small changes

Threaded comments

activitypub.php

@@ -72,6 +72,7 @@ function plugin_init() {
 	\add_action( 'init', array( __NAMESPACE__ . '\Mention', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Health_Check', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Scheduler', 'init' ) );
+	\add_action( 'init', array( __NAMESPACE__ . '\Comments', 'init' ) );
 
 	if ( site_supports_blocks() ) {
 		\add_action( 'init', array( __NAMESPACE__ . '\Blocks', 'init' ) );

assets/js/activitypub-admin.js

@@ -17,4 +17,5 @@ jQuery( function( $ ) {
 			$( '.activate-now' ).removeClass( 'thickbox open-plugin-details-modal' );
 		}, 1200 );
 	} );
+
 } );

includes/class-activity-dispatcher.php

@@ -2,10 +2,13 @@
 namespace Activitypub;
 
 use WP_Post;
+use WP_Comment;
 use Activitypub\Activity\Activity;
 use Activitypub\Collection\Users;
 use Activitypub\Collection\Followers;
+use Activitypub\Transformer\Factory;
 use Activitypub\Transformer\Post;
+use Activitypub\Transformer\Comment;
 
 use function Activitypub\is_single_user;
 use function Activitypub\is_user_disabled;
@@ -30,12 +33,12 @@ class Activity_Dispatcher {
 	/**
 	 * Send Activities to followers and mentioned users or `Announce` (boost) a blog post.
 	 *
-	 * @param WP_Post $wp_post The ActivityPub Post.
+	 * @param mixed  $wp_object The ActivityPub Post.
 	 * @param string $type      The Activity-Type.
 	 *
 	 * @return void
 	 */
-	public static function send_activity_or_announce( WP_Post $wp_post, $type ) {
+	public static function send_activity_or_announce( $wp_object, $type ) {
 		// check if a migration is needed before sending new posts
 		Migration::maybe_migrate();
 
@@ -43,35 +46,35 @@ class Activity_Dispatcher {
 			return;
 		}
 
-		$wp_post->post_author = Users::BLOG_USER_ID;
+		$wp_object->post_author = Users::BLOG_USER_ID;
 
 		if ( is_single_user() ) {
-			self::send_activity( $wp_post, $type );
+			self::send_activity( $wp_object, $type );
 		} else {
-			self::send_announce( $wp_post, $type );
+			self::send_announce( $wp_object, $type );
 		}
 	}
 
 	/**
 	 * Send Activities to followers and mentioned users.
 	 *
-	 * @param WP_Post $wp_post The ActivityPub Post.
+	 * @param mixed  $wp_object The ActivityPub Post.
 	 * @param string $type      The Activity-Type.
 	 *
 	 * @return void
 	 */
-	public static function send_activity( WP_Post $wp_post, $type ) {
-		if ( is_user_disabled( $wp_post->post_author ) ) {
+	public static function send_activity( $wp_object, $type ) {
+		if ( is_user_disabled( $wp_object->post_author ) ) {
 			return;
 		}
 
-		$object = Post::transform( $wp_post )->to_object();
+		$object = Factory::get_transformer( $wp_object )->to_object();
 
 		$activity = new Activity();
 		$activity->set_type( $type );
 		$activity->set_object( $object );
 
-		$follower_inboxes  = Followers::get_inboxes( $wp_post->post_author );
+		$follower_inboxes  = Followers::get_inboxes( $wp_object->post_author );
 		$mentioned_inboxes = Mention::get_inboxes( $activity->get_cc() );
 
 		$inboxes = array_merge( $follower_inboxes, $mentioned_inboxes );
@@ -80,19 +83,19 @@ class Activity_Dispatcher {
 		$json = $activity->to_json();
 
 		foreach ( $inboxes as $inbox ) {
-			safe_remote_post( $inbox, $json, $wp_post->post_author );
+			safe_remote_post( $inbox, $json, $wp_object->post_author );
 		}
 	}
 
 	/**
 	 * Send Announces to followers and mentioned users.
 	 *
-	 * @param WP_Post $wp_post The ActivityPub Post.
+	 * @param mixed  $wp_object The ActivityPub Post.
 	 * @param string $type      The Activity-Type.
 	 *
 	 * @return void
 	 */
-	public static function send_announce( WP_Post $wp_post, $type ) {
+	public static function send_announce( $wp_object, $type ) {
 		if ( ! in_array( $type, array( 'Create', 'Update' ), true ) ) {
 			return;
 		}
@@ -101,7 +104,7 @@ class Activity_Dispatcher {
 			return;
 		}
 
-		$object = Post::transform( $wp_post )->to_object();
+		$object = Factory::get_transformer( $wp_object )->to_object();
 
 		$activity = new Activity();
 		$activity->set_type( 'Announce' );
@@ -110,7 +113,7 @@ class Activity_Dispatcher {
 		// send only the id
 		$activity->set_object( $object->get_id() );
 
-		$follower_inboxes  = Followers::get_inboxes( $wp_post->post_author );
+		$follower_inboxes  = Followers::get_inboxes( $wp_object->post_author );
 		$mentioned_inboxes = Mention::get_inboxes( $activity->get_cc() );
 
