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\BBCode;
   9 use Friendica\Content\Text\HTML;
  10 use Friendica\Core\Config;
  11 use Friendica\Core\Logger;
  12 use Friendica\Core\Protocol;
  13 use Friendica\Model\Contact;
  14 use Friendica\Model\APContact;
  15 use Friendica\Model\Item;
  16 use Friendica\Model\Event;
  17 use Friendica\Model\Term;
  18 use Friendica\Model\User;
  19 use Friendica\Model\Mail;
  20 use Friendica\Protocol\ActivityPub;
  21 use Friendica\Util\DateTimeFormat;
  22 use Friendica\Util\JsonLD;
  23 use Friendica\Util\Strings;
  24
  25 /**
  26  * ActivityPub Processor Protocol class
  27  */
  28 class Processor
  29 {
  30         /**
  31          * Converts mentions from Pleroma into the Friendica format
  32          *
  33          * @param string $body
  34          *
  35          * @return string converted body
  36          */
  37         private static function convertMentions($body)
  38         {
  39                 $URLSearchString = "^\[\]";
  40                 $body = preg_replace("/\[url\=([$URLSearchString]*)\]([#@!])(.*?)\[\/url\]/ism", '$2[url=$1]$3[/url]', $body);
  41
  42                 return $body;
  43         }
  44
  45         /**
  46          * Replaces emojis in the body
  47          *
  48          * @param array $emojis
  49          * @param string $body
  50          *
  51          * @return string with replaced emojis
  52          */
  53         private static function replaceEmojis($body, array $emojis)
  54         {
  55                 foreach ($emojis as $emoji) {
  56                         $replace = '[class=emoji mastodon][img=' . $emoji['href'] . ']' . $emoji['name'] . '[/img][/class]';
  57                         $body = str_replace($emoji['name'], $replace, $body);
  58                 }
  59                 return $body;
  60         }
  61
  62         /**
  63          * Constructs a string with tags for a given tag array
  64          *
  65          * @param array   $tags
  66          * @param boolean $sensitive
  67          * @return string with tags
  68          */
  69         private static function constructTagString(array $tags = null, $sensitive = false)
  70         {
  71                 if (empty($tags)) {
  72                         return '';
  73                 }
  74
  75                 $tag_text = '';
  76                 foreach ($tags as $tag) {
  77                         if (in_array(defaults($tag, 'type', ''), ['Mention', 'Hashtag'])) {
  78                                 if (!empty($tag_text)) {
  79                                         $tag_text .= ',';
  80                                 }
  81
  82                                 $tag_text .= substr($tag['name'], 0, 1) . '[url=' . $tag['href'] . ']' . substr($tag['name'], 1) . '[/url]';
  83                         }
  84                 }
  85
  86                 /// @todo add nsfw for $sensitive
  87
  88                 return $tag_text;
  89         }
  90
  91         /**
  92          * Add attachment data to the item array
  93          *
  94          * @param array   $attachments
  95          * @param array   $item
  96          * @param boolean $no_images
  97          *
  98          * @return array array
  99          */
 100         private static function constructAttachList($attachments, $item, $no_images)
 101         {
 102                 if (empty($attachments)) {
 103                         return $item;
 104                 }
 105
 106                 foreach ($attachments as $attach) {
 107                         $filetype = strtolower(substr($attach['mediaType'], 0, strpos($attach['mediaType'], '/')));
 108                         if ($filetype == 'image') {
 109                                 if ($no_images) {
 110                                         continue;
 111                                 }
 112
 113                                 $item['body'] .= "\n[img]" . $attach['url'] . '[/img]';
 114                         } else {
 115                                 if (!empty($item["attach"])) {
 116                                         $item["attach"] .= ',';
 117                                 } else {
 118                                         $item["attach"] = '';
 119                                 }
 120                                 if (!isset($attach['length'])) {
 121                                         $attach['length'] = "0";
 122                                 }
 123                                 $item["attach"] .= '[attach]href="'.$attach['url'].'" length="'.$attach['length'].'" type="'.$attach['mediaType'].'" title="'.defaults($attach, 'name', '').'"[/attach]';
 124                         }
