X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FProtocol%2FActivityPub%2FReceiver.php;h=6cd0111ec0f59e2d3df5a1d1f6064c9db86cf33e;hb=627e91f209a2ed5b1ab51c4accb05f072c4e287f;hp=f094833060255c7acb9fe85d7df1f00eb52b82d5;hpb=a364436623a09d155421077b37537b94364392b0;p=friendica.git

diff --git a/src/Protocol/ActivityPub/Receiver.php b/src/Protocol/ActivityPub/Receiver.php
index f094833060..6cd0111ec0 100644
--- a/src/Protocol/ActivityPub/Receiver.php
+++ b/src/Protocol/ActivityPub/Receiver.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * @copyright Copyright (C) 2010-2021, the Friendica project
+ * @copyright Copyright (C) 2010-2022, the Friendica project
  *
  * @license GNU AGPL version 3 or any later version
  *
@@ -27,6 +27,8 @@ use Friendica\Content\Text\HTML;
 use Friendica\Content\Text\Markdown;
 use Friendica\Core\Logger;
 use Friendica\Core\Protocol;
+use Friendica\Core\System;
+use Friendica\DI;
 use Friendica\Model\Contact;
 use Friendica\Model\APContact;
 use Friendica\Model\Item;
@@ -37,6 +39,7 @@ use Friendica\Protocol\ActivityPub;
 use Friendica\Util\HTTPSignature;
 use Friendica\Util\JsonLD;
 use Friendica\Util\LDSignature;
+use Friendica\Util\Network;
 use Friendica\Util\Strings;
 
 /**
@@ -56,7 +59,7 @@ class Receiver
 {
 	const PUBLIC_COLLECTION = 'as:Public';
 	const ACCOUNT_TYPES = ['as:Person', 'as:Organization', 'as:Service', 'as:Group', 'as:Application'];
-	const CONTENT_TYPES = ['as:Note', 'as:Article', 'as:Video', 'as:Image', 'as:Event', 'as:Audio'];
+	const CONTENT_TYPES = ['as:Note', 'as:Article', 'as:Video', 'as:Image', 'as:Event', 'as:Audio', 'as:Page', 'as:Question'];
 	const ACTIVITY_TYPES = ['as:Like', 'as:Dislike', 'as:Accept', 'as:Reject', 'as:TentativeAccept'];
 
 	const TARGET_UNKNOWN = 0;
@@ -68,16 +71,11 @@ class Receiver
 	const TARGET_ANSWER = 6;
 	const TARGET_GLOBAL = 7;
 
-	/**
-	 * Checks if the web request is done for the AP protocol
-	 *
-	 * @return bool is it AP?
-	 */
-	public static function isRequest()
-	{
-		return stristr($_SERVER['HTTP_ACCEPT'] ?? '', 'application/activity+json') ||
-			stristr($_SERVER['HTTP_ACCEPT'] ?? '', 'application/ld+json');
-	}
+	const COMPLETION_NONE    = 0;
+	const COMPLETION_ANNOUCE = 1;
+	const COMPLETION_RELAY   = 2;
+	const COMPLETION_MANUAL  = 3;
+	const COMPLETION_AUTO    = 4;
 
