XSL : Replace value inside tag - xslt

Question

Input:
<Remarks>Random data## B2B## abc,controls,free text ## B2B## random data</Remarks>
The XSL should replace
"## B2B## abc,controls,free text ## B2B##"
in the Remarks tag with
"value1:abc,value2:controls,value3:free text"
Desired output:
<Remarks>Random data,value1:abc,value2:controls,value3:free text,random data</Remarks>
Note : the values inside ## B2B## tags are unknown and change everytime, for now I gave the sample values.

Answer 1

Assuming there will always be exactly one "placeholder" delimited by ## B2B##, and that it will always contain exactly 3 comma-delimited "tokens", you could do this quite simply by:
<xsl:template match="Remarks">
<xsl:copy>
<xsl:value-of select="substring-before(., '## B2B##')" />
<xsl:variable name="placeholder" select="substring-before(substring-after(., '## B2B##'), '## B2B##')" />
<xsl:text> value1: </xsl:text>
<xsl:value-of select="substring-before($placeholder, ',')" />
<xsl:text> value2: </xsl:text>
<xsl:value-of select="substring-before(substring-after($placeholder, ','), ',')" />
<xsl:text> value3: </xsl:text>
<xsl:value-of select="substring-after(substring-after($placeholder, ','), ',')" />
<xsl:value-of select="substring-after(substring-after(., '## B2B##'), '## B2B##')" />
</xsl:copy>
</xsl:template>

Answer 2

This solution is somewhat complex. It uses one template to extract the string between the tags and another to separate this string by the delimiter. What string is replaced by what other string is outsourced to another file containing the mapping (replacement.xml). Because XSLT-1.0 returns RTFs(Resulting Tree Fragments) in variables, the replacement is hardcoded in the template. In XSLT-2.0 you could use a variable for that making the solution more flexible.
Here is the replacement.xml containing the mappings:
<?xml version="1.0" encoding="UTF-8"?>
<replacement>
<r src="abc">value1</r>
<r src="controls">value2</r>
<r src="free text">value3</r>
</replacement>
And the XSLT incorporating these mappings into the string:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" indent="yes"/>
<xsl:template match="/lines/Remarks">
<xsl:variable name="tagName" select="'## B2B##'" />
<xsl:variable name="subStrToReplace">
<xsl:call-template name="strInTag">
<xsl:with-param name="str" select="text()" />
<xsl:with-param name="tagName" select="$tagName" />
</xsl:call-template>
</xsl:variable>
<xsl:variable name="replacementString">
<xsl:call-template name="splitAndReplace">
<xsl:with-param name="pText" select="$subStrToReplace" />
</xsl:call-template>
</xsl:variable>
<Remarks>
<xsl:value-of select="concat(normalize-space(substring-before(text(),$tagName)), ',',$replacementString, normalize-space(substring-after(substring-after(text(),$tagName),$tagName)))" />
</Remarks>
</xsl:template>
<xsl:template name="strInTag">
<xsl:param name="str" />
<xsl:param name="tagName" />
<xsl:value-of select="normalize-space(substring-before(substring-after($str,$tagName),$tagName))" />
</xsl:template>
<xsl:template name="splitAndReplace">
<xsl:param name="pText"/>
<xsl:if test="string-length($pText) > 0">
<xsl:variable name="vNextItem" select="substring-before(concat($pText, ','), ',')"/>
<xsl:value-of select="concat($vNextItem,':',document('replacement.xml')/replacement/r[#src = $vNextItem]/text(),',')"/>
<xsl:call-template name="splitAndReplace">
<xsl:with-param name="pText" select="substring-after($pText, ',')"/>
</xsl:call-template>
</xsl:if>
</xsl:template>
</xsl:stylesheet>