Comment Federation (#550)

* Comments 1

* Delete FUNDING.yml

* Add basic BuddyPress support

fix #122

thanks and props @skysarwer

* change URL to `bp_core_get_user_domain`

* fix "Follow" issue

fix #133

* fix #135

* version bump

* Create phpunit.yml

* Update composer.json

* Update composer.json

* Update phpunit.yml

* Update composer.json

* Create phpcs.yml

* Update phpcs.xml

* Update composer.json

* phpcs fixes

* fix typo

* Comments update

* webfinger_extract remove extra param

* coding standards

* Replies Collection, settings, other fixes

* Create stale.yml

* move stale file

* code standards cleanup

* Migrate / Update script

* bugfix

* add settings link to plugin page

* fix code standards

* fix cs

* fix PHPCS

* PHPCS fixes

* change background image for wp.org

* fix docker

* fix webfinger for email identifiers

fix #152

* version bump

* update composer file to fix unit testing

* allow plugins

* fix dependencies

* Migrate tools

* code cleanup

* regression fix

* Fix announce, clarified language

* update included filename

* code cleanup

* Improve migration UX

* Add comments view, warnings to migrate page

* style fix

* more style fixes

* Fix send_delete_activity

* replace ap_comment_id to reuse  replytocom var

* Comments class missing attributes

* Post class fix attributes

* move js file to assets/js

* Separate file for Comment processing hooks

* fix file path

* associate comments to back compat post

* Fix js assets enqueue

* change regex matching potential hashtags

Matches any string starting with '#' and consisting of any number and combination of [A-Za-z0-9_] that is directly followed by whitespace or punctuation. Groups everything after '#' for access in functions using this regex.

This fixes #183 (incomplete links on hashtags containing special characters) by not matching these at all.

* also detect hashtags at the start of a paragraph

* restrict html tags after which to detect a hashtag

Hashtags should not be detected after just any html tag - for example not after an opening a or div. To still allow detection at the start of a line, allow specifically p and br to directly precede a hashtag.

* fix pagination

* Add Custom Post Type support to outbox API

* remove comment_type

* fix comparison

* remove trailing spaces

* fix phpcs issues

* fix phpcs issues

* run phpcs also on pull_requests

* fix phpcs issues

* support threaded comments from ActivityPub

* refactor support for threaded comments from ActivityPub

* remove debugging log line

* add first unit tests for class inbox

* fix code smells

* make filter function static

* attempt to resolve backwards compatibility issues

* update js to new file

* delete old js

* Remove migrate code

* update post meta canonical

* remove type and mention meta from comment filters

* extract mentions from comment_content

* phpcbf

* remove extra curly bracket

* Remove migrate code

* remove version_check()

* Update enqueue scripts

* Remove remote comments from preprocessing

* Reply to comments from Dashboard

* rename function, inserts users into reply text

* Update dispatch comments

* update comment model

* fix comment model replies property

* fix preprocess_comment cap check

* Add webfinger filter to comments

* Add comment edit datetime

* cleanup

* fix var name

* cleanup

* phpcbf

* better actual translation support

* Separate comment reply script

* migrate dispatch, migrate comment model to transform

* ignore WP_Comment type for now

* Adds new helpers for resolving inReplyTo url

* Update activitypub_send_comment_activity to include type

* remove redundant id check

* reinclude user_id in saved ap_object meta

* update post field meta

* Fix comment updated datetime

* front-end reply inserts @mentions

* enqueue reply script on front end

* use const instead of dirname

* some simplifications

* move some functions

* fixes

* some more fixes

* fix namespace

* fix unittests

* fix testcase

* fixed typo

* fix tests

* fix tests

* fix PHPCS

* move functions to transformer class

* fix warnings

* Link remote comments on frontend

* Link to comment source as row action

* Init Comments class

* remove dead dispatch action

* re-add extract mentions filter

* Restore and tweak Comment transform

* Schedule comments activities for non-admin users

* lint

* remove context property

* rename get_id method to generate_id

* fix locale

* move functions

* PHPDoc

* this is never used

* remove some edit methods

* remove replies for now

* remove JS calls

* remove reply_recipients

* never used

* remove other query-vars

* otherwise to_json would not work properly

* small changes

* use `c` for comment IDs

* remove comments.php for now

maybe re-add it later

* wp_insert_post is an action

* also parse comment_text

* remove duplicate functions

* add Base transformer

* remove invalid test

* update to new query var

* update dispatcher to support comments and posts

* fix transition

* remove unused functions for now

* schedule_comment_activity seems to ignore create and update

* fix wrong use of functions!

* not every platforms sends an URL

* check source-id first

* remove hashtags for now

* fallback to ID

* fix typo

* move to_activity to Base class

* remove unused function

* add support for announce and like

* also ping inboxes of other commenters in the thread

* restructure WebFinger class

* some small improvements

* simplified to_object class

props @Menrath for the feedback and the idea!

* fix unit tests

* make transformer filterable

/cc @Menrath

* use transformer factory, so that transformer can be overwritten

* phpcs fixes

* fix attachments

* fix comment transformer

* remove comments for now

* update readme/changelog

* simplify and unify json_encodes

---------

Co-authored-by: Django Doucet <mediaformat.ux@gmail.com>
Co-authored-by: Andreas <andreas@bocops.de>
Co-authored-by: Eana Hufwe <eana@1a23.com>
Co-authored-by: Matthew Exon <git.mexon@spamgourmet.com>
Co-authored-by: Django Doucet <django.doucet@webdevstudios.com>

README.md

@@ -113,6 +113,7 @@ Project maintained on GitHub at [automattic/wordpress-activitypub](https://githu
 * Added: Make Post-Template filterable
 * Added: CSS class for ActivityPub comments to allow custom designs
 * Added: FEP-2677: Identifying the Application Actor
+* Added: Basic Comment Federation
 * Improved: WebFinger endpoints
 
 ### 1.3.0 ###

assets/js/activitypub-admin.js

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

includes/activity/class-base-object.php

@@ -254,19 +254,6 @@ class Base_Object {
 	 */
 	protected $published;
 
-	/**
-	 * A Collection containing objects considered to be responses to
-	 * this object.
-	 *
-	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-replies
-	 *
-	 * @var string
-	 *    | Collection
-	 *    | Link
-	 *    | null
-	 */
-	protected $replies;
-
 	/**
 	 * The date and time describing the actual or expected starting time
 	 * of the object.
@@ -437,6 +424,19 @@ class Base_Object {
 	 */
 	protected $source;
 
+	/**
+	 * A Collection containing objects considered to be responses to
+	 * this object.
+	 *
+	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-replies
+	 *
+	 * @var string
+	 *    | Collection
+	 *    | Link
+	 *    | null
+	 */
+	protected $replies;
+
 	/**
 	 * Magic function to implement getter and setter
 	 *
@@ -672,7 +672,24 @@ class Base_Object {
 	 */
 	public function to_json() {
 		$array   = $this->to_array();
+		$options = \JSON_HEX_TAG | \JSON_HEX_AMP | \JSON_HEX_QUOT;
 