 		$inboxes = array_merge( $follower_inboxes, $mentioned_inboxes );
@@ -119,7 +122,7 @@ class Activity_Dispatcher {
 		$json = $activity->to_json();
 
 		foreach ( $inboxes as $inbox ) {
-			safe_remote_post( $inbox, $json, $wp_post->post_author );
+			safe_remote_post( $inbox, $json, $wp_object->post_author );
 		}
 	}
 }

includes/class-activitypub.php

@@ -4,6 +4,8 @@ namespace Activitypub;
 use Activitypub\Signature;
 use Activitypub\Collection\Users;
 
+use function Activitypub\is_comment;
+
 /**
  * ActivityPub Class
  *
@@ -92,6 +94,8 @@ class Activitypub {
 
 		if ( \is_author() ) {
 			$json_template = ACTIVITYPUB_PLUGIN_DIR . '/templates/author-json.php';
+		} elseif ( is_comment() ) {
+			$json_template = ACTIVITYPUB_PLUGIN_DIR . '/templates/comment-json.php';
 		} elseif ( \is_singular() ) {
 			$json_template = ACTIVITYPUB_PLUGIN_DIR . '/templates/post-json.php';
 		} elseif ( \is_home() ) {
@@ -114,6 +118,7 @@ class Activitypub {
 	 */
 	public static function add_query_vars( $vars ) {
 		$vars[] = 'activitypub';
+		$vars[] = 'replytocom';
 
 		return $vars;
 	}
@@ -189,10 +194,12 @@ class Activitypub {
 	 * @return string $url
 	 */
 	public static function remote_comment_link( $comment_link, $comment ) {
+		if ( ! is_admin() ) {
 			$remote_comment_link = get_comment_meta( $comment->comment_ID, 'source_url', true );
 			if ( $remote_comment_link ) {
 				$comment_link = esc_url( $remote_comment_link );
 			}
+		}
 		return $comment_link;
 	}
 

includes/class-comments.php

@@ -0,0 +1,118 @@
+<?php
+namespace Activitypub;
+
+/**
+ * Comments Class
+ *
+ * @author Django Doucet
+ */
+class Comments {
+	/**
+	 * Initialize the class, registering WordPress hooks.
+	 */
+	public static function init() {
+
+		\add_filter( 'preprocess_comment', array( self::class, 'preprocess_comment' ) );
+		\add_filter( 'comment_excerpt', array( self::class, 'comment_excerpt' ), 10, 3 );
+		\add_filter( 'comment_text', array( self::class, 'comment_content_filter' ), 10, 3 );
+		\add_filter( 'comment_post', array( self::class, 'postprocess_comment' ), 10, 3 );
+		\add_action( 'edit_comment', array( self::class, 'edit_comment' ), 20, 2 ); //schedule_admin_comment_activity
+	}
+
+	/**
+	 * preprocess local comments for federated replies
+	 */
+	public static function preprocess_comment( $commentdata ) {
+		// only process replies from authorized local actors, for ap enabled post types
+		if ( 0 === $commentdata['user_id'] ) {
+			return $commentdata;
+		}
+		$user = \get_userdata( $commentdata['user_id'] );
+		$comment_parent_post = \get_post_type( $commentdata['comment_post_ID'] );
+		$post_types = \get_option( 'activitypub_support_post_types', array( 'post', 'page' ) );
+
+		if ( $user->has_cap( 'publish_post', $commentdata['comment_post_ID'] ) && \in_array( $comment_parent_post, $post_types, true ) ) {
+			$commentdata['comment_meta']['protocol'] = 'activitypub';
+		}
+		return $commentdata;
+	}
+
+	/**
+	 * Filters the comment text to display webfinger in the Recently Published Dashboard Widget.
+	 * comment_excerpt( $comment_excerpt, $comment_id )
+	 *
+	 * doesn't work on received webfinger links as get_comment_excerpt strips tags
+	 * https://developer.wordpress.org/reference/functions/get_comment_excerpt/
+	 * @param string $comment_text
+	 * @param int $comment_id
+	 * @param array $args
+	 * @return void
+	 */
+	public static function comment_excerpt( $comment_excerpt, $comment_id ) {
+		$comment = get_comment( $comment_id );
+		$comment_excerpt = \apply_filters( 'the_content', $comment_excerpt, $comment );
+		return $comment_excerpt;
+	}
+
+	/**
+	 * comment_text( $comment )
+	 * Filters the comment text for display.
+	 *
+	 * @param string $comment_text
+	 * @param WP_Comment $comment
+	 * @param array $args
+	 * @return void
+	 */
+	public static function comment_content_filter( $comment_text, $comment, $args ) {
+		$comment_text = \apply_filters( 'the_content', $comment_text, $comment );
+		$protocol = \get_comment_meta( $comment->comment_ID, 'protocol', true );
+		// TODO Test if this is returned by Model/Comment
+		if ( 'activitypub' === $protocol ) {
+			$updated = \get_comment_meta( $comment->comment_ID, 'activitypub_last_modified', true );
+			if ( $updated ) {
+				$format = get_option( 'date_format' ) . ' ' . get_option( 'time_format' );
+				$formatted_datetime = \date_i18n( $format, \strtotime( $updated ) );
+				$iso_date = \wp_date( 'c', \strtotime( $updated ) );
+				$i18n_text = sprintf(
+					/* translators: %s: Displays comment last modified date and time */
+					__( '(Last edited on %s)', 'activitypub' ),
+					"<time class='modified' datetime='{$iso_date}'>$formatted_datetime</time>"
+				);
+				$comment_text .= "<small>$i18n_text<small>";
+			}
+		}
+		return $comment_text;
+	}
+
+	/**
+	 * comment_post()
+	 * postprocess_comment for federating replies and inbox-forwarding
+	 */
+	public static function postprocess_comment( $comment_id, $comment_approved, $commentdata ) {
+		//Administrator role users comments bypass transition_comment_status (auto approved)
+		$user = \get_userdata( $commentdata['user_id'] );
+		if (
+			( 1 === $comment_approved ) &&
+			\in_array( 'administrator', $user->roles )
+		) {
+			// Only needed for Admins (because of transition bypass)
+			$wp_comment = \get_comment( $comment_id );
+			\wp_schedule_single_event( \time(), 'activitypub_send_activity', array( $wp_comment, 'Create' ) );
+		}
+	}
+
+	/**
+	 * edit_comment()
+	 *
+	 * Fires immediately after a comment is updated in the database.
+	 * Fires immediately before comment status transition hooks are fired. (useful only for admin)
+	 */
+	public static function edit_comment( $comment_id, $commentdata ) {
+		update_comment_meta( $comment_id, 'activitypub_last_modified', \wp_date( 'Y-m-d H:i:s' ) );
+		$user = \get_userdata( $commentdata['user_id'] );
+		if ( \in_array( 'administrator', $user->roles ) ) {
+			$wp_comment = \get_comment( $comment_id );
+			\wp_schedule_single_event( \time(), 'activitypub_send_activity', array( $wp_comment, 'Update' ) );
+		}
+	}
+}

