class KramdownRFC::ParameterSet

def [](pn)
  @f.delete(pn.to_s)
end

def []=(pn, val)
  @f[pn] = val
end

def arr(an, converthash=true, must_have_one=false, &block)
  arr = self[an] || []
  arr = [arr] if Hash === arr && converthash
  arr << { } if must_have_one && arr.empty?
  Array(arr).each(&block)
end

def attr(pn)
  val, an = van(pn)
  @av[an.intern] = val
  %{#{an}="#{escattr(val)}"}    if val
end

def attrs(*pns)
  pns.map{ |pn| attr(pn) if pn }.compact.join(" ")
end

def ele(pn, attr=nil, defcontent=nil, markdown=false)
  val, an = van(pn)
  val ||= defcontent
  val = [val] if Hash === val
  Array(val).map do |val1|
    a = Array(attr).dup
    if Hash === val1
      val1.each do |k, v|
        if k == ":"
          val1 = v
        else
          k = Kramdown::Element.attrmangle(k) || k
          a.unshift(%{#{k}="#{escattr(v)}"})
        end
      end
    end
    v = val1.to_s.strip
    contents =
      if markdown
        ::Kramdown::Converter::Rfc2629::process_markdown(v)
      else
        escape_html(v)
      end
    %{<#{[an, *a.map(&:to_s)].join(" ").strip}>#{contents}</#{an}>}
  end.join(" ")
end

def escattr(str)
  escape_html(str.to_s, :attribute)
end

def has(pn)
  @f[pn.to_s]
end

def initialize(y)
  raise "*** invalid parameter set #{y.inspect}" unless Hash === y
  @f = y
  @av = {}
end

def rest
  @f
end

def van(pn)                   # pn is a parameter name, possibly with an =alias
  an, pn = pn.to_s.split("=")
  pn ||= an
  [self[pn] || self[an], an]
end

def warn_if_leftovers
  if !@f.empty?
    warn "*** attributes left #{@f.inspect}!"
  end
end