{-# LANGUAGE DeriveDataTypeable #-}

-- http://tools.ietf.org/html/rfc2109
module Happstack.Server.Internal.Cookie
    ( Cookie(..)
    , CookieLife(..)
    , calcLife
    , mkCookie
    , mkCookieHeader
    , getCookies
    , getCookie
    , getCookies'
    , getCookie'
    , parseCookies
    , cookiesParser
    )
    where

import Control.Monad
import qualified Data.ByteString.Char8 as C
import Data.Char             (chr, toLower)
import Data.Data             (Data, Typeable)
import Data.List             ((\\), intersperse)
import Data.Time.Clock       (UTCTime, addUTCTime, diffUTCTime)
import Data.Time.Clock.POSIX (posixSecondsToUTCTime)
import Data.Time.Format      (formatTime)
import Happstack.Server.Internal.Clock (getApproximateUTCTime)
import Text.ParserCombinators.Parsec hiding (token)
import System.Locale         (defaultTimeLocale)

-- | a type for HTTP cookies. Usually created using 'mkCookie'.
data Cookie = Cookie
    { cookieVersion :: String
    , cookiePath    :: String
    , cookieDomain  :: String
    , cookieName    :: String
    , cookieValue   :: String
    , secure        :: Bool
    , httpOnly      :: Bool
    } deriving(Show,Eq,Read,Typeable,Data)

-- | Specify the lifetime of a cookie.
--
-- Note that we always set the max-age and expires headers because
-- internet explorer does not honor max-age. You can specific 'MaxAge'
-- or 'Expires' and the other will be calculated for you. Choose which
-- ever one makes your life easiest.
--
data CookieLife
    = Session         -- ^ session cookie - expires when browser is closed
    | MaxAge Int      -- ^ life time of cookie in seconds
    | Expires UTCTime -- ^ cookie expiration date
    | Expired         -- ^ cookie already expired
      deriving (Eq, Ord, Read, Show, Typeable)

-- convert 'CookieLife' to the argument needed for calling 'mkCookieHeader'
calcLife :: CookieLife -> IO (Maybe (Int, UTCTime))
calcLife Session = return Nothing
calcLife (MaxAge s) =
          do now <- getApproximateUTCTime
             return (Just (s, addUTCTime (fromIntegral s) now))
calcLife (Expires expirationDate) =
          do now <- getApproximateUTCTime
             return $ Just (round  $ expirationDate `diffUTCTime` now, expirationDate)
calcLife Expired =
          return $ Just (0, posixSecondsToUTCTime 0)


-- | Creates a cookie with a default version of 1, empty domain, a
-- path of "/", secure == False and httpOnly == False
--
-- see also: 'addCookie'
mkCookie :: String  -- ^ cookie name
         -> String  -- ^ cookie value
         -> Cookie
mkCookie key val = Cookie "1" "/" "" key val False False

-- | Set a Cookie in the Result.
-- The values are escaped as per RFC 2109, but some browsers may
-- have buggy support for cookies containing e.g. @\'\"\'@ or @\' \'@.
--
-- Also, it seems that chrome, safari, and other webkit browsers do
-- not like cookies which have double quotes around the domain and
-- reject/ignore the cookie. So, we no longer quote the domain.
--
-- internet explorer does not honor the max-age directive so we set
-- both max-age and expires.
--
-- See 'CookieLife' and 'calcLife' for a convenient way of calculating
-- the first argument to this function.
mkCookieHeader :: Maybe (Int, UTCTime) -> Cookie -> String
mkCookieHeader mLife cookie =
    let l = [("Domain=",  cookieDomain cookie)
            ,("Max-Age=", maybe "" (show . max 0 . fst) mLife)
            ,("expires=", maybe "" (formatTime defaultTimeLocale "%a, %d-%b-%Y %X GMT" . snd) mLife)
            ,("Path=",    cookiePath cookie)
            ,("Version=", s cookieVersion)]
        s f | f cookie == "" = ""
        s f   = '\"' : concatMap e (f cookie) ++ "\""
        e c | fctl c || c == '"' = ['\\',c]
            | otherwise          = [c]
    in concat $ intersperse ";" ((cookieName cookie++"="++s cookieValue):[ (k++v) | (k,v) <- l, "" /= v ] ++
                                 (if secure cookie then ["Secure"] else []) ++
                                 (if httpOnly cookie then ["HttpOnly"] else []))

