summary']);
 523                         $item['raw-body'] = $item['body'] = $content;
 524                 }
 525
 526                 self::storeFromBody($item);
 527                 self::storeTags($item['uri-id'], $activity['tags']);
 528
 529                 $item['location'] = $activity['location'];
 530
 531                 if (!empty($activity['latitude']) && !empty($activity['longitude'])) {
 532                         $item['coord'] = $activity['latitude'] . ' ' . $activity['longitude'];
 533                 }
 534
 535                 $item['app'] = $activity['generator'];
 536
 537                 return $item;
 538         }
 539
 540         /**
 541          * Store hashtags and mentions
 542          *
 543          * @param array $item
 544          */
 545         private static function storeFromBody(array $item)
 546         {
 547                 // Make sure to delete all existing tags (can happen when called via the update functionality)
 548                 DBA::delete('post-tag', ['uri-id' => $item['uri-id']]);
 549
 550                 Tag::storeFromBody($item['uri-id'], $item['body'], '@!');
 551         }
 552
 553         /**
 554          * Generate a GUID out of an URL
 555          *
 556          * @param string $url message URL
 557          * @return string with GUID
 558          */
 559         private static function getGUIDByURL(string $url)
 560         {
 561                 $parsed = parse_url($url);
 562
 563                 $host_hash = hash('crc32', $parsed['host']);
 564
 565                 unset($parsed["scheme"]);
 566                 unset($parsed["host"]);
 567
 568                 $path = implode("/", $parsed);
 569
 570                 return $host_hash . '-'. hash('fnv164', $path) . '-'. hash('joaat', $path);
 571         }
 572
 573         /**
 574          * Creates an item post
 575          *
 576          * @param array $activity Activity data
 577          * @param array $item     item array
 578          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 579          * @throws \ImagickException
 580          */
 581         public static function postItem(array $activity, array $item)
 582         {
 583                 if (empty($item)) {
 584                         return;
 585                 }
 586
 587                 $stored = false;
 588                 ksort($activity['receiver']);
 589
 590                 foreach ($activity['receiver'] as $receiver) {
 591                         if ($receiver == -1) {
 592                                 continue;
 593                         }
 594
 595                         $item['uid'] = $receiver;
 596
 597                         $type = $activity['reception_type'][$receiver] ?? Receiver::TARGET_UNKNOWN;
 598                         switch($type) {
 599                                 case Receiver::TARGET_TO:
 600                                         $item['post-reason'] = Item::PR_TO;
 601                                         break;
 602                                 case Receiver::TARGET_CC:
 603                                         $item['post-reason'] = Item::PR_CC;
 604                                         break;
 605                                 case Receiver::TARGET_BTO:
 606                                         $item['post-reason'] = Item::PR_BTO;
 607                                         break;
 608                                 case Receiver::TARGET_BCC:
 609                                         $item['post-reason'] = Item::PR_BCC;
 610                                         break;
 611                                 case Receiver::TARGET_FOLLOWER:
 612                                         $item['post-reason'] = Item::PR_FOLLOWER;
 613                                         break;
 614                                 case Receiver::TARGET_ANSWER:
 615                                         $item['post-reason'] = Item::PR_COMMENT;
 616                                         break;
 617                                 case Receiver::TARGET_GLOBAL:
 618                                         $item['post-reason'] = Item::PR_GLOBAL;
 619                                         break;
 620                                 default:
 621                                         $item['post-reason'] = Item::PR_NONE;
 622                         }
 623
 624                         if (!empty($activity['from-relay'])) {
 625                                 $item['post-reason'] = Item::PR_RELAY;
 626                         } elseif (!empty($activity['thread-completion'])) {
 627                                 $item['post-reason'] = Item::PR_FETCHED;
 628                         }
 629
 630                         if ($item['isForum'] ?? false) {
 631                                 $item['contact-id'] = Contact::getIdForURL($activity['actor'], $receiver);
 632                         } else {
 633                                 $item['contact-id'] = Contact::getIdForURL($activity['author'], $receiver);
 634                         }
 635
 636                         if (($receiver != 0) && empty($item['contact-id'])) {
