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{-# LANGUAGE OverloadedStrings #-}
module Network.HTTP.Date.Parser (parseHTTPDate) where
import Control.Applicative
import Control.Monad
import Data.Attoparsec.ByteString
import Data.Attoparsec.ByteString.Char8
import Data.ByteString
import Data.Char
import Network.HTTP.Date.Types
----------------------------------------------------------------
-- |
-- Parsing HTTP Date. Currently only RFC1123 style is supported.
--
-- >>> parseHTTPDate "Tue, 15 Nov 1994 08:12:31 GMT"
-- Just (HTTPDate {hdYear = 1994, hdMonth = 11, hdDay = 15, hdHour = 8, hdMinute = 12, hdSecond = 31, hdWkday = 2})
parseHTTPDate :: ByteString -> Maybe HTTPDate
parseHTTPDate bs = case parseOnly rfc1123Date bs of
Right ut -> Just ut
_ -> Nothing
rfc1123Date :: Parser HTTPDate
rfc1123Date = do
w <- wkday
void $ string ", "
(y,m,d) <- date1
sp
(h,n,s) <- time
sp
-- RFC 2616 defines GMT only but there are actually ill-formed ones such
-- as "+0000" and "UTC" in the wild.
void $ string "GMT" <|> string "+0000" <|> string "UTC"
return $ defaultHTTPDate {
hdYear = y
, hdMonth = m
, hdDay = d
, hdHour = h
, hdMinute = n
, hdSecond = s
, hdWkday = w
}
wkday :: Parser Int
wkday = 1 <$ string "Mon"
<|> 2 <$ string "Tue"
<|> 3 <$ string "Wed"
<|> 4 <$ string "Thu"
<|> 5 <$ string "Fri"
<|> 6 <$ string "Sat"
<|> 7 <$ string "Sun"
date1 :: Parser (Int,Int,Int)
date1 = do
d <- day
sp
m <- month
sp
y <- year
return (y,m,d)
where
day = digit2
year = digit4
sp :: Parser ()
sp = () <$ char ' '
time :: Parser (Int,Int,Int)
time = do
h <- digit2
void $ char ':'
m <- digit2
void $ char ':'
s <- digit2
return (h,m,s)
month :: Parser Int
month = 1 <$ string "Jan"
<|> 2 <$ string "Feb"
<|> 3 <$ string "Mar"
<|> 4 <$ string "Apr"
<|> 5 <$ string "May"
<|> 6 <$ string "Jun"
<|> 7 <$ string "Jul"
<|> 8 <$ string "Aug"
<|> 9 <$ string "Sep"
<|> 10 <$ string "Oct"
<|> 11 <$ string "Nov"
<|> 12 <$ string "Dec"
digit2 :: Parser Int
digit2 = do
x1 <- toInt <$> digit
x2 <- toInt <$> digit
return $ x1 * 10 + x2
digit4 :: Parser Int
digit4 = do
x1 <- toInt <$> digit
x2 <- toInt <$> digit
x3 <- toInt <$> digit
x4 <- toInt <$> digit
return $ x1 * 1000 + x2 * 100 + x3 * 10 + x4
toInt :: Char -> Int
toInt c = ord c - ord '0'
|
