"how to convert html to bbcode" Code Answer

It should be doable with XSLT in text output mode:

<xsl:output method="text">
…
<xsl:template match="b|strong"><xsl:apply-templates/></xsl:template>
<xsl:template match="br">&#10;</xsl:template>
<xsl:template match="p">&#10;<xsl:apply-templates/>&#10;</xsl:template>
<xsl:template match="a"><xsl:apply-templates/></xsl:template>
<xsl:template match="text()"><x:value-of select="normalize-space(.)"/></xsl:template>

To get there parse HTML and use built-in XSLT processor.