+{-# LANGUAGE ScopedTypeVariables #-}
+
-- | (Un)picklers for data types present in The Sports Network XML
-- feed.
--
module TSN.Picklers (
pickler_tests,
xp_ambiguous_time,
+ xp_attr_option,
xp_date,
xp_date_padded,
xp_datetime,
--
-- >>> import Data.Maybe ( fromJust )
-- >>> :{
--- let parse_date :: String -> Maybe UTCTime;
--- parse_date = parseTime defaultTimeLocale date_format;
+-- let parse_date :: String -> Maybe UTCTime
+-- parse_date = parseTime defaultTimeLocale date_format
-- :}
--
-- >>> let dates = [ "1/" ++ (d : "/1970") | d <- ['1'..'9'] ]
fmt = "%A, %B %-d" ++ upper_suffix ++ " (" ++ date_format_padded ++ ")"
+-- | This is a replacement for @xpOption xpFoo@ within an 'xpAttr'.
+-- There's a bug <https://github.com/UweSchmidt/hxt/issues/39> in
+-- newer versions of HXT that prevents us from using the usual
+-- 'xpOption' solution, so this is our stopgap. It should work on
+-- any type that can be unpickled with a plain read/show.
+--
+xp_attr_option :: forall a. (Read a, Show a) => PU (Maybe a)
+xp_attr_option =
+ (to_a, from_a) `xpWrap` xpText
+ where
+ to_a :: String -> Maybe a
+ to_a = readMaybe
+
+ from_a :: Maybe a -> String
+ from_a Nothing = ""
+ from_a (Just x) = show x
+
-- | Create an 'XmlTree' containing only the given text. This is
-- useful for testing (un)picklers, where we don't want to have to