src/Protocol/ActivityPub/Receiver.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\Database\DBA;
  26 use Friendica\Content\Text\HTML;
  27 use Friendica\Content\Text\Markdown;
  28 use Friendica\Core\Logger;
  29 use Friendica\Core\Protocol;
  30 use Friendica\Model\Contact;
  31 use Friendica\Model\APContact;
  32 use Friendica\Model\Item;
  33 use Friendica\Model\Post;
  34 use Friendica\Model\User;
  35 use Friendica\Protocol\Activity;
  36 use Friendica\Protocol\ActivityPub;
  37 use Friendica\Util\HTTPSignature;
  38 use Friendica\Util\JsonLD;
  39 use Friendica\Util\LDSignature;
  40 use Friendica\Util\Strings;
  41
  42 /**
  43  * ActivityPub Receiver Protocol class
  44  *
  45  * To-Do:
  46  * @todo Undo Announce
  47  *
  48  * Check what this is meant to do:
  49  * - Add
  50  * - Block
  51  * - Flag
  52  * - Remove
  53  * - Undo Block
  54  */
  55 class Receiver
  56 {
  57         const PUBLIC_COLLECTION = 'as:Public';
  58         const ACCOUNT_TYPES = ['as:Person', 'as:Organization', 'as:Service', 'as:Group', 'as:Application'];
  59         const CONTENT_TYPES = ['as:Note', 'as:Article', 'as:Video', 'as:Image', 'as:Event', 'as:Audio', 'as:Page', 'as:Question'];
  60         const ACTIVITY_TYPES = ['as:Like', 'as:Dislike', 'as:Accept', 'as:Reject', 'as:TentativeAccept'];
  61
  62         const TARGET_UNKNOWN = 0;
  63         const TARGET_TO = 1;
  64         const TARGET_CC = 2;
  65         const TARGET_BTO = 3;
  66         const TARGET_BCC = 4;
  67         const TARGET_FOLLOWER = 5;
  68         const TARGET_ANSWER = 6;
  69         const TARGET_GLOBAL = 7;
  70
  71         /**
  72          * Checks incoming message from the inbox
  73          *
  74          * @param         $body
  75          * @param         $header
  76          * @param integer $uid User ID
  77          * @throws \Exception
  78          */
  79         public static function processInbox($body, $header, $uid)
  80         {
  81                 $activity = json_decode($body, true);
  82                 if (empty($activity)) {
  83                         Logger::warning('Invalid body.');
  84                         return;
  85                 }
  86
  87                 $ldactivity = JsonLD::compact($activity);
  88
  89                 $actor = JsonLD::fetchElement($ldactivity, 'as:actor', '@id');
  90
  91                 $apcontact = APContact::getByURL($actor);
  92                 if (empty($apcontact)) {
  93                         Logger::notice('Unable to retrieve AP contact for actor - message is discarded', ['actor' => $actor]);
  94                         return;
  95                 } elseif ($apcontact['type'] == 'Application' && $apcontact['nick'] == 'relay') {
  96                         self::processRelayPost($ldactivity, $actor);
  97                         return;
  98                 } else {
  99                         APContact::unmarkForArchival($apcontact);
 100                 }
 101
 102                 $http_signer = HTTPSignature::getSigner($body, $header);
 103                 if ($http_signer === false) {
 104                         Logger::warning('Invalid HTTP signature, message will be discarded.');
 105                         return;
 106                 } elseif (empty($http_signer)) {
 107                         Logger::info('Signer is a tombstone. The message will be discarded, the signer account is deleted.');
 108                         return;
 109                 } else {
 110                         Logger::info('Valid HTTP signature', ['signer' => $http_signer]);
 111                 }
 112
 113                 $signer = [$http_signer];
 114
 115                 Logger::info('Message for user ' . $uid . ' is from actor ' . $actor);
 116
 117                 if (LDSignature::isSigned($activity)) {
 118                         $ld_signer = LDSignature::getSigner($activity);
 119                         if (empty($ld_signer)) {
 120                                 Logger::info('Invalid JSON-LD signature from ' . $actor);
 121                         } elseif ($ld_signer != $http_signer) {
 122                                 $signer[] = $ld_signer;
 123                         }
 124                         if (!empty($ld_signer && ($actor == $http_signer))) {
 125                                 Logger::info('The HTTP and the JSON-LD signature belong to ' . $ld_signer);
 126                                 $trust_source = true;
 127                         } elseif (!empty($ld_signer)) {
 128                                 Logger::info('JSON-LD signature is signed by ' . $ld_signer);
 129                                 $trust_source = true;
 130                         } elseif ($actor == $http_signer) {
 131                                 Logger::info('Bad JSON-LD signature, but HTTP signer fits the actor.');
 132                                 $trust_source = true;
 133                         } else {
 134                                 Logger::info('Invalid JSON-LD signature and the HTTP signer is different.');
 135                                 $trust_source = false;
 136                         }
 137                 } elseif ($actor == $http_signer) {
 138                         Logger::info('Trusting post without JSON-LD signature, The actor fits the HTTP signer.');
 139                         $trust_source = true;
 140                 } else {
 141                         Logger::info('No JSON-LD signature, different actor.');
 142                         $trust_source = false;
 143                 }
 144
 145                 self::processActivity($ldactivity, $body, $uid, $trust_source, true, $signer);
 146         }
 147
 148         /**
 149          * Process incoming posts from relays
 150          *
 151          * @param array  $activity
 152          * @param string $actor
 153          * @return void
 154          */
 155         private static function processRelayPost(array $activity, string $actor)
 156         {
 157                 $type = JsonLD::fetchElement($activity, '@type');
 158                 if (!$type) {
 159                         Logger::info('Empty type', ['activity' => $activity]);
 160                         return;
 161                 }
 162
 163                 if ($type != 'as:Announce') {
 164                         Logger::info('Not an announcement', ['activity' => $activity]);
 165                         return;
 166                 }
 167
 168                 $object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
 169                 if (empty($object_id)) {
 170                         Logger::info('No object id found', ['activity' => $activity]);
 171                         return;
 172                 }
 173
 174                 $contact = Contact::getByURL($actor);
 175                 if (empty($contact)) {
 176                         Logger::info('Relay contact not found', ['actor' => $actor]);
 177                         return;
 178                 }
 179
 180                 if (!in_array($contact['rel'], [Contact::SHARING, Contact::FRIEND])) {
 181                         Logger::notice('Relay is no sharer', ['actor' => $actor]);
 182                         return;
 183                 }
 184
 185                 Logger::info('Got relayed message id', ['id' => $object_id]);
 186
 187                 $item_id = Item::searchByLink($object_id);
 188                 if ($item_id) {
 189                         Logger::info('Relayed message already exists', ['id' => $object_id, 'item' => $item_id]);
 190                         return;
 191                 }
 192
 193                 $id = Processor::fetchMissingActivity($object_id, [], $actor);
 194                 if (empty($id)) {
 195                         Logger::notice('Relayed message had not been fetched', ['id' => $object_id]);
 196                         return;
 197                 }
 198
 199                 $item_id = Item::searchByLink($object_id);
 200                 if ($item_id) {
 201                         Logger::info('Relayed message had been fetched and stored', ['id' => $object_id, 'item' => $item_id]);
 202                 } else {
 203                         Logger::notice('Relayed message had not been stored', ['id' => $object_id]);
 204                 }
 205         }
 206
 207         /**
 208          * Fetches the object type for a given object id
 209          *
 210          * @param array   $activity
 211          * @param string  $object_id Object ID of the the provided object
 212          * @param integer $uid       User ID
 213          *
 214          * @return string with object type
 215          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 216          * @throws \ImagickException
 217          */
 218         private static function fetchObjectType($activity, $object_id, $uid = 0)
 219         {
 220                 if (!empty($activity['as:object'])) {
 221                         $object_type = JsonLD::fetchElement($activity['as:object'], '@type');
 222                         if (!empty($object_type)) {
 223                                 return $object_type;
 224                         }
 225                 }
 226
 227                 if (Post::exists(['uri' => $object_id, 'gravity' => [GRAVITY_PARENT, GRAVITY_COMMENT]])) {
 228                         // We just assume "note" since it doesn't make a difference for the further processing
 229                         return 'as:Note';
 230                 }
 231
 232                 $profile = APContact::getByURL($object_id);
 233                 if (!empty($profile['type'])) {
 234                         APContact::unmarkForArchival($profile);
 235                         return 'as:' . $profile['type'];
 236                 }
 237
 238                 $data = ActivityPub::fetchContent($object_id, $uid);
 239                 if (!empty($data)) {
 240                         $object = JsonLD::compact($data);
 241                         $type = JsonLD::fetchElement($object, '@type');
 242                         if (!empty($type)) {
 243                                 return $type;
 244                         }
 245                 }
 246
 247                 return null;
 248         }
 249
 250         /**
 251          * Prepare the object array
 252          *
 253          * @param array   $activity     Array with activity data
 254          * @param integer $uid          User ID
 255          * @param boolean $push         Message had been pushed to our system
 256          * @param boolean $trust_source Do we trust the source?