 	/**
 	 * Checks incoming message from the inbox
@@ -128,28 +126,28 @@ class Receiver
 		if (LDSignature::isSigned($activity)) {
 			$ld_signer = LDSignature::getSigner($activity);
 			if (empty($ld_signer)) {
-				Logger::log('Invalid JSON-LD signature from ' . $actor, Logger::DEBUG);
+				Logger::info('Invalid JSON-LD signature from ' . $actor);
 			} elseif ($ld_signer != $http_signer) {
 				$signer[] = $ld_signer;
 			}
 			if (!empty($ld_signer && ($actor == $http_signer))) {
-				Logger::log('The HTTP and the JSON-LD signature belong to ' . $ld_signer, Logger::DEBUG);
+				Logger::info('The HTTP and the JSON-LD signature belong to ' . $ld_signer);
 				$trust_source = true;
 			} elseif (!empty($ld_signer)) {
-				Logger::log('JSON-LD signature is signed by ' . $ld_signer, Logger::DEBUG);
+				Logger::info('JSON-LD signature is signed by ' . $ld_signer);
 				$trust_source = true;
 			} elseif ($actor == $http_signer) {
-				Logger::log('Bad JSON-LD signature, but HTTP signer fits the actor.', Logger::DEBUG);
+				Logger::info('Bad JSON-LD signature, but HTTP signer fits the actor.');
 				$trust_source = true;
 			} else {
-				Logger::log('Invalid JSON-LD signature and the HTTP signer is different.', Logger::DEBUG);
+				Logger::info('Invalid JSON-LD signature and the HTTP signer is different.');
 				$trust_source = false;
 			}
 		} elseif ($actor == $http_signer) {
-			Logger::log('Trusting post without JSON-LD signature, The actor fits the HTTP signer.', Logger::DEBUG);
+			Logger::info('Trusting post without JSON-LD signature, The actor fits the HTTP signer.');
 			$trust_source = true;
 		} else {
-			Logger::log('No JSON-LD signature, different actor.', Logger::DEBUG);
+			Logger::info('No JSON-LD signature, different actor.');
 			$trust_source = false;
 		}
 
@@ -201,7 +199,7 @@ class Receiver
 			return;
 		}
 
-		$id = Processor::fetchMissingActivity($object_id, [], $actor);
+		$id = Processor::fetchMissingActivity($object_id, [], $actor, self::COMPLETION_RELAY);
 		if (empty($id)) {
 			Logger::notice('Relayed message had not been fetched', ['id' => $object_id]);
 			return;
@@ -274,7 +272,9 @@ class Receiver
 	{
 		$id = JsonLD::fetchElement($activity, '@id');
 		if (!empty($id) && !$trust_source) {
-			$fetched_activity = ActivityPub::fetchContent($id, $uid ?? 0);
+			$fetch_uid = $uid ?: self::getBestUserForActivity($activity);
+
+			$fetched_activity = ActivityPub::fetchContent($id, $fetch_uid);
 			if (!empty($fetched_activity)) {
 				$object = JsonLD::compact($fetched_activity);
 				$fetched_id = JsonLD::fetchElement($object, '@id');
@@ -306,22 +306,28 @@ class Receiver
 			$reception_types[$data['uid']] = $data['type'] ?? self::TARGET_UNKNOWN;
 		}
 
+		$urls = self::getReceiverURL($activity);
+
 		// When it is a delivery to a personal inbox we add that user to the receivers
 		if (!empty($uid)) {
 			$additional = [$uid => $uid];
 			$receivers = array_replace($receivers, $additional);
 			if (empty($activity['thread-completion']) && (empty($reception_types[$uid]) || in_array($reception_types[$uid], [self::TARGET_UNKNOWN, self::TARGET_FOLLOWER, self::TARGET_ANSWER, self::TARGET_GLOBAL]))) {
 				$reception_types[$uid] = self::TARGET_BCC;
+				$owner = User::getOwnerDataById($uid);
+				if (!empty($owner['url'])) {
+					$urls['as:bcc'][] = $owner['url'];
+				}
 			}
-		} else {
-			// We possibly need some user to fetch private content,
-			// so we fetch the first out ot the list.
-			$uid = self::getFirstUserFromReceivers($receivers);
 		}
 
+		// We possibly need some user to fetch private content,
+		// so we fetch one out of the receivers if no uid is provided.
+		$fetch_uid = $uid ?: self::getBestUserForActivity($activity);
+
 		$object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
 		if (empty($object_id)) {
-			Logger::log('No object found', Logger::DEBUG);
+			Logger::info('No object found');
 			return [];
 		}
 
@@ -330,15 +336,38 @@ class Receiver
 			return [];
 		}
 
-		$object_type = self::fetchObjectType($activity, $object_id, $uid);
+		$object_type = self::fetchObjectType($activity, $object_id, $fetch_uid);
 
