wordpress-activitypub/includes/functions.php

<?php
namespace Activitypub;

use WP_Error;
use Activitypub\Http;
use Activitypub\Activity\Activity;
use Activitypub\Collection\Followers;

/**
 * Returns the ActivityPub default JSON-context
 *
 * @return array the activitypub context
 */
function get_context() {
	$context = Activity::CONTEXT;

	return \apply_filters( 'activitypub_json_context', $context );
}

function safe_remote_post( $url, $body, $user_id ) {
	return Http::post( $url, $body, $user_id );
}

function safe_remote_get( $url ) {
	return Http::get( $url );
}

/**
 * Returns a users WebFinger "resource"
 *
 * @param int $user_id The User-ID.
 *
 * @return string The User-Resource.
 */
function get_webfinger_resource( $user_id ) {
	return Webfinger::get_user_resource( $user_id );
}

/**
 * Requests the Meta-Data from the Actors profile
 *
 * @param string $actor  The Actor URL.
 * @param bool   $cached If the result should be cached.
 *
 * @return array|WP_Error The Actor profile as array or WP_Error on failure.
 */
function get_remote_metadata_by_actor( $actor, $cached = true ) {
	$pre = apply_filters( 'pre_get_remote_metadata_by_actor', false, $actor );
	if ( $pre ) {
		return $pre;
	}
	if ( preg_match( '/^@?' . ACTIVITYPUB_USERNAME_REGEXP . '$/i', $actor ) ) {
		$actor = Webfinger::resolve( $actor );
	}

	if ( ! $actor ) {
		return new WP_Error( 'activitypub_no_valid_actor_identifier', \__( 'The "actor" identifier is not valid', 'activitypub' ), array( 'status' => 404, 'actor' => $actor ) );
	}

	if ( is_wp_error( $actor ) ) {
		return $actor;
	}

	$transient_key = 'activitypub_' . $actor;

	// only check the cache if needed.
	if ( $cached ) {
		$metadata = \get_transient( $transient_key );

		if ( $metadata ) {
			return $metadata;
		}
	}

	if ( ! \wp_http_validate_url( $actor ) ) {
		$metadata = new WP_Error( 'activitypub_no_valid_actor_url', \__( 'The "actor" is no valid URL', 'activitypub' ), array( 'status' => 400, 'actor' => $actor ) );
		return $metadata;
	}

	$response = Http::get( $actor );

	if ( \is_wp_error( $response ) ) {
		return $response;
	}

	$metadata = \wp_remote_retrieve_body( $response );
	$metadata = \json_decode( $metadata, true );

	if ( ! $metadata ) {
		$metadata = new WP_Error( 'activitypub_invalid_json', \__( 'No valid JSON data', 'activitypub' ), array( 'status' => 400, 'actor' => $actor ) );
		return $metadata;
	}

	\set_transient( $transient_key, $metadata, WEEK_IN_SECONDS );

	return $metadata;
}

/**
 * Returns the followers of a given user.
 *
 * @param int $user_id The User-ID.
 *
 * @return array The followers.
 */
function get_followers( $user_id ) {
	return Followers::get_followers( $user_id );
}

/**
 * Count the number of followers for a given user.
 *
 * @param int $user_id The User-ID.
 *
 * @return int The number of followers.
 */
function count_followers( $user_id ) {
	return Followers::count_followers( $user_id );
}

/**
 * Examine a url and try to determine the author ID it represents.
 *
 * Checks are supposedly from the hosted site blog.
 *
 * @param string $url Permalink to check.
 *
 * @return int User ID, or 0 on failure.
 */
function url_to_authorid( $url ) {
	global $wp_rewrite;

	// check if url hase the same host
	if ( \wp_parse_url( \site_url(), \PHP_URL_HOST ) !== \wp_parse_url( $url, \PHP_URL_HOST ) ) {
		return 0;
	}

	// first, check to see if there is a 'author=N' to match against
	if ( \preg_match( '/[?&]author=(\d+)/i', $url, $values ) ) {
		$id = \absint( $values[1] );
		if ( $id ) {
			return $id;
		}
	}

