X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FProtocol%2FActivityPub.php;h=ef4a48479ea2a4c677704763af81d10272e443a8;hb=ec898ecd2a6a79e1e8a6a9dda94e90393eb08487;hp=b27101aac8fb2f30a07f8b11ab93cce2310068d9;hpb=b44fc62708f111449f9ead95c09d4570465c94b7;p=friendica.git

diff --git a/src/Protocol/ActivityPub.php b/src/Protocol/ActivityPub.php
index b27101aac8..ef4a48479e 100644
--- a/src/Protocol/ActivityPub.php
+++ b/src/Protocol/ActivityPub.php
@@ -12,7 +12,9 @@ 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;
@@ -21,6 +23,7 @@ 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
@@ -34,45 +37,211 @@ use Friendica\Util\LDSignature;
  *
  * Digest: https://tools.ietf.org/html/rfc5843
  * https://tools.ietf.org/html/draft-cavage-http-signatures-10#ref-15
- * https://github.com/digitalbazaar/php-json-ld
  *
- * Part of the code for HTTP signing is taken from the Osada project.
- * https://framagit.org/macgirvin/osada
+ * Mastodon implementation of supported activities:
+ * https://github.com/tootsuite/mastodon/blob/master/app/lib/activitypub/activity.rb#L26
  *
  * To-do:
  *
  * Receiver:
- * - Activities: Dislike, Update, Delete
- * - Object Types: Person, Tombstome
+ * - 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:
- * - Activities: Like, Dislike, Update, Delete, Announce
- * - Object Tyoes: Article, Person, Tombstone
+ * - Event
+ *
+ * Complicated:
+ * - Announce
+ * - Undo Announce
  *
  * General:
- * - Endpoints: Outbox, Follower, Following
- * - General cleanup
+ * - 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');
 	}
 
+	/**
+	 * @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)
+	{
+		$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 $data;
+		}
+
+		if (empty($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;
+		}
+
+		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;
+
+			$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[] = $object;
+			}
+
+			if (!empty($list)) {
+				$data['next'] = System::baseUrl() . '/outbox/' . $owner['nickname'] . '?page=' . ($page + 1);
+			}
+
+			$data['partOf'] = System::baseUrl() . '/outbox/' . $owner['nickname'];
+
+			$data['orderedItems'] = $list;
+		}
+
+		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', 'page-flags'];
@@ -93,13 +262,10 @@ class ActivityPub
 			return [];
 		}
 
-		$data = ['@context' => ['https://www.w3.org/ns/activitystreams', 'https://w3id.org/security/v1',
-			['vcard' => 'http://www.w3.org/2006/vcard/ns#', 'uuid' => 'http://schema.org/identifier',
-			'sensitive' => 'as:sensitive', 'manuallyApprovesFollowers' => 'as:manuallyApprovesFollowers']]];
-
+		$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'];
@@ -122,7 +288,14 @@ class ActivityPub
 		return $data;
 	}
 
-	public static function fetchPermissionBlockFromConversation($item)
+	/**
+	 * @brief Returns an array with permissions of a given item array
+	 *
+	 * @param array $item
+	 *
+	 * @return array with permissions
+	 */
+	private static function fetchPermissionBlockFromConversation($item)
 	{
 		if (empty($item['thr-parent'])) {
 			return [];
@@ -137,60 +310,75 @@ class ActivityPub
 		$activity = json_decode($conversation['source'], true);
 
 		$actor = JsonLD::fetchElement($activity, 'actor', 'id');
-		$profile = ActivityPub::fetchprofile($actor);
+		$profile = APContact::getByURL($actor);
 
-		$permissions = [];
+		$item_profile = APContact::getByURL($item['author-link']);
+		$exclude[] = $item['author-link'];
 
-		$elements = ['to', 'cc', 'bto', 'bcc'];
-		foreach ($elements as $element) {
+		if ($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']) {
-					$receiver = System::baseUrl() . '/followers/' . $item['author-nick'];
+				if ($receiver == $profile['followers'] && !empty($item_profile['followers'])) {
+					$receiver = $item_profile['followers'];
+				}
+				if (!in_array($receiver, $exclude)) {
+					$permissions[$element][] = $receiver;
 				}
-				$permissions[$element][] = $receiver;
 			}
 		}
 		return $permissions;
 	}
 
+	/**
+	 * @brief Creates an array of permissions from an item thread
+	 *
+	 * @param array $item
+	 *
+	 * @return permission array
+	 */
 	public static function createPermissionBlockForItem($item)
 	{
 		$data = ['to' => [], 'cc' => []];
 
 		$data = array_merge($data, self::fetchPermissionBlockFromConversation($item));
 
-		$terms = Term::tagArrayFromItemId($item['id']);
+		$actor_profile = APContact::getByURL($item['author-link']);
+
+		$terms = Term::tagArrayFromItemId($item['id'], TERM_MENTION);
+
+		$contacts[$item['author-link']] = $item['author-link'];
 
 		if (!$item['private']) {
-			$data['to'][] = self::PUBLIC;
-			$data['cc'][] = System::baseUrl() . '/followers/' . $item['author-nick'];
+			$data['to'][] = self::PUBLIC_COLLECTION;
+			if (!empty($actor_profile['followers'])) {
+				$data['cc'][] = $actor_profile['followers'];
+			}
 
 			foreach ($terms as $term) {
-				if ($term['type'] != TERM_MENTION) {
-					continue;
-				}
-				$profile = self::fetchprofile($term['url']);
-				if (!empty($profile)) {
+				$profile = APContact::getByURL($term['url'], false);
+				if (!empty($profile) && empty($contacts[$profile['url']])) {
 					$data['cc'][] = $profile['url'];
+					$contacts[$profile['url']] = $profile['url'];
 				}
 			}
 		} else {
-			//$data['cc'][] = System::baseUrl() . '/followers/' . $item['author-nick'];
 			$receiver_list = Item::enumeratePermissions($item);
 
