Insert image on first occurence - xslt

Question

I have a xml document which looks something like this:
<chapter>
<para>Just a random text<cross-ref refid="1234">Abb. 1.0</cross-ref>Some more text</para>
<section-title>Title</section-title>
<para>and more text text ext<cross-ref refif="1234">Abb 1.0</cross-ref>more more more</para>
</chapter>
As you can see there are two cross-ref elements inside paragraphs. They can occur basically everywhere and are somewhat identified by their refid(but not uniquely). What i am currently trying to do is inserting an image (based on the refid) at the position of the first occurence while keeping the text as a caption. Every other occurence (which are not the first) should just be inline texts containing an internal basic-link to that inserted image.
My current solution is:
<xsl:template match="cross-ref">
<xsl:choose>
<xsl:when test="position() = 1">
<fo:block text-align="center" id="{#refid}">
<xsl:variable name="refVar" select="#refid"/>
<xsl:variable name="imageName" select="/chapter/floats/figure[#id=$refVar]/link/#locator" />
<fo:external-graphic src="url({concat($imageName, '.jpg')})" />
<fo:block text-align="center" xsl:use-attribute-sets="lit-para">
<xsl:value-of select="current()" />
</fo:block>
</fo:block>
</xsl:when>
<xsl:otherwise>
<fo:basic-link internal-destination="{#refid}">
<xsl:value-of select="current()" />
</fo:basic-link>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
It does work on some cases, but since position() is not always 1 some images are not getting inserted correctly. What are my options?
Thank you!
EDIT: I should clarify. The image should get inserted at the first occurence of a "new" refid. Thus. Each refid only has one image and every other cross-refelement with the same refid points to that image

Answer 1

You have to change the test in your xsl:when, so that it is true only for the first occurrence of each #ref-id value; in other words, you have to check that no preceding cross-ref element has the same #ref-id:
<xsl:when test="not(preceding::cross-ref[#ref-id = current()/#ref_id])">
...

Answer 2

If you are using XSLT 2.0 or XSLT 3.0, if you add an xsl:key as a top-level element:
<xsl:key name="cross-ref" match="cross-ref" use="#refid" />
then you can change your xsl:when to:
<xsl:when test=". is key('cross-ref', #refid)[1]">
This works because key() returns nodes in document order (https://www.w3.org/TR/xslt20/#keys). This is potentially quicker (on large documents) than using the preceding axis, but to be sure you'd have to test it by running on your documents with your XSLT processor.
If you're using XSLT 1.0, you'd have to do it using a Meunchian Grouping-like trick:
<xsl:when test="count(. | key('cross-ref', #refid)[1]) = 1">
but that is much less readable than the XSLT 2.0 version.