-		// Fetch the content only on activities where this matters
-		// We can receive "#emojiReaction" when fetching content from Hubzilla systems
-		if (in_array($type, ['as:Create', 'as:Update', 'as:Announce']) || strpos($type, '#emojiReaction')) {
+		// Fetch the activity on Lemmy "Announce" messages (announces of activities)
+		if (($type == 'as:Announce') && in_array($object_type, array_merge(self::ACTIVITY_TYPES, ['as:Delete', 'as:Undo', 'as:Update']))) {
+			$data = ActivityPub::fetchContent($object_id, $fetch_uid);
+			if (!empty($data)) {
+				$type = $object_type;
+				$activity = JsonLD::compact($data);
+
+				// Some variables need to be refetched since the activity changed
+				$actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
+				$object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
+				$object_type = self::fetchObjectType($activity, $object_id, $fetch_uid);
+			}
+		}
+
+		// Any activities on account types must not be altered
+		if (in_array($object_type, self::ACCOUNT_TYPES)) {
+			$object_data = [];
+			$object_data['id'] = JsonLD::fetchElement($activity, '@id');
+			$object_data['object_id'] = JsonLD::fetchElement($activity, 'as:object', '@id');
+			$object_data['object_actor'] = JsonLD::fetchElement($activity['as:object'], 'as:actor', '@id');
+			$object_data['object_object'] = JsonLD::fetchElement($activity['as:object'], 'as:object');
+			$object_data['object_type'] = JsonLD::fetchElement($activity['as:object'], '@type');
+			$object_data['push'] = $push;
+		} elseif (in_array($type, ['as:Create', 'as:Update', 'as:Announce', 'as:Invite']) || strpos($type, '#emojiReaction')) {
+			// Fetch the content only on activities where this matters
+			// We can receive "#emojiReaction" when fetching content from Hubzilla systems
 			// Always fetch on "Announce"
-			$object_data = self::fetchObject($object_id, $activity['as:object'], $trust_source && ($type != 'as:Announce'), $uid);
+			$object_data = self::fetchObject($object_id, $activity['as:object'], $trust_source && ($type != 'as:Announce'), $fetch_uid);
 			if (empty($object_data)) {
-				Logger::log("Object data couldn't be processed", Logger::DEBUG);
+				Logger::info("Object data couldn't be processed");
 				return [];
 			}
 
@@ -356,16 +385,16 @@ class Receiver
 			} else {
 				$object_data['directmessage'] = JsonLD::fetchElement($activity, 'litepub:directMessage');
 			}
-		} elseif (in_array($type, array_merge(self::ACTIVITY_TYPES, ['as:Follow'])) && in_array($object_type, self::CONTENT_TYPES)) {
+		} elseif (in_array($type, array_merge(self::ACTIVITY_TYPES, ['as:Follow', 'litepub:EmojiReact', 'as:View'])) && in_array($object_type, self::CONTENT_TYPES)) {
 			// 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.
+			// This way we later don't have to check for the existence of each individual array element.
 			$object_data = self::processObject($activity);
 			$object_data['name'] = $type;
 			$object_data['author'] = JsonLD::fetchElement($activity, 'as:actor', '@id');
 			$object_data['object_id'] = $object_id;
 			$object_data['object_type'] = ''; // Since we don't fetch the object, we don't know the type
 			$object_data['push'] = $push;
-		} elseif (in_array($type, ['as:Add'])) {
+		} elseif (in_array($type, ['as:Add', 'as:Remove'])) {
 			$object_data = [];
 			$object_data['id'] = JsonLD::fetchElement($activity, '@id');
 			$object_data['target_id'] = JsonLD::fetchElement($activity, 'as:target', '@id');
@@ -384,7 +413,7 @@ class Receiver
 
 			// An Undo is done on the object of an object, so we need that type as well
 			if (($type == 'as:Undo') && !empty($object_data['object_object'])) {
-				$object_data['object_object_type'] = self::fetchObjectType([], $object_data['object_object'], $uid);
+				$object_data['object_object_type'] = self::fetchObjectType([], $object_data['object_object'], $fetch_uid);
 			}
 		}
 
@@ -394,6 +423,12 @@ class Receiver
 			$object_data['object_type'] = $object_type;
 		}
 