 			$mentioned = [];
-			$contacts = [];
 
 			foreach ($terms as $term) {
-				if ($term['type'] != TERM_MENTION) {
-					continue;
-				}
 				$cid = Contact::getIdForURL($term['url'], $item['uid']);
 				if (!empty($cid) && in_array($cid, $receiver_list)) {
 					$contact = DBA::selectFirst('contact', ['url'], ['id' => $cid, 'network' => Protocol::ACTIVITYPUB]);
@@ -206,99 +394,155 @@ class ActivityPub
 					$contacts[$contact['url']] = $contact['url'];
 				}
 			}
+		}
+
+		$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;
+			}
 
-			if (empty($data['to'])) {
-				$data['to'] = $data['cc'];
-				$data['cc'] = [];
+			$profile = APContact::getByURL($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;
 	}
 
-	public static function fetchTargetInboxes($item, $uid)
+	/**
+	 * @brief Fetches a list of inboxes of followers of a given user
+	 *
+	 * @param integer $uid User ID
+	 *
+	 * @return array of follower inboxes
+	 */
+	public static function fetchTargetInboxesforUser($uid)
 	{
 		$inboxes = [];
 
-		$parents = Item::select(['author-link', 'owner-link'], ['parent' => $item['parent']]);
-		while ($parent = Item::fetch($parents)) {
-			$profile = self::fetchprofile($parent['author-link']);
-			if (!empty($profile)) {
-				$target = defaults($profile, 'sharedinbox', $profile['inbox']);
-				$inboxes[$target] = $target;
-			}
-			$profile = self::fetchprofile($parent['owner-link']);
-			if (!empty($profile)) {
-				$target = defaults($profile, 'sharedinbox', $profile['inbox']);
-				$inboxes[$target] = $target;
-			}
+		$condition = ['uid' => $uid, 'network' => Protocol::ACTIVITYPUB, 'archive' => false, 'pending' => false];
+
+		if (!empty($uid)) {
+			$condition['rel'] = [Contact::FOLLOWER, Contact::FRIEND];
 		}
-		DBA::close($parents);
 
-		$terms = Term::tagArrayFromItemId($item['id']);
-		if (!$item['private']) {
-			$contacts = DBA::select('contact', ['notify', 'batch'], ['uid' => $uid,
-					'rel' => [Contact::FOLLOWER, Contact::FRIEND], 'network' => Protocol::ACTIVITYPUB]);
-			while ($contact = DBA::fetch($contacts)) {
-				$contact = defaults($contact, 'batch', $contact['notify']);
-				$inboxes[$contact] = $contact;
-			}
-			DBA::close($contacts);
+		$contacts = DBA::select('contact', ['notify', 'batch'], $condition);
+		while ($contact = DBA::fetch($contacts)) {
+			$contact = defaults($contact, 'batch', $contact['notify']);
+			$inboxes[$contact] = $contact;
+		}
+		DBA::close($contacts);
 
-			foreach ($terms as $term) {
-				if ($term['type'] != TERM_MENTION) {
-					continue;
-				}
-				$profile = self::fetchprofile($term['url']);
-				if (!empty($profile)) {
-					$target = defaults($profile, 'sharedinbox', $profile['inbox']);
-					$inboxes[$target] = $target;
-				}
-			}
+		return $inboxes;
+	}
+
+	/**
+	 * @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 [];
+		}
+
+		$inboxes = [];
+
+		if ($item['gravity'] == GRAVITY_ACTIVITY) {
+			$item_profile = APContact::getByURL($item['author-link']);
 		} else {
-			$receiver_list = Item::enumeratePermissions($item);
-			$mentioned = [];
+			$item_profile = APContact::getByURL($item['owner-link']);
+		}
 
-			foreach ($terms as $term) {
-				if ($term['type'] != TERM_MENTION) {
-					continue;
-				}
-				$cid = Contact::getIdForURL($term['url'], $uid);
-				if (!empty($cid) && in_array($cid, $receiver_list)) {
-					$contact = DBA::selectFirst('contact', ['url'], ['id' => $cid, 'network' => Protocol::ACTIVITYPUB]);
-					$profile = self::fetchprofile($contact['url']);
+		foreach (['to', 'cc', 'bto', 'bcc'] as $element) {
+			if (empty($permissions[$element])) {
+				continue;
+			}
+
+			foreach ($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] = $target;
 					}
 				}
 			}
-
-			foreach ($receiver_list as $receiver) {
-				$contact = DBA::selectFirst('contact', ['url'], ['id' => $receiver, 'network' => Protocol::ACTIVITYPUB]);
-				$profile = self::fetchprofile($contact['url']);
-				if (!empty($profile)) {
-					$target = defaults($profile, 'sharedinbox', $profile['inbox']);
-					$inboxes[$target] = $target;
-				}
-			}
 		}
 
