activitypub.php

<?php

// Force re-approval of updated comments.
add_action( 'activitypub_handled_update', function( $activity, $second_param, $state, $reaction ) {
	/** @todo: Send an email or something, because if you get quite a few of these, it's impossible to keep up. */
	if ( $reaction instanceof \WP_Comment ) {
		wp_set_comment_status( $reaction, 'hold' );
		wp_notify_moderator( $reaction->comment_ID );
	}
}, 99, 4 );

// Edit our ActivityPub Actor profile(s).
add_filter( 'activitypub_activity_user_object_array', function ( $array, $id, $object ) {
	$author_url = $object->get_id();

	$array['attachment'] = array(
		array(
			'type'  => 'PropertyValue',
			'name'  => __( 'Profile', 'activitypub' ),
			'value' => html_entity_decode(
				'<a rel="me" title="' . esc_attr( $author_url ) . '" target="_blank" href="' . esc_url( $author_url ) . '">' . wp_parse_url( $author_url, PHP_URL_HOST ) . '</a>',
				ENT_QUOTES,
				'UTF-8'
			),
		),
	);

	// @todo: Add other things.

	return $array;
}, 20, 3 );

// Save ActivityPub avatars locally.
add_filter( 'preprocess_comment', function ( $commentdata ) {
	if ( ! function_exists( '\\IndieBlocks\\store_image' ) ) {
		return $commentdata;
	}

	if ( empty( $commentdata['comment_meta']['protocol'] ) || 'activitypub' !== $commentdata['comment_meta']['protocol'] ) {
		return $commentdata;
	}

	if ( empty( $commentdata['comment_meta']['avatar_url'] ) || false === wp_http_validate_url( $commentdata['comment_meta']['avatar_url'] ) ) {
		return $commentdata;
	}

	$url      = $commentdata['comment_meta']['avatar_url'];
	$hash     = hash( 'sha256', esc_url_raw( $url ) ); // Create a (hopefully) unique, "reasonably short" filename.
	$ext      = pathinfo( $url, PATHINFO_EXTENSION );
	$filename = $hash . ( ! empty( $ext ) ? '.' . $ext : '' ); // Add a file extension if there was one.

	$dir = 'activitypub-avatars'; // The folder we're saving our avatars to.

	$upload_dir = wp_upload_dir();
	if ( ! empty( $upload_dir['subdir'] ) ) {
		// Add month and year, to be able to keep track of things.
		$dir .= '/' . trim( $upload_dir['subdir'], '/' );
	}

	$local_url = \IndieBlocks\store_image( $url, $filename, $dir ); // Attempt to store and resize the avatar.
	if ( null !== $local_url ) {
		$commentdata['comment_meta']['avatar_url'] = $local_url; // Replace the original URL by the local one.
	}

	return $commentdata;
} );

// Immediately stop processing Deletes of unkown, to our blog, actors.
add_filter( 'activitypub_defer_signature_verification', function ( $defer, $request ) {
	if ( ! class_exists( '\\Activitypub\\Collection\\Followers' ) || ! method_exists( \Activitypub\Collection\Followers::class, 'get_follower' ) ) {
		error_log( '[ActivityPub] The ActivitPub plugin may have been refactored.' );
		return $defer;
	}

	$type = $request->get_param( 'type' );
	if ( empty( $type ) || 'Delete' !== $type ) {
		return $defer;
	}

	$user_id = $request->get_param( 'user_id' );
	if ( empty( $user_id ) ) {
		return $defer;
	}

	$actor = $request->get_param( 'actor' );
	if ( empty( $actor ) ) {
		return $defer;
	}

	$object = $request->get_param( 'object' );
	if ( empty( $object ) ) {
		return $defer;
	}

	if ( $actor !== $object ) {
		return $defer;
	}

	if ( null !== \Activitypub\Collection\Followers::get_follower( (int) $user_id, esc_url_raw( $object ) ) ) {
		return $defer;
	}

	// We could skip signature verification, or ... just exit here.
	http_response_code( 202 );
	header( 'Content-Type: application/activity+json; charset=' . get_option( 'blog_charset' ) );
	echo json_encode( array() );
	exit;
}, 10, 2 );

