def tag(type, body, args = {})
  if args[:style].is_a? Hash
    args[:style] = args[:style].map { |k, v| "#{k}: #{v};" }.join(" ")
  end
  "<#{type} #{args.map { |k, v| "#{k}='#{v}'" }.join(" ")}>#{body}</#{type}>"
end

def data_table(schema, data, params = {})
  tablename_style  = params.fetch(:tablename_style, { "font-weight" => "bold", "text-decoration" => "underline" })
  rownum_style     = params.fetch(:rownum_style, { "font-size" => "50%", "font-face" => "Courier, fixed-width", "vertical-align"=> "middle" })
  annotation_style = params.fetch(:annotation_style, rownum_style)
  separator_style  = params.fetch(:separator_style, { "border-right" => "1px solid black" })

  num_cols = data.map { |row| row.size if row.is_a? Array }.compact.max

  data = data.map do |row| 
    case row
    when Array
      row.map do |cell| 
        tag("td", cell) 
      end
    when String
      [ tag("td", row, colspan: num_cols) ]
    else
      raise "Unknown rowtype: #{row}"
    end
  end
  if params.has_key? :annotations
    data = data.zip(params[:annotations]).map do |row, annot| 
        if annot.nil? then row
        else row+[tag("td", "→ "+annot.to_s, annotation_style)] end
      end
    num_cols += 1
  end

  data = [schema.map { |cell| tag("th", cell) }] + data
  if params.fetch(:rowids, false)
    data = data.map.with_index do |row, idx| 
      if idx == 0 then [tag("th", "#", style: separator_style)]+row
      else [tag("td", idx+params.fetch(:rowid_offset, 0), style: rownum_style.merge(separator_style))]+row
      end
    end
  elsif params.has_key? :name
    data = data.map { |row| [tag("td", "", style: separator_style)]+row }
  end
  if params.has_key? :name
    data[0][0] = tag("th", params[:name], style: tablename_style.merge(separator_style))
  end

  row_args = [{}] * data.size
  case params.fetch(:build_in, :none)
  when :none then 
  when :by_row then row_args = [{}] + [{ "class" => "fragment" }]*(data.size-1)
  when Array then row_args = [{}] + params[:build_in].map do |order| 
                                      if order <= 0 then {}
                                      else { "class" => "fragment", "data-fragment-index" => order } 
                                      end end
  end

  return tag("table", 
     data.zip(row_args).map { |row, args| tag("tr", row.join, args) }.join("\n"),
     params.fetch(:table_args, {})
  )
end