 257          *
 258          * @return array with object data
 259          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 260          * @throws \ImagickException
 261          */
 262         public static function prepareObjectData($activity, $uid, $push, &$trust_source)
 263         {
 264                 $id = JsonLD::fetchElement($activity, '@id');
 265                 if (!empty($id) && !$trust_source) {
 266                         if (empty($uid)) {
 267                                 $actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
 268                                 if (empty($actor)) {
 269                                         $actor = '';
 270                                 }
 271
 272                                 // Fetch a user out of the receivers of the message.
 273                                 $fetch_uid = Receiver::getBestUserForActivity($activity, $actor);
 274                         } else {
 275                                 $fetch_uid = $uid;
 276                         }
 277
 278                         $fetched_activity = ActivityPub::fetchContent($id, $fetch_uid);
 279                         if (!empty($fetched_activity)) {
 280                                 $object = JsonLD::compact($fetched_activity);
 281                                 $fetched_id = JsonLD::fetchElement($object, '@id');
 282                                 if ($fetched_id == $id) {
 283                                         Logger::info('Activity had been fetched successfully', ['id' => $id]);
 284                                         $trust_source = true;
 285                                         $activity = $object;
 286                                 } else {
 287                                         Logger::info('Activity id is not equal', ['id' => $id, 'fetched' => $fetched_id]);
 288                                 }
 289                         } else {
 290                                 Logger::info('Activity could not been fetched', ['id' => $id]);
 291                         }
 292                 }
 293
 294                 $actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
 295                 if (empty($actor)) {
 296                         Logger::info('Empty actor', ['activity' => $activity]);
 297                         return [];
 298                 }
 299
 300                 $type = JsonLD::fetchElement($activity, '@type');
 301
 302                 // Fetch all receivers from to, cc, bto and bcc
 303                 $receiverdata = self::getReceivers($activity, $actor);
 304                 $receivers = $reception_types = [];
 305                 foreach ($receiverdata as $key => $data) {
 306                         $receivers[$key] = $data['uid'];
 307                         $reception_types[$data['uid']] = $data['type'] ?? self::TARGET_UNKNOWN;
 308                 }
 309
 310                 // When it is a delivery to a personal inbox we add that user to the receivers
 311                 if (!empty($uid)) {
 312                         $additional = [$uid => $uid];
 313                         $receivers = array_replace($receivers, $additional);
 314                         if (empty($activity['thread-completion']) && (empty($reception_types[$uid]) || in_array($reception_types[$uid], [self::TARGET_UNKNOWN, self::TARGET_FOLLOWER, self::TARGET_ANSWER, self::TARGET_GLOBAL]))) {
 315                                 $reception_types[$uid] = self::TARGET_BCC;
 316                         }
 317                 } else {
 318                         // We possibly need some user to fetch private content,
 319                         // so we fetch the first out ot the list.
 320                         $uid = self::getFirstUserFromReceivers($receivers);
 321                 }
 322
 323                 $object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
 324                 if (empty($object_id)) {
 325                         Logger::info('No object found');
 326                         return [];
 327                 }
 328
 329                 if (!is_string($object_id)) {
 330                         Logger::info('Invalid object id', ['object' => $object_id]);
 331                         return [];
 332                 }
 333
 334                 $object_type = self::fetchObjectType($activity, $object_id, $uid);
 335
 336                 // Fetch the activity on Lemmy "Announce" messages (announces of activities)
 337                 if (($type == 'as:Announce') && in_array($object_type, array_merge(self::ACTIVITY_TYPES, ['as:Delete', 'as:Undo', 'as:Update']))) {
 338                         $data = ActivityPub::fetchContent($object_id, $uid);
 339                         if (!empty($data)) {
 340                                 $type = $object_type;
 341                                 $activity = JsonLD::compact($data);
 342
 343                                 // Some variables need to be refetched since the activity changed
 344                                 $actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
 345                                 $object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
 346                                 $object_type = self::fetchObjectType($activity, $object_id, $uid);
 347                         }
 348                 }
 349
 350                 // Any activities on account types must not be altered
 351                 if (in_array($object_type, self::ACCOUNT_TYPES)) {
 352                         $object_data = [];
 353                         $object_data['id'] = JsonLD::fetchElement($activity, '@id');
 354                         $object_data['object_id'] = JsonLD::fetchElement($activity, 'as:object', '@id');
 355                         $object_data['object_actor'] = JsonLD::fetchElement($activity['as:object'], 'as:actor', '@id');
 356                         $object_data['object_object'] = JsonLD::fetchElement($activity['as:object'], 'as:object');
 357                         $object_data['object_type'] = JsonLD::fetchElement($activity['as:object'], '@type');
 358                         $object_data['push'] = $push;
 359                 } elseif (in_array($type, ['as:Create', 'as:Update', 'as:Announce']) || strpos($type, '#emojiReaction')) {
 360                 // Fetch the content only on activities where this matters
 361                 // We can receive "#emojiReaction" when fetching content from Hubzilla systems
 362                         // Always fetch on "Announce"
 363                         $object_data = self::fetchObject($object_id, $activity['as:object'], $trust_source && ($type != 'as:Announce'), $uid);
 364                         if (empty($object_data)) {
 365                                 Logger::info("Object data couldn't be processed");
 366                                 return [];
 367                         }
 368
 369                         $object_data['object_id'] = $object_id;
 370
 371                         if ($type == 'as:Announce') {
 372                                 $object_data['push'] = false;
 373                         } else {
 374                                 $object_data['push'] = $push;
 375                         }
 376
 377                         // Test if it is an answer to a mail
 378                         if (DBA::exists('mail', ['uri' => $object_data['reply-to-id']])) {
 379                                 $object_data['directmessage'] = true;
 380                         } else {
 381                                 $object_data['directmessage'] = JsonLD::fetchElement($activity, 'litepub:directMessage');
 382                         }
 383                 } elseif (in_array($type, array_merge(self::ACTIVITY_TYPES, ['as:Follow'])) && in_array($object_type, self::CONTENT_TYPES)) {
 384                         // Create a mostly empty array out of the activity data (instead of the object).
 385                         // This way we later don't have to check for the existence of each individual array element.
