src/Protocol/ActivityPub/Processor.php

   1 <?php
   2 /**
   3  * @file src/Protocol/ActivityPub/Processor.php
   4  */
   5 namespace Friendica\Protocol\ActivityPub;
   6
   7 use Friendica\Database\DBA;
   8 use Friendica\Content\Text\HTML;
   9 use Friendica\Core\Config;
  10 use Friendica\Core\Logger;
  11 use Friendica\Core\Protocol;
  12 use Friendica\Model\Contact;
  13 use Friendica\Model\APContact;
  14 use Friendica\Model\Item;
  15 use Friendica\Model\Event;
  16 use Friendica\Model\Term;
  17 use Friendica\Model\User;
  18 use Friendica\Protocol\ActivityPub;
  19 use Friendica\Util\DateTimeFormat;
  20 use Friendica\Util\JsonLD;
  21 use Friendica\Util\Strings;
  22
  23 /**
  24  * ActivityPub Processor Protocol class
  25  */
  26 class Processor
  27 {
  28         /**
  29          * Converts mentions from Pleroma into the Friendica format
  30          *
  31          * @param string $body
  32          *
  33          * @return string converted body
  34          */
  35         private static function convertMentions($body)
  36         {
  37                 $URLSearchString = "^\[\]";
  38                 $body = preg_replace("/\[url\=([$URLSearchString]*)\]([#@!])(.*?)\[\/url\]/ism", '$2[url=$1]$3[/url]', $body);
  39
  40                 return $body;
  41         }
  42
  43         /**
  44          * Replaces emojis in the body
  45          *
  46          * @param array $emojis
  47          * @param string $body
  48          *
  49          * @return string with replaced emojis
  50          */
  51         public static function replaceEmojis($body, array $emojis)
  52         {
  53                 foreach ($emojis as $emoji) {
  54                         $replace = '[class=emoji mastodon][img=' . $emoji['href'] . ']' . $emoji['name'] . '[/img][/class]';
  55                         $body = str_replace($emoji['name'], $replace, $body);
  56                 }
  57                 return $body;
  58         }
  59
  60         /**
  61          * Constructs a string with tags for a given tag array
  62          *
  63          * @param array   $tags
  64          * @param boolean $sensitive
  65          * @param array   $implicit_mentions List of profile URLs to skip
  66          * @return string with tags
  67          */
  68         private static function constructTagString($tags, $sensitive, array $implicit_mentions)
  69         {
  70                 if (empty($tags)) {
  71                         return '';
  72                 }
  73
  74                 $tag_text = '';
  75                 foreach ($tags as $tag) {
  76                         if (in_array(defaults($tag, 'type', ''), ['Mention', 'Hashtag']) && !in_array($tag['href'], $implicit_mentions)) {
  77                                 if (!empty($tag_text)) {
  78                                         $tag_text .= ',';
  79                                 }
  80
  81                                 $tag_text .= substr($tag['name'], 0, 1) . '[url=' . $tag['href'] . ']' . substr($tag['name'], 1) . '[/url]';
  82                         }
  83                 }
  84
  85                 /// @todo add nsfw for $sensitive
  86
  87                 return $tag_text;
  88         }
  89
  90         /**
  91          * Add attachment data to the item array
  92          *
  93          * @param array $attachments
  94          * @param array $item
  95          *
  96          * @return array array
  97          */
  98         private static function constructAttachList($attachments, $item)
  99         {
 100                 if (empty($attachments)) {
 101                         return $item;
 102                 }
 103
 104                 foreach ($attachments as $attach) {
 105                         $filetype = strtolower(substr($attach['mediaType'], 0, strpos($attach['mediaType'], '/')));
 106                         if ($filetype == 'image') {
 107                                 $item['body'] .= "\n[img]" . $attach['url'] . '[/img]';
 108                         } else {
 109                                 if (!empty($item["attach"])) {
 110                                         $item["attach"] .= ',';
 111                                 } else {
 112                                         $item["attach"] = '';
 113                                 }
 114                                 if (!isset($attach['length'])) {
 115                                         $attach['length'] = "0";
 116                                 }
 117                                 $item["attach"] .= '[attach]href="'.$attach['url'].'" length="'.$attach['length'].'" type="'.$attach['mediaType'].'" title="'.defaults($attach, 'name', '').'"[/attach]';
 118                         }
 119                 }
 120
 121                 return $item;
 122         }
 123
 124         /**
 125          * Updates a message
 126          *
 127          * @param array $activity Activity array
 128          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 129          */
 130         public static function updateItem($activity)
 131         {
 132                 $item = Item::selectFirst(['uri', 'parent-uri', 'gravity'], ['uri' => $activity['id']]);
