Generate a breadcrumb trail with xsl from a node structure - xslt

Question

I have difficulties to write a template that generates a breadcrumb trial out of a node structure. It is not working correctly up to now, there is some flaw in my thinking how it should walk the item path.
Consider the following page structure:
<!-- ===== SITE PAGE STRUCTURE ===================================== -->
<index>
<item section="home" id="index"></item>
<item section="service" id="index">
<item id="content-management-systems">
<item id="p1-1"/>
<item id="p1-2"/>
<item id="p1-3"/>
</item>
<item id="online-stores"></item>
<item id="search-engines-and-ir"></item>
<item id="web-applications"></item>
</item>
<item section="solutions" id="index">
<item id="document-clustering"></item>
</item>
<item section="company" id="index">
<item section="company" id="about"></item>
<item section="company" id="philosophy" ></item>
...
</item>
...
</item>
This site index represents a site-structure of xml content pages in its hierarchy (consider it to be a menu). It contains of sections, that represent the site sections just as home, company, service, solutions, etc. These sections can contain sub-sections with pages, or just regular content pages. A content page (its xml contents such as title, text content, etc) is identified by the #id attribute in the item tree. The #id attribute mainly is used to fetch the content of the entire page that will be rendered to html.
The breadcrumb template uses the item node #id attribute to get the title of the page (which will be shown in the breadcrumb trail).
I try to implement the following template that walks the tree by checking the target section attribute #section and the target page attribute #id in the tree. I expect it to walk the axis down until the target item_target is found by comparing the ancestors #section attribute and the #id with $item_target of each node in that axis.
For example: Attribute *$item_section=service* and the page id *target item_target=p1-1* should now recursively "walk" to the section branch "service" (depth 1), check if the target page #id is found on this level. In this case it is not found, so it makes the next recurive call (via apply-templates) to the next item node level (in this case it would be content-management-systems, there the target item page p1-1 is found, so the trail process is finished:
The result should like this:
home >> service >> content management systems >> p1-1
But unfortunately it is not working correct, at least not in every case. Also maybe it can be solved more easily. I try to implement it as an recursive template that walks from the top (level 0) to the target page (item node) as a leaf.
<!-- walk item path to generate a breadcrumb trail -->
<xsl:template name="breadcrumb">
<a>
<xsl:attribute name="href">
<xsl:text>/</xsl:text>
<xsl:value-of select="$req-lg"/>
<xsl:text>/home/index</xsl:text>
</xsl:attribute>
<xsl:value-of select="'Home'"/>
</a>
<xsl:apply-templates select="$content/site/index" mode="Item-Path">
<xsl:with-param name="item_section" select="'service'"/>
<xsl:with-param name="item_target" select="'search-engines-and-ir'"/>
<xsl:with-param name="depth" select="0"/>
</xsl:apply-templates>
</xsl:template>
<xsl:template match="item" mode="Item-Path">
<xsl:param name="item_section" />
<xsl:param name="item_target" />
<xsl:param name="depth" />
<!--
depth=<xsl:value-of select="$depth"/>
count=<xsl:value-of select="count(./node())"/><br/>
-->
<xsl:variable name="cur-id" select="#id"/>
<xsl:variable name="cur-section" select="#section"/>
<xsl:choose>
<xsl:when test="#id=$item_target">
>>
<a>
<xsl:attribute name="href">
<xsl:text>/</xsl:text>
<!-- req-lg: global langauge variable -->
<xsl:value-of select="$req-lg"/>
<xsl:text>/</xsl:text>
<xsl:value-of select="$item_section"/>
<xsl:text>/</xsl:text>
<xsl:if test="$depth = 2">
<xsl:value-of select="../#id"/>
<xsl:text>/</xsl:text>
</xsl:if>
<xsl:value-of select="#id"/>
</xsl:attribute>
<xsl:value-of
select="$content/page[#id=$cur-id]/title"/>
</a>
</xsl:when>
<xsl:otherwise>
<xsl:if test="ancestor-or-self::item/#section = $item_section and count(./node()) > 0">
>>:
<a>
<xsl:attribute name="href">
<xsl:text>/</xsl:text>
<!-- req-lg: global langauge variable -->
<xsl:value-of select="$req-lg"/>
<xsl:text>/</xsl:text>
<xsl:value-of select="$item_section"/>
<xsl:text>/</xsl:text>
<xsl:if test="$depth = 2">
<xsl:value-of select="../#id"/>
<xsl:text>/</xsl:text>
</xsl:if>
<xsl:value-of select="#id"/>
</xsl:attribute>
<xsl:value-of
select="$content/page[#id=$cur-id and #section=$item_section]/title"/>
</a>
</xsl:if>
</xsl:otherwise>
</xsl:choose>
<xsl:apply-templates select="item" mode="Item-Path">
<xsl:with-param name="item_section" select="$item_section"/>
<xsl:with-param name="item_target" select="$item_target"/>
<xsl:with-param name="depth" select="$depth + 1"/>
</xsl:apply-templates>
</xsl:template>
So as the hardcoded parameters in the template breadcrumb, target section = 'service' and target page = 'search-engines-and-ir', I expect an output like
home >> service >> search-engines-and-ir
But the output is
home >> service >> content-management-systems >> search-engines-and-ir
which is obviously not correct.
Can anybody give me a hint how to correct this issue? It would be even more elegant to avoid that depth checking, but up to now I cannot think of a other way, I am sure there is a more elegant solution.
I work with XSLT 1.0 (libxml via PHP5).
Hope my question is clear enough, if not, please ask :-) Thanks for the help in advance!