-		return \wp_json_encode( $array, \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_encode_options', $options );
+
+		return \wp_json_encode( $array, $options );
+	}
+
+	/**
+	 * Returns the keys of the object vars.
+	 *
+	 * @return array The keys of the object vars.
+	 */
+	public function get_object_var_keys() {
+		return \array_keys( \get_object_vars( $this ) );
 	}
 }

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 +46,37 @@ class Activity_Dispatcher {
 			return;
 		}
 
-		$wp_post->post_author = Users::BLOG_USER_ID;
-
 		if ( is_single_user() ) {
-			self::send_activity( $wp_post, $type );
+			self::send_activity( $wp_object, $type, Users::BLOG_USER_ID );
 		} 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 ) {
+	public static function send_activity( $wp_object, $type, $user_id = null ) {
-		if ( is_user_disabled( $wp_post->post_author ) ) {
+		$transformer = Factory::get_transformer( $wp_object );
+
+		if ( null !== $user_id ) {
+			$transformer->change_wp_user_id( $user_id );
+		}
+
+		$user_id = $transformer->get_wp_user_id();
+
+		if ( is_user_disabled( $user_id ) ) {
 			return;
 		}
 
-		$object = Post::transform( $wp_post )->to_object();
+		$activity = $transformer->to_activity( 'Create' );
 
-		$activity = new Activity();
+		$follower_inboxes  = Followers::get_inboxes( $user_id );
-		$activity->set_type( $type );
-		$activity->set_object( $object );
-
-		$follower_inboxes  = Followers::get_inboxes( $wp_post->post_author );
 		$mentioned_inboxes = Mention::get_inboxes( $activity->get_cc() );
 
 		$inboxes = array_merge( $follower_inboxes, $mentioned_inboxes );
@@ -80,19 +85,19 @@ 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, $user_id );
 		}
 	}
 
 	/**
 	 * 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;
 		}
@@ -101,16 +106,13 @@ class Activity_Dispatcher {
 			return;
 		}
 
-		$object = Post::transform( $wp_post )->to_object();
+		$transformer = Factory::get_transformer( $wp_object );
+		$transformer->change_wp_user_id( Users::BLOG_USER_ID );
 
-		$activity = new Activity();
+		$user_id  = $transformer->get_wp_user_id();
-		$activity->set_type( 'Announce' );
+		$activity = $transformer->to_activity( 'Announce' );
-		// to pre-fill attributes like "published" and "id"
-		$activity->set_object( $object );
-		// send only the id
-		$activity->set_object( $object->get_id() );
 
-		$follower_inboxes  = Followers::get_inboxes( $wp_post->post_author );
+		$follower_inboxes  = Followers::get_inboxes( $user_id );
 		$mentioned_inboxes = Mention::get_inboxes( $activity->get_cc() );
 
 		$inboxes = array_merge( $follower_inboxes, $mentioned_inboxes );
@@ -119,7 +121,7 @@ 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, $user_id );
 		}
 	}
 }

includes/class-activitypub.php

@@ -8,6 +8,9 @@ use Activitypub\Collection\Followers;
 
 use function Activitypub\sanitize_url;
 
+use function Activitypub\is_comment;
+use function Activitypub\is_activitypub_request;
+
 /**
  * ActivityPub Class
  *
@@ -19,6 +22,7 @@ class Activitypub {
 	 */
 	public static function init() {
 		\add_filter( 'template_include', array( self::class, 'render_json_template' ), 99 );
+		\add_action( 'template_redirect', array( self::class, 'template_redirect' ) );
 		\add_filter( 'query_vars', array( self::class, 'add_query_vars' ) );
 		\add_filter( 'pre_get_avatar_data', array( self::class, 'pre_get_avatar_data' ), 11, 2 );
 		\add_filter( 'get_comment_link', array( self::class, 'remote_comment_link' ), 11, 3 );
@@ -100,6 +104,8 @@ 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() ) {
@@ -117,11 +123,43 @@ class Activitypub {
 		return $json_template;
 	}
 
+	/**
+	 * Custom redirects for ActivityPub requests.
+	 *
+	 * @return void
+	 */
+	public static function template_redirect() {
+		$comment_id = get_query_var( 'c', null );
+
+		// check if it seems to be a comment
+		if ( ! $comment_id ) {
+			return;
+		}
+
+		$comment = get_comment( $comment_id );
+
+		// load a 404 page if `c` is set but not valid
+		if ( ! $comment ) {
+			global $wp_query;
+			$wp_query->set_404();
+			return;
+		}
+
+		// stop if it's not an ActivityPub comment
+		if ( is_activitypub_request() && $comment->user_id ) {
+			return;
+		}
+
+		wp_safe_redirect( get_comment_link( $comment ) );
+	}
+
 	/**
 	 * Add the 'activitypub' query variable so WordPress won't mangle it.
 	 */
 	public static function add_query_vars( $vars ) {
 		$vars[] = 'activitypub';
+		$vars[] = 'c';
+		$vars[] = 'p';
 
 		return $vars;
 	}
@@ -197,10 +235,18 @@ class Activitypub {
 	 * @return string $url
 	 */
 	public static function remote_comment_link( $comment_link, $comment ) {
-		$remote_comment_link = get_comment_meta( $comment->comment_ID, 'source_url', true );
+		if ( ! $comment || is_admin() ) {
-		if ( $remote_comment_link ) {
+			return $comment_link;
-			$comment_link = esc_url( $remote_comment_link );
 		}
+
+		$comment_meta = \get_comment_meta( $comment->comment_ID );
+
+		if ( ! empty( $comment_meta['source_url'][0] ) ) {
+			return $comment_meta['source_url'][0];
+		} elseif ( ! empty( $comment_meta['source_id'][0] ) ) {
+			return $comment_meta['source_id'][0];
+		}
+
 		return $comment_link;
 	}
 

includes/class-hashtag.php

@@ -12,8 +12,8 @@ class Hashtag {
 	 */
 	public static function init() {
 		if ( '1' === \get_option( 'activitypub_use_hashtags', '1' ) ) {
-			\add_filter( 'wp_insert_post', array( self::class, 'insert_post' ), 10, 2 );
+			\add_action( 'wp_insert_post', array( self::class, 'insert_post' ), 10, 2 );
-			\add_filter( 'the_content', array( self::class, 'the_content' ), 10, 2 );
+			\add_filter( 'the_content', array( self::class, 'the_content' ), 10, 1 );
 		}
 	}
 
@@ -67,7 +67,7 @@ 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-mention.php