 386                         $object_data = self::processObject($activity);
 387                         $object_data['name'] = $type;
 388                         $object_data['author'] = JsonLD::fetchElement($activity, 'as:actor', '@id');
 389                         $object_data['object_id'] = $object_id;
 390                         $object_data['object_type'] = ''; // Since we don't fetch the object, we don't know the type
 391                         $object_data['push'] = $push;
 392                 } elseif (in_array($type, ['as:Add'])) {
 393                         $object_data = [];
 394                         $object_data['id'] = JsonLD::fetchElement($activity, '@id');
 395                         $object_data['target_id'] = JsonLD::fetchElement($activity, 'as:target', '@id');
 396                         $object_data['object_id'] = JsonLD::fetchElement($activity, 'as:object', '@id');
 397                         $object_data['object_type'] = JsonLD::fetchElement($activity['as:object'], '@type');
 398                         $object_data['object_content'] = JsonLD::fetchElement($activity['as:object'], 'as:content', '@type');
 399                         $object_data['push'] = $push;
 400                 } else {
 401                         $object_data = [];
 402                         $object_data['id'] = JsonLD::fetchElement($activity, '@id');
 403                         $object_data['object_id'] = JsonLD::fetchElement($activity, 'as:object', '@id');
 404                         $object_data['object_actor'] = JsonLD::fetchElement($activity['as:object'], 'as:actor', '@id');
 405                         $object_data['object_object'] = JsonLD::fetchElement($activity['as:object'], 'as:object');
 406                         $object_data['object_type'] = JsonLD::fetchElement($activity['as:object'], '@type');
 407                         $object_data['push'] = $push;
 408
 409                         // An Undo is done on the object of an object, so we need that type as well
 410                         if (($type == 'as:Undo') && !empty($object_data['object_object'])) {
 411                                 $object_data['object_object_type'] = self::fetchObjectType([], $object_data['object_object'], $uid);
 412                         }
 413                 }
 414
 415                 $object_data = self::addActivityFields($object_data, $activity);
 416
 417                 if (empty($object_data['object_type'])) {
 418                         $object_data['object_type'] = $object_type;
 419                 }
 420
 421                 $object_data['type'] = $type;
 422                 $object_data['actor'] = $actor;
 423                 $object_data['item_receiver'] = $receivers;
 424                 $object_data['receiver'] = array_replace($object_data['receiver'] ?? [], $receivers);
 425                 $object_data['reception_type'] = array_replace($object_data['reception_type'] ?? [], $reception_types);
 426
 427                 $author = $object_data['author'] ?? $actor;
 428                 if (!empty($author) && !empty($object_data['id'])) {
 429                         $author_host = parse_url($author, PHP_URL_HOST);
 430                         $id_host = parse_url($object_data['id'], PHP_URL_HOST);
 431                         if ($author_host == $id_host) {
 432                                 Logger::info('Valid hosts', ['type' => $type, 'host' => $id_host]);
 433                         } else {
 434                                 Logger::notice('Differing hosts on author and id', ['type' => $type, 'author' => $author_host, 'id' => $id_host]);
 435                                 $trust_source = false;
 436                         }
 437                 }
 438
 439                 Logger::info('Processing ' . $object_data['type'] . ' ' . $object_data['object_type'] . ' ' . $object_data['id']);
 440
 441                 return $object_data;
 442         }
 443
 444         /**
 445          * Fetches the first user id from the receiver array
 446          *
 447          * @param array $receivers Array with receivers
 448          * @return integer user id;
 449          */
 450         public static function getFirstUserFromReceivers($receivers)
 451         {
 452                 foreach ($receivers as $receiver) {
 453                         if (!empty($receiver)) {
 454                                 return $receiver;
 455                         }
 456                 }
 457                 return 0;
 458         }
 459
 460         /**
 461          * Processes the activity object
 462          *
 463          * @param array   $activity     Array with activity data
 464          * @param string  $body
 465          * @param integer $uid          User ID
 466          * @param boolean $trust_source Do we trust the source?
 467          * @param boolean $push         Message had been pushed to our system
 468          * @throws \Exception
 469          */
 470         public static function processActivity($activity, string $body = '', int $uid = null, bool $trust_source = false, bool $push = false, array $signer = [])
 471         {
 472                 $type = JsonLD::fetchElement($activity, '@type');
 473                 if (!$type) {
 474                         Logger::info('Empty type', ['activity' => $activity]);
 475                         return;
 476                 }
 477
 478                 if (!JsonLD::fetchElement($activity, 'as:object', '@id')) {
 479                         Logger::info('Empty object', ['activity' => $activity]);
 480                         return;
 481                 }
 482
 483                 $actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
 484                 if (empty($actor)) {
 485                         Logger::info('Empty actor', ['activity' => $activity]);
 486                         return;
 487                 }
 488
 489                 if (is_array($activity['as:object'])) {
 490                         $attributed_to = JsonLD::fetchElement($activity['as:object'], 'as:attributedTo', '@id');
 491                 } else {
 492                         $attributed_to = '';
 493                 }
 494
 495                 // Test the provided signatures against the actor and "attributedTo"
 496                 if ($trust_source) {
 497                         if (!empty($attributed_to) && !empty($actor)) {
 498                                 $trust_source = (in_array($actor, $signer) && in_array($attributed_to, $signer));
 499                         } else {
 500                                 $trust_source = in_array($actor, $signer);
 501                         }
 502                 }
 503
 504                 // $trust_source is called by reference and is set to true if the content was retrieved successfully
 505                 $object_data = self::prepareObjectData($activity, $uid, $push, $trust_source);
 506                 if (empty($object_data)) {
 507                         Logger::info('No object data found', ['activity' => $activity]);
 508                         return;
 509                 }
 510
 511                 // Lemmy is announcing activities.
 512                 // We are changing the announces into regular activities.
 513                 if (($type == 'as:Announce') && in_array($object_data['type'] ?? '', array_merge(self::ACTIVITY_TYPES, ['as:Delete', 'as:Undo', 'as:Update']))) {
 514                         $type = $object_data['type'];
 515                 }
 516
 517                 if (!$trust_source) {
 518                         Logger::info('Activity trust could not be achieved.',  ['id' => $object_data['object_id'], 'type' => $type, 'signer' => $signer, 'actor' => $actor, 'attributedTo' => $attributed_to]);
 519                         return;
 520                 }
 521
 522                 if (!empty($body) && empty($object_data['raw'])) {
 523                         $object_data['raw'] = $body;
 524                 }
 525
 526                 // Internal flag for thread completion. See Processor.php
 527                 if (!empty($activity['thread-completion'])) {
 528                         $object_data['thread-completion'] = $activity['thread-completion'];
 529                 }
 530                 if (!empty($activity['thread-children-type'])) {
 531                         $object_data['thread-children-type'] = $activity['thread-children-type'];
 532                 }
 533
 534                 // Internal flag for posts that arrived via relay
 535                 if (!empty($activity['from-relay'])) {
 536                         $object_data['from-relay'] = $activity['from-relay'];
 537                 }
 538
 539                 switch ($type) {
 540                         case 'as:Create':
 541                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 542                                         $item = ActivityPub\Processor::createItem($object_data);
 543                                         ActivityPub\Processor::postItem($object_data, $item);
 544                                 }
 545                                 break;
 546
 547                         case 'as:Add':
 548                                 if ($object_data['object_type'] == 'as:tag') {
 549                                         ActivityPub\Processor::addTag($object_data);
 550                                 }
 551                                 break;
 552
 553                         case 'as:Announce':
 554                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 555                                         $object_data['thread-completion'] = Contact::getIdForURL($actor);
 556
 557                                         $item = ActivityPub\Processor::createItem($object_data);
 558                                         if (empty($item)) {
 559                                                 return;
 560                                         }
 561
 562                                         $item['post-reason'] = Item::PR_ANNOUNCEMENT;
 563                                         ActivityPub\Processor::postItem($object_data, $item);
 564
 565                                         $announce_object_data = self::processObject($activity);
 566                                         $announce_object_data['name'] = $type;
 567                                         $announce_object_data['author'] = JsonLD::fetchElement($activity, 'as:actor', '@id');
 568                                         $announce_object_data['object_id'] = $object_data['object_id'];
 569                                         $announce_object_data['object_type'] = $object_data['object_type'];
 570                                         $announce_object_data['push'] = $push;
 571
 572                                         if (!empty($body)) {
 573                                                 $announce_object_data['raw'] = $body;
 574                                         }
 575
 576                                         ActivityPub\Processor::createActivity($announce_object_data, Activity::ANNOUNCE);
 577                                 }
 578                                 break;
 579