includes/class-hashtag.php

@@ -63,7 +63,7 @@ class Hashtag {
 				$tag = strtolower( $m[2] );
 				if ( '/' === $m[1] ) {
 					// Closing tag.
-					$i = array_search( $tag, $tag_stack );
+					$i = array_search( $tag, $tag_stack, true );
 					// We can only remove the tag from the stack if it is in the stack.
 					if ( false !== $i ) {
 						$tag_stack = array_slice( $tag_stack, 0, $i );

includes/class-scheduler.php

@@ -17,6 +17,7 @@ class Scheduler {
 	 */
 	public static function init() {
 		\add_action( 'transition_post_status', array( self::class, 'schedule_post_activity' ), 33, 3 );
+		\add_action( 'transition_comment_status', array( self::class, 'schedule_comment_activity' ), 20, 3 );
 
 		\add_action( 'activitypub_update_followers', array( self::class, 'update_followers' ) );
 		\add_action( 'activitypub_cleanup_followers', array( self::class, 'cleanup_followers' ) );
@@ -99,6 +100,36 @@ class Scheduler {
 		);
 	}
 
+	/**
+	 * Schedule Comment Activities
+	 *
+	 * transition_comment_status()
+	 *
+	 * @param string     $new_status New comment status.
+	 * @param string     $old_status Old comment status.
+	 * @param WP_Comment $comment    Comment object.
+	 */
+	public static function schedule_comment_activity( $new_status, $old_status, $comment ) {
+		$comment = get_comment( $comment );
+
+		if ( ! $comment->user_id ) {
+			// Registered comment author
+			return;
+		}
+
+		if ( 'approved' === $new_status && 'approved' !== $old_status ) {
+			// Only federate replies from local actors
+			$activity_object = unserialize( \get_comment_meta( $comment->comment_ID, 'ap_object', true ) );
+			if ( empty( $activity_object ) ) {
+				\wp_schedule_single_event( \time(), 'activitypub_send_activity', array( $comment, 'Create' ) );
+			}
+		} elseif ( 'trash' === $new_status ) {
+			\wp_schedule_single_event( \time(), 'activitypub_send_activity', array( $comment, 'Delete' ) );
+		} elseif ( 'update' === $new_status ) {
+			\wp_schedule_single_event( \time(), 'activitypub_send_activity', array( $comment, 'Update' ) );
+		}
+	}
+
 	/**
 	 * Update followers
 	 *

includes/functions.php

@@ -2,7 +2,9 @@
 namespace Activitypub;
 
 use WP_Error;
+use WP_Comment_Query;
 use Activitypub\Http;
+use Activitypub\Webfinger;
 use Activitypub\Activity\Activity;
 use Activitypub\Collection\Followers;
 