-		$profile = self::fetchprofile($item['author-link']);
-		if (!empty($profile['sharedinbox'])) {
-			unset($inboxes[$profile['sharedinbox']]);
-		}
+		return $inboxes;
+	}
 
-		if (!empty($profile['inbox'])) {
-			unset($inboxes[$profile['inbox']]);
+	/**
+	 * @brief Returns the activity type of a given item
+	 *
+	 * @param array $item
+	 *
+	 * @return activity type
+	 */
+	public static function getTypeOfItem($item)
+	{
+		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 = '';
 		}
 
-		return $inboxes;
+		return $type;
 	}
 
-	public static function createActivityFromItem($item_id)
+	/**
+	 * @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]);
+		$item = Item::selectFirst([], ['id' => $item_id, 'parent-network' => Protocol::NATIVE_SUPPORT]);
 
 		if (!DBA::isResult($item)) {
 			return false;
@@ -313,14 +557,22 @@ class ActivityPub
 			}
 		}
 
-		$data = ['@context' => ['https://www.w3.org/ns/activitystreams', 'https://w3id.org/security/v1',
-			['ostatus' => 'http://ostatus.org#', 'sensitive' => 'as:sensitive',
-			'Hashtag' => 'as:Hashtag', 'atomUri' => 'ostatus:atomUri',
-			'conversation' => 'ostatus:conversation',
-			'inReplyToAtomUri' => 'ostatus:inReplyToAtomUri']]];
+		$type = self::getTypeOfItem($item);
+
+		if (!$object_mode) {
+			$data = ['@context' => self::CONTEXT];
 
-		$data['id'] = $item['uri'] . '#activity';
-		$data['type'] = 'Create';
+			if ($item['deleted'] && ($item['gravity'] == GRAVITY_ACTIVITY)) {
+				$type = 'Undo';
+			} elseif ($item['deleted']) {
+				$type = 'Delete';
+			}
+		} else {
+			$data = [];
+		}
+
+		$data['id'] = $item['uri'] . '#' . $type;
+		$data['type'] = $type;
 		$data['actor'] = $item['author-link'];
 
 		$data['published'] = DateTimeFormat::utc($item["created"]."+00:00", DateTimeFormat::ATOM);
@@ -329,61 +581,120 @@ class ActivityPub
 			$data['updated'] = DateTimeFormat::utc($item["edited"]."+00:00", DateTimeFormat::ATOM);
 		}
 
+		$data['context'] = self::fetchContextURLForItem($item);
+
 		$data = array_merge($data, ActivityPub::createPermissionBlockForItem($item));
 
-		$data['object'] = self::createNote($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 {
+			$data['object'] = $item['thr-parent'];
+		}
 
 		$owner = User::getOwnerDataById($item['uid']);
 
-		return LDSignature::sign($data, $owner);
+		if (!$object_mode) {
+			return LDSignature::sign($data, $owner);
+		} else {
+			return $data;
+		}
 	}
 
+	/**
+	 * @brief Creates an object array for a given item id
+	 *
+	 * @param integer $item_id
+	 *
+	 * @return object array
+	 */
 	public static function createObjectFromItemID($item_id)
 	{
-		$item = Item::selectFirst([], ['id' => $item_id]);
+		$item = Item::selectFirst([], ['id' => $item_id, 'parent-network' => Protocol::NATIVE_SUPPORT]);
 
 		if (!DBA::isResult($item)) {
 			return false;
 		}
 
-		$data = ['@context' => ['https://www.w3.org/ns/activitystreams', 'https://w3id.org/security/v1',
-			['ostatus' => 'http://ostatus.org#', 'sensitive' => 'as:sensitive',
-			'Hashtag' => 'as:Hashtag', 'atomUri' => 'ostatus:atomUri',
-			'conversation' => 'ostatus:conversation',
-			'inReplyToAtomUri' => 'ostatus:inReplyToAtomUri']]];
-
+		$data = ['@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']);
+		$terms = Term::tagArrayFromItemId($item['id'], TERM_MENTION);
 		foreach ($terms as $term) {
-			if ($term['type'] == TERM_MENTION) {
-				$contact = Contact::getDetailsByURL($term['url']);
-				if (!empty($contact['addr'])) {
-					$mention = '@' . $contact['addr'];
-				} else {
-					$mention = '@' . $term['url'];
-				}
-
-				$tags[] = ['type' => 'Mention', 'href' => $term['url'], 'name' => $mention];
+			$contact = Contact::getDetailsByURL($term['url']);
+			if (!empty($contact['addr'])) {
+				$mention = '@' . $contact['addr'];
+			} else {
+				$mention = '@' . $term['url'];
 			}
-		}
 
+			$tags[] = ['type' => 'Mention', 'href' => $term['url'], 'name' => $mention];
+		}
 		return $tags;
 	}
 
-	public static function createNote($item)
+	/**
+	 * @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;
+	}
+
+	/**
+	 * @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 {
+			$type = 'Note';
+		}
+
+		if ($item['deleted']) {
+			$type = 'Tombstone';
+		}
+
 		$data = [];
 		$data['id'] = $item['uri'];
-		$data['type'] = 'Note';
+		$data['type'] = $type;
+
+		if ($item['deleted']) {
+			return $data;
+		}
+
 		$data['summary'] = null; // Ignore by now
 
 		if ($item['uri'] != $item['thr-parent']) {
@@ -392,25 +703,18 @@ class ActivityPub
 			$data['inReplyTo'] = null;
 		}
 
