XSLT Grouping elements inside two siblings - xslt

Question

I'm trying to wrap my head around this and I think the easiest way to explain it is to just show you, below. I've seen this but it doesn't always apply due to the fact I have standalone items also at the end which would match.
The seemingly tricky part is Whatever3 to Whatever6, and then Whatever7 and Whatever8, then finally the new position of Whatever9 - they need to be grouped and the original sequence maintained. (Ignore my naming, there is no way to use xsl:sort)
I've considered xsl:for-each with xsl:if inside, but issue is you can't guarantee how many "groups" vs "non-group" items there are.
Thanks!
XML
<root>
<item>
<position>1</position>
<label>Whatever1</label>
</item>
<item>
<position>2</position>
<label>Whatever2</label>
</item>
<item>
<position>3</position>
<label>Whatever3</label>
<marker id="unique1">start_group</marker>
</item>
<item>
<position>4</position>
<label>Whatever4</label>
</item>
<item>
<position>5</position>
<label>Whatever5</label>
</item>
<item>
<position>6</position>
<label>Whatever6</label>
<marker>last_in_group</marker>
</item>
<item>
<position>7</position>
<label>Whatever7</label>
<marker id="unique2">start_group</marker>
</item>
<item>
<position>8</position>
<label>Whatever8</label>
<marker>last_in_group</marker>
</item>
<item>
<position>9</position>
<label>Whatever9</label>
</item>
</root>
Result
<structure>
<item>
<position>1</position>
<label>Whatever1</label>
</item>
<item>
<position>2</position>
<label>Whatever2</label>
</item>
<group position="3" id="unique1">
<item>
<position>1</position>
<label>Whatever3</label>
</item>
<item>
<position>2</position>
<label>Whatever4</label>
</item>
<item>
<position>3</position>
<label>Whatever5</label>
</item>
<item>
<position>4</position>
<label>Whatever6</label>
</item>
</group>
<group position="4" id="uniqueid2">
<item>
<position>1</position>
<label>Whatever7</label>
</item>
<item>
<position>2</position>
<label>Whatever8</label>
</item>
</group>
<item>
<position>**5**</position>
<label>Whatever9</label>
</item>
</structure>
======================
Here is what I have so far, the only problem I have (besides it being messy) is Whatever4 and Whatever5 are showing up outside the Group.
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:template match="root">
<structure>
<xsl:apply-templates select="item[not(marker)] | item[marker='start_group']"/>
</structure>
</xsl:template>
<xsl:template match="item[marker='start_group']">
<group>
<xsl:variable name="currentPosition" select="number(position/text())"/>
<xsl:variable name="lastGroup" select="count(following-sibling::*[local-name() = 'item' and marker='last_in_group'][1]/preceding-sibling::*) + 1"/>
<xsl:attribute name="position">
<xsl:value-of select="$currentPosition"/>
</xsl:attribute>
<xsl:attribute name="id">
<xsl:value-of select="marker/#id"/>
</xsl:attribute>
<item>
<position><xsl:value-of select="number(position/text()) - $currentPosition + 1"/></position>
<label><xsl:value-of select="label/text()"/></label>
</item>
<!-- position() gets reset in for-loop, so need to adjust with outer position -->
<xsl:for-each select="following-sibling::item[(position() + $currentPosition) <= $lastGroup]">
<item>
<position><xsl:value-of select="number(position/text()) - $currentPosition + 1"/></position>
<label><xsl:value-of select="label/text()"/></label>
</item>
</xsl:for-each>
</group>
</xsl:template>
<xsl:template match="item[not(marker)]">
<item>
<position><xsl:value-of select="position/text()"/></position>
<label><xsl:value-of select="label/text()"/></label>
</item>
</xsl:template>
</xsl:stylesheet>

Answer 1

I. XSLT 1.0 Solution:
This transformation:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:key name="kFollowing"
match="item[not(marker[. = 'start_group'])
and
preceding-sibling::*[marker][1]/marker = 'start_group'
]"
use="generate-id(preceding-sibling::*
[marker[. = 'start_group']]
[1])"/>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="item[marker[. = 'start_group']]">
<group position="{1 +count(preceding-sibling::*[. = 'start_group'])}"
id="{marker/#id}">
<xsl:copy-of select=".|key('kFollowing', generate-id())"/>
</group>
</xsl:template>
<xsl:template match=
"item[not(marker[. = 'start_group'])
and
preceding-sibling::*[marker][1]/marker = 'start_group'
]"/>
</xsl:stylesheet>
when applied on the provided XML document:
<root>
<item>
<position>1</position>
<label>Whatever1</label>
</item>
<item>
<position>2</position>
<label>Whatever2</label>
</item>
<item>
<position>3</position>
<label>Whatever3</label>
<marker id="unique1">start_group</marker>
</item>
<item>
<position>4</position>
<label>Whatever4</label>
</item>
<item>
<position>5</position>
<label>Whatever5</label>
</item>
<item>
<position>6</position>
<label>Whatever6</label>
<marker>last_in_group</marker>
</item>
<item>
<position>7</position>
<label>Whatever7</label>
<marker id="unique2">start_group</marker>
</item>
<item>
<position>8</position>
<label>Whatever8</label>
<marker>last_in_group</marker>
</item>
<item>
<position>9</position>
<label>Whatever9</label>
</item>
</root>
produces the wanted, correct result:
<root>
<item>
<position>1</position>
<label>Whatever1</label>
</item>
<item>
<position>2</position>
<label>Whatever2</label>
</item>
<group position="1" id="unique1">
<item>
<position>3</position>
<label>Whatever3</label>
<marker id="unique1">start_group</marker>
</item>
<item>
<position>4</position>
<label>Whatever4</label>
</item>
<item>
<position>5</position>
<label>Whatever5</label>
</item>
<item>
<position>6</position>
<label>Whatever6</label>
<marker>last_in_group</marker>
</item>
</group>
<group position="1" id="unique2">
<item>
<position>7</position>
<label>Whatever7</label>
<marker id="unique2">start_group</marker>
</item>
<item>
<position>8</position>
<label>Whatever8</label>
<marker>last_in_group</marker>
</item>
</group>
<item>
<position>9</position>
<label>Whatever9</label>
</item>
</root>
II. XSLT 2.0 solution:
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="/*">
<root>
<xsl:for-each-group select="item" group-starting-with=
"*[marker eq 'start_group'
or
not(marker)
and
preceding-sibling::*[marker][1]/marker eq 'last_in_group'
]
">
<xsl:choose>
<xsl:when test="current-group()[1]/marker">
<group position=
"{1 +count(current-group()[1]
/preceding-sibling::*
[marker = 'start_group'])}"
id="{marker/#id}">
<xsl:apply-templates select="current-group()"/>
</group>
</xsl:when>
<xsl:otherwise>
<xsl:apply-templates select="current-group()"/>
</xsl:otherwise>
</xsl:choose>
</xsl:for-each-group>
</root>
</xsl:template>
</xsl:stylesheet>
When this XSLT 2.0 transformation is applied on the same XML document (above), the same correct result is produced.