 125                 }
 126
 127                 return $item;
 128         }
 129
 130         /**
 131          * Updates a message
 132          *
 133          * @param array $activity Activity array
 134          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 135          */
 136         public static function updateItem($activity)
 137         {
 138                 $item = Item::selectFirst(['uri', 'thr-parent', 'gravity'], ['uri' => $activity['id']]);
 139                 if (!DBA::isResult($item)) {
 140                         Logger::warning('Unknown item', ['uri' => $activity['id']]);
 141                         return;
 142                 }
 143
 144                 $item['changed'] = DateTimeFormat::utcNow();
 145                 $item['edited'] = $activity['updated'];
 146
 147                 $item = self::processContent($activity, $item);
 148                 if (empty($item)) {
 149                         return;
 150                 }
 151
 152                 Item::update($item, ['uri' => $activity['id']]);
 153         }
 154
 155         /**
 156          * Prepares data for a message
 157          *
 158          * @param array $activity Activity array
 159          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 160          * @throws \ImagickException
 161          */
 162         public static function createItem($activity)
 163         {
 164                 $item = [];
 165                 $item['verb'] = ACTIVITY_POST;
 166                 $item['thr-parent'] = $activity['reply-to-id'];
 167
 168                 if ($activity['reply-to-id'] == $activity['id']) {
 169                         $item['gravity'] = GRAVITY_PARENT;
 170                         $item['object-type'] = ACTIVITY_OBJ_NOTE;
 171                 } else {
 172                         $item['gravity'] = GRAVITY_COMMENT;
 173                         $item['object-type'] = ACTIVITY_OBJ_COMMENT;
 174                 }
 175
 176                 if (empty($activity['directmessage']) && ($activity['id'] != $activity['reply-to-id']) && !Item::exists(['uri' => $activity['reply-to-id']])) {
 177                         Logger::log('Parent ' . $activity['reply-to-id'] . ' not found. Try to refetch it.');
 178                         self::fetchMissingActivity($activity['reply-to-id'], $activity);
 179                 }
 180
 181                 $item['diaspora_signed_text'] = defaults($activity, 'diaspora:comment', '');
 182
 183                 self::postItem($activity, $item);
 184         }
 185
 186         /**
 187          * Delete items
 188          *
 189          * @param array $activity
 190          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 191          * @throws \ImagickException
 192          */
 193         public static function deleteItem($activity)
 194         {
 195                 $owner = Contact::getIdForURL($activity['actor']);
 196
 197                 Logger::log('Deleting item ' . $activity['object_id'] . ' from ' . $owner, Logger::DEBUG);
 198                 Item::delete(['uri' => $activity['object_id'], 'owner-id' => $owner]);
 199         }
 200
 201         /**
 202          * Prepare the item array for an activity
 203          *
 204          * @param array  $activity Activity array
 205          * @param string $verb     Activity verb
 206          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 207          * @throws \ImagickException
 208          */
 209         public static function createActivity($activity, $verb)
 210         {
 211                 $item = [];
 212                 $item['verb'] = $verb;
 213                 $item['thr-parent'] = $activity['object_id'];
 214                 $item['gravity'] = GRAVITY_ACTIVITY;
 215                 $item['object-type'] = ACTIVITY_OBJ_NOTE;
 216
 217                 $item['diaspora_signed_text'] = defaults($activity, 'diaspora:like', '');
 218
 219                 self::postItem($activity, $item);
 220         }
 221
 222         /**
 223          * Create an event
 224          *
 225          * @param array $activity Activity array
 226          * @param array $item
 227          * @throws \Exception
 228          */
 229         public static function createEvent($activity, $item)
 230         {
 231                 $event['summary']  = HTML::toBBCode($activity['name']);
 232                 $event['desc']     = HTML::toBBCode($activity['content']);
 233                 $event['start']    = $activity['start-time'];
 234                 $event['finish']   = $activity['end-time'];
 235                 $event['nofinish'] = empty($event['finish']);
 236                 $event['location'] = $activity['location'];
