]> git.mxchange.org Git - friendica.git/blobdiff - src/Protocol/ActivityPub.php
Merge pull request #5812 from annando/develop
[friendica.git] / src / Protocol / ActivityPub.php
index 8992c525b0dafb303c8b578a8bc77df01c9b5e46..ef4a48479ea2a4c677704763af81d10272e443a8 100644 (file)
@@ -10,11 +10,20 @@ use Friendica\BaseObject;
 use Friendica\Util\Network;
 use Friendica\Util\HTTPSignature;
 use Friendica\Core\Protocol;
+use Friendica\Model\Conversation;
+use Friendica\Model\Contact;
+use Friendica\Model\APContact;
 use Friendica\Model\Item;
+use Friendica\Model\Profile;
+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\Util\JsonLD;
+use Friendica\Util\LDSignature;
+use Friendica\Core\Config;
 
 /**
  * @brief ActivityPub Protocol class
@@ -28,56 +37,214 @@ use Friendica\Content\Text\BBCode;
  *
  * Digest: https://tools.ietf.org/html/rfc5843
  * https://tools.ietf.org/html/draft-cavage-http-signatures-10#ref-15
+ *
+ * Mastodon implementation of supported activities:
+ * https://github.com/tootsuite/mastodon/blob/master/app/lib/activitypub/activity.rb#L26
+ *
+ * To-do:
+ *
+ * Receiver:
+ * - Update (Image, Video, Article, Note)
+ * - Event
+ * - Undo Announce
+ *
+ * Check what this is meant to do:
+ * - Add
+ * - Block
+ * - Flag
+ * - Remove
+ * - Undo Block
+ * - Undo Accept (Problem: This could invert a contact accept or an event accept)
+ *
+ * Transmitter:
+ * - Event
+ *
+ * Complicated:
+ * - Announce
+ * - Undo Announce
+ *
+ * General:
+ * - Attachments
+ * - nsfw (sensitive)
+ * - Queueing unsucessful deliveries
+ * - Polling the outboxes for missing content?
+ * - Possibly using the LD-JSON parser
  */
 class ActivityPub
 {
-       const PUBLIC = 'https://www.w3.org/ns/activitystreams#Public';
+       const PUBLIC_COLLECTION = 'https://www.w3.org/ns/activitystreams#Public';
+       const CONTEXT = ['https://www.w3.org/ns/activitystreams', 'https://w3id.org/security/v1',
+               ['vcard' => 'http://www.w3.org/2006/vcard/ns#',
+               'diaspora' => 'https://diasporafoundation.org/ns/',
+               'manuallyApprovesFollowers' => 'as:manuallyApprovesFollowers',
+               'sensitive' => 'as:sensitive', 'Hashtag' => 'as:Hashtag']];
+       const ACCOUNT_TYPES = ['Person', 'Organization', 'Service', 'Group', 'Application'];
+       const CONTENT_TYPES = ['Note', 'Article', 'Video', 'Image'];
+       const ACTIVITY_TYPES = ['Like', 'Dislike', 'Accept', 'Reject', 'TentativeAccept'];
+       /**
+        * @brief Checks if the web request is done for the AP protocol
+        *
+        * @return is it AP?
+        */
+       public static function isRequest()
+       {
+               return stristr(defaults($_SERVER, 'HTTP_ACCEPT', ''), 'application/activity+json') ||
+                       stristr(defaults($_SERVER, 'HTTP_ACCEPT', ''), 'application/ld+json');
+       }
 
-       public static function transmit($content, $target, $uid)
+       /**
+        * @brief collects the lost of followers of the given owner
+        *
+        * @param array $owner Owner array
+        * @param integer $page Page number
+        *
+        * @return array of owners
+        */
+       public static function getFollowers($owner, $page = null)
        {
-               $owner = User::getOwnerDataById($uid);
+               $condition = ['rel' => [Contact::FOLLOWER, Contact::FRIEND], 'network' => Protocol::NATIVE_SUPPORT, 'uid' => $owner['uid'],
+                       'self' => false, 'hidden' => false, 'archive' => false, 'pending' => false];
+               $count = DBA::count('contact', $condition);
+
+               $data = ['@context' => self::CONTEXT];
+               $data['id'] = System::baseUrl() . '/followers/' . $owner['nickname'];
+               $data['type'] = 'OrderedCollection';
+               $data['totalItems'] = $count;
+
+               // When we hide our friends we will only show the pure number but don't allow more.
+               $profile = Profile::getByUID($owner['uid']);
+               if (!empty($profile['hide-friends'])) {
+                       return $data;
+               }
 
-               if (!$owner) {
-                       return;
+               if (empty($page)) {
+                       $data['first'] = System::baseUrl() . '/followers/' . $owner['nickname'] . '?page=1';
+               } else {
+                       $list = [];
+
+                       $contacts = DBA::select('contact', ['url'], $condition, ['limit' => [($page - 1) * 100, 100]]);
+                       while ($contact = DBA::fetch($contacts)) {
+                               $list[] = $contact['url'];
+                       }
+
+                       if (!empty($list)) {
+                               $data['next'] = System::baseUrl() . '/followers/' . $owner['nickname'] . '?page=' . ($page + 1);
+                       }
+
+                       $data['partOf'] = System::baseUrl() . '/followers/' . $owner['nickname'];
+
+                       $data['orderedItems'] = $list;
+               }
+
+               return $data;
+       }
+
+       /**
+        * @brief Create list of following contacts
+        *
+        * @param array $owner Owner array
+        * @param integer $page Page numbe
+        *
+        * @return array of following contacts
+        */
+       public static function getFollowing($owner, $page = null)
+       {
+               $condition = ['rel' => [Contact::SHARING, Contact::FRIEND], 'network' => Protocol::NATIVE_SUPPORT, 'uid' => $owner['uid'],
+                       'self' => false, 'hidden' => false, 'archive' => false, 'pending' => false];
+               $count = DBA::count('contact', $condition);
+
+               $data = ['@context' => self::CONTEXT];
+               $data['id'] = System::baseUrl() . '/following/' . $owner['nickname'];
+               $data['type'] = 'OrderedCollection';
+               $data['totalItems'] = $count;
+
+               // When we hide our friends we will only show the pure number but don't allow more.
+               $profile = Profile::getByUID($owner['uid']);
+               if (!empty($profile['hide-friends'])) {
+                       return $data;
+               }
+
+               if (empty($page)) {
+                       $data['first'] = System::baseUrl() . '/following/' . $owner['nickname'] . '?page=1';
+               } else {
+                       $list = [];
+
+                       $contacts = DBA::select('contact', ['url'], $condition, ['limit' => [($page - 1) * 100, 100]]);
+                       while ($contact = DBA::fetch($contacts)) {
+                               $list[] = $contact['url'];
+                       }
+
+                       if (!empty($list)) {
+                               $data['next'] = System::baseUrl() . '/following/' . $owner['nickname'] . '?page=' . ($page + 1);
+                       }
+
+                       $data['partOf'] = System::baseUrl() . '/following/' . $owner['nickname'];
+
+                       $data['orderedItems'] = $list;
                }
 
-               $host = parse_url($target, PHP_URL_HOST);
-               $path = parse_url($target, PHP_URL_PATH);
-               $date = date('r');
+               return $data;
+       }
+
+       /**
+        * @brief Public posts for the given owner
+        *
+        * @param array $owner Owner array
+        * @param integer $page Page numbe
+        *
+        * @return array of posts
+        */
+       public static function getOutbox($owner, $page = null)
+       {
+               $public_contact = Contact::getIdForURL($owner['url'], 0, true);
+
+               $condition = ['uid' => $owner['uid'], 'contact-id' => $owner['id'], 'author-id' => $public_contact,
+                       'wall' => true, 'private' => false, 'gravity' => [GRAVITY_PARENT, GRAVITY_COMMENT],
+                       'deleted' => false, 'visible' => true];
+               $count = DBA::count('item', $condition);
+
+               $data = ['@context' => self::CONTEXT];
+               $data['id'] = System::baseUrl() . '/outbox/' . $owner['nickname'];
+               $data['type'] = 'OrderedCollection';
+               $data['totalItems'] = $count;
+
+               if (empty($page)) {
+                       $data['first'] = System::baseUrl() . '/outbox/' . $owner['nickname'] . '?page=1';
+               } else {
+                       $list = [];
+
+                       $condition['parent-network'] = Protocol::NATIVE_SUPPORT;
 
-               $headers = ['Host: ' . $host, 'Date: ' . $date];
+                       $items = Item::select(['id'], $condition, ['limit' => [($page - 1) * 20, 20], 'order' => ['created' => true]]);
+                       while ($item = Item::fetch($items)) {
+                               $object = self::createObjectFromItemID($item['id']);
+                               unset($object['@context']);
+                               $list[] = $object;
+                       }
 