@@ -166,6 +168,161 @@ function url_to_authorid( $url ) {
 	return 0;
 }
 
+/**
+ * Examine a comment ID and look up an existing comment it represents.
+ *
+ * @param string $id ActivityPub object ID (usually a URL) to check.
+ *
+ * @return WP_Comment, or undef if no comment could be found.
+ */
+function object_id_to_comment( $id ) {
+	$comment_query = new WP_Comment_Query(
+		array(
+			'meta_key'   => 'source_id',
+			'meta_value' => $id,
+		)
+	);
+	if ( ! $comment_query->comments ) {
+		return;
+	}
+	if ( count( $comment_query->comments ) > 1 ) {
+		return;
+	}
+	return $comment_query->comments[0];
+}
+
+/**
+ * Examine an activity object and find the post that the specified URL field refers to.
+ *
+ * @param string $field_name The name of the URL field in the object to query.
+ *
+ * @return int Post ID, or null on failure.
+ */
+function object_to_post_id_by_field_name( $object, $field_name ) {
+	if ( ! isset( $object['object'][ $field_name ] ) ) {
+		return;
+	}
+	$result = \url_to_postid( $object['object'][ $field_name ] );
+	if ( $result > 0 ) {
+		return $result;
+	}
+}
+
+/**
+ * Verify if in_replyto_url is a local Post,
+ * (For backwards compatibility)
+ *
+ * @param string activitypub object id URI
+ * @return int post_id
+ */
+function url_to_postid( $in_replyto_url ) {
+	if ( ! empty( $in_replyto_url ) ) {
+		$tentative_postid = \url_to_postid( $in_replyto_url );
+		if ( is_null( $tentative_postid ) ) {
+			$post_types = \get_option( 'activitypub_support_post_types', array( 'post', 'page' ) );
+			$query_args = array(
+				'type' => $post_types,
+				'meta_query' => array(
+					array(
+						'key' => 'activitypub_canonical_url',
+						'value' => $in_replyto_url,
+					),
+				),
+			);
+			$posts_query = new \WP_Query();
+			$posts = $posts_query->query( $query_args );
+			$found_post_ids = array();
+			if ( $posts ) {
+				foreach ( $posts as $post ) {
+					$found_post_ids[] = $post->comment_ID;
+				}
+				return $found_post_ids[0];
+			}
+		} else {
+			return $tentative_postid;
+		}
+	}
+	return null;
+}
+
+/**
+ * Verify if in_replyto_url is a local comment,
+ * Or if it is a previously received remote comment
+ * (For threading comments locally)
+ *
+ * @param string activitypub object id URI
+ * @return int comment_id
+ */
+function url_to_commentid( $in_replyto_url ) {
+	if ( empty( $in_replyto_url ) ) {
+		return null;
+	}
+
+	//rewrite for activitypub object id simplification
+	$url_maybe_id = \wp_parse_url( $in_replyto_url );
+	if ( site_url() === $url_maybe_id['scheme'] . '://' . $url_maybe_id['host'] && ! empty( $url_maybe_id['query'] ) ) {
+		//is local post or comment
+		\parse_str( $url_maybe_id['query'], $reply_query );
+		if ( isset( $reply_query['replytocom'] ) ) {
+			//is local comment
+			return $reply_query['replytocom'];
+		}
+	} else {
+		//is remote url
+		//verify if in_replyto_url corresponds to a previously received comment
+		$comment_args = array(
+			'type' => 'activitypub',
+			'meta_query' => array(
+				array(
+					'key' => 'source_url', // $object['object']['id']
+					'value' => $in_replyto_url,
+				),
+			),
+		);
+		$comments_query = new WP_Comment_Query();
+		$comments = $comments_query->query( $comment_args );
+		$found_comment_ids = array();
+		if ( $comments ) {
+			foreach ( $comments as $comment ) {
+				$found_comment_ids[] = $comment->comment_ID;
+			}
+			return $found_comment_ids[0];
+		}
+	}
+	return null;
+}
+
+/**
+ * Verify if url is a wp_ap_comment,
+ * Or if it is a previously received remote comment
+ *
+ * @return int comment_id
+ */
+function is_comment() {
+	$comment_id = get_query_var( 'replytocom', null );
+	if ( ! is_null( $comment_id ) ) {
+		$comment = \get_comment( $comment_id );
+		// Only return local origin comments
+		if ( $comment->user_id ) {
+			return $comment_id;
+		}
+	}
+	return null;
+}
+
+/**
+ * @param string $user_url
+ * @return string $webfinger
+ */
+function url_to_webfinger( $user_url ) {
+	$user_url = \untrailingslashit( $user_url );
+	$user_url_array = \explode( '/', $user_url );
+	$user_name = \end( $user_url_array );
+	$url_host = \wp_parse_url( $user_url, PHP_URL_HOST );
+	$webfinger = '@' . $user_name . '@' . $url_host;
+	return $webfinger;
+}
+
 /**
  * Check for Tombstone Objects
  *

includes/rest/class-inbox.php

@@ -337,45 +337,82 @@ class Inbox {
 	}
 
 	/**
-	 * Handles "Create" requests
+	 * Converts a new ActivityPub object to comment data suitable for creating a comment
 	 *
-	 * @param  array $object  The activity-object
-	 * @param  int   $user_id The id of the local blog-user
+	 * @param  array $object  The activity-object.
+	 *
+	 * @return array Comment data suitable for creating a comment.
 	 */
-	public static function handle_create( $object, $user_id ) {
-		$meta = get_remote_metadata_by_actor( $object['actor'] );
-
+	public static function convert_object_to_comment_data( $object, $user_id ) {
+		$object['user_id'] = $user_id;
 		if ( ! isset( $object['object']['inReplyTo'] ) ) {
-			return;
+			return false;
 		}
 
 		// check if Activity is public or not
 		if ( ! self::is_activity_public( $object ) ) {
 			// @todo maybe send email
-			return;
+			return false;
 		}
 
-		$comment_post_id = \url_to_postid( $object['object']['inReplyTo'] );
+		$meta = \Activitypub\get_remote_metadata_by_actor( $object['actor'] );
 
