MultiTextMapPropagator.php

<?php

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

use function array_map;
use function array_merge;
use function array_unique;
use function array_values;
use OpenTelemetry\Context\Context;
use OpenTelemetry\Context\ContextInterface;
final class MultiTextMapPropagator implements TextMapPropagatorInterface {
    
    /** @var list<string> */
    private readonly array $fields;
    
    /**
     * @no-named-arguments
     *
     * @param list<TextMapPropagatorInterface> $propagators
     */
    public function __construct(array $propagators) {
        $this->fields = $this->extractFields($this->propagators);
    }
    public function fields() : array {
        return $this->fields;
    }
    public function inject(&$carrier, ?PropagationSetterInterface $setter = null, ?ContextInterface $context = null) : void {
        foreach ($this->propagators as $propagator) {
            $propagator->inject($carrier, $setter, $context);
        }
    }
    public function extract($carrier, ?PropagationGetterInterface $getter = null, ?ContextInterface $context = null) : ContextInterface {
        $context ??= Context::getCurrent();
        foreach ($this->propagators as $propagator) {
            $context = $propagator->extract($carrier, $getter, $context);
        }
        return $context;
    }
    
    /**
     * @param list<TextMapPropagatorInterface> $propagators
     * @return list<string>
     */
    private function extractFields(array $propagators) : array {
        return array_values(array_unique(array_merge(...array_map(static fn(TextMapPropagatorInterface $propagator) => $propagator->fields(), $propagators))));
    }

}