]> git.mxchange.org Git - friendica.git/blobdiff - src/Protocol/ActivityPub/Transmitter.php
The "summary" field seems to be interpreted as plain text only
[friendica.git] / src / Protocol / ActivityPub / Transmitter.php
index 47478c3cf72d5ee833046363b9b5961b4c8c5bc6..ce23e6db209910d7530ccb1376ffe58132d66ac1 100644 (file)
@@ -5,7 +5,9 @@
 namespace Friendica\Protocol\ActivityPub;
 
 use Friendica\BaseObject;
+use Friendica\Content\Feature;
 use Friendica\Database\DBA;
+use Friendica\Core\Config;
 use Friendica\Core\Logger;
 use Friendica\Core\System;
 use Friendica\Util\HTTPSignature;
@@ -18,18 +20,18 @@ use Friendica\Model\Term;
 use Friendica\Model\User;
 use Friendica\Util\DateTimeFormat;
 use Friendica\Content\Text\BBCode;
+use Friendica\Content\Text\Plaintext;
 use Friendica\Util\JsonLD;
 use Friendica\Util\LDSignature;
 use Friendica\Model\Profile;
-use Friendica\Core\Config;
 use Friendica\Object\Image;
 use Friendica\Protocol\ActivityPub;
-use Friendica\Protocol\Diaspora;
 use Friendica\Core\Cache;
 use Friendica\Util\Map;
 use Friendica\Util\Network;
 
 require_once 'include/api.php';
+require_once 'mod/share.php';
 
 /**
  * @brief ActivityPub Transmitter Protocol class
@@ -42,10 +44,11 @@ class Transmitter
        /**
         * collects the lost of followers of the given owner
         *
-        * @param array $owner Owner array
-        * @param integer $page Page number
+        * @param array   $owner Owner array
+        * @param integer $page  Page number
         *
         * @return array of owners
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         */
        public static function getFollowers($owner, $page = null)
        {
@@ -89,10 +92,11 @@ class Transmitter
        /**
         * Create list of following contacts
         *
-        * @param array $owner Owner array
-        * @param integer $page Page numbe
+        * @param array   $owner Owner array
+        * @param integer $page  Page numbe
         *
         * @return array of following contacts
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         */
        public static function getFollowing($owner, $page = null)
        {
@@ -136,10 +140,12 @@ class Transmitter
        /**
         * Public posts for the given owner
         *
-        * @param array $owner Owner array
-        * @param integer $page Page numbe
+        * @param array   $owner Owner array
+        * @param integer $page  Page numbe
         *
         * @return array of posts
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
        public static function getOutbox($owner, $page = null)
        {
@@ -147,7 +153,7 @@ class Transmitter
 
                $condition = ['uid' => 0, 'contact-id' => $public_contact, 'author-id' => $public_contact,
                        'private' => false, 'gravity' => [GRAVITY_PARENT, GRAVITY_COMMENT],
-                       'deleted' => false, 'visible' => true];
+                       'deleted' => false, 'visible' => true, 'moderated' => false];
                $count = DBA::count('item', $condition);
 
