t = $this->options->get( 'critical_css', '' );
		} else {
			$critical_css_content = rocket_direct_filesystem()->get_contents( $current_page_cpcss );
		}

		if ( ! $critical_css_content ) {
			return $buffer;
		}

		$critical_css_content = str_replace( '\\', '\\\\', $critical_css_content );

		$buffer = preg_replace( '#</title>#iU', '</title><style id="rocket-critical-css">' . wp_strip_all_tags( $critical_css_content ) . '</style>', $buffer, 1 );

		return $buffer;
	}

	/**
	 * Defer loading of CSS files
	 *
	 * @since 2.10
	 * @author Remy Perona
	 *
	 * @param string $buffer HTML code.
	 * @return string Updated HTML code
	 */
	public function async_css( $buffer ) {
		if ( ( defined( 'DONOTROCKETOPTIMIZE' ) && DONOTROCKETOPTIMIZE ) || ( defined( 'DONOTASYNCCSS' ) && DONOTASYNCCSS ) ) {
			return;
		}

		if ( ! $this->options->get( 'async_css' ) ) {
			return $buffer;
		}

		if ( is_rocket_post_excluded_option( 'async_css' ) ) {
			return $buffer;
		}

		if ( ! $this->critical_css->get_current_page_critical_css() ) {
			return $buffer;
		}

		$excluded_css = array_flip( get_rocket_exclude_async_css() );

		/**
		 * Filters the pattern used to get all stylesheets in the HTML
		 *
		 * @since 2.10
		 * @author Remy Perona
		 *
		 * @param string $css_pattern Regex pattern to get all stylesheets in the HTML.
		 */
		$css_pattern = apply_filters( 'rocket_async_css_regex_pattern', '/(?=<link[^>]*\s(rel\s*=\s*[\'"]stylesheet["\']))<link[^>]*\shref\s*=\s*[\'"]([^\'"]+)[\'"](.*)>/iU' );

		// Get all css files with this regex.
		preg_match_all( $css_pattern, $buffer, $tags_match );

		if ( ! isset( $tags_match[0] ) ) {
			return $buffer;
		}

		$noscripts = '';

		foreach ( $tags_match[0] as $i => $tag ) {
			// Strip query args.
			$path = rocket_extract_url_component( $tags_match[2][ $i ], PHP_URL_PATH );

			// Check if this file should be deferred.
			if ( isset( $excluded_css[ $path ] ) ) {
				continue;
			}

			$preload = str_replace( 'stylesheet', 'preload', $tags_match[1][ $i ] );
			$onload  = preg_replace( '~' . preg_quote( $tags_match[3][ $i ], '~' ) . '~iU', ' as="style" onload=""' . $tags_match[3][ $i ] . '>', $tags_match[3][ $i ] );
			$tag     = str_replace( $tags_match[3][ $i ] . '>', $onload, $tag );
			$tag     = str_replace( $tags_match[1][ $i ], $preload, $tag );
			$tag     = str_replace( 'onload=""', 'onload="this.onload=null;this.rel=\'stylesheet\'"', $tag );
			$buffer  = str_replace( $tags_match[0][ $i ], $tag, $buffer );

			$noscripts .= '<noscript>' . $tags_match[0][ $i ] . '</noscript>';
		}

		$buffer = str_replace( '</body>', $noscripts . '</body>', $buffer );

		return $buffer;
	}

	/**
	 * Regenerates the CPCSS when switching theme if the potion is active
	 *
	 * @since 3.3
	 * @author Remy Perona
	 * @return void
	 */
	public function maybe_regenerate_cpcss() {
		if ( ! $this->options->get( 'async_css' ) ) {
			return;
		}

		$this->critical_css->process_handler();
	}

	/**
	 * Cleans the cache when the generation is complete
	 *
	 * @since 3.3
	 * @author Remy Perona
	 * @return void
	 */
	public function clean_domain_on_complete() {
		\rocket_clean_domain();
	}
}