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, '', Receiver::COMPLETION_AUTO);
 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'], $activity['tags']);
 528
 529                 self::storeReceivers($item['uri-id'], $activity['receiver_urls'] ?? []);
 530
 531                 $item['location'] = $activity['location'];
 532
 533                 if (!empty($activity['latitude']) && !empty($activity['longitude'])) {
 534                         $item['coord'] = $activity['latitude'] . ' ' . $activity['longitude'];
 535                 }
 536
 537                 $item['app'] = $activity['generator'];
 538
 539                 return $item;
 540         }
 541
 542         /**
 543          * Store hashtags and mentions
 544          *
 545          * @param array $item
 546          */
 547         private static function storeFromBody(array $item)
 548         {
 549                 // Make sure to delete all existing tags (can happen when called via the update functionality)
 550                 DBA::delete('post-tag', ['uri-id' => $item['uri-id']]);
 551
 552                 Tag::storeFromBody($item['uri-id'], $item['body'], '@!');
 553         }
 554
 555         /**
 556          * Generate a GUID out of an URL
 557          *
 558          * @param string $url message URL
 559          * @return string with GUID
 560          */
 561         private static function getGUIDByURL(string $url)
 562         {
 563                 $parsed = parse_url($url);
 564
 565                 $host_hash = hash('crc32', $parsed['host']);
 566
 567                 unset($parsed["scheme"]);
 568                 unset($parsed["host"]);
 569
 570                 $path = implode("/", $parsed);
 571
 572                 return $host_hash . '-'. hash('fnv164', $path) . '-'. hash('joaat', $path);
 573         }
 574
 575         /**
 576          * Checks if an incoming message is wanted
 577          *
 578          * @param array $activity
 579          * @param array $item
 580          * @return boolean Is the message wanted?
 581          */
 582         private static function isSolicitedMessage(array $activity, array $item)
 583         {
 584                 // The checks are split to improve the support when searching why a message was accepted.
 585                 if (count($activity['receiver']) != 1) {
 586                         // The message has more than one receiver, so it is wanted.
 587                         Logger::debug('Message has got several receivers - accepted', ['uri-id' => $item['uri-id'], 'guid' => $item['guid'], 'url' => $item['uri']]);
 588                         return true;
 589                 }
 590
 591                 if ($item['private'] == Item::PRIVATE) {
 592                         // We only look at public posts here. Private posts are expected to be intentionally posted to the single receiver.
 593                         Logger::debug('Message is private - accepted', ['uri-id' => $item['uri-id'], 'guid' => $item['guid'], 'url' => $item['uri']]);
 594                         return true;
 595                 }
 596
 597                 if (!empty($activity['from-relay'])) {
 598                         // We check relay posts at another place. When it arrived here, the message is already checked.
 599                         Logger::debug('Message is a relay post that is already checked - accepted', ['uri-id' => $item['uri-id'], 'guid' => $item['guid'], 'url' => $item['uri']]);
 600                         return true;
 601                 }
 602
 603                 if (in_array($activity['completion-mode'] ?? Receiver::COMPLETION_NONE, [Receiver::COMPLETION_MANUAL, Receiver::COMPLETION_ANNOUCE])) {
 604                         // Manual completions and completions caused by reshares are allowed without any further checks.
 605                         Logger::debug('Message is in completion mode - accepted', ['mode' => $activity['completion-mode'], 'uri-id' => $item['uri-id'], 'guid' => $item['guid'], 'url' => $item['uri']]);
 606                         return true;
 607                 }
 608
 609                 if ($item['gravity'] != GRAVITY_PARENT) {
 610                         // We cannot reliably check at this point if a comment or activity belongs to an accepted post or needs to be fetched
 611                         // This can possibly be improved in the future.