                $data = ['@context' => ActivityPub::CONTEXT];
@@ -186,6 +192,7 @@ class Transmitter
         *
         * @param integer $uid User ID
         * @return array with profile data
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         */
        public static function getProfile($uid)
        {
@@ -228,7 +235,7 @@ class Transmitter
                        'vcard:region' => $profile['region'], 'vcard:locality' => $profile['locality']];
                $data['summary'] = $contact['about'];
                $data['url'] = $contact['url'];
-               $data['manuallyApprovesFollowers'] = in_array($user['page-flags'], [Contact::PAGE_NORMAL, Contact::PAGE_PRVGROUP]);
+               $data['manuallyApprovesFollowers'] = in_array($user['page-flags'], [User::PAGE_FLAGS_NORMAL, User::PAGE_FLAGS_PRVGROUP]);
                $data['publicKey'] = ['id' => $contact['url'] . '#main-key',
                        'owner' => $contact['url'],
                        'publicKeyPem' => $user['pubkey']];
@@ -246,6 +253,8 @@ class Transmitter
         * @param array $item
         *
         * @return array with permissions
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
        private static function fetchPermissionBlockFromConversation($item)
        {
@@ -295,32 +304,53 @@ class Transmitter
        /**
         * Creates an array of permissions from an item thread
         *
-        * @param array $item
-        * @param boolean $blindcopy
+        * @param array   $item       Item array
+        * @param boolean $blindcopy  addressing via "bcc" or "cc"?
+        * @param integer $last_id    Last item id for adding receivers
+        * @param boolean $forum_mode "true" means that we are sending content to a forum
         *
         * @return array with permission data
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
-       private static function createPermissionBlockForItem($item, $blindcopy)
+       private static function createPermissionBlockForItem($item, $blindcopy, $last_id = 0, $forum_mode = false)
        {
-               // Will be activated in a later step
-               // $networks = [Protocol::ACTIVITYPUB, Protocol::DFRN, Protocol::DIASPORA, Protocol::OSTATUS];
+               if ($last_id == 0) {
+                       $last_id = $item['id'];
+               }
+
+               $always_bcc = false;
+
+               // Check if we should always deliver our stuff via BCC
+               if (!empty($item['uid'])) {
+                       $profile = Profile::getByUID($item['uid']);
+                       if (!empty($profile)) {
+                               $always_bcc = $profile['hide-friends'];
+                       }
+               }
 
-               // For now only send to these contacts:
-               $networks = [Protocol::ACTIVITYPUB, Protocol::OSTATUS];
+               if (Config::get('debug', 'total_ap_delivery')) {
+                       // Will be activated in a later step
+                       $networks = [Protocol::ACTIVITYPUB, Protocol::DFRN, Protocol::DIASPORA, Protocol::OSTATUS];
+               } else {
+                       // For now only send to these contacts:
+                       $networks = [Protocol::ACTIVITYPUB, Protocol::OSTATUS];
+               }
 
                $data = ['to' => [], 'cc' => [], 'bcc' => []];
 
-               $actor_profile = APContact::getByURL($item['author-link']);
+               if ($item['gravity'] == GRAVITY_PARENT) {
+                       $actor_profile = APContact::getByURL($item['owner-link']);
+               } else {
+                       $actor_profile = APContact::getByURL($item['author-link']);
+               }
 
-               $terms = Term::tagArrayFromItemId($item['id'], TERM_MENTION);
+               $terms = Term::tagArrayFromItemId($item['id'], [Term::MENTION, Term::IMPLICIT_MENTION]);
 
                if (!$item['private']) {
                        $data = array_merge($data, self::fetchPermissionBlockFromConversation($item));
 
                        $data['to'][] = ActivityPub::PUBLIC_COLLECTION;
-                       if (!empty($actor_profile['followers'])) {
-                               $data['cc'][] = $actor_profile['followers'];
-                       }
 
                        foreach ($terms as $term) {
                                $profile = APContact::getByURL($term['url'], false);
@@ -331,8 +361,6 @@ class Transmitter
                } else {
                        $receiver_list = Item::enumeratePermissions($item);
 
-                       $mentioned = [];
-
                        foreach ($terms as $term) {
                                $cid = Contact::getIdForURL($term['url'], $item['uid']);
                                if (!empty($cid) && in_array($cid, $receiver_list)) {
@@ -344,39 +372,55 @@ class Transmitter
                        }
 