fctl :: Char -> Bool
fctl ch = ch == chr 127 || ch <= chr 31

-- | Not an supported api.  Takes a cookie header and returns
-- either a String error message or an array of parsed cookies
parseCookies :: String -> Either String [Cookie]
parseCookies str = either (Left . show) Right $ parse cookiesParser str str

-- | not a supported api.  A parser for RFC 2109 cookies
cookiesParser :: GenParser Char st [Cookie]
cookiesParser = cookies
    where -- Parsers based on RFC 2109
          cookies = do
            ws
            ver<-option "" $ try (cookie_version >>= (\x -> cookieSep >> return x))
            cookieList<-(cookie_value ver) `sepBy1` try cookieSep
            ws
            eof
            return cookieList
          cookie_value ver = do
            name<-name_parser
            cookieEq
            val<-value
            path<-option "" $ try (cookieSep >> cookie_path)
            domain<-option "" $ try (cookieSep >> cookie_domain)
            return $ Cookie ver path domain (low name) val False False
          cookie_version = cookie_special "$Version"
          cookie_path = cookie_special "$Path"
          cookie_domain = cookie_special "$Domain"
          cookie_special s = do
            void $ string s
            cookieEq
            value
          cookieSep = ws >> oneOf ",;" >> ws
          cookieEq = ws >> char '=' >> ws
          ws = spaces
          value         = word
          word          = try quoted_string <|> try incomp_token <|> return ""

          -- Parsers based on RFC 2068
          quoted_string = do
            void $ char '"'
            r <-many ((try quotedPair) <|> (oneOf qdtext))
            void $ char '"'
            return r

          -- Custom parsers, incompatible with RFC 2068, but more forgiving ;)
          incomp_token  = many1 $ oneOf ((chars \\ ctl) \\ " \t\";")
          name_parser   = many1 $ oneOf ((chars \\ ctl) \\ "= ;,")

          -- Primitives from RFC 2068
          ctl           = map chr (127:[0..31])
          chars         = map chr [0..127]
          octet         = map chr [0..255]
          text          = octet \\ ctl
          qdtext        = text \\ "\""
          quotedPair    = char '\\' >> anyChar

-- | Get all cookies from the HTTP request. The cookies are ordered per RFC from
-- the most specific to the least specific. Multiple cookies with the same
-- name are allowed to exist.
getCookies :: Monad m => C.ByteString -> m [Cookie]
getCookies h = getCookies' h >>=  either (fail. ("Cookie parsing failed!"++)) return

-- | Get the most specific cookie with the given name. Fails if there is no such
-- cookie or if the browser did not escape cookies in a proper fashion.
-- Browser support for escaping cookies properly is very diverse.
getCookie :: Monad m => String -> C.ByteString -> m Cookie
getCookie s h = getCookie' s h >>= either (const $ fail ("getCookie: " ++ show s)) return

getCookies' :: Monad m => C.ByteString -> m (Either String [Cookie])
getCookies' header | C.null header = return $ Right []
                   | otherwise     = return $ parseCookies (C.unpack header)

getCookie' :: Monad m => String -> C.ByteString -> m (Either String Cookie)
getCookie' s h = do
    cs <- getCookies' h
    return $ do -- Either
       cooks <- cs
       case filter (\x->(==)  (low s)  (cookieName x) ) cooks of
            [] -> fail "No cookie found"
            f -> return $ head f

low :: String -> String
low = map toLower

