Add replies collection

activitypub.php

@@ -39,7 +39,7 @@
 \defined( 'ACTIVITYPUB_AUTHORIZED_FETCH' ) || \define( 'ACTIVITYPUB_AUTHORIZED_FETCH', false );
 \defined( 'ACTIVITYPUB_DISABLE_REWRITES' ) || \define( 'ACTIVITYPUB_DISABLE_REWRITES', false );
 \defined( 'ACTIVITYPUB_DISABLE_INCOMING_INTERACTIONS' ) || \define( 'ACTIVITYPUB_DISABLE_INCOMING_INTERACTIONS', false );
-// Disable reactions like `Like` and `Accounce` by default
+// Disable reactions like `Like` and `Announce` by default
 \defined( 'ACTIVITYPUB_DISABLE_REACTIONS' ) || \define( 'ACTIVITYPUB_DISABLE_REACTIONS', true );
 \defined( 'ACTIVITYPUB_DISABLE_OUTGOING_INTERACTIONS' ) || \define( 'ACTIVITYPUB_DISABLE_OUTGOING_INTERACTIONS', false );
 \defined( 'ACTIVITYPUB_SHARED_INBOX_FEATURE' ) || \define( 'ACTIVITYPUB_SHARED_INBOX_FEATURE', false );

includes/activity/class-activity.php

@@ -90,6 +90,21 @@ class Activity extends Base_Object {
 	 */
 	protected $result;
 
+	/**
+	 * Identifies a Collection containing objects considered to be responses
+	 * to this object.
+	 * WordPress has a strong core system of approving replies. We only include
+	 * approved replies here.
+	 *
+	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-replies
+	 *
+	 * @var array
+	 *    | ObjectType
+	 *    | Link
+	 *    | null
+	 */
+	protected $replies;
+
 	/**
 	 * An indirect object of the activity from which the
 	 * activity is directed.

includes/collection/class-followers.php

@@ -111,7 +111,7 @@ public static function get_follower( $user_id, $actor ) {
 	}
 
 	/**
-	 * Get a Follower by Actor indepenent from the User.
+	 * Get a Follower by Actor independent from the User.
 	 *
 	 * @param string $actor The Actor URL.
 	 *

