parse csv to xml

#!/usr/bin/env ruby
require 'rexml/document'

source = 'root,ELEM,a,name,a1,ATTR,b,bbb1,ATTR,b,bbb2,ELEM,a2'
elems = source.split /,/
doc = REXML::Document.new "<#{elems.shift}/>"
elems.slice_before {|e| e == 'ELEM' }.each do |e|
  e.shift # delete 'ELEM'
  a = REXML::Element.new e.shift
  e.slice_before {|ee| ee == 'ATTR' }.each do |ee|
    if ee.first != 'ATTR'
      ee.each_slice(2) do |eee|
        if eee.size == 1
          a.text, = eee
        else
          a.add_attribute *eee
        end
      end
    else
      ee.shift # delete 'ATTR'
      b = REXML::Element.new ee.shift
      ee.each_slice(2) do |eee|
        if eee.size == 1
          b.text, = eee
        else
          b.add_attribute *eee
        end
      end
      a.elements << b
    end
  end
  doc.root << a
end
open('hoge.xml', 'w') {|f| doc.write f, 2; f.puts }