SanitizeCombinedHeadersPropagationGetter.php

<?php

declare (strict_types=1);
namespace OpenTelemetry\Context\Propagation;

use function preg_replace;

/**
 * Some servers concatenate multiple headers with ';' -- we need to replace these with ','
 * This is still a workaround and doesn't get around the problem fully, specifically it doesn't
 * handle edge cases where the header has a trailing ';' or an empty trace state.
 * We also need to trim trailing separators from the header, found when a header is empty.
 */
final class SanitizeCombinedHeadersPropagationGetter implements PropagationGetterInterface {
    private const LIST_MEMBERS_SEPARATOR = ',';
    private const SERVER_CONCAT_HEADERS_REGEX = '/;(?=[^,=;]*=|$)/';
    private const TRAILING_LEADING_SEPARATOR_REGEX = '/^' . self::LIST_MEMBERS_SEPARATOR . '+|' . self::LIST_MEMBERS_SEPARATOR . '+$/';
    public function __construct(PropagationGetterInterface $getter) {
    }
    public function keys($carrier) : array {
        return $this->getter
            ->keys($carrier);
    }
    public function get($carrier, string $key) : ?string {
        $value = $this->getter
            ->get($carrier, $key);
        if ($value === null) {
            return null;
        }
        return preg_replace([
            self::SERVER_CONCAT_HEADERS_REGEX,
            self::TRAILING_LEADING_SEPARATOR_REGEX,
        ], [
            self::LIST_MEMBERS_SEPARATOR,
        ], $value);
    }

}