{-# LANGUAGE DeriveDataTypeable #-}

-- | A newtype around a list of Strings which represent the usernames
--   to watch. This is all to avoid an orphan instance of Configured
--   for [String] if we had defined one in e.g. OptionalConfiguration.
--
module Usernames ( Usernames(..) )
where

-- DC is needed only for the DCT.Configured instance of String.
import qualified Data.Configurator as DC()
import qualified Data.Configurator.Types as DCT
import Data.Data ( Data )
import System.Console.CmdArgs.Default ( Default(..) )
import Data.Typeable ( Typeable )


newtype Usernames =
  Usernames { get_usernames :: [String] }
    deriving (Data, Show, Typeable)


instance Default Usernames where
  def = Usernames []


instance DCT.Configured Usernames where
  convert (DCT.List xs) =
    fmap Usernames (mapM convert_string xs)
    where
      convert_string :: DCT.Value -> Maybe String
      convert_string = DCT.convert

  convert _ = Nothing