+		$data['diaspora:guid'] = $item['guid'];
 		$data['published'] = DateTimeFormat::utc($item["created"]."+00:00", DateTimeFormat::ATOM);
 
 		if ($item["created"] != $item["edited"]) {
 			$data['updated'] = DateTimeFormat::utc($item["edited"]."+00:00", DateTimeFormat::ATOM);
 		}
 
-		$data['url'] = $item['uri'];
+		$data['url'] = $item['plink'];
 		$data['attributedTo'] = $item['author-link'];
 		$data['actor'] = $item['author-link'];
 		$data['sensitive'] = false; // - Query NSFW
-
-		$conversation = DBA::selectFirst('conversation', ['conversation-uri'], ['item-uri' => $item['parent-uri']]);
-		if (DBA::isResult($conversation) && !empty($conversation['conversation-uri'])) {
-			$conversation_uri = $conversation['conversation-uri'];
-		} else {
-			$conversation_uri = $item['parent-uri'];
-		}
-
-		$data['conversation'] = $conversation_uri;
+		$data['context'] = self::fetchContextURLForItem($item);
 
 		if (!empty($item['title'])) {
 			$data['name'] = BBCode::convert($item['title'], false, 7);
@@ -418,17 +722,80 @@ class ActivityPub
 
 		$data['content'] = BBCode::convert($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));
 
-		//$data['emoji'] = []; // Ignore by now
 		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)
 	{
-		$profile = self::fetchprofile($target);
+		$profile = APContact::getByURL($target);
 
 		$owner = User::getOwnerDataById($uid);
 
@@ -442,12 +809,19 @@ class ActivityPub
 		logger('Sending activity ' . $activity . ' to ' . $target . ' for user ' . $uid, LOGGER_DEBUG);
 
 		$signed = LDSignature::sign($data, $owner);
-		return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+		HTTPSignature::transmit($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)
 	{
-		$profile = self::fetchprofile($target);
+		$profile = APContact::getByURL($target);
 
 		$owner = User::getOwnerDataById($uid);
 		$data = ['@context' => 'https://www.w3.org/ns/activitystreams',
@@ -462,12 +836,19 @@ class ActivityPub
 		logger('Sending accept to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
 
 		$signed = LDSignature::sign($data, $owner);
-		return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+		HTTPSignature::transmit($signed, $profile['inbox'], $uid);
 	}
 
+	/**
+	 * @brief 
+	 *
+	 * @param string $target Target profile
+	 * @param $id
+	 * @param integer $uid User ID
+	 */
 	public static function transmitContactReject($target, $id, $uid)
 	{
-		$profile = self::fetchprofile($target);
+		$profile = APContact::getByURL($target);
 
 		$owner = User::getOwnerDataById($uid);
 		$data = ['@context' => 'https://www.w3.org/ns/activitystreams',
@@ -482,12 +863,18 @@ class ActivityPub
 		logger('Sending reject to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
 
 		$signed = LDSignature::sign($data, $owner);
-		return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+		HTTPSignature::transmit($signed, $profile['inbox'], $uid);
 	}
 
+	/**
+	 * @brief 
+	 *
+	 * @param string $target Target profile
+	 * @param integer $uid User ID
+	 */
 	public static function transmitContactUndo($target, $uid)
 	{
-		$profile = self::fetchprofile($target);
+		$profile = APContact::getByURL($target);
 
 		$id = System::baseUrl() . '/activity/' . System::createGUID();
 
@@ -504,152 +891,23 @@ class ActivityPub
 		logger('Sending undo to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
 