@@ -14,7 +14,8 @@ class Mention {
 	 * Initialize the class, registering WordPress hooks
 	 */
 	public static function init() {
-		\add_filter( 'the_content', array( self::class, 'the_content' ), 99, 2 );
+		\add_filter( 'the_content', array( self::class, 'the_content' ), 99, 1 );
+		\add_filter( 'comment_text', array( self::class, 'the_content' ), 10, 1 );
 		\add_filter( 'activitypub_extract_mentions', array( self::class, 'extract_mentions' ), 99, 2 );
 	}
 

includes/class-scheduler.php

@@ -16,11 +16,47 @@ class Scheduler {
 	 * Initialize the class, registering WordPress hooks
 	 */
 	public static function init() {
+		// Post transitions
 		\add_action( 'transition_post_status', array( self::class, 'schedule_post_activity' ), 33, 3 );
+		\add_action(
+			'edit_attachment',
+			function ( $post_id ) {
+				self::schedule_post_activity( 'publish', 'publish', $post_id );
+			}
+		);
+		\add_action(
+			'add_attachment',
+			function ( $post_id ) {
+				self::schedule_post_activity( 'publish', '', $post_id );
+			}
+		);
+		\add_action(
+			'delete_attachment',
+			function ( $post_id ) {
+				self::schedule_post_activity( 'trash', '', $post_id );
+			}
+		);
 
+		// Comment transitions
+		\add_action( 'transition_comment_status', array( self::class, 'schedule_comment_activity' ), 20, 3 );
+		\add_action(
+			'edit_comment',
+			function ( $comment_id ) {
+				self::schedule_comment_activity( 'approved', 'approved', $comment_id );
+			}
+		);
+		\add_action(
+			'wp_insert_comment',
+			function ( $comment_id ) {
+				self::schedule_comment_activity( 'approved', '', $comment_id );
+			}
+		);
+
+		// Follower Cleanups
 		\add_action( 'activitypub_update_followers', array( self::class, 'update_followers' ) );
 		\add_action( 'activitypub_cleanup_followers', array( self::class, 'cleanup_followers' ) );
 
+		// Migration
 		\add_action( 'admin_init', array( self::class, 'schedule_migration' ) );
 	}
 
@@ -58,6 +94,8 @@ class Scheduler {
 	 * @param WP_Post $post       Post object.
 	 */
 	public static function schedule_post_activity( $new_status, $old_status, $post ) {
+		$post = get_post( $post );
+
 		// Do not send activities if post is password protected.
 		if ( \post_password_required( $post ) ) {
 			return;
@@ -99,6 +137,57 @@ 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 );
+
+		// Federate only approved comments.
+		if ( ! $comment->user_id ) {
+			return;
+		}
+
+		if (
+			'approved' === $new_status &&
+			'approved' !== $old_status
+		) {
+			$type = 'Create';
+		} elseif ( 'approved' === $new_status ) {
+			$type = 'Update';
+		} elseif (
+			'trash' === $new_status ||
+			'spam' === $new_status
+		) {
+			$type = 'Delete';
+		}
+
+		if ( ! $type ) {
+			return;
+		}
+
+		\wp_schedule_single_event(
+			\time(),
+			'activitypub_send_activity',
+			array( $comment, $type )
+		);
+
+		\wp_schedule_single_event(
+			\time(),
+			sprintf(
+				'activitypub_send_%s_activity',
+				\strtolower( $type )
+			),
+			array( $comment )
+		);
+	}
+
 	/**
 	 * Update followers
 	 *

includes/class-shortcodes.php

@@ -110,8 +110,13 @@ class Shortcodes {
 
 		$excerpt = \get_post_field( 'post_excerpt', $item );
 
-		if ( '' === $excerpt ) {
+		if ( 'attachment' === $item->post_type ) {
-
+			// get title of attachment with fallback to alt text.
+			$content = wp_get_attachment_caption( $item->ID );
+			if ( empty( $content ) ) {
+				$content = get_post_meta( $item->ID, '_wp_attachment_image_alt', true );
+			}
+		} elseif ( '' === $excerpt ) {
 			$content = \get_post_field( 'post_content', $item );
 
 			// An empty string will make wp_trim_excerpt do stuff we do not want.
@@ -207,6 +212,15 @@ class Shortcodes {
 			$tag
 		);
 
+		$content = '';
+
+		if ( 'attachment' === $item->post_type ) {
+			// get title of attachment with fallback to alt text.
+			$content = wp_get_attachment_caption( $item->ID );
+			if ( empty( $content ) ) {
+				$content = get_post_meta( $item->ID, '_wp_attachment_image_alt', true );
+			}
+		} else {
 			$content = \get_post_field( 'post_content', $item );
 
 			if ( 'yes' === $atts['apply_filters'] ) {
@@ -221,6 +235,7 @@ class Shortcodes {
 			$content = \preg_replace( '@<(script|style)[^>]*?>.*?</\\1>@si', '', $content );
 			$content = strip_shortcodes( $content );
 			$content = \trim( \preg_replace( '/[\n\r\t]/', '', $content ) );
+		}
 
 		add_shortcode( 'ap_content', array( 'Activitypub\Shortcodes', 'content' ) );
 

includes/class-webfinger.php

@@ -15,7 +15,7 @@ class Webfinger {
 	/**
 	 * Returns a users WebFinger "resource"
 	 *
-	 * @param int $user_id
+	 * @param int $user_id The WordPress user id
 	 *
 	 * @return string The user-resource
 	 */
@@ -36,68 +36,65 @@ class Webfinger {
 	/**
 	 * Resolve a WebFinger resource
 	 *
-	 * @param string $resource The WebFinger resource
+	 * @param string $uri The WebFinger Resource
 	 *
 	 * @return string|WP_Error The URL or WP_Error
 	 */
-	public static function resolve( $resource ) {
+	public static function resolve( $uri ) {
-		if ( ! $resource ) {
+		$data = self::get_data( $uri );
-			return null;
+
+		if ( \is_wp_error( $data ) ) {
+			return $data;
 		}
 
-		if ( ! preg_match( '/^@?' . ACTIVITYPUB_USERNAME_REGEXP . '$/i', $resource, $m ) ) {
+		foreach ( $data['links'] as $link ) {
-			return null;
+			if (
-		}
+				'self' === $link['rel'] &&
-
+				'application/activity+json' === $link['type']
-		$transient_key = 'activitypub_resolve_' . ltrim( $resource, '@' );
+			) {
-
-		$link = \get_transient( $transient_key );
-		if ( $link ) {
-			return $link;
-		}
-
-		$url = \add_query_arg( 'resource', 'acct:' . ltrim( $resource, '@' ), 'https://' . $m[2] . '/.well-known/webfinger' );
-		if ( ! \wp_http_validate_url( $url ) ) {
-			$response = new WP_Error( 'invalid_webfinger_url', null, $url );
-			\set_transient( $transient_key, $response, HOUR_IN_SECONDS ); // Cache the error for a shorter period.
-			return $response;
-		}
-
-		// try to access author URL
-		$response = \wp_remote_get(
-			$url,
-			array(
-				'headers' => array( 'Accept' => 'application/jrd+json' ),
-				'redirection' => 2,
-				'timeout' => 2,
-			)
-		);
-
-		if ( \is_wp_error( $response ) ) {
-			$link = new WP_Error( 'webfinger_url_not_accessible', null, $url );
-			\set_transient( $transient_key, $link, HOUR_IN_SECONDS ); // Cache the error for a shorter period.
-			return $link;
-		}
-
-		$body = \wp_remote_retrieve_body( $response );
-		$body = \json_decode( $body, true );
-
-		if ( empty( $body['links'] ) ) {
-			$link = new WP_Error( 'webfinger_url_invalid_response', null, $url );
-			\set_transient( $transient_key, $link, HOUR_IN_SECONDS ); // Cache the error for a shorter period.
-			return $link;
-		}
-
-		foreach ( $body['links'] as $link ) {
-			if ( 'self' === $link['rel'] && 'application/activity+json' === $link['type'] ) {
-				\set_transient( $transient_key, $link['href'], WEEK_IN_SECONDS );
 				return $link['href'];
 			}
 		}
 
