<?php
/**
 * Keeps customer stats in step with orders.
 *
 * @package Rahkar\WP
 */

declare( strict_types = 1 );

namespace Rahkar\WP\Customers;

use WC_Order;

defined( 'ABSPATH' ) || exit;

/**
 * Notes which orders changed during a request and rebuilds their customers once,
 * in `shutdown`.
 *
 * WooCommerce saves an order several times in one checkout. Rebuilding on each
 * save would read the same customer's orders three or four times; noting the id
 * and doing the work once at the end costs one array write per save. The
 * connector's OrderWatcher does the same for the same reason.
 */
final class StatsWatcher {

	/**
	 * Order ids touched in this request.
	 *
	 * @var array<int, true>
	 */
	private static array $touched = [];

	/**
	 * Whether the shutdown flush is hooked already.
	 *
	 * @var bool
	 */
	private static bool $hooked = false;

	/**
	 * An order or refund was saved.
	 *
	 * @param mixed $order The saved object.
	 *
	 * @internal Hooked callback.
	 */
	public function saved( $order ): void {
		if ( $order instanceof \WC_Order_Refund ) {
			$this->touch( (int) $order->get_parent_id() );

			return;
		}

		if ( $order instanceof WC_Order ) {
			$this->touch( $order->get_id() );
		}
	}

	/**
	 * An order was trashed, deleted or restored; shutdown looks at what is left.
	 *
	 * @param mixed $orderId Order id.
	 *
	 * @internal Hooked callback.
	 */
	public function changed( $orderId ): void {
		$this->touch( (int) $orderId );
	}

	/**
	 * Record every touched order and rebuild the customers they belong to.
	 *
	 * @internal Hooked to `shutdown`.
	 */
	public function flush(): void {
		$ids           = array_keys( self::$touched );
		self::$touched = [];
		$customers     = [];

		foreach ( $ids as $id ) {
			$order = function_exists( 'wc_get_order' ) ? wc_get_order( $id ) : false;

			if ( $order instanceof WC_Order && 'trash' !== $order->get_status() ) {
				foreach ( Stats::record( $order ) as $hash ) {
					$customers[ $hash ] = true;
				}
			} else {
				$owner = Stats::forget( $id );

				if ( null !== $owner ) {
					$customers[ $owner ] = true;
				}
			}
		}

		foreach ( array_keys( $customers ) as $hash ) {
			Stats::rebuild( $hash );
		}
	}

	/**
	 * Note an order, and hook the flush the first time.
	 *
	 * @param int $orderId Order id.
	 */
	private function touch( int $orderId ): void {
		if ( $orderId < 1 ) {
			return;
		}

		self::$touched[ $orderId ] = true;

		if ( ! self::$hooked ) {
			self::$hooked = true;
			add_action( 'shutdown', fn() => $this->flush(), 5 );
		}
	}
}