+		foreach (['as:to', 'as:cc', 'as:bto', 'as:bcc'] as $element) {
+			if ((empty($object_data['receiver_urls'][$element]) || in_array($element, ['as:bto', 'as:bcc'])) && !empty($urls[$element])) {
+				$object_data['receiver_urls'][$element] = array_unique(array_merge($object_data['receiver_urls'][$element] ?? [], $urls[$element]));
+			}
+		}
+
 		$object_data['type'] = $type;
 		$object_data['actor'] = $actor;
 		$object_data['item_receiver'] = $receivers;
@@ -412,7 +447,7 @@ class Receiver
 			}
 		}
 
-		Logger::log('Processing ' . $object_data['type'] . ' ' . $object_data['object_type'] . ' ' . $object_data['id'], Logger::DEBUG);
+		Logger::info('Processing ' . $object_data['type'] . ' ' . $object_data['object_type'] . ' ' . $object_data['id']);
 
 		return $object_data;
 	}
@@ -437,10 +472,11 @@ class Receiver
 	 * Processes the activity object
 	 *
 	 * @param array   $activity     Array with activity data
-	 * @param string  $body
+	 * @param string  $body         The unprocessed body
 	 * @param integer $uid          User ID
 	 * @param boolean $trust_source Do we trust the source?
 	 * @param boolean $push         Message had been pushed to our system
+	 * @param array   $signer       The signer of the post
 	 * @throws \Exception
 	 */
 	public static function processActivity($activity, string $body = '', int $uid = null, bool $trust_source = false, bool $push = false, array $signer = [])
@@ -484,6 +520,12 @@ class Receiver
 			return;
 		}
 
+		// Lemmy is announcing activities.
+		// We are changing the announces into regular activities.
+		if (($type == 'as:Announce') && in_array($object_data['type'] ?? '', array_merge(self::ACTIVITY_TYPES, ['as:Delete', 'as:Undo', 'as:Update']))) {
+			$type = $object_data['type'];
+		}
+
 		if (!$trust_source) {
 			Logger::info('Activity trust could not be achieved.',  ['id' => $object_data['object_id'], 'type' => $type, 'signer' => $signer, 'actor' => $actor, 'attributedTo' => $attributed_to]);
 			return;
@@ -498,6 +540,14 @@ class Receiver
 			$object_data['thread-completion'] = $activity['thread-completion'];
 		}
 
+		if (!empty($activity['completion-mode'])) {
+			$object_data['completion-mode'] = $activity['completion-mode'];
+		}
+
+		if (!empty($activity['thread-children-type'])) {
+			$object_data['thread-children-type'] = $activity['thread-children-type'];
+		}
+
 		// Internal flag for posts that arrived via relay
 		if (!empty($activity['from-relay'])) {
 			$object_data['from-relay'] = $activity['from-relay'];
@@ -506,20 +556,43 @@ class Receiver
 		switch ($type) {
 			case 'as:Create':
 				if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+					if ($object_data['object_type'] == 'as:Question') {
+						self::storeUnhandledActivity(false, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
+					}
+					$item = ActivityPub\Processor::createItem($object_data);
+					ActivityPub\Processor::postItem($object_data, $item);
+				} elseif (in_array($object_data['object_type'], ['pt:CacheFile'])) {
+					// Unhandled Peertube activity
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
+				}
+				break;
+
+			case 'as:Invite':
+				if (in_array($object_data['object_type'], ['as:Event'])) {
 					$item = ActivityPub\Processor::createItem($object_data);
 					ActivityPub\Processor::postItem($object_data, $item);
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
 			case 'as:Add':
 				if ($object_data['object_type'] == 'as:tag') {
 					ActivityPub\Processor::addTag($object_data);
+				} elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+					ActivityPub\Processor::addToFeaturedCollection($object_data);
+				} elseif ($object_data['object_type'] == '') {
+					// The object type couldn't be determined. We don't have it and we can't fetch it. We ignore this activity.
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
 			case 'as:Announce':
 				if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 					$object_data['thread-completion'] = Contact::getIdForURL($actor);
+					$object_data['completion-mode']   = self::COMPLETION_ANNOUCE;
 
 					$item = ActivityPub\Processor::createItem($object_data);
 					if (empty($item)) {
@@ -541,24 +614,36 @@ class Receiver
 					}
 
