Aggregate nodes based on conditon under new parent - xslt-2.0

Question

I have an given XML and I want to convert it in new xml and want to aggregate nodes based on status and orderId.
<?xml version="1.0" encoding="utf-8"?>
<OrderStatusUpdate>
<OrderStatusEvents>
<OrderStatusEvent>
<StoreCode>store1</StoreCode>
<OrderId>Order1</OrderId>
<ItemId>Item1</ItemId>
<OrderStatusDetails>
<OrderStatusDetail>
<OrderStatusEventTimeStamp>2017-03-19 03:37:05</OrderStatusEventTimeStamp>
<StatusName>Cancelled</StatusName>
</OrderStatusDetail>
</OrderStatusDetails>
</OrderStatusEvent>
<OrderStatusEvent>
<StoreCode>Store1</StoreCode>
<OrderId>Order1</OrderId>
<ItemId>Item2</ItemId>
<OrderStatusDetails>
<OrderStatusDetail>
<OrderStatusEventTimeStamp>2017-03-19 03:48:35</OrderStatusEventTimeStamp>
<StatusName>Cancelled</StatusName>
</OrderStatusDetail>
</OrderStatusDetails>
</OrderStatusEvent>
<OrderStatusEvent>
<StoreCode>Store1</StoreCode>
<OrderId>Order1</OrderId>
<ItemId>Item3</ItemId>
<OrderStatusDetails>
<OrderStatusDetail>
<OrderStatusEventTimeStamp>2017-03-19 03:48:35</OrderStatusEventTimeStamp>
<StatusName>Shipped</StatusName>
</OrderStatusDetail>
</OrderStatusDetails>
</OrderStatusEvent>
<OrderStatusEvent>
<StoreCode>Store1</StoreCode>
<OrderId>Order2</OrderId>
<ItemId>Item1</ItemId>
<OrderStatusDetails>
<OrderStatusDetail>
<OrderStatusEventTimeStamp>2017-03-19 03:48:35</OrderStatusEventTimeStamp>
<StatusName>Cancelled</StatusName>
</OrderStatusDetail>
</OrderStatusDetails>
</OrderStatusEvent>
</OrderStatusEvents>
</OrderStatusUpdate>
And I want an output like this. Here I am grouping elements based on status and orderId.
<Orders>
<group name="CANCELLED">
<STATUS ID="CANCELLED" DESCRIPTION="Goods Cancelled">
<ORDER ID="Order1">
<ORDER_ITEM item="item1" />
<ORDER_ITEM item="item2" />
</ORDER>
</STATUS>
<STATUS ID="CANCELLED" DESCRIPTION="Goods Cancelled">
<ORDER ID="Order2">
<ORDER_ITEM item="item1" />
</ORDER>
</STATUS>
</group>
<group name="SHIPPED">
<STATUS ID="SHIPPED" DESCRIPTION="Goods SHIPPED">
<ORDER ID="Order1">
<ORDER_ITEM item="item3" />
</ORDER>
</STATUS>
<group>
</Orders>
I am using the following xslt and it is working fine. Is there any way to improve this.
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes" />
<xsl:template match="OrderStatusUpdate/OrderStatusEvents">
<Orders>
<xsl:for-each-group select="OrderStatusEvent" group-by="OrderStatusDetails/OrderStatusDetail/StatusName">
<xsl:variable name="group-name" select="current-grouping-key()" />
<group name="{current-grouping-key()}">
<xsl:for-each-group select="current-group()" group-by="OrderId">
<xsl:variable name="order-id" select="current-grouping-key()" />
<xsl:element name="STATUS">
<xsl:attribute name="ID"><xsl:value-of select="$group-name" /></xsl:attribute>
<xsl:attribute name="DESCRIPTION">Goods <xsl:value-of select="$group-name" /></xsl:attribute>
<xsl:element name="ORDER">
<xsl:attribute name="ID"><xsl:value-of select="$order-id" /></xsl:attribute>
<xsl:for-each select="current-group()">
<xsl:if test="$group-name = 'Shipped'">
<xsl:call-template name="Shipped">
<xsl:with-param name="nodes">
<xsl:copy-of select="." />
</xsl:with-param>
</xsl:call-template>
</xsl:if>
<xsl:if test="$group-name = 'Cancelled'">
<xsl:call-template name="Cancelled">
<xsl:with-param name="nodes">
<xsl:copy-of select="." />
</xsl:with-param>
</xsl:call-template>
</xsl:if>
</xsl:for-each>
</xsl:element>
</xsl:element>
</xsl:for-each-group>
</group>
</xsl:for-each-group>
</Orders>
</xsl:template>
<xsl:template name="Shipped">
<xsl:param name="nodes">
</xsl:param>
<xsl:element name="ORDER_ITEM">
<xsl:attribute name="ID"><xsl:value-of select="$nodes/OrderStatusEvent/ItemId" /></xsl:attribute>
</xsl:element>
</xsl:template>
<xsl:template name="Cancelled">
<xsl:param name="nodes"></xsl:param>
<xsl:element name="ORDER_ITEM">
<xsl:attribute name="ID"><xsl:value-of select="$nodes/OrderStatusEvent/ItemId" /></xsl:attribute>
</xsl:element>
</xsl:template>
</xsl:stylesheet>

Answer 1

It is easier to use literal result elements and attribute value templates as long as you don't need to compute element or attribute names at run-time and I don't think you need the two templates and call-template, it suffices to use
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="xs"
version="2.0">
<xsl:output omit-xml-declaration="yes" indent="yes" />
<xsl:template match="OrderStatusUpdate/OrderStatusEvents">
<Orders>
<xsl:for-each-group select="OrderStatusEvent" group-by="OrderStatusDetails/OrderStatusDetail/StatusName">
<xsl:variable name="group-name" select="current-grouping-key()" />
<group name="{current-grouping-key()}">
<xsl:for-each-group select="current-group()" group-by="OrderId">
<xsl:variable name="order-id" select="current-grouping-key()" />
<STATUS ID="{$group-name}" DESCRIPTION="Goods {$group-name}">
<ORDER ID="{$order-id}">
<xsl:apply-templates select="current-group()"/>
</ORDER>
</STATUS>
</xsl:for-each-group>
</group>
</xsl:for-each-group>
</Orders>
</xsl:template>
<xsl:template match="OrderStatusEvent">
<ORDER_ITEM ID="{ItemId}"/>
</xsl:template>
</xsl:stylesheet>