 612                         Logger::debug('Message is no parent - accepted', ['uri-id' => $item['uri-id'], 'guid' => $item['guid'], 'url' => $item['uri']]);
 613                         return true;
 614                 }
 615
 616                 $tags = array_column(Tag::getByURIId($item['uri-id'], [Tag::HASHTAG]), 'name');
 617                 if (Relay::isSolicitedPost($tags, $item['body'], $item['author-id'], $item['uri'], Protocol::ACTIVITYPUB)) {
 618                         Logger::debug('Post is accepted because of the relay settings', ['uri-id' => $item['uri-id'], 'guid' => $item['guid'], 'url' => $item['uri']]);
 619                         return true;
 620                 } else {
 621                         return false;
 622                 }
 623         }
 624
 625         /**
 626          * Creates an item post
 627          *
 628          * @param array $activity Activity data
 629          * @param array $item     item array
 630          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 631          * @throws \ImagickException
 632          */
 633         public static function postItem(array $activity, array $item)
 634         {
 635                 if (empty($item)) {
 636                         return;
 637                 }
 638
 639                 $stored = false;
 640                 ksort($activity['receiver']);
 641
 642                 if (!self::isSolicitedMessage($activity, $item)) {
 643                         DBA::delete('item-uri', ['id' => $item['uri-id']]);
 644                         return;
 645                 }
 646
 647                 foreach ($activity['receiver'] as $receiver) {
 648                         if ($receiver == -1) {
 649                                 continue;
 650                         }
 651
 652                         $item['uid'] = $receiver;
 653
 654                         $type = $activity['reception_type'][$receiver] ?? Receiver::TARGET_UNKNOWN;
 655                         switch($type) {
 656                                 case Receiver::TARGET_TO:
 657                                         $item['post-reason'] = Item::PR_TO;
 658                                         break;
 659                                 case Receiver::TARGET_CC:
 660                                         $item['post-reason'] = Item::PR_CC;
 661                                         break;
 662                                 case Receiver::TARGET_BTO:
 663                                         $item['post-reason'] = Item::PR_BTO;
 664                                         break;
 665                                 case Receiver::TARGET_BCC:
 666                                         $item['post-reason'] = Item::PR_BCC;
 667                                         break;
 668                                 case Receiver::TARGET_FOLLOWER:
 669                                         $item['post-reason'] = Item::PR_FOLLOWER;
 670                                         break;
 671                                 case Receiver::TARGET_ANSWER:
 672                                         $item['post-reason'] = Item::PR_COMMENT;
 673                                         break;
 674                                 case Receiver::TARGET_GLOBAL:
 675                                         $item['post-reason'] = Item::PR_GLOBAL;
 676                                         break;
 677                                 default:
 678                                         $item['post-reason'] = Item::PR_NONE;
 679                         }
 680
 681                         if (!empty($activity['from-relay'])) {
 682                                 $item['post-reason'] = Item::PR_RELAY;
 683                         } elseif (!empty($activity['thread-completion'])) {
 684                                 $item['post-reason'] = Item::PR_FETCHED;
 685                         }
 686
 687                         if ($item['isForum'] ?? false) {
 688                                 $item['contact-id'] = Contact::getIdForURL($activity['actor'], $receiver);
 689                         } else {
 690                                 $item['contact-id'] = Contact::getIdForURL($activity['author'], $receiver);
 691                         }
 692
 693                         if (($receiver != 0) && empty($item['contact-id'])) {
 694                                 $item['contact-id'] = Contact::getIdForURL($activity['author']);
 695                         }
 696
 697                         if (!empty($activity['directmessage'])) {
 698                                 self::postMail($activity, $item);
 699                                 continue;
 700                         }
 701
 702                         if (!($item['isForum'] ?? false) && ($receiver != 0) && ($item['gravity'] == GRAVITY_PARENT) && !Contact::isSharingByURL($activity['author'], $receiver)) {
 703                                 if ($item['post-reason'] == Item::PR_BCC) {
 704                                         Logger::info('Top level post via BCC from a non sharer, ignoring', ['uid' => $receiver, 'contact' => $item['contact-id']]);
 705                                         continue;
 706                                 }
 707
 708                                 if (