 133                 if (!DBA::isResult($item)) {
 134                         Logger::warning('Unknown item', ['uri' => $activity['id']]);
 135                         return;
 136                 }
 137
 138                 $item['changed'] = DateTimeFormat::utcNow();
 139                 $item['edited'] = $activity['updated'];
 140                 $item['title'] = HTML::toBBCode($activity['name']);
 141                 $item['content-warning'] = HTML::toBBCode($activity['summary']);
 142
 143                 $content = HTML::toBBCode($activity['content']);
 144                 $content = self::replaceEmojis($content, $activity['emojis']);
 145                 $content = self::convertMentions($content);
 146
 147                 $implicit_mentions = [];
 148                 if (($item['parent-uri'] != $item['uri']) && ($item['gravity'] == GRAVITY_COMMENT)) {
 149                         $parent = Item::selectFirst(['id', 'author-link', 'alias'], ['uri' => $item['parent-uri']]);
 150                         if (!DBA::isResult($parent)) {
 151                                 Logger::warning('Unknown parent item.', ['uri' => $item['parent-uri']]);
 152                                 return;
 153                         }
 154
 155                         $implicit_mentions = self::getImplicitMentionList($parent);
 156                         $content = self::removeImplicitMentionsFromBody($content, $implicit_mentions);
 157                 }
 158
 159                 $item['body'] = $content;
 160                 $item['tag'] = self::constructTagString($activity['tags'], $activity['sensitive'], $implicit_mentions);
 161
 162                 Item::update($item, ['uri' => $activity['id']]);
 163         }
 164
 165         /**
 166          * Prepares data for a message
 167          *
 168          * @param array $activity Activity array
 169          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 170          * @throws \ImagickException
 171          */
 172         public static function createItem($activity)
 173         {
 174                 $item = [];
 175                 $item['verb'] = ACTIVITY_POST;
 176                 $item['parent-uri'] = $activity['reply-to-id'];
 177
 178                 if ($activity['reply-to-id'] == $activity['id']) {
 179                         $item['gravity'] = GRAVITY_PARENT;
 180                         $item['object-type'] = ACTIVITY_OBJ_NOTE;
 181                 } else {
 182                         $item['gravity'] = GRAVITY_COMMENT;
 183                         $item['object-type'] = ACTIVITY_OBJ_COMMENT;
 184                 }
 185
 186                 if (($activity['id'] != $activity['reply-to-id']) && !Item::exists(['uri' => $activity['reply-to-id']])) {
 187                         Logger::log('Parent ' . $activity['reply-to-id'] . ' not found. Try to refetch it.');
 188                         self::fetchMissingActivity($activity['reply-to-id'], $activity);
 189                 }
 190
 191                 $item['diaspora_signed_text'] = defaults($activity, 'diaspora:comment', '');
 192
 193                 self::postItem($activity, $item);
 194         }
 195
 196         /**
 197          * Delete items
 198          *
 199          * @param array $activity
 200          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 201          * @throws \ImagickException
 202          */
 203         public static function deleteItem($activity)
 204         {
 205                 $owner = Contact::getIdForURL($activity['actor']);
 206
 207                 Logger::log('Deleting item ' . $activity['object_id'] . ' from ' . $owner, Logger::DEBUG);
 208                 Item::delete(['uri' => $activity['object_id'], 'owner-id' => $owner]);
 209         }
 210
 211         /**
 212          * Prepare the item array for an activity
 213          *
 214          * @param array  $activity Activity array
 215          * @param string $verb     Activity verb
 216          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 217          * @throws \ImagickException
 218          */
 219         public static function createActivity($activity, $verb)
 220         {
 221                 $item = [];
 222                 $item['verb'] = $verb;
 223                 $item['parent-uri'] = $activity['object_id'];
 224                 $item['gravity'] = GRAVITY_ACTIVITY;
 225                 $item['object-type'] = ACTIVITY_OBJ_NOTE;
 226
 227                 $item['diaspora_signed_text'] = defaults($activity, 'diaspora:like', '');
 228
 229                 self::postItem($activity, $item);
 230         }
 231
 232         /**
 233          * Create an event
 234          *
 235          * @param array $activity Activity array
 236          * @param array $item
 237          * @throws \Exception
 238          */
 239         public static function createEvent($activity, $item)
 240         {
 241                 $event['summary']  = HTML::toBBCode($activity['name']);
 242                 $event['desc']     = HTML::toBBCode($activity['content']);
 243                 $event['start']    = $activity['start-time'];
