]> git.mxchange.org Git - friendica.git/blobdiff - src/Protocol/ActivityPub.php
Improve communication
[friendica.git] / src / Protocol / ActivityPub.php
index df6b0342be0aa871ff53f22548d91e306f346f3f..95542ba966200b9fb14aa261f11013814e0468cc 100644 (file)
@@ -13,12 +13,14 @@ use Friendica\Core\Protocol;
 use Friendica\Model\Conversation;
 use Friendica\Model\Contact;
 use Friendica\Model\Item;
+use Friendica\Model\Term;
 use Friendica\Model\User;
 use Friendica\Util\DateTimeFormat;
 use Friendica\Util\Crypto;
 use Friendica\Content\Text\BBCode;
 use Friendica\Content\Text\HTML;
-use Friendica\Network\Probe;
+use Friendica\Util\JsonLD;
+use Friendica\Util\LDSignature;
 
 /**
  * @brief ActivityPub Protocol class
@@ -32,9 +34,10 @@ use Friendica\Network\Probe;
  *
  * Digest: https://tools.ietf.org/html/rfc5843
  * https://tools.ietf.org/html/draft-cavage-http-signatures-10#ref-15
+ * https://github.com/digitalbazaar/php-json-ld
  *
  * Part of the code for HTTP signing is taken from the Osada project.
- * 
+ * https://framagit.org/macgirvin/osada
  *
  * To-do:
  *
@@ -43,44 +46,22 @@ use Friendica\Network\Probe;
  * - Object Types: Person, Tombstome
  *
  * Transmitter:
- * - Activities: Like, Dislike, Update, Delete
- * - Object Tyoes: Article, Announce, Person, Tombstone
+ * - Activities: Like, Dislike, Update, Delete, Announce
+ * - Object Tyoes: Article, Person, Tombstone
  *
  * General:
- * - Message distribution
- * - Endpoints: Outbox, Object, Follower, Following
+ * - Endpoints: Outbox, Follower, Following
+ * - General cleanup
+ * - Queueing unsucessful deliveries
  */
 class ActivityPub
 {
        const PUBLIC = 'https://www.w3.org/ns/activitystreams#Public';
 
-       public static function transmit($data, $target, $uid)
+       public static function isRequest()
        {
-               $owner = User::getOwnerDataById($uid);
-
-               if (!$owner) {
-                       return;
-               }
-
-               $content = json_encode($data);
-
-               $host = parse_url($target, PHP_URL_HOST);
-               $path = parse_url($target, PHP_URL_PATH);
-               $date = date('r');
-
-               $headers = ['Host: ' . $host, 'Date: ' . $date];
-
-               $signed_data = "(request-target): post " . $path . "\nhost: " . $host . "\ndate: " . $date;
-
-               $signature = base64_encode(Crypto::rsaSign($signed_data, $owner['uprvkey'], 'sha256'));
-
-               $headers[] = 'Signature: keyId="' . $owner['url'] . '#main-key' . '",headers="(request-target) host date",signature="' . $signature . '"';
-               $headers[] = 'Content-Type: application/activity+json';
-
-               Network::post($target, $content, $headers);
-               $return_code = BaseObject::getApp()->get_curl_code();
-
-               logger('Transmit to ' . $target . ' returned ' . $return_code);
+               return stristr(defaults($_SERVER, 'HTTP_ACCEPT', ''), 'application/activity+json') ||
+                       stristr(defaults($_SERVER, 'HTTP_ACCEPT', ''), 'application/ld+json');
        }
 
        /**
@@ -92,10 +73,9 @@ class ActivityPub
        public static function profile($uid)
        {
                $accounttype = ['Person', 'Organization', 'Service', 'Group', 'Application'];
-
                $condition = ['uid' => $uid, 'blocked' => false, 'account_expired' => false,
                        'account_removed' => false, 'verified' => true];
-               $fields = ['guid', 'nickname', 'pubkey', 'account-type'];
+               $fields = ['guid', 'nickname', 'pubkey', 'account-type', 'page-flags'];
                $user = DBA::selectFirst('user', $fields, $condition);
                if (!DBA::isResult($user)) {
                        return [];
@@ -114,8 +94,8 @@ class ActivityPub
                }
 
                $data = ['@context' => ['https://www.w3.org/ns/activitystreams', 'https://w3id.org/security/v1',
-                       ['uuid' => 'http://schema.org/identifier', 'sensitive' => 'as:sensitive',
-                       'vcard' => 'http://www.w3.org/2006/vcard/ns#']]];
+                       ['vcard' => 'http://www.w3.org/2006/vcard/ns#', 'uuid' => 'http://schema.org/identifier',
+                       'sensitive' => 'as:sensitive', 'manuallyApprovesFollowers' => 'as:manuallyApprovesFollowers']]];
 
                $data['id'] = $contact['url'];
                $data['uuid'] = $user['guid'];
@@ -126,11 +106,11 @@ class ActivityPub
                $data['outbox'] = System::baseUrl() . '/outbox/' . $user['nickname'];
                $data['preferredUsername'] = $user['nickname'];
                $data['name'] = $contact['name'];
-               $data['vcard:hasAddress'] = ['@type' => 'Home', 'vcard:country-name' => $profile['country-name'],
+               $data['vcard:hasAddress'] = ['@type' => 'vcard:Home', 'vcard:country-name' => $profile['country-name'],
                        'vcard:region' => $profile['region'], 'vcard:locality' => $profile['locality']];
                $data['summary'] = $contact['about'];
                $data['url'] = $contact['url'];
-               $data['manuallyApprovesFollowers'] = false;
+               $data['manuallyApprovesFollowers'] = in_array($user['page-flags'], [Contact::PAGE_NORMAL, Contact::PAGE_PRVGROUP]);
                $data['publicKey'] = ['id' => $contact['url'] . '#main-key',
                        'owner' => $contact['url'],
                        'publicKeyPem' => $user['pubkey']];
@@ -142,64 +122,316 @@ class ActivityPub
                return $data;
        }
 