 709                                         !empty($activity['thread-children-type'])
 710                                         && in_array($activity['thread-children-type'], Receiver::ACTIVITY_TYPES)
 711                                         && DI::pConfig()->get($receiver, 'system', 'accept_only_sharer') != Item::COMPLETION_LIKE
 712                                 ) {
 713                                         Logger::info('Top level post from thread completion from a non sharer had been initiated via an activity, ignoring',
 714                                                 ['type' => $activity['thread-children-type'], 'user' => $item['uid'], 'causer' => $item['causer-link'], 'author' => $activity['author'], 'url' => $item['uri']]);
 715                                         continue;
 716                                 }
 717                         }
 718
 719                         $is_forum = false;
 720
 721                         if ($receiver != 0) {
 722                                 $user = User::getById($receiver, ['account-type']);
 723                                 if (!empty($user['account-type'])) {
 724                                         $is_forum = ($user['account-type'] == User::ACCOUNT_TYPE_COMMUNITY);
 725                                 }
 726                         }
 727
 728                         if (!$is_forum && DI::pConfig()->get($receiver, 'system', 'accept_only_sharer') == Item::COMPLETION_NONE && ($receiver != 0) && ($item['gravity'] == GRAVITY_PARENT)) {
 729                                 $skip = !Contact::isSharingByURL($activity['author'], $receiver);
 730
 731                                 if ($skip && (($activity['type'] == 'as:Announce') || ($item['isForum'] ?? false))) {
 732                                         $skip = !Contact::isSharingByURL($activity['actor'], $receiver);
 733                                 }
 734
 735                                 if ($skip) {
 736                                         Logger::info('Skipping post', ['uid' => $receiver, 'url' => $item['uri']]);
 737                                         continue;
 738                                 }
 739
 740                                 Logger::info('Accepting post', ['uid' => $receiver, 'url' => $item['uri']]);
 741                         }
 742
 743                         if (($item['gravity'] != GRAVITY_ACTIVITY) && ($activity['object_type'] == 'as:Event')) {
 744                                 $event_id = self::createEvent($activity, $item);
 745
 746                                 $item = Event::getItemArrayForImportedId($event_id, $item);
 747                         }
 748
 749                         $item_id = Item::insert($item);
 750                         if ($item_id) {
 751                                 Logger::info('Item insertion successful', ['user' => $item['uid'], 'item_id' => $item_id]);
 752                         } else {
 753                                 Logger::notice('Item insertion aborted', ['user' => $item['uid']]);
 754                         }
 755
 756                         if ($item['uid'] == 0) {
 757                                 $stored = $item_id;
 758                         }
 759                 }
 760
 761                 // Store send a follow request for every reshare - but only when the item had been stored
 762                 if ($stored && ($item['private'] != Item::PRIVATE) && ($item['gravity'] == GRAVITY_PARENT) && ($item['author-link'] != $item['owner-link'])) {
 763                         $author = APContact::getByURL($item['owner-link'], false);
 764                         // We send automatic follow requests for reshared messages. (We don't need though for forum posts)
 765                         if ($author['type'] != 'Group') {
 766                                 Logger::info('Send follow request', ['uri' => $item['uri'], 'stored' => $stored, 'to' => $item['author-link']]);
 767                                 ActivityPub\Transmitter::sendFollowObject($item['uri'], $item['author-link']);
 768                         }
 769                 }
 770         }
 771
 772         /**
 773          * Store tags and mentions into the tag table
 774          *
 775          * @param integer $uriid
 776          * @param array $tags
 777          */
 778         private static function storeTags(int $uriid, array $tags = null)
 779         {
 780                 foreach ($tags as $tag) {
 781                         if (empty($tag['name']) || empty($tag['type']) || !in_array($tag['type'], ['Mention', 'Hashtag'])) {
 782                                 continue;
 783                         }
 784
 785                         $hash = substr($tag['name'], 0, 1);
 786
 787                         if ($tag['type'] == 'Mention') {
 788                                 if (in_array($hash, [Tag::TAG_CHARACTER[Tag::MENTION],
 789                                         Tag::TAG_CHARACTER[Tag::EXCLUSIVE_MENTION],
 790                                         Tag::TAG_CHARACTER[Tag::IMPLICIT_MENTION]])) {
 791                                         $tag['name'] = substr($tag['name'], 1);
 792                                 }
 793                                 $type = Tag::IMPLICIT_MENTION;
 794
