Add the Fediverse creator of a post to opengraph (#786)

* add the fediverse creator of a post to opengraph

see:

* https://wordpress.org/plugins/opengraph/
* https://codeberg.org/fediverse/fep/src/branch/main/fep/XXXX/fep-XXXX.md
* mastodon/mastodon#30398

* remove prefix until it is clearified

* Do not add the metadata if it already exists

Author: pfefferle

activitypub.php

@@ -101,6 +101,9 @@ function plugin_init() {
 	require_once __DIR__ . '/integration/class-enable-mastodon-apps.php';
 	Integration\Enable_Mastodon_Apps::init();
 
+	require_once __DIR__ . '/integration/class-opengraph.php';
+	Integration\Opengraph::init();
+
 	if ( \defined( 'JETPACK__VERSION' ) && ! \defined( 'IS_WPCOM' ) ) {
 		require_once __DIR__ . '/integration/class-jetpack.php';
 		Integration\Jetpack::init();

integration/class-opengraph.php

@@ -0,0 +1,71 @@
+<?php
+namespace Activitypub\Integration;
+
+use Activitypub\Collection\Users;
+
+/**
+ * Compatibility with the OpenGraph plugin
+ *
+ * @see https://wordpress.org/plugins/opengraph/
+ * @see https://codeberg.org/fediverse/fep/src/branch/main/fep/XXXX/fep-XXXX.md
+ * @see https://github.com/mastodon/mastodon/pull/30398
+ */
+class Opengraph {
+	/**
+	 * Initialize the class, registering WordPress hooks
+	 */
+	public static function init() {
+		// \add_filter( 'opengraph_prefixes', array( self::class, 'add_opengraph_prefixes' ) );
+		\add_filter( 'opengraph_metadata', array( self::class, 'add_opengraph_metadata' ) );
+	}
+
+	/**
+	 * Add the ActivityPub prefix to the OpenGraph prefixes.
+	 *
+	 * @param array $prefixes the current prefixes.
+	 *
+	 * @return array the updated prefixes.
+	 */
+	public static function add_opengraph_prefixes( $prefixes ) {
+		// @todo discuss namespace
+		$prefixes['fediverse'] = 'https://codeberg.org/fediverse/fep/src/branch/main/fep/XXXX/fep-XXXX.md';
+
+		return $prefixes;
+	}
+
+	/**
+	 * Add the ActivityPub metadata to the OpenGraph metadata.
+	 *
+	 * @param array $metadata the current metadata.
+	 *
+	 * @return array the updated metadata.
+	 */
+	public static function add_opengraph_metadata( $metadata ) {
+		// Do not add the metadata if it already exists
+		if ( array_key_exists( 'fediverse:creator', $metadata ) ) {
+			return $metadata;
+		}
+
+		if ( \is_author() ) {
+			$user_id = \get_queried_object_id();
+		} elseif (
+			\is_singular() &&
+			\post_type_supports( get_post_type(), 'activitypub' )
+		) {
+			$user_id = \get_the_author_meta( 'ID' );
+		} else {
+			return $metadata;
+		}
+
+		$user = Users::get_by_id( $user_id );
+
+		if ( ! $user || \is_wp_error( $user ) ) {
+			return $metadata;
+		}
+
+		// add WebFinger resource
+		$metadata['fediverse:creator'] = $user->get_webfinger();
+
+		return $metadata;
+	}
+}