protected function set_fee( $order, $fee, $action ) {

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

			// fee title is required
			if ( ! isset( $fee['title'] ) ) {
				throw new WC_API_Exception( 'woocommerce_invalid_fee_item', __( 'Fee title is required', 'woocommerce' ), 400 );
			}

			$item = new WC_Order_Item_Fee();
			$item->set_order_id( $order->get_id() );
			$item->set_name( wc_clean( $fee['title'] ) );
			$item->set_total( isset( $fee['total'] ) ? floatval( $fee['total'] ) : 0 );

			// if taxable, tax class and total are required
			if ( ! empty( $fee['taxable'] ) ) {
				if ( ! isset( $fee['tax_class'] ) ) {
					throw new WC_API_Exception( 'woocommerce_invalid_fee_item', __( 'Fee tax class is required when fee is taxable.', 'woocommerce' ), 400 );
				}

				$item->set_tax_status( 'taxable' );
				$item->set_tax_class( $fee['tax_class'] );

				if ( isset( $fee['total_tax'] ) ) {
					$item->set_total_tax( isset( $fee['total_tax'] ) ? wc_format_refund_total( $fee['total_tax'] ) : 0 );
				}

				if ( isset( $fee['tax_data'] ) ) {
					$item->set_total_tax( wc_format_refund_total( array_sum( $fee['tax_data'] ) ) );
					$item->set_taxes( array_map( 'wc_format_refund_total', $fee['tax_data'] ) );
				}
			}

			$order->add_item( $item );
		} else {

			$item = new WC_Order_Item_Fee( $fee['id'] );

			if ( isset( $fee['title'] ) ) {
				$item->set_name( wc_clean( $fee['title'] ) );
			}

			if ( isset( $fee['tax_class'] ) ) {
				$item->set_tax_class( $fee['tax_class'] );
			}

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

			if ( isset( $fee['total_tax'] ) ) {
				$item->set_total_tax( floatval( $fee['total_tax'] ) );
			}

			$fee_id = $item->save();

			if ( ! $fee_id ) {
				throw new WC_API_Exception( 'woocommerce_cannot_update_fee', __( 'Cannot update fee, try again.', 'woocommerce' ), 500 );
			}
		}
	}