 		$signed = LDSignature::sign($data, $owner);
-		return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+		HTTPSignature::transmit($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($ret['body'])) {
-			return;
-		}
-
-		return json_decode($ret['body'], true);
-	}
-
-	/**
-	 * Resolves the profile url from the address by using webfinger
-	 *
-	 * @param string $addr profile address (user@domain.tld)
-	 * @return string url
-	 */
-	private static function addrToUrl($addr)
-	{
-		$addr_parts = explode('@', $addr);
-		if (count($addr_parts) != 2) {
-			return false;
-		}
-
-		$webfinger = 'https://' . $addr_parts[1] . '/.well-known/webfinger?resource=acct:' . urlencode($addr);
-
-		$ret = Network::curl($webfinger, false, $redirects, ['accept_content' => 'application/jrd+json,application/json']);
-		if (!$ret['success'] || empty($ret['body'])) {
-			return false;
-		}
-
-		$data = json_decode($ret['body'], true);
-
-		if (empty($data['links'])) {
-			return false;
-		}
-
-		foreach ($data['links'] as $link) {
-			if (empty($link['href']) || empty($link['rel']) || empty($link['type'])) {
-				continue;
-			}
-
-			if (($link['rel'] == 'self') && ($link['type'] == 'application/activity+json')) {
-				return $link['href'];
-			}
-		}
-
-		return false;
-	}
-
-	public static function fetchprofile($url, $update = false)
-	{
-		if (empty($url)) {
-			return false;
-		}
-
-		if (!$update) {
-			$apcontact = DBA::selectFirst('apcontact', [], ['url' => $url]);
-			if (DBA::isResult($apcontact)) {
-				return $apcontact;
-			}
-
-			$apcontact = DBA::selectFirst('apcontact', [], ['alias' => $url]);
-			if (DBA::isResult($apcontact)) {
-				return $apcontact;
-			}
-
-			$apcontact = DBA::selectFirst('apcontact', [], ['addr' => $url]);
-			if (DBA::isResult($apcontact)) {
-				return $apcontact;
-			}
-		}
-
-		if (empty(parse_url($url, PHP_URL_SCHEME))) {
-			$url = self::addrToUrl($url);
-			if (empty($url)) {
-				return false;
-			}
-		}
-
-		$data = self::fetchContent($url);
-
-		if (empty($data) || empty($data['id']) || empty($data['inbox'])) {
-			return false;
-		}
-
-		$apcontact = [];
-		$apcontact['url'] = $data['id'];
-		$apcontact['uuid'] = defaults($data, 'uuid', null);
-		$apcontact['type'] = defaults($data, 'type', null);
-		$apcontact['following'] = defaults($data, 'following', null);
-		$apcontact['followers'] = defaults($data, 'followers', null);
-		$apcontact['inbox'] = defaults($data, 'inbox', null);
-		$apcontact['outbox'] = defaults($data, 'outbox', null);
-		$apcontact['sharedinbox'] = JsonLD::fetchElement($data, 'endpoints', 'sharedInbox');
-		$apcontact['nick'] = defaults($data, 'preferredUsername', null);
-		$apcontact['name'] = defaults($data, 'name', $apcontact['nick']);
-		$apcontact['about'] = defaults($data, 'summary', '');
-		$apcontact['photo'] = JsonLD::fetchElement($data, 'icon', 'url');
-		$apcontact['alias'] = JsonLD::fetchElement($data, 'url', 'href');
-
-		$parts = parse_url($apcontact['url']);
-		unset($parts['scheme']);
-		unset($parts['path']);
-		$apcontact['addr'] = $apcontact['nick'] . '@' . str_replace('//', '', Network::unparseURL($parts));
-
-		$apcontact['pubkey'] = trim(JsonLD::fetchElement($data, 'publicKey', 'publicKeyPem'));
-
-		// To-Do
-		// manuallyApprovesFollowers
-
-		// Unhandled
-		// @context, tag, attachment, image, nomadicLocations, signature, following, followers, featured, movedTo, liked
-
-		// Unhandled from Misskey
-		// sharedInbox, isCat
-
-		// Unhandled from Kroeg
-		// kroeg:blocks, updated
-
-		// Check if the address is resolvable
-		if (self::addrToUrl($apcontact['addr']) == $apcontact['url']) {
-			$parts = parse_url($apcontact['url']);
-			unset($parts['path']);
-			$apcontact['baseurl'] = Network::unparseURL($parts);
-		} else {
-			$apcontact['addr'] = null;
-		}
-
-		if ($apcontact['url'] == $apcontact['alias']) {
-			$apcontact['alias'] = null;
+	 *
+	 * @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;
 		}
 
-		$apcontact['updated'] = DateTimeFormat::utcNow();
-
-		DBA::update('apcontact', $apcontact, ['url' => $url], true);
-
-		return $apcontact;
+		return json_decode($ret['body'], true);
 	}
 
 	/**
@@ -660,7 +918,7 @@ class ActivityPub
 	 */
 	public static function probeProfile($url)
 	{
-		$apcontact = self::fetchprofile($url, true);
+		$apcontact = APContact::getByURL($url, true);
 		if (empty($apcontact)) {
 			return false;
 		}
@@ -693,6 +951,13 @@ class ActivityPub
 		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);
@@ -715,14 +980,20 @@ class ActivityPub
 
 		if (LDSignature::isSigned($activity)) {
 			$ld_signer = LDSignature::getSigner($activity);
-			if (!empty($ld_signer)) {
+			if (empty($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.', LOGGER_DEBUG);
+				logger('Invalid JSON-LD signature and the HTTP signer is different.', LOGGER_DEBUG);
 				$trust_source = false;
 			}
 		} elseif ($actor == $http_signer) {
@@ -736,6 +1007,12 @@ class ActivityPub
 		self::processActivity($activity, $body, $uid, $trust_source);
 	}
 
+	/**
+	 * @brief 
+	 *
+	 * @param $url
+	 * @param integer $uid User ID
+	 */
 	public static function fetchOutbox($url, $uid)
 	{
 		$data = self::fetchContent($url);
@@ -759,7 +1036,16 @@ class ActivityPub
 		}
 	}
 
-	private static function prepareObjectData($activity, $uid, $trust_source)
+	/**
+	 * @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)) {
@@ -779,42 +1065,34 @@ class ActivityPub
 
 		logger('Receivers: ' . json_encode($receivers), LOGGER_DEBUG);
 
