+{-# LANGUAGE DeriveDataTypeable #-}
+
+-- | A newtype around a list of Strings which represent the feed
+-- hosts. This is all to avoid an orphan instance of Configured for
+-- [String] if we had defined one in e.g. OptionalConfiguration.
+--
+-- This was placed under the "TSN" namespace because its Default
+-- instance is specific to TSN, even though otherwise it's just a
+-- list of strings.
+--
+module FeedHosts
+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 (
+ Configured,
+ Value( List ),
+ convert )
+import Data.Data (Data)
+import System.Console.CmdArgs.Default (Default(..))
+import Data.Typeable (Typeable)
+
+
+-- | A (wrapper around a) list of hostnames that supply the XML feed.
+--
+newtype FeedHosts =
+ FeedHosts { get_feed_hosts :: [String] }
+ deriving (Data, Show, Typeable)
+
+
+instance Default FeedHosts where
+ -- | The default list of feed hosts. These were found by checking
+ -- PTR records in the neighborhood of the IP address in use. There
+ -- is a feed4.sportsnetwork.com, but it was not operational when
+ -- this was written.
+ def = FeedHosts ["feed1.sportsnetwork.com",
+ "feed2.sportsnetwork.com",
+ "feed3.sportsnetwork.com"]
+
+
+instance DCT.Configured FeedHosts where
+ -- | This allows us to read a FeedHosts object out of a Configurator
+ -- config file. By default Configurator wouldn't know what to do,
+ -- so we have to tell it that we expect a list, and if that list
+ -- has strings in it, we can apply the FeedHosts constructor to
+ -- it.
+ convert (DCT.List xs) =
+ -- mapM gives us a Maybe [String] here.
+ fmap FeedHosts (mapM convert_string xs)
+ where
+ convert_string :: DCT.Value -> Maybe String
+ convert_string = DCT.convert
+
+ -- If we read anything other than a list of values out of the file,
+ -- fail.
+ convert _ = Nothing