+       private static function fetchPermissionBlockFromConversation($item)
+       {
+               if (empty($item['thr-parent'])) {
+                       return [];
+               }
+
+               $condition = ['item-uri' => $item['thr-parent'], 'protocol' => Conversation::PARCEL_ACTIVITYPUB];
+               $conversation = DBA::selectFirst('conversation', ['source'], $condition);
+               if (!DBA::isResult($conversation)) {
+                       return [];
+               }
+
+               $activity = json_decode($conversation['source'], true);
+
+               $actor = JsonLD::fetchElement($activity, 'actor', 'id');
+               $profile = ActivityPub::fetchprofile($actor);
+
+               $item_profile = ActivityPub::fetchprofile($item['owner-link']);
+
+               $permissions = [];
+
+               $elements = ['to', 'cc', 'bto', 'bcc'];
+               foreach ($elements as $element) {
+                       if (empty($activity[$element])) {
+                               continue;
+                       }
+                       if (is_string($activity[$element])) {
+                               $activity[$element] = [$activity[$element]];
+                       }
+                       foreach ($activity[$element] as $receiver) {
+                               if ($receiver == $profile['followers'] && !empty($item_profile['followers'])) {
+                                       $receiver = $item_profile['followers'];
+                               }
+                               if ($receiver != $item['owner-link']) {
+                                       $permissions[$element][] = $receiver;
+                               }
+                       }
+               }
+               return $permissions;
+       }
+
+       public static function createPermissionBlockForItem($item)
+       {
+               $data = ['to' => [], 'cc' => []];
+
+               $data = array_merge($data, self::fetchPermissionBlockFromConversation($item));
+
+               $actor_profile = ActivityPub::fetchprofile($item['author-link']);
+
+               $terms = Term::tagArrayFromItemId($item['id']);
+
+               $contacts[$item['author-link']] = $item['author-link'];
+
+               if (!$item['private']) {
+                       $data['to'][] = self::PUBLIC;
+                       if (!empty($actor_profile['followers'])) {
+                               $data['cc'][] = $actor_profile['followers'];
+                       }
+
+                       foreach ($terms as $term) {
+                               if ($term['type'] != TERM_MENTION) {
+                                       continue;
+                               }
+                               $profile = self::fetchprofile($term['url']);
+                               if (!empty($profile) && empty($contacts[$profile['url']])) {
+                                       $data['cc'][] = $profile['url'];
+                                       $contacts[$profile['url']] = $profile['url'];
+                               }
+                       }
+               } else {
+                       $receiver_list = Item::enumeratePermissions($item);
+
+                       $mentioned = [];
+
+                       foreach ($terms as $term) {
+                               if ($term['type'] != TERM_MENTION) {
+                                       continue;
+                               }
+                               $cid = Contact::getIdForURL($term['url'], $item['uid']);
+                               if (!empty($cid) && in_array($cid, $receiver_list)) {
+                                       $contact = DBA::selectFirst('contact', ['url'], ['id' => $cid, 'network' => Protocol::ACTIVITYPUB]);
+                                       $data['to'][] = $contact['url'];
+                                       $contacts[$contact['url']] = $contact['url'];
+                               }
+                       }
+
+                       foreach ($receiver_list as $receiver) {
+                               $contact = DBA::selectFirst('contact', ['url'], ['id' => $receiver, 'network' => Protocol::ACTIVITYPUB]);
+                               if (empty($contacts[$contact['url']])) {
+                                       $data['cc'][] = $contact['url'];
+                                       $contacts[$contact['url']] = $contact['url'];
+                               }
+                       }
+               }
+
+               $parents = Item::select(['author-link', 'owner-link'], ['parent' => $item['parent']]);
+               while ($parent = Item::fetch($parents)) {
+                       $profile = self::fetchprofile($parent['author-link']);
+                       if (!empty($profile) && empty($contacts[$profile['url']])) {
+                               $data['cc'][] = $profile['url'];
+                               $contacts[$profile['url']] = $profile['url'];
+                       }
+
+                       $profile = self::fetchprofile($parent['owner-link']);
+                       if (!empty($profile) && empty($contacts[$profile['url']])) {
+                               $data['cc'][] = $profile['url'];
+                               $contacts[$profile['url']] = $profile['url'];
+                       }
+               }
+               DBA::close($parents);
+
+               if (empty($data['to'])) {
+                       $data['to'] = $data['cc'];
+                       $data['cc'] = [];
+               }
+
+               return $data;
+       }
+
+       public static function fetchTargetInboxes($item, $uid)
+       {
+               $permissions = self::createPermissionBlockForItem($item);
+               if (empty($permissions)) {
+                       return [];
+               }
+
+               $inboxes = [];
+
+               $item_profile = ActivityPub::fetchprofile($item['owner-link']);
+
+               $elements = ['to', 'cc', 'bto', 'bcc'];
+               foreach ($elements as $element) {
+                       if (empty($permissions[$element])) {
+                               continue;
+                       }
+                       foreach ($permissions[$element] as $receiver) {
+                               if ($receiver == $item_profile['followers']) {
+                                       $contacts = DBA::select('contact', ['notify', 'batch'], ['uid' => $uid,
+                                               'rel' => [Contact::FOLLOWER, Contact::FRIEND], 'network' => Protocol::ACTIVITYPUB]);
+                                       while ($contact = DBA::fetch($contacts)) {
+                                               $contact = defaults($contact, 'batch', $contact['notify']);
+                                               $inboxes[$contact] = $contact;
+                                       }
+                                       DBA::close($contacts);
+                               } else {
+                                       $profile = self::fetchprofile($receiver);
+                                       if (!empty($profile)) {
+                                               $target = defaults($profile, 'sharedinbox', $profile['inbox']);
+                                               $inboxes[$target] = $target;
+                                       }
+                               }
+                       }
+               }
+
+               if (!empty($item_profile['sharedinbox'])) {
+                       unset($inboxes[$item_profile['sharedinbox']]);
+               }
+
+               if (!empty($item_profile['inbox'])) {
+                       unset($inboxes[$item_profile['inbox']]);
+               }
+
+               return $inboxes;
+       }
+
        public static function createActivityFromItem($item_id)
        {
                $item = Item::selectFirst([], ['id' => $item_id]);
 
+               if (!DBA::isResult($item)) {
+                       return false;
+               }
+
+               $condition = ['item-uri' => $item['uri'], 'protocol' => Conversation::PARCEL_ACTIVITYPUB];
+               $conversation = DBA::selectFirst('conversation', ['source'], $condition);
+               if (DBA::isResult($conversation)) {
+                       $data = json_decode($conversation['source']);
+                       if (!empty($data)) {
+                               return $data;
+                       }
+               }
+
                $data = ['@context' => ['https://www.w3.org/ns/activitystreams', 'https://w3id.org/security/v1',
-                       ['Emoji' => 'toot:Emoji', 'Hashtag' => 'as:Hashtag', 'atomUri' => 'ostatus:atomUri',
-                       'conversation' => 'ostatus:conversation', 'inReplyToAtomUri' => 'ostatus:inReplyToAtomUri',
-                       'ostatus' => 'http://ostatus.org#', 'sensitive' => 'as:sensitive',
-                       'toot' => 'http://joinmastodon.org/ns#']]];
+                       ['ostatus' => 'http://ostatus.org#', 'sensitive' => 'as:sensitive',
+                       'Hashtag' => 'as:Hashtag', 'atomUri' => 'ostatus:atomUri',
+                       'conversation' => 'ostatus:conversation',
+                       'inReplyToAtomUri' => 'ostatus:inReplyToAtomUri']]];
 
+               $data['id'] = $item['uri'] . '#activity';
                $data['type'] = 'Create';
-               $data['id'] = $item['uri'];
                $data['actor'] = $item['author-link'];
-               $data['to'] = 'https://www.w3.org/ns/activitystreams#Public';
-               $data['object'] = self::createNote($item);
+
+               $data['published'] = DateTimeFormat::utc($item["created"]."+00:00", DateTimeFormat::ATOM);
+
+               if ($item["created"] != $item["edited"]) {
+                       $data['updated'] = DateTimeFormat::utc($item["edited"]."+00:00", DateTimeFormat::ATOM);
+               }
+
+               $data['context_id'] = $item['parent'];
+               $data['context'] = self::createConversationURLFromItem($item);
+
+               $data = array_merge($data, ActivityPub::createPermissionBlockForItem($item));
+
+               $data['object'] = self::createObjectTypeFromItem($item);
+
+               $owner = User::getOwnerDataById($item['uid']);
+
+               return LDSignature::sign($data, $owner);
+       }
+
+       public static function createObjectFromItemID($item_id)
+       {
+               $item = Item::selectFirst([], ['id' => $item_id]);
+
+               if (!DBA::isResult($item)) {
+                       return false;
+               }
+
+               $data = ['@context' => ['https://www.w3.org/ns/activitystreams', 'https://w3id.org/security/v1',
+                       ['ostatus' => 'http://ostatus.org#', 'sensitive' => 'as:sensitive',
+                       'Hashtag' => 'as:Hashtag', 'atomUri' => 'ostatus:atomUri',
+                       'conversation' => 'ostatus:conversation',
+                       'inReplyToAtomUri' => 'ostatus:inReplyToAtomUri']]];
+
+               $data = array_merge($data, self::createObjectTypeFromItem($item));
+
+
                return $data;
        }
 
-       public static function createNote($item)
+       private static function createTagList($item)
        {
-               $data = [];
-               $data['type'] = 'Note';
-               $data['id'] = $item['uri'];
+               $tags = [];
+
+               $terms = Term::tagArrayFromItemId($item['id']);
+               foreach ($terms as $term) {
+                       if ($term['type'] == TERM_MENTION) {
+                               $contact = Contact::getDetailsByURL($term['url']);
+                               if (!empty($contact['addr'])) {
+                                       $mention = '@' . $contact['addr'];
+                               } else {
+                                       $mention = '@' . $term['url'];
+                               }
 