 237                 $event['adjust']   = true;
 238                 $event['cid']      = $item['contact-id'];
 239                 $event['uid']      = $item['uid'];
 240                 $event['uri']      = $item['uri'];
 241                 $event['edited']   = $item['edited'];
 242                 $event['private']  = $item['private'];
 243                 $event['guid']     = $item['guid'];
 244                 $event['plink']    = $item['plink'];
 245
 246                 $condition = ['uri' => $item['uri'], 'uid' => $item['uid']];
 247                 $ev = DBA::selectFirst('event', ['id'], $condition);
 248                 if (DBA::isResult($ev)) {
 249                         $event['id'] = $ev['id'];
 250                 }
 251
 252                 $event_id = Event::store($event);
 253                 Logger::log('Event '.$event_id.' was stored', Logger::DEBUG);
 254         }
 255
 256         /**
 257          * Process the content
 258          *
 259          * @param array $activity Activity array
 260          * @param array $item
 261          * @return array|bool Returns the item array or false if there was an unexpected occurrence
 262          * @throws \Exception
 263          */
 264         private static function processContent($activity, $item)
 265         {
 266                 $item['title'] = HTML::toBBCode($activity['name']);
 267
 268                 if (!empty($activity['source'])) {
 269                         $item['body'] = $activity['source'];
 270                 } else {
 271                         $content = HTML::toBBCode($activity['content']);
 272
 273                         if (!empty($activity['emojis'])) {
 274                                 $content = self::replaceEmojis($content, $activity['emojis']);
 275                         }
 276
 277                         $content = self::convertMentions($content);
 278
 279                         if (empty($activity['directmessage']) && ($item['thr-parent'] != $item['uri']) && ($item['gravity'] == GRAVITY_COMMENT)) {
 280                                 $item_private = !in_array(0, $activity['item_receiver']);
 281                                 $parent = Item::selectFirst(['id', 'private', 'author-link', 'alias'], ['uri' => $item['thr-parent']]);
 282                                 if (!DBA::isResult($parent)) {
 283                                         Logger::warning('Unknown parent item.', ['uri' => $item['thr-parent']]);
 284                                         return false;
 285                                 }
 286                                 if ($item_private && !$parent['private']) {
 287                                         Logger::warning('Item is private but the parent is not. Dropping.', ['item-uri' => $item['uri'], 'thr-parent' => $item['thr-parent']]);
 288                                         return false;
 289                                 }
 290
 291                                 $potential_implicit_mentions = self::getImplicitMentionList($parent);
 292                                 $content = self::removeImplicitMentionsFromBody($content, $potential_implicit_mentions);
 293                                 $activity['tags'] = self::convertImplicitMentionsInTags($activity['tags'], $potential_implicit_mentions);
 294                         }
 295                         $item['content-warning'] = HTML::toBBCode($activity['summary']);
 296                         $item['body'] = $content;
 297
 298                         if (($activity['object_type'] == 'as:Video') && !empty($activity['alternate-url'])) {
 299                                 $item['body'] .= "\n[video]" . $activity['alternate-url'] . '[/video]';
 300                         }
 301                 }
 302
 303                 $item['tag'] = self::constructTagString($activity['tags'], $activity['sensitive']);
 304
 305                 $item['location'] = $activity['location'];
 306
 307                 if (!empty($item['latitude']) && !empty($item['longitude'])) {
 308                         $item['coord'] = $item['latitude'] . ' ' . $item['longitude'];
 309                 }
 310
 311                 $item['app'] = $activity['generator'];
 312
 313                 return $item;
 314         }
 315
 316         /**
 317          * Creates an item post
 318          *
 319          * @param array $activity Activity data
 320          * @param array $item     item array
 321          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 322          * @throws \ImagickException
 323          */
 324         private static function postItem($activity, $item)
 325         {
 326                 /// @todo What to do with $activity['context']?