 					ActivityPub\Processor::createActivity($announce_object_data, Activity::ANNOUNCE);
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
 			case 'as:Like':
 				if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 					ActivityPub\Processor::createActivity($object_data, Activity::LIKE);
+				} elseif ($object_data['object_type'] == '') {
+					// The object type couldn't be determined. We don't have it and we can't fetch it. We ignore this activity.
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
 			case 'as:Dislike':
 				if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 					ActivityPub\Processor::createActivity($object_data, Activity::DISLIKE);
+				} elseif ($object_data['object_type'] == '') {
+					// The object type couldn't be determined. We don't have it and we can't fetch it. We ignore this activity.
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
 			case 'as:TentativeAccept':
 				if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 					ActivityPub\Processor::createActivity($object_data, Activity::ATTENDMAYBE);
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
@@ -567,14 +652,40 @@ class Receiver
 					ActivityPub\Processor::updateItem($object_data);
 				} elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 					ActivityPub\Processor::updatePerson($object_data);
+				} elseif (in_array($object_data['object_type'], ['pt:CacheFile'])) {
+					// Unhandled Peertube activity
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
 			case 'as:Delete':
-				if ($object_data['object_type'] == 'as:Tombstone') {
+				if (in_array($object_data['object_type'], array_merge(['as:Tombstone'], self::CONTENT_TYPES))) {
 					ActivityPub\Processor::deleteItem($object_data);
 				} elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 					ActivityPub\Processor::deletePerson($object_data);
+				} elseif ($object_data['object_type'] == '') {
+					// The object type couldn't be determined. Most likely we don't have it here. We ignore this activity.
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
+				}
+				break;
+
+			case 'as:Block':
+				if (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
+					ActivityPub\Processor::blockAccount($object_data);
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
+				}
+				break;
+
+			case 'as:Remove':
+				if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+					ActivityPub\Processor::removeFromFeaturedCollection($object_data);					
+				} elseif ($object_data['object_type'] == '') {
+					// The object type couldn't be determined. We don't have it and we can't fetch it. We ignore this activity.
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
@@ -584,6 +695,8 @@ class Receiver
 				} elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 					$object_data['reply-to-id'] = $object_data['object_id'];
 					ActivityPub\Processor::createActivity($object_data, Activity::FOLLOW);
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
@@ -592,6 +705,8 @@ class Receiver
 					ActivityPub\Processor::acceptFollowUser($object_data);
 				} elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 					ActivityPub\Processor::createActivity($object_data, Activity::ATTEND);
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
@@ -600,6 +715,8 @@ class Receiver
 					ActivityPub\Processor::rejectFollowUser($object_data);
 				} elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 					ActivityPub\Processor::createActivity($object_data, Activity::ATTENDNO);
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
@@ -607,21 +724,146 @@ class Receiver
 				if (($object_data['object_type'] == 'as:Follow') &&
 					in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
 					ActivityPub\Processor::undoFollowUser($object_data);
+				} elseif (($object_data['object_type'] == 'as:Follow') &&
+					in_array($object_data['object_object_type'], self::CONTENT_TYPES)) {
+					ActivityPub\Processor::undoActivity($object_data);
 				} elseif (($object_data['object_type'] == 'as:Accept') &&
 					in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
 					ActivityPub\Processor::rejectFollowUser($object_data);
-				} elseif (in_array($object_data['object_type'], self::ACTIVITY_TYPES) &&
-					in_array($object_data['object_object_type'], self::CONTENT_TYPES)) {
+				} elseif (($object_data['object_type'] == 'as:Block') &&
+					in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
+					ActivityPub\Processor::unblockAccount($object_data);
+				} elseif (in_array($object_data['object_type'], array_merge(self::ACTIVITY_TYPES, ['as:Announce'])) &&
+					in_array($object_data['object_object_type'], array_merge(['as:Tombstone'], self::CONTENT_TYPES))) {
 					ActivityPub\Processor::undoActivity($object_data);
+				} elseif (in_array($object_data['object_type'], array_merge(self::ACTIVITY_TYPES, ['as:Announce', 'as:Create', ''])) &&
+					empty($object_data['object_object_type'])) {
+					// We cannot detect the target object. So we can ignore it.
+				} elseif (in_array($object_data['object_type'], ['as:Create']) &&
+					in_array($object_data['object_object_type'], ['pt:CacheFile'])) {
+					// Unhandled Peertube activity
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				}
 				break;
 