-               if ($item['uri'] != $item['thr-parent']) {
-                       $data['inReplyTo'] = $item['thr-parent'];
+                               $tags[] = ['type' => 'Mention', 'href' => $term['url'], 'name' => $mention];
+                       }
                }
+               return $tags;
+       }
 
+       private static function createConversationURLFromItem($item)
+       {
                $conversation = DBA::selectFirst('conversation', ['conversation-uri'], ['item-uri' => $item['parent-uri']]);
                if (DBA::isResult($conversation) && !empty($conversation['conversation-uri'])) {
                        $conversation_uri = $conversation['conversation-uri'];
                } else {
                        $conversation_uri = $item['parent-uri'];
                }
+               return $conversation_uri;
+       }
 
-               $data['context'] = $data['conversation'] = $conversation_uri;
-               $data['actor'] = $item['author-link'];
-               $data['to'] = [];
-               if (!$item['private']) {
-                       $data['to'][] = 'https://www.w3.org/ns/activitystreams#Public';
+       private static function createObjectTypeFromItem($item)
+       {
+               if (!empty($item['title'])) {
+                       $type = 'Article';
+               } else {
+                       $type = 'Note';
                }
+
+               $data = [];
+               $data['id'] = $item['uri'];
+               $data['type'] = $type;
+               $data['summary'] = null; // Ignore by now
+
+               if ($item['uri'] != $item['thr-parent']) {
+                       $data['inReplyTo'] = $item['thr-parent'];
+               } else {
+                       $data['inReplyTo'] = null;
+               }
+
                $data['published'] = DateTimeFormat::utc($item["created"]."+00:00", DateTimeFormat::ATOM);
-               $data['updated'] = DateTimeFormat::utc($item["edited"]."+00:00", DateTimeFormat::ATOM);
+
+               if ($item["created"] != $item["edited"]) {
+                       $data['updated'] = DateTimeFormat::utc($item["edited"]."+00:00", DateTimeFormat::ATOM);
+               }
+
+               $data['url'] = $item['plink'];
                $data['attributedTo'] = $item['author-link'];
-               $data['name'] = BBCode::convert($item['title'], false, 7);
+               $data['actor'] = $item['author-link'];
+               $data['sensitive'] = false; // - Query NSFW
+               $data['context_id'] = $item['parent'];
+               $data['conversation'] = $data['context'] = self::createConversationURLFromItem($item);
+
+               if (!empty($item['title'])) {
+                       $data['name'] = BBCode::convert($item['title'], false, 7);
+               }
+
                $data['content'] = BBCode::convert($item['body'], false, 7);
                $data['source'] = ['content' => $item['body'], 'mediaType' => "text/bbcode"];
-               //$data['summary'] = ''; // Ignore by now
-               //$data['sensitive'] = false; // - Query NSFW
+               $data['attachment'] = []; // @ToDo
+               $data['tag'] = self::createTagList($item);
+               $data = array_merge($data, ActivityPub::createPermissionBlockForItem($item));
+
                //$data['emoji'] = []; // Ignore by now
-               //$data['tag'] = []; /// @ToDo
-               //$data['attachment'] = []; // @ToDo
                return $data;
        }
 
        public static function transmitActivity($activity, $target, $uid)
        {
-               $profile = Probe::uri($target, Protocol::ACTIVITYPUB);
+               $profile = self::fetchprofile($target);
 
                $owner = User::getOwnerDataById($uid);
 
@@ -207,15 +439,18 @@ class ActivityPub
                        'id' => System::baseUrl() . '/activity/' . System::createGUID(),
                        'type' => $activity,
                        'actor' => $owner['url'],
-                       'object' => $profile['url']];
+                       'object' => $profile['url'],
+                       'to' => $profile['url']];
 
                logger('Sending activity ' . $activity . ' to ' . $target . ' for user ' . $uid, LOGGER_DEBUG);
-               return self::transmit($data,  $profile['notify'], $uid);
+
+               $signed = LDSignature::sign($data, $owner);
+               return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
        }
 
        public static function transmitContactAccept($target, $id, $uid)
        {
-               $profile = Probe::uri($target, Protocol::ACTIVITYPUB);
+               $profile = self::fetchprofile($target);
 
                $owner = User::getOwnerDataById($uid);
                $data = ['@context' => 'https://www.w3.org/ns/activitystreams',
@@ -224,31 +459,55 @@ class ActivityPub
                        'actor' => $owner['url'],
                        'object' => ['id' => $id, 'type' => 'Follow',
                                'actor' => $profile['url'],
-                               'object' => $owner['url']]];
+                               'object' => $owner['url']],
+                       'to' => $profile['url']];
 
                logger('Sending accept to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
-               return self::transmit($data,  $profile['notify'], $uid);
+
+               $signed = LDSignature::sign($data, $owner);
+               return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
        }
 
-       public static function transmitContactUndo($target, $id, $uid)
+       public static function transmitContactReject($target, $id, $uid)
        {
-               $profile = Probe::uri($target, Protocol::ACTIVITYPUB);
-
-               if (empty($id)) {
-                       $id = System::baseUrl() . '/activity/' . System::createGUID();
-               }
+               $profile = self::fetchprofile($target);
 
                $owner = User::getOwnerDataById($uid);
                $data = ['@context' => 'https://www.w3.org/ns/activitystreams',
                        'id' => System::baseUrl() . '/activity/' . System::createGUID(),
+                       'type' => 'Reject',
+                       'actor' => $owner['url'],
+                       'object' => ['id' => $id, 'type' => 'Follow',
+                               'actor' => $profile['url'],
+                               'object' => $owner['url']],
+                       'to' => $profile['url']];
+
+               logger('Sending reject to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
+
+               $signed = LDSignature::sign($data, $owner);
+               return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+       }
+
+       public static function transmitContactUndo($target, $uid)
+       {
+               $profile = self::fetchprofile($target);
+
+               $id = System::baseUrl() . '/activity/' . System::createGUID();
+
+               $owner = User::getOwnerDataById($uid);
+               $data = ['@context' => 'https://www.w3.org/ns/activitystreams',
+                       'id' => $id,
                        'type' => 'Undo',
                        'actor' => $owner['url'],
                        'object' => ['id' => $id, 'type' => 'Follow',
                                'actor' => $owner['url'],
-                               'object' => $profile['url']]];
+                               'object' => $profile['url']],
+                       'to' => $profile['url']];
 
                logger('Sending undo to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
-               return self::transmit($data,  $profile['notify'], $uid);
+
+               $signed = LDSignature::sign($data, $owner);
+               return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
        }
 
        /**
@@ -259,8 +518,7 @@ class ActivityPub
         */
        public static function fetchContent($url)
        {
-               $ret = Network::curl($url, false, $redirects, ['accept_content' => 'application/activity+json']);
-
+               $ret = Network::curl($url, false, $redirects, ['accept_content' => 'application/activity+json, application/ld+json']);
                if (!$ret['success'] || empty($ret['body'])) {
                        return;
                }
@@ -307,208 +565,126 @@ class ActivityPub
                return false;
        }
 
-       public static function verifySignature($content, $http_headers)
+       public static function fetchprofile($url, $update = false)
        {
-               $object = json_decode($content, true);
-
-               if (empty($object)) {
+               if (empty($url)) {
                        return false;
                }
 