 327                 if (empty($activity['directmessage']) && ($item['gravity'] != GRAVITY_PARENT) && !Item::exists(['uri' => $item['thr-parent']])) {
 328                         Logger::info('Parent not found, message will be discarded.', ['thr-parent' => $item['thr-parent']]);
 329                         return;
 330                 }
 331
 332                 $item['network'] = Protocol::ACTIVITYPUB;
 333                 $item['private'] = !in_array(0, $activity['receiver']);
 334                 $item['author-link'] = $activity['author'];
 335                 $item['author-id'] = Contact::getIdForURL($activity['author'], 0, true);
 336
 337                 if (empty($activity['thread-completion'])) {
 338                         $item['owner-link'] = $activity['actor'];
 339                         $item['owner-id'] = Contact::getIdForURL($activity['actor'], 0, true);
 340                 } else {
 341                         Logger::info('Ignoring actor because of thread completion.');
 342                         $item['owner-link'] = $item['author-link'];
 343                         $item['owner-id'] = $item['author-id'];
 344                 }
 345
 346                 $item['uri'] = $activity['id'];
 347
 348                 $item['created'] = $activity['published'];
 349                 $item['edited'] = $activity['updated'];
 350                 $item['guid'] = $activity['diaspora:guid'];
 351
 352                 $item = self::processContent($activity, $item);
 353                 if (empty($item)) {
 354                         return;
 355                 }
 356
 357                 $item['plink'] = defaults($activity, 'alternate-url', $item['uri']);
 358
 359                 $item = self::constructAttachList($activity['attachments'], $item, !empty($activity['source']));
 360
 361                 $stored = false;
 362
 363                 foreach ($activity['receiver'] as $receiver) {
 364                         $item['uid'] = $receiver;
 365                         $item['contact-id'] = Contact::getIdForURL($activity['author'], $receiver, true);
 366
 367                         if (($receiver != 0) && empty($item['contact-id'])) {
 368                                 $item['contact-id'] = Contact::getIdForURL($activity['author'], 0, true);
 369                         }
 370
 371                         if (!empty($activity['directmessage'])) {
 372                                 self::postMail($activity, $item);
 373                                 continue;
 374                         }
 375
 376                         if ($activity['object_type'] == 'as:Event') {
 377                                 self::createEvent($activity, $item);
 378                         }
 379
 380                         $item_id = Item::insert($item);
 381                         if ($item_id) {
 382                                 Logger::info('Item insertion successful', ['user' => $item['uid'], 'item_id' => $item_id]);
 383                         } else {
 384                                 Logger::notice('Item insertion aborted', ['user' => $item['uid']]);
 385                         }
 386
 387                         if ($item['uid'] == 0) {
 388                                 $stored = $item_id;
 389                         }
 390                 }
 391
 392                 // Store send a follow request for every reshare - but only when the item had been stored
 393                 if ($stored && !$item['private'] && ($item['gravity'] == GRAVITY_PARENT) && ($item['author-link'] != $item['owner-link'])) {
 394                         $author = APContact::getByURL($item['owner-link'], false);
 395                         // We send automatic follow requests for reshared messages. (We don't need though for forum posts)
 396                         if ($author['type'] != 'Group') {
 397                                 Logger::log('Send follow request for ' . $item['uri'] . ' (' . $stored . ') to ' . $item['author-link'], Logger::DEBUG);
 398                                 ActivityPub\Transmitter::sendFollowObject($item['uri'], $item['author-link']);
 399                         }
 400                 }
 401         }
 402
 403         /**
 404          * Creates an mail post
 405          *
 406          * @param array $activity Activity data
 407          * @param array $item     item array
 408          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 409          * @throws \ImagickException
 410          */
 411         private static function postMail($activity, $item)
 412         {