 244                 $event['finish']   = $activity['end-time'];
 245                 $event['nofinish'] = empty($event['finish']);
 246                 $event['location'] = $activity['location'];
 247                 $event['adjust']   = true;
 248                 $event['cid']      = $item['contact-id'];
 249                 $event['uid']      = $item['uid'];
 250                 $event['uri']      = $item['uri'];
 251                 $event['edited']   = $item['edited'];
 252                 $event['private']  = $item['private'];
 253                 $event['guid']     = $item['guid'];
 254                 $event['plink']    = $item['plink'];
 255
 256                 $condition = ['uri' => $item['uri'], 'uid' => $item['uid']];
 257                 $ev = DBA::selectFirst('event', ['id'], $condition);
 258                 if (DBA::isResult($ev)) {
 259                         $event['id'] = $ev['id'];
 260                 }
 261
 262                 $event_id = Event::store($event);
 263                 Logger::log('Event '.$event_id.' was stored', Logger::DEBUG);
 264         }
 265
 266         /**
 267          * Creates an item post
 268          *
 269          * @param array $activity Activity data
 270          * @param array $item     item array
 271          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 272          * @throws \ImagickException
 273          */
 274         private static function postItem($activity, $item)
 275         {
 276                 /// @todo What to do with $activity['context']?
 277
 278                 if (($item['gravity'] != GRAVITY_PARENT) && !Item::exists(['uri' => $item['parent-uri']])) {
 279                         Logger::log('Parent ' . $item['parent-uri'] . ' not found, message will be discarded.', Logger::DEBUG);
 280                         return;
 281                 }
 282
 283                 $item['network'] = Protocol::ACTIVITYPUB;
 284                 $item['private'] = !in_array(0, $activity['receiver']);
 285                 $item['author-link'] = $activity['author'];
 286                 $item['author-id'] = Contact::getIdForURL($activity['author'], 0, true);
 287
 288                 if (empty($activity['thread-completion'])) {
 289                         $item['owner-link'] = $activity['actor'];
 290                         $item['owner-id'] = Contact::getIdForURL($activity['actor'], 0, true);
 291                 } else {
 292                         Logger::log('Ignoring actor because of thread completion.', Logger::DEBUG);
 293                         $item['owner-link'] = $item['author-link'];
 294                         $item['owner-id'] = $item['author-id'];
 295                 }
 296
 297                 $item['uri'] = $activity['id'];
 298                 $content = HTML::toBBCode($activity['content']);
 299                 $content = self::replaceEmojis($content, $activity['emojis']);
 300                 $content = self::convertMentions($content);
 301
 302                 $implicit_mentions = [];
 303
 304                 if (($item['parent-uri'] != $item['uri']) && ($item['gravity'] == GRAVITY_COMMENT)) {
 305                         $item_private = !in_array(0, $activity['item_receiver']);
 306                         $parent = Item::selectFirst(['id', 'private', 'author-link', 'alias'], ['uri' => $item['parent-uri']]);
 307                         if (!DBA::isResult($parent)) {
 308                                 return;
 309                         }
 310                         if ($item_private && !$parent['private']) {
 311                                 Logger::log('Item ' . $item['uri'] . ' is private but the parent ' . $item['parent-uri'] . ' is not. So we drop it.');
 312                                 return;
 313                         }
 314
 315                         $implicit_mentions = self::getImplicitMentionList($parent);
 316                         $content = self::removeImplicitMentionsFromBody($content, $implicit_mentions);
 317                 }
 318
 319                 $item['created'] = $activity['published'];
 320                 $item['edited'] = $activity['updated'];
 321                 $item['guid'] = $activity['diaspora:guid'];
 322                 $item['title'] = HTML::toBBCode($activity['name']);
 323                 $item['content-warning'] = HTML::toBBCode($activity['summary']);
 324                 $item['body'] = $content;
 325
 326                 if (($activity['object_type'] == 'as:Video') && !empty($activity['alternate-url'])) {
 327                         $item['body'] .= "\n[video]" . $activity['alternate-url'] . '[/video]';
 328                 }
 329
 330                 $item['location'] = $activity['location'];
 331
 332                 if (!empty($item['latitude']) && !empty($item['longitude'])) {
 333                         $item['coord'] = $item['latitude'] . ' ' . $item['longitude'];
 334                 }
 335
 336                 $item['tag'] = self::constructTagString($activity['tags'], $activity['sensitive'], $implicit_mentions);
 337                 $item['app'] = $activity['generator'];
 338                 $item['plink'] = defaults($activity, 'alternate-url', $item['uri']);
