<?xml version='1.0'?>

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Copyright (C) 2014-2026  Robert A. Beezer

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<!-- This stylesheet locates video/@youtube elements and -->
<!-- prepares a Python dictionary necessary to extract a -->
<!-- thumbnail for each video from the YouTube servers   -->

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"
    xmlns:xml="http://www.w3.org/XML/1998/namespace"
    xmlns:exsl="http://exslt.org/common"
    xmlns:str="http://exslt.org/strings"
    extension-element-prefixes="exsl"
>

<!-- Get internal ID's for filenames, etc -->
<!-- Standard conversion groundwork       -->
<xsl:import href="./publisher-variables.xsl"/>
<xsl:import href="./pretext-assembly.xsl"/>
<xsl:import href="./pretext-common.xsl"/>

<!-- Get a "subtree" xml:id value   -->
<!-- Then walk the XML source tree  -->
<!-- applying specializations below -->
<xsl:import href="./extract-identity.xsl" />

<xsl:output method="text" encoding="UTF-8"/>

<!-- Avoid Catch-22: default assembly/pre-processor providews output     -->
<!-- for a conversion to a static format, but that format will *replace* -->
<!-- "video" by a static version (a "sidebyside") and it will not be     -->
<!-- available for extraction.                                           -->
<xsl:variable name="exercise-style" select="'dynamic'"/>

<!-- YouTube ID, and internal id as a comma-separated pair per line -->
<xsl:template match="video[@youtube and not(@preview)]" mode="extraction">
    <!-- replace commas with spaces, then normalize space,                       -->
    <!-- then tack on a space at the end, then grab content prior to first space -->
    <xsl:variable name="first-video-id" select="substring-before(concat(normalize-space(str:replace(@youtube, ',', ' ')), ' '), ' ')" />
    <xsl:value-of select="$first-video-id" />
    <xsl:text>,</xsl:text>
    <xsl:apply-templates select="." mode="unique-id" />
    <xsl:text>&#xa;</xsl:text>
</xsl:template>

</xsl:stylesheet>
