Move the TSN namespace (Xml.hs and FeedHosts.hs) into the top level.

[dead/htsn.git] / src / FeedHosts.hs

diff --git a/src/FeedHosts.hs b/src/FeedHosts.hs
new file mode 100644 (file)
index 0000000..b3fcc48
--- /dev/null
+++ b/src/FeedHosts.hs
@@ -0,0 +1,57 @@
+{-# 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