-               $actor = self::processElement($object, 'actor', 'id');
-
-               $headers = [];
-               $headers['(request-target)'] = strtolower($http_headers['REQUEST_METHOD']) . ' ' . $http_headers['REQUEST_URI'];
-
-               // First take every header
-               foreach ($http_headers as $k => $v) {
-                       $field = str_replace('_', '-', strtolower($k));
-                       $headers[$field] = $v;
-               }
-
-               // Now add every http header
-               foreach ($http_headers as $k => $v) {
-                       if (strpos($k, 'HTTP_') === 0) {
-                               $field = str_replace('_', '-', strtolower(substr($k, 5)));
-                               $headers[$field] = $v;
+               if (!$update) {
+                       $apcontact = DBA::selectFirst('apcontact', [], ['url' => $url]);
+                       if (DBA::isResult($apcontact)) {
+                               return $apcontact;
                        }
-               }
 
-               $sig_block = ActivityPub::parseSigHeader($http_headers['HTTP_SIGNATURE']);
-
-               if (empty($sig_block) || empty($sig_block['headers']) || empty($sig_block['keyId'])) {
-                       return false;
-               }
-
-               $signed_data = '';
-               foreach ($sig_block['headers'] as $h) {
-                       if (array_key_exists($h, $headers)) {
-                               $signed_data .= $h . ': ' . $headers[$h] . "\n";
+                       $apcontact = DBA::selectFirst('apcontact', [], ['alias' => $url]);
+                       if (DBA::isResult($apcontact)) {
+                               return $apcontact;
                        }
-               }
-               $signed_data = rtrim($signed_data, "\n");
-
-               if (empty($signed_data)) {
-                       return false;
-               }
 
-               $algorithm = null;
-
-               if ($sig_block['algorithm'] === 'rsa-sha256') {
-                       $algorithm = 'sha256';
-               }
-
-               if ($sig_block['algorithm'] === 'rsa-sha512') {
-                       $algorithm = 'sha512';
+                       $apcontact = DBA::selectFirst('apcontact', [], ['addr' => $url]);
+                       if (DBA::isResult($apcontact)) {
+                               return $apcontact;
+                       }
                }
 
-               if (empty($algorithm)) {
-                       return false;
+               if (empty(parse_url($url, PHP_URL_SCHEME))) {
+                       $url = self::addrToUrl($url);
+                       if (empty($url)) {
+                               return false;
+                       }
                }
 
-               $key = self::fetchKey($sig_block['keyId'], $actor);
-
-               if (empty($key)) {
-                       return false;
-               }
+               $data = self::fetchContent($url);
 
-               if (!Crypto::rsaVerify($signed_data, $sig_block['signature'], $key, $algorithm)) {
+               if (empty($data) || empty($data['id']) || empty($data['inbox'])) {
                        return false;
                }
 
-               // Check the digest if it was part of the signed data
-               if (in_array('digest', $sig_block['headers'])) {
-                       $digest = explode('=', $headers['digest'], 2);
-                       if ($digest[0] === 'SHA-256') {
-                               $hashalg = 'sha256';
-                       }
-                       if ($digest[0] === 'SHA-512') {
-                               $hashalg = 'sha512';
-                       }
-
-                       /// @todo add all hashes from the rfc
-
-                       if (!empty($hashalg) && base64_encode(hash($hashalg, $content, true)) != $digest[1]) {
-                               return false;
-                       }
-               }
-
-               // Check the content-length if it was part of the signed data
-               if (in_array('content-length', $sig_block['headers'])) {
-                       if (strlen($content) != $headers['content-length']) {
-                               return false;
-                       }
-               }
+               $apcontact = [];
+               $apcontact['url'] = $data['id'];
+               $apcontact['uuid'] = defaults($data, 'uuid', null);
+               $apcontact['type'] = defaults($data, 'type', null);
+               $apcontact['following'] = defaults($data, 'following', null);
+               $apcontact['followers'] = defaults($data, 'followers', null);
+               $apcontact['inbox'] = defaults($data, 'inbox', null);
+               $apcontact['outbox'] = defaults($data, 'outbox', null);
+               $apcontact['sharedinbox'] = JsonLD::fetchElement($data, 'endpoints', 'sharedInbox');
+               $apcontact['nick'] = defaults($data, 'preferredUsername', null);
+               $apcontact['name'] = defaults($data, 'name', $apcontact['nick']);
+               $apcontact['about'] = defaults($data, 'summary', '');
+               $apcontact['photo'] = JsonLD::fetchElement($data, 'icon', 'url');
+               $apcontact['alias'] = JsonLD::fetchElement($data, 'url', 'href');
+
+               $parts = parse_url($apcontact['url']);
+               unset($parts['scheme']);
+               unset($parts['path']);
+               $apcontact['addr'] = $apcontact['nick'] . '@' . str_replace('//', '', Network::unparseURL($parts));
 
-               return true;
+               $apcontact['pubkey'] = trim(JsonLD::fetchElement($data, 'publicKey', 'publicKeyPem'));
 
-       }
+               // To-Do
+               // manuallyApprovesFollowers
 
-       private static function fetchKey($id, $actor)
-       {
-               $url = (strpos($id, '#') ? substr($id, 0, strpos($id, '#')) : $id);
-
-               $profile = Probe::uri($url, Protocol::ACTIVITYPUB);
-               if (!empty($profile)) {
-                       return $profile['pubkey'];
-               } elseif ($url != $actor) {
-                       $profile = Probe::uri($actor, Protocol::ACTIVITYPUB);
-                       if (!empty($profile)) {
-                               return $profile['pubkey'];
-                       }
-               }
+               // Unhandled
+               // @context, tag, attachment, image, nomadicLocations, signature, following, followers, featured, movedTo, liked
 
-               return false;
-       }
+               // Unhandled from Misskey
+               // sharedInbox, isCat
 
-       /**
-        * @brief
-        *
-        * @param string $header
-        * @return array associate array with
-        *   - \e string \b keyID
-        *   - \e string \b algorithm
-        *   - \e array  \b headers
-        *   - \e string \b signature
-        */
-       private static function parseSigHeader($header)
-       {
-               $ret = [];
-               $matches = [];
+               // Unhandled from Kroeg
+               // kroeg:blocks, updated
 
-               if (preg_match('/keyId="(.*?)"/ism',$header,$matches)) {
-                       $ret['keyId'] = $matches[1];
+               // Check if the address is resolvable
+               if (self::addrToUrl($apcontact['addr']) == $apcontact['url']) {
+                       $parts = parse_url($apcontact['url']);
+                       unset($parts['path']);
+                       $apcontact['baseurl'] = Network::unparseURL($parts);
+               } else {
+                       $apcontact['addr'] = null;
                }
 
-               if (preg_match('/algorithm="(.*?)"/ism',$header,$matches)) {
-                       $ret['algorithm'] = $matches[1];
+               if ($apcontact['url'] == $apcontact['alias']) {
+                       $apcontact['alias'] = null;
                }
 
-               if (preg_match('/headers="(.*?)"/ism',$header,$matches)) {
-                       $ret['headers'] = explode(' ', $matches[1]);
-               }
+               $apcontact['updated'] = DateTimeFormat::utcNow();
 
-               if (preg_match('/signature="(.*?)"/ism',$header,$matches)) {
-                       $ret['signature'] = base64_decode(preg_replace('/\s+/','',$matches[1]));
-               }
+               DBA::update('apcontact', $apcontact, ['url' => $url], true);
 
-               return $ret;
+               return $apcontact;
        }
 
        /**
-        * Fetches a profile from the given url
+        * Fetches a profile from the given url into an array that is compatible to Probe::uri
         *
         * @param string $url profile url
         * @return array
         */
-       public static function fetchProfile($url)
+       public static function probeProfile($url)
        {
-               if (empty(parse_url($url, PHP_URL_SCHEME))) {
-                       $url = self::addrToUrl($url);
-                       if (empty($url)) {
-                               return false;
-                       }
-               }
-
-               $data = self::fetchContent($url);
-
-               if (empty($data) || empty($data['id']) || empty($data['inbox'])) {
+               $apcontact = self::fetchprofile($url, true);
+               if (empty($apcontact)) {
                        return false;
                }
 
