{-# LANGUAGE
    FlexibleInstances
  , MultiParamTypeClasses
  , OverloadedStrings
  , TemplateHaskell
  , UnicodeSyntax
  #-}
-- |This module provides functions to parse and format RFC 1123 date
-- and time strings (<http://tools.ietf.org/html/rfc1123#page-55>).
--
-- The format is basically the same as RFC 822, but the syntax for
-- @date@ is changed from:
--
-- > year ::= 2DIGIT
--
-- to:
--
-- > year ::= 4DIGIT
module Data.Time.Format.RFC1123
    ( RFC1123
    , rfc1123
    , rfc1123DateAndTime
    )
    where
import Control.Applicative
import Data.Ascii (Ascii, AsciiBuilder)
import qualified Data.Ascii as A
import Data.Attoparsec.Char8
import Data.Convertible.Base
import Data.Monoid.Unicode
import Data.Proxy
import Data.Tagged
import Data.Time
import Data.Time.Calendar.WeekDate
import Data.Time.Format.HTTP.Common
import Data.Time.Format.RFC822.Internal
import Prelude.Unicode

-- |The phantom type for conversions between RFC 1123 date and time
-- strings and 'ZonedTime'.
--
-- >>> convertSuccess (ZonedTime (LocalTime (ModifiedJulianDay 49662) (TimeOfDay 8 49 37)) utc)
-- Tagged "Sun, 06 Nov 1994 08:49:37 GMT"
data RFC1123

-- |The proxy for conversions between RFC 1123 date and time strings
-- and 'ZonedTime'.
rfc1123 ∷ Proxy RFC1123
{-# INLINE CONLIKE rfc1123 #-}
rfc1123 = Proxy

instance ConvertSuccess ZonedTime (Tagged RFC1123 Ascii) where
    {-# INLINE convertSuccess #-}
    convertSuccess = (A.fromAsciiBuilder <$>) ∘ cs

instance ConvertSuccess ZonedTime (Tagged RFC1123 AsciiBuilder) where
    {-# INLINE convertSuccess #-}
    convertSuccess = Tagged ∘ toAsciiBuilder

instance ConvertAttempt (Tagged RFC1123 Ascii) ZonedTime where
    {-# INLINE convertAttempt #-}
    convertAttempt = parseAttempt' rfc1123DateAndTime ∘ untag

-- |Parse an RFC 1123 date and time string.
rfc1123DateAndTime ∷ Parser ZonedTime
rfc1123DateAndTime = dateTime

dateTime ∷ Parser ZonedTime
dateTime = do weekDay ← optionMaybe $
                         do w ← shortWeekDayNameP
                            _ ← string ", "
                            return w
              gregDay ← date
              case weekDay of
                Nothing
                    → return ()
                Just givenWD
                    → assertWeekDayIsGood givenWD gregDay
              (tod, timeZone) ← rfc822Time
              let lt = LocalTime gregDay tod
                  zt = ZonedTime lt timeZone
              return zt

date ∷ Parser Day
date = do day   ← read2
          _     ← char ' '
          month ← shortMonthNameP
          _     ← char ' '
          year  ← read4
          _     ← char ' '
          assertGregorianDateIsGood year month day

toAsciiBuilder ∷ ZonedTime → AsciiBuilder
toAsciiBuilder zonedTime
    = let localTime          = zonedTimeToLocalTime zonedTime
          timeZone           = zonedTimeZone zonedTime
          (year, month, day) = toGregorian (localDay localTime)
          (_, _, week)       = toWeekDate  (localDay localTime)
          timeOfDay          = localTimeOfDay localTime
      in
        shortWeekDayName week
        ⊕ A.toAsciiBuilder ", "
        ⊕ show2 day
        ⊕ A.toAsciiBuilder " "
        ⊕ shortMonthName month
        ⊕ A.toAsciiBuilder " "
        ⊕ show4 year
        ⊕ A.toAsciiBuilder " "
        ⊕ show2 (todHour timeOfDay)
        ⊕ A.toAsciiBuilder ":"
        ⊕ show2 (todMin timeOfDay)
        ⊕ A.toAsciiBuilder ":"
        ⊕ show2 (floor (todSec timeOfDay) ∷ Int)
        ⊕ A.toAsciiBuilder " "
        ⊕ untag (cs timeZone ∷ Tagged RFC822 AsciiBuilder)

deriveAttempts [ ([t| ZonedTime |], [t| Tagged RFC1123 Ascii        |])
               , ([t| ZonedTime |], [t| Tagged RFC1123 AsciiBuilder |])
               ]