-- | (Un)picklers for data types present in The Sports Network XML
--   feed.
--
module TSN.Picklers (
  xp_date,
  xp_team_id )
where

-- System imports.
import Data.Time.Clock ( UTCTime )
import Data.Time.Format ( formatTime, parseTime )
import System.Locale ( defaultTimeLocale )
import Text.Printf ( printf )
import Text.Read ( readMaybe )
import Text.XML.HXT.Arrow.Pickle (
  xpText,
  xpWrapMaybe )
import Text.XML.HXT.Arrow.Pickle.Xml ( PU )


-- | (Un)pickle a UTCTime without the time portion.
--
xp_date :: PU UTCTime
xp_date =
  (to_date, from_date) `xpWrapMaybe` xpText
  where
    format = "%-m/%-d/%Y"

    to_date :: String -> Maybe UTCTime
    to_date = parseTime defaultTimeLocale format

    from_date :: UTCTime -> String
    from_date = formatTime defaultTimeLocale format


-- | 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