Answer 1

As simple as this:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:key name="kNodeById" match="item" use="#id"/>
<xsl:template match="/">
<xsl:text>home</xsl:text>
<xsl:call-template name="findPath">
<xsl:with-param name="pStart" select="'service'"/>
<xsl:with-param name="pEnd" select="'search-engines-and-ir'"/>
</xsl:call-template>
</xsl:template>
<xsl:template name="findPath">
<xsl:param name="pStart"/>
<xsl:param name="pEnd"/>
<xsl:for-each select=
"key('kNodeById', $pEnd)
[ancestor::item[#section=$pStart]]
[1]
/ancestor-or-self::item
[not(descendant::item[#section=$pStart])]
">
<xsl:value-of select=
"concat('>>', #id[not(../#section)], #section)"/>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
the wanted, correct result is produced:
home>>service>>search-engines-and-ir
Do Note:
This solution prints the breadcrumb from any node -- anywhere in the hierarchy to any of its descendent nodes -- anywhere in the hierarchy. More precisely, for the first item (in document order) with id attribute equal to $pEnd, the breadcrumb is generated from its inner-most ancestor whose section attribute is equal to $pStart -- to that item element.
This solution should be much more efficient than any solution using //, because we are using a key to locate efficiently the "end" item element.
II. XSLT 2.0 solution:
Much shorter and easier -- an XPathe 2.0 single expression:
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:key name="kNodeById" match="item" use="#id"/>
<xsl:template match="/">
<xsl:value-of select=
"string-join(
(
'home',
key('kNodeById', $pEnd)
[ancestor::item[#section=$pStart]]
[1]
/ancestor-or-self::item
[not(descendant::item[#section=$pStart])]
/(#id[not(../#section)], #section)[1]
),
'>>'
)
"/>
</xsl:template>
</xsl:stylesheet>

Answer 2

You can just iterate over the ancestor-or-self:: axis . This is easy to do without recursion. For example...
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="html"/>
<xsl:template match="/">
<html><body>
<xsl:call-template name="bread-crumbs">
<xsl:with-param name="items" select="*/item" />
<xsl:with-param name="section" select="'service'" />
<xsl:with-param name="leaf" select="'p1-2'" />
</xsl:call-template>
</body></html>
</xsl:template>
<xsl:template name="bread-crumbs">
<xsl:param name="items" />
<xsl:param name="section" />
<xsl:param name="leaf" />
<xsl:value-of select="concat($section,'>>')" />
<xsl:for-each select="$items/self::item[#section=$section]//item[#id=$leaf]/
ancestor-or-self::item[not(#section)]">
<xsl:value-of select="#id" />
<xsl:if test="position() != last()">
<xsl:value-of select="'>>'" />
</xsl:if>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
...on your sample input yields...
<html>
<body>service>>content-management-systems>>p1-2</body>
</html>
...which renders as...
service>>content-management-systems>>p1-2