-		if (is_string($activity['object'])) {
-			$object_url = $activity['object'];
-		} elseif (!empty($activity['object']['id'])) {
-			$object_url = $activity['object']['id'];
-		} else {
+		$object_id = JsonLD::fetchElement($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', 'Update', 'Announce'])) {
-			$object_data = self::fetchObject($object_url, $activity['object'], $trust_source);
+		if (in_array($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 [];
 			}
-		} elseif ($activity['type'] == 'Accept') {
-			$object_data = [];
-			$object_data['object_type'] = JsonLD::fetchElement($activity, 'object', 'type');
-			$object_data['object'] = JsonLD::fetchElement($activity, 'object', 'actor');
-		} elseif ($activity['type'] == 'Undo') {
-			$object_data = [];
-			$object_data['object_type'] = JsonLD::fetchElement($activity, 'object', 'type');
-			$object_data['object'] = JsonLD::fetchElement($activity, 'object', 'object');
+			// 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.
-			$object_data = self::processCommonData($activity);
+			$object_data = self::processObject($activity);
 			$object_data['name'] = $activity['type'];
 			$object_data['author'] = $activity['actor'];
-			$object_data['object'] = $object_url;
-		} elseif ($activity['type'] == 'Follow') {
-			$object_data['id'] = $activity['id'];
-			$object_data['object'] = $object_url;
+			$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);
@@ -823,9 +1101,19 @@ class ActivityPub
 		$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'])) {
@@ -844,20 +1132,17 @@ class ActivityPub
 
 		}
 
-		// Non standard
-		// title, atomUri, context_id, statusnetConversationId
-
-		// To-Do?
-		// context, location, signature;
-
-		logger('Processing activity: ' . $activity['type'], LOGGER_DEBUG);
-
+		// $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':
@@ -869,12 +1154,23 @@ class ActivityPub
 				break;
 
 			case 'Dislike':
+				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':
@@ -887,9 +1183,17 @@ class ActivityPub
 				}
 				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;
 
@@ -899,6 +1203,14 @@ class ActivityPub
 		}
 	}
 
+	/**
+	 * @brief 
+	 *
+	 * @param array $activity
+	 * @param $actor
+	 *
+	 * @return 
+	 */
 	private static function getReceivers($activity, $actor)
 	{
 		$receivers = [];
@@ -913,7 +1225,7 @@ class ActivityPub
 		}
 
 		if (!empty($actor)) {
-			$profile = self::fetchprofile($actor);
+			$profile = APContact::getByURL($actor);
 			$followers = defaults($profile, 'followers', '');
 
 			logger('Actor: ' . $actor . ' - Followers: ' . $followers, LOGGER_DEBUG);
@@ -922,25 +1234,25 @@ class ActivityPub
 			$followers = '';
 		}
 
-		$elements = ['to', 'cc', 'bto', 'bcc'];
-		foreach ($elements as $element) {
+		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) {
+				if ($receiver == self::PUBLIC_COLLECTION) {
 					$receivers['uid:0'] = 0;
 				}
 
-				if (($receiver == self::PUBLIC) && !empty($actor)) {
+				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]];
+					$condition = ['alias' => [$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) {
@@ -950,9 +1262,9 @@ class ActivityPub
 					DBA::close($contacts);
 				}
 
-				if (in_array($receiver, [$followers, self::PUBLIC]) && !empty($actor)) {
+				if (in_array($receiver, [$followers, self::PUBLIC_COLLECTION]) && !empty($actor)) {
 					$condition = ['nurl' => normalise_link($actor), 'rel' => [Contact::SHARING, Contact::FRIEND],
-						'network' => Protocol::ACTIVITYPUB];
+						'network' => Protocol::ACTIVITYPUB, 'archive' => false, 'pending' => false];
 					$contacts = DBA::select('contact', ['uid'], $condition);
 					while ($contact = DBA::fetch($contacts)) {
 						if ($contact['uid'] != 0) {
@@ -971,9 +1283,71 @@ class ActivityPub
 				$receivers['uid:' . $contact['uid']] = $contact['uid'];
 			}
 		}
+
+		self::switchContacts($receivers, $actor);
+
 		return $receivers;
 	}
 
+	/**
+	 * @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, $actor)
+	{
+		if (empty($actor)) {
+			return;
+		}
+
+		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);
+			}
+		}
+	}
+
+	/**
+	 * @brief 
+	 *
+	 * @param $object_data
+	 * @param array $activity
+	 *
+	 * @return 
+	 */
 	private static function addActivityFields($object_data, $activity)
 	{
 		if (!empty($activity['published']) && empty($object_data['published'])) {
@@ -994,18 +1368,27 @@ class ActivityPub
 		return $object_data;
 	}
 
-	private static function fetchObject($object_url, $object = [], $trust_source = false)
+	/**
+	 * @brief 
+	 *
+	 * @param $object_id
+	 * @param $object
+	 * @param $trust_source
+	 *
+	 * @return 
+	 */
+	private static function fetchObject($object_id, $object = [], $trust_source = false)
 	{
 		if (!$trust_source || is_string($object)) {
-			$data = self::fetchContent($object_url);
+			$data = self::fetchContent($object_id);
 			if (empty($data)) {
-				logger('Empty content for ' . $object_url . ', check if content is available locally.', LOGGER_DEBUG);
-				$data = $object_url;
+				logger('Empty content for ' . $object_id . ', check if content is available locally.', LOGGER_DEBUG);
+				$data = $object_id;
 			} else {
-				logger('Fetched content for ' . $object_url, LOGGER_DEBUG);
+				logger('Fetched content for ' . $object_id, LOGGER_DEBUG);
 			}
 		} else {
-			logger('Using original object for url ' . $object_url, LOGGER_DEBUG);
+			logger('Using original object for url ' . $object_id, LOGGER_DEBUG);
 			$data = $object;
 		}
 
