Expanding datetime ranges in XSLT 1.0

Question

I have an XML feed of events whose dates I would like to interact with.

Source XML:

<?xml version="1.0" encoding="UTF-8"?>
<events>
  <event>
    <!-- various elements -->
    <start_datetime value="2012-02-09 10:00:00"/>
    <end_datetime value="2012-02-09 11:00:00"/>
    <!-- various elements -->
  </event>
  <event>
    <!-- various elements -->
    <start_datetime value="2012-02-09 10:00:00"/>
    <end_datetime value="2012-02-10 15:00:00"/>
    <!-- various elements -->
  </event>
  <!-- other events -->
</events>

Notice that /events/event[1] is an event that starts and ends on the same day; /events/event[2], on the other hand, spans two days. Here's what I would like to accomplish:

1. For events that are on the same day, leave the datetimes alone and merely transform those attributes into child elements.
2. For events that span multiple days, I want to create multiple <event> elements that (a) match the overall span of time and (b) where appropriate, span a full day's worth of time.

So, my ideal XSLT would produce:

Desired XML:

<?xml version="1.0" encoding="UTF-8"?>
<events>
  <event>
    <!-- various elements -->
    <start_datetime>2012-02-09 10:00:00</start_datetime>
    <end_datetime>2012-02-09 11:00:00</end_datetime>
    <!-- various elements -->
  </event>
  <event>
    <!-- various elements -->
    <start_datetime>2012-02-09 10:00:00</start_datetime>
    <end_datetime>2012-02-09 23:59:59</end_datetime>
    <!-- various elements -->
  </event>
  <event>
    <!-- various elements -->
    <start_datetime>2012-02-10 00:00:00</start_datetime>
    <end_datetime>2012-02-10 15:00:00</end_datetime>
    <!-- various elements -->
  </event>
  <!-- other events -->
</events>

Notice how my rules are met:

• Because /events/event[1] occurs over the same day, we leave it alone (other than the trivial task of changing attribute values into child elements).
• /events/event[2] spans two days, which means it needs two <event> blocks (one from the starting datetime to 11:59:59pm on that date and one from 00:00:00 on the ending date to the ending datetime).

Final Considerations:

• This needs to be accomplished in XSLT 1.0.

• I am not opposed to using EXSLT's date functions - however, if they can be avoided, that would be preferable.

Clear as mud? As always, thanks for your help. :)

Answer 1

Here is an XSLT 1.0 solution, that doesn't use EXSLT date functions, but which makes use of a named template to add one to a given date, using string manipulation functions to extra the year, month and day from a date string

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
   <xsl:output method="xml" indent="yes"/>

   <xsl:template match="@*|node()">
      <xsl:copy>
         <xsl:apply-templates select="@*|node()"/>
      </xsl:copy>
   </xsl:template>

   <xsl:template match="event" name="event">
      <xsl:param name="start_datetime" select="start_datetime/@value"/>
      <xsl:variable name="end_datetime" select="end_datetime/@value"/>
      <event>
         <xsl:apply-templates select="start_datetime/preceding-sibling::node()"/>
         <start_datetime>
            <xsl:value-of select="$start_datetime"/>
         </start_datetime>
         <end_datetime>
            <xsl:choose>
               <xsl:when test="substring($start_datetime, 1, 10) = substring($end_datetime ,1, 10)">
                  <xsl:value-of select="$end_datetime"/>
               </xsl:when>
               <xsl:otherwise>
                  <xsl:value-of select="concat(substring($start_datetime, 1, 10), ' 23:59:59')"/>
               </xsl:otherwise>
            </xsl:choose>
         </end_datetime>
         <xsl:apply-templates select="end_datetime/following-sibling::node()"/>
      </event>
      <xsl:if test="substring($start_datetime, 1, 10) != substring($end_datetime ,1, 10)">
         <xsl:call-template name="event">
            <xsl:with-param name="start_datetime">
               <xsl:call-template name="addOneToDate">
                  <xsl:with-param name="date" select="$start_datetime"/>
               </xsl:call-template>
            </xsl:with-param>
         </xsl:call-template>
      </xsl:if>
   </xsl:template>

   <xsl:template name="addOneToDate">
      <xsl:param name="date"/>
      <xsl:variable name="year" select="number(substring($date, 1, 4))"/>
      <xsl:variable name="month" select="number(substring($date, 6, 2))"/>
      <xsl:variable name="day" select="number(substring($date, 9, 2))"/>
      <xsl:variable name="daysInMonth">
         <xsl:choose>
            <xsl:when test="$month = 2">
               <xsl:choose>
                  <xsl:when test="($year div 4 = 0 and $year div 100 != 0) or ($year div 400 = 0)">29</xsl:when>
                  <xsl:otherwise>28</xsl:otherwise>
               </xsl:choose>
            </xsl:when>
            <xsl:when test="$month = 4 or $month = 6 or $month = 9 or $month = 11">30</xsl:when>
            <xsl:otherwise>31</xsl:otherwise>
         </xsl:choose>
      </xsl:variable>
      <xsl:choose>
         <xsl:when test="$day != $daysInMonth">
            <xsl:value-of select="concat($year, '-', format-number($month, '00'), '-', format-number($day + 1, '00'), ' 00:00:00')"/>
         </xsl:when>
         <xsl:when test="$month = 12">
            <xsl:value-of select="concat($year + 1, '-01-01 00:00:00')"/>
         </xsl:when>
         <xsl:otherwise>
            <xsl:value-of select="concat($year, '-', format-number($month + 1, '00'), '-01 00:00:00')"/>
         </xsl:otherwise>
      </xsl:choose>
   </xsl:template>
</xsl:stylesheet>

When applied to your sample XML, the following is output

<events>
   <event>
      <!-- various elements -->
      <start_datetime>2012-02-09 10:00:00</start_datetime>
      <end_datetime>2012-02-09 11:00:00</end_datetime>
      <!-- various elements -->
   </event>
   <event>
      <!-- various elements -->
      <start_datetime>2012-02-09 10:00:00</start_datetime>
      <end_datetime>2012-02-09 23:59:59</end_datetime>
      <!-- various elements -->
   </event>
   <event>
      <!-- various elements -->
      <start_datetime>2012-02-10 00:00:00</start_datetime>
      <end_datetime>2012-02-10 15:00:00</end_datetime>
      <!-- various elements -->
   </event>
   <!-- other events -->
</events>

I am sure you would agree using EXSLT would be simpler....