wordpress-activitypub/includes/functions.php

<?php
namespace Activitypub;

define( 'AS_PUBLIC', 'https://www.w3.org/ns/activitystreams#Public' );

/**
 * Returns the ActivityPub default JSON-context
 *
 * @return array the activitypub context
 */
function get_context() {
	$context = array(
		'https://www.w3.org/ns/activitystreams',
		'https://w3id.org/security/v1',
		array(
			'manuallyApprovesFollowers' => 'as:manuallyApprovesFollowers',
			'PropertyValue' => 'schema:PropertyValue',
			'schema' => 'http://schema.org#',
			'pt' => 'https://joinpeertube.org/ns#',
			'toot' => 'http://joinmastodon.org/ns#',
			'value' => 'schema:value',
			'Hashtag' => 'as:Hashtag',
			'featured' => array(
				'@id' => 'toot:featured',
				'@type' => '@id',
			),
			'featuredTags' => array(
				'@id' => 'toot:featuredTags',
				'@type' => '@id',
			),
		),
	);

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

function safe_remote_post( $url, $body, $user_id ) {
	$date = \gmdate( 'D, d M Y H:i:s T' );
	$digest = \Activitypub\Signature::generate_digest( $body );
	$signature = \Activitypub\Signature::generate_signature( $user_id, $url, $date, $digest );

	$wp_version = \get_bloginfo( 'version' );
	$user_agent = \apply_filters( 'http_headers_useragent', 'WordPress/' . $wp_version . '; ' . \get_bloginfo( 'url' ) );
	$args = array(
		'timeout' => 100,
		'limit_response_size' => 1048576,
		'redirection' => 3,
		'user-agent' => "$user_agent; ActivityPub",
		'headers' => array(
			'Accept' => 'application/activity+json',
			'Content-Type' => 'application/activity+json',
			'Digest' => "SHA-256=$digest",
			'Signature' => $signature,
			'Date' => $date,
		),
		'body' => $body,
	);

	$response = \wp_safe_remote_post( $url, $args );

	\do_action( 'activitypub_safe_remote_post_response', $response, $url, $body, $user_id );

	return $response;
}

function forward_remote_post( $url, $body, $user_id ) {
	$date = \gmdate( 'D, d M Y H:i:s T' );
	$digest = \Activitypub\Signature::generate_digest( $body );
	$signature = \Activitypub\Signature::generate_signature( 1, $url, $date );

	$wp_version = \get_bloginfo( 'version' );
	$user_agent = \apply_filters( 'http_headers_useragent', 'WordPress/' . $wp_version . '; ' . \get_bloginfo( 'url' ) );
	$args = array(
		'timeout' => 100,
		'limit_response_size' => 1048576,
		'redirection' => 3,
		'user-agent' => "$user_agent; ActivityPub",
		'headers' => array(
			'Accept' => 'application/activity+json',
			'Content-Type' => 'application/activity+json',
			'Digest' => "SHA-256=$digest",
			'Signature' => $signature,
			'Date' => $date,
		),
		'body' => $body,
	);

	$response = \wp_safe_remote_post( $url, $args );

	\do_action( 'activitypub_forward_remote_post_response', $response, $url, $body, $user_id );

	return $response;
}

function safe_remote_get( $url, $user_id ) {
	$date = \gmdate( 'D, d M Y H:i:s T' );
	$signature = \Activitypub\Signature::generate_signature( $user_id, $url, $date );

	$wp_version = \get_bloginfo( 'version' );
	$user_agent = \apply_filters( 'http_headers_useragent', 'WordPress/' . $wp_version . '; ' . \get_bloginfo( 'url' ) );
	$args = array(
		'timeout' => 100,
		'limit_response_size' => 1048576,
		'redirection' => 3,
		'user-agent' => "$user_agent; ActivityPub",
		'headers' => array(
			'Accept' => 'application/activity+json',
			'Content-Type' => 'application/activity+json',
			'Signature' => $signature,
			'Date' => $date,
		),
	);

	$response = \wp_safe_remote_get( $url, $args );

	\do_action( 'activitypub_safe_remote_get_response', $response, $url, $user_id );

	return $response;
}

/**
 * Returns a users WebFinger "resource"
 *
 * @param int $user_id
 *
 * @return string The user-resource
 */
function get_webfinger_resource( $user_id ) {
	// use WebFinger plugin if installed
	if ( \function_exists( '\get_webfinger_resource' ) ) {
		return \get_webfinger_resource( $user_id, false );
	}

	$user = \get_user_by( 'id', $user_id );

	return $user->user_login . '@' . \wp_parse_url( \home_url(), \PHP_URL_HOST );
}

/**
 * [get_metadata_by_actor description]
 *
 * @param sting $actor
 *
 * @return array
 */
function get_remote_metadata_by_actor( $actor ) {
	$metadata = \get_transient( 'activitypub_' . $actor );

	if ( $metadata ) {
		return $metadata;
	}

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

	$user = \get_users(
		array(
			'number' => 1,
			'who'    => 'authors',
			'fields' => 'ID',
		)
	);