                        foreach ($receiver_list as $receiver) {
-                               $contact = DBA::selectFirst('contact', ['url'], ['id' => $receiver, 'network' => $networks]);
+                               $contact = DBA::selectFirst('contact', ['url', 'hidden'], ['id' => $receiver, 'network' => $networks]);
                                if (DBA::isResult($contact) && !empty($profile = APContact::getByURL($contact['url'], false))) {
-                                       // BCC is currently deactivated, due to Pleroma and Mastodon not reacting like expected
-                                       // $data['bcc'][] = $profile['url'];
-                                       $data['cc'][] = $profile['url'];
+                                       if ($contact['hidden'] || $always_bcc) {
+                                               $data['bcc'][] = $profile['url'];
+                                       } else {
+                                               $data['cc'][] = $profile['url'];
+                                       }
                                }
                        }
                }
 
                $parents = Item::select(['id', 'author-link', 'owner-link', 'gravity', 'uri'], ['parent' => $item['parent']]);
                while ($parent = Item::fetch($parents)) {
+                       if ($parent['gravity'] == GRAVITY_PARENT) {
+                               $profile = APContact::getByURL($parent['owner-link'], false);
+                               if (!empty($profile)) {
+                                       if ($item['gravity'] != GRAVITY_PARENT) {
+                                               // Comments to forums are directed to the forum
+                                               // But comments to forums aren't directed to the followers collection
+                                               if ($profile['type'] == 'Group') {
+                                                       $data['to'][] = $profile['url'];
+                                               } else {
+                                                       $data['cc'][] = $profile['url'];
+                                                       if (!$item['private']) {
+                                                               $data['cc'][] = $actor_profile['followers'];
+                                                       }
+                                               }
+                                       } else {
+                                               // Public thread parent post always are directed to the followes
+                                               if (!$item['private'] && !$forum_mode) {
+                                                       $data['cc'][] = $actor_profile['followers'];
+                                               }
+                                       }
+                               }
+                       }
+
                        // Don't include data from future posts
-                       if ($parent['id'] >= $item['id']) {
+                       if ($parent['id'] >= $last_id) {
                                continue;
                        }
 
                        $profile = APContact::getByURL($parent['author-link'], false);
                        if (!empty($profile)) {
-                               if ($parent['uri'] == $item['thr-parent']) {
+                               if (($profile['type'] == 'Group') || ($parent['uri'] == $item['thr-parent'])) {
                                        $data['to'][] = $profile['url'];
                                } else {
                                        $data['cc'][] = $profile['url'];
                                }
                        }
-
-                       if ($item['gravity'] != GRAVITY_PARENT) {
-                               continue;
-                       }
-
-                       $profile = APContact::getByURL($parent['owner-link'], false);
-                       if (!empty($profile)) {
-                               $data['cc'][] = $profile['url'];
-                       }
                }
                DBA::close($parents);
 
@@ -424,20 +468,24 @@ class Transmitter
        /**
         * Fetches a list of inboxes of followers of a given user
         *
-        * @param integer $uid User ID
+        * @param integer $uid      User ID
         * @param boolean $personal fetch personal inboxes
         *
         * @return array of follower inboxes
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
        public static function fetchTargetInboxesforUser($uid, $personal = false)
        {
                $inboxes = [];
 
-               // Will be activated in a later step
-               // $networks = [Protocol::ACTIVITYPUB, Protocol::DFRN, Protocol::DIASPORA, Protocol::OSTATUS];
-
-               // For now only send to these contacts:
-               $networks = [Protocol::ACTIVITYPUB, Protocol::OSTATUS];
+               if (Config::get('debug', 'total_ap_delivery')) {
+                       // Will be activated in a later step
+                       $networks = [Protocol::ACTIVITYPUB, Protocol::DFRN, Protocol::DIASPORA, Protocol::OSTATUS];
+               } else {
+                       // For now only send to these contacts:
+                       $networks = [Protocol::ACTIVITYPUB, Protocol::OSTATUS];
+               }
 
                $condition = ['uid' => $uid, 'network' => $networks, 'archive' => false, 'pending' => false];
 