 795                                 if (!empty($tag['href'])) {
 796                                         $apcontact = APContact::getByURL($tag['href']);
 797                                         if (!empty($apcontact['name']) || !empty($apcontact['nick'])) {
 798                                                 $tag['name'] = $apcontact['name'] ?: $apcontact['nick'];
 799                                         }
 800                                 }
 801                         } elseif ($tag['type'] == 'Hashtag') {
 802                                 if ($hash == Tag::TAG_CHARACTER[Tag::HASHTAG]) {
 803                                         $tag['name'] = substr($tag['name'], 1);
 804                                 }
 805                                 $type = Tag::HASHTAG;
 806                         }
 807
 808                         if (empty($tag['name'])) {
 809                                 continue;
 810                         }
 811
 812                         Tag::store($uriid, $type, $tag['name'], $tag['href']);
 813                 }
 814         }
 815
 816         public static function storeReceivers(int $uriid, array $receivers)
 817         {
 818                 foreach (['as:to' => Tag::TO, 'as:cc' => Tag::CC, 'as:bto' => Tag::BTO, 'as:bcc' => Tag::BCC] as $element => $type) {
 819                         if (!empty($receivers[$element])) {
 820                                 foreach ($receivers[$element] as $receiver) {
 821                                         if ($receiver == ActivityPub::PUBLIC_COLLECTION) {
 822                                                 $name = Receiver::PUBLIC_COLLECTION;
 823                                         } else {
 824                                                 $name = trim(parse_url($receiver, PHP_URL_PATH), '/');
 825                                         }
 826                                         Tag::store($uriid, $type, $name, $receiver);
 827                                 }
 828                         }
 829                 }
 830         }
 831
 832         /**
 833          * Creates an mail post
 834          *
 835          * @param array $activity Activity data
 836          * @param array $item     item array
 837          * @return int|bool New mail table row id or false on error
 838          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 839          */
 840         private static function postMail($activity, $item)
 841         {
 842                 if (($item['gravity'] != GRAVITY_PARENT) && !DBA::exists('mail', ['uri' => $item['thr-parent'], 'uid' => $item['uid']])) {
 843                         Logger::info('Parent not found, mail will be discarded.', ['uid' => $item['uid'], 'uri' => $item['thr-parent']]);
 844                         return false;
 845                 }
 846
 847                 Logger::info('Direct Message', $item);
 848
 849                 $msg = [];
 850                 $msg['uid'] = $item['uid'];
 851
 852                 $msg['contact-id'] = $item['contact-id'];
 853
 854                 $contact = Contact::getById($item['contact-id'], ['name', 'url', 'photo']);
 855                 $msg['from-name'] = $contact['name'];
 856                 $msg['from-url'] = $contact['url'];
 857                 $msg['from-photo'] = $contact['photo'];
 858
 859                 $msg['uri'] = $item['uri'];
 860                 $msg['created'] = $item['created'];
 861
 862                 $parent = DBA::selectFirst('mail', ['parent-uri', 'title'], ['uri' => $item['thr-parent']]);
 863                 if (DBA::isResult($parent)) {
 864                         $msg['parent-uri'] = $parent['parent-uri'];
 865                         $msg['title'] = $parent['title'];
 866                 } else {
 867                         $msg['parent-uri'] = $item['thr-parent'];
 868
 869                         if (!empty($item['title'])) {
 870                                 $msg['title'] = $item['title'];
 871                         } elseif (!empty($item['content-warning'])) {
 872                                 $msg['title'] = $item['content-warning'];
 873                         } else {
 874                                 // Trying to generate a title out of the body
 875                                 $title = $item['body'];
 876
 877                                 while (preg_match('#^(@\[url=([^\]]+)].*?\[\/url]\s)(.*)#is', $title, $matches)) {
 878                                         $title = $matches[3];
 879                                 }
 880
 881                                 $title = trim(BBCode::toPlaintext($title));
 882
 883                                 if (strlen($title) > 20) {
 884                                         $title = substr($title, 0, 20) . '...';
 885                                 }
 886
 887                                 $msg['title'] = $title;
 888                         }
 889                 }
 890                 $msg['body'] = $item['body'];
 891
 892                 return Mail::insert($msg);
 893         }
 894
 895         /**
 896          * Fetches missing posts
 897          *
 898          * @param string $url         message URL
 899          * @param array  $child       activity array with the child of this message
 900          * @param string $relay_actor Relay actor