includes/collection/class-replies.php

@@ -0,0 +1,175 @@
+<?php
+namespace Activitypub\Collection;
+
+use WP_Post;
+use WP_Comment;
+use WP_Error;
+
+use function Activitypub\is_local_comment;
+use function Activitypub\get_rest_url_by_path;
+
+/**
+ * Class containing code for getting replies Collections and CollectionPages of posts and comments.
+ */
+class Replies {
+	/**
+	 * Build base arguments for fetching the comments of either a WordPress post or comment.
+	 *
+	 * @param WP_Post|WP_Comment $wp_object
+	 */
+	private static function build_args( $wp_object ) {
+		$args = array(
+			'status' => 'approve',
+			'orderby' => 'comment_date_gmt',
+			'order'  => 'ASC',
+		);
+
+		if ( $wp_object instanceof WP_Post ) {
+			$args['parent'] = 0; // TODO: maybe this is unnecessary.
+			$args['post_id'] = $wp_object->ID;
+		} elseif ( $wp_object instanceof WP_Comment ) {
+			$args['parent'] = $wp_object->comment_ID;
+		} else {
+			return new WP_Error();
+		}
+
+		return $args;
+	}
+
+	/**
+	 * Adds pagination args comments query.
+	 *
+	 * @param array $args              Query args built by self::build_args.
+	 * @param int   $page              The current pagination page.
+	 * @param int   $comments_per_page The number of comments per page.
+	 */
+	private static function add_pagination_args( $args, $page, $comments_per_page ) {
+		$args['number'] = $comments_per_page;
+
+		$offset = intval( $page ) * $comments_per_page;
+		$args['offset'] = $offset;
+
+		return $args;
+	}
+
+
+	/**
+	 * Get the replies collections ID.
+	 *
+	 * @param WP_Post|WP_Comment $wp_object
+	 *
+	 * @return string The rest URL of the replies collection.
+	 */
+	private static function get_replies_id( $wp_object ) {
+		if ( $wp_object instanceof WP_Post ) {
+			return get_rest_url_by_path( sprintf( 'posts/%d/replies', $wp_object->ID ) );
+		} elseif ( $wp_object instanceof WP_Comment ) {
+			return get_rest_url_by_path( sprintf( 'comments/%d/replies', $wp_object->comment_ID ) );
+		} else {
+			return new WP_Error();
+		}
+	}
+
+	/**
+	 * Get the replies collection.
+	 *
+	 * @param WP_Post|WP_Comment $wp_object
+	 * @param int $page
+	 *
+	 * @return array An associative array containing the replies collection without JSON-LD context.
+	 */
+	public static function get_collection( $wp_object ) {
+		$id = self::get_replies_id( $wp_object );
+
+		if ( ! $id ) {
+			return null;
+		}
+
+		$replies = array(
+			'id'    => $id,
+			'type'  => 'Collection',
+		);
+
+		$replies['first'] = self::get_collection_page( $wp_object, 0, $replies['id'] );
+
+		return $replies;
+	}
+
+	/**
+	 * Get the ActivityPub ID's from a list of comments.
+	 *
+	 * It takes only federated/non-local comments into account, others also do not have an
+	 * ActivityPub ID available.
+	 *
+	 * @param WP_Comment[] $comments The comments to retrieve the ActivityPub ids from.
+	 *
+	 * @return string[] A list of the ActivityPub ID's.
+	 */
+	private static function get_activitypub_comment_ids( $comments ) {
+		$comment_ids = array();
+		// Only add external comments from the fediverse.
+		// Maybe use the Comment class more and the function is_local_comment etc.
+		foreach ( $comments as $comment ) {
+			if ( is_local_comment( $comment ) ) {
+				continue;
+			}
+			$comment_meta = \get_comment_meta( $comment->comment_ID );
+			if ( ! empty( $comment_meta['source_url'][0] ) ) {
+				$comment_ids[] = $comment_meta['source_url'][0];
+			} elseif ( ! empty( $comment_meta['source_id'][0] ) ) {
+				$comment_ids[] = $comment_meta['source_id'][0];
+			}
+		}
+		return $comment_ids;
+	}
+
+	/**
+	 * Returns a replies collection page as an associative array.
+	 *
+	 * @link https://www.w3.org/TR/activitystreams-vocabulary/#dfn-collectionpage
+	 *
+	 * @param WP_Post|WP_Comment $wp_object The post of comment the replies are for.
+	 * @param int                $page      The current pagination page.
+	 * @param string             $part_of   The collection id/url the returned CollectionPage belongs to.
+	 *
+	 * @return array A CollectionPage as an associative array.
+	 */
+	public static function get_collection_page( $wp_object, $page, $part_of = null ) {
+		// Build initial arguments for fetching approved comments.
+		$args = self::build_args( $wp_object );
+
+		// Retrieve the partOf if not already given.
+		$part_of = $part_of ?? self::get_replies_id( $wp_object );
+
+		// If the collection page does not exist.
+		if ( is_wp_error( $args ) || is_wp_error( $part_of ) ) {
+			return null;
+		}
+
+		// Get to total replies count.
+		$total_replies = \get_comments( array_merge( $args, array( 'count' => true ) ) );
+
+		// Modify query args to retrieve paginated results.
+		$comments_per_page = \get_option( 'comments_per_page' );
+
+		// Fetch internal and external comments for current page.
+		$comments = get_comments( self::add_pagination_args( $args, $page, $comments_per_page ) );
+
+		// Get the ActivityPub ID's of the comments, without out local-only comments.
+		$comment_ids = self::get_activitypub_comment_ids( $comments );
+
+		// Build the associative CollectionPage array.
+		$collection_page = array(
+			'id'     => \add_query_arg( 'page', $page, $part_of ),
+			'type'   => 'CollectionPage',
+			'partOf' => $part_of,
+			'items'  => $comment_ids,
+		);
+
+		if ( $total_replies / $comments_per_page > $page + 1 ) {
+			$collection_page['next'] = \add_query_arg( 'page', $page + 1, $part_of );
+		}
+
+		return $collection_page;
+	}
+}

includes/rest/class-collection.php

@@ -6,7 +6,10 @@
 use Activitypub\Activity\Actor;
 use Activitypub\Activity\Base_Object;
 use Activitypub\Collection\Users as User_Collection;
+use Activitypub\Collection\Replies;
+
 use Activitypub\Transformer\Factory;
+use WP_Error;
 
