+{-# LANGUAGE FlexibleContexts #-}
+module Data.Time.RFC822.Internal
+ ( rfc822DateAndTime
+
+ -- private
+ , rfc822time
+ )
+ where
+import Control.Monad
+import Data.Fixed
+import Data.Time
+import Data.Time.Calendar.WeekDate
+import Data.Time.HTTP.Common
+
+-- |This is a parsec parser for RFC 822 date and time strings.
+rfc822DateAndTime :: Stream s m Char => ParsecT s u m ZonedTime
+rfc822DateAndTime = dateTime
+
+dateTime :: Stream s m Char => ParsecT s u m ZonedTime
+dateTime = do weekDay <- optionMaybe $
+ do w <- shortWeekDayNameP
+ _ <- string ", "
+ return w
+ gregDay <- date
+ case weekDay of
+ Nothing
+ -> return () -- No day in week exists.
+ Just givenWD
+ -> assertWeekDayIsGood givenWD gregDay
+ (tod, timeZone) <- rfc822time
+ let lt = LocalTime gregDay tod
+ zt = ZonedTime lt timeZone
+ return zt
+
+date :: Stream s m Char => ParsecT s u m Day
+date = do day <- read2
+ _ <- char ' '
+ month <- shortMonthNameP
+ _ <- char ' '
+ year <- liftM (+ 1900) read2
+ _ <- char ' '
+ assertGregorianDateIsGood year month day
+
+rfc822time :: Stream s m Char => ParsecT s u m (TimeOfDay, TimeZone)
+rfc822time = do tod <- hour
+ _ <- char ' '
+ tz <- zone
+ return (tod, tz)
+
+hour :: Stream s m Char => ParsecT s u m TimeOfDay
+hour = do hour <- read2
+ minute <- char ':' >> read2
+ second <- option 0 (char ':' >> read2)
+ assertTimeOfDayIsGood hour minute second
+
+zone :: Stream s m Char => ParsecT s u m TimeZone
+zone = choice [ string "UT" >> return (TimeZone 0 False "UT" )
+ , string "GMT" >> return (TimeZone 0 False "GMT")
+ , char 'E'
+ >> choice [ string "ST" >> return (TimeZone ((-5) * 60) False "EST")
+ , string "DT" >> return (TimeZone ((-4) * 60) True "EDT")
+ ]
+ , char 'C'
+ >> choice [ string "ST" >> return (TimeZone ((-6) * 60) False "CST")
+ , string "DT" >> return (TimeZone ((-5) * 60) True "CDT")
+ ]
+ , char 'M'
+ >> choice [ string "ST" >> return (TimeZone ((-7) * 60) False "MST")
+ , string "DT" >> return (TimeZone ((-6) * 60) True "MDT")
+ , return (TimeZone ((-12) * 60) False "M")
+ ]
+ , char 'P'
+ >> choice [ string "ST" >> return (TimeZone ((-8) * 60) False "PST")
+ , string "DT" >> return (TimeZone ((-7) * 60) True "PDT")
+ ]
+ , char 'Z' >> return (TimeZone 0 False "Z")
+ , char 'A' >> return (TimeZone ((-1) * 60) False "A")
+ , char 'N' >> return (TimeZone ( 1 * 60) False "N")
+ , char 'Y' >> return (TimeZone ( 12 * 60) False "Y")
+ , read4digitsTZ
+ ]