 637                                 $item['contact-id'] = Contact::getIdForURL($activity['author']);
 638                         }
 639
 640                         if (!empty($activity['directmessage'])) {
 641                                 self::postMail($activity, $item);
 642                                 continue;
 643                         }
 644
 645                         if (!($item['isForum'] ?? false) && ($receiver != 0) && ($item['gravity'] == GRAVITY_PARENT) && !Contact::isSharingByURL($activity['author'], $receiver)) {
 646                                 if ($item['post-reason'] == Item::PR_BCC) {
 647                                         Logger::info('Top level post via BCC from a non sharer, ignoring', ['uid' => $receiver, 'contact' => $item['contact-id']]);
 648                                         continue;
 649                                 }
 650                                 if (!empty($activity['thread-children-type']) && in_array($activity['thread-children-type'], Receiver::ACTIVITY_TYPES)) {
 651                                         Logger::info('Top level post from thread completion from a non sharer had been initiated via an activity, ignoring',
 652                                                 ['type' => $activity['thread-children-type'], 'user' => $item['uid'], 'causer' => $item['causer-link'], 'author' => $activity['author'], 'url' => $item['uri']]);
 653                                         continue;
 654                                 }
 655                         }
 656
 657                         $is_forum = false;
 658
 659                         if ($receiver != 0) {
 660                                 $user = User::getById($receiver, ['account-type']);
 661                                 if (!empty($user['account-type'])) {
 662                                         $is_forum = ($user['account-type'] == User::ACCOUNT_TYPE_COMMUNITY);
 663                                 }
 664                         }
 665
 666                         if (!$is_forum && DI::pConfig()->get($receiver, 'system', 'accept_only_sharer', false) && ($receiver != 0) && ($item['gravity'] == GRAVITY_PARENT)) {
 667                                 $skip = !Contact::isSharingByURL($activity['author'], $receiver);
 668
 669                                 if ($skip && (($activity['type'] == 'as:Announce') || ($item['isForum'] ?? false))) {
 670                                         $skip = !Contact::isSharingByURL($activity['actor'], $receiver);
 671                                 }
 672
 673                                 if ($skip) {
 674                                         Logger::info('Skipping post', ['uid' => $receiver, 'url' => $item['uri']]);
 675                                         continue;
 676                                 }
 677
 678                                 Logger::info('Accepting post', ['uid' => $receiver, 'url' => $item['uri']]);
 679                         }
 680
 681                         if (($item['gravity'] != GRAVITY_ACTIVITY) && ($activity['object_type'] == 'as:Event')) {
 682                                 $event_id = self::createEvent($activity, $item);
 683
 684                                 $item = Event::getItemArrayForImportedId($event_id, $item);
 685                         }
 686
 687                         $item_id = Item::insert($item);
 688                         if ($item_id) {
 689                                 Logger::info('Item insertion successful', ['user' => $item['uid'], 'item_id' => $item_id]);
 690                         } else {
 691                                 Logger::notice('Item insertion aborted', ['user' => $item['uid']]);
 692                         }
 693
 694                         if ($item['uid'] == 0) {
 695                                 $stored = $item_id;
 696                         }
 697                 }
 698
 699                 // Store send a follow request for every reshare - but only when the item had been stored
 700                 if ($stored && ($item['private'] != Item::PRIVATE) && ($item['gravity'] == GRAVITY_PARENT) && ($item['author-link'] != $item['owner-link'])) {
 701                         $author = APContact::getByURL($item['owner-link'], false);
 702                         // We send automatic follow requests for reshared messages. (We don't need though for forum posts)
 703                         if ($author['type'] != 'Group') {
 704                                 Logger::info('Send follow request', ['uri' => $item['uri'], 'stored' => $stored, 'to' => $item['author-link']]);
 705                                 ActivityPub\Transmitter::sendFollowObject($item['uri'], $item['author-link']);
 706                         }
 707                 }
 708         }
 709
 710         /**
 711          * Store tags and mentions into the tag table
 712          *
 713          * @param integer $uriid
 714          * @param array $tags
 715          */
 716         private static function storeTags(int $uriid, array $tags = null)
 717         {
 718                 foreach ($tags as $tag) {
 719                         if (empty($tag['name']) || empty($tag['type']) || !in_array($tag['type'], ['Mention', 'Hashtag'])) {
