@next URLs in multi-category search results are broken

[Conal-Tuohy]

At the moment I've written code in TroveProxy to fix these broken URLs, and it seems to me that the Trove API actually could incorporate this same fix, so I'd like to be able to move this fix "upstream" to Trove, so that other people who aren't using TroveProxy don't experience these broken links.

The XML response includes <records> elements with next attributes whose values are URLs which include a single category parameter whose value is a list of category names, separated by a (URL-encoded) comma. If I replace that category parameter with one whose value is taken from the code attribute of the parent (i.e. <category>) element of the <records> element, then the resulting URL does work.

e.g. take the following query URL:
https://api.trove.nla.gov.au/v3/result?category=book&category=newspaper&q=water%20dragon&s=*&n=1&bulkHarvest=true

The result looks like this:

<response>
  <query>water dragon</query>
  <category code="book" name="Books &amp; Libraries">
    <records s="*" n="1" total="3700" next="https://api.trove.nla.gov.au/v3/result?category=book%2Cnewspaper&amp;q=water+dragon&amp;n=1&amp;bulkHarvest=true&amp;s=AoEqc3UxMDAwMTE4Ng%3D%3D" nextStart="AoEqc3UxMDAwMTE4Ng==">
      <!-- omitted for brevity -->
    </records>
  </category>
  <category code="newspaper" name="Newspapers &amp; Gazettes">
    <records s="*" n="1" total="98345" next="https://api.trove.nla.gov.au/v3/result?category=book%2Cnewspaper&amp;q=water+dragon&amp;n=1&amp;bulkHarvest=true&amp;s=AoEpMTAwMDI0NDE5" nextStart="AoEpMTAwMDI0NDE5">
      <!-- omitted for brevity -->
    </records>
  </category>
</response>

Those "next" URLs are broken, but if I change them like so, they do appear to work correctly:

<response>
  <query>water dragon</query>
  <category code="book" name="Books &amp; Libraries">
    <records s="*" n="1" total="3700" next="https://api.trove.nla.gov.au/v3/result?category=book&amp;q=water+dragon&amp;n=1&amp;bulkHarvest=true&amp;s=AoEqc3UxMDAwMTE4Ng%3D%3D" nextStart="AoEqc3UxMDAwMTE4Ng==">
      <!-- omitted for brevity -->
    </records>
  </category>
  <category code="newspaper" name="Newspapers &amp; Gazettes">
    <records s="*" n="1" total="98345" next="https://api.trove.nla.gov.au/v3/result?category=newspaper&amp;q=water+dragon&amp;n=1&amp;bulkHarvest=true&amp;s=AoEpMTAwMDI0NDE5" nextStart="AoEpMTAwMDI0NDE5">
      <!-- omitted for brevity -->
    </records>
  </category>
</response>

The code I'm using to fix these broken URLs is here:

TroveProxy/src/xslt/fix-trove-response.xsl

Line 4 in 0778f71

<xsl:variable name="category-code" select="ancestor::category/@code"/>

TroveProxy/src/xslt/fix-trove-response.xsl

Lines 13 to 23 in 0778f71

	<xsl:variable name="parameters" select="$query => tokenize('&amp;')"/>
	<!-- throw out any category parameters that don't match current category -->
	<xsl:variable name="refined-parameters" select="
	(
	$parameters[substring-before(., '=') != 'category'], (: ditch any categories :)
	concat('category=', $category-code) (: add the current category back :)
	)
	"/>
	<xsl:attribute name="next" select="
	concat($base-uri, '?', string-join($refined-parameters, '&amp;'))
	"/>

[Conal-Tuohy]

Followed up on this with Trove Support this morning