-               $signed_data = "(request-target): post " . $path . "\nhost: " . $host . "\ndate: " . $date;
+                       if (!empty($list)) {
+                               $data['next'] = System::baseUrl() . '/outbox/' . $owner['nickname'] . '?page=' . ($page + 1);
+                       }
 
-               $signature = base64_encode(Crypto::rsaSign($signed_data, $owner['uprvkey'], 'sha256'));
+                       $data['partOf'] = System::baseUrl() . '/outbox/' . $owner['nickname'];
 
-               $headers[] = 'Signature: keyId="' . $owner['url'] . '#main-key' . '",headers="(request-target) host date",signature="' . $signature . '"';
-               $headers[] = 'Content-Type: application/activity+json';
-//print_r($headers);
-//die($signed_data);
-//$headers = [];
-//             $headers = HTTPSignature::createSig('', $headers, $owner['uprvkey'], $owner['url'] . '#main-key', false, false, 'sha256');
+                       $data['orderedItems'] = $list;
+               }
 
-               Network::post($target, $content, $headers);
-               $return_code = BaseObject::getApp()->get_curl_code();
-echo $return_code."\n";
-               print_r(BaseObject::getApp()->get_curl_headers());
-               print_r($headers);
+               return $data;
        }
 
        /**
         * Return the ActivityPub profile of the given user
         *
         * @param integer $uid User ID
-        * @return array
+        * @return profile array
         */
        public static function profile($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 [];
@@ -95,24 +262,21 @@ echo $return_code."\n";
                        return [];
                }
 
-               $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#']]];
-
+               $data = ['@context' => self::CONTEXT];
                $data['id'] = $contact['url'];
-               $data['uuid'] = $user['guid'];
-               $data['type'] = $accounttype[$user['account-type']];
+               $data['diaspora:guid'] = $user['guid'];
+               $data['type'] = self::ACCOUNT_TYPES[$user['account-type']];
                $data['following'] = System::baseUrl() . '/following/' . $user['nickname'];
                $data['followers'] = System::baseUrl() . '/followers/' . $user['nickname'];
                $data['inbox'] = System::baseUrl() . '/inbox/' . $user['nickname'];
                $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']];
@@ -124,652 +288,1657 @@ echo $return_code."\n";
                return $data;
        }
 
-       public static function createActivityFromItem($item_id)
+       /**
+        * @brief Returns an array with permissions of a given item array
+        *
+        * @param array $item
+        *
+        * @return array with permissions
+        */
+       private static function fetchPermissionBlockFromConversation($item)
        {
-               $item = Item::selectFirst([], ['id' => $item_id]);
+               if (empty($item['thr-parent'])) {
+                       return [];
+               }
 
-               $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#']]];
+               $condition = ['item-uri' => $item['thr-parent'], 'protocol' => Conversation::PARCEL_ACTIVITYPUB];
+               $conversation = DBA::selectFirst('conversation', ['source'], $condition);
+               if (!DBA::isResult($conversation)) {
+                       return [];
+               }
 
-               $data['type'] = 'Create';
-               $data['id'] = $item['plink'];
-               $data['actor'] = $item['author-link'];
-               $data['to'] = 'https://www.w3.org/ns/activitystreams#Public';
-               $data['object'] = self::createNote($item);
-//             print_r($data);
-//             print_r($item);
-               return $data;
-       }
+               $activity = json_decode($conversation['source'], true);
 
-       public static function createNote($item)
-       {
-               $data = [];
-               $data['type'] = 'Note';
-               $data['id'] = $item['plink'];
-               //$data['context'] = $data['conversation'] = $item['parent-uri'];
-               $data['actor'] = $item['author-link'];
-//             if (!$item['private']) {
-//                     $data['to'] = [];
-//                     $data['to'][] = '"https://pleroma.soykaf.com/users/heluecht"';
-                       $data['to'] = 'https://www.w3.org/ns/activitystreams#Public';
-//                     $data['cc'] = 'https://pleroma.soykaf.com/users/heluecht';
-//             }
-               $data['published'] = DateTimeFormat::utc($item["created"]."+00:00", DateTimeFormat::ATOM);
-               $data['updated'] = DateTimeFormat::utc($item["edited"]."+00:00", DateTimeFormat::ATOM);
-               $data['attributedTo'] = $item['author-link'];
-               $data['title'] = BBCode::convert($item['title'], false, 7);
-               $data['content'] = BBCode::convert($item['body'], false, 7);
-               //$data['summary'] = '';
-               //$data['sensitive'] = false;
-               //$data['emoji'] = [];
-               //$data['tag'] = [];
-               //$data['attachment'] = [];
-               return $data;
+               $actor = JsonLD::fetchElement($activity, 'actor', 'id');
+               $profile = APContact::getByURL($actor);
+
+               $item_profile = APContact::getByURL($item['author-link']);
+               $exclude[] = $item['author-link'];
+
+               if ($item['gravity'] == GRAVITY_PARENT) {
+                       $exclude[] = $item['owner-link'];
+               }
+
+               $permissions['to'][] = $actor;
+
+               foreach (['to', 'cc', 'bto', 'bcc'] 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 = $item_profile['followers'];
+                               }
+                               if (!in_array($receiver, $exclude)) {
+                                       $permissions[$element][] = $receiver;
+                               }
+                       }
+               }
+               return $permissions;
        }
 
        /**
-        * Fetches ActivityPub content from the given url
+        * @brief Creates an array of permissions from an item thread
         *
-        * @param string $url content url
-        * @return array
+        * @param array $item
+        *
+        * @return permission array
         */
-       public static function fetchContent($url)
+       public static function createPermissionBlockForItem($item)
        {
-               $ret = Network::curl($url, false, $redirects, ['accept_content' => 'application/activity+json']);
+               $data = ['to' => [], 'cc' => []];
 
-               if (!$ret['success'] || empty($ret['body'])) {
-                       return;
+               $data = array_merge($data, self::fetchPermissionBlockFromConversation($item));
+
+               $actor_profile = APContact::getByURL($item['author-link']);
+
+               $terms = Term::tagArrayFromItemId($item['id'], TERM_MENTION);
+
+               $contacts[$item['author-link']] = $item['author-link'];
+
+               if (!$item['private']) {
+                       $data['to'][] = self::PUBLIC_COLLECTION;
+                       if (!empty($actor_profile['followers'])) {
+                               $data['cc'][] = $actor_profile['followers'];
+                       }
+
+                       foreach ($terms as $term) {
+                               $profile = APContact::getByURL($term['url'], false);
+                               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) {
+                               $cid = Contact::getIdForURL($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'];
+                               }
+                       }
                }
 
-               return json_decode($ret['body'], true);
+               $parents = Item::select(['id', 'author-link', 'owner-link', 'gravity'], ['parent' => $item['parent']]);
+               while ($parent = Item::fetch($parents)) {
+                       // Don't include data from future posts
+                       if ($parent['id'] >= $item['id']) {
+                               continue;
+                       }
+
+                       $profile = APContact::getByURL($parent['author-link'], false);
+                       if (!empty($profile) && empty($contacts[$profile['url']])) {
+                               $data['cc'][] = $profile['url'];
+                               $contacts[$profile['url']] = $profile['url'];
+                       }
+
+                       if ($item['gravity'] != GRAVITY_PARENT) {
+                               continue;
+                       }
+
+                       $profile = APContact::getByURL($parent['owner-link'], false);
+                       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;
        }
 
        /**
-        * Resolves the profile url from the address by using webfinger
+        * @brief Fetches a list of inboxes of followers of a given user
+        *
+        * @param integer $uid User ID
         *
-        * @param string $addr profile address (user@domain.tld)
-        * @return string url
+        * @return array of follower inboxes
         */
-       private static function addrToUrl($addr)
+       public static function fetchTargetInboxesforUser($uid)
        {
-               $addr_parts = explode('@', $addr);
-               if (count($addr_parts) != 2) {
-                       return false;
+               $inboxes = [];
+
+               $condition = ['uid' => $uid, 'network' => Protocol::ACTIVITYPUB, 'archive' => false, 'pending' => false];
+
+               if (!empty($uid)) {
+                       $condition['rel'] = [Contact::FOLLOWER, Contact::FRIEND];
+               }
+
+               $contacts = DBA::select('contact', ['notify', 'batch'], $condition);
+               while ($contact = DBA::fetch($contacts)) {
+                       $contact = defaults($contact, 'batch', $contact['notify']);
+                       $inboxes[$contact] = $contact;
                }
+               DBA::close($contacts);
 
-               $webfinger = 'https://' . $addr_parts[1] . '/.well-known/webfinger?resource=acct:' . urlencode($addr);
+               return $inboxes;
+       }
 