 720                                 continue;
 721                         }
 722
 723                         $hash = substr($tag['name'], 0, 1);
 724
 725                         if ($tag['type'] == 'Mention') {
 726                                 if (in_array($hash, [Tag::TAG_CHARACTER[Tag::MENTION],
 727                                         Tag::TAG_CHARACTER[Tag::EXCLUSIVE_MENTION],
 728                                         Tag::TAG_CHARACTER[Tag::IMPLICIT_MENTION]])) {
 729                                         $tag['name'] = substr($tag['name'], 1);
 730                                 }
 731                                 $type = Tag::IMPLICIT_MENTION;
 732
 733                                 if (!empty($tag['href'])) {
 734                                         $apcontact = APContact::getByURL($tag['href']);
 735                                         if (!empty($apcontact['name']) || !empty($apcontact['nick'])) {
 736                                                 $tag['name'] = $apcontact['name'] ?: $apcontact['nick'];
 737                                         }
 738                                 }
 739                         } elseif ($tag['type'] == 'Hashtag') {
 740                                 if ($hash == Tag::TAG_CHARACTER[Tag::HASHTAG]) {
 741                                         $tag['name'] = substr($tag['name'], 1);
 742                                 }
 743                                 $type = Tag::HASHTAG;
 744                         }
 745
 746                         if (empty($tag['name'])) {
 747                                 continue;
 748                         }
 749
 750                         Tag::store($uriid, $type, $tag['name'], $tag['href']);
 751                 }
 752         }
 753
 754         /**
 755          * Creates an mail post
 756          *
 757          * @param array $activity Activity data
 758          * @param array $item     item array
 759          * @return int|bool New mail table row id or false on error
 760          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 761          */
 762         private static function postMail($activity, $item)
 763         {
 764                 if (($item['gravity'] != GRAVITY_PARENT) && !DBA::exists('mail', ['uri' => $item['thr-parent'], 'uid' => $item['uid']])) {
 765                         Logger::info('Parent not found, mail will be discarded.', ['uid' => $item['uid'], 'uri' => $item['thr-parent']]);
 766                         return false;
 767                 }
 768
 769                 Logger::info('Direct Message', $item);
 770
 771                 $msg = [];
 772                 $msg['uid'] = $item['uid'];
 773
 774                 $msg['contact-id'] = $item['contact-id'];
 775
 776                 $contact = Contact::getById($item['contact-id'], ['name', 'url', 'photo']);
 777                 $msg['from-name'] = $contact['name'];
 778                 $msg['from-url'] = $contact['url'];
 779                 $msg['from-photo'] = $contact['photo'];
 780
 781                 $msg['uri'] = $item['uri'];
 782                 $msg['created'] = $item['created'];
 783
 784                 $parent = DBA::selectFirst('mail', ['parent-uri', 'title'], ['uri' => $item['thr-parent']]);
 785                 if (DBA::isResult($parent)) {
 786                         $msg['parent-uri'] = $parent['parent-uri'];
 787                         $msg['title'] = $parent['title'];
 788                 } else {
 789                         $msg['parent-uri'] = $item['thr-parent'];
 790
 791                         if (!empty($item['title'])) {
 792                                 $msg['title'] = $item['title'];
 793                         } elseif (!empty($item['content-warning'])) {
 794                                 $msg['title'] = $item['content-warning'];
 795                         } else {
 796                                 // Trying to generate a title out of the body
 797                                 $title = $item['body'];
 798
 799                                 while (preg_match('#^(@\[url=([^\]]+)].*?\[\/url]\s)(.*)#is', $title, $matches)) {
 800                                         $title = $matches[3];
 801                                 }
 802
 803                                 $title = trim(BBCode::toPlaintext($title));
 804
 805                                 if (strlen($title) > 20) {
 806                                         $title = substr($title, 0, 20) . '...';
 807                                 }
 808
 809                                 $msg['title'] = $title;
 810                         }
 811                 }
 812                 $msg['body'] = $item['body'];
 813
 814                 return Mail::insert($msg);
 815         }
 816
 817         /**
 818          * Fetches missing posts
 819          *
 820          * @param string $url         message URL
 821          * @param array  $child       activity array with the child of this message
 822          * @param string $relay_actor Relay actor
 823          * @return string fetched message URL
 824          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 825          */
