class Nokogiri::XML::Node

def diff(other,options={},&block)
  return enum_for(__method__,other,options) unless block
  if (options[:added] || options[:removed])
    tdiff_unordered(other) do |change,node|
      if    (change == '+' && options[:added])   then yield change, node
      elsif (change == '-' && options[:removed]) then yield change, node
      end
    end
  else
    tdiff(other,&block)
  end
end

def tdiff_each_child(node,&block)
  if node.kind_of?(Nokogiri::XML::Element)
    node.attribute_nodes.sort_by(&:name).each(&block)
  end
  node.children.each(&block)
end

def tdiff_equal(node)
  if (self.class == node.class)
    case node
    when Nokogiri::XML::Attr
      (self.name == node.name && self.value == node.value)
    when Nokogiri::XML::Element, Nokogiri::XML::DTD
      self.name == node.name
    when Nokogiri::XML::Text, Nokogiri::XML::Comment
      self.text == node.text
    when Nokogiri::XML::ProcessingInstruction
      (self.name == node.name && self.content == node.content)
    else
      false
    end
  else
    false
  end
end