                $profile = ['network' => Protocol::ACTIVITYPUB];
-               $profile['nick'] = $data['preferredUsername'];
-               $profile['name'] = defaults($data, 'name', $profile['nick']);
-               $profile['guid'] = defaults($data, 'uuid', null);
-               $profile['url'] = $data['id'];
-
-               $parts = parse_url($profile['url']);
-               unset($parts['scheme']);
-               unset($parts['path']);
-               $profile['addr'] = $profile['nick'] . '@' . str_replace('//', '', Network::unparseURL($parts));
-               $profile['alias'] = self::processElement($data, 'url', 'href');
-               $profile['photo'] = self::processElement($data, 'icon', 'url');
+               $profile['nick'] = $apcontact['nick'];
+               $profile['name'] = $apcontact['name'];
+               $profile['guid'] = $apcontact['uuid'];
+               $profile['url'] = $apcontact['url'];
+               $profile['addr'] = $apcontact['addr'];
+               $profile['alias'] = $apcontact['alias'];
+               $profile['photo'] = $apcontact['photo'];
                // $profile['community']
                // $profile['keywords']
                // $profile['location']
-               $profile['about'] = defaults($data, 'summary', '');
-               $profile['batch'] = self::processElement($data, 'endpoints', 'sharedInbox');
-               $profile['notify'] = $data['inbox'];
-               $profile['poll'] = $data['outbox'];
-               $profile['pubkey'] = self::processElement($data, 'publicKey', 'publicKeyPem');
-
-               // Check if the address is resolvable
-               if (self::addrToUrl($profile['addr']) == $profile['url']) {
-                       $parts = parse_url($profile['url']);
-                       unset($parts['path']);
-                       $profile['baseurl'] = Network::unparseURL($parts);
-               } else {
-                       unset($profile['addr']);
-               }
-
-               if ($profile['url'] == $profile['alias']) {
-                       unset($profile['alias']);
-               }
+               $profile['about'] = $apcontact['about'];
+               $profile['batch'] = $apcontact['sharedinbox'];
+               $profile['notify'] = $apcontact['inbox'];
+               $profile['poll'] = $apcontact['outbox'];
+               $profile['pubkey'] = $apcontact['pubkey'];
+               $profile['baseurl'] = $apcontact['baseurl'];
 
                // Remove all "null" fields
                foreach ($profile as $field => $content) {
@@ -517,51 +693,56 @@ class ActivityPub
                        }
                }
 
-/*
-               // To-Do
-               unset($data['type']);
-               unset($data['manuallyApprovesFollowers']);
-
-               // Unhandled
-               unset($data['@context']);
-               unset($data['tag']);
-               unset($data['attachment']);
-               unset($data['image']);
-               unset($data['nomadicLocations']);
-               unset($data['signature']);
-               unset($data['following']);
-               unset($data['followers']);
-               unset($data['featured']);
-               unset($data['movedTo']);
-               unset($data['liked']);
-               unset($data['sharedInbox']); // Misskey
-               unset($data['isCat']); // Misskey
-               unset($data['kroeg:blocks']); // Kroeg
-               unset($data['updated']); // Kroeg
-*/
                return $profile;
        }
 
        public static function processInbox($body, $header, $uid)
        {
-               logger('Incoming message for user ' . $uid, LOGGER_DEBUG);
-
-               if (!self::verifySignature($body, $header)) {
-                       logger('Invalid signature, message will be discarded.', LOGGER_DEBUG);
+               $http_signer = HTTPSignature::getSigner($body, $header);
+               if (empty($http_signer)) {
+                       logger('Invalid HTTP signature, message will be discarded.', LOGGER_DEBUG);
                        return;
+               } else {
+                       logger('HTTP signature is signed by ' . $http_signer, LOGGER_DEBUG);
                }
 
                $activity = json_decode($body, true);
 
-               if (!is_array($activity)) {
+               $actor = JsonLD::fetchElement($activity, 'actor', 'id');
+               logger('Message for user ' . $uid . ' is from actor ' . $actor, LOGGER_DEBUG);
+
+               if (empty($activity)) {
                        logger('Invalid body.', LOGGER_DEBUG);
                        return;
                }
 
-               self::processActivity($activity, $body, $uid);
+               if (LDSignature::isSigned($activity)) {
+                       $ld_signer = LDSignature::getSigner($activity);
+                       if (!empty($ld_signer && ($actor == $http_signer))) {
+                               logger('The HTTP and the JSON-LD signature belong to ' . $ld_signer, LOGGER_DEBUG);
+                               $trust_source = true;
+                       } elseif (!empty($ld_signer)) {
+                               logger('JSON-LD signature is signed by ' . $ld_signer, LOGGER_DEBUG);
+                               $trust_source = true;
+                       } elseif ($actor == $http_signer) {
+                               logger('Bad JSON-LD signature, but HTTP signer fits the actor.', LOGGER_DEBUG);
+                               $trust_source = true;
+                       } else {
+                               logger('Invalid JSON-LD signature and the HTTP signer is different.', LOGGER_DEBUG);
+                               $trust_source = false;
+                       }
+               } elseif ($actor == $http_signer) {
+                       logger('Trusting post without JSON-LD signature, The actor fits the HTTP signer.', LOGGER_DEBUG);
+                       $trust_source = true;
+               } else {
+                       logger('No JSON-LD signature, different actor.', LOGGER_DEBUG);
+                       $trust_source = false;
+               }
+
+               self::processActivity($activity, $body, $uid, $trust_source);
        }
 
-       public static function fetchOutbox($url)
+       public static function fetchOutbox($url, $uid)
        {
                $data = self::fetchContent($url);
                if (empty($data)) {
@@ -573,40 +754,36 @@ class ActivityPub
                } elseif (!empty($data['first']['orderedItems'])) {
                        $items = $data['first']['orderedItems'];
                } elseif (!empty($data['first'])) {
-                       self::fetchOutbox($data['first']);
+                       self::fetchOutbox($data['first'], $uid);
                        return;
                } else {
                        $items = [];
                }
 
                foreach ($items as $activity) {
-                       self::processActivity($activity);
+                       self::processActivity($activity, '', $uid, true);
                }
        }
 
-       function processActivity($activity, $body = '', $uid = null)
+       private static function prepareObjectData($activity, $uid, $trust_source)
        {
-               if (empty($activity['type'])) {
-                       logger('Empty type', LOGGER_DEBUG);
-                       return;
-               }
-
-               if (empty($activity['object'])) {
-                       logger('Empty object', LOGGER_DEBUG);
-                       return;
+               $actor = JsonLD::fetchElement($activity, 'actor', 'id');
+               if (empty($actor)) {
+                       logger('Empty actor', LOGGER_DEBUG);
+                       return [];
                }
 
-               if (empty($activity['actor'])) {
-                       logger('Empty actor', LOGGER_DEBUG);
-                       return;
+               // Fetch all receivers from to, cc, bto and bcc
+               $receivers = self::getReceivers($activity, $actor);
 
+               // When it is a delivery to a personal inbox we add that user to the receivers
+               if (!empty($uid)) {
+                       $owner = User::getOwnerDataById($uid);
+                       $additional = ['uid:' . $uid => $uid];
+                       $receivers = array_merge($receivers, $additional);
                }
 
-               $actor = self::processElement($activity, 'actor', 'id');
-               if (empty($actor)) {
-                       logger('Empty actor - 2', LOGGER_DEBUG);
-                       return;
-               }
+               logger('Receivers: ' . json_encode($receivers), LOGGER_DEBUG);
 
                if (is_string($activity['object'])) {
                        $object_url = $activity['object'];
@@ -614,93 +791,112 @@ class ActivityPub
                        $object_url = $activity['object']['id'];
                } else {
                        logger('No object found', LOGGER_DEBUG);
-                       return;
+                       return [];
                }
 