-		// save only replys and reactions
+		$id = $object['object']['id'];
+
+		// Only handle replies
+		if ( ! isset( $object['object']['inReplyTo'] ) ) {
+			return false;
+		}
+		$in_reply_to = $object['object']['inReplyTo'];
+
+		// Comment already exists
+		if ( \Activitypub\object_id_to_comment( $id ) ) {
+			return false;
+		}
+
+		$parent_comment = \Activitypub\object_id_to_comment( $in_reply_to );
+
+		// save only replies and reactions
+		$comment_post_id = \Activitypub\object_to_post_id_by_field_name( $object, 'context' );
+		if ( ! $comment_post_id ) {
+			$comment_post_id = \Activitypub\object_to_post_id_by_field_name( $object, 'inReplyTo' );
+		}
+		if ( ! $comment_post_id ) {
+			$comment_post_id = $parent_comment->comment_post_ID;
+		}
 		if ( ! $comment_post_id ) {
 			return false;
 		}
 
-		$commentdata = array(
+		return array(
 			'comment_post_ID' => $comment_post_id,
 			'comment_author' => \esc_attr( $meta['name'] ),
 			'comment_author_url' => \esc_url_raw( $object['actor'] ),
 			'comment_content' => \wp_filter_kses( $object['object']['content'] ),
 			'comment_type' => 'comment',
 			'comment_author_email' => '',
-			'comment_parent' => 0,
+			'comment_parent' => $parent_comment ? $parent_comment->comment_ID : 0,
 			'comment_meta' => array(
+				'ap_object' => \serialize( $object ),
+				'source_id' => \esc_url_raw( $id ),
 				'source_url' => \esc_url_raw( $object['object']['url'] ),
 				'avatar_url' => \esc_url_raw( $meta['icon']['url'] ),
 				'protocol' => 'activitypub',
 			),
 		);
+	}
+
+	/**
+	 * Handles "Create" requests
+	 *
+	 * @param  array $object  The activity-object
+	 * @param  int   $user_id The id of the local blog-user
+	 */
+	public static function handle_create( $object, $user_id ) {
+		$commentdata = self::convert_object_to_comment_data( $object, $user_id );
+		if ( ! $commentdata ) {
+			return false;
+		}
 
 		// disable flood control
 		\remove_action( 'check_comment_flood', 'check_comment_flood_db', 10 );
@@ -401,6 +438,76 @@ class Inbox {
 		do_action( 'activitypub_handled_create', $object, $user_id, $state, $commentdata );
 	}
 
+	/**
+	 * Handles "Update" requests
+	 *
+	 * @param  array $object  The activity-object
+	 * @param  int   $user_id The id of the local blog-user
+	 */
+	public static function handle_update( $object, $user_id ) {
+		$meta = \Activitypub\get_remote_metadata_by_actor( $object['actor'] );
+
+		//Determine comment_ID
+		$object_comment_id = \Activitypub\url_to_commentid( \esc_url_raw( $object['object']['id'] ) );
+		if ( ! is_null( $object_comment_id ) ) {
+
+			//found a local comment id
+			$commentdata = \get_comment( $object_comment_id, ARRAY_A );
+			$commentdata['comment_author'] = \esc_attr( $meta['name'] ? $meta['name'] : $meta['preferredUsername'] );
+			$commentdata['comment_content'] = \wp_filter_kses( $object['object']['content'] );
+			$commentdata['comment_meta']['avatar_url'] = \esc_url_raw( $meta['icon']['url'] );
+			$commentdata['comment_meta']['ap_published'] = \wp_date( 'Y-m-d H:i:s', strtotime( $object['object']['published'] ) );
+			$commentdata['comment_meta']['activitypub_last_modified'] = $object['object']['updated'];
+			$commentdata['comment_meta']['ap_object'] = \serialize( $object );
+
+			// disable flood control
+			\remove_action( 'check_comment_flood', 'check_comment_flood_db', 10 );
+
+			// do not require email for AP entries
+			\add_filter( 'pre_option_require_name_email', '__return_false' );
+
+			$state = \wp_update_comment( $commentdata, true );
+
+			\remove_filter( 'pre_option_require_name_email', '__return_false' );
+
+			// re-add flood control
+			\add_action( 'check_comment_flood', 'check_comment_flood_db', 10, 4 );
+		}
+	}
+
+	/**
+	 * Handles "Delete" requests
+	 *
+	 * @param  array $object  The activity-object
+	 * @param  int   $user_id The id of the local blog-user
+	 */
+	public static function handle_delete( $object, $user_id ) {
+		if ( ! isset( $object['object']['id'] ) ) {
+			return;
+		}
+		//Determine comment_ID
+		$object_comment_id = \Activitypub\url_to_commentid( \esc_url_raw( $object['object']['id'] ) );
+		if ( ! is_null( $object_comment_id ) ) {
+
+			//found a local comment id
+			$commentdata = \get_comment( $object_comment_id, ARRAY_A );
+
+			// disable flood control
+			\remove_action( 'check_comment_flood', 'check_comment_flood_db', 10 );
+
+			// do not require email for AP entries
+			\add_filter( 'pre_option_require_name_email', '__return_false' );
+
+			// Should we trash or send back to moderation
+			$state = \wp_trash_comment( $commentdata['comment_ID'], true );
+
+			\remove_filter( 'pre_option_require_name_email', '__return_false' );
+
+			// re-add flood control
+			\add_action( 'check_comment_flood', 'check_comment_flood_db', 10, 4 );
+		}
+	}
+
 	/**
 	 * Extract recipient URLs from Activity object
 	 *