@@ -469,15 +517,18 @@ class Transmitter
        /**
         * Fetches an array of inboxes for the given item and user
         *
-        * @param array $item
-        * @param integer $uid User ID
-        * @param boolean $personal fetch personal inboxes
-        *
+        * @param array   $item       Item array
+        * @param integer $uid        User ID
+        * @param boolean $personal   fetch personal inboxes
+        * @param integer $last_id    Last item id for adding receivers
+        * @param boolean $forum_mode "true" means that we are sending content to a forum
         * @return array with inboxes
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
-       public static function fetchTargetInboxes($item, $uid, $personal = false)
+       public static function fetchTargetInboxes($item, $uid, $personal = false, $last_id = 0, $forum_mode = false)
        {
-               $permissions = self::createPermissionBlockForItem($item, true);
+               $permissions = self::createPermissionBlockForItem($item, true, $last_id, $forum_mode);
                if (empty($permissions)) {
                        return [];
                }
@@ -527,10 +578,20 @@ class Transmitter
         * @param array $item
         *
         * @return string with activity type
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
        private static function getTypeOfItem($item)
        {
-               if (!empty(Diaspora::isReshare($item['body'], false))) {
+               $reshared = false;
+
+               // Only check for a reshare, if it is a real reshare and no quoted reshare
+               if (strpos($item['body'], "[share") === 0) {
+                       $announce = api_share_as_retweet($item);
+                       $reshared = !empty($announce['plink']);
+               }
+
+               if ($reshared) {
                        $type = 'Announce';
                } elseif ($item['verb'] == ACTIVITY_POST) {
                        if ($item['created'] == $item['edited']) {
@@ -548,6 +609,8 @@ class Transmitter
                        $type = 'Reject';
                } elseif ($item['verb'] == ACTIVITY_ATTENDMAYBE) {
                        $type = 'TentativeAccept';
+               } elseif ($item['verb'] == ACTIVITY_FOLLOW) {
+                       $type = 'Follow';
                } else {
                        $type = '';
                }
@@ -559,9 +622,10 @@ class Transmitter
         * Creates the activity or fetches it from the cache
         *
         * @param integer $item_id
-        * @param boolean $force   Force new cache entry
+        * @param boolean $force Force new cache entry
         *
         * @return array with the activity
+        * @throws \Exception
         */
        public static function createCachedActivityFromItem($item_id, $force = false)
        {
@@ -587,6 +651,7 @@ class Transmitter
         * @param boolean $object_mode Is the activity item is used inside another object?
         *
         * @return array of activity
+        * @throws \Exception
         */
        public static function createActivityFromItem($item_id, $object_mode = false)
        {
@@ -596,16 +661,29 @@ class Transmitter
                        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 $data;
+               if ($item['wall'] && ($item['uri'] == $item['parent-uri'])) {
+                       $owner = User::getOwnerDataById($item['uid']);
+                       if (($owner['account-type'] == User::ACCOUNT_TYPE_COMMUNITY) && ($item['author-link'] != $owner['url'])) {
+                               $type = 'Announce';
+
+                               // Disguise forum posts as reshares. Will later be converted to a real announce
+                               $item['body'] = share_header($item['author-name'], $item['author-link'], $item['author-avatar'],
+                                       $item['guid'], $item['created'], $item['plink']) . $item['body'] . '[/share]';
                        }
                }
 
-               $type = self::getTypeOfItem($item);
+               if (empty($type)) {
+                       $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;
+                               }
+                       }
+
+                       $type = self::getTypeOfItem($item);
+               }
 
                if (!$object_mode) {
                        $data = ['@context' => ActivityPub::CONTEXT];
@@ -621,7 +699,12 @@ class Transmitter
 
                $data['id'] = $item['uri'] . '#' . $type;
                $data['type'] = $type;
-               $data['actor'] = $item['owner-link'];
+
+               if (Item::isForumPost($item) && ($type != 'Announce')) {
+                       $data['actor'] = $item['author-link'];
+               } else {
+                       $data['actor'] = $item['owner-link'];
+               }
 
                $data['published'] = DateTimeFormat::utc($item['created'] . '+00:00', DateTimeFormat::ATOM);
 
