{-# LANGUAGE NoMonomorphismRestriction, OverloadedStrings  #-}
module Network.XMPP.SASL where

import Control.Applicative
import Control.Monad
import Control.Monad.Trans
import Control.Monad.Trans.State

import qualified Crypto.Classes as CC

import qualified Data.Attoparsec.ByteString.Char8 as AP
import qualified Data.Binary as Binary
import qualified Data.ByteString as BS
import qualified Data.ByteString.Char8 as BS8
import qualified Data.ByteString.Lazy as BL
import qualified Data.ByteString.Lazy.Char8 as BL8
import qualified Data.ByteString.Base64 as B64
import qualified Data.List as L
import qualified Data.Digest.Pure.MD5 as MD5
import Data.List
import Data.XML.Types

import qualified Data.Text as Text
import qualified Data.Text.Encoding as Text

import Network.XMPP.Monad

import Numeric --

import qualified System.Random as Random

import Text.XML.Stream.Elements

saslInitE mechanism =
    Element "{urn:ietf:params:xml:ns:xmpp-sasl}auth"
        [("mechanism", [ContentText mechanism])
        ]
        []

saslResponseE resp =
    Element "{urn:ietf:params:xml:ns:xmpp-sasl}response" []
    [NodeContent $ ContentText resp]

saslResponse2E =
    Element "{urn:ietf:params:xml:ns:xmpp-sasl}response" [] []

xmppSASL passwd = do
  mechanisms <- gets $ saslMechanisms . sFeatures
  unless ("DIGEST-MD5" `elem` mechanisms) $ error "No usable auth mechanism"
  push $ saslInitE "DIGEST-MD5"
  Element "{urn:ietf:params:xml:ns:xmpp-sasl}challenge" []
    [NodeContent (ContentText content)] <- pull
  let (Right challenge) = B64.decode . Text.encodeUtf8 $ content
  let Right pairs = toPairs challenge
  liftIO $ BS.putStrLn challenge
  push . saslResponseE =<< createResponse passwd pairs
  Element name attrs content <- pull
  when (name == "{urn:ietf:params:xml:ns:xmpp-sasl}failure") $
    (error $ show content)
  push saslResponse2E
  Element "{urn:ietf:params:xml:ns:xmpp-sasl}sucess" <- pull
  return ()

createResponse passwd' pairs = do
  let Just qop = L.lookup "qop" pairs
  let Just nonce = L.lookup "nonce" pairs
  uname <- Text.encodeUtf8 <$> gets username
  let passwd = Text.encodeUtf8 passwd'
  realm <- Text.encodeUtf8 <$> gets sHostname
  g <- liftIO $ Random.newStdGen
  let cnonce = BS.tail . BS.init .
               B64.encode . BS.pack . take 8 $ Random.randoms g
  let nc = "00000001"
  let digestURI = ("xmpp/" `BS.append` realm)
  let digest = md5Digest
                 uname
                 realm
                 passwd
                 digestURI
                 nc
                 qop
                 nonce
                 cnonce
  let response = BS.intercalate"," . map (BS.intercalate "=") $
       [["username"  , quote uname     ]
       ,["realm"     , quote realm     ]
       ,["nonce"     , quote nonce     ]
       ,["cnonce"    , quote cnonce    ]
       ,["nc"        ,       nc        ]
       ,["qop"       ,       qop       ]
       ,["digest-uri", quote digestURI ]
       ,["response"  ,       digest    ]
       ,["charset"   ,       "utf-8"   ]
       ]
  liftIO $ BS.putStrLn response
  return . Text.decodeUtf8 $ B64.encode response
  where quote x = BS.concat ["\"",x,"\""]

toPairs :: BS.ByteString -> Either String [(BS.ByteString, BS.ByteString)]
toPairs = AP.parseOnly . flip AP.sepBy1 (void $ AP.char ',') $ do
  AP.skipSpace
  name <- AP.takeWhile1 (/= '=')
  AP.char '='
  quote <- ((AP.char '"' >> return True) `mplus` return False)
  content <- AP.takeWhile1 (AP.notInClass ",\"" )
  when quote . void $ AP.char '"'
  return (name,content)

hash = BS8.pack . show
       . (CC.hash' :: BS.ByteString -> MD5.MD5Digest) . BS.intercalate (":")

hashRaw = toStrict . Binary.encode
          . (CC.hash' :: BS.ByteString -> MD5.MD5Digest) . BS.intercalate (":")

toStrict = BS.concat . BL.toChunks
-- TODO: this only handles MD5-sess
md5Digest uname realm password digestURI nc qop nonce cnonce=
  let ha1 = hash [hashRaw [uname,realm,password], nonce, cnonce]
      ha2 = hash ["AUTHENTICATE", digestURI]
  in hash [ha1,nonce, nc, cnonce,qop,ha2]