	// check to see if we are using rewrite rules
	$rewrite = $wp_rewrite->wp_rewrite_rules();

	// not using rewrite rules, and 'author=N' method failed, so we're out of options
	if ( empty( $rewrite ) ) {
		return 0;
	}

	// generate rewrite rule for the author url
	$author_rewrite = $wp_rewrite->get_author_permastruct();
	$author_regexp = \str_replace( '%author%', '', $author_rewrite );

	// match the rewrite rule with the passed url
	if ( \preg_match( '/https?:\/\/(.+)' . \preg_quote( $author_regexp, '/' ) . '([^\/]+)/i', $url, $match ) ) {
		$user = \get_user_by( 'slug', $match[2] );
		if ( $user ) {
			return $user->ID;
		}
	}

	return 0;
}

/**
 * Examine a comment ID and look up an existing comment it represents.
 *
 * @param string $id ActivityPub object ID (usually a URL) to check.
 *
 * @return WP_Comment, or undef if no comment could be found.
 */
function object_id_to_comment( $id ) {
	$comment_query = new \WP_Comment_Query(
		array(
			'meta_key' => 'source_id',
			'meta_value' => $id,
		)
	);
	if ( ! $comment_query->comments ) {
		return;
	}
	if ( count( $comment_query->comments ) > 1 ) {
		\error_log( "More than one comment under {$id}" );
		return;
	}
	return $comment_query->comments[0];
}

/**
 * Examine an activity object and find the post that the specified URL field refers to.
 *
 * @param string $field_name The name of the URL field in the object to query.
 *
 * @return int Post ID, or null on failure.
 */
function object_to_post_id_by_field_name( $object, $field_name ) {
	if ( ! isset( $object['object'][ $field_name ] ) ) {
		return;
	}
	$result = \url_to_postid( $object['object'][ $field_name ] );
	if ( $result > 0 ) {
		return $result;
	}
}

/**
 * Verify if in_replyto_url is a local Post,
 * (For backwards compatibility)
 *
 * @param string activitypub object id URI
 * @return int post_id
 */
function url_to_postid( $in_replyto_url ) {
	if ( ! empty( $in_replyto_url ) ) {
		$tentative_postid = \url_to_postid( $in_replyto_url );
		if ( is_null( $tentative_postid ) ) {
			$post_types = \get_option( 'activitypub_support_post_types', array( 'post', 'page' ) );
			$query_args = array(
				'type' => $post_types,
				'meta_query' => array(
					array(
						'key' => 'activitypub_canonical_url',
						'value' => $in_replyto_url,
					),
				),
			);
			$posts_query = new \WP_Query();
			$posts = $posts_query->query( $query_args );
			$found_post_ids = array();
			if ( $posts ) {
				foreach ( $posts as $post ) {
					$found_post_ids[] = $post->comment_ID;
				}
				return $found_post_ids[0];
			}
		} else {
			return $tentative_postid;
		}
	}
	return null;
}

/**
 * Verify if in_replyto_url is a local comment,
 * Or if it is a previously received remote comment
 * (For threading comments locally)
 *
 * @param string activitypub object id URI
 * @return int comment_id
 */
function url_to_commentid( $in_replyto_url ) {
	if ( empty( $in_replyto_url ) ) {
		return null;
	}

	//rewrite for activitypub object id simplification
	$url_maybe_id = \wp_parse_url( $in_replyto_url );
	if ( site_url() === $url_maybe_id['scheme'] . '://' . $url_maybe_id['host'] && ! empty( $url_maybe_id['query'] ) ) {
		//is local post or comment
		\parse_str( $url_maybe_id['query'], $reply_query );
		if ( isset( $reply_query['replytocom'] ) ) {
			//is local comment
			return $reply_query['replytocom'];
		}
	} else {
		//is remote url
		//verify if in_replyto_url corresponds to a previously received comment
		$comment_args = array(
			'type' => 'activitypub',
			'meta_query' => array(
				array(
					'key' => 'source_url', // $object['object']['id']
					'value' => $in_replyto_url,
				),
			),
		);
		$comments_query = new \WP_Comment_Query();
		$comments = $comments_query->query( $comment_args );
		$found_comment_ids = array();
		if ( $comments ) {
			foreach ( $comments as $comment ) {
				$found_comment_ids[] = $comment->comment_ID;
			}
			return $found_comment_ids[0];
		}
	}
	return null;
}