-               // ----------------------------------
-/*
-               // unhandled
-               unset($activity['@context']);
-               unset($activity['id']);
+               // Fetch the content only on activities where this matters
+               if (in_array($activity['type'], ['Create', 'Update', 'Announce'])) {
+                       $object_data = self::fetchObject($object_url, $activity['object'], $trust_source);
+                       if (empty($object_data)) {
+                               logger("Object data couldn't be processed", LOGGER_DEBUG);
+                               return [];
+                       }
+               } elseif ($activity['type'] == 'Accept') {
+                       $object_data = [];
+                       $object_data['object_type'] = JsonLD::fetchElement($activity, 'object', 'type');
+                       $object_data['object'] = JsonLD::fetchElement($activity, 'object', 'actor');
+               } elseif ($activity['type'] == 'Undo') {
+                       $object_data = [];
+                       $object_data['object_type'] = JsonLD::fetchElement($activity, 'object', 'type');
+                       $object_data['object'] = JsonLD::fetchElement($activity, 'object', 'object');
+               } elseif (in_array($activity['type'], ['Like', 'Dislike'])) {
+                       // Create a mostly empty array out of the activity data (instead of the object).
+                       // This way we later don't have to check for the existence of ech individual array element.
+                       $object_data = self::processCommonData($activity);
+                       $object_data['name'] = $activity['type'];
+                       $object_data['author'] = $activity['actor'];
+                       $object_data['object'] = $object_url;
+               } elseif ($activity['type'] == 'Follow') {
+                       $object_data['id'] = $activity['id'];
+                       $object_data['object'] = $object_url;
+               } else {
+                       $object_data = [];
+               }
 
-               // Non standard
-               unset($activity['title']);
-               unset($activity['atomUri']);
-               unset($activity['context_id']);
-               unset($activity['statusnetConversationId']);
+               $object_data = self::addActivityFields($object_data, $activity);
 
-               // To-Do?
-               unset($activity['context']);
-               unset($activity['location']);
-               unset($activity['signature']);
-*/
-               // Fetch all receivers from to, cc, bto and bcc
-               $receivers = self::getReceivers($activity);
+               $object_data['type'] = $activity['type'];
+               $object_data['owner'] = $actor;
+               $object_data['receiver'] = array_merge(defaults($object_data, 'receiver', []), $receivers);
 
-               // When it is a delivery to a personal inbox we add that user to the receivers
-               if (!empty($uid)) {
-                       $owner = User::getOwnerDataById($uid);
-                       $additional = [$owner['url'] => $uid];
-                       $receivers = array_merge($receivers, $additional);
+               return $object_data;
+       }
+
+       private static function processActivity($activity, $body = '', $uid = null, $trust_source = false)
+       {
+               if (empty($activity['type'])) {
+                       logger('Empty type', LOGGER_DEBUG);
+                       return;
                }
 
-               logger('Receivers: ' . json_encode($receivers), LOGGER_DEBUG);
+               if (empty($activity['object'])) {
+                       logger('Empty object', LOGGER_DEBUG);
+                       return;
+               }
 
-               logger('Processing activity: ' . $activity['type'], LOGGER_DEBUG);
+               if (empty($activity['actor'])) {
+                       logger('Empty actor', LOGGER_DEBUG);
+                       return;
 
-               // Fetch the content only on activities where this matters
-               if (in_array($activity['type'], ['Create', 'Update', 'Announce'])) {
-                       $item = self::fetchObject($object_url, $activity['object']);
-                       if (empty($item)) {
-                               logger("Object data couldn't be processed", LOGGER_DEBUG);
-                               return;
-                       }
-               } else {
-                       if (in_array($activity['type'], ['Accept'])) {
-                               $item['object'] = self::processElement($activity, 'object', 'actor', 'type', 'Follow');
-                       } elseif (in_array($activity['type'], ['Undo'])) {
-                               $item['object'] = self::processElement($activity, 'object', 'object', 'type', 'Follow');
-                       } else {
-                               $item['object'] = $object_url;
-                       }
-                       $item['id'] = $activity['id'];
-                       $item['receiver'] = [];
-                       $item['type'] = $activity['type'];
                }
 
-               $item = self::addActivityFields($item, $activity);
+               // Non standard
+               // title, atomUri, context_id, statusnetConversationId
+
+               // To-Do?
+               // context, location, signature;
 
-               $item['owner'] = $actor;
+               logger('Processing activity: ' . $activity['type'], LOGGER_DEBUG);
 
-               $item['receiver'] = array_merge($item['receiver'], $receivers);
+               $object_data = self::prepareObjectData($activity, $uid, $trust_source);
+               if (empty($object_data)) {
+                       logger('No object data found', LOGGER_DEBUG);
+                       return;
+               }
 
                switch ($activity['type']) {
                        case 'Create':
-                       case 'Update':
                        case 'Announce':
-                               self::createItem($item, $body);
+                               self::createItem($object_data, $body);
                                break;
 
                        case 'Like':
-                               self::likeItem($item, $body);
+                               self::likeItem($object_data, $body);
                                break;
 
                        case 'Dislike':
                                break;
 
+                       case 'Update':
+                               break;
+
                        case 'Delete':
                                break;
 
                        case 'Follow':
-                               self::followUser($item);
+                               self::followUser($object_data);
                                break;
 
                        case 'Accept':
-                               self::acceptFollowUser($item);
+                               if ($object_data['object_type'] == 'Follow') {
+                                       self::acceptFollowUser($object_data);
+                               }
                                break;
 
                        case 'Undo':
-                               self::undoFollowUser($item);
+                               if ($object_data['object_type'] == 'Follow') {
+                                       self::undoFollowUser($object_data);
+                               }
                                break;
 
                        default:
@@ -709,10 +905,29 @@ class ActivityPub
                }
        }
 
-       private static function getReceivers($activity)
+       private static function getReceivers($activity, $actor)
        {
                $receivers = [];
 
+               // When it is an answer, we inherite the receivers from the parent
+               $replyto = JsonLD::fetchElement($activity, 'inReplyTo', 'id');
+               if (!empty($replyto)) {
+                       $parents = Item::select(['uid'], ['uri' => $replyto]);
+                       while ($parent = Item::fetch($parents)) {
+                               $receivers['uid:' . $parent['uid']] = $parent['uid'];
+                       }
+               }
+
+               if (!empty($actor)) {
+                       $profile = self::fetchprofile($actor);
+                       $followers = defaults($profile, 'followers', '');
+
+                       logger('Actor: ' . $actor . ' - Followers: ' . $followers, LOGGER_DEBUG);
+               } else {
+                       logger('Empty actor', LOGGER_DEBUG);
+                       $followers = '';
+               }
+
                $elements = ['to', 'cc', 'bto', 'bcc'];
                foreach ($elements as $element) {
                        if (empty($activity[$element])) {
@@ -726,7 +941,32 @@ class ActivityPub
 
                        foreach ($activity[$element] as $receiver) {
                                if ($receiver == self::PUBLIC) {
-                                       $receivers[$receiver] = 0;
+                                       $receivers['uid:0'] = 0;
+                               }
+
+                               if (($receiver == self::PUBLIC) && !empty($actor)) {
+                                       // This will most likely catch all OStatus connections to Mastodon
+                                       $condition = ['alias' => [$actor, normalise_link($actor)], 'rel' => [Contact::SHARING, Contact::FRIEND]];
+                                       $contacts = DBA::select('contact', ['uid'], $condition);
+                                       while ($contact = DBA::fetch($contacts)) {
+                                               if ($contact['uid'] != 0) {
+                                                       $receivers['uid:' . $contact['uid']] = $contact['uid'];
+                                               }
+                                       }
+                                       DBA::close($contacts);
+                               }
+
+                               if (in_array($receiver, [$followers, self::PUBLIC]) && !empty($actor)) {
+                                       $condition = ['nurl' => normalise_link($actor), 'rel' => [Contact::SHARING, Contact::FRIEND],
+                                               'network' => Protocol::ACTIVITYPUB];
+                                       $contacts = DBA::select('contact', ['uid'], $condition);
+                                       while ($contact = DBA::fetch($contacts)) {
+                                               if ($contact['uid'] != 0) {
+                                                       $receivers['uid:' . $contact['uid']] = $contact['uid'];
+                                               }
+                                       }
+                                       DBA::close($contacts);
+                                       continue;
                                }
 