 580                         case 'as:Like':
 581                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 582                                         ActivityPub\Processor::createActivity($object_data, Activity::LIKE);
 583                                 }
 584                                 break;
 585
 586                         case 'as:Dislike':
 587                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 588                                         ActivityPub\Processor::createActivity($object_data, Activity::DISLIKE);
 589                                 }
 590                                 break;
 591
 592                         case 'as:TentativeAccept':
 593                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 594                                         ActivityPub\Processor::createActivity($object_data, Activity::ATTENDMAYBE);
 595                                 }
 596                                 break;
 597
 598                         case 'as:Update':
 599                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 600                                         ActivityPub\Processor::updateItem($object_data);
 601                                 } elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 602                                         ActivityPub\Processor::updatePerson($object_data);
 603                                 }
 604                                 break;
 605
 606                         case 'as:Delete':
 607                                 if ($object_data['object_type'] == 'as:Tombstone') {
 608                                         ActivityPub\Processor::deleteItem($object_data);
 609                                 } elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 610                                         ActivityPub\Processor::deletePerson($object_data);
 611                                 }
 612                                 break;
 613
 614                         case 'as:Follow':
 615                                 if (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 616                                         ActivityPub\Processor::followUser($object_data);
 617                                 } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 618                                         $object_data['reply-to-id'] = $object_data['object_id'];
 619                                         ActivityPub\Processor::createActivity($object_data, Activity::FOLLOW);
 620                                 }
 621                                 break;
 622
 623                         case 'as:Accept':
 624                                 if ($object_data['object_type'] == 'as:Follow') {
 625                                         ActivityPub\Processor::acceptFollowUser($object_data);
 626                                 } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 627                                         ActivityPub\Processor::createActivity($object_data, Activity::ATTEND);
 628                                 }
 629                                 break;
 630
 631                         case 'as:Reject':
 632                                 if ($object_data['object_type'] == 'as:Follow') {
 633                                         ActivityPub\Processor::rejectFollowUser($object_data);
 634                                 } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 635                                         ActivityPub\Processor::createActivity($object_data, Activity::ATTENDNO);
 636                                 }
 637                                 break;
 638
 639                         case 'as:Undo':
 640                                 if (($object_data['object_type'] == 'as:Follow') &&
 641                                         in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
 642                                         ActivityPub\Processor::undoFollowUser($object_data);
 643                                 } elseif (($object_data['object_type'] == 'as:Accept') &&
 644                                         in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
 645                                         ActivityPub\Processor::rejectFollowUser($object_data);
 646                                 } elseif (in_array($object_data['object_type'], self::ACTIVITY_TYPES) &&
 647                                         in_array($object_data['object_object_type'], self::CONTENT_TYPES)) {
 648                                         ActivityPub\Processor::undoActivity($object_data);
 649                                 }
 650                                 break;
 651
 652                         default:
 653                                 Logger::info('Unknown activity: ' . $type . ' ' . $object_data['object_type']);
 654                                 break;
 655                 }
 656         }
 657
 658         /**
 659          * Fetch a user id from an activity array
 660          *
 661          * @param array  $activity
 662          * @param string $actor
 663          *
 664          * @return int   user id
 665          */
 666         private static function getBestUserForActivity(array $activity, string $actor)
 667         {
 668                 $uid = 0;
 669                 $receivers = self::getReceivers($activity, $actor);
 670                 foreach ($receivers as $receiver) {
 671                         if ($receiver['type'] == self::TARGET_GLOBAL) {
 672                                 return 0;
 673                         }
 674                         if (empty($uid) || ($receiver['type'] == self::TARGET_TO)) {
 675                                 $uid = $receiver['uid'];
 676                         }
 677                 }
 678                 return $uid;
 679         }
 680
 681         /**
 682          * Fetch the receiver list from an activity array
 683          *
 684          * @param array   $activity
 685          * @param string  $actor
 686          * @param array   $tags
 687          * @param boolean $fetch_unlisted
 688          *
 689          * @return array with receivers (user id)
 690          * @throws \Exception
 691          */
 692         private static function getReceivers($activity, $actor, $tags = [], $fetch_unlisted = false)
 693         {
 694                 $reply = $receivers = [];
 695
 696                 // When it is an answer, we inherite the receivers from the parent
 697                 $replyto = JsonLD::fetchElement($activity, 'as:inReplyTo', '@id');
 698                 if (!empty($replyto)) {
 699                         $reply = [$replyto];
 700
 701                         // Fix possibly wrong item URI (could be an answer to a plink uri)
 702                         $fixedReplyTo = Item::getURIByLink($replyto);
 703                         if (!empty($fixedReplyTo)) {
 704                                 $reply[] = $fixedReplyTo;
 705                         }
 706                 }
 707
 708                 // Fetch all posts that refer to the object id
 709                 $object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
 710                 if (!empty($object_id)) {
 711                         $reply[] = $object_id;
 712                 }
 713
 714                 if (!empty($reply)) {
 715                         $parents = Post::select(['uid'], ['uri' => $reply]);
 716                         while ($parent = Post::fetch($parents)) {
 717                                 $receivers[$parent['uid']] = ['uid' => $parent['uid'], 'type' => self::TARGET_ANSWER];
 718                         }
 719                         DBA::close($parents);
 720                 }
 721
 722                 if (!empty($actor)) {
 723                         $profile   = APContact::getByURL($actor);
 724                         $followers = $profile['followers'] ?? '';
 725                         $is_forum  = ($actor['type'] ?? '') == 'Group';
 726                         Logger::info('Got actor and followers', ['actor' => $actor, 'followers' => $followers]);
 727                 } else {
 728                         Logger::info('Empty actor', ['activity' => $activity]);
 729                         $followers = '';
 730                         $is_forum  = false;
 731                 }
 732
 733                 // We have to prevent false follower assumptions upon thread completions
 734                 $follower_target = empty($activity['thread-completion']) ? self::TARGET_FOLLOWER : self::TARGET_UNKNOWN;
 735
 736                 foreach (['as:to', 'as:cc', 'as:bto', 'as:bcc'] as $element) {
 737                         $receiver_list = JsonLD::fetchElementArray($activity, $element, '@id');
 738                         if (empty($receiver_list)) {
 739                                 continue;
 740                         }
 741
 742                         foreach ($receiver_list as $receiver) {
 743                                 if ($receiver == self::PUBLIC_COLLECTION) {
 744                                         $receivers[0] = ['uid' => 0, 'type' => self::TARGET_GLOBAL];
 745                                 }
 746
 747                                 // Add receiver "-1" for unlisted posts
 748                                 if ($fetch_unlisted && ($receiver == self::PUBLIC_COLLECTION) && ($element == 'as:cc')) {
 749                                         $receivers[-1] = ['uid' => -1, 'type' => self::TARGET_GLOBAL];
 750                                 }
 751
 752                                 // Fetch the receivers for the public and the followers collection
 753                                 if ((($receiver == $followers) || (($receiver == self::PUBLIC_COLLECTION) && !$is_forum)) && !empty($actor)) {
 754                                         $receivers = self::getReceiverForActor($actor, $tags, $receivers, $follower_target);
 755                                         continue;
 756                                 }
 757
 758                                 // Fetching all directly addressed receivers
 759                                 $condition = ['self' => true, 'nurl' => Strings::normaliseLink($receiver)];
 760                                 $contact = DBA::selectFirst('contact', ['uid', 'contact-type'], $condition);
 761                                 if (!DBA::isResult($contact)) {
 762                                         continue;
 763                                 }
 764
 765                                 // Check if the potential receiver is following the actor
 766                                 // Exception: The receiver is targetted via "to" or this is a comment
 767                                 if ((($element != 'as:to') && empty($replyto)) || ($contact['contact-type'] == Contact::TYPE_COMMUNITY)) {
 768                                         $networks = Protocol::FEDERATED;
 769                                         $condition = ['nurl' => Strings::normaliseLink($actor), 'rel' => [Contact::SHARING, Contact::FRIEND],
 770                                                 'network' => $networks, 'archive' => false, 'pending' => false, 'uid' => $contact['uid']];