-               $ret = Network::curl($webfinger, false, $redirects, ['accept_content' => 'application/jrd+json,application/json']);
-               if (!$ret['success'] || empty($ret['body'])) {
-                       return false;
+       /**
+        * @brief Fetches an array of inboxes for the given item and user
+        *
+        * @param array $item
+        * @param integer $uid User ID
+        *
+        * @return array with inboxes
+        */
+       public static function fetchTargetInboxes($item, $uid)
+       {
+               $permissions = self::createPermissionBlockForItem($item);
+               if (empty($permissions)) {
+                       return [];
                }
 
-               $data = json_decode($ret['body'], true);
+               $inboxes = [];
 
-               if (empty($data['links'])) {
-                       return false;
+               if ($item['gravity'] == GRAVITY_ACTIVITY) {
+                       $item_profile = APContact::getByURL($item['author-link']);
+               } else {
+                       $item_profile = APContact::getByURL($item['owner-link']);
                }
 
-               foreach ($data['links'] as $link) {
-                       if (empty($link['href']) || empty($link['rel']) || empty($link['type'])) {
+               foreach (['to', 'cc', 'bto', 'bcc'] as $element) {
+                       if (empty($permissions[$element])) {
                                continue;
                        }
 
-                       if (($link['rel'] == 'self') && ($link['type'] == 'application/activity+json')) {
-                               return $link['href'];
+                       foreach ($permissions[$element] as $receiver) {
+                               if ($receiver == $item_profile['followers']) {
+                                       $inboxes = self::fetchTargetInboxesforUser($uid);
+                               } else {
+                                       $profile = APContact::getByURL($receiver);
+                                       if (!empty($profile)) {
+                                               $target = defaults($profile, 'sharedinbox', $profile['inbox']);
+                                               $inboxes[$target] = $target;
+                                       }
+                               }
                        }
                }
 
-               return false;
+               return $inboxes;
        }
 
        /**
-        * Fetches a profile from the given url
+        * @brief Returns the activity type of a given item
         *
-        * @param string $url profile url
-        * @return array
+        * @param array $item
+        *
+        * @return activity type
         */
-       public static function fetchProfile($url)
+       public static function getTypeOfItem($item)
        {
-               if (empty(parse_url($url, PHP_URL_SCHEME))) {
-                       $url = self::addrToUrl($url);
-                       if (empty($url)) {
-                               return false;
+               if ($item['verb'] == ACTIVITY_POST) {
+                       if ($item['created'] == $item['edited']) {
+                               $type = 'Create';
+                       } else {
+                               $type = 'Update';
                        }
+               } elseif ($item['verb'] == ACTIVITY_LIKE) {
+                       $type = 'Like';
+               } elseif ($item['verb'] == ACTIVITY_DISLIKE) {
+                       $type = 'Dislike';
+               } elseif ($item['verb'] == ACTIVITY_ATTEND) {
+                       $type = 'Accept';
+               } elseif ($item['verb'] == ACTIVITY_ATTENDNO) {
+                       $type = 'Reject';
+               } elseif ($item['verb'] == ACTIVITY_ATTENDMAYBE) {
+                       $type = 'TentativeAccept';
+               } else {
+                       $type = '';
                }
 
-               $data = self::fetchContent($url);
+               return $type;
+       }
+
+       /**
+        * @brief Creates an activity array for a given item id
+        *
+        * @param integer $item_id
+        * @param boolean $object_mode Is the activity item is used inside another object?
+        *
+        * @return array of activity
+        */
+       public static function createActivityFromItem($item_id, $object_mode = false)
+       {
+               $item = Item::selectFirst([], ['id' => $item_id, 'parent-network' => Protocol::NATIVE_SUPPORT]);
 
-               if (empty($data) || empty($data['id']) || empty($data['inbox'])) {
+               if (!DBA::isResult($item)) {
                        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'];
-               $profile['alias'] = self::processElement($data, 'url', 'href');
-
-               $parts = parse_url($profile['url']);
-               unset($parts['scheme']);
-               unset($parts['path']);
-               $profile['addr'] = $profile['nick'] . '@' . str_replace('//', '', Network::unparseURL($parts));
-
-               $profile['photo'] = self::processElement($data, 'icon', 'url');
-               $profile['about'] = defaults($data, 'summary', '');
-               $profile['batch'] = self::processElement($data, 'endpoints', 'sharedInbox');
-               $profile['pubkey'] = self::processElement($data, 'publicKey', 'publicKeyPem');
-               $profile['notify'] = $data['inbox'];
-               $profile['poll'] = $data['outbox'];
-
-               // Check if the address is resolvable
-               if (self::addrToUrl($profile['addr']) == $profile['url']) {
-                       $parts = parse_url($profile['url']);
-                       unset($parts['path']);
-                       $profile['baseurl'] = Network::unparseURL($parts);
-               } else {
-                       unset($profile['addr']);
+               $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 ($profile['url'] == $profile['alias']) {
-                       unset($profile['alias']);
-               }
+               $type = self::getTypeOfItem($item);
 
-               // Remove all "null" fields
-               foreach ($profile as $field => $content) {
-                       if (is_null($content)) {
-                               unset($profile[$field]);
+               if (!$object_mode) {
+                       $data = ['@context' => self::CONTEXT];
+
+                       if ($item['deleted'] && ($item['gravity'] == GRAVITY_ACTIVITY)) {
+                               $type = 'Undo';
+                       } elseif ($item['deleted']) {
+                               $type = 'Delete';
                        }
+               } else {
+                       $data = [];
                }
 
-               // Handled
-               unset($data['id']);
-               unset($data['inbox']);
-               unset($data['outbox']);
-               unset($data['preferredUsername']);
-               unset($data['name']);
-               unset($data['summary']);
-               unset($data['url']);
-               unset($data['publicKey']);
-               unset($data['endpoints']);
-               unset($data['icon']);
-               unset($data['uuid']);
-
-               // To-Do
-               unset($data['type']);
-               unset($data['manuallyApprovesFollowers']);
+               $data['id'] = $item['uri'] . '#' . $type;
+               $data['type'] = $type;
+               $data['actor'] = $item['author-link'];
 
-               // 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($data['updated']); // Kroeg
-
-/*             if (!empty($data)) {
-                       print_r($data);
-                       die();
-               }
-*/
-               return $profile;
-       }
+               $data['published'] = DateTimeFormat::utc($item["created"]."+00:00", DateTimeFormat::ATOM);
 
-       public static function fetchOutbox($url)
-       {
-               $data = self::fetchContent($url);
-               if (empty($data)) {
-                       return;
+               if ($item["created"] != $item["edited"]) {
+                       $data['updated'] = DateTimeFormat::utc($item["edited"]."+00:00", DateTimeFormat::ATOM);
                }
 
-               if (!empty($data['orderedItems'])) {
-                       $items = $data['orderedItems'];
-               } elseif (!empty($data['first']['orderedItems'])) {
-                       $items = $data['first']['orderedItems'];
-               } elseif (!empty($data['first'])) {
-                       self::fetchOutbox($data['first']);
-                       return;
+               $data['context'] = self::fetchContextURLForItem($item);
+
+               $data = array_merge($data, ActivityPub::createPermissionBlockForItem($item));
+
+               if (in_array($data['type'], ['Create', 'Update', 'Announce', 'Delete'])) {
+                       $data['object'] = self::createNote($item);
+               } elseif ($data['type'] == 'Undo') {
+                       $data['object'] = self::createActivityFromItem($item_id, true);
                } else {
-                       $items = [];
+                       $data['object'] = $item['thr-parent'];
                }
 
-               foreach ($items as $activity) {
-                       self::processActivity($activity, $url);
+               $owner = User::getOwnerDataById($item['uid']);
+
+               if (!$object_mode) {
+                       return LDSignature::sign($data, $owner);
+               } else {
+                       return $data;
                }
        }
 
-       function processActivity($activity, $url)
+       /**
+        * @brief Creates an object array for a given item id
+        *
+        * @param integer $item_id
+        *
+        * @return object array
+        */
+       public static function createObjectFromItemID($item_id)
        {
-               if (empty($activity['type'])) {
-                       return;
-               }
+               $item = Item::selectFirst([], ['id' => $item_id, 'parent-network' => Protocol::NATIVE_SUPPORT]);
 
-               if (empty($activity['object'])) {
-                       return;
+               if (!DBA::isResult($item)) {
+                       return false;
                }
 
-               if (empty($activity['actor'])) {
-                       return;
+               $data = ['@context' => self::CONTEXT];
+               $data = array_merge($data, self::createNote($item));
+
+               return $data;
+       }
+
+       /**
+        * @brief Returns a tag array for a given item array
+        *
+        * @param array $item
+        *
+        * @return array of tags
+        */
+       private static function createTagList($item)
+       {
+               $tags = [];
+
+               $terms = Term::tagArrayFromItemId($item['id'], TERM_MENTION);
+               foreach ($terms as $term) {
+                       $contact = Contact::getDetailsByURL($term['url']);
+                       if (!empty($contact['addr'])) {
+                               $mention = '@' . $contact['addr'];
+                       } else {
+                               $mention = '@' . $term['url'];
+                       }
+
+                       $tags[] = ['type' => 'Mention', 'href' => $term['url'], 'name' => $mention];
                }
+               return $tags;
+       }
 
