<?php
namespace Admirly\Domain;

/**
 * Language helpers for multilingual sites (pure PHP).
 */
final class Lang {
	/** "tr_TR" → "tr", "en-US" → "en"; '' when not a language code. */
	public static function normalize( string $locale ): string {
		$l     = strtolower( trim( $locale ) );
		$parts = preg_split( '/[_-]/', $l ) ?: [];
		$l     = $parts[0] ?? '';
		return preg_match( '/^[a-z]{2,3}$/', $l ) ? $l : '';
	}

	/**
	 * Filters review items by language. Items without a language are always shown; when the current
	 * language is unknown nothing is filtered.
	 *
	 * @param array<int,array<string,mixed>> $items
	 * @param string                         $mode 'all' | 'current'
	 * @return array<int,array<string,mixed>>
	 */
	public static function filter( array $items, string $mode, string $current ): array {
		$cur = self::normalize( $current );
		if ( $mode !== 'current' || $cur === '' ) {
			return $items;
		}
		return array_values(
			array_filter(
				$items,
				static function ( $it ) use ( $cur ) {
					$l = self::normalize( (string) ( $it['lang'] ?? '' ) );
					return $l === '' || $l === $cur;
				}
			)
		);
	}
}