-		$link = new WP_Error( 'webfinger_url_no_activitypub', null, $body );
+		return new WP_Error( 'webfinger_url_no_activitypub', null, $data );
-		\set_transient( $transient_key, $link, HOUR_IN_SECONDS ); // Cache the error for a shorter period.
+	}
-		return $link;
+
+	/**
+	 * Transform a URI to an acct <identifier>@<host>
+	 *
+	 * @param string $uri The URI (acct:, mailto:, http:, https:)
+	 *
+	 * @return string|WP_Error Error or acct URI
+	 */
+	public static function uri_to_acct( $uri ) {
+		$data = self::get_data( $uri );
+
+		if ( is_wp_error( $data ) ) {
+			return $data;
+		}
+
+		// check if subject is an acct URI
+		if (
+			isset( $data['subject'] ) &&
+			\str_starts_with( $data['subject'], 'acct:' )
+		) {
+			return $data['subject'];
+		}
+
+		// search for an acct URI in the aliases
+		if ( isset( $data['aliases'] ) ) {
+			foreach ( $data['aliases'] as $alias ) {
+				if ( \str_starts_with( $alias, 'acct:' ) ) {
+					return $alias;
+				}
+			}
+		}
+
+		return new WP_Error(
+			'webfinger_url_no_acct',
+			__( 'No acct URI found.', 'activitypub' ),
+			$data
+		);
 	}
 
 	/**
@@ -137,7 +134,7 @@ class Webfinger {
 		}
 
 		if ( empty( $host ) ) {
-			return new WP_Error( 'invalid_identifier', __( 'Invalid Identifier', 'activitypub' ) );
+			return new WP_Error( 'webfinger_invalid_identifier', __( 'Invalid Identifier', 'activitypub' ) );
 		}
 
 		return array( $identifier, $host );
@@ -146,55 +143,70 @@ class Webfinger {
 	/**
 	 * Get the WebFinger data for a given URI
 	 *
-	 * @param string $identifier The Identifier: <identifier>@<host>
+	 * @param string $uri The Identifier: <identifier>@<host> or URI
-	 * @param string $host       The Host: <identifier>@<host>
 	 *
 	 * @return WP_Error|array Error reaction or array with
 	 *                        identifier and host as values
 	 */
-	public static function get_data( $identifier, $host ) {
+	public static function get_data( $uri ) {
-		$webfinger_url = 'https://' . $host . '/.well-known/webfinger?resource=' . rawurlencode( $identifier );
-
-		$response = wp_safe_remote_get(
-			$webfinger_url,
-			array(
-				'headers' => array( 'Accept' => 'application/jrd+json' ),
-				'redirection' => 0,
-				'timeout' => 2,
-			)
-		);
-
-		if ( is_wp_error( $response ) ) {
-			return new WP_Error( 'webfinger_url_not_accessible', null, $webfinger_url );
-		}
-
-		$body = wp_remote_retrieve_body( $response );
-
-		return json_decode( $body, true );
-	}
-
-	/**
-	 * Undocumented function
-	 *
-	 * @return void
-	 */
-	public static function get_remote_follow_endpoint( $uri ) {
 		$identifier_and_host = self::get_identifier_and_host( $uri );
 
 		if ( is_wp_error( $identifier_and_host ) ) {
 			return $identifier_and_host;
 		}
 
+		$transient_key = self::generate_cache_key( $uri );
+
 		list( $identifier, $host ) = $identifier_and_host;
 
-		$data = self::get_data( $identifier, $host );
+		$data = \get_transient( $transient_key );
+		if ( $data ) {
+			return $data;
+		}
+
+		$webfinger_url = 'https://' . $host . '/.well-known/webfinger?resource=' . rawurlencode( $identifier );
+
+		$response = wp_safe_remote_get(
+			$webfinger_url,
+			array(
+				'headers' => array( 'Accept' => 'application/jrd+json' ),
+			)
+		);
+
+		if ( is_wp_error( $response ) ) {
+			return new WP_Error(
+				'webfinger_url_not_accessible',
+				__( 'The WebFinger Resource is not accessible.', 'activitypub' ),
+				$webfinger_url
+			);
+		}
+
+		$body = wp_remote_retrieve_body( $response );
+		$data = json_decode( $body, true );
+
+		\set_transient( $transient_key, $data, WEEK_IN_SECONDS );
+
+		return $data;
+	}
+
+	/**
+	 * Get the Remote-Follow endpoint for a given URI
+	 *
+	 * @return string|WP_Error Error or the Remote-Follow endpoint URI.
+	 */
+	public static function get_remote_follow_endpoint( $uri ) {
+		$data = self::get_data( $uri );
 
 		if ( is_wp_error( $data ) ) {
 			return $data;
 		}
 
 		if ( empty( $data['links'] ) ) {
-			return new WP_Error( 'webfinger_url_invalid_response', null, $data );
+			return new WP_Error(
+				'webfinger_missing_links',
+				__( 'No valid Link elements found.', 'activitypub' ),
+				$data
+			);
 		}
 
 		foreach ( $data['links'] as $link ) {
@@ -203,6 +215,27 @@ class Webfinger {
 			}
 		}
 
-		return new WP_Error( 'webfinger_remote_follow_endpoint_invalid', $data, array( 'status' => 417 ) );
+		return new WP_Error(
+			'webfinger_missing_remote_follow_endpoint',
+			__( 'No valid Remote-Follow endpoint found.', 'activitypub' ),
+			$data
+		);
+	}
+
+	/**
+	 * Generate a cache key for a given URI
+	 *
+	 * @param string $uri A WebFinger Resource URI
+	 *
+	 * @return string The cache key
+	 */
+	public static function generate_cache_key( $uri ) {
+		$uri = ltrim( $uri, '@' );
+
+		if ( filter_var( $uri, FILTER_VALIDATE_EMAIL ) ) {
+			$uri = 'acct:' . $uri;
+		}
+
+		return 'webfinger_' . md5( $uri );
 	}
 }

includes/collection/class-interactions.php

@@ -33,10 +33,11 @@ class Interactions {
 
 		$in_reply_to        = \esc_url_raw( $activity['object']['inReplyTo'] );
 		$comment_post_id    = \url_to_postid( $in_reply_to );
-		$parent_comment  = object_id_to_comment( $in_reply_to );
+		$parent_comment_id  = url_to_commentid( $in_reply_to );
 
