global

def boilerplate(key)
  case key.downcase
  when /\Abcp14(info)?(\+)?(-tagged)?\z/i
    ret = ''
    if $1
      ret << <<RFC8174ise
Although this document is not an IETF Standards Track publication, it
adopts the conventions for normative language to provide clarity of
instructions to the implementer.
RFC8174ise
    end
    ret << <<RFC8174
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
"MAY", and "OPTIONAL" in this document are to be interpreted as
described in BCP 14 {{!RFC2119}} {{!RFC8174}} when, and only when, they
appear in all capitals, as shown here.
RFC8174
    if $2
      ret << <<PLUS
These words may also appear in this document in
lower case as plain English words, absent their normative meanings.
PLUS
    end
    if $3
      ($options.v3_used ||= []) << "** need --v3 to tag bcp14"
      ret << <<TAGGED

*[MUST]: <bcp14>
*[MUST NOT]: <bcp14>
*[REQUIRED]: <bcp14>
*[SHALL]: <bcp14>
*[SHALL NOT]: <bcp14>
*[SHOULD]: <bcp14>
*[SHOULD NOT]: <bcp14>
*[RECOMMENDED]: <bcp14>
*[NOT RECOMMENDED]: <bcp14>
*[MAY]: <bcp14>
*[OPTIONAL]: <bcp14>
TAGGED
    end
    ret
  else
    warn "** Unknwon boilerplate key: #{key}"
    "{::boilerplate #{key}}"
  end
end