xslt select rss item by both child node and position

1
votes

Using XSLT 1.0 with an RSS calendar feed, I want to exclude expired items - those with pubDates before the current date - then include only three current items. The result should be the next three future events. I used http://exslt.org/date/index.html to create a variable for the current system date. The problem is that when I select="item[not(position() > 4)] and substring(item/pubDate,5,11) &gt= $current", I end up with less than three items if any of the first ones are expired. Apparently my code selects three items then removes the expired ones, which is not what I want. Is it possible to save a copy of the unexpired items and then select three of them?

Since XSLT 1.0 doesn't provide inequality string comparison operators, I may not be able to see if a value such as "30 Oct 2013" is greater than "29 Oct 2013," I can format the values as 30102013 and 29102013 instead, but it still seems that I'm trying to concatenate channel/item/pubDate before I have selected it. So knowing how to process the XML/RSS in two stages, if possible, would be helpful.

I have tried several techniques, with similar results:

  <xsl:for-each select="substring(item/pubDate,5,11) &gt;= $current and item[not(position() &gt; 4)]">

  <xsl:template match="item[not(position() &gt; 4)]">
       <xsl:apply-templates select="item"/>

  <xsl:for-each select="substring(item/pubDate,5,11) &gt;= $current">
       <xsl:if test=" item[not(position() &gt; 4)]">

Sample XML:

<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
  <channel>
    <atom:link href="http://calendar.example.edu/" rel="self" type="application/rss+xml"/>
    <title>University Calendar - Featured Events</title>
    <link>http://calendar.example.edu/</link>
    <description>List of featured events on calendar.example.edu</description>
    <language>en-us</language>
    <pubDate>Tue, 27 Oct 2013 20:47:05 CDT</pubDate>
    <item>
        <title>Creative Movement Program Student Show</title>
        <description/>
        <link>http://calendar.example.edu/?&amp;y=2013&amp;m=10&amp;d=30&amp;eventdatetime_id=19721</link>
        <guid>calendar.example.edu/?&amp;y=2013&amp;m=10&amp;d=30&amp;eventdatetime_id=19721</guid>
        <pubDate>Wed 30 Oct 2013, 17:00:00 CDT</pubDate>
    </item>
    <item>
        <title>Philosophy Career Fair</title>
        <description>The Department of Philosophy brings recruiters from around the state to interview seniors and alumni.</description>
        <link>http://calendar.example.edu/?&amp;y=2013&amp;m=11&amp;d=04&amp;eventdatetime_id=16427</link>
        <guid>calendar.example.edu/?&amp;y=2013&amp;m=11&amp;d=04&amp;eventdatetime_id=16427</guid>
        <pubDate>Mon 04 Nov 2013, 07:00:00 CDT</pubDate>
    </item>
    <item>
        <title>Football vs. Caltech</title>
        <description/>
        <link>http://calendar.example.edu/?&amp;y=2013&amp;m=12&amp;d=07&amp;eventdatetime_id=16521</link>
        <guid>calendar.example.edu/?&amp;y=2013&amp;m=12&amp;d=07&amp;eventdatetime_id=16521</guid>
        <pubDate>Sat 07 Dec 2013, 00:00:00 CDT</pubDate>
    </item>
    <item>
        <title>Mural Exhibition</title>
        <description>The College of Arts presents an overview of wall paintings from the Caves of Lascaux to the Kiev train station.</description>
        <link>http://calendar.example.edu/?&amp;y=2014&amp;m=01&amp;d=14&amp;eventdatetime_id=16759</link>
        <guid>calendar.example.edu/?&amp;y=2014&amp;m=01&amp;d=14&amp;eventdatetime_id=16759</guid>
        <pubDate>Tue 14 Jan 2014, 07:00:00 CDT</pubDate>
    </item>
  </channel>
</rss>

Current XSLT: 

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" extension-element-prefixes="date" version="1.0" xmlns:date="http://exslt.org/dates-and-times" >

<xsl:template name="lf">
    <xsl:text/>
</xsl:template>

<xsl:template match="rss">
    <section id="campusEvents" role="region">
        <h2 id="eventsTitle">
            <a href="http://calendar.test.edu/">Campus Events</a>
        </h2>
       <xsl:apply-templates select="channel"/>
        <div class="moreLink">
            <a href="http://calendar.test.edu/">Full Calendar</a>
        </div>
    </section>
</xsl:template>

<xsl:template match="channel">
        <xsl:variable name="currDay" select="substring(date:date(),9,2)"/>
        <xsl:variable name="currMonth">
            <xsl:call-template name="format-month">
                <xsl:with-param name="date" select="date:date()"/>
            </xsl:call-template>
        </xsl:variable>
        <xsl:variable name="currYear" select="substring(date:date(),1,4)"/>
        <xsl:variable name="current" select="concat($currDay,' ',$currMonth,' ',$currYear )"/>

  <xsl:for-each select="item[not(position() &gt; 4)] and substring(item/pubDate,5,11) &gt;= $current">
        <div class="eventBlock">
            <xsl:call-template name="lf"/>
            <div class="dateBlock">
                <xsl:call-template name="lf"/>
                <div class="eventMonth">
                    <xsl:value-of select="substring(pubDate,8,3)"/>
                </div>
                <div class="eventDate">
                    <xsl:value-of select="substring(pubDate,5,2)"/>
                </div>
            </div>
            <xsl:call-template name="lf"/>
            <div class="eventDescription">
                <a class="url" href="{link}">
                <xsl:value-of select="title"/>
                </a>
                <xsl:call-template name="lf"/>
            </div>
            <xsl:call-template name="lf"/>
        </div>
        <xsl:call-template name="lf"/>
        </xsl:for-each>
</xsl:template>