 413                 if (($item['gravity'] != GRAVITY_PARENT) && !DBA::exists('mail', ['uri' => $item['thr-parent'], 'uid' => $item['uid']])) {
 414                         Logger::info('Parent not found, mail will be discarded.', ['uid' => $item['uid'], 'uri' => $item['thr-parent']]);
 415                         return false;
 416                 }
 417
 418                 Logger::info('Direct Message', $item);
 419
 420                 $msg = [];
 421                 $msg['uid'] = $item['uid'];
 422
 423                 $msg['contact-id'] = $item['contact-id'];
 424
 425                 $contact = Contact::getById($item['contact-id'], ['name', 'url', 'photo']);
 426                 $msg['from-name'] = $contact['name'];
 427                 $msg['from-url'] = $contact['url'];
 428                 $msg['from-photo'] = $contact['photo'];
 429
 430                 $msg['uri'] = $item['uri'];
 431                 $msg['created'] = $item['created'];
 432
 433                 $parent = DBA::selectFirst('mail', ['parent-uri', 'title'], ['uri' => $item['thr-parent']]);
 434                 if (DBA::isResult($parent)) {
 435                         $msg['parent-uri'] = $parent['parent-uri'];
 436                         $msg['title'] = $parent['title'];
 437                 } else {
 438                         $msg['parent-uri'] = $item['thr-parent'];
 439
 440                         if (!empty($item['title'])) {
 441                                 $msg['title'] = $item['title'];
 442                         } elseif (!empty($item['content-warning'])) {
 443                                 $msg['title'] = $item['content-warning'];
 444                         } else {
 445                                 // Trying to generate a title out of the body
 446                                 $title = $item['body'];
 447
 448                                 while (preg_match('#^(@\[url=([^\]]+)].*?\[\/url]\s)(.*)#is', $title, $matches)) {
 449                                         $title = $matches[3];
 450                                 }
 451
 452                                 $title = trim(HTML::toPlaintext(BBCode::convert($title, false, 2, true), 0));
 453
 454                                 if (strlen($title) > 20) {
 455                                         $title = substr($title, 0, 20) . '...';
 456                                 }
 457
 458                                 $msg['title'] = $title;
 459                         }
 460                 }
 461                 $msg['body'] = $item['body'];
 462
 463                 Mail::insert($msg);
 464         }
 465
 466         /**
 467          * Fetches missing posts
 468          *
 469          * @param $url
 470          * @param $child
 471          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 472          */
 473         private static function fetchMissingActivity($url, $child)
 474         {
 475                 if (Config::get('system', 'ostatus_full_threads')) {
 476                         return;
 477                 }
 478
 479                 $uid = ActivityPub\Receiver::getFirstUserFromReceivers($child['receiver']);
 480
 481                 $object = ActivityPub::fetchContent($url, $uid);
 482                 if (empty($object)) {
 483                         Logger::log('Activity ' . $url . ' was not fetchable, aborting.');
 484                         return;
 485                 }
 486
 487                 if (empty($object['id'])) {
 488                         Logger::log('Activity ' . $url . ' has got not id, aborting. ' . json_encode($object));
 489                         return;
 490                 }
 491
 492                 $activity = [];
 493                 $activity['@context'] = $object['@context'];
 494                 unset($object['@context']);
 495                 $activity['id'] = $object['id'];
 496                 $activity['to'] = defaults($object, 'to', []);
 497                 $activity['cc'] = defaults($object, 'cc', []);
 498                 $activity['actor'] = $child['author'];
 499                 $activity['object'] = $object;
 500                 $activity['published'] = defaults($object, 'published', $child['published']);
 501                 $activity['type'] = 'Create';
 502
 503                 $ldactivity = JsonLD::compact($activity);
 504
 505                 $ldactivity['thread-completion'] = true;
 506
 507                 ActivityPub\Receiver::processActivity($ldactivity);
 508                 Logger::log('Activity ' . $url . ' had been fetched and processed.');
 509         }
 510
 511         /**
 512          * perform a "follow" request
