create_shipping( $order, $parent_order ) {
        dokan_log( sprintf( '#%d - Creating Shipping.', $order->get_id() ) );

        // Get all shipping methods for parent order
        $shipping_methods = $parent_order->get_shipping_methods();
        $order_seller_id  = dokan_get_seller_id_by_order( $order->get_id() );

        $applied_shipping_method = '';

        if ( $shipping_methods ) {
            foreach ( $shipping_methods as $method_item_id => $shipping_object ) {
                $shipping_seller_id = wc_get_order_item_meta( $method_item_id, 'seller_id', true );

                if ( $order_seller_id == $shipping_seller_id ) {
                    $applied_shipping_method = $shipping_object;
                    break;
                }
            }
        }

        $shipping_method = apply_filters( 'dokan_shipping_method', $applied_shipping_method, $order->get_id(), $parent_order );

        // bail out if no shipping methods found
        if ( ! $shipping_method ) {
            dokan_log( sprintf( '#%d - No shipping method found. Aborting.', $order->get_id() ) );

            return;
        }

        if ( is_a( $shipping_method, 'WC_Order_Item_Shipping' ) ) {
            $item = new \WC_Order_Item_Shipping();

            dokan_log( sprintf( '#%d - Adding shipping item.', $order->get_id() ) );

            $item->set_props(
                array(
                    'method_title' => $shipping_method->get_name(),
                    'method_id'    => $shipping_method->get_method_id(),
                    'total'        => $shipping_method->get_total(),
                    'taxes'        => $shipping_method->get_taxes(),
                )
            );

            $metadata = $shipping_method->get_meta_data();

            if ( $metadata ) {
                foreach ( $metadata as $meta ) {
                    $item->add_meta_data( $meta->key, $meta->value );
                }
            }

            $order->add_item( $item );
            $order->set_shipping_total( $shipping_method->get_total() );
            $order->save();
        }
    }

    /**
     * Create coupons for a sub-order if neccessary
     *
     * @param \WC_Order $order
     * @param \WC_Order $parent_order
     * @param array $products
     *
     * @return void
     */
    public function create_coupons( $order, $parent_order, $products ) {
        $used_coupons = $parent_order->get_items( 'coupon' );
        $product_ids  = array_map(
            function ( $item ) {
                return $item->get_product_id();
            }, $products
        );

        if ( ! $used_coupons ) {
            return;
        }

        $seller_id = dokan_get_seller_id_by_order( $order->get_id() );

        if ( ! $seller_id ) {
            return;
        }

        foreach ( $used_coupons as $item ) {
            $coupon = new \WC_Coupon( $item->get_code() );

            if (
                $coupon &&
                ! is_wp_error( $coupon ) &&
                ( array_intersect( $product_ids, $coupon->get_product_ids() ) ||
                  apply_filters( 'dokan_is_order_have_admin_coupon', false, $coupon, [ $seller_id ], $product_ids )
                )
            ) {
                $new_item = new \WC_Order_Item_Coupon();
                $new_item->set_props(
                    array(
                        'code'         => $item->get_code(),
                        'discount'     => $item->get_discount(),
                        'discount_tax' => $item->get_discount_tax(),
                    )
                );

                $new_item->add_meta_data( 'coupon_data', $coupon->get_data() );

                $order->add_item( $new_item );
            }
        }

        $order->save();
    }

    /**
     * Monitors a new order and attempts to create sub-orders
     *
     * If an order contains products from multiple vendor, we can't show the order
     * to each seller dashboard. That's why we need to divide the main order to
     * some sub-orders based on the number of sellers.
     *
     * @param int $parent_order_id
     *
     * @return void
     */
    public function maybe_split_orders( $parent_order_id ) {
        $parent_order = dokan()->order->get( $parent_order_id );

        dokan_log( sprintf( 'New Order #%d created. Init sub order.', $parent_order_id ) );

        if ( $parent_order->get_meta( 'has_sub_order' ) == true ) {
            $args = array(
                'post_parent' => $parent_order_id,
                'post_type'   => 'shop_order',
                'numberposts' => - 1,
                'post_status' => 'any',
            );

            $child_orders = get_children( $args );

            foreach ( $child_orders as $child ) {
                wp_delete_post( $child->ID, true );
            }
        }

        $vendors = dokan_get_sellers_by( $parent_order_id );

        // return if we've only ONE seller
        if ( count( $vendors ) == 1 ) {
            dokan_log( '1 vendor only, skipping sub order.' );

            $temp      = array_keys( $vendors );
            $seller_id = reset( $temp );

            do_action( 'dokan_create_parent_order', $parent_order, $seller_id );

            $parent_order->update_meta_data( '_dokan_vendor_id', $seller_id );
            $parent_order->save();

            // if the request is made from rest api then insert the order data to the sync table
            if ( defined( 'REST_REQUEST' ) ) {
                do_action( 'dokan_checkout_update_order_meta', $parent_order_id, $seller_id );
            }

            return;
        }

        // flag it as it has a suborder
        $parent_order->update_meta_data( 'has_sub_order', true );
        $parent_order->save();

        dokan_log( sprintf( 'Got %s vendors, starting sub order.', count( $vendors ) ) );

        // seems like we've got multiple sellers
        foreach ( $vendors as $seller_id => $seller_products ) {
            dokan()->order->create_sub_order( $parent_order, $seller_id, $seller_products );
        }

        dokan_log( sprintf( 'Completed sub order for #%d.', $parent_order_id ) );
    }

    /**
     * This will check if given var is empty or not.
     *
     * @since 3.6.3
     *
     * @param mixed $var
     *
     * @return bool
     */
    protected function is_empty( $var ) {
        if ( empty( $var ) ) {
            return true;
        }

        // if var is an array, check if it's empty or not
        if ( is_array( $var ) && isset( $var[0] ) && intval( $var[0] ) === 0 ) {
            return true;
        }

        return false;
    }
}