<?php
/**
 * Privacy-safe identifier hashing.
 *
 * @package ZeroSpamForms
 */

namespace TwoOTwoCode\ZeroSpamForms\Privacy;

defined( 'ABSPATH' ) || exit;

/**
 * Hashes identifiers before storage or counters.
 */
final class IdentifierHasher {
	/**
	 * Secret provider.
	 *
	 * @var SecretProviderInterface
	 */
	private $secret_provider;

	/**
	 * Constructor.
	 *
	 * @param SecretProviderInterface $secret_provider Secret provider.
	 */
	public function __construct( SecretProviderInterface $secret_provider ) {
		$this->secret_provider = $secret_provider;
	}

	/**
	 * Hash an identifier with a purpose namespace.
	 *
	 * @param string $purpose    Purpose namespace.
	 * @param string $identifier Raw identifier.
	 */
	public function hash_identifier( string $purpose, string $identifier ): string {
		$purpose = strtolower( preg_replace( '/[^a-z0-9_:-]/', '', $purpose ) ?? 'generic' );

		return hash_hmac( 'sha256', $purpose . '|' . trim( $identifier ), $this->secret_provider->get_secret() );
	}
}