Show differences in a text file between two XML files with XSLT1.0

The opening file is file1 which is composed of a lot of network nodes with their children nodes.

Sometimes, the user can change something in the file1, either a value either add a new key and so a new value. The modification are so saved in a new file, file2.

What I would like to do, see the exemple, is :

1°) Check if, in the file2, there is new Keys and so new values or if keys have been deleted.

2°) Check, for each Key, if the value has changed.

3°) Point out the difference in a text file with, for each shift, the top parent node.

File 1

 <node>
    <node key="Network1">
      <node key="@IP" value="65.12.30.20"/>
      <node key="@MAC" value="62-42-85-74-21"/>
      <node key="PortNumber" value="12000"/>
      <node key="Location">
          <node key="House" value="Blue"/>
          <node key="Room" value="Green"/>
          <node key="Office" value="IT"/>
      </node>
     </node>
    
    <node key="Network2">
      <node key="@IP" value="15.58.12.36"/>
      <node key="@MAC" value="85-02-14-52-12"/>
      <node key="PortNumber" value="12000"/>
      <node key="Location">
          <node key="House" value="Blue"/>
          <node key="Room" value="Yellow"/>
          <node key="Office" value="IT"/>
       </node>
       </node>
 </node> 

File 2

<node>
<node key="Network1">
  <node key="@IP" value="65.12.30.20"/>
  <node key="@MAC" value="62-42-85-74-21"/>
  <node key="PortNumber" value="12001"/>
  <node key="Location">
      <node key="House" value="Blue"/>
      <node key="Room" value="Green"/>
      <node key="Office" value="HR"/>
      <node key="Rack" value="2"/>
   </node>
</node>

<node key="Network2">
  <node key="@IP" value="15.58.12.36"/>
  <node key="@MAC" value="14-85-13-74-36"/>
  <node key="PortNumber" value="12001"/>
  <node key="Location">
      <node key="House" value="Blue"/>
      <node key="Room" value="Yellow"/>
      <node key="Office" value="IT"/>
      <node key="Rack" value="1"/>
    </node>
  </node>
</node>

So, I would like to point out the differences.

@EDIT

With the solution proposed, I've found a bug with this example.

<stackoverflow12>
	<node key="Test">
		<node key="keyA">
			<node key="A" value="A1">
				<node key="Name" value="Tim" />
			</node>
			<node key="A" value="A2">
				<node key="Name" value="Tom" />
			</node>
		</node>
	</node>
	
	<node key="Test">
		<node key="keyA">
			<node key="A" value="A1">
				<node key="Name" value="Tim" />
			</node>
			<node key="A" value="A2">
				<node key="Name" value="Tom" />
			</node>
		</node>
	</node>
</stackoverflow12>

The two XML Files are the same but the XSLT code get :

<?xml version="1.0" encoding="UTF-8"?>
<node key="Test">
    <node key="keyA">
        <node key="A" left-value="A1" right-value="A1"/>
        <node key="A" left-value="A2" right-value="A1"/>
    </node>
</node>

What's the problem with the code ?

Your desired output consists of two files that lack the closing tags demanded by the XML syntax. Rather than create that directly, I suggest creating an "intermediate" XML file that contains nodes with a left-value and a right-value if the value differs between the two input files and a left-node or right-node if the key exists only in one file. The following stylesheet computes such an intermediate XML file recursively. It would produce superfluous nodes like <node key="..."> for every node with children that is the same in the two input files (which does not occur in your example). These can be removed with a second pass or simply skipped over when the intermediate format is converted into your desired output.

The stylesheet expects a single XML input that combines both your input files like so:

<stackoverflow-75629991>
  <node>
    <!-- File 1 -->
  </node>
  <node>
    <!-- File 2 -->
  </node>
</stackoverflow-75629991>

Here is the stylesheet:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes" />
  <xsl:template match="/*">
    <xsl:apply-templates select="node[1]">
      <xsl:with-param name="others" select="node[2]" />
    </xsl:apply-templates>
  </xsl:template>
  <xsl:template match="node">
    <xsl:param name="others" />
    <xsl:variable name="other" select="$others[not(@key) or @key=current()/@key]" />
    <xsl:choose>
      <xsl:when test="@value != $other/@value">
        <node key="{@key}" left-value="{@value}" right-value="{$other/@value}" />
      </xsl:when>
      <xsl:when test="$other and not(@value)">
        <node>
          <xsl:copy-of select="@key" />
          <xsl:apply-templates select="node">
            <xsl:with-param name="others" select="$other/node" />
          </xsl:apply-templates>
          <xsl:for-each select="$other/node[not(@key=current()/node/@key)]">
            <right-node>
              <xsl:copy-of select="@key | @value | node"/>
            </right-node>
          </xsl:for-each>
        </node>
      </xsl:when>
      <xsl:when test="not($other)">
        <left-node>
          <xsl:copy-of select="@key | @value | node"/>
        </left-node>
      </xsl:when>
    </xsl:choose>
  </xsl:template>
</xsl:stylesheet>

And here is the intermediate XML file it produces as output:

<node>
   <node key="Network1">
      <node key="PortNumber" left-value="12000" right-value="12001"/>
      <node key="Location">
         <node key="Office" left-value="IT" right-value="HR"/>
         <right-node key="Rack" value="2"/>
      </node>
   </node>
   <node key="Network2">
      <node key="@MAC" left-value="85-02-14-52-12" right-value="14-85-13-74-36"/>
      <node key="PortNumber" left-value="12000" right-value="12001"/>
      <node key="Location">
         <right-node key="Rack" value="1"/>
      </node>
   </node>
</node>