 use function Activitypub\esc_hashtag;
 use function Activitypub\is_single_user;
@@ -69,6 +72,73 @@ public static function register_routes() {
 				),
 			)
 		);
+
+		\register_rest_route(
+			ACTIVITYPUB_REST_NAMESPACE,
+			'/(?P<type>[\w\-\.]+)s/(?P<id>[\w\-\.]+)/replies',
+			array(
+				array(
+					'methods'             => WP_REST_Server::READABLE,
+					'callback'            => array( self::class, 'replies_get' ),
+					'args'                => self::request_parameters_for_replies(),
+					'permission_callback' => '__return_true',
+				),
+			)
+		);
+	}
+
+	/**
+	 * The endpoint for replies collections
+	 *
+	 * @param WP_REST_Request $request The request object.
+	 *
+	 * @return WP_REST_Response The response object.
+	 */
+	public static function replies_get( $request ) {
+		$type = $request->get_param( 'type' );
+
+		// Get the WordPress object of that "owns" the requested replies.
+		switch ( $type ) {
+			case 'comment':
+				$wp_object = \get_comment( $request->get_param( 'id' ) );
+				break;
+			case 'post':
+			default:
+				$wp_object = \get_post( $request->get_param( 'id' ) );
+				break;
+		}
+
+		if ( ! isset( $wp_object ) || is_wp_error( $wp_object ) ) {
+			return new WP_Error(
+				'activitypub_replies_collection_does_not_exist',
+				\sprintf(
+					// translators: %s: The type (post, comment, etc.) for which no replies collection exists.
+					\__( 'No reply collection exists for the type %s.', 'activitypub' ),
+					$type
+				)
+			);
+		}
+
+		$page = intval( $request->get_param( 'page' ) );
+
+		// If the request parameter page is present get the CollectionPage otherwise the replies collection.
+		if ( isset( $page ) ) {
+			$response = Replies::get_collection_page( $wp_object, $page );
+		} else {
+			$response = Replies::get_collection( $wp_object );
+		}
+
+		if ( is_wp_error( $response ) ) {
+			return $response;
+		}
+
+		// Add ActivityPub Context.
+		$response = array_merge(
+			array( '@context' => Base_Object::JSON_LD_CONTEXT ),
+			$response
+		);
+
+		return new WP_REST_Response( $response, 200 );
 	}
 
 	/**
@@ -220,7 +290,29 @@ public static function request_parameters() {
 
 		$params['user_id'] = array(
 			'required' => true,
-			'type' => 'string',
+			'type'     => 'string',
+		);
+
+		return $params;
+	}
+
+	/**
+	 * The supported parameters
+	 *
+	 * @return array list of parameters
+	 */
+	public static function request_parameters_for_replies() {
+		$params = array();
+
+		$params['type'] = array(
+			'required' => true,
+			'type'     => 'string',
+			'enum'     => array( 'post', 'comment' ),
+		);
+
+		$params['id'] = array(
+			'required' => true,
+			'type'     => 'string',
 		);
 
 		return $params;

includes/transformer/class-base.php

@@ -1,12 +1,13 @@
 <?php
 namespace Activitypub\Transformer;
 
-use WP_Error;
 use WP_Post;
 use WP_Comment;
 
 use Activitypub\Activity\Activity;
 use Activitypub\Activity\Base_Object;
+use Activitypub\Collection\Replies;
+
 
 /**
  * WordPress Base Transformer
@@ -108,6 +109,16 @@ public function to_activity( $type ) {
 		return $activity;
 	}
 
+	abstract protected function get_id();
+
+	/**
+	 * Get the replies Collection.
+	 */
+	public function get_replies() {
+		$replies = Replies::get_collection( $this->wp_object, $this->get_id() );
+		return $replies;
+	}
+
 	/**
 	 * Returns the ID of the WordPress Object.
 	 *

includes/transformer/class-post.php

@@ -124,7 +124,7 @@ protected function get_actor_object() {
 	 *
 	 * @return string The Posts ID.
 	 */
-	public function get_id() {
+	protected function get_id() {
 		return $this->get_url();
 	}