+
+
+-- | Parse a team_id. These are (so far!) three characters long, and
+-- not necessarily numeric. For simplicity, we return a 'String'
+-- rather than e.g. a @(Char, Char, Char)@. But unpickling will fail
+-- if the team_id is longer than three characters.
+--
+xp_team_id :: PU String
+xp_team_id =
+ (to_team_id, from_team_id) `xpWrapMaybe` xpText
+ where
+ to_team_id :: String -> Maybe String
+ to_team_id s
+ | length s <= 3 = Just s
+ | otherwise = Nothing
+
+ from_team_id :: String -> String
+ from_team_id = id