// Filter both *activities* and *objects*.
add_filter( 'activitypub_activity_object_array', function ( $array, $class, $id, $object ) {
	if ( 'activity' === $class && isset( $array['object']['id'] ) ) {
		// If `$object` represents a post, attempt to fetch it.
		$post = get_post( url_to_postid( $array['object']['id'] ) );
	} elseif ( 'base_object' === $class && isset( $array['id'] ) ) {
		$post = get_post( url_to_postid( $array['id'] ) );
	}

	// Show "RSS-only" posts as unlisted.
	if ( ! empty( $post->post_author ) && has_category( 'rss-club', $post->ID ) ) {
		$to = isset( $array['to'] ) ? $array['to'] : array();
		$cc = isset( $array['cc'] ) ? $array['cc'] : array();

		// phpcs:ignore Generic.CodeAnalysis.AssignmentInCondition.Found,Squiz.PHP.DisallowMultipleAssignments.FoundInControlStructure
		if ( false !== ( $key = array_search( 'https://www.w3.org/ns/activitystreams#Public', $to, true ) ) ) {
			unset( $to[ $key ] ); // Remove the "Public" value ...
		}

		$cc[] = 'https://www.w3.org/ns/activitystreams#Public'; // And add it to `cc`.

		$to = array_values( $to ); // Renumber.
		$cc = array_values( array_unique( $cc ) ); // Remove duplicates.

		$array['to'] = $to;
		$array['cc'] = $cc;

		if ( 'activity' === $class ) {
			// Update object, too.
			$array['object']['to'] = $to;
			$array['object']['cc'] = $cc;
		}
	}

	// Attempt to correctly thread (certain) replies. Note that the ActivitPub
	// plugin already notifies mentioned Fediverse accounts and adds them to
	// both the activity and the object's `cc`.
	if ( ! empty( $post->post_type ) && in_array( $post->post_type, array( 'post', 'indieblocks_note' ), true ) ) {
		$blocks = parse_blocks( $post->post_content );

		// Using blocks right now, but we could run a regex on
		// `$post->post_content`, too, to allow posts that don't use a literal
		// Reply block. Or use a microformats parser.
		foreach ( $blocks as $block ) {
			if ( 'indieblocks/reply' === $block['blockName'] ) {
				$inner_html = $block['innerHTML'];
				break;
			}
		}

		if ( isset( $inner_html ) && preg_match( '~<p>.*?<a.+?href="(.+?)".*?>.+?</a>(.*?)</p>~s', $inner_html, $context ) ) {
			// Current object is a reply.
			if ( 0 === stripos( $context[1], esc_url_raw( home_url( '/' ) ) ) ) {
				// Reply-to-self.
				$parent = get_post( url_to_postid( $context[1] ) );

				if ( ! empty( $parent->post_type ) && in_array( $parent->post_type, array( 'post', 'indieblocks_note' ), true ) ) {
					// If we found a "parent" post of the "correct" post type, mark
					// the object a reply.
					if ( 'activity' === $class ) {
						$array['object']['inReplyTo'] = esc_url_raw( get_permalink( $parent ) );
					} elseif ( 'base_object' === $class ) {
						$array['inReplyTo'] = esc_url_raw( get_permalink( $parent ) );
					}

					// Ensure a post's ActivityPub representation contains only
					// the original's `e-content`. We could (and maybe should)
					// use `activitypub_the_content` instead, but then we'd lose
					// the reply context (and automatic notifying).
					if ( preg_match( '~<div class="e-content">.+?</div>~s', $post->post_content, $content ) ) {
						$copy               = clone $post;
						$copy->post_content = $content[0];

						// Regenerate "ActivityPub content" using the "slimmed
						// down" post content.
						$content = apply_filters( 'activitypub_the_content', $content[0], $copy );

						if ( 'activity' === $class ) {
							$array['object']['content'] = $content;

							foreach ( $array['object']['contentMap'] as $locale => $value ) {
								$array['object']['contentMap'][ $locale ] = $content;
							}
						} elseif ( 'base_object' === $class ) {
							$array['content'] = $content;

							foreach ( $array['contentMap'] as $locale => $value ) {
								$array['contentMap'][ $locale ] = $content;
							}
						}
					}
				}
			} elseif ( preg_match( '~<span class="p-author">@.+?@(.+?)</span>~', $context[2], $actor ) && filter_var( $actor[1], FILTER_VALIDATE_DOMAIN ) ) { // phpcs:ignore PHPCompatibility.Constants.NewConstants.filter_validate_domainFound
				// Could we be replying to a Fediverse URL?
				if ( 'activity' === $class ) {
					$array['object']['inReplyTo'] = esc_url_raw( $context[1] );
				} elseif ( 'base_object' === $class ) {
					$array['inReplyTo'] = esc_url_raw( $context[1] );
				}