@@ -1015,60 +1398,50 @@ class ActivityPub
 				logger('Object with url ' . $data . ' was not found locally.', LOGGER_DEBUG);
 				return false;
 			}
-			logger('Using already stored item for url ' . $object_url, LOGGER_DEBUG);
+			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'];
-			logger('Type ' . $type, LOGGER_DEBUG);
 		}
 
-		if (in_array($type, ['Note', 'Article', 'Video'])) {
-			$common = self::processCommonData($data);
+		if (in_array($data['type'], self::CONTENT_TYPES)) {
+			return self::processObject($data);
 		}
 
-		switch ($type) {
-			case 'Note':
-				return array_merge($common, self::processNote($data));
-			case 'Article':
-				return array_merge($common, self::processArticle($data));
-			case 'Video':
-				return array_merge($common, self::processVideo($data));
-
-			case 'Announce':
-				if (empty($data['object'])) {
-					return false;
-				}
-				return self::fetchObject($data['object']);
-
-			case 'Person':
-			case 'Tombstone':
-				break;
-
-			default:
-				logger('Unknown object type: ' . $data['type'], LOGGER_DEBUG);
-				break;
+		if ($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)
+	/**
+	 * @brief 
+	 *
+	 * @param $object
+	 *
+	 * @return 
+	 */
+	private static function processObject($object)
 	{
 		if (empty($object['id'])) {
 			return false;
 		}
 
 		$object_data = [];
-		$object_data['type'] = $object['type'];
-		$object_data['uri'] = $object['id'];
+		$object_data['object_type'] = $object['type'];
+		$object_data['id'] = $object['id'];
 
 		if (!empty($object['inReplyTo'])) {
-			$object_data['reply-to-uri'] = JsonLD::fetchElement($object, 'inReplyTo', 'id');
+			$object_data['reply-to-id'] = JsonLD::fetchElement($object, 'inReplyTo', 'id');
 		} else {
-			$object_data['reply-to-uri'] = $object_data['uri'];
+			$object_data['reply-to-id'] = $object_data['id'];
 		}
 
 		$object_data['published'] = defaults($object, 'published', null);
@@ -1078,8 +1451,13 @@ class ActivityPub
 			$object_data['published'] = $object_data['updated'];
 		}
 
-		$object_data['uuid'] = defaults($object, 'uuid', null);
-		$object_data['owner'] = $object_data['author'] = JsonLD::fetchElement($object, 'attributedTo', 'id');
+		$actor = JsonLD::fetchElement($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);
@@ -1095,39 +1473,21 @@ class ActivityPub
 		$object_data['alternate-url'] = JsonLD::fetchElement($object, 'url', 'href');
 		$object_data['receiver'] = self::getReceivers($object, $object_data['owner']);
 
+		// Common object data:
+
 		// Unhandled
 		// @context, type, actor, signature, mediaType, duration, replies, icon
 
 		// Also missing: (Defined in the standard, but currently unused)
 		// audience, preview, endTime, startTime, generator, image
 
-		return $object_data;
-	}
-
-	private static function processNote($object)
-	{
-		$object_data = [];
-
-		// To-Do?
-		// emoji, atomUri, inReplyToAtomUri
+		// Data in Notes:
 
 		// Unhandled
 		// contentMap, announcement_count, announcements, context_id, likes, like_count
 		// inReplyToStatusId, shares, quoteUrl, statusnetConversationId
 
-		return $object_data;
-	}
-
-	private static function processArticle($object)
-	{
-		$object_data = [];
-
-		return $object_data;
-	}
-
-	private static function processVideo($object)
-	{
-		$object_data = [];
+		// Data in video:
 
 		// To-Do?
 		// category, licence, language, commentsEnabled
@@ -1139,6 +1499,13 @@ class ActivityPub
 		return $object_data;
 	}
 
+	/**
+	 * @brief Converts mentions from Pleroma into the Friendica format
+	 *
+	 * @param string $body
+	 *
+	 * @return converted body
+	 */
 	private static function convertMentions($body)
 	{
 		$URLSearchString = "^\[\]";
@@ -1147,6 +1514,14 @@ class ActivityPub
 		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)) {
@@ -1160,11 +1535,6 @@ class ActivityPub
 					$tag_text .= ',';
 				}
 
-				if (empty($tag['href'])) {
-					//$tag['href']
-					logger('Blubb!');
-				}
-
 				$tag_text .= substr($tag['name'], 0, 1) . '[url=' . $tag['href'] . ']' . substr($tag['name'], 1) . '[/url]';
 			}
 		}
@@ -1174,6 +1544,14 @@ class ActivityPub
 		return $tag_text;
 	}
 
+	/**
+	 * @brief 
+	 *
+	 * @param $attachments
+	 * @param array $item
+	 *
+	 * @return item array
+	 */
 	private static function constructAttachList($attachments, $item)
 	{
 		if (empty($attachments)) {
@@ -1200,13 +1578,19 @@ class ActivityPub
 		return $item;
 	}
 