 771
 772                                         // Forum posts are only accepted from forum contacts
 773                                         if ($contact['contact-type'] == Contact::TYPE_COMMUNITY) {
 774                                                 $condition['rel'] = [Contact::SHARING, Contact::FRIEND, Contact::FOLLOWER];
 775                                         }
 776
 777                                         if (!DBA::exists('contact', $condition)) {
 778                                                 continue;
 779                                         }
 780                                 }
 781
 782                                 $type = $receivers[$contact['uid']]['type'] ?? self::TARGET_UNKNOWN;
 783                                 if (in_array($type, [self::TARGET_UNKNOWN, self::TARGET_FOLLOWER, self::TARGET_ANSWER, self::TARGET_GLOBAL])) {
 784                                         switch ($element) {
 785                                                 case 'as:to':
 786                                                         $type = self::TARGET_TO;
 787                                                         break;
 788                                                 case 'as:cc':
 789                                                         $type = self::TARGET_CC;
 790                                                         break;
 791                                                 case 'as:bto':
 792                                                         $type = self::TARGET_BTO;
 793                                                         break;
 794                                                 case 'as:bcc':
 795                                                         $type = self::TARGET_BCC;
 796                                                         break;
 797                                         }
 798
 799                                         $receivers[$contact['uid']] = ['uid' => $contact['uid'], 'type' => $type];
 800                                 }
 801                         }
 802                 }
 803
 804                 self::switchContacts($receivers, $actor);
 805
 806                 return $receivers;
 807         }
 808
 809         /**
 810          * Fetch the receiver list of a given actor
 811          *
 812          * @param string  $actor
 813          * @param array   $tags
 814          * @param array   $receivers
 815          * @param integer $target_type
 816          *
 817          * @return array with receivers (user id)
 818          * @throws \Exception
 819          */
 820         private static function getReceiverForActor($actor, $tags, $receivers, $target_type)
 821         {
 822                 $basecondition = ['rel' => [Contact::SHARING, Contact::FRIEND, Contact::FOLLOWER],
 823                         'network' => Protocol::FEDERATED, 'archive' => false, 'pending' => false];
 824
 825                 $condition = DBA::mergeConditions($basecondition, ["`nurl` = ? AND `uid` != ?", Strings::normaliseLink($actor), 0]);
 826                 $contacts = DBA::select('contact', ['uid', 'rel'], $condition);
 827                 while ($contact = DBA::fetch($contacts)) {
 828                         if (empty($receivers[$contact['uid']]) && self::isValidReceiverForActor($contact, $tags)) {
 829                                 $receivers[$contact['uid']] = ['uid' => $contact['uid'], 'type' => $target_type];
 830                         }
 831                 }
 832                 DBA::close($contacts);
 833
 834                 // The queries are split because of performance issues
 835                 $condition = DBA::mergeConditions($basecondition, ["`alias` IN (?, ?) AND `uid` != ?", Strings::normaliseLink($actor), $actor, 0]);
 836                 $contacts = DBA::select('contact', ['uid', 'rel'], $condition);
 837                 while ($contact = DBA::fetch($contacts)) {
 838                         if (empty($receivers[$contact['uid']]) && self::isValidReceiverForActor($contact, $tags)) {
 839                                 $receivers[$contact['uid']] = ['uid' => $contact['uid'], 'type' => $target_type];
 840                         }
 841                 }
 842                 DBA::close($contacts);
 843                 return $receivers;
 844         }
 845
 846         /**
 847          * Tests if the contact is a valid receiver for this actor
 848          *
 849          * @param array  $contact
 850          * @param string $actor
 851          * @param array  $tags
 852          *
 853          * @return bool with receivers (user id)
 854          * @throws \Exception
 855          */
 856         private static function isValidReceiverForActor($contact, $tags)
 857         {
 858                 // Are we following the contact? Then this is a valid receiver
 859                 if (in_array($contact['rel'], [Contact::SHARING, Contact::FRIEND])) {
 860                         return true;
 861                 }
 862
 863                 // When the possible receiver isn't a community, then it is no valid receiver
 864                 $owner = User::getOwnerDataById($contact['uid']);
 865                 if (empty($owner) || ($owner['contact-type'] != Contact::TYPE_COMMUNITY)) {
 866                         return false;
 867                 }
 868
 869                 // Is the community account tagged?
 870                 foreach ($tags as $tag) {
 871                         if ($tag['type'] != 'Mention') {
 872                                 continue;
 873                         }
 874
 875                         if (Strings::compareLink($tag['href'], $owner['url'])) {
 876                                 return true;
 877                         }
 878                 }
 879
 880                 return false;
 881         }
 882
 883         /**
 884          * Switches existing contacts to ActivityPub
 885          *
 886          * @param integer $cid Contact ID
 887          * @param integer $uid User ID
 888          * @param string  $url Profile URL
 889          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 890          * @throws \ImagickException
 891          */
 892         public static function switchContact($cid, $uid, $url)
 893         {
 894                 if (DBA::exists('contact', ['id' => $cid, 'network' => Protocol::ACTIVITYPUB])) {
 895                         Logger::info('Contact is already ActivityPub', ['id' => $cid, 'uid' => $uid, 'url' => $url]);
 896                         return;
 897                 }
 898
 899                 if (Contact::updateFromProbe($cid)) {
 900                         Logger::info('Update was successful', ['id' => $cid, 'uid' => $uid, 'url' => $url]);
 901                 }
 902
 903                 // Send a new follow request to be sure that the connection still exists
 904                 if (($uid != 0) && DBA::exists('contact', ['id' => $cid, 'rel' => [Contact::SHARING, Contact::FRIEND], 'network' => Protocol::ACTIVITYPUB])) {
 905                         Logger::info('Contact had been switched to ActivityPub. Sending a new follow request.', ['uid' => $uid, 'url' => $url]);
 906                         ActivityPub\Transmitter::sendActivity('Follow', $url, $uid);
 907                 }
 908         }
 909
 910         /**
 911          *
 912          *
 913          * @param $receivers
 914          * @param $actor
 915          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 916          * @throws \ImagickException
 917          */
 918         private static function switchContacts($receivers, $actor)
 919         {
 920                 if (empty($actor)) {
 921                         return;
 922                 }
 923
 924                 foreach ($receivers as $receiver) {
 925                         $contact = DBA::selectFirst('contact', ['id'], ['uid' => $receiver['uid'], 'network' => Protocol::OSTATUS, 'nurl' => Strings::normaliseLink($actor)]);
 926                         if (DBA::isResult($contact)) {
 927                                 self::switchContact($contact['id'], $receiver['uid'], $actor);
 928                         }
 929
 930                         $contact = DBA::selectFirst('contact', ['id'], ['uid' => $receiver['uid'], 'network' => Protocol::OSTATUS, 'alias' => [Strings::normaliseLink($actor), $actor]]);
 931                         if (DBA::isResult($contact)) {
 932                                 self::switchContact($contact['id'], $receiver['uid'], $actor);
 933                         }
 934                 }
 935         }
 936
 937         /**
 938          *
 939          *
 940          * @param       $object_data
 941          * @param array $activity
 942          *
 943          * @return mixed
 944          */
 945         private static function addActivityFields($object_data, $activity)
 946         {
 947                 if (!empty($activity['published']) && empty($object_data['published'])) {
 948                         $object_data['published'] = JsonLD::fetchElement($activity, 'as:published', '@value');
 949                 }
 950
 951                 if (!empty($activity['diaspora:guid']) && empty($object_data['diaspora:guid'])) {
 952                         $object_data['diaspora:guid'] = JsonLD::fetchElement($activity, 'diaspora:guid', '@value');
 953                 }
 954
 955                 $object_data['service'] = JsonLD::fetchElement($activity, 'as:instrument', 'as:name', '@type', 'as:Service');
 956                 $object_data['service'] = JsonLD::fetchElement($object_data, 'service', '@value');
 957
 958                 if (!empty($object_data['object_id'])) {
 959                         // Some systems (e.g. GNU Social) don't reply to the "id" field but the "uri" field.
 960                         $objectId = Item::getURIByLink($object_data['object_id']);
 961                         if (!empty($objectId) && ($object_data['object_id'] != $objectId)) {
 962                                 Logger::notice('Fix wrong object-id', ['received' => $object_data['object_id'], 'correct' => $objectId]);
 963                                 $object_data['object_id'] = $objectId;
 964                         }
 965                 }
 966
 967                 return $object_data;
 968         }
 969
 970         /**
 971          * Fetches the object data from external ressources if needed
 972          *
 973          * @param string  $object_id    Object ID of the the provided object
 974          * @param array   $object       The provided object array
 975          * @param boolean $trust_source Do we trust the provided object?
 976          * @param integer $uid          User ID for the signature that we use to fetch data
 977          *
 978          * @return array|false with trusted and valid object data
 979          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 980          * @throws \ImagickException
 981          */
 982         private static function fetchObject(string $object_id, array $object = [], bool $trust_source = false, int $uid = 0)
 983         {
 984                 // By fetching the type we check if the object is complete.
