'quantity' => abs( $change['from'] - $change['to'] ),
				)
			);
		}
	}

	$order->add_order_note( __( 'Stock levels reduced:', 'woocommerce' ) . ' ' . implode( ', ', $order_notes ) );
}

/**
 * Increase stock levels for items within an order.
 *
 * @since 3.0.0
 * @param int|WC_Order $order_id Order ID or order instance.
 */
function wc_increase_stock_levels( $order_id ) {
	if ( is_a( $order_id, 'WC_Order' ) ) {
		$order    = $order_id;
		$order_id = $order->get_id();
	} else {
		$order = wc_get_order( $order_id );
	}

	// We need an order, and a store with stock management to continue.
	if ( ! $order || 'yes' !== get_option( 'woocommerce_manage_stock' ) || ! apply_filters( 'woocommerce_can_restore_order_stock', true, $order ) ) {
		return;
	}

	$changes = array();

	// Loop over all items.
	foreach ( $order->get_items() as $item ) {
		if ( ! $item->is_type( 'line_item' ) ) {
			continue;
		}

		// Only increase stock once for each item.
		$product            = $item->get_product();
		$item_stock_reduced = $item->get_meta( '_reduced_stock', true );

		if ( ! $item_stock_reduced || ! $product || ! $product->managing_stock() ) {
			continue;
		}

		$item_name = $product->get_formatted_name();
		$new_stock = wc_update_product_stock( $product, $item_stock_reduced, 'increase' );

		if ( is_wp_error( $new_stock ) ) {
			/* translators: %s item name. */
			$order->add_order_note( sprintf( __( 'Unable to restore stock for item %s.', 'woocommerce' ), $item_name ) );
			continue;
		}

		$item->delete_meta_data( '_reduced_stock' );
		$item->save();

		$changes[] = $item_name . ' ' . ( $new_stock - $item_stock_reduced ) . '→' . $new_stock;
	}

	if ( $changes ) {
		$order->add_order_note( __( 'Stock levels increased:', 'woocommerce' ) . ' ' . implode( ', ', $changes ) );
	}

	do_action( 'woocommerce_restore_order_stock', $order );
}

/**
 * See how much stock is being held in pending orders.
 *
 * @since 3.5.0
 * @param WC_Product $product Product to check.
 * @param integer    $exclude_order_id Order ID to exclude.
 * @return int
 */
function wc_get_held_stock_quantity( WC_Product $product, $exclude_order_id = 0 ) {
	/**
	 * Filter: woocommerce_hold_stock_for_checkout
	 * Allows enable/disable hold stock functionality on checkout.
	 *
	 * @since 4.3.0
	 * @param bool $enabled Default to true if managing stock globally.
	 */
	if ( ! apply_filters( 'woocommerce_hold_stock_for_checkout', wc_string_to_bool( get_option( 'woocommerce_manage_stock', 'yes' ) ) ) ) {
		return 0;
	}

	return ( new \Automattic\WooCommerce\Checkout\Helpers\ReserveStock() )->get_reserved_stock( $product, $exclude_order_id );
}

/**
 * Hold stock for an order.
 *
 * @throws ReserveStockException If reserve stock fails.
 *
 * @since 4.1.0
 * @param \WC_Order|int $order Order ID or instance.
 */
function wc_reserve_stock_for_order( $order ) {
	/**
	 * Filter: woocommerce_hold_stock_for_checkout
	 * Allows enable/disable hold stock functionality on checkout.
	 *
	 * @since @since 4.1.0
	 * @param bool $enabled Default to true if managing stock globally.
	 */
	if ( ! apply_filters( 'woocommerce_hold_stock_for_checkout', wc_string_to_bool( get_option( 'woocommerce_manage_stock', 'yes' ) ) ) ) {
		return;
	}

	$order = $order instanceof WC_Order ? $order : wc_get_order( $order );

	if ( $order ) {
		( new \Automattic\WooCommerce\Checkout\Helpers\ReserveStock() )->reserve_stock_for_order( $order );
	}
}
add_action( 'woocommerce_checkout_order_created', 'wc_reserve_stock_for_order' );

/**
 * Release held stock for an order.
 *
 * @since 4.3.0
 * @param \WC_Order|int $order Order ID or instance.
 */
function wc_release_stock_for_order( $order ) {
	/**
	 * Filter: woocommerce_hold_stock_for_checkout
	 * Allows enable/disable hold stock functionality on checkout.
	 *
	 * @since 4.3.0
	 * @param bool $enabled Default to true if managing stock globally.
	 */
	if ( ! apply_filters( 'woocommerce_hold_stock_for_checkout', wc_string_to_bool( get_option( 'woocommerce_manage_stock', 'yes' ) ) ) ) {
		return;
	}

	$order = $order instanceof WC_Order ? $order : wc_get_order( $order );

	if ( $order ) {
		( new \Automattic\WooCommerce\Checkout\Helpers\ReserveStock() )->release_stock_for_order( $order );
	}
}
add_action( 'woocommerce_checkout_order_exception', 'wc_release_stock_for_order' );
add_action( 'woocommerce_payment_complete', 'wc_release_stock_for_order', 11 );
add_action( 'woocommerce_order_status_cancelled', 'wc_release_stock_for_order', 11 );
add_action( 'woocommerce_order_status_completed', 'wc_release_stock_for_order', 11 );
add_action( 'woocommerce_order_status_processing', 'wc_release_stock_for_order', 11 );
add_action( 'woocommerce_order_status_on-hold', 'wc_release_stock_for_order', 11 );

/**
 * Return low stock amount to determine if notification needs to be sent
 *
 * Since 5.2.0, this function no longer redirects from variation to its parent product.
 * Low stock amount can now be attached to the variation itself and if it isn't, only
 * then we check the parent product, and if it's not there, then we take the default
 * from the store-wide setting.
 *
 * @param  WC_Product $product Product to get data from.
 * @since  3.5.0
 * @return int
 */
function wc_get_low_stock_amount( WC_Product $product ) {
	$low_stock_amount = $product->get_low_stock_amount();

	if ( '' === $low_stock_amount && $product->is_type( 'variation' ) ) {
		$product          = wc_get_product( $product->get_parent_id() );
		$low_stock_amount = $product->get_low_stock_amount();
	}

	if ( '' === $low_stock_amount ) {
		$low_stock_amount = get_option( 'woocommerce_notify_low_stock_amount', 2 );
	}

	return (int) $low_stock_amount;
}