get_active_blog_for_user( int $user_id ): WP_Site|object|null|false

45function get_active_blog_for_user( $user_id ) {46	$blogs = get_blogs_of_user( $user_id );47	if ( empty( $blogs ) ) {48		return null;49	}50 51	if ( ! is_multisite() ) {52		return $blogs[ get_current_blog_id() ];53	}54 55	$primary      = null;56	$primary_blog = get_user_meta( $user_id, 'primary_blog', true );57	$first_blog   = current( $blogs );58	if ( false !== $primary_blog ) {59		if ( ! isset( $blogs[ $primary_blog ] ) ) {60			update_user_meta( $user_id, 'primary_blog', $first_blog->userblog_id );61			$primary = get_site( $first_blog->userblog_id );62		} else {63			$primary = get_site( $primary_blog );64		}65	} else {66		// TODO: Review this call to add_user_to_blog too - to get here the user must have a role on this blog?67		$result = add_user_to_blog( $first_blog->userblog_id, $user_id, 'subscriber' );68 69		if ( ! is_wp_error( $result ) ) {70			update_user_meta( $user_id, 'primary_blog', $first_blog->userblog_id );71			$primary = $first_blog;72		}73	}74 75	if ( ( ! is_object( $primary ) )76		|| ( '1' === $primary->archived || '1' === $primary->spam || '1' === $primary->deleted )77	) {78		$blogs = get_blogs_of_user( $user_id, true ); // If a user's primary blog is shut down, check their other blogs.79		$ret   = false;80 81		if ( is_array( $blogs ) && count( $blogs ) > 0 ) {82			$current_network_id = get_current_network_id();83 84			foreach ( (array) $blogs as $blog_id => $blog ) {85				if ( $blog->site_id !== $current_network_id ) {86					continue;87				}88 89				$details = get_site( $blog_id );90				if ( is_object( $details )91					&& '0' === $details->archived && '0' === $details->spam && '0' === $details->deleted92				) {93					$ret = $details;94					if ( (int) get_user_meta( $user_id, 'primary_blog', true ) !== $blog_id ) {95						update_user_meta( $user_id, 'primary_blog', $blog_id );96					}97					if ( ! get_user_meta( $user_id, 'source_domain', true ) ) {98						update_user_meta( $user_id, 'source_domain', $details->domain );99					}100					break;101				}102			}103		} else {104			return null;105		}106 107		return $ret;108	} else {109		return $primary;110	}111}