 985                 $type = JsonLD::fetchElement($object, '@type');
 986
 987                 if (!$trust_source || empty($type)) {
 988                         $data = ActivityPub::fetchContent($object_id, $uid);
 989                         if (!empty($data)) {
 990                                 $object = JsonLD::compact($data);
 991                                 Logger::info('Fetched content for ' . $object_id);
 992                         } else {
 993                                 Logger::info('Empty content for ' . $object_id . ', check if content is available locally.');
 994
 995                                 $item = Post::selectFirst(Item::DELIVER_FIELDLIST, ['uri' => $object_id]);
 996                                 if (!DBA::isResult($item)) {
 997                                         Logger::info('Object with url ' . $object_id . ' was not found locally.');
 998                                         return false;
 999                                 }
1000                                 Logger::info('Using already stored item for url ' . $object_id);
1001                                 $data = ActivityPub\Transmitter::createNote($item);
1002                                 $object = JsonLD::compact($data);
1003                         }
1004
1005                         $id = JsonLD::fetchElement($object, '@id');
1006                         if (empty($id)) {
1007                                 Logger::info('Empty id');
1008                                 return false;
1009                         }
1010
1011                         if ($id != $object_id) {
1012                                 Logger::info('Fetched id differs from provided id', ['provided' => $object_id, 'fetched' => $id]);
1013                                 return false;
1014                         }
1015                 } else {
1016                         Logger::info('Using original object for url ' . $object_id);
1017                 }
1018
1019                 $type = JsonLD::fetchElement($object, '@type');
1020                 if (empty($type)) {
1021                         Logger::info('Empty type');
1022                         return false;
1023                 }
1024
1025                 // Lemmy is resharing "create" activities instead of content
1026                 // We fetch the content from the activity.
1027                 if (in_array($type, ['as:Create'])) {
1028                         $object = $object['as:object'];
1029                         $type = JsonLD::fetchElement($object, '@type');
1030                         if (empty($type)) {
1031                                 Logger::info('Empty type');
1032                                 return false;
1033                         }
1034                         $object_data = self::processObject($object);
1035                 }
1036
1037                 // We currently don't handle 'pt:CacheFile', but with this step we avoid logging
1038                 if (in_array($type, self::CONTENT_TYPES) || ($type == 'pt:CacheFile')) {
1039                         $object_data = self::processObject($object);
1040
1041                         if (!empty($data)) {
1042                                 $object_data['raw'] = json_encode($data);
1043                         }
1044                         return $object_data;
1045                 }
1046
1047                 if ($type == 'as:Announce') {
1048                         $object_id = JsonLD::fetchElement($object, 'object', '@id');
1049                         if (empty($object_id) || !is_string($object_id)) {
1050                                 return false;
1051                         }
1052                         return self::fetchObject($object_id, [], false, $uid);
1053                 }
1054
1055                 Logger::info('Unhandled object type: ' . $type);
1056                 return false;
1057         }
1058
1059         /**
1060          * Converts the language element (Used by Peertube)
1061          *
1062          * @param array $languages
1063          * @return array Languages
1064          */
1065         public static function processLanguages(array $languages)
1066         {
1067                 if (empty($languages)) {
1068                         return [];
1069                 }
1070
1071                 $language_list = [];
1072
1073                 foreach ($languages as $language) {
1074                         if (!empty($language['_:identifier']) && !empty($language['as:name'])) {
1075                                 $language_list[$language['_:identifier']] = $language['as:name'];
1076                         }
1077                 }
1078                 return $language_list;
1079         }
1080
1081         /**
1082          * Convert tags from JSON-LD format into a simplified format
1083          *
1084          * @param array $tags Tags in JSON-LD format
1085          *
1086          * @return array with tags in a simplified format
1087          */
1088         public static function processTags(array $tags)
1089         {
1090                 $taglist = [];
1091
1092                 foreach ($tags as $tag) {
1093                         if (empty($tag)) {
1094                                 continue;
1095                         }
1096
1097                         $element = ['type' => str_replace('as:', '', JsonLD::fetchElement($tag, '@type')),
1098                                 'href' => JsonLD::fetchElement($tag, 'as:href', '@id'),
1099                                 'name' => JsonLD::fetchElement($tag, 'as:name', '@value')];
1100
1101                         if (empty($element['type'])) {
1102                                 continue;
1103                         }
1104
1105                         if (empty($element['href'])) {
1106                                 $element['href'] = $element['name'];
1107                         }
1108
1109                         $taglist[] = $element;
1110                 }
1111                 return $taglist;
1112         }
1113
1114         /**
1115          * Convert emojis from JSON-LD format into a simplified format
1116          *
1117          * @param array $emojis
1118          * @return array with emojis in a simplified format
1119          */
1120         private static function processEmojis(array $emojis)
1121         {
1122                 $emojilist = [];
1123
1124                 foreach ($emojis as $emoji) {
1125                         if (empty($emoji) || (JsonLD::fetchElement($emoji, '@type') != 'toot:Emoji') || empty($emoji['as:icon'])) {
1126                                 continue;
1127                         }
1128
1129                         $url = JsonLD::fetchElement($emoji['as:icon'], 'as:url', '@id');
1130                         $element = ['name' => JsonLD::fetchElement($emoji, 'as:name', '@value'),
1131                                 'href' => $url];
1132
1133                         $emojilist[] = $element;
1134                 }
1135
1136                 return $emojilist;
1137         }
1138
1139         /**
1140          * Convert attachments from JSON-LD format into a simplified format
1141          *
1142          * @param array $attachments Attachments in JSON-LD format
1143          *
1144          * @return array Attachments in a simplified format
1145          */
1146         private static function processAttachments(array $attachments)
1147         {
1148                 $attachlist = [];
1149
1150                 // Removes empty values
1151                 $attachments = array_filter($attachments);
1152
1153                 foreach ($attachments as $attachment) {
1154                         switch (JsonLD::fetchElement($attachment, '@type')) {
1155                                 case 'as:Page':
1156                                         $pageUrl = null;
1157                                         $pageImage = null;
1158
1159                                         $urls = JsonLD::fetchElementArray($attachment, 'as:url');
1160                                         foreach ($urls as $url) {
1161                                                 // Single scalar URL case
1162                                                 if (is_string($url)) {
1163                                                         $pageUrl = $url;
1164                                                         continue;
1165                                                 }
1166
1167                                                 $href = JsonLD::fetchElement($url, 'as:href', '@id');
1168                                                 $mediaType = JsonLD::fetchElement($url, 'as:mediaType', '@value');
1169                                                 if (Strings::startsWith($mediaType, 'image')) {
1170                                                         $pageImage = $href;
1171                                                 } else {
1172                                                         $pageUrl = $href;
1173                                                 }
1174                                         }
1175
1176                                         $attachlist[] = [
1177                                                 'type'  => 'link',
1178                                                 'title' => JsonLD::fetchElement($attachment, 'as:name', '@value'),
1179                                                 'desc'  => JsonLD::fetchElement($attachment, 'as:summary', '@value'),
1180                                                 'url'   => $pageUrl,
1181                                                 'image' => $pageImage,
1182                                         ];
1183                                         break;
1184                                 case 'as:Image':
1185                                         $mediaType = JsonLD::fetchElement($attachment, 'as:mediaType', '@value');
1186                                         $imageFullUrl = JsonLD::fetchElement($attachment, 'as:url', '@id');
1187                                         $imagePreviewUrl = null;
1188                                         // Multiple URLs?