 826         public static function fetchMissingActivity(string $url, array $child = [], string $relay_actor = '')
 827         {
 828                 if (!empty($child['receiver'])) {
 829                         $uid = ActivityPub\Receiver::getFirstUserFromReceivers($child['receiver']);
 830                 } else {
 831                         $uid = 0;
 832                 }
 833
 834                 $object = ActivityPub::fetchContent($url, $uid);
 835                 if (empty($object)) {
 836                         Logger::notice('Activity was not fetchable, aborting.', ['url' => $url]);
 837                         return '';
 838                 }
 839
 840                 if (empty($object['id'])) {
 841                         Logger::notice('Activity has got not id, aborting. ', ['url' => $url, 'object' => $object]);
 842                         return '';
 843                 }
 844
 845                 if (!empty($object['actor'])) {
 846                         $object_actor = $object['actor'];
 847                 } elseif (!empty($object['attributedTo'])) {
 848                         $object_actor = $object['attributedTo'];
 849                         if (is_array($object_actor)) {
 850                                 $compacted = JsonLD::compact($object);
 851                                 $object_actor = JsonLD::fetchElement($compacted, 'as:attributedTo', '@id');
 852                         }
 853                 } else {
 854                         // Shouldn't happen
 855                         $object_actor = '';
 856                 }
 857
 858                 $signer = [$object_actor];
 859
 860                 if (!empty($child['author'])) {
 861                         $actor = $child['author'];
 862                         $signer[] = $actor;
 863                 } else {
 864                         $actor = $object_actor;
 865                 }
 866
 867                 if (!empty($object['published'])) {
 868                         $published = $object['published'];
 869                 } elseif (!empty($child['published'])) {
 870                         $published = $child['published'];
 871                 } else {
 872                         $published = DateTimeFormat::utcNow();
 873                 }
 874
 875                 $activity = [];
 876                 $activity['@context'] = $object['@context'] ?? ActivityPub::CONTEXT;
 877                 unset($object['@context']);
 878                 $activity['id'] = $object['id'];
 879                 $activity['to'] = $object['to'] ?? [];
 880                 $activity['cc'] = $object['cc'] ?? [];
 881                 $activity['actor'] = $actor;
 882                 $activity['object'] = $object;
 883                 $activity['published'] = $published;
 884                 $activity['type'] = 'Create';
 885
 886                 $ldactivity = JsonLD::compact($activity);
 887
 888                 if (!empty($relay_actor)) {
 889                         $ldactivity['thread-completion'] = $ldactivity['from-relay'] = Contact::getIdForURL($relay_actor);
 890                 } elseif (!empty($child['thread-completion'])) {
 891                         $ldactivity['thread-completion'] = $child['thread-completion'];
 892                 } else {
 893                         $ldactivity['thread-completion'] = Contact::getIdForURL($actor);
 894                 }
 895
 896                 if (!empty($child['type'])) {
 897                         $ldactivity['thread-children-type'] = $child['type'];
 898                 }
 899
 900                 if (!empty($relay_actor) && !self::acceptIncomingMessage($ldactivity, $object['id'])) {
 901                         return '';
 902                 }
 903
 904                 ActivityPub\Receiver::processActivity($ldactivity, json_encode($activity), $uid, true, false, $signer);
 905
 906                 Logger::notice('Activity had been fetched and processed.', ['url' => $url, 'object' => $activity['id']]);
 907
 908                 return $activity['id'];
 909         }
 910
 911         /**
 912          * Test if incoming relay messages should be accepted
 913          *
 914          * @param array $activity activity array
 915          * @param string $id      object ID
 916          * @return boolean true if message is accepted
 917          */
 918         private static function acceptIncomingMessage(array $activity, string $id)
 919         {
 920                 if (empty($activity['as:object'])) {
 921                         Logger::info('No object field in activity - accepted', ['id' => $id]);
 922                         return true;
 923                 }
 924
 925                 $replyto = JsonLD::fetchElement($activity['as:object'], 'as:inReplyTo', '@id');
 926                 $uriid = ItemURI::getIdByURI($replyto);
 927                 if (Post::exists(['uri-id' => $uriid])) {
 928                         Logger::info('Post is a reply to an existing post - accepted', ['id' => $id, 'uri-id' => $uriid, 'replyto' => $replyto]);
 929                         return true;
 930                 }
 931