                                $condition = ['self' => true, 'nurl' => normalise_link($receiver)];
@@ -734,52 +974,55 @@ class ActivityPub
                                if (!DBA::isResult($contact)) {
                                        continue;
                                }
-                               $receivers[$receiver] = $contact['uid'];
+                               $receivers['uid:' . $contact['uid']] = $contact['uid'];
                        }
                }
                return $receivers;
        }
 
-       private static function addActivityFields($item, $activity)
+       private static function addActivityFields($object_data, $activity)
        {
-               if (!empty($activity['published']) && empty($item['published'])) {
-                       $item['published'] = $activity['published'];
+               if (!empty($activity['published']) && empty($object_data['published'])) {
+                       $object_data['published'] = $activity['published'];
                }
 
-               if (!empty($activity['updated']) && empty($item['updated'])) {
-                       $item['updated'] = $activity['updated'];
+               if (!empty($activity['updated']) && empty($object_data['updated'])) {
+                       $object_data['updated'] = $activity['updated'];
                }
 
-               if (!empty($activity['inReplyTo']) && empty($item['parent-uri'])) {
-                       $item['parent-uri'] = self::processElement($activity, 'inReplyTo', 'id');
+               if (!empty($activity['inReplyTo']) && empty($object_data['parent-uri'])) {
+                       $object_data['parent-uri'] = JsonLD::fetchElement($activity, 'inReplyTo', 'id');
                }
 
                if (!empty($activity['instrument'])) {
-                       $item['service'] = self::processElement($activity, 'instrument', 'name', 'type', 'Service');
+                       $object_data['service'] = JsonLD::fetchElement($activity, 'instrument', 'name', 'type', 'Service');
                }
-               return $item;
+               return $object_data;
        }
 
-       private static function fetchObject($object_url, $object = [])
+       private static function fetchObject($object_url, $object = [], $trust_source = false)
        {
-               $data = self::fetchContent($object_url);
-               if (empty($data)) {
-                       $data = $object;
+               if (!$trust_source || is_string($object)) {
+                       $data = self::fetchContent($object_url);
                        if (empty($data)) {
-                               logger('Empty content', LOGGER_DEBUG);
-                               return false;
-                       } elseif (is_string($data)) {
-                               logger('No object array provided.', LOGGER_DEBUG);
-                               $item = Item::selectFirst([], ['uri' => $data]);
-                               if (!DBA::isResult($item)) {
-                                       logger('Object with url ' . $data . ' was not found locally.', LOGGER_DEBUG);
-                                       return false;
-                               }
-                               logger('Using already stored item', LOGGER_DEBUG);
-                               $data = self::createNote($item);
+                               logger('Empty content for ' . $object_url . ', check if content is available locally.', LOGGER_DEBUG);
+                               $data = $object_url;
                        } else {
-                               logger('Using provided object', LOGGER_DEBUG);
+                               logger('Fetched content for ' . $object_url, LOGGER_DEBUG);
+                       }
+               } else {
+                       logger('Using original object for url ' . $object_url, LOGGER_DEBUG);
+                       $data = $object;
+               }
+
+               if (is_string($data)) {
+                       $item = Item::selectFirst([], ['uri' => $data]);
+                       if (!DBA::isResult($item)) {
+                               logger('Object with url ' . $data . ' was not found locally.', LOGGER_DEBUG);
+                               return false;
                        }
+                       logger('Using already stored item for url ' . $object_url, LOGGER_DEBUG);
+                       $data = self::createObjectTypeFromItem($item);
                }
 
                if (empty($data['type'])) {
@@ -820,153 +1063,86 @@ class ActivityPub
 
        private static function processCommonData(&$object)
        {
-               if (empty($object['id']) || empty($object['attributedTo'])) {
+               if (empty($object['id'])) {
                        return false;
                }
 
-               $item = [];
-               $item['type'] = $object['type'];
-               $item['uri'] = $object['id'];
+               $object_data = [];
+               $object_data['type'] = $object['type'];
+               $object_data['uri'] = $object['id'];
 
                if (!empty($object['inReplyTo'])) {
-                       $item['reply-to-uri'] = self::processElement($object, 'inReplyTo', 'id');
+                       $object_data['reply-to-uri'] = JsonLD::fetchElement($object, 'inReplyTo', 'id');
                } else {
-                       $item['reply-to-uri'] = $item['uri'];
-               }
-
-               $item['published'] = defaults($object, 'published', null);
-               $item['updated'] = defaults($object, 'updated', $item['published']);
-
-               if (empty($item['published']) && !empty($item['updated'])) {
-                       $item['published'] = $item['updated'];
-               }
-
-               $item['uuid'] = defaults($object, 'uuid', null);
-               $item['owner'] = $item['author'] = self::processElement($object, 'attributedTo', 'id');
-               $item['context'] = defaults($object, 'context', null);
-               $item['conversation'] = defaults($object, 'conversation', null);
-               $item['sensitive'] = defaults($object, 'sensitive', null);
-               $item['name'] = defaults($object, 'title', null);
-               $item['name'] = defaults($object, 'name', $item['name']);
-               $item['summary'] = defaults($object, 'summary', null);
-               $item['content'] = defaults($object, 'content', null);
-               $item['source'] = defaults($object, 'source', null);
-               $item['location'] = self::processElement($object, 'location', 'name', 'type', 'Place');
-               $item['attachments'] = defaults($object, 'attachment', null);
-               $item['tags'] = defaults($object, 'tag', null);
-               $item['service'] = self::processElement($object, 'instrument', 'name', 'type', 'Service');
-               $item['alternate-url'] = self::processElement($object, 'url', 'href');
-               $item['receiver'] = self::getReceivers($object);
-
-/*
-               // To-Do
-               unset($object['source']);
+                       $object_data['reply-to-uri'] = $object_data['uri'];
+               }
+
+               $object_data['published'] = defaults($object, 'published', null);
+               $object_data['updated'] = defaults($object, 'updated', $object_data['published']);
+
+               if (empty($object_data['published']) && !empty($object_data['updated'])) {
+                       $object_data['published'] = $object_data['updated'];
+               }
+
+               $object_data['uuid'] = defaults($object, 'uuid', null);
+               $object_data['owner'] = $object_data['author'] = JsonLD::fetchElement($object, 'attributedTo', 'id');
+               $object_data['context'] = defaults($object, 'context', null);
+               $object_data['conversation'] = defaults($object, 'conversation', null);
+               $object_data['sensitive'] = defaults($object, 'sensitive', null);
+               $object_data['name'] = defaults($object, 'title', null);
+               $object_data['name'] = defaults($object, 'name', $object_data['name']);
+               $object_data['summary'] = defaults($object, 'summary', null);
+               $object_data['content'] = defaults($object, 'content', null);
+               $object_data['source'] = defaults($object, 'source', null);
+               $object_data['location'] = JsonLD::fetchElement($object, 'location', 'name', 'type', 'Place');
+               $object_data['attachments'] = defaults($object, 'attachment', null);
+               $object_data['tags'] = defaults($object, 'tag', null);
+               $object_data['service'] = JsonLD::fetchElement($object, 'instrument', 'name', 'type', 'Service');
+               $object_data['alternate-url'] = JsonLD::fetchElement($object, 'url', 'href');
+               $object_data['receiver'] = self::getReceivers($object, $object_data['owner']);
 