1189                                         if (!$imageFullUrl && ($urls = JsonLD::fetchElementArray($attachment, 'as:url'))) {
1190                                                 $imageVariants = [];
1191                                                 $previewVariants = [];
1192                                                 foreach ($urls as $url) {
1193                                                         // Scalar URL, no discrimination possible
1194                                                         if (is_string($url)) {
1195                                                                 $imageFullUrl = $url;
1196                                                                 continue;
1197                                                         }
1198
1199                                                         // Not sure what to do with a different Link media type than the base Image, we skip
1200                                                         if ($mediaType != JsonLD::fetchElement($url, 'as:mediaType', '@value')) {
1201                                                                 continue;
1202                                                         }
1203
1204                                                         $href = JsonLD::fetchElement($url, 'as:href', '@id');
1205
1206                                                         // Default URL choice if no discriminating width is provided
1207                                                         $imageFullUrl = $href ?? $imageFullUrl;
1208
1209                                                         $width = intval(JsonLD::fetchElement($url, 'as:width', '@value') ?? 1);
1210
1211                                                         if ($href && $width) {
1212                                                                 $imageVariants[$width] = $href;
1213                                                                 // 632 is the ideal width for full screen frio posts, we compute the absolute distance to it
1214                                                                 $previewVariants[abs(632 - $width)] = $href;
1215                                                         }
1216                                                 }
1217
1218                                                 if ($imageVariants) {
1219                                                         // Taking the maximum size image
1220                                                         ksort($imageVariants);
1221                                                         $imageFullUrl = array_pop($imageVariants);
1222
1223                                                         // Taking the minimum number distance to the target distance
1224                                                         ksort($previewVariants);
1225                                                         $imagePreviewUrl = array_shift($previewVariants);
1226                                                 }
1227
1228                                                 unset($imageVariants);
1229                                                 unset($previewVariants);
1230                                         }
1231
1232                                         $attachlist[] = [
1233                                                 'type' => str_replace('as:', '', JsonLD::fetchElement($attachment, '@type')),
1234                                                 'mediaType' => $mediaType,
1235                                                 'name'  => JsonLD::fetchElement($attachment, 'as:name', '@value'),
1236                                                 'url'   => $imageFullUrl,
1237                                                 'image' => $imagePreviewUrl !== $imageFullUrl ? $imagePreviewUrl : null,
1238                                         ];
1239                                         break;
1240                                 default:
1241                                         $attachlist[] = [
1242                                                 'type' => str_replace('as:', '', JsonLD::fetchElement($attachment, '@type')),
1243                                                 'mediaType' => JsonLD::fetchElement($attachment, 'as:mediaType', '@value'),
1244                                                 'name' => JsonLD::fetchElement($attachment, 'as:name', '@value'),
1245                                                 'url' => JsonLD::fetchElement($attachment, 'as:url', '@id'),
1246                                                 'height' => JsonLD::fetchElement($attachment, 'as:height', '@value'),
1247                                                 'width' => JsonLD::fetchElement($attachment, 'as:width', '@value'),
1248                                                 'image' => JsonLD::fetchElement($attachment, 'as:image', '@id')
1249                                         ];
1250                         }
1251                 }
1252
1253                 return $attachlist;
1254         }
1255
1256         /**
1257          * Fetch the original source or content with the "language" Markdown or HTML
1258          *
1259          * @param array $object
1260          * @param array $object_data
1261          *
1262          * @return array
1263          * @throws \Exception
1264          */
1265         private static function getSource($object, $object_data)
1266         {
1267                 $object_data['source'] = JsonLD::fetchElement($object, 'as:source', 'as:content', 'as:mediaType', 'text/bbcode');
1268                 $object_data['source'] = JsonLD::fetchElement($object_data, 'source', '@value');
1269                 if (!empty($object_data['source'])) {
1270                         return $object_data;
1271                 }
1272
1273                 $object_data['source'] = JsonLD::fetchElement($object, 'as:source', 'as:content', 'as:mediaType', 'text/markdown');
1274                 $object_data['source'] = JsonLD::fetchElement($object_data, 'source', '@value');
1275                 if (!empty($object_data['source'])) {
1276                         $object_data['source'] = Markdown::toBBCode($object_data['source']);
1277                         return $object_data;
1278                 }
1279
1280                 $object_data['source'] = JsonLD::fetchElement($object, 'as:source', 'as:content', 'as:mediaType', 'text/html');
1281                 $object_data['source'] = JsonLD::fetchElement($object_data, 'source', '@value');
1282                 if (!empty($object_data['source'])) {
1283                         $object_data['source'] = HTML::toBBCode($object_data['source']);
1284                         return $object_data;
1285                 }
1286
1287                 return $object_data;
1288         }
1289
1290         /**
1291          * Extracts a potential alternate URL from a list of additional URL elements
1292          *
1293          * @param array $urls
1294          * @return string
1295          */
1296         private static function extractAlternateUrl(array $urls): string
1297         {
1298                 $alternateUrl = '';
1299                 foreach ($urls as $key => $url) {
1300                         // Not a list but a single URL element
1301                         if (!is_numeric($key)) {
1302                                 continue;
1303                         }
1304
1305                         if (empty($url['@type']) || ($url['@type'] != 'as:Link')) {
1306                                 continue;
1307                         }
1308
1309                         $href = JsonLD::fetchElement($url, 'as:href', '@id');
1310                         if (empty($href)) {
1311                                 continue;
1312                         }
1313
1314                         $mediatype = JsonLD::fetchElement($url, 'as:mediaType');
1315                         if (empty($mediatype)) {
1316                                 continue;
1317                         }
1318
1319                         if ($mediatype == 'text/html') {
1320                                 $alternateUrl = $href;
1321                         }
1322                 }
1323
1324                 return $alternateUrl;
1325         }
1326
1327         /**
1328          * Check if the "as:url" element is an array with multiple links
1329          * This is the case with audio and video posts.
1330          * Then the links are added as attachments
1331          *
1332          * @param array $urls The object URL list
1333          * @return array an array of attachments
1334          */
1335         private static function processAttachmentUrls(array $urls): array
1336         {
1337                 $attachments = [];
1338                 foreach ($urls as $key => $url) {
1339                         // Not a list but a single URL element
1340                         if (!is_numeric($key)) {
1341                                 continue;
1342                         }
1343
1344                         if (empty($url['@type']) || ($url['@type'] != 'as:Link')) {
1345                                 continue;
1346                         }
1347
1348                         $href = JsonLD::fetchElement($url, 'as:href', '@id');
1349                         if (empty($href)) {
1350                                 continue;
1351                         }
1352
1353                         $mediatype = JsonLD::fetchElement($url, 'as:mediaType');
1354                         if (empty($mediatype)) {
1355                                 continue;
1356                         }
1357
1358                         $filetype = strtolower(substr($mediatype, 0, strpos($mediatype, '/')));
1359
1360                         if ($filetype == 'audio') {
1361                                 $attachments[] = ['type' => $filetype, 'mediaType' => $mediatype, 'url' => $href, 'height' => null, 'size' => null, 'name' => ''];
1362                         } elseif ($filetype == 'video') {
1363                                 $height = (int)JsonLD::fetchElement($url, 'as:height', '@value');
1364                                 // PeerTube audio-only track
1365                                 if ($height === 0) {
1366                                         continue;
1367                                 }
1368
1369                                 $size = (int)JsonLD::fetchElement($url, 'pt:size', '@value');
1370                                 $attachments[] = ['type' => $filetype, 'mediaType' => $mediatype, 'url' => $href, 'height' => $height, 'size' => $size, 'name' => ''];
1371                         } elseif (in_array($mediatype, ['application/x-bittorrent', 'application/x-bittorrent;x-scheme-handler/magnet'])) {
1372                                 $height = (int)JsonLD::fetchElement($url, 'as:height', '@value');
1373
1374                                 // For Torrent links we always store the highest resolution
1375                                 if (!empty($attachments[$mediatype]['height']) && ($height < $attachments[$mediatype]['height'])) {
1376                                         continue;
1377                                 }
1378
1379                                 $attachments[$mediatype] = ['type' => $mediatype, 'mediaType' => $mediatype, 'url' => $href, 'height' => $height, 'size' => null, 'name' => ''];
1380                         } elseif ($mediatype == 'application/x-mpegURL') {
1381                                 // PeerTube exception, actual video link is in the tags of this URL element
1382                                 $attachments = array_merge($attachments, self::processAttachmentUrls($url['as:tag']));
1383                         }
1384                 }
1385
1386                 return array_values($attachments);
1387         }
1388
1389         /**
1390          * Fetches data from the object part of an activity
1391          *
1392          * @param array $object
1393          *
1394          * @return array
1395          * @throws \Exception
1396          */
1397         private static function processObject($object)
1398         {
1399                 if (!JsonLD::fetchElement($object, '@id')) {
1400                         return false;
1401                 }
1402
1403                 $object_data = [];
1404                 $object_data['object_type'] = JsonLD::fetchElement($object, '@type');
1405                 $object_data['id'] = JsonLD::fetchElement($object, '@id');
1406                 $object_data['reply-to-id'] = JsonLD::fetchElement($object, 'as:inReplyTo', '@id');
1407
1408                 // An empty "id" field is translated to "./" by the compactor, so we have to check for this content
1409                 if (empty($object_data['reply-to-id']) || ($object_data['reply-to-id'] == './')) {
1410                         $object_data['reply-to-id'] = $object_data['id'];
1411
1412                         // On activities the "reply to" is the id of the object it refers to
1413                         if (in_array($object_data['object_type'], self::ACTIVITY_TYPES)) {
1414                                 $object_id = JsonLD::fetchElement($object, 'as:object', '@id');
1415                                 if (!empty($object_id)) {
1416                                         $object_data['reply-to-id'] = $object_id;
1417                                 }
1418                         }
1419                 } else {
1420                         // Some systems (e.g. GNU Social) don't reply to the "id" field but the "uri" field.