/**
 * Verify if url is a wp_ap_comment,
 * Or if it is a previously received remote comment
 *
 * @return int comment_id
 */
function is_comment() {
	$comment_id = get_query_var( 'replytocom', null );
	if ( ! is_null( $comment_id ) ) {
		$comment = \get_comment( $comment_id );
		// Only return local origin comments
		if ( $comment->user_id ) {
			return $comment_id;
		}
	}
	return null;
}

/**
 * Get recipients to insert/tag in reply tag from received AP object meta
 * @param string $object_id a comment_id to search
 * @param boolean $post defaults to searching a comment_id
 * @return string space separated webfinger of tagged users
 */
function reply_recipients( $object_id, $post = null ) {
	$recipients = null;
	if ( $post ) {
		//post
		$ap_object = \unserialize( \get_post_meta( $object_id, 'ap_object', true ) );
	} else {
		//comment
		$ap_object = \unserialize( \get_comment_meta( $object_id, 'ap_object', true ) );
	}

	if ( ! empty( $ap_object ) ) {
		// Replying to remote comments.
		$recipients[] = \ActivityPub\url_to_webfinger( $ap_object['actor'] ); // Reply to Object actor!

		if ( ! empty( $ap_object['object']['tag'] ) ) { // Reply to other tagged users.
			if ( isset( $ap_object['user_id'] ) ) {
				$author_post_url = \get_author_posts_url( $ap_object['user_id'] );// ignore self tag.
				foreach ( $ap_object['object']['tag'] as $tag ) { // Other tagged users
					if ( $author_post_url === $tag['href'] ) {
						continue;
					}
					if ( in_array( 'Mention', $tag ) ) {
						$recipients[] = $tag['name'];
					}
				}
			}
		}
		return implode( ' ', $recipients );
	} else {
		// Replying to self with others.
		$comment = \get_comment( $object_id );
		preg_match_all( '/@' . ACTIVITYPUB_USERNAME_REGEXP . '/', $comment->comment_content, $recipients );
		return implode( ' ', $recipients[0] );
	}
}

/**
 * @param string $user_url
 * @return string $webfinger
 */
function url_to_webfinger( $user_url ) {
	$user_url = \untrailingslashit( $user_url );
	$user_url_array = \explode( '/', $user_url );
	$user_name = \end( $user_url_array );
	$url_host = \wp_parse_url( $user_url, PHP_URL_HOST );
	$webfinger = '@' . $user_name . '@' . $url_host;
	return $webfinger;
}

/**
 * Determine AP audience of incoming object
 * @param string $object
 * @return string audience
 */
function get_audience( $object ) {
	if ( in_array( AS_PUBLIC, $object['to'] ) ) {
		return 'public';
	}
	if ( in_array( AS_PUBLIC, $object['cc'] ) ) {
		return 'unlisted';
	}
	if ( ! in_array( AS_PUBLIC, $object['to'] ) && ! in_array( AS_PUBLIC, $object['cc'] ) ) {
		$author_post_url = get_author_posts_url( $object['user_id'] );
		if ( in_array( $author_post_url, $object['cc'] ) ) {
			return 'followers_only';
		}
		if ( in_array( $author_post_url, $object['to'] ) ) {
			return 'private';
		}
	}
}

/**
 * Check for Tombstone Objects
 *
 * @see https://www.w3.org/TR/activitypub/#delete-activity-outbox
 *
 * @param WP_Error $wp_error A WP_Error-Response of an HTTP-Request
 *
 * @return boolean true if HTTP-Code is 410 or 404
 */
function is_tombstone( $wp_error ) {
	if ( ! is_wp_error( $wp_error ) ) {
		return false;
	}

	if ( in_array( (int) $wp_error->get_error_code(), array( 404, 410 ), true ) ) {
		return true;
	}

	return false;
}

/**
 * Get the REST URL relative to this plugin's namespace.
 *
 * @param string $path Optional. REST route path. Otherwise this plugin's namespaced root.
 *
 * @return string REST URL relative to this plugin's namespace.
 */
function get_rest_url_by_path( $path = '' ) {
	// we'll handle the leading slash.
	$path = ltrim( $path, '/' );
	$namespaced_path = sprintf( '/%s/%s', ACTIVITYPUB_REST_NAMESPACE, $path );
	return \get_rest_url( null, $namespaced_path );
}