-               $actor = self::processElement($activity, 'actor', 'id');
-               if (empty($actor)) {
-                       return;
+       /**
+        * @brief Fetches the "context" value for a givem item array from the "conversation" table
+        *
+        * @param array $item
+        *
+        * @return string with context url
+        */
+       private static function fetchContextURLForItem($item)
+       {
+               $conversation = DBA::selectFirst('conversation', ['conversation-href', 'conversation-uri'], ['item-uri' => $item['parent-uri']]);
+               if (DBA::isResult($conversation) && !empty($conversation['conversation-href'])) {
+                       $context_uri = $conversation['conversation-href'];
+               } elseif (DBA::isResult($conversation) && !empty($conversation['conversation-uri'])) {
+                       $context_uri = $conversation['conversation-uri'];
+               } else {
+                       $context_uri = str_replace('/objects/', '/context/', $item['parent-uri']);
                }
+               return $context_uri;
+       }
 
-               if (is_string($activity['object'])) {
-                       $object_url = $activity['object'];
-               } elseif (!empty($activity['object']['id'])) {
-                       $object_url = $activity['object']['id'];
+       /**
+        * @brief Creates a note/article object array
+        *
+        * @param array $item
+        *
+        * @return object array
+        */
+       private static function createNote($item)
+       {
+               if (!empty($item['title'])) {
+                       $type = 'Article';
                } else {
-                       return;
+                       $type = 'Note';
                }
 
-               $receivers = self::getReceivers($activity);
-               if (empty($receivers)) {
-                       return;
+               if ($item['deleted']) {
+                       $type = 'Tombstone';
                }
 
-               // ----------------------------------
-               // unhandled
-               unset($activity['@context']);
-               unset($activity['id']);
+               $data = [];
+               $data['id'] = $item['uri'];
+               $data['type'] = $type;
 
-               // Non standard
-               unset($activity['title']);
-               unset($activity['atomUri']);
-               unset($activity['context_id']);
-               unset($activity['statusnetConversationId']);
+               if ($item['deleted']) {
+                       return $data;
+               }
 
-               $structure = $activity;
+               $data['summary'] = null; // Ignore by now
 
-               // To-Do?
-               unset($activity['context']);
-               unset($activity['location']);
-
-               // handled
-               unset($activity['to']);
-               unset($activity['cc']);
-               unset($activity['bto']);
-               unset($activity['bcc']);
-               unset($activity['type']);
-               unset($activity['actor']);
-               unset($activity['object']);
-               unset($activity['published']);
-               unset($activity['updated']);
-               unset($activity['instrument']);
-               unset($activity['inReplyTo']);
-
-               if (!empty($activity)) {
-                       echo "Activity\n";
-                       print_r($activity);
-                       die($url."\n");
-               }
-
-               $activity = $structure;
-               // ----------------------------------
-
-               $item = self::fetchObject($object_url, $url);
-               if (empty($item)) {
-                       return;
+               if ($item['uri'] != $item['thr-parent']) {
+                       $data['inReplyTo'] = $item['thr-parent'];
+               } else {
+                       $data['inReplyTo'] = null;
                }
 
-               $item = self::addActivityFields($item, $activity);
+               $data['diaspora:guid'] = $item['guid'];
+               $data['published'] = DateTimeFormat::utc($item["created"]."+00:00", DateTimeFormat::ATOM);
 
-               $item['owner'] = $actor;
+               if ($item["created"] != $item["edited"]) {
+                       $data['updated'] = DateTimeFormat::utc($item["edited"]."+00:00", DateTimeFormat::ATOM);
+               }
 
-               $item['receiver'] = array_merge($item['receiver'], $receivers);
+               $data['url'] = $item['plink'];
+               $data['attributedTo'] = $item['author-link'];
+               $data['actor'] = $item['author-link'];
+               $data['sensitive'] = false; // - Query NSFW
+               $data['context'] = self::fetchContextURLForItem($item);
 
-               switch ($activity['type']) {
-                       case 'Create':
-                       case 'Update':
-                               self::createItem($item);
-                               break;
+               if (!empty($item['title'])) {
+                       $data['name'] = BBCode::convert($item['title'], false, 7);
+               }
+
+               $data['content'] = BBCode::convert($item['body'], false, 7);
+               $data['source'] = ['content' => $item['body'], 'mediaType' => "text/bbcode"];
+
+               if (!empty($item['signed_text']) && ($item['uri'] != $item['thr-parent'])) {
+                       $data['diaspora:comment'] = $item['signed_text'];
+               }
+
+               $data['attachment'] = []; // @ToDo
+               $data['tag'] = self::createTagList($item);
+               $data = array_merge($data, ActivityPub::createPermissionBlockForItem($item));
+
+               return $data;
+       }
+
+       /**
+        * @brief Transmits a profile deletion to a given inbox
+        *
+        * @param integer $uid User ID
+        * @param string $inbox Target inbox
+        */
+       public static function transmitProfileDeletion($uid, $inbox)
+       {
+               $owner = User::getOwnerDataById($uid);
+               $profile = APContact::getByURL($owner['url']);
 