@@ -632,7 +715,9 @@ class Transmitter
                if (in_array($data['type'], ['Create', 'Update', 'Delete'])) {
                        $data['object'] = self::createNote($item);
                } elseif ($data['type'] == 'Announce') {
-                       $data['object'] = self::createAnnounce($item);
+                       $data = self::createAnnounce($item, $data);
+               } elseif ($data['type'] == 'Follow') {
+                       $data['object'] = $item['parent-uri'];
                } elseif ($data['type'] == 'Undo') {
                        $data['object'] = self::createActivityFromItem($item_id, true);
                } else {
@@ -643,9 +728,15 @@ class Transmitter
                        $data['object'] = $item['thr-parent'];
                }
 
-               $owner = User::getOwnerDataById($item['contact-uid']);
+               if (!empty($item['contact-uid'])) {
+                       $uid = $item['contact-uid'];
+               } else {
+                       $uid = $item['uid'];
+               }
 
-               if (!$object_mode) {
+               $owner = User::getOwnerDataById($uid);
+
+               if (!$object_mode && !empty($owner)) {
                        return LDSignature::sign($data, $owner);
                } else {
                        return $data;
@@ -660,6 +751,8 @@ class Transmitter
         * @param integer $item_id
         *
         * @return array with the object data
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
        public static function createObjectFromItemID($item_id)
        {
@@ -715,16 +808,18 @@ class Transmitter
         * @param array $item
         *
         * @return array of tags
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         */
        private static function createTagList($item)
        {
                $tags = [];
 
-               $terms = Term::tagArrayFromItemId($item['id']);
+               $terms = Term::tagArrayFromItemId($item['id'], [Term::HASHTAG, Term::MENTION, Term::IMPLICIT_MENTION]);
                foreach ($terms as $term) {
-                       if ($term['type'] == TERM_HASHTAG) {
-                               $tags[] = ['type' => 'Hashtag', 'href' => $term['url'], 'name' => '#' . $term['term']];
-                       } elseif ($term['type'] == TERM_MENTION) {
+                       if ($term['type'] == Term::HASHTAG) {
+                               $url = System::baseUrl() . '/search?tag=' . urlencode($term['term']);
+                               $tags[] = ['type' => 'Hashtag', 'href' => $url, 'name' => '#' . $term['term']];
+                       } elseif ($term['type'] == Term::MENTION || $term['type'] == Term::IMPLICIT_MENTION) {
                                $contact = Contact::getDetailsByURL($term['url']);
                                if (!empty($contact['addr'])) {
                                        $mention = '@' . $contact['addr'];
@@ -741,10 +836,11 @@ class Transmitter
        /**
         * Adds attachment data to the JSON document
         *
-        * @param array $item Data of the item that is to be posted
-        * @param text $type Object type
+        * @param array  $item Data of the item that is to be posted
+        * @param string $type Object type
         *
         * @return array with attachment data
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         */
        private static function createAttachmentList($item, $type)
        {
@@ -793,21 +889,22 @@ class Transmitter
                return $attachments;
        }
 
-        /**
+       /**
         * @brief Callback function to replace a Friendica style mention in a mention that is used on AP
         *
         * @param array $match Matching values for the callback
         * @return string Replaced mention
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         */
        private static function mentionCallback($match)
        {
                if (empty($match[1])) {
-                       return;
+                       return '';
                }
 
                $data = Contact::getDetailsByURL($match[1]);
-               if (empty($data) || empty($data['nick'])) {
-                       return;
+               if (empty($data['nick'])) {
+                       return $match[0];
                }
 
                return '@[url=' . $data['url'] . ']' . $data['nick'] . '[/url]';
@@ -837,6 +934,7 @@ class Transmitter
         * @param array $item
         *
         * @return string with context url
+        * @throws \Exception
         */
        private static function fetchContextURLForItem($item)
        {
@@ -857,6 +955,7 @@ class Transmitter
         * @param integer $item_id
         *
         * @return boolean
+        * @throws \Exception
         */
        private static function isSensitive($item_id)
        {
@@ -870,6 +969,7 @@ class Transmitter
         * @param array $item
         *
         * @return array with the event data
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         */
        public static function createEvent($item)
        {
@@ -896,6 +996,8 @@ class Transmitter
         * @param array $item
         *
         * @return array with the object data
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
        public static function createNote($item)
        {
@@ -919,7 +1021,7 @@ class Transmitter
                        return $data;
                }
 