 932                 $attributed_to = JsonLD::fetchElement($activity['as:object'], 'as:attributedTo', '@id');
 933                 $authorid = Contact::getIdForURL($attributed_to);
 934
 935                 $body = HTML::toBBCode(JsonLD::fetchElement($activity['as:object'], 'as:content', '@value'));
 936
 937                 $messageTags = [];
 938                 $tags = Receiver::processTags(JsonLD::fetchElementArray($activity['as:object'], 'as:tag') ?? []);
 939                 if (!empty($tags)) {
 940                         foreach ($tags as $tag) {
 941                                 if ($tag['type'] != 'Hashtag') {
 942                                         continue;
 943                                 }
 944                                 $messageTags[] = ltrim(mb_strtolower($tag['name']), '#');
 945                         }
 946                 }
 947
 948                 return Relay::isSolicitedPost($messageTags, $body, $authorid, $id, Protocol::ACTIVITYPUB);
 949         }
 950
 951         /**
 952          * perform a "follow" request
 953          *
 954          * @param array $activity
 955          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 956          * @throws \ImagickException
 957          */
 958         public static function followUser($activity)
 959         {
 960                 $uid = User::getIdForURL($activity['object_id']);
 961                 if (empty($uid)) {
 962                         return;
 963                 }
 964
 965                 $owner = User::getOwnerDataById($uid);
 966                 if (empty($owner)) {
 967                         return;
 968                 }
 969
 970                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 971                 if (!empty($cid)) {
 972                         self::switchContact($cid);
 973                         Contact::update(['hub-verify' => $activity['id'], 'protocol' => Protocol::ACTIVITYPUB], ['id' => $cid]);
 974                 }
 975
 976                 $item = ['author-id' => Contact::getIdForURL($activity['actor']),
 977                         'author-link' => $activity['actor']];
 978
 979                 // Ensure that the contact has got the right network type
 980                 self::switchContact($item['author-id']);
 981
 982                 $result = Contact::addRelationship($owner, [], $item, false, $activity['content'] ?? '');
 983                 if ($result === true) {
 984                         ActivityPub\Transmitter::sendContactAccept($item['author-link'], $activity['id'], $owner['uid']);
 985                 }
 986
 987                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 988                 if (empty($cid)) {
 989                         return;
 990                 }
 991
 992                 if (empty($contact)) {
 993                         Contact::update(['hub-verify' => $activity['id'], 'protocol' => Protocol::ACTIVITYPUB], ['id' => $cid]);
 994                 }
 995
 996                 Logger::notice('Follow user ' . $uid . ' from contact ' . $cid . ' with id ' . $activity['id']);
 997         }
 998
 999         /**
1000          * Update the given profile
1001          *
1002          * @param array $activity
1003          * @throws \Exception
1004          */
1005         public static function updatePerson($activity)
1006         {
1007                 if (empty($activity['object_id'])) {
1008                         return;
1009                 }
1010
1011                 Logger::info('Updating profile', ['object' => $activity['object_id']]);
1012                 Contact::updateFromProbeByURL($activity['object_id']);
1013         }
1014
1015         /**
1016          * Delete the given profile
1017          *
1018          * @param array $activity
1019          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1020          */
1021         public static function deletePerson($activity)
1022         {
1023                 if (empty($activity['object_id']) || empty($activity['actor'])) {
1024                         Logger::info('Empty object id or actor.');
1025                         return;
1026                 }
1027
1028                 if ($activity['object_id'] != $activity['actor']) {
1029                         Logger::info('Object id does not match actor.');
1030                         return;
1031                 }
1032
1033                 $contacts = DBA::select('contact', ['id'], ['nurl' => Strings::normaliseLink($activity['object_id'])]);
1034                 while ($contact = DBA::fetch($contacts)) {
1035                         Contact::remove($contact['id']);
1036                 }
1037                 DBA::close($contacts);
1038
1039                 Logger::info('Deleted contact', ['object' => $activity['object_id']]);
1040         }
1041
1042         /**
1043          * Accept a follow request
1044          *
1045          * @param array $activity
1046          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1047          * @throws \ImagickException
1048          */
1049         public static function acceptFollowUser($activity)
1050         {
1051                 $uid = User::getIdForURL($activity['object_actor']);