+               $data = ['@context' => 'https://www.w3.org/ns/activitystreams',
+                       'id' => System::baseUrl() . '/activity/' . System::createGUID(),
+                       'type' => 'Delete',
+                       'actor' => $owner['url'],
+                       'object' => self::profile($uid),
+                       'published' => DateTimeFormat::utcNow(DateTimeFormat::ATOM),
+                       'to' => [self::PUBLIC_COLLECTION],
+                       'cc' => []];
+
+               $signed = LDSignature::sign($data, $owner);
+
+               logger('Deliver profile deletion for user ' . $uid . ' to ' . $inbox .' via ActivityPub', LOGGER_DEBUG);
+               HTTPSignature::transmit($signed, $inbox, $uid);
+       }
+
+       /**
+        * @brief Transmits a profile change to a given inbox
+        *
+        * @param integer $uid User ID
+        * @param string $inbox Target inbox
+        */
+       public static function transmitProfileUpdate($uid, $inbox)
+       {
+               $owner = User::getOwnerDataById($uid);
+               $profile = APContact::getByURL($owner['url']);
+
+               $data = ['@context' => 'https://www.w3.org/ns/activitystreams',
+                       'id' => System::baseUrl() . '/activity/' . System::createGUID(),
+                       'type' => 'Update',
+                       'actor' => $owner['url'],
+                       'object' => self::profile($uid),
+                       'published' => DateTimeFormat::utcNow(DateTimeFormat::ATOM),
+                       'to' => [$profile['followers']],
+                       'cc' => []];
+
+               $signed = LDSignature::sign($data, $owner);
+
+               logger('Deliver profile update for user ' . $uid . ' to ' . $inbox .' via ActivityPub', LOGGER_DEBUG);
+               HTTPSignature::transmit($signed, $inbox, $uid);
+       }
+
+       /**
+        * @brief Transmits a given activity to a target
+        *
+        * @param array $activity
+        * @param string $target Target profile
+        * @param integer $uid User ID
+        */
+       public static function transmitActivity($activity, $target, $uid)
+       {
+               $profile = APContact::getByURL($target);
+
+               $owner = User::getOwnerDataById($uid);
+
+               $data = ['@context' => 'https://www.w3.org/ns/activitystreams',
+                       'id' => System::baseUrl() . '/activity/' . System::createGUID(),
+                       'type' => $activity,
+                       'actor' => $owner['url'],
+                       'object' => $profile['url'],
+                       'to' => $profile['url']];
+
+               logger('Sending activity ' . $activity . ' to ' . $target . ' for user ' . $uid, LOGGER_DEBUG);
+
+               $signed = LDSignature::sign($data, $owner);
+               HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+       }
+
+       /**
+        * @brief Transmit a message that the contact request had been accepted
+        *
+        * @param string $target Target profile
+        * @param $id
+        * @param integer $uid User ID
+        */
+       public static function transmitContactAccept($target, $id, $uid)
+       {
+               $profile = APContact::getByURL($target);
+
+               $owner = User::getOwnerDataById($uid);
+               $data = ['@context' => 'https://www.w3.org/ns/activitystreams',
+                       'id' => System::baseUrl() . '/activity/' . System::createGUID(),
+                       'type' => 'Accept',
+                       'actor' => $owner['url'],
+                       'object' => ['id' => $id, 'type' => 'Follow',
+                               'actor' => $profile['url'],
+                               'object' => $owner['url']],
+                       'to' => $profile['url']];
+
+               logger('Sending accept to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
+
+               $signed = LDSignature::sign($data, $owner);
+               HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+       }
+
+       /**
+        * @brief 
+        *
+        * @param string $target Target profile
+        * @param $id
+        * @param integer $uid User ID
+        */
+       public static function transmitContactReject($target, $id, $uid)
+       {
+               $profile = APContact::getByURL($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, $owner);
+               HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+       }
+
+       /**
+        * @brief 
+        *
+        * @param string $target Target profile
+        * @param integer $uid User ID
+        */
+       public static function transmitContactUndo($target, $uid)
+       {
+               $profile = APContact::getByURL($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']],
+                       'to' => $profile['url']];
+
+               logger('Sending undo to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
+
+               $signed = LDSignature::sign($data, $owner);
+               HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+       }
+
+       /**
+        * Fetches ActivityPub content from the given url
+        *
+        * @param string $url content url
+        * @return array
+        */
+       public static function fetchContent($url)
+       {
+               $ret = Network::curl($url, false, $redirects, ['accept_content' => 'application/activity+json, application/ld+json']);
+               if (!$ret['success'] || empty($ret['body'])) {
+                       return false;
+               }
+
+               return json_decode($ret['body'], true);
+       }
+
+       /**
+        * Fetches a profile from the given url into an array that is compatible to Probe::uri
+        *
+        * @param string $url profile url
+        * @return array
+        */
+       public static function probeProfile($url)
+       {
+               $apcontact = APContact::getByURL($url, true);
+               if (empty($apcontact)) {
+                       return false;
+               }
+
+               $profile = ['network' => Protocol::ACTIVITYPUB];
+               $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'] = $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 => $content) {
+                       if (is_null($content)) {
+                               unset($profile[$field]);
+                       }
+               }
+
+               return $profile;
+       }
+
+       /**
+        * @brief 
+        *
+        * @param $body
+        * @param $header
+        * @param integer $uid User ID
+        */
+       public static function processInbox($body, $header, $uid)
+       {
+               $http_signer = HTTPSignature::getSigner($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);
+
+               $actor = JsonLD::fetchElement($activity, 'actor', 'id');
+               logger('Message for user ' . $uid . ' is from actor ' . $actor, LOGGER_DEBUG);
+
+               if (empty($activity)) {
+                       logger('Invalid body.', LOGGER_DEBUG);
+                       return;
+               }
+
+               if (LDSignature::isSigned($activity)) {
+                       $ld_signer = LDSignature::getSigner($activity);
+                       if (empty($ld_signer)) {
+                               logger('Invalid JSON-LD signature from ' . $actor, LOGGER_DEBUG);
+                       }
+                       if (!empty($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);
+       }
+
+       /**
+        * @brief 
+        *
+        * @param $url
+        * @param integer $uid User ID
+        */
+       public static function fetchOutbox($url, $uid)
+       {
+               $data = self::fetchContent($url);
+               if (empty($data)) {
+                       return;
+               }
+
+               if (!empty($data['orderedItems'])) {
+                       $items = $data['orderedItems'];
+               } elseif (!empty($data['first']['orderedItems'])) {
+                       $items = $data['first']['orderedItems'];
+               } elseif (!empty($data['first'])) {
+                       self::fetchOutbox($data['first'], $uid);
+                       return;
+               } else {
+                       $items = [];
+               }
+
+               foreach ($items as $activity) {
+                       self::processActivity($activity, '', $uid, true);
+               }
+       }
+
+       /**
+        * @brief 
+        *
+        * @param array $activity
+        * @param integer $uid User ID
+        * @param $trust_source
+        *
+        * @return 
+        */
+       private static function prepareObjectData($activity, $uid, &$trust_source)
+       {
+               $actor = JsonLD::fetchElement($activity, 'actor', 'id');
+               if (empty($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, $additional);
+               }
+
+               logger('Receivers: ' . json_encode($receivers), LOGGER_DEBUG);
+
+               $object_id = JsonLD::fetchElement($activity, 'object', 'id');
+               if (empty($object_id)) {
+                       logger('No object found', LOGGER_DEBUG);
+                       return [];
+               }
+
+               // Fetch the content only on activities where this matters
+               if (in_array($activity['type'], ['Create', 'Announce'])) {
+                       $object_data = self::fetchObject($object_id, $activity['object'], $trust_source);
+                       if (empty($object_data)) {
+                               logger("Object data couldn't be processed", LOGGER_DEBUG);
+                               return [];
+                       }
+                       // We had been able to retrieve the object data - so we can trust the source
+                       $trust_source = true;
+               } elseif (in_array($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.
+                       $object_data = self::processObject($activity);
+                       $object_data['name'] = $activity['type'];
+                       $object_data['author'] = $activity['actor'];
+                       $object_data['object'] = $object_id;
+                       $object_data['object_type'] = ''; // Since we don't fetch the object, we don't know the type
+               } else {
+                       $object_data = [];
+                       $object_data['id'] = $activity['id'];
+                       $object_data['object'] = $activity['object'];
+                       $object_data['object_type'] = JsonLD::fetchElement($activity, 'object', 'type');
+               }
+
+               $object_data = self::addActivityFields($object_data, $activity);
+
+               $object_data['type'] = $activity['type'];
+               $object_data['owner'] = $actor;
+               $object_data['receiver'] = array_merge(defaults($object_data, 'receiver', []), $receivers);
+
+               logger('Processing ' . $object_data['type'] . ' ' . $object_data['object_type'] . ' ' . $object_data['id'], LOGGER_DEBUG);
+
+               return $object_data;
+       }
+
+       /**
+        * @brief 
+        *
+        * @param array $activity
+        * @param $body
+        * @param integer $uid User ID
+        * @param $trust_source
+        */
+       private static function processActivity($activity, $body = '', $uid = null, $trust_source = false)
+       {
+               if (empty($activity['type'])) {
+                       logger('Empty type', LOGGER_DEBUG);
+                       return;
+               }
+
+               if (empty($activity['object'])) {
+                       logger('Empty object', LOGGER_DEBUG);
+                       return;
+               }
+
+               if (empty($activity['actor'])) {
+                       logger('Empty actor', LOGGER_DEBUG);
+                       return;
+
+               }
+
+               // $trust_source is called by reference and is set to true if the content was retrieved successfully
+               $object_data = self::prepareObjectData($activity, $uid, $trust_source);
+               if (empty($object_data)) {
+                       logger('No object data found', LOGGER_DEBUG);
+                       return;
+               }
+
+               if (!$trust_source) {
+                       logger('No trust for activity type "' . $activity['type'] . '", so we quit now.', LOGGER_DEBUG);
+               }
+
+               switch ($activity['type']) {
+                       case 'Create':
                        case 'Announce':
-                               self::announceItem($item);
+                               self::createItem($object_data, $body);
                                break;
 
                        case 'Like':
+                               self::likeItem($object_data, $body);
+                               break;
+
                        case 'Dislike':
-                               self::activityItem($item);
+                               self::dislikeItem($object_data, $body);
+                               break;
+
+                       case 'Update':
+                               if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+                                       /// @todo
+                               } elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
+                                       self::updatePerson($object_data, $body);
+                               }
+                               break;
+
+                       case 'Delete':
+                               if ($object_data['object_type'] == 'Tombstone') {
+                                       self::deleteItem($object_data, $body);
+                               } elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
+                                       self::deletePerson($object_data, $body);
+                               }
                                break;
 
                        case 'Follow':
+                               self::followUser($object_data);
+                               break;
+
+                       case 'Accept':
+                               if ($object_data['object_type'] == 'Follow') {
+                                       self::acceptFollowUser($object_data);
+                               }
+                               break;
+
+                       case 'Reject':
+                               if ($object_data['object_type'] == 'Follow') {
+                                       self::rejectFollowUser($object_data);
+                               }
+                               break;
+
+                       case 'Undo':
+                               if ($object_data['object_type'] == 'Follow') {
+                                       self::undoFollowUser($object_data);
+                               } elseif (in_array($object_data['object_type'], self::ACTIVITY_TYPES)) {
+                                       self::undoActivity($object_data);
+                               }
                                break;
 
                        default:
-                               echo "Unknown activity: ".$activity['type']."\n";
-                               print_r($item);
-                               die();
+                               logger('Unknown activity: ' . $activity['type'], LOGGER_DEBUG);
                                break;
                }
        }
 
-       private static function getReceivers($activity)
+       /**
+        * @brief 
+        *
+        * @param array $activity
+        * @param $actor
+        *
+        * @return 
+        */
+       private static function getReceivers($activity, $actor)
        {
                $receivers = [];
 