includes/transformer/class-comment.php

@@ -0,0 +1,299 @@
+<?php
+namespace Activitypub\Transformer;
+
+use WP_Comment;
+use Activitypub\Collection\Users;
+use Activitypub\Model\Blog_User;
+use Activitypub\Activity\Base_Object;
+use Activitypub\Hashtag;
+
+use function Activitypub\esc_hashtag;
+use function Activitypub\is_single_user;
+use function Activitypub\get_rest_url_by_path;
+
+/**
+ * WordPress Comment Transformer
+ *
+ * The Comment Transformer is responsible for transforming a WP_Comment object into different
+ * Object-Types.
+ *
+ * Currently supported are:
+ *
+ * - Activitypub\Activity\Base_Object
+ */
+class Comment {
+
+	/**
+	 * The WP_Comment object.
+	 *
+	 * @var WP_Comment
+	 */
+	protected $wp_comment;
+
+	/**
+	 * Static function to Transform a WP_Comment Object.
+	 *
+	 * This helps to chain the output of the Transformer.
+	 *
+	 * @param WP_Comment $wp_comment The WP_Comment object
+	 *
+	 * @return void
+	 */
+	public static function transform( WP_Comment $wp_comment ) {
+		return new static( $wp_comment );
+	}
+
+	/**
+	 *
+	 *
+	 * @param WP_Comment $wp_comment
+	 */
+	public function __construct( WP_Comment $wp_comment ) {
+		$this->wp_comment = $wp_comment;
+	}
+
+	/**
+	 * Transforms the WP_Comment object to an ActivityPub Object
+	 *
+	 * @see \Activitypub\Activity\Base_Object
+	 *
+	 * @return \Activitypub\Activity\Base_Object The ActivityPub Object
+	 */
+	public function to_object() {
+		$comment = $this->wp_comment;
+		$object = new Base_Object();
+
+		$object->set_id( $this->generate_id( $comment ) );
+		$object->set_url( \get_comment_link( $comment->ID ) );
+		$object->set_type( 'Note' );
+
+		$published = \strtotime( $comment->comment_date_gmt );
+		$object->set_published( \gmdate( 'Y-m-d\TH:i:s\Z', $published ) );
+
+		$updated = \get_comment_meta( $comment->comment_ID, 'activitypub_last_modified', true );
+		if ( $updated > $published ) {
+			$object->set_updated( \gmdate( 'Y-m-d\TH:i:s\Z', \strtotime( $updated ) ) );
+		}
+
+		$object->set_attributed_to( $this->get_attributed_to() );
+		$object->set_in_reply_to( $this->get_in_reply_to() );
+		$object->set_content( $this->get_content() );
+		$object->set_content_map(
+			array(
+				$this->get_locale() => $this->get_content(),
+			)
+		);
+		$path = sprintf( 'users/%d/followers', intval( $comment->comment_author ) );
+
+		$object->set_to(
+			array(
+				'https://www.w3.org/ns/activitystreams#Public',
+				get_rest_url_by_path( $path ),
+			)
+		);
+		$object->set_cc( $this->get_cc() );
+		$object->set_tag( $this->get_tags() );
+
+		return $object;
+	}
+
+	/**
+	 * Returns the User-URL of the Author of the Post.
+	 *
+	 * If `single_user` mode is enabled, the URL of the Blog-User is returned.
+	 *
+	 * @return string The User-URL.
+	 */
+	protected function get_attributed_to() {
+		if ( is_single_user() ) {
+			$user = new Blog_User();
+			return $user->get_url();
+		}
+
+		return Users::get_by_id( $this->wp_comment->user_id )->get_url();
+	}
+
+	/**
+	 * Returns the content for the ActivityPub Item.
+	 *
+	 * The content will be generated based on the user settings.
+	 *
+	 * @return string The content.
+	 */
+	protected function get_content() {
+		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+		$comment = $this->wp_comment;
+		$content = $comment->comment_content;
+
+		$content = \wpautop( $content );
+		$content = \preg_replace( '/[\n\r\t]/', '', $content );
+		$content = \trim( $content );
+		$content = \apply_filters( 'the_content', $content, $comment );
+
+		return $content;
+	}
+
+	/**
+	 * get_parent_uri (in reply to)
+	 * takes a comment and returns
+	 * @param WP_Comment activitypub object id URI
+	 * @return int comment_id
+	 */
+	protected function get_in_reply_to() {
+		$comment = $this->wp_comment;
+
+		$parent_comment = \get_comment( $comment->comment_parent );
+		if ( $parent_comment ) {
+			//is parent remote?
+			$in_reply_to = $this->get_source_id( $parent_comment );
