{-# OPTIONS_HADDOCK hide #-}
{-# LANGUAGE NoMonomorphismRestriction, OverloadedStrings #-}

-- Submodule for functionality related to SASL negotation:
-- authentication functions, SASL functionality, bind functionality,
-- and the legacy `{urn:ietf:params:xml:ns:xmpp-session}session'
-- functionality.

module Network.Xmpp.Sasl
    ( xmppSasl
    , digestMd5
    , scramSha1
    , plain
    , auth
    ) where

import           Control.Applicative
import           Control.Arrow (left)
import           Control.Monad
import           Control.Monad.Error
import           Control.Monad.State.Strict
import           Data.Maybe (fromJust, isJust)

import qualified Crypto.Classes as CC

import qualified Data.Binary as Binary
import qualified Data.ByteString.Base64 as B64
import qualified Data.ByteString.Char8 as BS8
import qualified Data.ByteString.Lazy as BL
import qualified Data.Digest.Pure.MD5 as MD5
import qualified Data.List as L
import           Data.Word (Word8)

import qualified Data.Text as Text
import           Data.Text (Text)
import qualified Data.Text.Encoding as Text

import           Network.Xmpp.Stream
import           Network.Xmpp.Types

import qualified System.Random as Random

import           Network.Xmpp.Sasl.Types
import           Network.Xmpp.Sasl.Mechanisms

import           Control.Concurrent.STM.TMVar

import Control.Exception

import Data.XML.Pickle
import Data.XML.Types

import Network.Xmpp.Types
import Network.Xmpp.Marshal

import Control.Monad.State(modify)

import Control.Concurrent.STM.TMVar

import Control.Monad.Error

-- | Uses the first supported mechanism to authenticate, if any. Updates the
-- state with non-password credentials and restarts the stream upon
-- success. Returns `Nothing' on success, an `AuthFailure' if
-- authentication fails, or an `XmppFailure' if anything else fails.
xmppSasl :: [SaslHandler] -- ^ Acceptable authentication mechanisms and their
                       -- corresponding handlers
         -> TMVar Stream
         -> IO (Either XmppFailure (Maybe AuthFailure))
xmppSasl handlers = withStream $ do
    -- Chooses the first mechanism that is acceptable by both the client and the
    -- server.
    mechanisms <- gets $ streamSaslMechanisms . streamFeatures
    case (filter (\(name, _) -> name `elem` mechanisms)) handlers of
        [] -> return $ Right $ Just $ AuthNoAcceptableMechanism mechanisms
        (_name, handler):_ -> do
            cs <- gets streamState
            case cs of
                Closed -> return . Right $ Just AuthNoStream
                _ -> do
                       r <- runErrorT handler
                       case r of
                           Left ae -> return $ Right $ Just ae
                           Right a -> do
                               _ <- runErrorT $ ErrorT restartStream
                               return $ Right $ Nothing

-- | Authenticate to the server using the first matching method and bind a
-- resource.
auth :: [SaslHandler]
     -> Maybe Text
     -> TMVar Stream
     -> IO (Either XmppFailure (Maybe AuthFailure))
auth mechanisms resource con = runErrorT $ do
    ErrorT $ xmppSasl mechanisms con
    jid <- lift $ xmppBind resource con
    lift $ startSession con
    return Nothing

-- Produces a `bind' element, optionally wrapping a resource.
bindBody :: Maybe Text -> Element
bindBody = pickleElem $
               -- Pickler to produce a
               -- "<bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'/>"
               -- element, with a possible "<resource>[JID]</resource>"
               -- child.
               xpBind . xpOption $ xpElemNodes "resource" (xpContent xpId)

-- Sends a (synchronous) IQ set request for a (`Just') given or server-generated
-- resource and extract the JID from the non-error response.
xmppBind  :: Maybe Text -> TMVar Stream -> IO (Either XmppFailure Jid)
xmppBind rsrc c = runErrorT $ do
    answer <- ErrorT $ pushIQ "bind" Nothing Set Nothing (bindBody rsrc) c
    case answer of
        Right IQResult{iqResultPayload = Just b} -> do
            let jid = unpickleElem xpJid b
            case jid of
                Right jid' -> do
                    ErrorT $ withStream (do
                                      modify $ \s -> s{streamJid = Just jid'}
                                      return $ Right jid') c -- not pretty
                    return jid'
                otherwise -> throwError XmppOtherFailure
                -- TODO: Log: ("Bind couldn't unpickle JID from " ++ show answer)
        otherwise -> throwError XmppOtherFailure
  where
    -- Extracts the character data in the `jid' element.
    xpJid :: PU [Node] Jid
    xpJid = xpBind $ xpElemNodes jidName (xpContent xpPrim)
    jidName = "{urn:ietf:params:xml:ns:xmpp-bind}jid"

-- A `bind' element pickler.
xpBind  :: PU [Node] b -> PU [Node] b
xpBind c = xpElemNodes "{urn:ietf:params:xml:ns:xmpp-bind}bind" c

sessionXml :: Element
sessionXml = pickleElem
    (xpElemBlank "{urn:ietf:params:xml:ns:xmpp-session}session")
    ()

sessionIQ :: Stanza
sessionIQ = IQRequestS $ IQRequest { iqRequestID      = "sess"
                                   , iqRequestFrom    = Nothing
                                   , iqRequestTo      = Nothing
                                   , iqRequestLangTag = Nothing
                                   , iqRequestType    = Set
                                   , iqRequestPayload = sessionXml
                                   }

-- Sends the session IQ set element and waits for an answer. Throws an error if
-- if an IQ error stanza is returned from the server.
startSession :: TMVar Stream -> IO ()
startSession con = do
    answer <- pushIQ "session" Nothing Set Nothing sessionXml con
    case answer of
        Left e -> error $ show e
        Right _ -> return ()