+			case 'as:View':
+				if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+					ActivityPub\Processor::createActivity($object_data, Activity::VIEW);
+				} elseif ($object_data['object_type'] == '') {
+					// The object type couldn't be determined. Most likely we don't have it here. We ignore this activity.
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
+				}
+				break;
+
+			case 'litepub:EmojiReact':
+				if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+					ActivityPub\Processor::createActivity($object_data, Activity::EMOJIREACT);
+				} elseif ($object_data['object_type'] == '') {
+					// The object type couldn't be determined. We don't have it and we can't fetch it. We ignore this activity.
+				} else {
+					self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
+				}
+				break;
+	
 			default:
-				Logger::log('Unknown activity: ' . $type . ' ' . $object_data['object_type'], Logger::DEBUG);
+				Logger::info('Unknown activity: ' . $type . ' ' . $object_data['object_type']);
+				self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
 				break;
 		}
 	}
 
+	/**
+	 * Stores unhandled or unknown Activities as a file
+	 *
+	 * @param boolean $unknown      "true" if the activity is unknown, "false" if it is unhandled
+	 * @param string  $type         Activity type
+	 * @param array   $object_data  Preprocessed array that is generated out of the received activity
+ 	 * @param array   $activity     Array with activity data
+	 * @param string  $body         The unprocessed body
+	 * @param integer $uid          User ID
+	 * @param boolean $trust_source Do we trust the source?
+	 * @param boolean $push         Message had been pushed to our system
+	 * @param array   $signer       The signer of the post
+	 * @return void
+	 */
+	private static function storeUnhandledActivity(bool $unknown, string $type, array $object_data, array $activity, string $body = '', int $uid = null, bool $trust_source = false, bool $push = false, array $signer = [])
+	{
+		if (!DI::config()->get('debug', 'ap_log_unknown')) {
+			return;
+		}
+
+		$file = ($unknown  ? 'unknown-' : 'unhandled-') . str_replace(':', '-', $type) . '-';
+	
+		if (!empty($object_data['object_type'])) {
+			$file .= str_replace(':', '-', $object_data['object_type']) . '-';
+		}
+
+		if (!empty($object_data['object_object_type'])) {
+			$file .= str_replace(':', '-', $object_data['object_object_type']) . '-';
+		}
+
+		$tempfile = tempnam(System::getTempPath(), $file);
+		file_put_contents($tempfile, json_encode(['activity' => $activity, 'body' => $body, 'uid' => $uid, 'trust_source' => $trust_source, 'push' => $push, 'signer' => $signer, 'object_data' => $object_data], JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT));
+		Logger::notice('Unknown activity stored', ['type' => $type, 'object_type' => $object_data['object_type'], $object_data['object_object_type'] ?? '', 'file' => $tempfile]);
+	}
+
+	/**
+	 * Fetch a user id from an activity array
+	 *
+	 * @param array  $activity
+	 * @param string $actor
+	 *
+	 * @return int   user id
+	 */
+	public static function getBestUserForActivity(array $activity)
+	{
+		$uid = 0;
+		$actor = JsonLD::fetchElement($activity, 'as:actor', '@id') ?? '';
+
+		$receivers = self::getReceivers($activity, $actor);
+		foreach ($receivers as $receiver) {
+			if ($receiver['type'] == self::TARGET_GLOBAL) {
+				return 0;
+			}
+			if (empty($uid) || ($receiver['type'] == self::TARGET_TO)) {
+				$uid = $receiver['uid'];
+			}
+		}
+
+		// When we haven't found any user yet, we just chose a user who most likely could have access to the content
+		if (empty($uid)) {
+			$contact = Contact::selectFirst(['uid'], ['nurl' => Strings::normaliseLink($actor), 'rel' => [Contact::SHARING, Contact::FRIEND]]);
+			if (!empty($contact['uid'])) {
+				$uid = $contact['uid'];
+			}
+		}
+
+		return $uid;
+	}
+
+	public static function getReceiverURL($activity)
+	{
+		$urls = [];
+
+		foreach (['as:to', 'as:cc', 'as:bto', 'as:bcc'] as $element) {
+			$receiver_list = JsonLD::fetchElementArray($activity, $element, '@id');
+			if (empty($receiver_list)) {
+				continue;
+			}
+
+			foreach ($receiver_list as $receiver) {
+				if ($receiver == self::PUBLIC_COLLECTION) {
+					$receiver = ActivityPub::PUBLIC_COLLECTION;
+				}
+				$urls[$element][] = $receiver;
+			}
+		}
+
+		return $urls;
+	}
+
 	/**
 	 * Fetch the receiver list from an activity array
 	 *
@@ -932,16 +1174,16 @@ class Receiver
 			$data = ActivityPub::fetchContent($object_id, $uid);
 			if (!empty($data)) {
 				$object = JsonLD::compact($data);
-				Logger::log('Fetched content for ' . $object_id, Logger::DEBUG);
+				Logger::info('Fetched content for ' . $object_id);
 			} else {
-				Logger::log('Empty content for ' . $object_id . ', check if content is available locally.', Logger::DEBUG);
+				Logger::info('Empty content for ' . $object_id . ', check if content is available locally.');
 