 		// save only replys and reactions
-		if ( ! $comment_post_id && $parent_comment ) {
+		if ( ! $comment_post_id && $parent_comment_id ) {
+			$parent_comment  = get_comment( $parent_comment_id );
 			$comment_post_id = $parent_comment->comment_post_ID;
 		}
 
@@ -58,10 +59,9 @@ class Interactions {
 			'comment_content' => \addslashes( $activity['object']['content'] ),
 			'comment_type' => 'comment',
 			'comment_author_email' => '',
-			'comment_parent' => $parent_comment ? $parent_comment->comment_ID : 0,
+			'comment_parent' => $parent_comment_id ? $parent_comment_id : 0,
 			'comment_meta' => array(
 				'source_id'  => \esc_url_raw( $activity['object']['id'] ),
-				'source_url' => \esc_url_raw( $activity['object']['url'] ),
 				'protocol'   => 'activitypub',
 			),
 		);
@@ -70,6 +70,10 @@ class Interactions {
 			$commentdata['comment_meta']['avatar_url'] = \esc_url_raw( $meta['icon']['url'] );
 		}
 
+		if ( isset( $activity['object']['url'] ) ) {
+			$commentdata['comment_meta']['source_url'] = \esc_url_raw( $activity['object']['url'] );
+		}
+
 		// disable flood control
 		\remove_action( 'check_comment_flood', 'check_comment_flood_db', 10 );
 		// do not require email for AP entries
@@ -104,14 +108,14 @@ class Interactions {
 		$meta = get_remote_metadata_by_actor( $activity['actor'] );
 
 		//Determine comment_ID
-		$object_comment_id = url_to_commentid( \esc_url_raw( $activity['object']['id'] ) );
+		$comment     = object_id_to_comment( \esc_url_raw( $activity['object']['id'] ) );
+		$commentdata = \get_comment( $comment, ARRAY_A );
 
-		if ( ! $object_comment_id ) {
+		if ( ! $commentdata ) {
 			return false;
 		}
 
 		//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'] = \addslashes( $activity['object']['content'] );
 		if ( isset( $meta['icon']['url'] ) ) {

includes/functions.php

@@ -4,6 +4,7 @@ namespace Activitypub;
 use WP_Error;
 use WP_Comment_Query;
 use Activitypub\Http;
+use Activitypub\Webfinger;
 use Activitypub\Activity\Activity;
 use Activitypub\Collection\Followers;
 use Activitypub\Collection\Users;
@@ -168,6 +169,27 @@ function url_to_authorid( $url ) {
 	return 0;
 }
 
+/**
+ * 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( 'c', null );
+
+	if ( ! is_null( $comment_id ) ) {
+		$comment = \get_comment( $comment_id );
+
+		// Only return local origin comments
+		if ( $comment && $comment->user_id ) {
+			return $comment_id;
+		}
+	}
+
+	return false;
+}
+
 /**
  * Check for Tombstone Objects
  *
@@ -579,7 +601,7 @@ function get_active_users( $duration = 1 ) {
 		global $wpdb;
 		$query = "SELECT COUNT( DISTINCT post_author ) FROM {$wpdb->posts} WHERE post_type = 'post' AND post_status = 'publish' AND post_date <= DATE_SUB( NOW(), INTERVAL %d MONTH )";
 		$query = $wpdb->prepare( $query, $duration );
-		$count = $wpdb->get_var( $query ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery
+		$count = $wpdb->get_var( $query ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
 
 		set_transient( $transient_key, $count, DAY_IN_SECONDS );
 	}
@@ -674,6 +696,23 @@ function url_to_commentid( $url ) {
 		return null;
 	}
 
+	// check for local comment
+	if ( \wp_parse_url( \site_url(), \PHP_URL_HOST ) === \wp_parse_url( $url, \PHP_URL_HOST ) ) {
+		$query = \wp_parse_url( $url, PHP_URL_QUERY );
+
+		if ( $query ) {
+			parse_str( $query, $params );
+
+			if ( ! empty( $params['c'] ) ) {
+				$comment = \get_comment( $params['c'] );
+
+				if ( $comment ) {
+					return $comment->comment_ID;
+				}
+			}
+		}
+	}
+
 	$args = array(
 		// phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_query
 		'meta_query' => array(

includes/rest/class-users.php

@@ -50,14 +50,13 @@ class Users {
 				array(
 					'methods'             => WP_REST_Server::READABLE,
 					'callback'            => array( self::class, 'remote_follow_get' ),
-
+					'permission_callback' => '__return_true',
 					'args'                => array(
 						'resource' => array(
 							'required'          => true,
 							'sanitize_callback' => 'sanitize_text_field',
 						),
 					),
-					'permission_callback' => '__return_true',
 				),
 			)
 		);

includes/transformer/class-attachment.php

@@ -0,0 +1,49 @@
+<?php
+namespace Activitypub\Transformer;
+
+use Activitypub\Transformer\Post;
+
+/**
+ * WordPress Attachment Transformer
+ *
+ * The Attachment Transformer is responsible for transforming a WP_Post object into different other
+ * Object-Types.
+ *
+ * Currently supported are:
+ *
+ * - Activitypub\Activity\Base_Object
+ */
+class Attachment extends Post {
+	/**
+	 * Generates all Media Attachments for a Post.
+	 *
+	 * @return array The Attachments.
+	 */
+	protected function get_attachment() {
+		$mime_type  = get_post_mime_type( $this->object->ID );
+		$media_type = preg_replace( '/(\/[a-zA-Z]+)/i', '', $mime_type );
+
+		switch ( $media_type ) {
+			case 'audio':
+			case 'video':
+				$type = 'Document';
+				break;
+			case 'image':
+				$type = 'Image';
+				break;
+		}
+
+		$attachment = array(
+			'type'      => $type,
+			'url'       => wp_get_attachment_url( $this->object->ID ),
+			'mediaType' => $mime_type,
+		);
+
+		$alt = \get_post_meta( $this->object->ID, '_wp_attachment_image_alt', true );
+		if ( $alt ) {
+			$attachment['name'] = $alt;
+		}
+
+		return $attachment;
+	}
+}