	// we just need any user to generate a request signature
	$user_id = \reset( $user );

	$response = \Activitypub\safe_remote_get( $actor, $user_id );

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

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

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

	\set_transient( 'activitypub_' . $actor, $metadata, WEEK_IN_SECONDS );

	return $metadata;
}

/**
 * [get_inbox_by_actor description]
 * @param  [type] $actor [description]
 * @return [type]        [description]
 */
function get_inbox_by_actor( $actor ) {
	$metadata = \Activitypub\get_remote_metadata_by_actor( $actor );

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

	if ( isset( $metadata['endpoints'] ) && isset( $metadata['endpoints']['sharedInbox'] ) ) {
		return $metadata['endpoints']['sharedInbox'];
	}

	if ( \array_key_exists( 'inbox', $metadata ) ) {
		return $metadata['inbox'];
	}

	return new \WP_Error( 'activitypub_no_inbox', \__( 'No "Inbox" found', 'activitypub' ), $metadata );
}

/**
 * [get_inbox_by_actor description]
 * @param  [type] $actor [description]
 * @return [type]        [description]
 */
function get_publickey_by_actor( $actor, $key_id ) {
	$metadata = \Activitypub\get_remote_metadata_by_actor( $actor );

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

	if (
		isset( $metadata['publicKey'] ) &&
		isset( $metadata['publicKey']['id'] ) &&
		isset( $metadata['publicKey']['owner'] ) &&
		isset( $metadata['publicKey']['publicKeyPem'] ) &&
		$key_id === $metadata['publicKey']['id'] &&
		$actor === $metadata['publicKey']['owner']
	) {
		return $metadata['publicKey']['publicKeyPem'];
	}

	return new \WP_Error( 'activitypub_no_public_key', \__( 'No "Public-Key" found', 'activitypub' ), $metadata );
}

function get_follower_inboxes( $user_id ) {
	$followers = \Activitypub\Peer\Followers::get_followers( $user_id );
	$inboxes = array();

	foreach ( $followers as $follower ) {
		$inbox = \Activitypub\get_inbox_by_actor( $follower );
		if ( ! $inbox || \is_wp_error( $inbox ) ) {
			continue;
		}
		// init array if empty
		if ( ! isset( $inboxes[ $inbox ] ) ) {
			$inboxes[ $inbox ] = array();
		}
		$inboxes[ $inbox ][] = $follower;
	}

	return $inboxes;
}

function get_mentioned_inboxes( $mentions ) {
	$inboxes = array();

	foreach ( $mentions as $mention ) {
		$inbox = \Activitypub\get_inbox_by_actor( $mention['href'] );
		if ( ! $inbox || \is_wp_error( $inbox ) ) {
			continue;
		}
		// init array if empty
		if ( ! isset( $inboxes[ $inbox ] ) ) {
			$inboxes[ $inbox ] = array();
		}
		$inboxes[ $inbox ][] = $mention;
	}

	return $inboxes;
}

function get_identifier_settings( $user_id ) {
	?>
<table class="form-table">
	<tbody>
		<tr>
			<th scope="row">
				<label><?php \esc_html_e( 'Profile identifier', 'activitypub' ); ?></label>
			</th>
			<td>
				<p><code><?php echo \esc_html( \Activitypub\get_webfinger_resource( $user_id ) ); ?></code> or <code><?php echo \esc_url( \get_author_posts_url( $user_id ) ); ?></code></p>
				<?php // translators: the webfinger resource ?>
				<p class="description"><?php \printf( \esc_html__( 'Try to follow "@%s" in the Mastodon/Friendica search field.', 'activitypub' ), \esc_html( \Activitypub\get_webfinger_resource( $user_id ) ) ); ?></p>
			</td>
		</tr>
	</tbody>
</table>
	<?php
}

function get_followers( $user_id ) {
	$followers = \Activitypub\Peer\Followers::get_followers( $user_id );

	if ( ! $followers ) {
		return array();
	}

	return $followers;
}

function count_followers( $user_id ) {
	$followers = \Activitypub\get_followers( $user_id );

	return \count( $followers );
}

/**
 * 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;
}

/**
 * Verify if in_replyto_url is a local comment,
 * Or if it is a previously received remote comment
 * 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'] ) {
		//is local post or comment
		\parse_str( $url_maybe_id['query'], $reply_query );
		if ( isset( $reply_query['ap_comment_id'] ) && is_int( $reply_query['ap_comment_id'] ) ) {
			//is local comment
			return $reply_query['ap_comment_id'];
		} else {
			//not a comment
			return null;
		}
	} 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_ap_comment() {
	$comment_id = get_query_var( 'ap_comment_id', 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;
}