 901          * @return string fetched message URL
 902          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 903          */
 904         public static function fetchMissingActivity(string $url, array $child = [], string $relay_actor = '', int $completion = Receiver::COMPLETION_MANUAL)
 905         {
 906                 if (!empty($child['receiver'])) {
 907                         $uid = ActivityPub\Receiver::getFirstUserFromReceivers($child['receiver']);
 908                 } else {
 909                         $uid = 0;
 910                 }
 911
 912                 $object = ActivityPub::fetchContent($url, $uid);
 913                 if (empty($object)) {
 914                         Logger::notice('Activity was not fetchable, aborting.', ['url' => $url]);
 915                         return '';
 916                 }
 917
 918                 if (empty($object['id'])) {
 919                         Logger::notice('Activity has got not id, aborting. ', ['url' => $url, 'object' => $object]);
 920                         return '';
 921                 }
 922
 923                 if (!empty($object['actor'])) {
 924                         $object_actor = $object['actor'];
 925                 } elseif (!empty($object['attributedTo'])) {
 926                         $object_actor = $object['attributedTo'];
 927                         if (is_array($object_actor)) {
 928                                 $compacted = JsonLD::compact($object);
 929                                 $object_actor = JsonLD::fetchElement($compacted, 'as:attributedTo', '@id');
 930                         }
 931                 } else {
 932                         // Shouldn't happen
 933                         $object_actor = '';
 934                 }
 935
 936                 $signer = [$object_actor];
 937
 938                 if (!empty($child['author'])) {
 939                         $actor = $child['author'];
 940                         $signer[] = $actor;
 941                 } else {
 942                         $actor = $object_actor;
 943                 }
 944
 945                 if (!empty($object['published'])) {
 946                         $published = $object['published'];
 947                 } elseif (!empty($child['published'])) {
 948                         $published = $child['published'];
 949                 } else {
 950                         $published = DateTimeFormat::utcNow();
 951                 }
 952
 953                 $activity = [];
 954                 $activity['@context'] = $object['@context'] ?? ActivityPub::CONTEXT;
 955                 unset($object['@context']);
 956                 $activity['id'] = $object['id'];
 957                 $activity['to'] = $object['to'] ?? [];
 958                 $activity['cc'] = $object['cc'] ?? [];
 959                 $activity['actor'] = $actor;
 960                 $activity['object'] = $object;
 961                 $activity['published'] = $published;
 962                 $activity['type'] = 'Create';
 963
 964                 $ldactivity = JsonLD::compact($activity);
 965
 966                 if (!empty($relay_actor)) {
 967                         $ldactivity['thread-completion'] = $ldactivity['from-relay'] = Contact::getIdForURL($relay_actor);
 968                         $ldactivity['completion-mode']   = Receiver::COMPLETION_RELAY;
 969                 } elseif (!empty($child['thread-completion'])) {
 970                         $ldactivity['thread-completion'] = $child['thread-completion'];
 971                         $ldactivity['completion-mode']   = $child['completion-mode'] ?? Receiver::COMPLETION_NONE;
 972                 } else {
 973                         $ldactivity['thread-completion'] = Contact::getIdForURL($actor);
 974                         $ldactivity['completion-mode']   = $completion;
 975                 }
 976
 977                 if (!empty($child['type'])) {
 978                         $ldactivity['thread-children-type'] = $child['type'];
 979                 }
 980
 981                 if (!empty($relay_actor) && !self::acceptIncomingMessage($ldactivity, $object['id'])) {
 982                         return '';
 983                 }
 984
 985                 ActivityPub\Receiver::processActivity($ldactivity, json_encode($activity), $uid, true, false, $signer);
 986
 987                 Logger::notice('Activity had been fetched and processed.', ['url' => $url, 'object' => $activity['id']]);
 988
 989                 return $activity['id'];
 990         }
 991
 992         /**
 993          * Test if incoming relay messages should be accepted
 994          *
 995          * @param array $activity activity array
 996          * @param string $id      object ID
 997          * @return boolean true if message is accepted
 998          */
 999         private static function acceptIncomingMessage(array $activity, string $id)
1000         {
1001                 if (empty($activity['as:object'])) {
1002                         Logger::info('No object field in activity - accepted', ['id' => $id]);
1003                         return true;
1004                 }
1005
1006                 $replyto = JsonLD::fetchElement($activity['as:object'], 'as:inReplyTo', '@id');
