gistfile1.builder

def Facter.case(name, whens)
  if whens[:default].is_a?(Exception)
    default = proc { raise whens[:default] }
  elsif whens[:default].is_a?(Proc)
    default = whens[:default]
  elsif whens[:default]
    default = proc { whens[:default] }
  else
    default = proc { |value| raise "Unsupported case for '#{name}': #{value}" }
  end

  if value = self[name]
    if result = whens[value]
      return result
    else
      return default.call(value)
    end
  else
    raise "No value was returned for '#{name}'"
  end
end