How can I produce columnar output from 2-level grouping in XML? - xslt

Question

I have the following xml:
input
<page>
<group category="cat1">
<item fileunder="#">.45 colt</item>
<item fileunder="#">8 queens</item>
<item fileunder="#">9 lives</item>
<item fileunder="#">99 bottles of beer</item>
<item fileunder="A">An innocent man</item>
<item fileunder="A">Academy awards</item>
<item fileunder="B">Before the dawn</item>
</group>
<group category="cat2">
<item fileunder="R">Rows of houses</item>
</group>
</page>
The input items are already sorted.
desired output
I want to produce a 3-column HTML table for every group, with a subheading (a 3-column spanning cell) for each distinct fileunder, optimally presented in a top-down, then-next-column (the items are already sorted):
<table>
<tr><td colspan="3">#</td></tr>
<tr><td>.45 colt</td><td>9 lives</td><td>99 bottles of beer</td></tr>
<tr><td>8 queens</td></tr>
<tr><td colspan="3">A</td></tr>
<tr><td>An innocent man</td><td>Academy awards</td></tr>
<tr><td colspan="3">B</td></tr>
<tr><td>Before the dawn</td></tr>
</table>
<table>
<tr><td colspan="3">R</td></tr>
<tr><td>Rows of houses</td></tr>
</table>
I can live if the items are presented as left-to-right, then-next-row.
What I have so far is:
current xslt
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:key name="itm_grp" match="/page/group/item" use="concat(../#category,':',#fileunder)"/>
<xsl:template match="page/group">
<table>
<xsl:for-each select="item[.=key('itm_grp',concat(../#category,':',#fileunder))[1]]">
<tr><td colspan="3"><xsl:value-of select="#fileunder"/></td></tr>
<xsl:variable name="nodeset" select="key('itm_grp',concat(../#category,':',#fileunder))"/>
<xsl:for-each select="$nodeset[position() mod 3=1]">
<tr>
<td><xsl:value-of select="."/></td>
<td><xsl:value-of select="following-sibling::item[1]"/></td>
<td><xsl:value-of select="following-sibling::item[2]"/></td>
</tr>
</xsl:for-each>
</xsl:for-each>
</table>
</xsl:template>
</xsl:stylesheet>
which produces a left-to-right, then-next-row output (non-optimal); however, the following-sibling selects produce a “bleed-through” effect:
#
.45 colt 8 queens 9 lives
99 bottles of beer An innocent man Academy awards
A
An innocent man Academy awards Before the dawn
B
Before the dawn
R
Rows of houses
As you can see, fileunder # has two A items, and fileunder A has one B item.
So, my question is:
How can I produce the desired output (column-wise)?
If I can't do that, how can I have the row-wise output avoiding the “bleeding”?
Please note that I have very little experience with XSLT, so if my code is blatantly inefficient/idiotic/whatever, please feel free to educate me by replacing all of it!
NB: XSLT version 1, so apparently no index-of function is available.