-               $elements = ['to', 'cc', 'bto', 'bcc'];
-               foreach ($elements as $element) {
+               // 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)) {
+                       $profile = APContact::getByURL($actor);
+                       $followers = defaults($profile, 'followers', '');
+
+                       logger('Actor: ' . $actor . ' - Followers: ' . $followers, LOGGER_DEBUG);
+               } else {
+                       logger('Empty actor', LOGGER_DEBUG);
+                       $followers = '';
+               }
+
+               foreach (['to', 'cc', 'bto', 'bcc'] as $element) {
                        if (empty($activity[$element])) {
                                continue;
                        }
 
-                       // The receiver can be an arror or a string
+                       // The receiver can be an array or a string
                        if (is_string($activity[$element])) {
                                $activity[$element] = [$activity[$element]];
                        }
 
                        foreach ($activity[$element] as $receiver) {
-                               if ($receiver == self::PUBLIC) {
-                                       $receivers[$receiver] = 0;
+                               if ($receiver == self::PUBLIC_COLLECTION) {
+                                       $receivers['uid:0'] = 0;
+                               }
+
+                               if (($receiver == self::PUBLIC_COLLECTION) && !empty($actor)) {
+                                       // This will most likely catch all OStatus connections to Mastodon
+                                       $condition = ['alias' => [$actor, normalise_link($actor)], 'rel' => [Contact::SHARING, Contact::FRIEND]
+                                               , 'archive' => false, 'pending' => false];
+                                       $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_COLLECTION]) && !empty($actor)) {
+                                       $condition = ['nurl' => normalise_link($actor), 'rel' => [Contact::SHARING, Contact::FRIEND],
+                                               'network' => Protocol::ACTIVITYPUB, 'archive' => false, 'pending' => false];
+                                       $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)];
-                               $contact = DBA::selectFirst('contact', ['id'], $condition);
+                               $contact = DBA::selectFirst('contact', ['uid'], $condition);
                                if (!DBA::isResult($contact)) {
                                        continue;
                                }
-                               $receivers[$receiver] = $contact['id'];
+                               $receivers['uid:' . $contact['uid']] = $contact['uid'];
                        }
                }
+
+               self::switchContacts($receivers, $actor);
+
                return $receivers;
        }
 
-       private static function addActivityFields($item, $activity)
+       /**
+        * @brief 
+        *
+        * @param $cid
+        * @param integer $uid User ID
+        * @param $url
+        */
+       private static function switchContact($cid, $uid, $url)
+       {
+               $profile = ActivityPub::probeProfile($url);
+               if (empty($profile)) {
+                       return;
+               }
+
+               logger('Switch contact ' . $cid . ' (' . $profile['url'] . ') for user ' . $uid . ' from OStatus to ActivityPub');
+
+               $photo = $profile['photo'];
+               unset($profile['photo']);
+               unset($profile['baseurl']);
+
+               $profile['nurl'] = normalise_link($profile['url']);
+               DBA::update('contact', $profile, ['id' => $cid]);
+
+               Contact::updateAvatar($photo, $uid, $cid);
+       }
+
+       /**
+        * @brief 
+        *
+        * @param $receivers
+        * @param $actor
+        */
+       private static function switchContacts($receivers, $actor)
        {
-               if (!empty($activity['published']) && empty($item['published'])) {
-                       $item['published'] = $activity['published'];
+               if (empty($actor)) {
+                       return;
                }
 
-               if (!empty($activity['updated']) && empty($item['updated'])) {
-                       $item['updated'] = $activity['updated'];
+               foreach ($receivers as $receiver) {
+                       $contact = DBA::selectFirst('contact', ['id'], ['uid' => $receiver, 'network' => Protocol::OSTATUS, 'nurl' => normalise_link($actor)]);
+                       if (DBA::isResult($contact)) {
+                               self::switchContact($contact['id'], $receiver, $actor);
+                       }
+
+                       $contact = DBA::selectFirst('contact', ['id'], ['uid' => $receiver, 'network' => Protocol::OSTATUS, 'alias' => [normalise_link($actor), $actor]]);
+                       if (DBA::isResult($contact)) {
+                               self::switchContact($contact['id'], $receiver, $actor);
+                       }
                }
+       }
 
-               if (!empty($activity['inReplyTo']) && empty($item['parent-uri'])) {
-                       $item['parent-uri'] = self::processElement($activity, 'inReplyTo', 'id');
+       /**
+        * @brief 
+        *
+        * @param $object_data
+        * @param array $activity
+        *
+        * @return 
+        */
+       private static function addActivityFields($object_data, $activity)
+       {
+               if (!empty($activity['published']) && empty($object_data['published'])) {
+                       $object_data['published'] = $activity['published'];
                }
 
-               if (!empty($activity['instrument'])) {
-                       $item['service'] = self::processElement($activity, 'instrument', 'name', 'Service');
+               if (!empty($activity['updated']) && empty($object_data['updated'])) {
+                       $object_data['updated'] = $activity['updated'];
                }
 
-               // Remove all "null" fields
-               foreach ($item as $field => $content) {
-                       if (is_null($content)) {
-                               unset($item[$field]);
-                       }
+               if (!empty($activity['inReplyTo']) && empty($object_data['parent-uri'])) {
+                       $object_data['parent-uri'] = JsonLD::fetchElement($activity, 'inReplyTo', 'id');
                }
 
-               return $item;
+               if (!empty($activity['instrument'])) {
+                       $object_data['service'] = JsonLD::fetchElement($activity, 'instrument', 'name', 'type', 'Service');
+               }
+               return $object_data;
        }
 
-       private static function fetchObject($object_url, $url)
+       /**
+        * @brief 
+        *
+        * @param $object_id
+        * @param $object
+        * @param $trust_source
+        *
+        * @return 
+        */
+       private static function fetchObject($object_id, $object = [], $trust_source = false)
        {
-               $data = self::fetchContent($object_url);
-               if (empty($data)) {
-                       return false;
+               if (!$trust_source || is_string($object)) {
+                       $data = self::fetchContent($object_id);
+                       if (empty($data)) {
+                               logger('Empty content for ' . $object_id . ', check if content is available locally.', LOGGER_DEBUG);
+                               $data = $object_id;
+                       } else {
+                               logger('Fetched content for ' . $object_id, LOGGER_DEBUG);
+                       }
+               } else {
+                       logger('Using original object for url ' . $object_id, 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_id, LOGGER_DEBUG);
+                       $data = self::createNote($item);
                }
 
                if (empty($data['type'])) {
+                       logger('Empty type', LOGGER_DEBUG);
                        return false;
-               } else {
-                       $type = $data['type'];
                }
 
-               if (in_array($type, ['Note', 'Article', 'Video'])) {
-                       $common = self::processCommonData($data, $url);
+               if (in_array($data['type'], self::CONTENT_TYPES)) {
+                       return self::processObject($data);
                }
 
-               switch ($type) {
-                       case 'Note':
-                               return array_merge($common, self::processNote($data, $url));
-                       case 'Article':
-                               return array_merge($common, self::processArticle($data, $url));
-                       case 'Video':
-                               return array_merge($common, self::processVideo($data, $url));
-
-                       case 'Announce':
-                               if (empty($data['object'])) {
-                                       return false;
-                               }
-                               return self::fetchObject($data['object'], $url);
-
-                       case 'Person':
-                       case 'Tombstone':
-                               break;
-
-                       default:
-                               echo "Unknown object type: ".$data['type']."\n";
-                               print_r($data);
-                               die($url."\n");
-                               break;
+               if ($data['type'] == 'Announce') {
+                       if (empty($data['object'])) {
+                               return false;
+                       }
+                       return self::fetchObject($data['object']);
                }
+
+               logger('Unhandled object type: ' . $data['type'], LOGGER_DEBUG);
        }
 
-       private static function processCommonData(&$object, $url)
+       /**
+        * @brief 
+        *
+        * @param $object
+        *
+        * @return 
+        */
+       private static function processObject($object)
        {
-               if (empty($object['id']) || empty($object['attributedTo'])) {
+               if (empty($object['id'])) {
                        return false;
                }
 