/**
 * Convert a string from camelCase to snake_case.
 *
 * @param string $string The string to convert.
 *
 * @return string The converted string.
 */
// phpcs:ignore Universal.NamingConventions.NoReservedKeywordParameterNames.stringFound
function camel_to_snake_case( $string ) {
	return strtolower( preg_replace( '/(?<!^)[A-Z]/', '_$0', $string ) );
}

/**
 * Convert a string from snake_case to camelCase.
 *
 * @param string $string The string to convert.
 *
 * @return string The converted string.
 */
// phpcs:ignore Universal.NamingConventions.NoReservedKeywordParameterNames.stringFound
function snake_to_camel_case( $string ) {
	return lcfirst( str_replace( '_', '', ucwords( $string, '_' ) ) );
}

/**
 * Escapes a Tag, to be used as a hashtag.
 *
 * @param string $string The string to escape.
 *
 * @return string The escaped hastag.
 */
function esc_hashtag( $string ) {

	$hashtag = \wp_specialchars_decode( $string, ENT_QUOTES );
	// Remove all characters that are not letters, numbers, or underscores.
	$hashtag = \preg_replace( '/emoji-regex(*SKIP)(?!)|[^\p{L}\p{Nd}_]+/u', '_', $hashtag );

	// Capitalize every letter that is preceded by an underscore.
	$hashtag = preg_replace_callback(
		'/_(.)/',
		function ( $matches ) {
			return '' . strtoupper( $matches[1] );
		},
		$hashtag
	);

	// Add a hashtag to the beginning of the string.
	$hashtag = ltrim( $hashtag, '#' );
	$hashtag = '#' . $hashtag;

	/**
	 * Allow defining your own custom hashtag generation rules.
	 *
	 * @param string $hashtag The hashtag to be returned.
	 * @param string $string  The original string.
	 */
	$hashtag = apply_filters( 'activitypub_esc_hashtag', $hashtag, $string );

	return esc_html( $hashtag );
}

/**
 * Check if a request is for an ActivityPub request.
 *
 * @return bool False by default.
 */
function is_activitypub_request() {
	global $wp_query;

	/*
	 * ActivityPub requests are currently only made for
	 * author archives, singular posts, and the homepage.
	 */
	if ( ! \is_author() && ! \is_singular() && ! \is_home() && ! defined( '\REST_REQUEST' ) ) {
		return false;
	}

	// One can trigger an ActivityPub request by adding ?activitypub to the URL.
	// phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.VariableRedeclaration
	global $wp_query;
	if ( isset( $wp_query->query_vars['activitypub'] ) ) {
		return true;
	}

	/*
	 * The other (more common) option to make an ActivityPub request
	 * is to send an Accept header.
	 */
	if ( isset( $_SERVER['HTTP_ACCEPT'] ) ) {
		$accept = sanitize_text_field( wp_unslash( $_SERVER['HTTP_ACCEPT'] ) );

		/*
		 * $accept can be a single value, or a comma separated list of values.
		 * We want to support both scenarios,
		 * and return true when the header includes at least one of the following:
		 * - application/activity+json
		 * - application/ld+json
		 * - application/json
		 */
		if ( preg_match( '/(application\/(ld\+json|activity\+json|json))/i', $accept ) ) {
			return true;
		}
	}

	return false;
}

/**
 * This function checks if a user is disabled for ActivityPub.
 *
 * @param int $user_id The User-ID.
 *
 * @return boolean True if the user is disabled, false otherwise.
 */
function is_user_disabled( $user_id ) {
	$return = false;

	switch ( $user_id ) {
		// if the user is the application user, it's always enabled.
		case \Activitypub\Collection\Users::APPLICATION_USER_ID:
			$return = false;
			break;
		// if the user is the blog user, it's only enabled in single-user mode.
		case \Activitypub\Collection\Users::BLOG_USER_ID:
			if ( is_user_type_disabled( 'blog' ) ) {
				$return = true;
				break;
			}