1007                 $uriid = ItemURI::getIdByURI($replyto);
1008                 if (Post::exists(['uri-id' => $uriid])) {
1009                         Logger::info('Post is a reply to an existing post - accepted', ['id' => $id, 'uri-id' => $uriid, 'replyto' => $replyto]);
1010                         return true;
1011                 }
1012
1013                 $attributed_to = JsonLD::fetchElement($activity['as:object'], 'as:attributedTo', '@id');
1014                 $authorid = Contact::getIdForURL($attributed_to);
1015
1016                 $body = HTML::toBBCode(JsonLD::fetchElement($activity['as:object'], 'as:content', '@value'));
1017
1018                 $messageTags = [];
1019                 $tags = Receiver::processTags(JsonLD::fetchElementArray($activity['as:object'], 'as:tag') ?? []);
1020                 if (!empty($tags)) {
1021                         foreach ($tags as $tag) {
1022                                 if ($tag['type'] != 'Hashtag') {
1023                                         continue;
1024                                 }
1025                                 $messageTags[] = ltrim(mb_strtolower($tag['name']), '#');
1026                         }
1027                 }
1028
1029                 return Relay::isSolicitedPost($messageTags, $body, $authorid, $id, Protocol::ACTIVITYPUB);
1030         }
1031
1032         /**
1033          * perform a "follow" request
1034          *
1035          * @param array $activity
1036          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1037          * @throws \ImagickException
1038          */
1039         public static function followUser($activity)
1040         {
1041                 $uid = User::getIdForURL($activity['object_id']);
1042                 if (empty($uid)) {
1043                         return;
1044                 }
1045
1046                 $owner = User::getOwnerDataById($uid);
1047                 if (empty($owner)) {
1048                         return;
1049                 }
1050
1051                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1052                 if (!empty($cid)) {
1053                         self::switchContact($cid);
1054                         Contact::update(['hub-verify' => $activity['id'], 'protocol' => Protocol::ACTIVITYPUB], ['id' => $cid]);
1055                 }
1056
1057                 $item = ['author-id' => Contact::getIdForURL($activity['actor']),
1058                         'author-link' => $activity['actor']];
1059
1060                 // Ensure that the contact has got the right network type
1061                 self::switchContact($item['author-id']);
1062
1063                 $result = Contact::addRelationship($owner, [], $item, false, $activity['content'] ?? '');
1064                 if ($result === true) {
1065                         ActivityPub\Transmitter::sendContactAccept($item['author-link'], $activity['id'], $owner['uid']);
1066                 }
1067
1068                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1069                 if (empty($cid)) {
1070                         return;
1071                 }
1072
1073                 if (empty($contact)) {
1074                         Contact::update(['hub-verify' => $activity['id'], 'protocol' => Protocol::ACTIVITYPUB], ['id' => $cid]);
1075                 }
1076
1077                 Logger::notice('Follow user ' . $uid . ' from contact ' . $cid . ' with id ' . $activity['id']);
1078         }
1079
1080         /**
1081          * Update the given profile
1082          *
1083          * @param array $activity
1084          * @throws \Exception
1085          */
1086         public static function updatePerson($activity)
1087         {
1088                 if (empty($activity['object_id'])) {
1089                         return;
1090                 }
1091
1092                 Logger::info('Updating profile', ['object' => $activity['object_id']]);
1093                 Contact::updateFromProbeByURL($activity['object_id']);
1094         }
1095
1096         /**
1097          * Delete the given profile
1098          *
1099          * @param array $activity
1100          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1101          */
1102         public static function deletePerson($activity)
1103         {
1104                 if (empty($activity['object_id']) || empty($activity['actor'])) {
1105                         Logger::info('Empty object id or actor.');
1106                         return;
1107                 }
1108
1109                 if ($activity['object_id'] != $activity['actor']) {
1110                         Logger::info('Object id does not match actor.');
1111                         return;
1112                 }
1113
1114                 $contacts = DBA::select('contact', ['id'], ['nurl' => Strings::normaliseLink($activity['object_id'])]);
1115                 while ($contact = DBA::fetch($contacts)) {
1116                         Contact::remove($contact['id']);
1117                 }
1118                 DBA::close($contacts);
1119
1120                 Logger::info('Deleted contact', ['object' => $activity['object_id']]);
1121         }
1122
1123         /**
1124          * Accept a follow request
1125          *
1126          * @param array $activity