-               $item = [];
-               $item['uri'] = $object['id'];
+               $object_data = [];
+               $object_data['object_type'] = $object['type'];
+               $object_data['id'] = $object['id'];
 
                if (!empty($object['inReplyTo'])) {
-                       $item['reply-to-uri'] = self::processElement($object, 'inReplyTo', 'id');
+                       $object_data['reply-to-id'] = JsonLD::fetchElement($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, 'name', null);
-               $item['title'] = defaults($object, 'title', null);
-               $item['content'] = defaults($object, 'content', null);
-               $item['summary'] = defaults($object, 'summary', null);
-               $item['location'] = self::processElement($object, 'location', 'name', 'Place');
-               $item['attachments'] = defaults($object, 'attachment', null);
-               $item['tags'] = defaults($object, 'tag', null);
-               $item['service'] = self::processElement($object, 'instrument', 'name', 'Service');
-               $item['alternate-url'] = self::processElement($object, 'url', 'href');
-               $item['receiver'] = self::getReceivers($object);
-
-               // handled
-               unset($object['id']);
-               unset($object['inReplyTo']);
-               unset($object['published']);
-               unset($object['updated']);
-               unset($object['uuid']);
-               unset($object['attributedTo']);
-               unset($object['context']);
-               unset($object['conversation']);
-               unset($object['sensitive']);
-               unset($object['name']);
-               unset($object['title']);
-               unset($object['content']);
-               unset($object['summary']);
-               unset($object['location']);
-               unset($object['attachment']);
-               unset($object['tag']);
-               unset($object['instrument']);
-               unset($object['url']);
-               unset($object['to']);
-               unset($object['cc']);
-               unset($object['bto']);
-               unset($object['bcc']);
-
-               // To-Do
-               unset($object['source']);
+                       $object_data['reply-to-id'] = $object_data['id'];
+               }
+
+               $object_data['published'] = defaults($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'];
+               }
+
+               $actor = JsonLD::fetchElement($object, 'attributedTo', 'id');
+               if (empty($actor)) {
+                       $actor = defaults($object, 'actor', null);
+               }
+
+               $object_data['diaspora:guid'] = defaults($object, 'diaspora:guid', null);
+               $object_data['owner'] = $object_data['author'] = $actor;
+               $object_data['context'] = defaults($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']);
+
+               // Common object data:
 
                // 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']);
-
-               /*
-               audience, preview, endTime, startTime, generator, image
-               */
+               // @context, type, actor, signature, mediaType, duration, replies, icon
 
-               return $item;
-       }
+               // Also missing: (Defined in the standard, but currently unused)
+               // audience, preview, endTime, startTime, generator, image
 
-       private static function processNote($object, $url)
-       {
-               $item = [];
+               // Data in Notes:
+
+               // Unhandled
+               // contentMap, announcement_count, announcements, context_id, likes, like_count
+               // inReplyToStatusId, shares, quoteUrl, statusnetConversationId
+
+               // Data in video:
 
                // To-Do?
-               unset($object['emoji']);
-               unset($object['atomUri']);
-               unset($object['inReplyToAtomUri']);
+               // category, licence, language, commentsEnabled
 
                // 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']);
-
-               if (empty($object))
+               // views, waitTranscoding, state, support, subtitleLanguage
+               // likes, dislikes, shares, comments
+
+               return $object_data;
+       }
+
+       /**
+        * @brief Converts mentions from Pleroma into the Friendica format
+        *
+        * @param string $body
+        *
+        * @return converted body
+        */
+       private static function convertMentions($body)
+       {
+               $URLSearchString = "^\[\]";
+               $body = preg_replace("/\[url\=([$URLSearchString]*)\]([#@!])(.*?)\[\/url\]/ism", '$2[url=$1]$3[/url]', $body);
+
+               return $body;
+       }
+
+       /**
+        * @brief Constructs a string with tags for a given tag array
+        *
+        * @param array $tags
+        * @param boolean $sensitive
+        *
+        * @return string with tags
+        */
+       private static function constructTagList($tags, $sensitive)
+       {
+               if (empty($tags)) {
+                       return '';
+               }
+
+               $tag_text = '';
+               foreach ($tags as $tag) {
+                       if (in_array($tag['type'], ['Mention', 'Hashtag'])) {
+                               if (!empty($tag_text)) {
+                                       $tag_text .= ',';
+                               }
+
+                               $tag_text .= substr($tag['name'], 0, 1) . '[url=' . $tag['href'] . ']' . substr($tag['name'], 1) . '[/url]';
+                       }
+               }
+
+               /// @todo add nsfw for $sensitive
+
+               return $tag_text;
+       }
+
+       /**
+        * @brief 
+        *
+        * @param $attachments
+        * @param array $item
+        *
+        * @return item array
+        */
+       private static function constructAttachList($attachments, $item)
+       {
+               if (empty($attachments)) {
                        return $item;
+               }
 
-               echo "Unknown Note\n";
-               print_r($object);
-               print_r($item);
-               die($url."\n");
+               foreach ($attachments as $attach) {
+                       $filetype = strtolower(substr($attach['mediaType'], 0, strpos($attach['mediaType'], '/')));
+                       if ($filetype == 'image') {
+                               $item['body'] .= "\n[img]".$attach['url'].'[/img]';
+                       } else {
+                               if (!empty($item["attach"])) {
+                                       $item["attach"] .= ',';
+                               } else {
+                                       $item["attach"] = '';
+                               }
+                               if (!isset($attach['length'])) {
+                                       $attach['length'] = "0";
+                               }
+                               $item["attach"] .= '[attach]href="'.$attach['url'].'" length="'.$attach['length'].'" type="'.$attach['mediaType'].'" title="'.defaults($attach, 'name', '').'"[/attach]';
+                       }
+               }
 
-               return [];
+               return $item;
        }
 
-       private static function processArticle($object, $url)
+       /**
+        * @brief 
+        *
+        * @param array $activity
+        * @param $body
+        */
+       private static function createItem($activity, $body)
        {
                $item = [];
+               $item['verb'] = ACTIVITY_POST;
+               $item['parent-uri'] = $activity['reply-to-id'];
 
-               if (empty($object))
-                       return $item;
+               if ($activity['reply-to-id'] == $activity['id']) {
+                       $item['gravity'] = GRAVITY_PARENT;
+                       $item['object-type'] = ACTIVITY_OBJ_NOTE;
+               } else {
+                       $item['gravity'] = GRAVITY_COMMENT;
+                       $item['object-type'] = ACTIVITY_OBJ_COMMENT;
+               }
 
-               echo "Unknown Article\n";
-               print_r($object);
-               print_r($item);
-               die($url."\n");
+               if (($activity['id'] != $activity['reply-to-id']) && !Item::exists(['uri' => $activity['reply-to-id']])) {
+                       logger('Parent ' . $activity['reply-to-id'] . ' not found. Try to refetch it.');
+                       self::fetchMissingActivity($activity['reply-to-id'], $activity);
+               }
 
-               return [];
+               self::postItem($activity, $item, $body);
        }
 
-       private static function processVideo($object, $url)
+       /**
+        * @brief 
+        *
+        * @param array $activity
+        * @param $body
+        */
+       private static function likeItem($activity, $body)
        {
                $item = [];
+               $item['verb'] = ACTIVITY_LIKE;
+               $item['parent-uri'] = $activity['object'];
+               $item['gravity'] = GRAVITY_ACTIVITY;
+               $item['object-type'] = ACTIVITY_OBJ_NOTE;
 
-               // To-Do?
-               unset($object['category']);
-               unset($object['licence']);
-               unset($object['language']);
-               unset($object['commentsEnabled']);
+               self::postItem($activity, $item, $body);
+       }
 
-               // 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($object['comments']);
-
-               if (empty($object))
-                       return $item;
+       /**
+        * @brief Delete items
+        *
+        * @param array $activity
+        * @param $body
+        */
+       private static function deleteItem($activity)
+       {
+               $owner = Contact::getIdForURL($activity['owner']);
+               $object = JsonLD::fetchElement($activity, 'object', 'id');
+               logger('Deleting item ' . $object . ' from ' . $owner, LOGGER_DEBUG);
+               Item::delete(['uri' => $object, 'owner-id' => $owner]);
+       }
 
-               echo "Unknown Video\n";
-               print_r($object);
-               print_r($item);
-               die($url."\n");
+       /**
+        * @brief 
+        *
+        * @param array $activity
+        * @param $body
+        */
+       private static function dislikeItem($activity, $body)
+       {
+               $item = [];
+               $item['verb'] = ACTIVITY_DISLIKE;
+               $item['parent-uri'] = $activity['object'];
+               $item['gravity'] = GRAVITY_ACTIVITY;
+               $item['object-type'] = ACTIVITY_OBJ_NOTE;
 
-               return [];
+               self::postItem($activity, $item, $body);
        }
 
-       private static function processElement($array, $element, $key, $type = null)
+       /**
+        * @brief 
+        *
+        * @param array $activity
+        * @param array $item
+        * @param $body
+        */
+       private static function postItem($activity, $item, $body)
        {
-               if (empty($array)) {
-                       return false;
-               }
+               /// @todo What to do with $activity['context']?
 
