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/class-comment.php

@@ -340,6 +340,46 @@ public static function comment_class( $classes, $css_class, $comment_id ) {
 		return $classes;
 	}
 
+	/**
+	 * Gets the public comment id via the WordPress comments meta.
+	 *
+	 * @param  int    $wp_comment_id The internal WordPress comment ID.
+	 * @param  bool   $fallback      Whether the code should fall back to `source_url` if `source_id` is not set.
+	 *
+	 * @return string|null           The ActivityPub id/url of the comment.
+	 */
+	public static function get_source_id( $wp_comment_id, $fallback = true ) {
+		$comment_meta = \get_comment_meta( $wp_comment_id );
+
+		if ( ! empty( $comment_meta['source_id'][0] ) ) {
+			return $comment_meta['source_id'][0];
+		} elseif ( ! empty( $comment_meta['source_url'][0] && $fallback ) ) {
+			return $comment_meta['source_url'][0];
+		}
+
+		return null;
+	}
+
+	/**
+	 * Gets the public comment url via the WordPress comments meta.
+	 *
+	 * @param  int    $wp_comment_id The internal WordPress comment ID.
+	 * @param  bool   $fallback      Whether the code should fall back to `source_id` if `source_url` is not set.
+	 *
+	 * @return string|null           The ActivityPub id/url of the comment.
+	 */
+	public static function get_source_url( $wp_comment_id, $fallback = true ) {
+		$comment_meta = \get_comment_meta( $wp_comment_id );
+
+		if ( ! empty( $comment_meta['source_url'][0] ) ) {
+			return $comment_meta['source_url'][0];
+		} elseif ( ! empty( $comment_meta['source_id'][0] && $fallback ) ) {
+			return $comment_meta['source_id'][0];
+		}
+
+		return null;
+	}
+
 	/**
 	 * Link remote comments to source url.
 	 *
@@ -353,15 +393,9 @@ public static function remote_comment_link( $comment_link, $comment ) {
 			return $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];
-		}
+		$public_comment_link = self::get_source_url( $comment->comment_ID );
 
-		return $comment_link;
+		return $public_comment_link ?? $comment_link;
 	}
 
 
@@ -373,14 +407,13 @@ public static function remote_comment_link( $comment_link, $comment ) {
 	 * @return string ActivityPub URI for comment
 	 */
 	public static function generate_id( $comment ) {
-		$comment      = \get_comment( $comment );
-		$comment_meta = \get_comment_meta( $comment->comment_ID );
+		$comment = \get_comment( $comment );
 
 		// show external comment ID if it exists
-		if ( ! empty( $comment_meta['source_id'][0] ) ) {
-			return $comment_meta['source_id'][0];
-		} elseif ( ! empty( $comment_meta['source_url'][0] ) ) {
-			return $comment_meta['source_url'][0];
+		$public_comment_link = self::get_source_id( $comment->comment_ID );
+
+		if ( $public_comment_link ) {
+			return $public_comment_link;
 		}
 
 		// generate URI based on comment ID

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 +1,176 @@
+<?php
+namespace Activitypub\Collection;
+
+use WP_Post;
+use WP_Comment;
+use WP_Error;
+
+use Activitypub\Comment;
+
+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_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_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_reply_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;
+			}
+
+			$public_comment_id = Comment::get_source_id( $comment->comment_ID );
+			if ( $public_comment_id ) {
+				$comment_ids[] = $public_comment_id;
+			}
+		}
+		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_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_reply_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;
+	}
+}