includes/transformer/class-base.php

@@ -0,0 +1,105 @@
+<?php
+namespace Activitypub\Transformer;
+
+use Activitypub\Activity\Activity;
+use Activitypub\Activity\Base_Object;
+
+/**
+ * WordPress Base Transformer
+ *
+ * Transformers are responsible for transforming a WordPress objects into different ActivityPub
+ * Object-Types or Activities.
+ */
+abstract class Base {
+	/**
+	 * The WP_Post object.
+	 *
+	 * @var
+	 */
+	protected $object;
+
+	/**
+	 * Static function to Transform a WordPress Object.
+	 *
+	 * This helps to chain the output of the Transformer.
+	 *
+	 * @param stdClass $object The WP_Post object
+	 *
+	 * @return void
+	 */
+	public static function transform( $object ) {
+		return new static( $object );
+	}
+
+	/**
+	 * Base constructor.
+	 *
+	 * @param stdClass $object
+	 */
+	public function __construct( $object ) {
+		$this->object = $object;
+	}
+
+	/**
+	 * Transform the WordPress Object into an ActivityPub Object.
+	 *
+	 * @return Activitypub\Activity\Base_Object
+	 */
+	public function to_object() {
+		$object = new Base_Object();
+
+		$vars = $object->get_object_var_keys();
+
+		foreach ( $vars as $var ) {
+			$getter = 'get_' . $var;
+
+			if ( method_exists( $this, $getter ) ) {
+				$value = call_user_func( array( $this, $getter ) );
+
+				if ( isset( $value ) ) {
+					$setter = 'set_' . $var;
+
+					call_user_func( array( $object, $setter ), $value );
+				}
+			}
+		}
+
+		return $object;
+	}
+
+	/**
+	 * Transforms the ActivityPub Object to an Activity
+	 *
+	 * @param string $type The Activity-Type.
+	 *
+	 * @return \Activitypub\Activity\Activity The Activity.
+	 */
+	public function to_activity( $type ) {
+		$object = $this->to_object();
+
+		$activity = new Activity();
+		$activity->set_type( $type );
+		$activity->set_object( $object );
+
+		// Use simple Object (only ID-URI) for Like and Announce
+		if ( in_array( $type, array( 'Like', 'Announce' ), true ) ) {
+			$activity->set_object( $object->get_id() );
+		}
+
+		return $activity;
+	}
+
+	/**
+	 * Returns the ID of the WordPress Object.
+	 *
+	 * @return int The ID of the WordPress Object
+	 */
+	abstract public function get_wp_user_id();
+
+	/**
+	 * Change the User-ID of the WordPress Post.
+	 *
+	 * @return int The User-ID of the WordPress Post
+	 */
+	abstract public function change_wp_user_id( $user_id );
+}

includes/transformer/class-comment.php

@@ -0,0 +1,277 @@
+<?php
+namespace Activitypub\Transformer;
+
+use WP_Comment;
+use WP_Comment_Query;
+use Activitypub\Hashtag;
+use Activitypub\Webfinger;
+use Activitypub\Model\Blog_User;
+use Activitypub\Collection\Users;
+use Activitypub\Transformer\Base;
+use Activitypub\Activity\Base_Object;
+
+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 extends Base {
+	/**
+	 * Returns the User-ID of the WordPress Comment.
+	 *
+	 * @return int The User-ID of the WordPress Comment
+	 */
+	public function get_wp_user_id() {
+		return $this->object->user_id;
+	}
+
+	/**
+	 * Change the User-ID of the WordPress Comment.
+	 *
+	 * @return int The User-ID of the WordPress Comment
+	 */
+	public function change_wp_user_id( $user_id ) {
+		$this->object->user_id = $user_id;
+	}
+
+	/**
+	 * 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->object;
+		$object  = parent::to_object();
+
+		$object->set_url( \get_comment_link( $comment->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_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 ),
+			)
+		);
+
+		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->object->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->object;
+		$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;
+	}
+
+	/**
+	 * Returns the in-reply-to for the ActivityPub Item.
+	 *
+	 * @return int The URL of the in-reply-to.
+	 */
+	protected function get_in_reply_to() {
+		$comment = $this->object;
+
+		$parent_comment = \get_comment( $comment->comment_parent );
+
+		if ( $parent_comment ) {
+			$comment_meta = \get_comment_meta( $parent_comment->comment_ID );
+
+			if ( ! empty( $comment_meta['source_id'][0] ) ) {
+				$in_reply_to = $comment_meta['source_id'][0];
+			} elseif ( ! empty( $comment_meta['source_url'][0] ) ) {
+				$in_reply_to = $comment_meta['source_url'][0];
+			} else {
+				$in_reply_to = $this->generate_id( $parent_comment );
+			}
+		} else {
+			$in_reply_to = \get_permalink( $comment->comment_post_ID );
+		}
+
+		return $in_reply_to;
+	}
+
+	/**
+	 * Returns the ID of the ActivityPub Object.
+	 *
+	 * @see https://www.w3.org/TR/activitypub/#obj-id
+	 * @see https://github.com/tootsuite/mastodon/issues/13879
+	 *
+	 * @return string ActivityPub URI for comment
+	 */
+	protected function get_id() {
+		$comment = $this->object;
+		return $this->generate_id( $comment );
+	}
+
+	/**
+	 * Generates an ActivityPub URI for a comment
+	 *
+	 * @param WP_Comment|int $comment A comment object or comment ID
+	 *
+	 * @return string ActivityPub URI for comment
+	 */
+	protected function generate_id( $comment ) {
+		$comment = get_comment( $comment );
+
+		return \add_query_arg(
+			array(
+				'c' => $comment->comment_ID,
+			),
+			\trailingslashit( site_url() )
+		);
+	}
+
+	/**
+	 * 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;
+			}
+		}
+
+		$comment_query = new WP_Comment_Query(
+			array(
+				'post_id'    => $this->object->comment_post_ID,
+				// phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_query
+				'meta_query' => array(
+					array(
+						'key'     => 'source_id',
+						'compare' => 'EXISTS',
+					),
+				),
+			)
+		);
+
+		if ( $comment_query->comments ) {
+			foreach ( $comment_query->comments as $comment ) {
+				if ( empty( $comment->comment_author_url ) ) {
+					continue;
+				}
+				$cc[] = \esc_url( $comment->comment_author_url );
+			}
+		}
+
+		$cc = \array_unique( $cc );
+
+		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_tag() {
+		$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 \array_unique( $tags, SORT_REGULAR );
+	}
+
+	/**
+	 * 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->object->comment_content, $this->object );
+	}
+
+	/**
+	 * Returns the locale of the post.
+	 *
+	 * @return string The locale of the post.
+	 */
+	public function get_locale() {
+		$comment_id = $this->object->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->object );
+	}
+}