				// Ensure a post's ActivityPub representation contains only
				// the original's `e-content`. We could (and maybe should)
				// use `activitypub_the_content` instead, but then we'd lose
				// the reply context (and automatic notifying).
				if ( preg_match( '~<div class="e-content">.+?</div>~s', $post->post_content, $content ) ) {
					$copy               = clone $post;
					$copy->post_content = $content[0];

					// Regenerate "ActivityPub content" using the "slimmed
					// down" post content.
					$content = apply_filters( 'activitypub_the_content', $content[0], $copy );

					if ( 'activity' === $class ) {
						$array['object']['content'] = $content;

						foreach ( $array['object']['contentMap'] as $locale => $value ) {
							$array['object']['contentMap'][ $locale ] = $content;
						}
					} elseif ( 'base_object' === $class ) {
						$array['content'] = $content;

						foreach ( $array['contentMap'] as $locale => $value ) {
							$array['contentMap'][ $locale ] = $content;
						}
					}
				}
			}
		}
	}

	return $array;
}, 20, 4 );

// Modify content "template" based on post type.
add_filter( 'activitypub_the_content', function ( $content, $post ) {
	$allowed_tags = array(
		'a'          => array(
			'href'  => array(),
			'title' => array(),
			'class' => array(),
			'rel'   => array(),
		),
		'br'         => array(),
		'p'          => array(
			'class' => array(),
		),
		'span'       => array(
			'class' => array(),
		),
		'ul'         => array(),
		'ol'         => array(
			'reversed' => array(),
			'start'    => array(),
		),
		'li'         => array(
			'value' => array(),
		),
		'strong'     => array(
			'class' => array(),
		),
		'b'          => array(
			'class' => array(),
		),
		'i'          => array(
			'class' => array(),
		),
		'em'         => array(
			'class' => array(),
		),
		'blockquote' => array(),
		'cite'       => array(),
		'code'       => array(
			'class' => array(),
		),
		'pre'        => array(
			'class' => array(),
		),
	);

	$shortlink = wp_get_shortlink( $post->ID );
	if ( ! empty( $shortlink ) ) {
		$permalink = $shortlink;
	} else {
		$permalink = get_permalink( $post );
	}

	$content = apply_filters( 'the_content', $post->post_content );

	if ( in_array( $post->post_type, array( 'post', 'page' ), true ) ) {
		// Strip tags and shorten.
		$content = wp_trim_words( $content, 25, ' […]' ); // Also strips all HTML.

		// Prepend the title.
		$content = '<p><strong>' . get_the_title( $post ) . '</strong></p><p>' . $content . '</p>';

		// Append a permalink.
		$content .= '<p>(<a href="' . esc_url( $permalink ) . '">' . esc_html( $permalink ) . '</a>)</p>';

	} else {
		// Append a permalink.
		$content .= '<p>(<a href="' . esc_url( $permalink ) . '">' . esc_html( $permalink ) . '</a>)</p>';
	}

	$content = wp_kses( $content, $allowed_tags );
	// Strip whitespace, but ignore `pre` elements' contents.
	$content = preg_replace( '~<pre[^>]*>.*?</pre>(*SKIP)(*FAIL)|\r|\n|\t~s', '', $content );
	// Collapse newlines inside (`code` elements inside) `pre` elements.
	if ( preg_match_all('~<pre[^>]*><code[^>]*>(.*?)</code></pre>~s', $content, $matches ) ) {
		foreach ( $matches[1] as $match ) {
			$content = str_replace( $match, preg_replace( '~\n{3,}~', "\n\n", trim( $match ) ), $content );
		}
	}

	return trim( $content );
}, 20, 2 );