-               $data['summary'] = null; // Ignore by now
+               $data['summary'] = BBCode::toPlaintext(BBCode::getAbstract($item['body'], Protocol::ACTIVITYPUB));
 
                if ($item['uri'] != $item['thr-parent']) {
                        $data['inReplyTo'] = $item['thr-parent'];
@@ -943,10 +1045,18 @@ class Transmitter
                        $data['name'] = BBCode::toPlaintext($item['title'], false);
                }
 
+               $permission_block = self::createPermissionBlockForItem($item, false);
+
                $body = $item['body'];
 
+               if (empty($item['uid']) || !Feature::isEnabled($item['uid'], 'explicit_mentions')) {
+                       $body = self::prependMentions($body, $permission_block);
+               }
+
                if ($type == 'Note') {
                        $body = self::removePictures($body);
+               } elseif (($type == 'Article') && empty($data['summary'])) {
+                       $data['summary'] = BBCode::toPlaintext(Plaintext::shorten(self::removePictures($body), 1000));
                }
 
                if ($type == 'Event') {
@@ -975,7 +1085,7 @@ class Transmitter
                        $data['generator'] = ['type' => 'Application', 'name' => $item['app']];
                }
 
-               $data = array_merge($data, self::createPermissionBlockForItem($item, false));
+               $data = array_merge($data, $permission_block);
 
                return $data;
        }
@@ -984,17 +1094,35 @@ class Transmitter
         * Creates an announce object entry
         *
         * @param array $item
+        * @param array $data activity data
         *
-        * @return string with announced object url
+        * @return array with activity data
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
-       public static function createAnnounce($item)
+       private static function createAnnounce($item, $data)
        {
                $announce = api_share_as_retweet($item);
                if (empty($announce['plink'])) {
-                       return self::createNote($item);
+                       $data['type'] = 'Create';
+                       $data['object'] = self::createNote($item);
+                       return $data;
                }
 
-               return $announce['plink'];
+               // Fetch the original id of the object
+               $activity = ActivityPub::fetchContent($announce['plink'], $item['uid']);
+               if (!empty($activity)) {
+                       $ldactivity = JsonLD::compact($activity);
+                       $id = JsonLD::fetchElement($ldactivity, '@id');
+                       if (!empty($id)) {
+                               $data['object'] = $id;
+                               return $data;
+                       }
+               }
+
+               $data['type'] = 'Create';
+               $data['object'] = self::createNote($item);
+               return $data;
        }
 
        /**
@@ -1019,11 +1147,12 @@ class Transmitter
        /**
         * Transmits a contact suggestion to a given inbox
         *
-        * @param integer $uid User ID
-        * @param string $inbox Target inbox
+        * @param integer $uid           User ID
+        * @param string  $inbox         Target inbox
         * @param integer $suggestion_id Suggestion ID
         *
         * @return boolean was the transmission successful?
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         */
        public static function sendContactSuggestion($uid, $inbox, $suggestion_id)
        {
@@ -1050,10 +1179,11 @@ class Transmitter
        /**
         * Transmits a profile relocation to a given inbox
         *
-        * @param integer $uid User ID
-        * @param string $inbox Target inbox
+        * @param integer $uid   User ID
+        * @param string  $inbox Target inbox
         *
         * @return boolean was the transmission successful?
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         */
        public static function sendProfileRelocation($uid, $inbox)
        {
@@ -1078,15 +1208,26 @@ class Transmitter
        /**
         * Transmits a profile deletion to a given inbox
         *
-        * @param integer $uid User ID
-        * @param string $inbox Target inbox
+        * @param integer $uid   User ID
+        * @param string  $inbox Target inbox
         *
         * @return boolean was the transmission successful?
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         */
        public static function sendProfileDeletion($uid, $inbox)
        {
                $owner = User::getOwnerDataById($uid);
 