 513          *
 514          * @param array $activity
 515          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 516          * @throws \ImagickException
 517          */
 518         public static function followUser($activity)
 519         {
 520                 $uid = User::getIdForURL($activity['object_id']);
 521                 if (empty($uid)) {
 522                         return;
 523                 }
 524
 525                 $owner = User::getOwnerDataById($uid);
 526
 527                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 528                 if (!empty($cid)) {
 529                         self::switchContact($cid);
 530                         DBA::update('contact', ['hub-verify' => $activity['id'], 'protocol' => Protocol::ACTIVITYPUB], ['id' => $cid]);
 531                         $contact = DBA::selectFirst('contact', [], ['id' => $cid, 'network' => Protocol::NATIVE_SUPPORT]);
 532                 } else {
 533                         $contact = false;
 534                 }
 535
 536                 $item = ['author-id' => Contact::getIdForURL($activity['actor']),
 537                         'author-link' => $activity['actor']];
 538
 539                 $note = Strings::escapeTags(trim(defaults($activity, 'content', '')));
 540
 541                 // Ensure that the contact has got the right network type
 542                 self::switchContact($item['author-id']);
 543
 544                 Contact::addRelationship($owner, $contact, $item, '', false, $note);
 545                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 546                 if (empty($cid)) {
 547                         return;
 548                 }
 549
 550                 if (empty($contact)) {
 551                         DBA::update('contact', ['hub-verify' => $activity['id'], 'protocol' => Protocol::ACTIVITYPUB], ['id' => $cid]);
 552                 }
 553
 554                 Logger::log('Follow user ' . $uid . ' from contact ' . $cid . ' with id ' . $activity['id']);
 555         }
 556
 557         /**
 558          * Update the given profile
 559          *
 560          * @param array $activity
 561          * @throws \Exception
 562          */
 563         public static function updatePerson($activity)
 564         {
 565                 if (empty($activity['object_id'])) {
 566                         return;
 567                 }
 568
 569                 Logger::log('Updating profile for ' . $activity['object_id'], Logger::DEBUG);
 570                 APContact::getByURL($activity['object_id'], true);
 571         }
 572
 573         /**
 574          * Delete the given profile
 575          *
 576          * @param array $activity
 577          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 578          */
 579         public static function deletePerson($activity)
 580         {
 581                 if (empty($activity['object_id']) || empty($activity['actor'])) {
 582                         Logger::log('Empty object id or actor.', Logger::DEBUG);
 583                         return;
 584                 }
 585
 586                 if ($activity['object_id'] != $activity['actor']) {
 587                         Logger::log('Object id does not match actor.', Logger::DEBUG);
 588                         return;
 589                 }
 590
 591                 $contacts = DBA::select('contact', ['id'], ['nurl' => Strings::normaliseLink($activity['object_id'])]);
 592                 while ($contact = DBA::fetch($contacts)) {
 593                         Contact::remove($contact['id']);
 594                 }
 595                 DBA::close($contacts);
 596
 597                 Logger::log('Deleted contact ' . $activity['object_id'], Logger::DEBUG);
 598         }
 599
 600         /**
 601          * Accept a follow request
 602          *
 603          * @param array $activity
 604          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 605          * @throws \ImagickException
 606          */
 607         public static function acceptFollowUser($activity)
 608         {
 609                 $uid = User::getIdForURL($activity['object_actor']);
 610                 if (empty($uid)) {
 611                         return;
 612                 }
 613
 614                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 615                 if (empty($cid)) {
 616                         Logger::log('No contact found for ' . $activity['actor'], Logger::DEBUG);
 617                         return;
 618                 }
 619
 620                 self::switchContact($cid);
