X-Git-Url: http://gitweb.michael.orlitzky.com/?p=dead%2Fhalcyon.git;a=blobdiff_plain;f=src%2FUsernames.hs;fp=src%2FUsernames.hs;h=6f2fb2874108bd436a18ad0aedde8ad4db5112a3;hp=0000000000000000000000000000000000000000;hb=dd4abc21674b98bc55a3775291a8667dffec2863;hpb=93577603f6df06e4627ca13a6f5fe412b28dc817

diff --git a/src/Usernames.hs b/src/Usernames.hs
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+++ b/src/Usernames.hs
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+{-# 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
+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