+			if ( ! $in_reply_to ) {
+				//local
+				$in_reply_to = $this->generate_id( $parent_comment );
+			}
+		} else {
+			$pretty_permalink = \get_post_meta( $comment->comment_post_ID, 'activitypub_canonical_url', true );
+			if ( $pretty_permalink ) {
+				$in_reply_to = $pretty_permalink;
+			} else {
+				$in_reply_to = \get_permalink( $comment->comment_post_ID );
+			}
+		}
+		return $in_reply_to;
+	}
+
+	/**
+	 * @param $comment or $comment_id
+	 * @return ActivityPub URI of comment
+	 *
+	 * AP Object ID must be unique
+	 *
+	 * https://www.w3.org/TR/activitypub/#obj-id
+	 * https://github.com/tootsuite/mastodon/issues/13879
+	 */
+	protected function generate_id( $comment ) {
+
+		$comment = \get_comment( $comment );
+		$ap_comment_id = \add_query_arg(
+			array(
+				'p' => $comment->comment_post_ID,
+				'replytocom' => $comment->comment_ID,
+			),
+			\trailingslashit( site_url() )
+		);
+		return $ap_comment_id;
+	}
+
+	/**
+	 * Checks a comment ID for a source_id, or source_url
+	 */
+	protected function get_source_id( $comment ) {
+		if ( $comment->user_id ) {
+			return null;
+		}
+
+		$source_id = \get_comment_meta( $comment->comment_ID, 'source_id', true );
+		if ( ! $source_id ) {
+			$source_url = \get_comment_meta( $comment->comment_ID, 'source_url', true );
+			if ( ! $source_url ) {
+				return null;
+			}
+			$response = \safe_remote_get( $source_url );
+			$body = \wp_remote_retrieve_body( $response );
+			$remote_status = \json_decode( $body, true );
+			if ( \is_wp_error( $remote_status )
+				|| ! isset( $remote_status['@context'] )
+				|| ! isset( $remote_status['object']['id'] ) ) {
+					// the original post may have been deleted, before we started processing deletes.
+				return null;
+			}
+			$source_id = $remote_status['object']['id'];
+		}
+		return $source_id;
+	}
+
+	protected function get_context() {
+		$comment = $this->wp_comment;
+		$pretty_permalink = \get_post_meta( $comment->comment_post_ID, 'activitypub_canonical_url', true );
+		if ( $pretty_permalink ) {
+			$context = $pretty_permalink;
+		} else {
+			$context = \get_permalink( $comment->comment_post_ID );
+		}
+		return $context;
+	}
+
+	/**
+	 * Returns a list of Mentions, used in the Comment.
+	 *
+	 * @see https://docs.joinmastodon.org/spec/activitypub/#Mention
+	 *
+	 * @return array The list of Mentions.
+	 */
+	protected function get_cc() {
+		$cc = array();
+
+		$mentions = $this->get_mentions();
+		if ( $mentions ) {
+			foreach ( $mentions as $mention => $url ) {
+				$cc[] = $url;
+			}
+		}
+
+		return $cc;
+	}
+
+	/**
+	 * Returns a list of Tags, used in the Comment.
+	 *
+	 * This includes Hash-Tags and Mentions.
+	 *
+	 * @return array The list of Tags.
+	 */
+	protected function get_tags() {
+		$tags = array();
+
+		$mentions = $this->get_mentions();
+		if ( $mentions ) {
+			foreach ( $mentions as $mention => $url ) {
+				$tag = array(
+					'type' => 'Mention',
+					'href' => \esc_url( $url ),
+					'name' => \esc_html( $mention ),
+				);
+				$tags[] = $tag;
+			}
+		}
+
+		return $tags;
+	}
+
+	/**
+	 * Helper function to get the @-Mentions from the comment content.
+	 *
+	 * @return array The list of @-Mentions.
+	 */
+	protected function get_mentions() {
+		return apply_filters( 'activitypub_extract_mentions', array(), $this->wp_comment->comment_content, $this->wp_comment );
+	}
+
+	/**
+	 * Returns the locale of the post.
+	 *
+	 * @return string The locale of the post.
+	 */
+	public function get_locale() {
+		$comment_id = $this->wp_comment->ID;
+		$lang       = \strtolower( \strtok( \get_locale(), '_-' ) );
+
+		/**
+		 * Filter the locale of the comment.
+		 *
+		 * @param string  $lang    The locale of the comment.
+		 * @param int     $comment_id The comment ID.
+		 * @param WP_Post $post    The comment object.
+		 *
+		 * @return string The filtered locale of the comment.
+		 */
+		return apply_filters( 'activitypub_comment_locale', $lang, $comment_id, $this->wp_comment );
+	}
+}