+	/**
+	 * @brief 
+	 *
+	 * @param array $activity
+	 * @param $body
+	 */
 	private static function createItem($activity, $body)
 	{
 		$item = [];
 		$item['verb'] = ACTIVITY_POST;
-		$item['parent-uri'] = $activity['reply-to-uri'];
+		$item['parent-uri'] = $activity['reply-to-id'];
 
-		if ($activity['reply-to-uri'] == $activity['uri']) {
+		if ($activity['reply-to-id'] == $activity['id']) {
 			$item['gravity'] = GRAVITY_PARENT;
 			$item['object-type'] = ACTIVITY_OBJ_NOTE;
 		} else {
@@ -1214,14 +1598,20 @@ class ActivityPub
 			$item['object-type'] = ACTIVITY_OBJ_COMMENT;
 		}
 
-		if (($activity['uri'] != $activity['reply-to-uri']) && !Item::exists(['uri' => $activity['reply-to-uri']])) {
-			logger('Parent ' . $activity['reply-to-uri'] . ' not found. Try to refetch it.');
-			self::fetchMissingActivity($activity['reply-to-uri'], $activity);
+		if (($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);
 		}
 
 		self::postItem($activity, $item, $body);
 	}
 
+	/**
+	 * @brief 
+	 *
+	 * @param array $activity
+	 * @param $body
+	 */
 	private static function likeItem($activity, $body)
 	{
 		$item = [];
@@ -1233,18 +1623,61 @@ class ActivityPub
 		self::postItem($activity, $item, $body);
 	}
 
+	/**
+	 * @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]);
+	}
+
+	/**
+	 * @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;
+		$item['object-type'] = ACTIVITY_OBJ_NOTE;
+
+		self::postItem($activity, $item, $body);
+	}
+
+	/**
+	 * @brief 
+	 *
+	 * @param array $activity
+	 * @param array $item
+	 * @param $body
+	 */
 	private static function postItem($activity, $item, $body)
 	{
 		/// @todo What to do with $activity['context']?
 
+		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;
+		}
+
 		$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['uri'];
+		$item['uri'] = $activity['id'];
 		$item['created'] = $activity['published'];
 		$item['edited'] = $activity['updated'];
-		$item['guid'] = $activity['uuid'];
+		$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']));
@@ -1262,6 +1695,7 @@ class ActivityPub
 
 		$item['protocol'] = Conversation::PARCEL_ACTIVITYPUB;
 		$item['source'] = $body;
+		$item['conversation-href'] = $activity['context'];
 		$item['conversation-uri'] = $activity['conversation'];
 
 		foreach ($activity['receiver'] as $receiver) {
@@ -1277,8 +1711,18 @@ class ActivityPub
 		}
 	}
 
+	/**
+	 * @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.');
@@ -1300,19 +1744,15 @@ class ActivityPub
 		logger('Activity ' . $url . ' had been fetched and processed.');
 	}
 
-	private static function getUserOfObject($object)
-	{
-		$self = DBA::selectFirst('contact', ['uid'], ['nurl' => normalise_link($object), 'self' => true]);
-		if (!DBA::isResult($self)) {
-			return false;
-		} else {
-			return $self['uid'];
-		}
-	}
-
+	/**
+	 * @brief perform a "follow" request
+	 *
+	 * @param array $activity
+	 */
 	private static function followUser($activity)
 	{
-		$uid = self::getUserOfObject($activity['object']);
+		$actor = JsonLD::fetchElement($activity, 'object', 'id');
+		$uid = User::getIdForURL($actor);
 		if (empty($uid)) {
 			return;
 		}
@@ -1344,9 +1784,56 @@ class ActivityPub
 		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 ($activity['object']['id'] != $activity['object']['actor']) {
+			logger('Object id does not match actor.', LOGGER_DEBUG);
+			return;
+		}
+
+		$contacts = DBA::select('contact', ['id'], ['nurl' => normalise_link($activity['object']['id'])]);
+		while ($contact = DBA::fetch($contacts)) {
+			Contact::remove($contact["id"]);
+		}
+		DBA::close($contacts);
+
+		logger('Deleted contact ' . $activity['object']['id'], LOGGER_DEBUG);
+	}
+
+	/**
+	 * @brief Accept a follow request
+	 *
+	 * @param array $activity
+	 */
 	private static function acceptFollowUser($activity)
 	{
-		$uid = self::getUserOfObject($activity['object']);
+		$actor = JsonLD::fetchElement($activity, 'object', 'actor');
+		$uid = User::getIdForURL($actor);
 		if (empty($uid)) {
 			return;
 		}
@@ -1371,9 +1858,69 @@ class ActivityPub
 		logger('Accept contact request from contact ' . $cid . ' for user ' . $uid, LOGGER_DEBUG);
 	}
 
+	/**
+	 * @brief Reject a follow request
+	 *
+	 * @param array $activity
+	 */
+	private static function rejectFollowUser($activity)
+	{
+		$actor = JsonLD::fetchElement($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);
+		}
+	}
+
+	/**
+	 * @brief Undo activity like "like" or "dislike"
+	 *
+	 * @param array $activity
+	 */
+	private static function undoActivity($activity)
+	{
+		$activity_url = JsonLD::fetchElement($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)
 	{
-		$uid = self::getUserOfObject($activity['object']);
+		$object = JsonLD::fetchElement($activity, 'object', 'object');
+		$uid = User::getIdForURL($object);
 		if (empty($uid)) {
 			return;
 		}