Recursively replacing elements in XSLT - xslt

Question

I need to replace the <tref> element with other tags from elsewhere in my document. For example, I have:
<tref id="57236"/>
and
<Topic>
<ID>57236</ID>
<Text>
<p id="4">
<cs id="56792">1090-189-01 </cs>
<href id="57237">
<cs id="56792">Document Name</cs>
</href>
</p>
</Text>
</Topic>
Obtaining the following is not a problem:
<p id="4">
<cs id="56792">1090-189-01 </cs>
<href id="57237">
<cs id="56792">Document Name</cs>
</href>
</p>
With this stylesheet:
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
<xsl:template match="tref">
<xsl:variable name="NodeID"><xsl:value-of select="#id"/></xsl:variable>
<xsl:copy-of select="//Topic[ID = $NodeID]/Text/p/node()"/>
</xsl:template>
What I cannot do is replacing trefs nested into other trefs. For example, consider the following:
<tref id="57236"/>
and:
<Topic>
<ID>57236</ID>
<Text>
<p id="251">
<tref id="37287"/>
</p>
</Text>
</Topic>
My stylesheet duly replaces the tref with the content of the tag - which also contains a tref:
<p id="251">
<tref id="37287"/>
</p>
My current solution is to call <xsl:template match="tref"> from two different stylesheets. It does the job, but it is not very elegant, and what if trefs are nested at an even deeper level? And recursion is the bread and butter of XSLT.
Is there a solution to recursively replace all trefs as in XSLT?

Answer 1

Instead of using xsl:copy-of, use xsl:apply-templates
<xsl:apply-templates select="//Topic[ID = $NodeID]/Text/p/node()"/>
Or, to eliminate the use of the varianle
<xsl:apply-templates select="//Topic[ID = current()/#id]/Text/p/node()"/>
Note you can make use of an xsl:key to look-up the Topic elements
<xsl:key name="topic" match="Topic" use="ID" />
Then you can write this
<xsl:apply-templates select="key('topic', #id)/Text/p/node()"/>
Be wary of infinite recursion if you have a tref referring to a Topic that is an ancestor of it.