1127          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1128          * @throws \ImagickException
1129          */
1130         public static function acceptFollowUser($activity)
1131         {
1132                 $uid = User::getIdForURL($activity['object_actor']);
1133                 if (empty($uid)) {
1134                         return;
1135                 }
1136
1137                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1138                 if (empty($cid)) {
1139                         Logger::info('No contact found', ['actor' => $activity['actor']]);
1140                         return;
1141                 }
1142
1143                 self::switchContact($cid);
1144
1145                 $fields = ['pending' => false];
1146
1147                 $contact = DBA::selectFirst('contact', ['rel'], ['id' => $cid]);
1148                 if ($contact['rel'] == Contact::FOLLOWER) {
1149                         $fields['rel'] = Contact::FRIEND;
1150                 }
1151
1152                 $condition = ['id' => $cid];
1153                 Contact::update($fields, $condition);
1154                 Logger::info('Accept contact request', ['contact' => $cid, 'user' => $uid]);
1155         }
1156
1157         /**
1158          * Reject a follow request
1159          *
1160          * @param array $activity
1161          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1162          * @throws \ImagickException
1163          */
1164         public static function rejectFollowUser($activity)
1165         {
1166                 $uid = User::getIdForURL($activity['object_actor']);
1167                 if (empty($uid)) {
1168                         return;
1169                 }
1170
1171                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1172                 if (empty($cid)) {
1173                         Logger::info('No contact found', ['actor' => $activity['actor']]);
1174                         return;
1175                 }
1176
1177                 self::switchContact($cid);
1178
1179                 $contact = Contact::getById($cid, ['rel']);
1180                 if ($contact['rel'] == Contact::SHARING) {
1181                         Contact::remove($cid);
1182                         Logger::info('Rejected contact request - contact removed', ['contact' => $cid, 'user' => $uid]);
1183                 } elseif ($contact['rel'] == Contact::FRIEND) {
1184                         Contact::update(['rel' => Contact::FOLLOWER], ['id' => $cid]);
1185                 } else {
1186                         Logger::info('Rejected contact request', ['contact' => $cid, 'user' => $uid]);
1187                 }
1188         }
1189
1190         /**
1191          * Undo activity like "like" or "dislike"
1192          *
1193          * @param array $activity
1194          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1195          * @throws \ImagickException
1196          */
1197         public static function undoActivity($activity)
1198         {
1199                 if (empty($activity['object_id'])) {
1200                         return;
1201                 }
1202
1203                 if (empty($activity['object_actor'])) {
1204                         return;
1205                 }
1206
1207                 $author_id = Contact::getIdForURL($activity['object_actor']);
1208                 if (empty($author_id)) {
1209                         return;
1210                 }
1211
1212                 Item::markForDeletion(['uri' => $activity['object_id'], 'author-id' => $author_id, 'gravity' => GRAVITY_ACTIVITY]);
1213         }
1214
1215         /**
1216          * Activity to remove a follower
1217          *
1218          * @param array $activity
1219          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1220          * @throws \ImagickException
1221          */
1222         public static function undoFollowUser($activity)
1223         {
1224                 $uid = User::getIdForURL($activity['object_object']);
1225                 if (empty($uid)) {
1226                         return;
1227                 }
1228
1229                 $owner = User::getOwnerDataById($uid);
1230                 if (empty($owner)) {
1231                         return;
1232                 }
1233
1234                 $cid = Contact::getIdForURL($activity['actor'], $uid);
1235                 if (empty($cid)) {
1236                         Logger::info('No contact found', ['actor' => $activity['actor']]);
1237                         return;
1238                 }
1239
1240                 self::switchContact($cid);
1241
1242                 $contact = DBA::selectFirst('contact', [], ['id' => $cid]);
1243                 if (!DBA::isResult($contact)) {
1244                         return;
1245                 }
1246
1247                 Contact::removeFollower($contact);
1248                 Logger::info('Undo following request', ['contact' => $cid, 'user' => $uid]);
1249         }
1250
1251         /**
1252          * Switches a contact to AP if needed
1253          *
1254          * @param integer $cid Contact ID
1255          * @throws \Exception
1256          */
1257         private static function switchContact($cid)
1258         {
1259                 $contact = DBA::selectFirst('contact', ['network', 'url'], ['id' => $cid]);