 621
 622                 $fields = ['pending' => false];
 623
 624                 $contact = DBA::selectFirst('contact', ['rel'], ['id' => $cid]);
 625                 if ($contact['rel'] == Contact::FOLLOWER) {
 626                         $fields['rel'] = Contact::FRIEND;
 627                 }
 628
 629                 $condition = ['id' => $cid];
 630                 DBA::update('contact', $fields, $condition);
 631                 Logger::log('Accept contact request from contact ' . $cid . ' for user ' . $uid, Logger::DEBUG);
 632         }
 633
 634         /**
 635          * Reject a follow request
 636          *
 637          * @param array $activity
 638          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 639          * @throws \ImagickException
 640          */
 641         public static function rejectFollowUser($activity)
 642         {
 643                 $uid = User::getIdForURL($activity['object_actor']);
 644                 if (empty($uid)) {
 645                         return;
 646                 }
 647
 648                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 649                 if (empty($cid)) {
 650                         Logger::log('No contact found for ' . $activity['actor'], Logger::DEBUG);
 651                         return;
 652                 }
 653
 654                 self::switchContact($cid);
 655
 656                 if (DBA::exists('contact', ['id' => $cid, 'rel' => Contact::SHARING])) {
 657                         Contact::remove($cid);
 658                         Logger::log('Rejected contact request from contact ' . $cid . ' for user ' . $uid . ' - contact had been removed.', Logger::DEBUG);
 659                 } else {
 660                         Logger::log('Rejected contact request from contact ' . $cid . ' for user ' . $uid . '.', Logger::DEBUG);
 661                 }
 662         }
 663
 664         /**
 665          * Undo activity like "like" or "dislike"
 666          *
 667          * @param array $activity
 668          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 669          * @throws \ImagickException
 670          */
 671         public static function undoActivity($activity)
 672         {
 673                 if (empty($activity['object_id'])) {
 674                         return;
 675                 }
 676
 677                 if (empty($activity['object_actor'])) {
 678                         return;
 679                 }
 680
 681                 $author_id = Contact::getIdForURL($activity['object_actor']);
 682                 if (empty($author_id)) {
 683                         return;
 684                 }
 685
 686                 Item::delete(['uri' => $activity['object_id'], 'author-id' => $author_id, 'gravity' => GRAVITY_ACTIVITY]);
 687         }
 688
 689         /**
 690          * Activity to remove a follower
 691          *
 692          * @param array $activity
 693          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 694          * @throws \ImagickException
 695          */
 696         public static function undoFollowUser($activity)
 697         {
 698                 $uid = User::getIdForURL($activity['object_object']);
 699                 if (empty($uid)) {
 700                         return;
 701                 }
 702
 703                 $owner = User::getOwnerDataById($uid);
 704
 705                 $cid = Contact::getIdForURL($activity['actor'], $uid);
 706                 if (empty($cid)) {
 707                         Logger::log('No contact found for ' . $activity['actor'], Logger::DEBUG);
 708                         return;
 709                 }
 710
 711                 self::switchContact($cid);
 712
 713                 $contact = DBA::selectFirst('contact', [], ['id' => $cid]);
 714                 if (!DBA::isResult($contact)) {
 715                         return;
 716                 }
 717
 718                 Contact::removeFollower($owner, $contact);
 719                 Logger::log('Undo following request from contact ' . $cid . ' for user ' . $uid, Logger::DEBUG);
 720         }
 721
 722         /**
 723          * Switches a contact to AP if needed
 724          *
 725          * @param integer $cid Contact ID
 726          * @throws \Exception
 727          */
 728         private static function switchContact($cid)
 729         {
 730                 $contact = DBA::selectFirst('contact', ['network'], ['id' => $cid, 'network' => Protocol::NATIVE_SUPPORT]);
 731                 if (!DBA::isResult($contact) || in_array($contact['network'], [Protocol::ACTIVITYPUB, Protocol::DFRN])) {