Answer 1

There is a slight contradiction between your narrative and your listed expected output. You have asked for top-down, then left-right column fill order, which you have so in the listing for the non-empty values, but not for the empties. This spatial order implies that a whole column must be filled out before the next column can begin. I have assumed that your listing was a mistake and what your really want in output is ...
<table>
<tr>
<td colspan="3">#</td>
</tr>
<tr>
<td>.45 colt</td>
<td>9 lives</td>
<td>&npsp;</td>
</tr>
<tr>
<td>8 queens</td>
<td>99 bottles of beer</td>
<td>&npsp;</td>
</tr>
<tr>
<td colspan="3">A</td>
</tr>
<tr>
<td>An innocent man</td>
<td>Academy awards</td>
<td>&npsp;</td>
</tr>
<tr>
<td colspan="3">B</td>
</tr>
<tr>
<td>Before the dawn</td>
<td>&npsp;</td>
<td>&npsp;</td>
</tr>
</table>
<table>
<tr>
<td colspan="3">R</td>
</tr>
<tr>
<td>Rows of houses</td>
<td>&npsp;</td>
<td>&npsp;</td>
</tr>
</table>
... which is consistent top-down, then left-right column fill order.
This XSLT 1.0 style-sheet...
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="html" doctype-system="about:legacy-compat" encoding="UTF-8" indent="yes" />
<xsl:strip-space elements="*" />
<xsl:key name="kItemByFile" match="item" use="concat(../#category,':',#fileunder)"/>
<xsl:template match="/">
<html lang="en">
<head><title>Songs</title></head>
<body>
<xsl:apply-templates select="*/group" />
</body>
</html>
</xsl:template>
<xsl:template match="group">
<xsl:variable name="cat" select="concat(#category,':')" />
<table>
<xsl:apply-templates select="item[
generate-id() = generate-id(key('kItemByFile',concat($cat,#fileunder))[1])]"
mode="group-head" />
</table>
</xsl:template>
<xsl:template match="item" mode="group-head">
<xsl:variable name="items"
select="key('kItemByFile',concat(../#category,':',#fileunder))" />
<xsl:variable name="row-count" select="ceiling( count($items) div 3)" />
<tr><td colspan="3"><xsl:value-of select="#fileunder" /></td></tr>
<xsl:for-each select="$items[position() <= $row-count]">
<xsl:variable name="pos" select="position()" />
<xsl:apply-templates select="." mode="row">
<xsl:with-param name="items" select="$items" />
<xsl:with-param name="row" select="$pos" />
<xsl:with-param name="row-count" select="$row-count" />
</xsl:apply-templates>
</xsl:for-each>
</xsl:template>
<xsl:template match="item" mode="row">
<xsl:param name="items" select="/.." />
<xsl:param name="row" select="1" />
<xsl:param name="row-count" select="1" />
<tr>
<xsl:apply-templates select="
$items[(position() mod $row-count) = ($row mod $row-count)]" mode="td" />
<xsl:variable name="full-cols" select="floor((count($items) div $row-count))" />
<xsl:variable name="part-col" select="number($row <
((count($items) mod $row-count) + 1))" />
<xsl:variable name="empties" select="3 - ($full-cols + $part-col)" />
<xsl:for-each select="(document('')/*/*)[position() <= $empties]">
<xsl:call-template name="empty-cell" />
</xsl:for-each>
</tr>
</xsl:template>
<xsl:template match="item" mode="td">
<td><xsl:value-of select="." /></td>
</xsl:template>
<xsl:template name="empty-cell">
<td> </td>
</xsl:template>
</xsl:stylesheet>
...when applied to this input...
<page>
<group category="cat1">
<item fileunder="#">.45 colt</item>
<item fileunder="#">8 queens</item>
<item fileunder="#">9 lives</item>
<item fileunder="#">99 bottles of beer</item>
<item fileunder="A">An innocent man</item>
<item fileunder="A">Academy awards</item>
<item fileunder="B">Before the dawn</item>
</group>
<group category="cat2">
<item fileunder="R">Rows of houses</item>
</group>
</page>
...yields...
<!DOCTYPE html SYSTEM "about:legacy-compat">
<html lang="en">
<head>
<META http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Songs</title>
</head>
<body>
<table>
<tr>
<td colspan="3">#</td>
</tr>
<tr>
<td>.45 colt</td>
<td>9 lives</td>
<td> </td>
</tr>
<tr>
<td>8 queens</td>
<td>99 bottles of beer</td>
<td> </td>
</tr>
<tr>
<td colspan="3">A</td>
</tr>
<tr>
<td>An innocent man</td>
<td>Academy awards</td>
<td> </td>
</tr>
<tr>
<td colspan="3">B</td>
</tr>
<tr>
<td>Before the dawn</td>
<td> </td>
<td> </td>
</tr>
</table>
<table>
<tr>
<td colspan="3">R</td>
</tr>
<tr>
<td>Rows of houses</td>
<td> </td>
<td> </td>
</tr>
</table>
</body>
</html>
Note
For the empty cells in the output, when viewing the lexical HTML, you will get either or the literal white space equivalent. It is XSLT processor implementation dependant, but should not cause you any concern because it is model-equivalent.

Answer 2

Easiest way to fix that:
<xsl:variable name="header" select="#fileunder"/>
...
<xsl:value-of select="following-sibling::item[#fileunder=$header][1]"/>
<xsl:value-of select="following-sibling::item[#fileunder=$header][2]"/>