			$return = false;
			break;
		// if the user is any other user, it's enabled if it can publish posts.
		default:
			if ( ! \get_user_by( 'id', $user_id ) ) {
				$return = true;
				break;
			}

			if ( is_user_type_disabled( 'user' ) ) {
				$return = true;
				break;
			}

			if ( ! \user_can( $user_id, 'publish_posts' ) ) {
				$return = true;
				break;
			}

			$return = false;
			break;
	}

	return apply_filters( 'activitypub_is_user_disabled', $return, $user_id );
}

/**
 * Checks if a User-Type is disabled for ActivityPub.
 *
 * This function is used to check if the 'blog' or 'user'
 * type is disabled for ActivityPub.
 *
 * @param enum $type Can be 'blog' or 'user'.
 *
 * @return boolean True if the user type is disabled, false otherwise.
 */
function is_user_type_disabled( $type ) {
	switch ( $type ) {
		case 'blog':
			if ( \defined( 'ACTIVITYPUB_SINGLE_USER_MODE' ) ) {
				if ( ACTIVITYPUB_SINGLE_USER_MODE ) {
					$return = false;
					break;
				}
			}

			if ( \defined( 'ACTIVITYPUB_DISABLE_BLOG_USER' ) ) {
				$return = ACTIVITYPUB_DISABLE_BLOG_USER;
				break;
			}

			if ( '1' !== \get_option( 'activitypub_enable_blog_user', '0' ) ) {
				$return = true;
				break;
			}

			$return = false;
			break;
		case 'user':
			if ( \defined( 'ACTIVITYPUB_SINGLE_USER_MODE' ) ) {
				if ( ACTIVITYPUB_SINGLE_USER_MODE ) {
					$return = true;
					break;
				}
			}

			if ( \defined( 'ACTIVITYPUB_DISABLE_USER' ) ) {
				$return = ACTIVITYPUB_DISABLE_USER;
				break;
			}

			if ( '1' !== \get_option( 'activitypub_enable_users', '1' ) ) {
				$return = true;
				break;
			}

			$return = false;
			break;
		default:
			$return = new WP_Error( 'activitypub_wrong_user_type', __( 'Wrong user type', 'activitypub' ), array( 'status' => 400 ) );
			break;
	}

	return apply_filters( 'activitypub_is_user_type_disabled', $return, $type );
}

/**
 * Check if the blog is in single-user mode.
 *
 * @return boolean True if the blog is in single-user mode, false otherwise.
 */
function is_single_user() {
	if (
		false === is_user_type_disabled( 'blog' ) &&
		true === is_user_type_disabled( 'user' )
	) {
		return true;
	}

	return false;
}

/**
 * Check if a site supports the block editor.
 *
 * @return boolean True if the site supports the block editor, false otherwise.
 */
function site_supports_blocks() {
	if ( \version_compare( \get_bloginfo( 'version' ), '5.9', '<' ) ) {
		return false;
	}

	if ( ! \function_exists( 'register_block_type_from_metadata' ) ) {
		return false;
	}

	/**
	 * Allow plugins to disable block editor support,
	 * thus disabling blocks registered by the ActivityPub plugin.
	 *
	 * @param boolean $supports_blocks True if the site supports the block editor, false otherwise.
	 */
	return apply_filters( 'activitypub_site_supports_blocks', true );
}

/**
 * Check if data is valid JSON.
 *
 * @param string $data The data to check.
 *
 * @return boolean True if the data is JSON, false otherwise.
 */
function is_json( $data ) {
	return \is_array( \json_decode( $data, true ) ) ? true : false;
}

/**
 * Check if a blog is public based on the `blog_public` option
 *
 * @return bollean True if public, false if not
 */
function is_blog_public() {
	return (bool) apply_filters( 'activitypub_is_blog_public', \get_option( 'blog_public', 1 ) );
}