src/FeedHosts.hs

   1 {-# LANGUAGE DeriveDataTypeable #-}
   2
   3 -- | A newtype around a list of Strings which represent the feed
   4 -- hosts. This is all to avoid an orphan instance of Configured for
   5 -- [String] if we had defined one in e.g. OptionalConfiguration.
   6 --
   7 module FeedHosts
   8 where
   9
  10 -- DC is needed only for the DCT.Configured instance of String.
  11 import qualified Data.Configurator as DC()
  12 import qualified Data.Configurator.Types as DCT
  13 import Data.Data (Data)
  14 import System.Console.CmdArgs.Default (Default(..))
  15 import Data.Typeable (Typeable)
  16
  17
  18 newtype FeedHosts =
  19   FeedHosts { get_feed_hosts :: [String] }
  20     deriving (Data, Show, Typeable)
  21
  22
  23 instance Default FeedHosts where
  24   def = FeedHosts ["feed1.sportsnetwork.com",
  25                    "feed2.sportsnetwork.com",
  26                    "feed3.sportsnetwork.com"]
  27
  28
  29 instance DCT.Configured FeedHosts where
  30   convert (DCT.List xs) =
  31     fmap FeedHosts (mapM convert_string xs)
  32     where
  33       convert_string :: DCT.Value -> Maybe String
  34       convert_string = DCT.convert
  35
  36   convert _ = Nothing
  37