includes/transformer/class-factory.php

@@ -0,0 +1,21 @@
+<?php
+namespace Activitypub\Transformer;
+
+use Activitypub\Transformer\Post;
+use Activitypub\Transformer\Comment;
+
+/**
+ * Transformer Factory
+ */
+class Factory {
+	public static function get_transformer( $object ) {
+		switch ( get_class( $object ) ) {
+			case 'WP_Post':
+				return new Post( $object );
+			case 'WP_Comment':
+				return new Comment( $object );
+			default:
+				return apply_filters( 'activitypub_transformer', null, $object, get_class( $object ) );
+		}
+	}
+}

includes/transformer/class-post.php

@@ -580,4 +580,63 @@ class Post {
 	protected function get_mentions() {
 		return apply_filters( 'activitypub_extract_mentions', array(), $this->wp_post->post_content, $this->wp_post );
 	}
+
+	/**
+	 * Get deleted datetime
+	 */
+	public function get_deleted() {
+		$post = $this->wp_post;
+		$deleted = null;
+		if ( 'trash' === $post->post_status ) {
+			$this->deleted = \gmdate( 'Y-m-d\TH:i:s\Z', \strtotime( $post->post_modified_gmt ) );
+		}
+		return $deleted;
+	}
+
+	public function get_replies() {
+		$replies = null;
+
+		$post = $this->wp_post;
+
+		if ( $post->comment_count > 0 ) {
+			$args = array(
+				'post_id' => $post->ID,
+				'hierarchical' => false,
+				'status'       => 'approve',
+			);
+			$comments = \get_comments( $args );
+			$items = array();
+
+			foreach ( $comments as $comment ) {
+				// include self replies
+				if ( $post->post_author === $comment->user_id ) {
+					$comment_url = \add_query_arg( //
+						array(
+							'p' => $post->ID,
+							'replytocom' => $comment->comment_ID,
+						),
+						trailingslashit( site_url() )
+					);
+					$items[] = $comment_url;
+				} else {
+					$comment_url = \get_comment_meta( $comment->comment_ID, 'source_url', true );
+					if ( ! empty( $comment_url ) ) {
+						$items[] = \get_comment_meta( $comment->comment_ID, 'source_url', true );
+					}
+				}
+			}
+
+			$replies = array(
+				'type'  => 'Collection',
+				'id'    => \add_query_arg( array( 'replies' => '' ), $this->get_id() ),
+				'first' => array(
+					'type'  => 'CollectionPage',
+					'partOf' => \add_query_arg( array( 'replies' => '' ), $this->get_id() ),
+					'items' => $items,
+				),
+			);
+		}
+
+		return $replies;
+	}
 }

templates/comment-json.php

@@ -0,0 +1,36 @@
+<?php
+$comment = \get_comment( \get_query_var( 'replytocom' ) ); // phpcs:ignore
+
+$object = new \Activitypub\Transformer\Comment( $comment );
+$json = \array_merge( array( '@context' => \Activitypub\get_context() ), $object->to_object()->to_array() );
+
+// filter output
+$json = \apply_filters( 'activitypub_json_comment_array', $json );
+
+/*
+ * Action triggerd prior to the ActivityPub profile being created and sent to the client
+ */
+\do_action( 'activitypub_json_comment_pre' );
+
+$options = 0;
+// JSON_PRETTY_PRINT added in PHP 5.4
+if ( \get_query_var( 'pretty' ) ) {
+	$options |= \JSON_PRETTY_PRINT; // phpcs:ignore
+}
+
+$options |= \JSON_HEX_TAG | \JSON_HEX_AMP | \JSON_HEX_QUOT;
+
+/*
+ * Options to be passed to json_encode()
+ *
+ * @param int $options The current options flags
+ */
+$options = \apply_filters( 'activitypub_json_comment_options', $options );
+
+\header( 'Content-Type: application/activity+json' );
+echo \wp_json_encode( $json, $options );
+
+/*
+ * Action triggerd after the ActivityPub profile has been created and sent to the client
+ */
+\do_action( 'activitypub_json_comment_comment' );

tests/test-class-inbox.php

@@ -0,0 +1,66 @@
+<?php
+class Test_Inbox extends WP_UnitTestCase {
+	public $post_permalink;
+	public $user_url;
+
+	public function set_up() {
+		$authordata = \get_userdata( 1 );
+		$this->user_url = $authordata->user_url;
+
+		$post = \wp_insert_post(
+			array(
+				'post_author' => 1,
+				'post_content' => 'test',
+			)
+		);
+		$this->post_permalink = \get_permalink( $post );
+
+		\add_filter( 'pre_get_remote_metadata_by_actor', array( '\Test_Inbox', 'get_remote_metadata_by_actor' ), 10, 2 );
+	}
+
+	public static function get_remote_metadata_by_actor( $value, $actor ) {
+		return array(
+			'name' => 'Example User',
+			'icon' => array(
+				'url' => 'https://example.com/icon',
+			),
+		);
+	}
+
+	public function test_convert_object_to_comment_data_basic() {
+		$object = array(
+			'actor' => $this->user_url,
+			'to' => [ $this->user_url ],
+			'cc' => [ 'https://www.w3.org/ns/activitystreams#Public' ],
+			'object' => array(
+				'id' => '123',
+				'url' => 'https://example.com/example',
+				'inReplyTo' => $this->post_permalink,
+				'content' => 'example',
+			),
+		);
+		$converted = \Activitypub\Rest\Inbox::convert_object_to_comment_data( $object, 1 );
+
+		$this->assertGreaterThan( 1, $converted['comment_post_ID'] );
+		$this->assertEquals( $converted['comment_author'], 'Example User' );
+		$this->assertEquals( $converted['comment_author_url'], 'http://example.org' );
+		$this->assertEquals( $converted['comment_content'], 'example' );
+		$this->assertEquals( $converted['comment_type'], 'comment' );
+		$this->assertEquals( $converted['comment_author_email'], '' );
+		$this->assertEquals( $converted['comment_parent'], 0 );
+		$this->assertArrayHasKey( 'comment_meta', $converted );
+		$this->assertEquals( $converted['comment_meta']['source_id'], 'http://123' );
+		$this->assertEquals( $converted['comment_meta']['source_url'], 'https://example.com/example' );
+		$this->assertEquals( $converted['comment_meta']['avatar_url'], 'https://example.com/icon' );
+		$this->assertEquals( $converted['comment_meta']['protocol'], 'activitypub' );
+	}
+
+	public function test_convert_object_to_comment_data_non_public_rejected() {
+		$object = array(
+			'to' => array( 'https://example.com/profile/test' ),
+			'cc' => array(),
+		);
+		$converted = \Activitypub\Rest\Inbox::convert_object_to_comment_data( $object, 1 );
+		$this->assertFalse( $converted );
+	}
+}