 				$item = Post::selectFirst(Item::DELIVER_FIELDLIST, ['uri' => $object_id]);
 				if (!DBA::isResult($item)) {
-					Logger::log('Object with url ' . $object_id . ' was not found locally.', Logger::DEBUG);
+					Logger::info('Object with url ' . $object_id . ' was not found locally.');
 					return false;
 				}
-				Logger::log('Using already stored item for url ' . $object_id, Logger::DEBUG);
+				Logger::info('Using already stored item for url ' . $object_id);
 				$data = ActivityPub\Transmitter::createNote($item);
 				$object = JsonLD::compact($data);
 			}
@@ -957,7 +1199,7 @@ class Receiver
 				return false;
 			}
 		} else {
-			Logger::log('Using original object for url ' . $object_id, Logger::DEBUG);
+			Logger::info('Using original object for url ' . $object_id);
 		}
 
 		$type = JsonLD::fetchElement($object, '@type');
@@ -966,6 +1208,18 @@ class Receiver
 			return false;
 		}
 
+		// Lemmy is resharing "create" activities instead of content
+		// We fetch the content from the activity.
+		if (in_array($type, ['as:Create'])) {
+			$object = $object['as:object'];
+			$type = JsonLD::fetchElement($object, '@type');
+			if (empty($type)) {
+				Logger::info('Empty type');
+				return false;
+			}
+			$object_data = self::processObject($object);
+		}
+
 		// We currently don't handle 'pt:CacheFile', but with this step we avoid logging
 		if (in_array($type, self::CONTENT_TYPES) || ($type == 'pt:CacheFile')) {
 			$object_data = self::processObject($object);
@@ -984,7 +1238,7 @@ class Receiver
 			return self::fetchObject($object_id, [], false, $uid);
 		}
 
-		Logger::log('Unhandled object type: ' . $type, Logger::DEBUG);
+		Logger::info('Unhandled object type: ' . $type);
 		return false;
 	}
 
