Integrate Federated Reply block with Reader post share (#2302)

Author: obenland

.github/changelog/2302-from-description

@@ -0,0 +1,4 @@
+Significance: minor
+Type: added
+
+Integrate Federated Reply block with WP.com Reader's post share functionality, allowing users to reply to ActivityPub posts directly from the Reader.

integration/class-jetpack.php

@@ -10,8 +10,11 @@
 use Activitypub\Collection\Followers;
 use Activitypub\Collection\Following;
 use Activitypub\Comment;
+use Activitypub\Http;
 use Automattic\Jetpack\Connection\Manager;
 
+use function Activitypub\is_activity_object;
+
 /**
  * Jetpack integration class.
  */
@@ -36,6 +39,8 @@ public static function init() {
 			\add_filter( 'activitypub_following_row_actions', array( self::class, 'add_reader_link' ), 10, 2 );
 			\add_filter( 'pre_option_activitypub_following_ui', array( self::class, 'pre_option_activitypub_following_ui' ) );
 		}
+
+		\add_action( 'load-post-new.php', array( self::class, 'adapt_post_share' ) );
 	}
 
 	/**
@@ -128,4 +133,25 @@ public static function add_reader_link( $actions, $item ) {
 	public static function pre_option_activitypub_following_ui() {
 		return '1';
 	}
+
+	/**
+	 * Adapt the parameters for a post share request to be compatible with the Federated Reply block.
+	 */
+	public static function adapt_post_share() {
+		if ( ! isset( $_GET['is_post_share'], $_GET['url'] ) || ! $_GET['is_post_share'] ) { // phpcs:ignore WordPress.Security
+			return;
+		}
+
+		$url = \sanitize_url( \wp_unslash( $_GET['url'] ) ); // phpcs:ignore WordPress.Security.NonceVerification
+
+		if ( is_activity_object( Http::get_remote_object( $url ) ) ) {
+			$args = array(
+				'post_type'   => 'post',
+				'in_reply_to' => $url,
+			);
+
+			\wp_safe_redirect( \add_query_arg( $args, \admin_url( 'post-new.php' ) ) );
+			exit;
+		}
+	}
 }