1052                 if (empty($uid)) {
1053                         return;
1054                 }
1055
1056                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1057                 if (empty($cid)) {
1058                         Logger::info('No contact found', ['actor' => $activity['actor']]);
1059                         return;
1060                 }
1061
1062                 self::switchContact($cid);
1063
1064                 $fields = ['pending' => false];
1065
1066                 $contact = DBA::selectFirst('contact', ['rel'], ['id' => $cid]);
1067                 if ($contact['rel'] == Contact::FOLLOWER) {
1068                         $fields['rel'] = Contact::FRIEND;
1069                 }
1070
1071                 $condition = ['id' => $cid];
1072                 Contact::update($fields, $condition);
1073                 Logger::info('Accept contact request', ['contact' => $cid, 'user' => $uid]);
1074         }
1075
1076         /**
1077          * Reject a follow request
1078          *
1079          * @param array $activity
1080          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1081          * @throws \ImagickException
1082          */
1083         public static function rejectFollowUser($activity)
1084         {
1085                 $uid = User::getIdForURL($activity['object_actor']);
1086                 if (empty($uid)) {
1087                         return;
1088                 }
1089
1090                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1091                 if (empty($cid)) {
1092                         Logger::info('No contact found', ['actor' => $activity['actor']]);
1093                         return;
1094                 }
1095
1096                 self::switchContact($cid);
1097
1098                 $contact = Contact::getById($cid, ['rel']);
1099                 if ($contact['rel'] == Contact::SHARING) {
1100                         Contact::remove($cid);
1101                         Logger::info('Rejected contact request - contact removed', ['contact' => $cid, 'user' => $uid]);
1102                 } elseif ($contact['rel'] == Contact::FRIEND) {
1103                         Contact::update(['rel' => Contact::FOLLOWER], ['id' => $cid]);
1104                 } else {
1105                         Logger::info('Rejected contact request', ['contact' => $cid, 'user' => $uid]);
1106                 }
1107         }
1108
1109         /**
1110          * Undo activity like "like" or "dislike"
1111          *
1112          * @param array $activity
1113          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1114          * @throws \ImagickException
1115          */
1116         public static function undoActivity($activity)
1117         {
1118                 if (empty($activity['object_id'])) {
1119                         return;
1120                 }
1121
1122                 if (empty($activity['object_actor'])) {
1123                         return;
1124                 }
1125
1126                 $author_id = Contact::getIdForURL($activity['object_actor']);
1127                 if (empty($author_id)) {
1128                         return;
1129                 }
1130
1131                 Item::markForDeletion(['uri' => $activity['object_id'], 'author-id' => $author_id, 'gravity' => GRAVITY_ACTIVITY]);
1132         }
1133
1134         /**
1135          * Activity to remove a follower
1136          *
1137          * @param array $activity
1138          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1139          * @throws \ImagickException
1140          */
1141         public static function undoFollowUser($activity)
1142         {
1143                 $uid = User::getIdForURL($activity['object_object']);
1144                 if (empty($uid)) {
1145                         return;
1146                 }
1147
1148                 $owner = User::getOwnerDataById($uid);
1149                 if (empty($owner)) {
1150                         return;
1151                 }
1152
1153                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1154                 if (empty($cid)) {
1155                         Logger::info('No contact found', ['actor' => $activity['actor']]);
1156                         return;
1157                 }
1158
1159                 self::switchContact($cid);
1160
1161                 $contact = DBA::selectFirst('contact', [], ['id' => $cid]);
1162                 if (!DBA::isResult($contact)) {
1163                         return;
1164                 }
1165
1166                 Contact::removeFollower($contact);
1167                 Logger::info('Undo following request', ['contact' => $cid, 'user' => $uid]);
1168         }
1169
1170         /**
1171          * Switches a contact to AP if needed
1172          *
1173          * @param integer $cid Contact ID
1174          * @throws \Exception
1175          */
1176         private static function switchContact($cid)
1177         {
1178                 $contact = DBA::selectFirst('contact', ['network', 'url'], ['id' => $cid]);
1179                 if (!DBA::isResult($contact) || in_array($contact['network'], [Protocol::ACTIVITYPUB, Protocol::DFRN]) || Contact::isLocal($contact['url'])) {
