How to match the case and apply templates - xpath

Question

I've the below XML line of code.
<title><page>651</page>CHAPTER 13 This is <content-style font-style="italic">This goes in content-style</content-style> The title</title>
Here i'm trying to do the below.
Get the number after CHAPTER and concat it with Chapter, i'm able to do it with the below code.
<xsl:value-of select="concat('Chapter ', substring-before(substring-after(child::title,' '),' ')"/>
ignore the page in the title, and i use the below template match and able to do it.
<xsl:template match="title/page"/>
If there is just plain data, i'm using the below to get it.
<xsl:value of select ="substring-after(substring-after(./title,' '),' ')">
But the problem came in the above type, here i need to apply templates on substring-after(substring-after(.,' '),' ') and unfortunately this is not working.
I have the below XSLT
<xsl:template match ="title">
<xsl:apply-templates/>
</xsl:template>
<xsl:template match="content-style">
<xsl:variable name="fontStyle">
<xsl:value-of select="concat('font-style-',#font-style)"/>
</xsl:variable>
<span class="{$fontStyle}">
<xsl:value-of select="."/>
<xsl:apply-templates select="para"/>
</span>
</xsl:template>
expected O/P
<div class="chapter-title">
<span class="chapter-num">Chapter 13</span><br /><br /> This is <span class="font-style-italic">This goes in content-style</span> the title</span></div>
Can you please let me know how can i do this.
Thanks

Answer 1

Your expected output has an unmatched span end tag.
Ignoring that, I would do something like:
<xsl:template match ="title">
<xsl:apply-templates/>
</xsl:template>
<xsl:template match="content-style">
<span class="font-style-{#font-style}">
<xsl:value-of select="."/>
</span>
</xsl:template>
<xsl:template match="title/text()">
<xsl:analyze-string select="." regex="Chapter [0-9]+">
<xsl:matching-substring>
<span class="chapter-num">
<xsl:value-of select="."/>
</span><br/>>br/>
</xsl:matching-substring>
<xsl:non-matching-substring>
<xsl:value-of select="."/>
</xsl:-nonmatching-substring>
</xsl:analyze-string>
</xsl:template>