<?php
/**
 * Request signing contract.
 *
 * @package AdPix\Analytics
 */

declare( strict_types = 1 );

namespace AdPix\Analytics\Contracts;

defined( 'ABSPATH' ) || exit;

/**
 * Adds authentication headers that depend on the exact bytes being sent.
 *
 * Separate from the HTTP client because signing is a policy — a property may or may not require
 * HMAC — and the client should not grow a branch for every policy that is ever added.
 */
interface SignerInterface {

	/**
	 * Return the headers with any signature applied.
	 *
	 * @param array<string,string> $headers Headers assembled so far.
	 * @param string               $body    The exact request body the signature must cover.
	 * @return array<string,string>
	 */
	public function sign( array $headers, string $body ): array;
}