class Sanitize

def clean_element!(node)
  # Run this node through all configured transformers.
  transform = transform_element!(node)
  # If this node is in the dynamic whitelist array (built at runtime by
  # transformers), let it live with all of its attributes intact.
  return if @whitelist_nodes.include?(node)
  name = node.name.to_s.downcase
  # Delete any element that isn't in the whitelist.
  unless transform[:whitelist] || @config[:elements].include?(name)
    unless @config[:remove_contents]
      node.children.each { |n| node.add_previous_sibling(n) }
    end
    node.unlink
    return
  end
  attr_whitelist = (transform[:attr_whitelist] +
      (@config[:attributes][name] || []) +
      (@config[:attributes][:all] || [])).uniq
  if attr_whitelist.empty?
    # Delete all attributes from elements with no whitelisted attributes.
    node.attribute_nodes.each {|attr| attr.remove }
  else
    # Delete any attribute that isn't in the whitelist for this element.
    node.attribute_nodes.each do |attr|
      attr.unlink unless attr_whitelist.include?(attr.name.downcase)
    end
    # Delete remaining attributes that use unacceptable protocols.
    if @config[:protocols].has_key?(name)
      protocol = @config[:protocols][name]
      node.attribute_nodes.each do |attr|
        attr_name = attr.name.downcase
        next false unless protocol.has_key?(attr_name)
        del = if attr.value.to_s.downcase =~ REGEX_PROTOCOL
          !protocol[attr_name].include?($1.downcase)
        else
          !protocol[attr_name].include?(:relative)
        end
        attr.unlink if del
      end
    end
  end
  # Add required attributes.
  if @config[:add_attributes].has_key?(name)
    @config[:add_attributes][name].each do |key, val|
      node[key] = val
    end
  end
  transform
end