<?php
namespace QWSpeedCache\Compatibility;

defined( 'ABSPATH' ) || exit;

/**
 * Append custom robots.txt rules.
 */
class RobotsTxt {

	public function __construct() {
		add_filter( 'robots_txt', array( $this, 'append' ), 20, 2 );
	}

	/**
	 * @param string $output Output.
	 * @param bool   $public Blog public.
	 * @return string
	 */
	public function append( $output, $public ) {
		$s = \QWSpeedCache\Plugin::instance()->get_all_settings();
		$extra = isset( $s['robots_txt_extra'] ) && is_string( $s['robots_txt_extra'] ) ? trim( $s['robots_txt_extra'] ) : '';
		if ( '' === $extra ) {
			return $output;
		}
		// Keep custom rules bounded and strip null bytes/control characters.
		$extra = substr( preg_replace( '/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]/', '', $extra ), 0, 16384 );
		return rtrim( $output ) . "\n\n# QW Optimize\n" . $extra . "\n";
	}
}