includes/transformer/class-factory.php

@@ -0,0 +1,61 @@
+<?php
+namespace Activitypub\Transformer;
+
+use Activitypub\Transformer\Post;
+use Activitypub\Transformer\Comment;
+use Activitypub\Transformer\Attachment;
+
+/**
+ * Transformer Factory
+ */
+class Factory {
+	public static function get_transformer( $object ) {
+		/**
+		 * Filter the transformer for a given object.
+		 *
+		 * Add your own transformer based on the object class or the object type.
+		 *
+		 * Example usage:
+		 *
+		 * // Filter be object class
+		 * add_filter( 'activitypub_transformer', function( $transformer, $object, $object_class ) {
+		 *     if ( $object_class === 'WP_Post' ) {
+		 *         return new My_Post_Transformer( $object );
+		 *     }
+		 *     return $transformer;
+		 * }, 10, 3 );
+		 *
+		 * // Filter be object type
+		 * add_filter( 'activitypub_transformer', function( $transformer, $object, $object_class ) {
+		 *     if ( $object->post_type === 'event' ) {
+		 *         return new My_Event_Transformer( $object );
+		 *     }
+		 *     return $transformer;
+		 * }, 10, 3 );
+		 *
+		 * @param Activitypub\Transformer\Base $transformer  The transformer to use.
+		 * @param mixed                        $object       The object to transform.
+		 * @param string                       $object_class The class of the object to transform.
+		 *
+		 * @return mixed The transformer to use.
+		 */
+		$transformer = apply_filters( 'activitypub_transformer', null, $object, get_class( $object ) );
+
+		if ( $transformer ) {
+			return $transformer;
+		}
+
+		// use default transformer
+		switch ( get_class( $object ) ) {
+			case 'WP_Post':
+				if ( 'attachment' === $object->post_type ) {
+					return new Attachment( $object );
+				}
+				return new Post( $object );
+			case 'WP_Comment':
+				return new Comment( $object );
+			default:
+				return null;
+		}
+	}
+}

includes/transformer/class-post.php

@@ -2,10 +2,11 @@
 namespace Activitypub\Transformer;
 
 use WP_Post;
-use Activitypub\Collection\Users;
-use Activitypub\Model\Blog_User;
-use Activitypub\Activity\Base_Object;
 use Activitypub\Shortcodes;
+use Activitypub\Model\Blog_User;
+use Activitypub\Transformer\Base;
+use Activitypub\Collection\Users;
+use Activitypub\Activity\Base_Object;
 
 use function Activitypub\esc_hashtag;
 use function Activitypub\is_single_user;
@@ -15,42 +16,32 @@ use function Activitypub\site_supports_blocks;
 /**
  * WordPress Post Transformer
  *
- * The Post Transformer is responsible for transforming a WP_Post object into different othe
+ * The Post Transformer is responsible for transforming a WP_Post object into different other
  * Object-Types.
  *
  * Currently supported are:
  *
  * - Activitypub\Activity\Base_Object
  */
-class Post {
+class Post extends Base {
-
 	/**
-	 * The WP_Post object.
+	 * Returns the ID of the WordPress Post.
 	 *
-	 * @var WP_Post
+	 * @return int The ID of the WordPress Post
 	 */
-	protected $wp_post;
+	public function get_wp_user_id() {
-
+		return $this->object->post_author;
-	/**
-	 * Static function to Transform a WP_Post Object.
-	 *
-	 * This helps to chain the output of the Transformer.
-	 *
-	 * @param WP_Post $wp_post The WP_Post object
-	 *
-	 * @return void
-	 */
-	public static function transform( WP_Post $wp_post ) {
-		return new static( $wp_post );
 	}
 
 	/**
+	 * Change the User-ID of the WordPress Post.
 	 *
-	 *
+	 * @return int The User-ID of the WordPress Post
-	 * @param WP_Post $wp_post
 	 */
-	public function __construct( WP_Post $wp_post ) {
+	public function change_wp_user_id( $user_id ) {
-		$this->wp_post = $wp_post;
+		$this->object->post_author = $user_id;
+
+		return $this;
 	}
 
 	/**
@@ -61,31 +52,25 @@ class Post {
 	 * @return \Activitypub\Activity\Base_Object The ActivityPub Object
 	 */
 	public function to_object() {
-		$wp_post = $this->wp_post;
+		$post = $this->object;
-		$object = new Base_Object();
+		$object = parent::to_object();
 
-		$object->set_id( $this->get_id() );
+		$published = \strtotime( $post->post_date_gmt );
-		$object->set_url( $this->get_url() );
-		$object->set_type( $this->get_object_type() );
-
-		$published = \strtotime( $wp_post->post_date_gmt );
 
 		$object->set_published( \gmdate( 'Y-m-d\TH:i:s\Z', $published ) );
 
-		$updated = \strtotime( $wp_post->post_modified_gmt );
+		$updated = \strtotime( $post->post_modified_gmt );
 
 		if ( $updated > $published ) {
 			$object->set_updated( \gmdate( 'Y-m-d\TH:i:s\Z', $updated ) );
 		}
 
-		$object->set_attributed_to( $this->get_attributed_to() );
-		$object->set_content( $this->get_content() );
 		$object->set_content_map(
 			array(
 				$this->get_locale() => $this->get_content(),
 			)
 		);
-		$path = sprintf( 'users/%d/followers', intval( $wp_post->post_author ) );
+		$path = sprintf( 'users/%d/followers', intval( $post->post_author ) );
 
 		$object->set_to(
 			array(
@@ -93,9 +78,6 @@ class Post {
 				get_rest_url_by_path( $path ),
 			)
 		);
-		$object->set_cc( $this->get_cc() );
-		$object->set_attachment( $this->get_attachments() );
-		$object->set_tag( $this->get_tags() );
 
 		return $object;
 	}
@@ -115,7 +97,7 @@ class Post {
 	 * @return string The Posts URL.
 	 */
 	public function get_url() {
-		$post = $this->wp_post;
+		$post = $this->object;
 
 		if ( 'trash' === get_post_status( $post ) ) {
 			$permalink = \get_post_meta( $post->ID, 'activitypub_canonical_url', true );
@@ -139,7 +121,7 @@ class Post {
 			return $user->get_url();
 		}
 
-		return Users::get_by_id( $this->wp_post->post_author )->get_url();
+		return Users::get_by_id( $this->object->post_author )->get_url();
 	}
 
 	/**
@@ -147,12 +129,12 @@ class Post {
 	 *
 	 * @return array The Attachments.
 	 */
-	protected function get_attachments() {
+	protected function get_attachment() {
 		// Once upon a time we only supported images, but we now support audio/video as well.
 		// We maintain the image-centric naming for backwards compatibility.
 		$max_media = intval( \apply_filters( 'activitypub_max_image_attachments', \get_option( 'activitypub_max_image_attachments', ACTIVITYPUB_MAX_IMAGE_ATTACHMENTS ) ) );
 
-		if ( site_supports_blocks() && \has_blocks( $this->wp_post->post_content ) ) {
+		if ( site_supports_blocks() && \has_blocks( $this->object->post_content ) ) {
 			return $this->get_block_attachments( $max_media );
 		}
 
@@ -172,7 +154,7 @@ class Post {
 			return array();
 		}
 
-		$id = $this->wp_post->ID;
+		$id = $this->object->ID;
 
 		$media_ids = array();
 
@@ -182,7 +164,7 @@ class Post {
 		}
 
 		if ( $max_media > 0 ) {
-			$blocks = \parse_blocks( $this->wp_post->post_content );
+			$blocks = \parse_blocks( $this->object->post_content );
 			$media_ids = self::get_media_ids_from_blocks( $blocks, $media_ids, $max_media );
 		}
 
