XSLT transformation to make Koha's OAI-PMH records comply with the harvesting for Biblioteksøk

biblioteksok.xslt

<xsl:stylesheet version="1.0"
 xmlns:marc="http://www.loc.gov/MARC21/slim"
 xmlns:items="http://www.koha-community.org/items"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 xmlns:package="info:srw/extension/13/package-v1.0">

 <xsl:output method="xml" omit-xml-declaration="yes" indent="yes"/>

 <xsl:template match="node()|@*">
  <xsl:copy>
   <xsl:apply-templates select="node()|@*"/>
  </xsl:copy>
 </xsl:template>

 <!-- Remove the original versions of these fields -->
 <xsl:template match="marc:controlfield[@tag=001]"/>
 <xsl:template match="marc:datafield[@tag=850]"/>

 <!-- Add a new 001 that contains the biblionumber from 999$c -->
 <xsl:template match="marc:leader">
  <xsl:copy>
   <xsl:apply-templates select="@*|node()"/>
  </xsl:copy>
   <xsl:if test="not(marc:controlfield[@tag=001])">
    <xsl:text>
  </xsl:text><xsl:element name="controlfield" xmlns="http://www.loc.gov/MARC21/slim">
     <xsl:attribute name="tag">001</xsl:attribute>
     <xsl:value-of select="//marc:datafield[@tag=999]/marc:subfield[@code='c']/text()"/>
    </xsl:element>
   </xsl:if>
 </xsl:template>

 <!-- Add a new 850$a that contains a hardcoded string -->
 <xsl:template match="marc:datafield[@tag=999]">
 <!-- xsl:template match="marc:record" -->
  <xsl:copy>
   <xsl:apply-templates select="@*|node()"/>
  </xsl:copy>
  <xsl:if test="not(marc:controlfield[@tag=850])">
    <xsl:text>
  </xsl:text>
    <xsl:element name="datafield" xmlns="http://www.loc.gov/MARC21/slim">
      <xsl:attribute name="ind1"><xsl:text> </xsl:text></xsl:attribute>
      <xsl:attribute name="ind2"><xsl:text> </xsl:text></xsl:attribute>
      <xsl:attribute name="tag">850</xsl:attribute>
      <xsl:text>
    </xsl:text>
      <xsl:element name="subfield">
        <xsl:attribute name="code">a</xsl:attribute>
        <xsl:text>NO-1120127</xsl:text>
      </xsl:element>
    </xsl:element>
  </xsl:if>
 </xsl:template>

</xsl:stylesheet>

record.marcxml

<?xml version="1.0" encoding="UTF-8"?>
<record 
xmlns='http://www.loc.gov/MARC21/slim' 
xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' 
xsi:schemaLocation='http://www.loc.gov/MARC21/slim http://www.loc.gov/standards/marcxml/schema/MARC21slim.xsd'>
  <leader>00581nam a2200205 a 4500</leader>
  <controlfield tag="001">999</controlfield>
  <controlfield tag='008'>                       r           eng  </controlfield>
  <datafield ind1=' ' ind2=' ' tag='100'>
    <subfield code='a'>Author 2</subfield>
  </datafield>
  <datafield ind1=' ' ind2=' ' tag='245'>
    <subfield code='a'>Title 2</subfield>
  </datafield>
  <datafield ind1=' ' ind2=' ' tag='999'>
    <subfield code='c'>2</subfield>
    <subfield code='d'>2</subfield>
  </datafield>
</record>

test.pl

#!/usr/bin/perl -w

use XML::LibXML;
use XML::LibXSLT;
use Modern::Perl;

my $xsl='biblioteksok.xslt';
my $xml='record.marcxml';

my $xslt = XML::LibXSLT->new();
  
my $source = XML::LibXML->load_xml(location => $xml);
my $style_doc = XML::LibXML->load_xml(location=>$xsl, no_cdata=>1);
  
my $stylesheet = $xslt->parse_stylesheet($style_doc);
 
my $results = $stylesheet->transform($source);
  
print $stylesheet->output_as_bytes($results);