 732                         return;
 733                 }
 734
 735                 Logger::log('Change existing contact ' . $cid . ' from ' . $contact['network'] . ' to ActivityPub.');
 736                 Contact::updateFromProbe($cid, Protocol::ACTIVITYPUB);
 737         }
 738
 739         /**
 740          * Collects implicit mentions like:
 741          * - the author of the parent item
 742          * - all the mentioned conversants in the parent item
 743          *
 744          * @param array $parent Item array with at least ['id', 'author-link', 'alias']
 745          * @return array
 746          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 747          */
 748         private static function getImplicitMentionList(array $parent)
 749         {
 750                 if (Config::get('system', 'disable_implicit_mentions')) {
 751                         return [];
 752                 }
 753
 754                 $parent_terms = Term::tagArrayFromItemId($parent['id'], [Term::MENTION, Term::IMPLICIT_MENTION]);
 755
 756                 $parent_author = Contact::getDetailsByURL($parent['author-link'], 0);
 757
 758                 $implicit_mentions = [];
 759                 if (empty($parent_author)) {
 760                         Logger::notice('Author public contact unknown.', ['author-link' => $parent['author-link'], 'item-id' => $parent['id']]);
 761                 } else {
 762                         $implicit_mentions[] = $parent_author['url'];
 763                         $implicit_mentions[] = $parent_author['nurl'];
 764                         $implicit_mentions[] = $parent_author['alias'];
 765                 }
 766
 767                 if (!empty($parent['alias'])) {
 768                         $implicit_mentions[] = $parent['alias'];
 769                 }
 770
 771                 foreach ($parent_terms as $term) {
 772                         $contact = Contact::getDetailsByURL($term['url'], 0);
 773                         if (!empty($contact)) {
 774                                 $implicit_mentions[] = $contact['url'];
 775                                 $implicit_mentions[] = $contact['nurl'];
 776                                 $implicit_mentions[] = $contact['alias'];
 777                         }
 778                 }
 779
 780                 return $implicit_mentions;
 781         }
 782
 783         /**
 784          * Strips from the body prepended implicit mentions
 785          *
 786          * @param string $body
 787          * @param array $potential_mentions
 788          * @return string
 789          */
 790         private static function removeImplicitMentionsFromBody($body, array $potential_mentions)
 791         {
 792                 if (Config::get('system', 'disable_implicit_mentions')) {
 793                         return $body;
 794                 }
 795
 796                 $kept_mentions = [];
 797
 798                 // Extract one prepended mention at a time from the body
 799                 while(preg_match('#^(@\[url=([^\]]+)].*?\[\/url]\s)(.*)#is', $body, $matches)) {
 800                         if (!in_array($matches[2], $potential_mentions) ) {
 801                                 $kept_mentions[] = $matches[1];
 802                         }
 803
 804                         $body = $matches[3];
 805                 }
 806
 807                 // Re-appending the kept mentions to the body after extraction
 808                 $kept_mentions[] = $body;
 809
 810                 return implode('', $kept_mentions);
 811         }
 812
 813         private static function convertImplicitMentionsInTags($activity_tags, array $potential_mentions)
 814         {
 815                 if (Config::get('system', 'disable_implicit_mentions')) {
 816                         return $activity_tags;
 817                 }
 818
 819                 foreach ($activity_tags as $index => $tag) {
 820                         if (in_array($tag['href'], $potential_mentions)) {
 821                                 $activity_tags[$index]['name'] = preg_replace(
 822                                         '/' . preg_quote(Term::TAG_CHARACTER[Term::MENTION], '/') . '/',
 823                                         Term::TAG_CHARACTER[Term::IMPLICIT_MENTION],
 824                                         $activity_tags[$index]['name'],
 825                                         1
 826                                 );
 827                         }
 828                 }
 829
 830                 return $activity_tags;
 831         }
 832 }