/**
 * Verify if url is a /replies endoint,
 * return int true
 */
function is_ap_replies() {
	global $wp;
	$replies = get_query_var( 'replies' );
	if ( $replies ) {
		return $replies;
	}
	return null;
}

/**
 * Get tagged users from received AP object meta
 * @param string $object_id a comment_id to search
 * @param boolean $post defaults to searching a comment_id
 * @return array of tagged users
 */
function get_recipients( $object_id, $post = null ) {
	$tagged_users_name = 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 ) ) {
		$tagged_users_name[] = \Activitypub\url_to_webfinger( $ap_object['actor'] );
		if ( ! empty( $ap_object['object']['tag'] ) ) {
			$author_post_url = \get_author_posts_url( $ap_object['user_id'] );
			foreach ( $ap_object['object']['tag'] as $tag ) {
				if ( $author_post_url == $tag['href'] ) {
					continue;
				}
				if ( in_array( 'Mention', $tag ) ) {
					$tagged_users_name[] = $tag['name'];
				}
			}
		}
		return implode( ' ', $tagged_users_name );
	}
}

/**
 * Add summary to reply
 */
function get_summary( $comment_id ) {
	$ap_object = \unserialize( \get_comment_meta( $comment_id, 'ap_object', true ) );
	if ( ! empty( $ap_object ) ) {
		if ( ! empty( $ap_object['object']['summary'] ) ) {
			return \esc_attr( $ap_object['object']['summary'] );
		}
	}
}

/**
 * parse content for tags to transform
 * @param string $content to search
 */
function transform_tags( $content ) {
	//#tags

	//@Mentions
	$mentions = null;
	$webfinger_tags = \Activitypub\webfinger_extract( $content );
	if ( ! empty( $webfinger_tags ) ) {
		foreach ( $webfinger_tags[0] as $webfinger_tag ) {
			$ap_profile = \Activitypub\Rest\Webfinger::webfinger_lookup( $webfinger_tag );
			if ( ! empty( $ap_profile ) ) {
				$short_tag = \Activitypub\webfinger_short_tag( $webfinger_tag );
				$webfinger_link = "<span class='h-card'><a href=\"{$ap_profile['href']}\" class='u-url mention' rel='noopener noreferer' target='_blank'>{$short_tag}</a></span>";
				$content = str_replace( $webfinger_tag, $webfinger_link, $content );
				$mentions[] = $ap_profile;
			}
		}
	}
	// Return mentions separately to attach to comment/post meta
	$content_mentions['mentions'] = $mentions;
	$content_mentions['content'] = $content;
	return $content_mentions;
}

function tag_user( $recipient ) {
	$tagged_user = array(
		'type' => 'Mention',
		'href' => $recipient,
		'name' => \Activitypub\url_to_webfinger( $recipient ),
	);
	$tag[] = $tagged_user;
	return $tag;
}

/**
 * @param string $content
 * @return array of all matched webfinger
 */
function webfinger_extract( $string ) {
	preg_match_all( '/@[\._a-zA-Z0-9-]+@[\._a-zA-Z0-9-]+/i', $string, $matches );
	return $matches;
}

/**
 * @param string full $webfinger
 * @return string short @webfinger
 */
function webfinger_short_tag( $webfinger ) {
	$short_tag = explode( '@', $webfinger );
	return '@' . $short_tag[1];
}

/**
 * @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 = parse_url( $user_url, PHP_URL_HOST );
	$webfinger = '@' . $user_name . '@' . $url_host;
	return $webfinger;
}

/**
 * Transform comment url, replace #fragment with ?query
 *
 * AP Object ID must be unique
 *
 * https://www.w3.org/TR/activitypub/#obj-id
 * https://github.com/tootsuite/mastodon/issues/13879
 */
function normalize_comment_url( $comment ) {
	$comment_id = explode( '#comment-', \get_comment_link( $comment ) );
	$comment_id = $comment_id[0] . '?ap_comment_id=' . $comment_id[1];
	return $comment_id;
}

/**
 * Set ap_comment_id
 *
 * AP Object ID must be unique
 *
 * https://www.w3.org/TR/activitypub/#obj-id
 * https://github.com/tootsuite/mastodon/issues/13879
 */
function set_ap_comment_id( $comment ) {
	$ap_comment_id = add_query_arg(
		array(
			'p' => $comment->comment_post_ID,
			'ap_comment_id' => $comment->comment_ID, //should probably rename to ap_comment or something
		),
		trailingslashit( site_url() )
	);
	return $ap_comment_id;
}
/*  comment_id_to_url( $comment_id ) {
		//get remote from post_id from comment meta
		//get local normalized comment_link
	}
*/

/**
 * 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';//is unlisted even relevant?
	}
	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';
		}
	}
}