class UserAgent

def to_str
  if @product && !@version.nil? && @comment
    "#{@product}/#{@version} (#{@comment.join("; ")})"
  elsif @product && !@version.nil?
    "#{@product}/#{@version}"
  elsif @product && @comment
    "#{@product} (#{@comment.join("; ")})"
  else
    @product
  end
end