   <xsl:template name="format-month">
    <xsl:param name="date"/>
    <xsl:variable name="monthName" select="substring(date:date(),6,2)"/>
    <xsl:variable name="month">
        <xsl:choose>
            <xsl:when test="$monthName = '01'">Jan</xsl:when>
            <xsl:when test="$monthName = '02'">Feb</xsl:when>
            <xsl:when test="$monthName = '03'">Mar</xsl:when>
            <xsl:when test="$monthName = '04'">Apr</xsl:when>
            <xsl:when test="$monthName = '05'">May</xsl:when>
            <xsl:when test="$monthName = '06'">Jun</xsl:when>
            <xsl:when test="$monthName = '07'">Jul</xsl:when>
            <xsl:when test="$monthName = '08'">Aug</xsl:when>
            <xsl:when test="$monthName = '09'">Sep</xsl:when>
            <xsl:when test="$monthName = '10'">Oct</xsl:when>
            <xsl:when test="$monthName = '11'">Nov</xsl:when>
            <xsl:when test="$monthName = '12'">Dec</xsl:when>
            <xsl:otherwise/>
        </xsl:choose>
    </xsl:variable>
    <xsl:value-of select="$month"/>
</xsl:template>

</xsl:stylesheet>

Desired Result (after Oct. 30 event has expired):

<section role="region" id="campusEvents">
  <h2 id="eventsTitle">
    <a href="http://calendar.test.edu/">Campus Events</a>
  </h2>
 <div class="eventBlock">
    <div class="dateBlock">
        <div class="eventMonth">Nov</div>
        <div class="eventDate">04</div>
    </div>
    <div class="eventDescription">
        <a href="http://calendar.example.edu/?&amp;y=2013&amp;m=11&amp;d=04&amp;eventdatetime_id=16427" class="url">Philosophy Career Fair</a>
    </div>
</div>
  <div class="eventBlock">
    <div class="dateBlock">
        <div class="eventMonth">Dec</div>
        <div class="eventDate">07</div>
    </div>
    <div class="eventDescription">
        <a href="http://calendar.example.edu/?&amp;y=2013&amp;m=12&amp;d=07&amp;eventdatetime_id=16521" class="url">Football vs. Caltech</a>
    </div>
  </div>
  <div class="eventBlock">
    <div class="dateBlock">
        <div class="eventMonth">Jan</div>
        <div class="eventDate">14</div>
    </div>
    <div class="eventDescription">
        <a href="http://calendar.example.edu/?&amp;y=2014&amp;m=01&amp;d=14&amp;eventdatetime_id=16759" class="url">Mural Exhibition</a>
    </div>
  </div>
  <div class="moreLink">
    <a href="http://calendar.test.edu/">Full Calendar</a>
  </div>
</section>
1
xsltxpathrssxslt-1.0

1 Answers

2
votes

If you want to compare dates then you'll have to somehow massage the various date expressions into all-numeric yyyymmdd format (e.g. 20131029) so that the chronological ordering is equivalent to numerical ordering. For the current date that's a simple global variable:

<xsl:variable name="curDateStr" select="date:date()" />
<xsl:variable name="currentDateNum"
   select="concat(substring($curDateStr, 1, 4),
                  substring($curDateStr, 6, 2),
                  substring($curDateStr, 9, 2))" />

and to parse the pubDate values I'd use a named template that's the reverse of your current format-month

<xsl:template name="parse-date">
  <xsl:param name="dateStr" />
  <xsl:value-of select="substring($dateStr, 12, 4)" /><!-- year -->
  <xsl:variable name="month" select="substring($dateStr, 8, 3)" />
  <xsl:choose>
    <xsl:when test="$month = 'Jan'">01</xsl:when>
    <xsl:when test="$month = 'Feb'">02</xsl:when>
    <!-- etc. -->
  </xsl:choose>
  <xsl:value-of select="substring($dateStr, 5, 2)" /><!-- day -->
</xsl:template>

Now the main logic can be implemented using a tail-recursive template which is the nearest you can get in XSLT to a "while" loop:

<xsl:template match="item">
  <xsl:param name="numItems" select="3" />
  <xsl:if test="$numItems &gt; 0"><!-- stop if we hit the threshold -->
    <xsl:variable name="itemDate">
      <xsl:call-template name="parse-date">
        <xsl:with-param name="dateStr" select="pubDate" />
      </xsl:call-template>
    </xsl:variable>
    <xsl:choose>
     <xsl:when test="$itemDate &gt; $currentDateNum">
        <!-- do what you need to do to produce output for this item -->
        <!-- ..... -->
        <xsl:apply-templates select="following-sibling::item[1]">
          <!-- we processed this item, so decrement $numItems -->
          <xsl:with-param name="numItems" select="$numItems - 1" />
        </xsl:apply-templates>
      </xsl:when>
      <xsl:otherwise>
        <xsl:apply-templates select="following-sibling::item[1]">
          <!-- we ignored this item, so don't decrement $numItems -->
          <xsl:with-param name="numItems" select="$numItems" />
        </xsl:apply-templates>
      </xsl:otherwise>
    </xsl:choose>
  <xsl:if>
</xsl:template>

and then in the channel template you start this "loop" by applying templates to the first item only

<xsl:template match="channel">
  <xsl:apply-templates select="item[1]" />
</xsl:template>

The item template will then keep processing siblings until either it runs out of item elements completely, or it has processed 3 items that meet the date criteria.