+               if (empty($owner)) {
+                       Logger::error('No owner data found, the deletion message cannot be processed.', ['user' => $uid]);
+                       return false;
+               }
+
+               if (empty($owner['uprvkey'])) {
+                       Logger::error('No private key for owner found, the deletion message cannot be processed.', ['user' => $uid]);
+                       return false;
+               }
+
                $data = ['@context' => ActivityPub::CONTEXT,
                        'id' => System::baseUrl() . '/activity/' . System::createGUID(),
                        'type' => 'Delete',
@@ -1106,10 +1247,12 @@ class Transmitter
        /**
         * Transmits a profile change to a given inbox
         *
-        * @param integer $uid User ID
-        * @param string $inbox Target inbox
+        * @param integer $uid   User ID
+        * @param string  $inbox Target inbox
         *
         * @return boolean was the transmission successful?
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
        public static function sendProfileUpdate($uid, $inbox)
        {
@@ -1135,10 +1278,13 @@ class Transmitter
        /**
         * Transmits a given activity to a target
         *
-        * @param array $activity
-        * @param string $target Target profile
-        * @param integer $uid User ID
-        * @param string $id activity id
+        * @param string  $activity Type name
+        * @param string  $target   Target profile
+        * @param integer $uid      User ID
+        * @return bool
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
+        * @throws \Exception
         */
        public static function sendActivity($activity, $target, $uid, $id = '')
        {
@@ -1156,20 +1302,71 @@ class Transmitter
                        'actor' => $owner['url'],
                        'object' => $profile['url'],
                        'instrument' => ['type' => 'Service', 'name' => BaseObject::getApp()->getUserAgent()],
-                       'to' => $profile['url']];
+                       'to' => [$profile['url']]];
 
                Logger::log('Sending activity ' . $activity . ' to ' . $target . ' for user ' . $uid, Logger::DEBUG);
 
                $signed = LDSignature::sign($data, $owner);
-               HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+               return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+       }
+
+       /**
+        * Transmits a "follow object" activity to a target
+        * This is a preparation for sending automated "follow" requests when receiving "Announce" messages
+        *
+        * @param string  $object Object URL
+        * @param string  $target Target profile
+        * @param integer $uid    User ID
+        * @return bool
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
+        * @throws \Exception
+        */
+       public static function sendFollowObject($object, $target, $uid = 0)
+       {
+               $profile = APContact::getByURL($target);
+
+               if (empty($uid)) {
+                       // Fetch the list of administrators
+                       $admin_mail = explode(',', str_replace(' ', '', Config::get('config', 'admin_email')));
+
+                       // We need to use some user as a sender. It doesn't care who it will send. We will use an administrator account.
+                       $condition = ['verified' => true, 'blocked' => false, 'account_removed' => false, 'account_expired' => false, 'email' => $admin_mail];
+                       $first_user = DBA::selectFirst('user', ['uid'], $condition);
+                       $uid = $first_user['uid'];
+               }
+
+               $condition = ['verb' => ACTIVITY_FOLLOW, 'uid' => 0, 'parent-uri' => $object,
+                       'author-id' => Contact::getPublicIdByUserId($uid)];
+               if (Item::exists($condition)) {
+                       Logger::log('Follow for ' . $object . ' for user ' . $uid . ' does already exist.', Logger::DEBUG);
+                       return false;
+               }
+
+               $owner = User::getOwnerDataById($uid);
+
+               $data = ['@context' => ActivityPub::CONTEXT,
+                       'id' => System::baseUrl() . '/activity/' . System::createGUID(),
+                       'type' => 'Follow',
+                       'actor' => $owner['url'],
+                       'object' => $object,
+                       'instrument' => ['type' => 'Service', 'name' => BaseObject::getApp()->getUserAgent()],
+                       'to' => [$profile['url']]];
+
+               Logger::log('Sending follow ' . $object . ' to ' . $target . ' for user ' . $uid, Logger::DEBUG);
+
+               $signed = LDSignature::sign($data, $owner);
+               return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
        }
 