1260                 if (!DBA::isResult($contact) || in_array($contact['network'], [Protocol::ACTIVITYPUB, Protocol::DFRN]) || Contact::isLocal($contact['url'])) {
1261                         return;
1262                 }
1263
1264                 Logger::info('Change existing contact', ['cid' => $cid, 'previous' => $contact['network']]);
1265                 Contact::updateFromProbe($cid);
1266         }
1267
1268         /**
1269          * Collects implicit mentions like:
1270          * - the author of the parent item
1271          * - all the mentioned conversants in the parent item
1272          *
1273          * @param array $parent Item array with at least ['id', 'author-link', 'alias']
1274          * @return array
1275          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
1276          */
1277         private static function getImplicitMentionList(array $parent)
1278         {
1279                 $parent_terms = Tag::getByURIId($parent['uri-id'], [Tag::MENTION, Tag::IMPLICIT_MENTION, Tag::EXCLUSIVE_MENTION]);
1280
1281                 $parent_author = Contact::getByURL($parent['author-link'], false, ['url', 'nurl', 'alias']);
1282
1283                 $implicit_mentions = [];
1284                 if (empty($parent_author['url'])) {
1285                         Logger::notice('Author public contact unknown.', ['author-link' => $parent['author-link'], 'parent-id' => $parent['id']]);
1286                 } else {
1287                         $implicit_mentions[] = $parent_author['url'];
1288                         $implicit_mentions[] = $parent_author['nurl'];
1289                         $implicit_mentions[] = $parent_author['alias'];
1290                 }
1291
1292                 if (!empty($parent['alias'])) {
1293                         $implicit_mentions[] = $parent['alias'];
1294                 }
1295
1296                 foreach ($parent_terms as $term) {
1297                         $contact = Contact::getByURL($term['url'], false, ['url', 'nurl', 'alias']);
1298                         if (!empty($contact['url'])) {
1299                                 $implicit_mentions[] = $contact['url'];
1300                                 $implicit_mentions[] = $contact['nurl'];
1301                                 $implicit_mentions[] = $contact['alias'];
1302                         }
1303                 }
1304
1305                 return $implicit_mentions;
1306         }
1307
1308         /**
1309          * Strips from the body prepended implicit mentions
1310          *
1311          * @param string $body
1312          * @param array $parent
1313          * @return string
1314          */
1315         private static function removeImplicitMentionsFromBody(string $body, array $parent)
1316         {
1317                 if (DI::config()->get('system', 'disable_implicit_mentions')) {
1318                         return $body;
1319                 }
1320
1321                 $potential_mentions = self::getImplicitMentionList($parent);
1322
1323                 $kept_mentions = [];
1324
1325                 // Extract one prepended mention at a time from the body
1326                 while(preg_match('#^(@\[url=([^\]]+)].*?\[\/url]\s)(.*)#is', $body, $matches)) {
1327                         if (!in_array($matches[2], $potential_mentions)) {
1328                                 $kept_mentions[] = $matches[1];
1329                         }
1330
1331                         $body = $matches[3];
1332                 }
1333
1334                 // Re-appending the kept mentions to the body after extraction
1335                 $kept_mentions[] = $body;
1336
1337                 return implode('', $kept_mentions);
1338         }
1339
1340         /**
1341          * Adds links to string mentions
1342          *
1343          * @param string $body
1344          * @param array  $tags
1345          * @return string
1346          */
1347         protected static function addMentionLinks(string $body, array $tags): string
1348         {
1349                 // This prevents links to be added again to Pleroma-style mention links
1350                 $body = self::normalizeMentionLinks($body);
1351
1352                 $body = BBCode::performWithEscapedTags($body, ['url'], function ($body) use ($tags) {
1353                         foreach ($tags as $tag) {
1354                                 if (empty($tag['name']) || empty($tag['type']) || empty($tag['href']) || !in_array($tag['type'], ['Mention', 'Hashtag'])) {
1355                                         continue;
1356                                 }
1357
1358                                 $hash = substr($tag['name'], 0, 1);
1359                                 $name = substr($tag['name'], 1);
1360                                 if (!in_array($hash, Tag::TAG_CHARACTER)) {
1361                                         $hash = '';
1362                                         $name = $tag['name'];
1363                                 }
1364
1365                                 $body = str_replace($tag['name'], $hash . '[url=' . $tag['href'] . ']' . $name . '[/url]', $body);
1366                         }
1367
1368                         return $body;
1369                 });
1370
1371                 return $body;
1372         }
1373 }