 339
 340                 $item = self::constructAttachList($activity['attachments'], $item);
 341
 342                 if (!empty($activity['source'])) {
 343                         $item['body'] = $activity['source'];
 344                 }
 345
 346                 foreach ($activity['receiver'] as $receiver) {
 347                         $item['uid'] = $receiver;
 348                         $item['contact-id'] = Contact::getIdForURL($activity['author'], $receiver, true);
 349
 350                         if (($receiver != 0) && empty($item['contact-id'])) {
 351                                 $item['contact-id'] = Contact::getIdForURL($activity['author'], 0, true);
 352                         }
 353
 354                         if ($activity['object_type'] == 'as:Event') {
 355                                 self::createEvent($activity, $item);
 356                         }
 357
 358                         $item_id = Item::insert($item);
 359                         Logger::log('Storing for user ' . $item['uid'] . ': ' . $item_id);
 360                 }
 361
 362                 if (!$item['private'] && ($item['gravity'] == GRAVITY_PARENT) && ($item['author-link'] != $item['owner-link'])) {
 363                         $author = APContact::getByURL($item['owner-link'], false);
 364                         // We send automatic follow requests for reshared messages. (We don't need though for forum posts)
 365                         if ($author['type'] != 'Group') {
 366                                 Logger::log('Send follow request for ' . $item['uri'] . ' to ' . $item['author-link'], Logger::DEBUG);
 367                                 ActivityPub\Transmitter::sendFollowObject($item['uri'], $item['author-link']);
 368                         }
 369                 }
 370         }
 371
 372         /**
 373          * Fetches missing posts
 374          *
 375          * @param $url
 376          * @param $child
 377          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 378          */
 379         private static function fetchMissingActivity($url, $child)
 380         {
 381                 if (Config::get('system', 'ostatus_full_threads')) {
 382                         return;
 383                 }
 384
 385                 $uid = ActivityPub\Receiver::getFirstUserFromReceivers($child['receiver']);
 386
 387                 $object = ActivityPub::fetchContent($url, $uid);
 388                 if (empty($object)) {
 389                         Logger::log('Activity ' . $url . ' was not fetchable, aborting.');
 390                         return;
 391                 }
 392
 393                 if (empty($object['id'])) {
 394                         Logger::log('Activity ' . $url . ' has got not id, aborting. ' . json_encode($object));
 395                         return;
 396                 }
 397
 398                 $activity = [];
 399                 $activity['@context'] = $object['@context'];
 400                 unset($object['@context']);
 401                 $activity['id'] = $object['id'];
 402                 $activity['to'] = defaults($object, 'to', []);
 403                 $activity['cc'] = defaults($object, 'cc', []);
 404                 $activity['actor'] = $child['author'];
 405                 $activity['object'] = $object;
 406                 $activity['published'] = defaults($object, 'published', $child['published']);
 407                 $activity['type'] = 'Create';
 408
 409                 $ldactivity = JsonLD::compact($activity);
 410
 411                 $ldactivity['thread-completion'] = true;
 412
 413                 ActivityPub\Receiver::processActivity($ldactivity);
 414                 Logger::log('Activity ' . $url . ' had been fetched and processed.');
 415         }
 416
 417         /**
 418          * perform a "follow" request
 419          *
 420          * @param array $activity
 421          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 422          * @throws \ImagickException
 423          */
 424         public static function followUser($activity)
 425         {
 426                 $uid = User::getIdForURL($activity['object_id']);
 427                 if (empty($uid)) {
 428                         return;
 429                 }
 430
 431                 $owner = User::getOwnerDataById($uid);
 432
 433                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 434                 if (!empty($cid)) {
 435                         self::switchContact($cid);
 436                         DBA::update('contact', ['hub-verify' => $activity['id']], ['id' => $cid]);
 437                         $contact = DBA::selectFirst('contact', [], ['id' => $cid, 'network' => Protocol::NATIVE_SUPPORT]);
 438                 } else {
 439                         $contact = false;
 440                 }
 441
 442                 $item = ['author-id' => Contact::getIdForURL($activity['actor']),
 443                         'author-link' => $activity['actor']];
 444
 445                 // Ensure that the contact has got the right network type
 446                 self::switchContact($item['author-id']);
 447
