<?php
// phpcs:disable WordPress.NamingConventions.PrefixAllGlobals.NonPrefixedHooknameFound -- Compatibility layer must hook third-party action/filter names unchanged.
namespace QWSpeedCache\Compatibility;

defined( 'ABSPATH' ) || exit;

/**
 * WPML / Polylang language segment for page-cache keys (N-16).
 */
class Multilingual {

	public function __construct() {
		if ( function_exists( 'add_filter' ) ) {
			add_filter( 'qwsc_cache_key_suffix', array( $this, 'suffix' ) );
		}
	}

	/**
	 * Current language code for cache key.
	 *
	 * @return string
	 */
	public static function language_code() {
		// Polylang.
		if ( function_exists( 'pll_current_language' ) ) {
			$c = pll_current_language( 'slug' );
			if ( is_string( $c ) && '' !== $c ) {
				return strtolower( $c );
			}
		}
		// WPML.
		if ( defined( 'ICL_LANGUAGE_CODE' ) && ICL_LANGUAGE_CODE ) {
			return strtolower( (string) ICL_LANGUAGE_CODE );
		}
		if ( function_exists( 'has_filter' ) && has_filter( 'wpml_current_language' ) && function_exists( 'apply_filters' ) ) {
			$c = apply_filters( 'wpml_current_language', null );
			if ( is_string( $c ) && '' !== $c ) {
				return strtolower( $c );
			}
		}
		// Locale fallback (blog language).
		if ( function_exists( 'determine_locale' ) ) {
			$loc = determine_locale();
			if ( is_string( $loc ) && strlen( $loc ) >= 2 ) {
				return strtolower( substr( $loc, 0, 2 ) );
			}
		}
		return '';
	}

	/**
	 * @param string $suffix Existing suffix.
	 * @return string
	 */
	public function suffix( $suffix ) {
		$code = self::language_code();
		if ( '' === $code ) {
			return $suffix;
		}
		return (string) $suffix . '|lang:' . $code;
	}
}