                // Unhandled
-               unset($object['@context']);
-               unset($object['type']);
-               unset($object['actor']);
-               unset($object['signature']);
-               unset($object['mediaType']);
-               unset($object['duration']);
-               unset($object['replies']);
-               unset($object['icon']);
-
-               // Also missing:
-               audience, preview, endTime, startTime, generator, image
-*/
-               return $item;
+               // @context, type, actor, signature, mediaType, duration, replies, icon
+
+               // Also missing: (Defined in the standard, but currently unused)
+               // audience, preview, endTime, startTime, generator, image
+
+               return $object_data;
        }
 
        private static function processNote($object)
        {
-               $item = [];
+               $object_data = [];
 
-/*
                // To-Do?
-               unset($object['emoji']);
-               unset($object['atomUri']);
-               unset($object['inReplyToAtomUri']);
+               // emoji, atomUri, inReplyToAtomUri
 
                // Unhandled
-               unset($object['contentMap']);
-               unset($object['announcement_count']);
-               unset($object['announcements']);
-               unset($object['context_id']);
-               unset($object['likes']);
-               unset($object['like_count']);
-               unset($object['inReplyToStatusId']);
-               unset($object['shares']);
-               unset($object['quoteUrl']);
-               unset($object['statusnetConversationId']);
-*/
-               return $item;
+               // contentMap, announcement_count, announcements, context_id, likes, like_count
+               // inReplyToStatusId, shares, quoteUrl, statusnetConversationId
+
+               return $object_data;
        }
 
        private static function processArticle($object)
        {
-               $item = [];
+               $object_data = [];
 
-               return $item;
+               return $object_data;
        }
 
        private static function processVideo($object)
        {
-               $item = [];
-/*
+               $object_data = [];
+
                // To-Do?
-               unset($object['category']);
-               unset($object['licence']);
-               unset($object['language']);
-               unset($object['commentsEnabled']);
+               // category, licence, language, commentsEnabled
 
                // Unhandled
-               unset($object['views']);
-               unset($object['waitTranscoding']);
-               unset($object['state']);
-               unset($object['support']);
-               unset($object['subtitleLanguage']);
-               unset($object['likes']);
-               unset($object['dislikes']);
-               unset($object['shares']);
-               unset($object['comments']);
-*/
-               return $item;
-       }
-
-       private static function processElement($array, $element, $key, $type = null, $type_value = null)
-       {
-               if (empty($array)) {
-                       return false;
-               }
-
-               if (empty($array[$element])) {
-                       return false;
-               }
-
-               if (is_string($array[$element])) {
-                       return $array[$element];
-               }
-
-               if (is_null($type_value)) {
-                       if (!empty($array[$element][$key])) {
-                               return $array[$element][$key];
-                       }
-
-                       if (!empty($array[$element][0][$key])) {
-                               return $array[$element][0][$key];
-                       }
-
-                       return false;
-               }
+               // views, waitTranscoding, state, support, subtitleLanguage
+               // likes, dislikes, shares, comments
 
-               if (!empty($array[$element][$key]) && !empty($array[$element][$type]) && ($array[$element][$type] == $type_value)) {
-                       return $array[$element][$key];
-               }
-
-               /// @todo Add array search
-
-               return false;
+               return $object_data;
        }
 
        private static function convertMentions($body)
@@ -990,6 +1166,11 @@ class ActivityPub
                                        $tag_text .= ',';
                                }
 
+                               if (empty($tag['href'])) {
+                                       //$tag['href']
+                                       logger('Blubb!');
+                               }
+
                                $tag_text .= substr($tag['name'], 0, 1) . '[url=' . $tag['href'] . ']' . substr($tag['name'], 1) . '[/url]';
                        }
                }
@@ -1039,6 +1220,11 @@ class ActivityPub
                        $item['object-type'] = ACTIVITY_OBJ_COMMENT;
                }
 
+               if (($activity['uri'] != $activity['reply-to-uri']) && !Item::exists(['uri' => $activity['reply-to-uri']])) {
+                       logger('Parent ' . $activity['reply-to-uri'] . ' not found. Try to refetch it.');
+                       self::fetchMissingActivity($activity['reply-to-uri'], $activity);
+               }
+
                self::postItem($activity, $item, $body);
        }
 
@@ -1075,7 +1261,7 @@ class ActivityPub
 
                $item = self::constructAttachList($activity['attachments'], $item);
 
-               $source = self::processElement($activity, 'source', 'content', 'mediaType', 'text/bbcode');
+               $source = JsonLD::fetchElement($activity, 'source', 'content', 'mediaType', 'text/bbcode');
                if (!empty($source)) {
                        $item['body'] = $source;
                }
@@ -1094,19 +1280,49 @@ class ActivityPub
 
                        $item_id = Item::insert($item);
                        logger('Storing for user ' . $item['uid'] . ': ' . $item_id);
-                       if (!empty($item_id) && ($item['uid'] == 0)) {
-                               Item::distribute($item_id);
-                       }
+               }
+       }
+
+       private static function fetchMissingActivity($url, $child)
+       {
+               $object = ActivityPub::fetchContent($url);
+               if (empty($object)) {
+                       logger('Activity ' . $url . ' was not fetchable, aborting.');
+                       return;
+               }
+
+               $activity = [];
+               $activity['@context'] = $object['@context'];
+               unset($object['@context']);
+               $activity['id'] = $object['id'];
+               $activity['to'] = defaults($object, 'to', []);
+               $activity['cc'] = defaults($object, 'cc', []);
+               $activity['actor'] = $child['author'];
+               $activity['object'] = $object;
+               $activity['published'] = $object['published'];
+               $activity['type'] = 'Create';
+
+               self::processActivity($activity);
+               logger('Activity ' . $url . ' had been fetched and processed.');
+       }
+
+       private static function getUserOfObject($object)
+       {
+               $self = DBA::selectFirst('contact', ['uid'], ['nurl' => normalise_link($object), 'self' => true]);
+               if (!DBA::isResult($self)) {
+                       return false;
+               } else {
+                       return $self['uid'];
                }
        }
 
        private static function followUser($activity)
        {
-               if (empty($activity['receiver'][$activity['object']])) {
+               $uid = self::getUserOfObject($activity['object']);
+               if (empty($uid)) {
                        return;
                }
 
-               $uid = $activity['receiver'][$activity['object']];
                $owner = User::getOwnerDataById($uid);
 
                $cid = Contact::getIdForURL($activity['owner'], $uid);
@@ -1136,11 +1352,11 @@ class ActivityPub
 
        private static function acceptFollowUser($activity)
        {
-               if (empty($activity['receiver'][$activity['object']])) {
+               $uid = self::getUserOfObject($activity['object']);
+               if (empty($uid)) {
                        return;
                }
 
-               $uid = $activity['receiver'][$activity['object']];
                $owner = User::getOwnerDataById($uid);
 
                $cid = Contact::getIdForURL($activity['owner'], $uid);
@@ -1150,18 +1366,24 @@ class ActivityPub
                }
 
                $fields = ['pending' => false];
-               $condition = ['id' => $cid, 'pending' => true];
-               DBA::update('comtact', $fields, $condition);
+
+               $contact = DBA::selectFirst('contact', ['rel'], ['id' => $cid]);
+               if ($contact['rel'] == Contact::FOLLOWER) {
+                       $fields['rel'] = Contact::FRIEND;
+               }
+
+               $condition = ['id' => $cid];
+               DBA::update('contact', $fields, $condition);
                logger('Accept contact request from contact ' . $cid . ' for user ' . $uid, LOGGER_DEBUG);
        }
 
        private static function undoFollowUser($activity)
        {
-               if (empty($activity['receiver'][$activity['object']])) {
+               $uid = self::getUserOfObject($activity['object']);
+               if (empty($uid)) {
                        return;
                }
 
-               $uid = $activity['receiver'][$activity['object']];
                $owner = User::getOwnerDataById($uid);
 
                $cid = Contact::getIdForURL($activity['owner'], $uid);