        /**
         * Transmit a message that the contact request had been accepted
         *
-        * @param string $target Target profile
-        * @param $id
-        * @param integer $uid User ID
+        * @param string  $target Target profile
+        * @param         $id
+        * @param integer $uid    User ID
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
        public static function sendContactAccept($target, $id, $uid)
        {
@@ -1184,7 +1381,7 @@ class Transmitter
                                'actor' => $profile['url'],
                                'object' => $owner['url']],
                        'instrument' => ['type' => 'Service', 'name' => BaseObject::getApp()->getUserAgent()],
-                       'to' => $profile['url']];
+                       'to' => [$profile['url']]];
 
                Logger::log('Sending accept to ' . $target . ' for user ' . $uid . ' with id ' . $id, Logger::DEBUG);
 
@@ -1195,9 +1392,11 @@ class Transmitter
        /**
         * Reject a contact request or terminates the contact relation
         *
-        * @param string $target Target profile
-        * @param $id
-        * @param integer $uid User ID
+        * @param string  $target Target profile
+        * @param         $id
+        * @param integer $uid    User ID
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
        public static function sendContactReject($target, $id, $uid)
        {
@@ -1212,7 +1411,7 @@ class Transmitter
                                'actor' => $profile['url'],
                                'object' => $owner['url']],
                        'instrument' => ['type' => 'Service', 'name' => BaseObject::getApp()->getUserAgent()],
-                       'to' => $profile['url']];
+                       'to' => [$profile['url']]];
 
                Logger::log('Sending reject to ' . $target . ' for user ' . $uid . ' with id ' . $id, Logger::DEBUG);
 
@@ -1223,9 +1422,11 @@ class Transmitter
        /**
         * Transmits a message that we don't want to follow this contact anymore
         *
-        * @param string $target Target profile
-        * @param integer $cid Contact ID of target
-        * @param integer $uid User ID
+        * @param string  $target Target profile
+        * @param integer $uid    User ID
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
+        * @throws \Exception
         */
        public static function sendContactUndo($target, $cid, $uid)
        {
@@ -1247,11 +1448,35 @@ class Transmitter
                                'actor' => $owner['url'],
                                'object' => $profile['url']],
                        'instrument' => ['type' => 'Service', 'name' => BaseObject::getApp()->getUserAgent()],
-                       'to' => $profile['url']];
+                       'to' => [$profile['url']]];
 
                Logger::log('Sending undo to ' . $target . ' for user ' . $uid . ' with id ' . $id, Logger::DEBUG);
 
                $signed = LDSignature::sign($data, $owner);
                HTTPSignature::transmit($signed, $profile['inbox'], $uid);
        }
+
+       private static function prependMentions($body, array $permission_block)
+       {
+               if (Config::get('system', 'disable_implicit_mentions')) {
+                       return $body;
+               }
+
+               $mentions = [];
+
+               foreach ($permission_block['to'] as $profile_url) {
+                       $profile = Contact::getDetailsByURL($profile_url);
+                       if (!empty($profile['addr'])
+                               && $profile['contact-type'] != Contact::TYPE_COMMUNITY
+                               && !strstr($body, $profile['addr'])
+                               && !strstr($body, $profile_url)
+                       ) {
+                               $mentions[] = '@[url=' . $profile_url . ']' . $profile['nick'] . '[/url]';
+                       }
+               }
+
+               $mentions[] = $body;
+
+               return implode(' ', $mentions);
+       }
 }