@@ -1185,6 +1439,59 @@ class Receiver
 		return $attachlist;
 	}
 
+	/**
+	 * Convert questions from JSON-LD format into a simplified format
+	 *
+	 * @param array $object
+	 *
+	 * @return array Questions in a simplified format
+	 */
+	private static function processQuestion(array $object)
+	{
+		$question = [];
+
+		if (!empty($object['as:oneOf'])) {
+			$question['multiple'] = false;
+			$options = JsonLD::fetchElementArray($object, 'as:oneOf') ?? [];
+		} elseif (!empty($object['as:anyOf'])) {
+			$question['multiple'] = true;
+			$options = JsonLD::fetchElementArray($object, 'as:anyOf') ?? [];
+		} else {
+			return [];
+		}
+
+		// @todo Check if "closed" is a thing, see here: https://www.w3.org/TR/activitystreams-vocabulary/#dfn-closed
+		$question['voters']  = (int)JsonLD::fetchElement($object, 'toot:votersCount', '@value');
+		$question['options'] = [];
+
+		$voters = 0;
+
+		foreach ($options as $option) {
+			if (JsonLD::fetchElement($option, '@type') != 'as:Note') {
+				continue;
+			}
+
+			$name = JsonLD::fetchElement($option, 'as:name', '@value');
+
+			if (empty($option['as:replies'])) {
+				continue;
+			}
+
+			$replies = JsonLD::fetchElement($option['as:replies'], 'as:totalItems', '@value');
+
+			$question['options'][] = ['name' => $name, 'replies' => $replies];
+
+			$voters += (int)$replies;
+		}
+
+		// For single choice question we can count the number of voters if not provided (like with Misskey)
+		if (empty($question['voters']) && !$question['multiple']) {
+			$question['voters'] = $voters;
+		}
+
+		return $question;
+	}
+
 	/**
 	 * Fetch the original source or content with the "language" Markdown or HTML
 	 *
@@ -1340,6 +1647,14 @@ class Receiver
 		// An empty "id" field is translated to "./" by the compactor, so we have to check for this content
 		if (empty($object_data['reply-to-id']) || ($object_data['reply-to-id'] == './')) {
 			$object_data['reply-to-id'] = $object_data['id'];
+
+			// On activities the "reply to" is the id of the object it refers to
+			if (in_array($object_data['object_type'], self::ACTIVITY_TYPES)) {
+				$object_id = JsonLD::fetchElement($object, 'as:object', '@id');
+				if (!empty($object_id)) {
+					$object_data['reply-to-id'] = $object_id;
+				}
+			}
 		} else {
 			// Some systems (e.g. GNU Social) don't reply to the "id" field but the "uri" field.
 			$replyToId = Item::getURIByLink($object_data['reply-to-id']);
@@ -1389,7 +1704,6 @@ class Receiver
 		$object_data = self::getSource($object, $object_data);
 		$object_data['start-time'] = JsonLD::fetchElement($object, 'as:startTime', '@value');
 		$object_data['end-time'] = JsonLD::fetchElement($object, 'as:endTime', '@value');
-		$object_data['adjust'] = JsonLD::fetchElement($object, 'dfrn:adjust', '@value');
 		$object_data['location'] = $location;
 		$object_data['latitude'] = JsonLD::fetchElement($object, 'as:location', 'as:latitude', '@type', 'as:Place');
 		$object_data['latitude'] = JsonLD::fetchElement($object_data, 'latitude', '@value');
@@ -1412,11 +1726,27 @@ class Receiver
 			}
 		}
 
+		if (!empty($object_data['alternate-url']) && !Network::isValidHttpUrl($object_data['alternate-url'])) {
+			$object_data['alternate-url'] = null;
+		}
+
 		if (in_array($object_data['object_type'], ['as:Audio', 'as:Video'])) {
 			$object_data['alternate-url'] = self::extractAlternateUrl($object['as:url'] ?? []) ?: $object_data['alternate-url'];
 			$object_data['attachments'] = array_merge($object_data['attachments'], self::processAttachmentUrls($object['as:url'] ?? []));
 		}
 
+		// For page types we expect that the alternate url posts to some page.
+		// So we add this to the attachments if it differs from the id.
+		// Currently only Lemmy is using the page type.
+		if (($object_data['object_type'] == 'as:Page') && !empty($object_data['alternate-url']) && !Strings::compareLink($object_data['alternate-url'], $object_data['id'])) {
+			$object_data['attachments'][] = ['url' => $object_data['alternate-url']];
+			$object_data['alternate-url'] = null;
+		}
+
+		if ($object_data['object_type'] == 'as:Question') {
+			$object_data['question'] = self::processQuestion($object);
+		}
+
 		$receiverdata = self::getReceivers($object, $object_data['actor'], $object_data['tags'], true);
 		$receivers = $reception_types = [];
 		foreach ($receiverdata as $key => $data) {
@@ -1424,7 +1754,8 @@ class Receiver
 			$reception_types[$data['uid']] = $data['type'] ?? 0;
 		}
 
-		$object_data['receiver'] = $receivers;
+		$object_data['receiver_urls']  = self::getReceiverURL($object);
+		$object_data['receiver']       = $receivers;
 		$object_data['reception_type'] = $reception_types;
 
 		$object_data['unlisted'] = in_array(-1, $object_data['receiver']);