 448                 Contact::addRelationship($owner, $contact, $item);
 449                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 450                 if (empty($cid)) {
 451                         return;
 452                 }
 453
 454                 if (empty($contact)) {
 455                         DBA::update('contact', ['hub-verify' => $activity['id']], ['id' => $cid]);
 456                 }
 457
 458                 Logger::log('Follow user ' . $uid . ' from contact ' . $cid . ' with id ' . $activity['id']);
 459         }
 460
 461         /**
 462          * Update the given profile
 463          *
 464          * @param array $activity
 465          * @throws \Exception
 466          */
 467         public static function updatePerson($activity)
 468         {
 469                 if (empty($activity['object_id'])) {
 470                         return;
 471                 }
 472
 473                 Logger::log('Updating profile for ' . $activity['object_id'], Logger::DEBUG);
 474                 APContact::getByURL($activity['object_id'], true);
 475         }
 476
 477         /**
 478          * Delete the given profile
 479          *
 480          * @param array $activity
 481          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 482          */
 483         public static function deletePerson($activity)
 484         {
 485                 if (empty($activity['object_id']) || empty($activity['actor'])) {
 486                         Logger::log('Empty object id or actor.', Logger::DEBUG);
 487                         return;
 488                 }
 489
 490                 if ($activity['object_id'] != $activity['actor']) {
 491                         Logger::log('Object id does not match actor.', Logger::DEBUG);
 492                         return;
 493                 }
 494
 495                 $contacts = DBA::select('contact', ['id'], ['nurl' => Strings::normaliseLink($activity['object_id'])]);
 496                 while ($contact = DBA::fetch($contacts)) {
 497                         Contact::remove($contact['id']);
 498                 }
 499                 DBA::close($contacts);
 500
 501                 Logger::log('Deleted contact ' . $activity['object_id'], Logger::DEBUG);
 502         }
 503
 504         /**
 505          * Accept a follow request
 506          *
 507          * @param array $activity
 508          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 509          * @throws \ImagickException
 510          */
 511         public static function acceptFollowUser($activity)
 512         {
 513                 $uid = User::getIdForURL($activity['object_actor']);
 514                 if (empty($uid)) {
 515                         return;
 516                 }
 517
 518                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 519                 if (empty($cid)) {
 520                         Logger::log('No contact found for ' . $activity['actor'], Logger::DEBUG);
 521                         return;
 522                 }
 523
 524                 self::switchContact($cid);
 525
 526                 $fields = ['pending' => false];
 527
 528                 $contact = DBA::selectFirst('contact', ['rel'], ['id' => $cid]);
 529                 if ($contact['rel'] == Contact::FOLLOWER) {
 530                         $fields['rel'] = Contact::FRIEND;
 531                 }
 532
 533                 $condition = ['id' => $cid];
 534                 DBA::update('contact', $fields, $condition);
 535                 Logger::log('Accept contact request from contact ' . $cid . ' for user ' . $uid, Logger::DEBUG);
 536         }
 537
 538         /**
 539          * Reject a follow request
 540          *
 541          * @param array $activity
 542          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 543          * @throws \ImagickException
 544          */
 545         public static function rejectFollowUser($activity)
 546         {
 547                 $uid = User::getIdForURL($activity['object_actor']);
 548                 if (empty($uid)) {
 549                         return;
 550                 }
 551
 552                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 553                 if (empty($cid)) {
 554                         Logger::log('No contact found for ' . $activity['actor'], Logger::DEBUG);
 555                         return;
 556                 }
 557
 558                 self::switchContact($cid);
 559
 560                 if (DBA::exists('contact', ['id' => $cid, 'rel' => Contact::SHARING, 'pending' => true])) {
 561                         Contact::remove($cid);
 562                         Logger::log('Rejected contact request from contact ' . $cid . ' for user ' . $uid . ' - contact had been removed.', Logger::DEBUG);
 563                 } else {
 564                         Logger::log('Rejected contact request from contact ' . $cid . ' for user ' . $uid . '.', Logger::DEBUG);
 565                 }
 566         }
 567
 568         /**
 569          * Undo activity like "like" or "dislike"
 570          *
 571          * @param array $activity
