<?php
namespace Actirise\Includes\Push;

if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly
}

/**
 * Deduplicates push notifications by their event id.
 *
 * The Actirise API reuses the same `event_id` across delivery retries. To avoid
 * applying the same change twice, a processed event is recorded in a transient
 * keyed by its id. The record is written only *after* a successful apply, so a
 * notification that failed to apply is never marked processed and can be
 * retried. A duplicate is answered with `200 {success:true}` and no re-apply.
 *
 * @link       https://actirise.com
 * @since      4.3.0
 * @package    actirise
 * @subpackage actirise/includes/push
 * @author     actirise <wordpress@actirise.com>
 */
final class Idempotency {
	/**
	 * Transient-key prefix for the per-event processed marker.
	 *
	 * @since 4.3.0
	 * @var   string
	 */
	const TRANSIENT_PREFIX = 'actirise_push_';

	/**
	 * Lifetime of a processed marker, in seconds (~1 day). Retries land well
	 * inside this window; the marker expires afterwards so the transient store
	 * does not grow without bound.
	 *
	 * @since 4.3.0
	 * @var   int
	 */
	const TTL_SECONDS = 86400;

	/**
	 * Whether a notification with this event id has already been applied.
	 *
	 * @since 4.3.0
	 * @param string $event_id The notification event id.
	 * @return bool
	 */
	public function is_processed( $event_id ) {
		return false !== get_transient( self::key( $event_id ) );
	}

	/**
	 * Record that a notification with this event id has been applied.
	 *
	 * Called only after a successful apply so a failed apply is never marked and
	 * remains eligible for retry.
	 *
	 * @since 4.3.0
	 * @param string $event_id The notification event id.
	 * @return void
	 */
	public function mark_processed( $event_id ) {
		set_transient( self::key( $event_id ), 1, self::TTL_SECONDS );
	}

	/**
	 * Build the transient key for an event id.
	 *
	 * @since 4.3.0
	 * @param string $event_id The notification event id.
	 * @return string
	 */
	private static function key( $event_id ) {
		return self::TRANSIENT_PREFIX . $event_id;
	}
}