@@ -203,7 +185,7 @@ class Post {
 			return array();
 		}
 
-		$id = $this->wp_post->ID;
+		$id = $this->object->ID;
 
 		$image_ids = array();
 
@@ -316,7 +298,7 @@ class Post {
 				 */
 				$thumbnail = apply_filters(
 					'activitypub_get_image',
-					self::get_image( $id, $image_size ),
+					self::get_wordpress_attachment( $id, $image_size ),
 					$id,
 					$image_size
 				);
@@ -365,7 +347,7 @@ class Post {
 	 *
 	 * @return array|false Array of image data, or boolean false if no image is available.
 	 */
-	protected static function get_image( $id, $image_size = 'full' ) {
+	protected static function get_wordpress_attachment( $id, $image_size = 'full' ) {
 		/**
 		 * Hook into the image retrieval process. Before image retrieval.
 		 *
@@ -402,10 +384,10 @@ class Post {
 
 		// Default to Article.
 		$object_type = 'Article';
-		$post_type = \get_post_type( $this->wp_post );
+		$post_type = \get_post_type( $this->object );
 		switch ( $post_type ) {
 			case 'post':
-				$post_format = \get_post_format( $this->wp_post );
+				$post_format = \get_post_format( $this->object );
 				switch ( $post_format ) {
 					case 'aside':
 					case 'status':
@@ -481,10 +463,10 @@ class Post {
 	 *
 	 * @return array The list of Tags.
 	 */
-	protected function get_tags() {
+	protected function get_tag() {
 		$tags = array();
 
-		$post_tags = \get_the_tags( $this->wp_post->ID );
+		$post_tags = \get_the_tags( $this->object->ID );
 		if ( $post_tags ) {
 			foreach ( $post_tags as $post_tag ) {
 				$tag = array(
@@ -531,7 +513,7 @@ class Post {
 		do_action( 'activitypub_before_get_content', $post );
 
 		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
-		$post    = $this->wp_post;
+		$post    = $this->object;
 		$content = $this->get_post_content_template();
 
 		// Register our shortcodes just in time.
@@ -576,7 +558,7 @@ class Post {
 				break;
 		}
 
-		return apply_filters( 'activitypub_object_content_template', $template, $this->wp_post );
+		return apply_filters( 'activitypub_object_content_template', $template, $this->object );
 	}
 
 	/**
@@ -585,7 +567,7 @@ class Post {
 	 * @return array The list of @-Mentions.
 	 */
 	protected function get_mentions() {
-		return apply_filters( 'activitypub_extract_mentions', array(), $this->wp_post->post_content, $this->wp_post );
+		return apply_filters( 'activitypub_extract_mentions', array(), $this->object->post_content, $this->object );
 	}
 
 	/**
@@ -594,7 +576,7 @@ class Post {
 	 * @return string The locale of the post.
 	 */
 	public function get_locale() {
-		$post_id = $this->wp_post->ID;
+		$post_id = $this->object->ID;
 		$lang    = \strtolower( \strtok( \get_locale(), '_-' ) );
 
 		/**
@@ -606,6 +588,6 @@ class Post {
 		 *
 		 * @return string The filtered locale of the post.
 		 */
-		return apply_filters( 'activitypub_post_locale', $lang, $post_id, $this->wp_post );
+		return apply_filters( 'activitypub_post_locale', $lang, $post_id, $this->object );
 	}
 }

readme.txt

@@ -113,6 +113,7 @@ Project maintained on GitHub at [automattic/wordpress-activitypub](https://githu
 * Added: Make Post-Template filterable
 * Added: CSS class for ActivityPub comments to allow custom designs
 * Added: FEP-2677: Identifying the Application Actor
+* Added: Basic Comment Federation
 * Improved: WebFinger endpoints
 
 = 1.3.0 =

templates/author-json.php

@@ -10,23 +10,8 @@ $user->set_context(
  */
 \do_action( 'activitypub_json_author_pre', $user->get__id() );
 
-$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_author_options', $options, $user->get__id() );
-
 \header( 'Content-Type: application/activity+json' );
-echo \wp_json_encode( $user->to_array(), $options );
+echo $user->to_json(); // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
 
 /*
  * Action triggerd after the ActivityPub profile has been created and sent to the client

templates/blog-json.php

@@ -10,23 +10,8 @@ $user->set_context(
  */
 \do_action( 'activitypub_json_author_pre', $user->get__id() );
 
-$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_author_options', $options, $user->get__id() );
-
 \header( 'Content-Type: application/activity+json' );
-echo \wp_json_encode( $user->to_array(), $options );
+echo $user->to_json(); // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
 
 /*
  * Action triggerd after the ActivityPub profile has been created and sent to the client

templates/comment-json.php

@@ -0,0 +1,36 @@
+<?php
+$comment = \get_comment( \get_query_var( 'c', null ) ); // phpcs:ignore
+
+$object = \Activitypub\Transformer\Factory::get_transformer( $comment );
+$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' );

templates/post-json.php

@@ -2,34 +2,16 @@
 // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
 $post = \get_post();
 
-$object = new \Activitypub\Transformer\Post( $post );
+$post_object = \Activitypub\Transformer\Factory::get_transformer( $post )->to_object();
-$json = \array_merge( array( '@context' => \Activitypub\get_context() ), $object->to_object()->to_array() );
+$post_object->set_context( \Activitypub\get_context() );
-
-// filter output
-$json = \apply_filters( 'activitypub_json_post_array', $json );
 
 /*
  * Action triggerd prior to the ActivityPub profile being created and sent to the client
  */
 \do_action( 'activitypub_json_post_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_post_options', $options );
-
 \header( 'Content-Type: application/activity+json' );
-echo \wp_json_encode( $json, $options );
+echo $post_object->to_json(); // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
 
 /*
  * Action triggerd after the ActivityPub profile has been created and sent to the client

tests/test-class-activitypub-webfinger.php

@@ -0,0 +1,21 @@
+<?php
+class Test_Activitypub_Webfinger extends WP_UnitTestCase {
+	/**
+	 * @dataProvider the_cache_key_provider
+	 */
+	public function test_generate_cache_key( $uri, $hash ) {
+		$cache_key = Activitypub\Webfinger::generate_cache_key( $uri );
+
+		$this->assertEquals( $cache_key, 'webfinger_' . $hash );
+	}
+
+	public function the_cache_key_provider() {
+		return array(
+			array( 'http://example.org/?author=1', md5( 'http://example.org/?author=1' ) ),
+			array( '@author@example.org', md5( 'acct:author@example.org' ) ),
+			array( 'author@example.org', md5( 'acct:author@example.org' ) ),
+			array( 'acct:author@example.org', md5( 'acct:author@example.org' ) ),
+			array( 'https://example.org', md5( 'https://example.org' ) ),
+		);
+	}
+}