 572          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 573          * @throws \ImagickException
 574          */
 575         public static function undoActivity($activity)
 576         {
 577                 if (empty($activity['object_id'])) {
 578                         return;
 579                 }
 580
 581                 if (empty($activity['object_actor'])) {
 582                         return;
 583                 }
 584
 585                 $author_id = Contact::getIdForURL($activity['object_actor']);
 586                 if (empty($author_id)) {
 587                         return;
 588                 }
 589
 590                 Item::delete(['uri' => $activity['object_id'], 'author-id' => $author_id, 'gravity' => GRAVITY_ACTIVITY]);
 591         }
 592
 593         /**
 594          * Activity to remove a follower
 595          *
 596          * @param array $activity
 597          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 598          * @throws \ImagickException
 599          */
 600         public static function undoFollowUser($activity)
 601         {
 602                 $uid = User::getIdForURL($activity['object_object']);
 603                 if (empty($uid)) {
 604                         return;
 605                 }
 606
 607                 $owner = User::getOwnerDataById($uid);
 608
 609                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 610                 if (empty($cid)) {
 611                         Logger::log('No contact found for ' . $activity['actor'], Logger::DEBUG);
 612                         return;
 613                 }
 614
 615                 self::switchContact($cid);
 616
 617                 $contact = DBA::selectFirst('contact', [], ['id' => $cid]);
 618                 if (!DBA::isResult($contact)) {
 619                         return;
 620                 }
 621
 622                 Contact::removeFollower($owner, $contact);
 623                 Logger::log('Undo following request from contact ' . $cid . ' for user ' . $uid, Logger::DEBUG);
 624         }
 625
 626         /**
 627          * Switches a contact to AP if needed
 628          *
 629          * @param integer $cid Contact ID
 630          * @throws \Exception
 631          */
 632         private static function switchContact($cid)
 633         {
 634                 $contact = DBA::selectFirst('contact', ['network'], ['id' => $cid, 'network' => Protocol::NATIVE_SUPPORT]);
 635                 if (!DBA::isResult($contact) || ($contact['network'] == Protocol::ACTIVITYPUB)) {
 636                         return;
 637                 }
 638
 639                 Logger::log('Change existing contact ' . $cid . ' from ' . $contact['network'] . ' to ActivityPub.');
 640                 Contact::updateFromProbe($cid, Protocol::ACTIVITYPUB);
 641         }
 642
 643         /**
 644          * Collects implicit mentions like:
 645          * - the author of the parent item
 646          * - all the mentioned conversants in the parent item
 647          *
 648          * @param array $parent Item array with at least ['id', 'author-link', 'alias']
 649          * @return array
 650          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 651          */
 652         private static function getImplicitMentionList(array $parent)
 653         {
 654                 $parent_terms = Term::tagArrayFromItemId($parent['id'], [TERM_MENTION]);
 655
 656                 $implicit_mentions = [
 657                         $parent['author-link']
 658                 ];
 659
 660                 if ($parent['alias']) {
 661                         $implicit_mentions[] = $parent['alias'];
 662                 }
 663
 664                 foreach ($parent_terms as $term) {
 665                         $contact = Contact::getDetailsByURL($term['url']);
 666
 667                         $implicit_mentions[] = $contact['url'];
 668                         $implicit_mentions[] = $contact['nurl'];
 669                         $implicit_mentions[] = $contact['alias'];
 670                 }
 671
 672                 return $implicit_mentions;
 673         }
 674
 675         /**
 676          * Strips from the body prepended implicit mentions
 677          *
 678          * @param string $body
 679          * @param array  $implicit_mentions List of profile URLs
 680          * @return string
 681          */
 682         private static function removeImplicitMentionsFromBody($body, array $implicit_mentions)
 683         {
 684                 $kept_mentions = [];
 685
 686                 // Extract one prepended mention at a time from the body
 687                 while(preg_match('#^(@\[url=([^\]]+)].*?\[\/url]\s)(.*)#mi', $body, $matches)) {
 688                         if (!in_array($matches[2], $implicit_mentions) ) {
 689                                 $kept_mentions[] = $matches[1];
 690                         }
 691
 692                         $body = $matches[3];
 693                 }
 694
 695                 // Re-appending the kept mentions to the body after extraction
 696                 $kept_mentions[] = $body;
 697
 698                 return implode('', $kept_mentions);
 699         }
 700 }