re-add mention functionality

not perfect but works as expected

includes/class-activity-dispatcher.php

@@ -67,7 +67,11 @@ class Activity_Dispatcher {
 		$activitypub_activity = new Activity( $activity_type );
 		$activitypub_activity->from_post( $activitypub_post );
 
-		$inboxes = Followers::get_inboxes( $user_id );
+		$follower_inboxes = Followers::get_inboxes( $user_id );
+		$mentioned_inboxes = Mention::get_inboxes( $activitypub_activity->get_cc() );
+
+		$inboxes = array_merge( $follower_inboxes, $mentioned_inboxes );
+		$inboxes = array_unique( $inboxes );
 
 		foreach ( $inboxes as $inbox ) {
 			$activity = $activitypub_activity->to_json();

includes/class-mention.php

@@ -1,6 +1,8 @@
 <?php
 namespace Activitypub;
 
+use WP_Error;
+
 /**
  * ActivityPub Mention Class
  *
@@ -57,10 +59,11 @@ class Mention {
 	 * A callback for preg_replace to build the user links
 	 *
 	 * @param array $result the preg_match results
+	 *
 	 * @return string the final string
 	 */
 	public static function replace_with_links( $result ) {
-		$metadata = \ActivityPub\get_remote_metadata_by_actor( $result[0] );
+		$metadata = get_remote_metadata_by_actor( $result[0], true );
 		if ( ! is_wp_error( $metadata ) && ! empty( $metadata['url'] ) ) {
 			$username = ltrim( $result[0], '@' );
 			if ( ! empty( $metadata['name'] ) ) {
@@ -76,17 +79,64 @@ class Mention {
 		return $result[0];
 	}
 
+	/**
+	 * Get the Inboxes for the mentioned Actors
+	 *
+	 * @param array $mentioned The list of Actors that were mentioned
+	 *
+	 * @return array The list of Inboxes
+	 */
+	public static function get_inboxes( $mentioned ) {
+		$inboxes = array();
+
+		foreach ( $mentioned as $actor ) {
+			$inbox = self::get_inbox_by_mentioned_actor( $actor );
+
+			if ( ! is_wp_error( $inbox ) && $inbox ) {
+				$inboxes[] = $inbox;
+			}
+		}
+
+		return $inboxes;
+	}
+
+	/**
+	 * Get the inbox from the Remote-Profile of a mentioned Actor
+	 *
+	 * @param string $actor The Actor-URL
+	 *
+	 * @return string The Inbox-URL
+	 */
+	public static function get_inbox_by_mentioned_actor( $actor ) {
+		$metadata = get_remote_metadata_by_actor( $actor, true );
+
+		if ( \is_wp_error( $metadata ) ) {
+			return $metadata;
+		}
+
+		if ( isset( $metadata['endpoints'] ) && isset( $metadata['endpoints']['sharedInbox'] ) ) {
+			return $metadata['endpoints']['sharedInbox'];
+		}
+
+		if ( \array_key_exists( 'inbox', $metadata ) ) {
+			return $metadata['inbox'];
+		}
+
+		return new WP_Error( 'activitypub_no_inbox', \__( 'No "Inbox" found', 'activitypub' ), $metadata );
+	}
+
 	/**
 	 * Extract the mentions from the post_content.
 	 *
 	 * @param array  $mentions The already found mentions.
 	 * @param string $post_content The post content.
+	 *
 	 * @return mixed The discovered mentions.
 	 */
 	public static function extract_mentions( $mentions, $post_content ) {
 		\preg_match_all( '/@' . ACTIVITYPUB_USERNAME_REGEXP . '/i', $post_content, $matches );
 		foreach ( $matches[0] as $match ) {
-			$link = \Activitypub\Webfinger::resolve( $match );
+			$link = Webfinger::resolve( $match );
 			if ( ! is_wp_error( $link ) ) {
 				$mentions[ $match ] = $link;
 			}

includes/functions.php

@@ -102,9 +102,12 @@ function get_webfinger_resource( $user_id ) {
  * Requests the Meta-Data from the Actors profile
  *
  * @param string $actor The Actor URL
+ * @param bool   $cache Enable/Disable caching of the meta.
+ *                      This does not effect Error-Caching.
+ *
  * @return array The Actor profile as array
  */
-function get_remote_metadata_by_actor( $actor ) {
+function get_remote_metadata_by_actor( $actor, $cache = false ) {
 	$pre = apply_filters( 'pre_get_remote_metadata_by_actor', false, $actor );
 	if ( $pre ) {
 		return $pre;
@@ -158,6 +161,10 @@ function get_remote_metadata_by_actor( $actor ) {
 	$metadata = \wp_remote_retrieve_body( $response );
 	$metadata = \json_decode( $metadata, true );
 
+	if ( true === $cache ) {
+		\set_transient( $transient_key, $metadata, WEEK_IN_SECONDS );
+	}
+
 	if ( ! $metadata ) {
 		$metadata = new \WP_Error( 'activitypub_invalid_json', \__( 'No valid JSON data', 'activitypub' ), $actor );
 		\set_transient( $transient_key, $metadata, HOUR_IN_SECONDS ); // Cache the error for a shorter period.