How can I determine if an XML node has a last ancestor that does `not` have a certain attribute?

Any  tag within the <body> tags should be transformed to Body_Text.
The  tags that have a last ancestor <sec> without the attribute "sec-type" should be transformed to Flush_Text (which overrides the first Body_Text transformation here).
The  tags that have a last ancestor <sec sec-type="irrelevant-attribute-name> (with the attribute "sec-type") should be transformed to Body_Text.

<sec>asdf</sec> should be transformed into <sec><Flush_Text>asdf</Flush_Text></sec>.

<sec sec-type="whatevs">asdf</sec> should be <sec sec-type="whatevs"><Body_Text>asdf</Body_Text></sec>.

Also, any further nesting into an ancestor with this sec-type attribute should still be Body_Text:

<sec sec-type="whatevs"><sec>asdf</sec></sec> should be <sec sec-type="whatevs"><sec><Body_Text>asdf</Body_Text></sec>.

Here is my XML:

<root>
  <body>
  <sec sec-type="asdf">
    <title>This is an H1</title>

    <sec>
      <title>This is an H2</title>

      <sec>
        <title>This is an H3</title>
        <p>This SHOULD be "Body_Text", but it's "Flush_Text"</p>
      </sec> <!-- end of H3 -->
    </sec> <!-- end of H2 -->
  </sec> <!-- end of H1 -->

  <sec>
    <p>This is Flush_Text</p>
  </sec>
    <p>This is Body_Text</p>
  </body>
</root>

...here is my XSL, which is not working correctly:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes" method="xml"/>
<xsl:strip-space elements="*"/>

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

        <!-- Body_Text -->
        <xsl:template match="body//p">
            <Body_Text>
                <xsl:apply-templates select="@*|node()"/>
            </Body_Text>
        </xsl:template>

        <!-- Flush_Text -->
        <xsl:template match="sec//p">
          <xsl:if test="not(@sec-type)">
            <Flush_Text>
                <xsl:apply-templates select="@*|node()"/>
            </Flush_Text>
          </xsl:if>
        </xsl:template>

        <!-- H1 -->
        <xsl:template match="sec//title">
            <H1>
                <xsl:apply-templates select="@*|node()"/>
            </H1>
        </xsl:template>

        <!-- H2 -->
        <xsl:template match="sec//sec//title">
            <H2>
                <xsl:apply-templates select="@*|node()"/>
            </H2>
        </xsl:template>

        <!-- H3 -->
        <xsl:template match="sec//sec//sec//title">
            <H3>
                <xsl:apply-templates select="@*|node()"/>
            </H3>
        </xsl:template>
</xsl:stylesheet>

...and here is the incorrect output:

<?xml version="1.0" encoding="utf-16"?>
<root>
    <body>
        <sec sec-type="asdf">
            <H1>This is an H1</H1>
            <sec>
                <H2>This is an H2</H2>
                <sec>
                    <H3>This is an H3</H3>
                    <Flush_Text>This SHOULD be "Body_Text", but it's "Flush_Text"</Flush_Text>
                </sec>
                <!-- end of H3 -->
            </sec>
            <!-- end of H2 -->
        </sec>
        <!-- end of H1 -->
        <sec>
            <Flush_Text>This is Flush_Text</Flush_Text>
        </sec>
        <Body_Text>This is Body_Text</Body_Text>
    </body>
</root>

Note that the first instance of  in this example should be transformed to Body_Text, but it is being transformed as Flush_Text.

Solution

Ok, so to produce the wanted results here, I have changed the statement <xsl:template match="sec//p"> (in the XSL under Flush_Text) to <xsl:template match="p[ancestor::sec[last()][not(@sec-type)]]">, and also removed the if statement.

Here is the corrected XSL:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes" method="xml"/>
<xsl:strip-space elements="*"/>

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

        <!-- Body_Text -->
        <xsl:template match="body//p">
            <Body_Text>
                <xsl:apply-templates select="@*|node()"/>
            </Body_Text>
        </xsl:template>

    <!-- Flush_Text -->
    <xsl:template match="p[ancestor::sec[last()][not(@sec-type)]]">
        <Flush_Text>
            <xsl:apply-templates select="@*|node()"/>
        </Flush_Text>
    </xsl:template>

        <!-- H1 -->
        <xsl:template match="sec//title">
            <H1>
                <xsl:apply-templates select="@*|node()"/>
            </H1>
        </xsl:template>

        <!-- H2 -->
        <xsl:template match="sec//sec//title">
            <H2>
                <xsl:apply-templates select="@*|node()"/>
            </H2>
        </xsl:template>

        <!-- H3 -->
        <xsl:template match="sec//sec//sec//title">
            <H3>
                <xsl:apply-templates select="@*|node()"/>
            </H3>
        </xsl:template>
</xsl:stylesheet>

...producing this desired output:

<root>
<body>
<sec sec-type="asdf">
<H1>This is an H1</H1>
<sec>
<H2>This is an H2</H2>
<sec>
<H3>This is an H3</H3>
<Body_Text>This SHOULD be "Body_Text", but it's "Flush_Text"</Body_Text>
</sec>

</sec>

</sec>

<sec>
<Flush_Text>This is Flush_Text</Flush_Text>
</sec>
<Body_Text>This is Body_Text</Body_Text>
</body>
</root>

this was tested at: http://xslt.online-toolz.com/tools/xslt-transformation.php.

Thanks @Tomalak for pointing me in the right direction in the use of the ancestor xpath axis.

Here I have matched the last ancestor (what I was incorrectly calling the "highest parent") <sec> from any  that does not have the attribute sec-type, and transformating that as Flush_Text. This is preventing the first instance of  in this example, that has <sec sec-type... as its' last ancestor, from being Flush_Text and allows the Body_Text to override.

Also, I like Tomalak's use of automating H1 - H3... I am still experimenting with this, and don't want to use it until I fully understand it ;)