XQuery to generate a catalog of EXPath package XSLT stylesheets

xquery version "3.1";

(:  LIBRARIES  :)
  declare namespace db="http://basex.org/modules/db";
  declare namespace file="http://expath.org/ns/file";
(:  NAMESPACES  :)
  declare default element namespace "urn:oasis:names:tc:entity:xmlns:xml:catalog";
  declare namespace output="http://www.w3.org/2010/xslt-xquery-serialization";
  declare namespace pkg="http://expath.org/ns/pkg";
(:  OPTIONS  :)
  declare option output:indent "yes";
  declare option output:method "xml";

(:~
  Find all EXPath Package <xslt>s in a BaseX Repository and generate an XML catalog to map their
  filesystem paths to their URIs. With a catalog saved to the filesystem, you can include it in the
  BaseX "CATALOG" option (https://docs.basex.org/main/Options#catalog). You may need to place Norm
  Tovey-Walsh's Catalog Resolver on your classpath in order to use the catalog entry URIs in
  <xsl:import>s (see https://docs.basex.org/main/Catalog_Resolver for more information).

  EXPath Packaging System specification: https://expath.org/spec/pkg

  @author Ash Clark
  @since 2026
 :)

(:
    MAIN QUERY
 :)

(: Get the path to BaseX's repository. :)
let $repoDir :=
  let $optStr := db:option('repopath')
  return
    (: Make sure the path ends with "/". :)
    if ( ends-with($optStr, '/') ) then $optStr else $optStr||'/'
let $xslPackages :=
  (: Identify the directories within the repository. Each directory should correspond with a package,
    either EXPath or internal. We're only interested in the EXPath ones. :)
  for $packagePath in file:children($repoDir)[ends-with(., '/')]
  (: Try to identify the EXPath package descriptor in the package directory. The EXPath package standard
    says the descriptor should always be in the outermost directory and named "expath-pkg.xml". If the
    file isn't there, we can ignore this directory. :)
  let $packageDescriptor :=
    let $path := concat($packagePath,'expath-pkg.xml')
    return
      if ( not(doc-available($path)) ) then () else
        (: We can also ignore this directory if it HAS a package descriptor but no <xslt> listing. :)
        doc($path)/pkg:package[pkg:xslt]
  (: Filter out directories so we're only looking at EXPath packages with defined XSLT components. :)
  where exists($packageDescriptor)
  (: Gather information on the XSLT available through this XSLT package. :)
  let $packageUri := $packageDescriptor/@name/data(.)
  (: Get a sequence of subdirectories within the package directory for later testing. :)
  let $packageSubdirs := file:children($packagePath)[ends-with(., '/')]
  (: The EXPath package spec allows multiple <xslt>s can be defined. Each one should get its own catalog
    entry. :)
  for $xsltConfig in $packageDescriptor/pkg:xslt
  let $stylesheetPath :=
    let $relativePath := $xsltConfig/pkg:file/data(.)
    (: According to the EXPath package spec, the usable components of the package should be placed in a
      content/ directory alongside the package descriptor. However, FunctX's package (at least in BaseX)
      uses a directory named functx/ instead. Since <file> is supposed to be relative to the content
      directory (it doesn't specify which directory it's in), we need to try to identify where the
      stylesheet is stored in order to generate a catalog entry for its filesystem path. :)
    return
      (: Try using the base package path too, just in case. While there's a spec for the EXPath
        packaging system, I get the sense that people don't always use it as intended. (For years I
        didn't!) Someone may have decided to use a relative path from the EXPath descriptor file's
        directory, or placed the XSLT in that directory. :)
      for $directory in ($packagePath, $packageSubdirs)
      let $tryStylesheetPath := 'file://'||$directory||$relativePath
      return
        if ( doc-available($tryStylesheetPath) ) then
          $tryStylesheetPath
        else ()
  return
    if ( empty($stylesheetPath) ) then () else
      <uri name="{ $xsltConfig/pkg:import-uri/data(.) }" uri="{ $stylesheetPath }"/>
return
  (: Gather any catalog entries into an XML catalog. :)
  if ( empty($xslPackages) ) then () else
    <catalog>
      { $xslPackages }
    </catalog>