src/TSN/Picklers.hs

   1 -- | (Un)picklers for data types present in The Sports Network XML
   2 --   feed.
   3 --
   4 module TSN.Picklers (
   5   xp_date,
   6   xp_team_id )
   7 where
   8
   9 -- System imports.
  10 import Data.Time.Clock ( UTCTime )
  11 import Data.Time.Format ( formatTime, parseTime )
  12 import System.Locale ( defaultTimeLocale )
  13 import Text.XML.HXT.Arrow.Pickle (
  14   xpText,
  15   xpWrapMaybe )
  16 import Text.XML.HXT.Arrow.Pickle.Xml ( PU )
  17
  18
  19 -- | (Un)pickle a UTCTime without the time portion.
  20 --
  21 xp_date :: PU UTCTime
  22 xp_date =
  23   (to_date, from_date) `xpWrapMaybe` xpText
  24   where
  25     format = "%-m/%-d/%Y"
  26
  27     to_date :: String -> Maybe UTCTime
  28     to_date = parseTime defaultTimeLocale format
  29
  30     from_date :: UTCTime -> String
  31     from_date = formatTime defaultTimeLocale format
  32
  33
  34 -- | Parse a team_id. These are (so far!) three characters long, and
  35 --   not necessarily numeric. For simplicity, we return a 'String'
  36 --   rather than e.g. a @(Char, Char, Char)@. But unpickling will fail
  37 --   if the team_id is longer than three characters.
  38 --
  39 xp_team_id :: PU String
  40 xp_team_id =
  41   (to_team_id, from_team_id) `xpWrapMaybe` xpText
  42   where
  43     to_team_id :: String -> Maybe String
  44     to_team_id s
  45       | length s <= 3 = Just s
  46       | otherwise = Nothing
  47
  48     from_team_id :: String -> String
  49     from_team_id = id