1421                         $replyToId = Item::getURIByLink($object_data['reply-to-id']);
1422                         if (!empty($replyToId) && ($object_data['reply-to-id'] != $replyToId)) {
1423                                 Logger::notice('Fix wrong reply-to', ['received' => $object_data['reply-to-id'], 'correct' => $replyToId]);
1424                                 $object_data['reply-to-id'] = $replyToId;
1425                         }
1426                 }
1427
1428                 $object_data['published'] = JsonLD::fetchElement($object, 'as:published', '@value');
1429                 $object_data['updated'] = JsonLD::fetchElement($object, 'as:updated', '@value');
1430
1431                 if (empty($object_data['updated'])) {
1432                         $object_data['updated'] = $object_data['published'];
1433                 }
1434
1435                 if (empty($object_data['published']) && !empty($object_data['updated'])) {
1436                         $object_data['published'] = $object_data['updated'];
1437                 }
1438
1439                 $actor = JsonLD::fetchElement($object, 'as:attributedTo', '@id');
1440                 if (empty($actor)) {
1441                         $actor = JsonLD::fetchElement($object, 'as:actor', '@id');
1442                 }
1443
1444                 $location = JsonLD::fetchElement($object, 'as:location', 'as:name', '@type', 'as:Place');
1445                 $location = JsonLD::fetchElement($location, 'location', '@value');
1446                 if ($location) {
1447                         // Some AP software allow formatted text in post location, so we run all the text converters we have to boil
1448                         // down to HTML and then finally format to plaintext.
1449                         $location = Markdown::convert($location);
1450                         $location = BBCode::toPlaintext($location);
1451                 }
1452
1453                 $object_data['sc:identifier'] = JsonLD::fetchElement($object, 'sc:identifier', '@value');
1454                 $object_data['diaspora:guid'] = JsonLD::fetchElement($object, 'diaspora:guid', '@value');
1455                 $object_data['diaspora:comment'] = JsonLD::fetchElement($object, 'diaspora:comment', '@value');
1456                 $object_data['diaspora:like'] = JsonLD::fetchElement($object, 'diaspora:like', '@value');
1457                 $object_data['actor'] = $object_data['author'] = $actor;
1458                 $object_data['context'] = JsonLD::fetchElement($object, 'as:context', '@id');
1459                 $object_data['conversation'] = JsonLD::fetchElement($object, 'ostatus:conversation', '@id');
1460                 $object_data['sensitive'] = JsonLD::fetchElement($object, 'as:sensitive');
1461                 $object_data['name'] = JsonLD::fetchElement($object, 'as:name', '@value');
1462                 $object_data['summary'] = JsonLD::fetchElement($object, 'as:summary', '@value');
1463                 $object_data['content'] = JsonLD::fetchElement($object, 'as:content', '@value');
1464                 $object_data['mediatype'] = JsonLD::fetchElement($object, 'as:mediaType', '@value');
1465                 $object_data = self::getSource($object, $object_data);
1466                 $object_data['start-time'] = JsonLD::fetchElement($object, 'as:startTime', '@value');
1467                 $object_data['end-time'] = JsonLD::fetchElement($object, 'as:endTime', '@value');
1468                 $object_data['location'] = $location;
1469                 $object_data['latitude'] = JsonLD::fetchElement($object, 'as:location', 'as:latitude', '@type', 'as:Place');
1470                 $object_data['latitude'] = JsonLD::fetchElement($object_data, 'latitude', '@value');
1471                 $object_data['longitude'] = JsonLD::fetchElement($object, 'as:location', 'as:longitude', '@type', 'as:Place');
1472                 $object_data['longitude'] = JsonLD::fetchElement($object_data, 'longitude', '@value');
1473                 $object_data['attachments'] = self::processAttachments(JsonLD::fetchElementArray($object, 'as:attachment') ?? []);
1474                 $object_data['tags'] = self::processTags(JsonLD::fetchElementArray($object, 'as:tag') ?? []);
1475                 $object_data['emojis'] = self::processEmojis(JsonLD::fetchElementArray($object, 'as:tag', null, '@type', 'toot:Emoji') ?? []);
1476                 $object_data['languages'] = self::processLanguages(JsonLD::fetchElementArray($object, 'sc:inLanguage') ?? []);
1477                 $object_data['generator'] = JsonLD::fetchElement($object, 'as:generator', 'as:name', '@type', 'as:Application');
1478                 $object_data['generator'] = JsonLD::fetchElement($object_data, 'generator', '@value');
1479                 $object_data['alternate-url'] = JsonLD::fetchElement($object, 'as:url', '@id');
1480
1481                 // Special treatment for Hubzilla links
1482                 if (is_array($object_data['alternate-url'])) {
1483                         $object_data['alternate-url'] = JsonLD::fetchElement($object_data['alternate-url'], 'as:href', '@id');
1484
1485                         if (!is_string($object_data['alternate-url'])) {
1486                                 $object_data['alternate-url'] = JsonLD::fetchElement($object['as:url'], 'as:href', '@id');
1487                         }
1488                 }
1489
1490                 if (in_array($object_data['object_type'], ['as:Audio', 'as:Video'])) {
1491                         $object_data['alternate-url'] = self::extractAlternateUrl($object['as:url'] ?? []) ?: $object_data['alternate-url'];
1492                         $object_data['attachments'] = array_merge($object_data['attachments'], self::processAttachmentUrls($object['as:url'] ?? []));
1493                 }
1494
1495                 // For page types we expect that the alternate url posts to some page.
1496                 // So we add this to the attachments if it differs from the id.
1497                 // Currently only Lemmy is using the page type.
1498                 if (($object_data['object_type'] == 'as:Page') && !empty($object_data['alternate-url']) && !Strings::compareLink($object_data['alternate-url'], $object_data['id'])) {
1499                         $object_data['attachments'][] = ['url' => $object_data['alternate-url']];
1500                         $object_data['alternate-url'] = null;
1501                 }
1502
1503                 $receiverdata = self::getReceivers($object, $object_data['actor'], $object_data['tags'], true);
1504                 $receivers = $reception_types = [];
1505                 foreach ($receiverdata as $key => $data) {
1506                         $receivers[$key] = $data['uid'];
1507                         $reception_types[$data['uid']] = $data['type'] ?? 0;
1508                 }
1509
1510                 $object_data['receiver'] = $receivers;
1511                 $object_data['reception_type'] = $reception_types;
1512
1513                 $object_data['unlisted'] = in_array(-1, $object_data['receiver']);
1514                 unset($object_data['receiver'][-1]);
1515                 unset($object_data['reception_type'][-1]);
1516
1517                 // Common object data:
1518
1519                 // Unhandled
1520                 // @context, type, actor, signature, mediaType, duration, replies, icon
1521
1522                 // Also missing: (Defined in the standard, but currently unused)
1523                 // audience, preview, endTime, startTime, image
1524
1525                 // Data in Notes:
1526
1527                 // Unhandled
1528                 // contentMap, announcement_count, announcements, context_id, likes, like_count
1529                 // inReplyToStatusId, shares, quoteUrl, statusnetConversationId
1530
1531                 // Data in video:
1532
1533                 // To-Do?
1534                 // category, licence, language, commentsEnabled
1535
1536                 // Unhandled
1537                 // views, waitTranscoding, state, support, subtitleLanguage
1538                 // likes, dislikes, shares, comments
1539
1540                 return $object_data;
1541         }
1542 }