1180                         return;
1181                 }
1182
1183                 Logger::info('Change existing contact', ['cid' => $cid, 'previous' => $contact['network']]);
1184                 Contact::updateFromProbe($cid);
1185         }
1186
1187         /**
1188          * Collects implicit mentions like:
1189          * - the author of the parent item
1190          * - all the mentioned conversants in the parent item
1191          *
1192          * @param array $parent Item array with at least ['id', 'author-link', 'alias']
1193          * @return array
1194          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1195          */
1196         private static function getImplicitMentionList(array $parent)
1197         {
1198                 $parent_terms = Tag::getByURIId($parent['uri-id'], [Tag::MENTION, Tag::IMPLICIT_MENTION, Tag::EXCLUSIVE_MENTION]);
1199
1200                 $parent_author = Contact::getByURL($parent['author-link'], false, ['url', 'nurl', 'alias']);
1201
1202                 $implicit_mentions = [];
1203                 if (empty($parent_author['url'])) {
1204                         Logger::notice('Author public contact unknown.', ['author-link' => $parent['author-link'], 'parent-id' => $parent['id']]);
1205                 } else {
1206                         $implicit_mentions[] = $parent_author['url'];
1207                         $implicit_mentions[] = $parent_author['nurl'];
1208                         $implicit_mentions[] = $parent_author['alias'];
1209                 }
1210
1211                 if (!empty($parent['alias'])) {
1212                         $implicit_mentions[] = $parent['alias'];
1213                 }
1214
1215                 foreach ($parent_terms as $term) {
1216                         $contact = Contact::getByURL($term['url'], false, ['url', 'nurl', 'alias']);
1217                         if (!empty($contact['url'])) {
1218                                 $implicit_mentions[] = $contact['url'];
1219                                 $implicit_mentions[] = $contact['nurl'];
1220                                 $implicit_mentions[] = $contact['alias'];
1221                         }
1222                 }
1223
1224                 return $implicit_mentions;
1225         }
1226
1227         /**
1228          * Strips from the body prepended implicit mentions
1229          *
1230          * @param string $body
1231          * @param array $parent
1232          * @return string
1233          */
1234         private static function removeImplicitMentionsFromBody(string $body, array $parent)
1235         {
1236                 if (DI::config()->get('system', 'disable_implicit_mentions')) {
1237                         return $body;
1238                 }
1239
1240                 $potential_mentions = self::getImplicitMentionList($parent);
1241
1242                 $kept_mentions = [];
1243
1244                 // Extract one prepended mention at a time from the body
1245                 while(preg_match('#^(@\[url=([^\]]+)].*?\[\/url]\s)(.*)#is', $body, $matches)) {
1246                         if (!in_array($matches[2], $potential_mentions)) {
1247                                 $kept_mentions[] = $matches[1];
1248                         }
1249
1250                         $body = $matches[3];
1251                 }
1252
1253                 // Re-appending the kept mentions to the body after extraction
1254                 $kept_mentions[] = $body;
1255
1256                 return implode('', $kept_mentions);
1257         }
1258
1259         /**
1260          * Adds links to string mentions
1261          *
1262          * @param string $body
1263          * @param array  $tags
1264          * @return string
1265          */
1266         protected static function addMentionLinks(string $body, array $tags): string
1267         {
1268                 // This prevents links to be added again to Pleroma-style mention links
1269                 $body = self::normalizeMentionLinks($body);
1270
1271                 $body = BBCode::performWithEscapedTags($body, ['url'], function ($body) use ($tags) {
1272                         foreach ($tags as $tag) {
1273                                 if (empty($tag['name']) || empty($tag['type']) || empty($tag['href']) || !in_array($tag['type'], ['Mention', 'Hashtag'])) {
1274                                         continue;
1275                                 }
1276
1277                                 $hash = substr($tag['name'], 0, 1);
1278                                 $name = substr($tag['name'], 1);
1279                                 if (!in_array($hash, Tag::TAG_CHARACTER)) {
1280                                         $hash = '';
1281                                         $name = $tag['name'];
1282                                 }
1283
1284                                 $body = str_replace($tag['name'], $hash . '[url=' . $tag['href'] . ']' . $name . '[/url]', $body);
1285                         }
1286
1287                         return $body;
1288                 });
1289
1290                 return $body;
1291         }
1292 }