protected function set_shipping( $order, $shipping, $action ) {

		// total must be a positive float
		if ( isset( $shipping['total'] ) && floatval( $shipping['total'] ) < 0 ) {
			throw new WC_API_Exception( 'woocommerce_invalid_shipping_total', __( 'Shipping total must be a positive amount.', 'woocommerce' ), 400 );
		}

		if ( 'create' === $action ) {

			// method ID is required
			if ( ! isset( $shipping['method_id'] ) ) {
				throw new WC_API_Exception( 'woocommerce_invalid_shipping_item', __( 'Shipping method ID is required.', 'woocommerce' ), 400 );
			}

			$rate = new WC_Shipping_Rate( $shipping['method_id'], isset( $shipping['method_title'] ) ? $shipping['method_title'] : '', isset( $shipping['total'] ) ? floatval( $shipping['total'] ) : 0, array(), $shipping['method_id'] );
			$item = new WC_Order_Item_Shipping();
			$item->set_order_id( $order->get_id() );
			$item->set_shipping_rate( $rate );
			$order->add_item( $item );
		} else {

			$item = new WC_Order_Item_Shipping( $shipping['id'] );

			if ( isset( $shipping['method_id'] ) ) {
				$item->set_method_id( $shipping['method_id'] );
			}

			if ( isset( $shipping['method_title'] ) ) {
				$item->set_method_title( $shipping['method_title'] );
			}

			if ( isset( $shipping['total'] ) ) {
				$item->set_total( floatval( $shipping['total'] ) );
			}

			$shipping_id = $item->save();

			if ( ! $shipping_id ) {
				throw new WC_API_Exception( 'woocommerce_cannot_update_shipping', __( 'Cannot update shipping method, try again.', 'woocommerce' ), 500 );
			}
		}
	}