-               if (empty($array[$element])) {
-                       return false;
+               if (($item['gravity'] != GRAVITY_PARENT) && !Item::exists(['uri' => $item['parent-uri']])) {
+                       logger('Parent ' . $item['parent-uri'] . ' not found, message will be discarded.', LOGGER_DEBUG);
+                       return;
                }
 
-               if (is_string($array[$element])) {
-                       return $array[$element];
+               $item['network'] = Protocol::ACTIVITYPUB;
+               $item['private'] = !in_array(0, $activity['receiver']);
+               $item['author-id'] = Contact::getIdForURL($activity['author'], 0, true);
+               $item['owner-id'] = Contact::getIdForURL($activity['owner'], 0, true);
+               $item['uri'] = $activity['id'];
+               $item['created'] = $activity['published'];
+               $item['edited'] = $activity['updated'];
+               $item['guid'] = $activity['diaspora:guid'];
+               $item['title'] = HTML::toBBCode($activity['name']);
+               $item['content-warning'] = HTML::toBBCode($activity['summary']);
+               $item['body'] = self::convertMentions(HTML::toBBCode($activity['content']));
+               $item['location'] = $activity['location'];
+               $item['tag'] = self::constructTagList($activity['tags'], $activity['sensitive']);
+               $item['app'] = $activity['service'];
+               $item['plink'] = defaults($activity, 'alternate-url', $item['uri']);
+
+               $item = self::constructAttachList($activity['attachments'], $item);
+
+               $source = JsonLD::fetchElement($activity, 'source', 'content', 'mediaType', 'text/bbcode');
+               if (!empty($source)) {
+                       $item['body'] = $source;
                }
 
-               if (is_null($type)) {
-                       if (!empty($array[$element][$key])) {
-                               return $array[$element][$key];
-                       }
+               $item['protocol'] = Conversation::PARCEL_ACTIVITYPUB;
+               $item['source'] = $body;
+               $item['conversation-href'] = $activity['context'];
+               $item['conversation-uri'] = $activity['conversation'];
+
+               foreach ($activity['receiver'] as $receiver) {
+                       $item['uid'] = $receiver;
+                       $item['contact-id'] = Contact::getIdForURL($activity['author'], $receiver, true);
 
-                       if (!empty($array[$element][0][$key])) {
-                               return $array[$element][0][$key];
+                       if (($receiver != 0) && empty($item['contact-id'])) {
+                               $item['contact-id'] = Contact::getIdForURL($activity['author'], 0, true);
                        }
 
-                       return false;
+                       $item_id = Item::insert($item);
+                       logger('Storing for user ' . $item['uid'] . ': ' . $item_id);
+               }
+       }
+
+       /**
+        * @brief 
+        *
+        * @param $url
+        * @param $child
+        */
+       private static function fetchMissingActivity($url, $child)
+       {
+               if (Config::get('system', 'ostatus_full_threads')) {
+                       return;
+               }
+
+               $object = ActivityPub::fetchContent($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.');
+       }
+
+       /**
+        * @brief perform a "follow" request
+        *
+        * @param array $activity
+        */
+       private static function followUser($activity)
+       {
+               $actor = JsonLD::fetchElement($activity, 'object', 'id');
+               $uid = User::getIdForURL($actor);
+               if (empty($uid)) {
+                       return;
+               }
+
+               $owner = User::getOwnerDataById($uid);
+
+               $cid = Contact::getIdForURL($activity['owner'], $uid);
+               if (!empty($cid)) {
+                       $contact = DBA::selectFirst('contact', [], ['id' => $cid]);
+               } else {
+                       $contact = false;
+               }
+
+               $item = ['author-id' => Contact::getIdForURL($activity['owner']),
+                       'author-link' => $activity['owner']];
+
+               Contact::addRelationship($owner, $contact, $item);
+               $cid = Contact::getIdForURL($activity['owner'], $uid);
+               if (empty($cid)) {
+                       return;
+               }
+
+               $contact = DBA::selectFirst('contact', ['network'], ['id' => $cid]);
+               if ($contact['network'] != Protocol::ACTIVITYPUB) {
+                       Contact::updateFromProbe($cid, Protocol::ACTIVITYPUB);
+               }
+
+               DBA::update('contact', ['hub-verify' => $activity['id']], ['id' => $cid]);
+               logger('Follow user ' . $uid . ' from contact ' . $cid . ' with id ' . $activity['id']);
+       }
+
+       /**
+        * @brief Update the given profile
+        *
+        * @param array $activity
+        */
+       private static function updatePerson($activity)
+       {
+               if (empty($activity['object']['id'])) {
+                       return;
+               }
+
+               logger('Updating profile for ' . $activity['object']['id'], LOGGER_DEBUG);
+               APContact::getByURL($activity['object']['id'], true);
+       }
+
+       /**
+        * @brief Delete the given profile
+        *
+        * @param array $activity
+        */
+       private static function deletePerson($activity)
+       {
+               if (empty($activity['object']['id']) || empty($activity['object']['actor'])) {
+                       logger('Empty object id or actor.', LOGGER_DEBUG);
+                       return;
                }
 
-               if (!empty($array[$element][$key]) && !empty($array[$element]['type']) && ($array[$element]['type'] == $type)) {
-                       return $array[$element][$key];
+               if ($activity['object']['id'] != $activity['object']['actor']) {
+                       logger('Object id does not match actor.', LOGGER_DEBUG);
+                       return;
                }
 
-               /// @todo Add array search
+               $contacts = DBA::select('contact', ['id'], ['nurl' => normalise_link($activity['object']['id'])]);
+               while ($contact = DBA::fetch($contacts)) {
+                       Contact::remove($contact["id"]);
+               }
+               DBA::close($contacts);
 
-               return false;
+               logger('Deleted contact ' . $activity['object']['id'], LOGGER_DEBUG);
        }
 
-       private static function createItem($item)
+       /**
+        * @brief Accept a follow request
+        *
+        * @param array $activity
+        */
+       private static function acceptFollowUser($activity)
        {
-//             print_r($item);
+               $actor = JsonLD::fetchElement($activity, 'object', 'actor');
+               $uid = User::getIdForURL($actor);
+               if (empty($uid)) {
+                       return;
+               }
+
+               $owner = User::getOwnerDataById($uid);
+
+               $cid = Contact::getIdForURL($activity['owner'], $uid);
+               if (empty($cid)) {
+                       logger('No contact found for ' . $activity['owner'], LOGGER_DEBUG);
+                       return;
+               }
+
+               $fields = ['pending' => false];
+
+               $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 announceItem($item)
+       /**
+        * @brief Reject a follow request
+        *
+        * @param array $activity
+        */
+       private static function rejectFollowUser($activity)
        {
-//             print_r($item);
+               $actor = JsonLD::fetchElement($activity, 'object', 'actor');
+               $uid = User::getIdForURL($actor);
+               if (empty($uid)) {
+                       return;
+               }
+
+               $owner = User::getOwnerDataById($uid);
+
+               $cid = Contact::getIdForURL($activity['owner'], $uid);
+               if (empty($cid)) {
+                       logger('No contact found for ' . $activity['owner'], LOGGER_DEBUG);
+                       return;
+               }
+
+               if (DBA::exists('contact', ['id' => $cid, 'rel' => Contact::SHARING, 'pending' => true])) {
+                       Contact::remove($cid);
+                       logger('Rejected contact request from contact ' . $cid . ' for user ' . $uid . ' - contact had been removed.', LOGGER_DEBUG);
+               } else {
+                       logger('Rejected contact request from contact ' . $cid . ' for user ' . $uid . '.', LOGGER_DEBUG);
+               }
        }
 
-       private static function activityItem($item)
+       /**
+        * @brief Undo activity like "like" or "dislike"
+        *
+        * @param array $activity
+        */
+       private static function undoActivity($activity)
        {
-       //      print_r($item);
+               $activity_url = JsonLD::fetchElement($activity, 'object', 'id');
+               if (empty($activity_url)) {
+                       return;
+               }
+
+               $actor = JsonLD::fetchElement($activity, 'object', 'actor');
+               if (empty($actor)) {
+                       return;
+               }
+
+               $author_id = Contact::getIdForURL($actor);
+               if (empty($author_id)) {
+                       return;
+               }
+
+               Item::delete(['uri' => $activity_url, 'author-id' => $author_id, 'gravity' => GRAVITY_ACTIVITY]);
        }
 
+       /**
+        * @brief Activity to remove a follower
+        *
+        * @param array $activity
+        */
+       private static function undoFollowUser($activity)
+       {
+               $object = JsonLD::fetchElement($activity, 'object', 'object');
+               $uid = User::getIdForURL($object);
+               if (empty($uid)) {
+                       return;
+               }
+
+               $owner = User::getOwnerDataById($uid);
+
+               $cid = Contact::getIdForURL($activity['owner'], $uid);
+               if (empty($cid)) {
+                       logger('No contact found for ' . $activity['owner'], LOGGER_DEBUG);
+                       return;
+               }
+
+               $contact = DBA::selectFirst('contact', [], ['id' => $cid]);
+               if (!DBA::isResult($contact)) {
+                       return;
+               }
+
+               Contact::removeFollower($owner, $contact);
+               logger('Undo following request from contact ' . $cid . ' for user ' . $uid, LOGGER_DEBUG);
+       }
 }