{-# LANGUAGE CPP             #-}
{-# LANGUAGE LambdaCase      #-}
{-# LANGUAGE PatternSynonyms #-}
module Network.Tox.Onion.Handlers where

import qualified Data.Tox.DHT.Multi           as Multi
import Network.Kademlia.Search
import Network.Tox.TCP.NodeId (udpNodeInfo)
import Network.Tox.DHT.Transport
import Network.Tox.DHT.Handlers hiding (Message,Client)
import Network.Tox.Onion.Transport
import Network.QueryResponse as QR hiding (Client)
import qualified Network.QueryResponse as QR (Client)
import Crypto.Tox
import qualified Data.Wrapper.PSQ             as PSQ
         ;import Data.Wrapper.PSQ             (PSQ,pattern (:->))
import Control.Arrow

import Data.Function
import qualified Data.MinMaxPSQ               as MinMaxPSQ
         ;import Data.MinMaxPSQ               (MinMaxPSQ')
import Network.BitTorrent.DHT.Token           as Token

import Control.Exception hiding (Handler)
import Control.Monad
#ifdef THREAD_DEBUG
import Control.Concurrent.Lifted.Instrument
#else
import Control.Concurrent
import GHC.Conc (labelThread)
#endif
import Control.Concurrent.STM
import Data.Dependent.Sum ( (==>) )
import Data.Time.Clock.POSIX  (POSIXTime, getPOSIXTime)
import Network.Socket
#if MIN_VERSION_iproute(1,7,4)
import Data.IP hiding (fromSockAddr)
#else
import Data.IP
#endif
import Data.Maybe
import Data.Functor.Identity
import DPut
import DebugTag

type Client r = QR.Client String PacketKind TransactionId (OnionDestination r) Message
type Message = OnionMessage Identity

classify :: Message -> MessageClass String PacketKind TransactionId (OnionDestination r) Message
classify msg = go msg
 where
    go (OnionAnnounce         announce)    = IsQuery AnnounceType
                                                $ TransactionId (snd $ runIdentity $ asymmData announce)
                                                                (asymmNonce announce)
    go (OnionAnnounceResponse n8 n24 resp) = IsResponse (TransactionId n8 n24)
    go (OnionToRoute          {})          = IsQuery DataRequestType (TransactionId (Nonce8 0) (Nonce24 zeros24))
    go (OnionToRouteResponse  {})          = IsResponse              (TransactionId (Nonce8 0) (Nonce24 zeros24))

-- Toxcore generates `ping_id`s by taking a 32 byte sha hash of the current time,
-- some secret bytes generated when the instance is created, the current time
-- divided by a 20 second timeout, the public key of the requester and the source
-- ip/port that the packet was received from. Since the ip/port that the packet
-- was received from is in the `ping_id`, the announce packets being sent with a
-- ping id must be sent using the same path as the packet that we received the
-- `ping_id` from or announcing will fail.
--
-- The reason for this 20 second timeout in toxcore is that it gives a reasonable
-- time (20 to 40 seconds) for a peer to announce himself while taking in count
-- all the possible delays with some extra seconds.
announceH :: Routing -> TVar SessionTokens -> TVar AnnouncedKeys -> OnionDestination r -> AnnounceRequest -> IO AnnounceResponse
announceH routing toks keydb oaddr req = do
    case () of
        _ | announcePingId req == zeros32
          -> go False

        _ -> let Nonce32 bs = announcePingId req
                 tok        = fromPaddedByteString 32 bs
             in checkToken toks (onionNodeInfo oaddr) tok >>= go
        `catch` (\(SomeException e) -> dput XAnnounce ("announceH Exception! "++show e) >> throw e)
 where
    go withTok = do
        let naddr = onionNodeInfo oaddr
        ns <- getNodesH routing (Multi.UDP ==> naddr) (GetNodes (announceSeeking req))
        tm <- getPOSIXTime

        let storing = case oaddr of
                        OnionToOwner _ pth -> guard (nodeId naddr == announceSeeking req) >> Just pth
                        _                  -> Nothing
        dput XAnnounce   $ unlines [ "announceH: nodeId          = " ++ show (nodeId naddr)
                                   , "           announceSeeking = " ++ show (announceSeeking req)
                                   , "           withTok         = " ++ show withTok
                                   , "           storing         = " ++ maybe "False" (const "True") storing
                                   ]
        record <- atomically $ do
            forM_ storing $ \retpath -> when withTok $ do
                let toxpath = AnnouncedRoute naddr{ nodeId = announceKey req } retpath
                    -- Note: The following distance calculation assumes that
                    -- our nodeid doesn't change and is the same for both
                    -- routing4 and routing6.
                    d = xorNodeId (nodeId (tentativeId routing))
                                  (announceSeeking req)
                modifyTVar' keydb (insertKey tm (announceSeeking req) toxpath d)
            ks <- readTVar keydb
            return $ snd . snd <$> MinMaxPSQ.lookup' (announceSeeking req) (keyAssoc ks)
        newtok <- maybe (return $ zeros32)
                        (const $ Nonce32 . toPaddedByteString 32 <$> grantToken toks naddr)
                        storing
        let k = case record of
                Nothing                    -> NotStored newtok
                Just _  | isJust storing   -> Acknowledged newtok
                Just (AnnouncedRoute ni _) -> SendBackKey $ id2key (nodeId ni)
        let response = AnnounceResponse k ns
        dput XAnnounce $ unwords ["Announce:", show req, "-reply->", show response]
        return response

dataToRouteH ::
          TVar AnnouncedKeys
          -> Transport err (OnionDestination r) (OnionMessage f)
          -> addr
          -> OnionMessage f
          -> IO ()
dataToRouteH keydb udp _ (OnionToRoute pub asymm) = do
    let k = key2id pub
    dput XAnnounce $ "dataToRouteH "++ show k
    mb <- atomically $ do
        ks <- readTVar keydb
        forM (MinMaxPSQ.lookup' k (keyAssoc ks)) $ \(p,(cnt,rpath)) -> do
            writeTVar keydb $ ks { keyAssoc = MinMaxPSQ.insert' k (cnt + 1, rpath) p (keyAssoc ks) }
            return rpath
    dput XAnnounce $ "dataToRouteH "++ show (fmap (const ()) mb)
    forM_ mb $ \rpath -> do
        -- forward
        dput XAnnounce $ "dataToRouteH sendMessage"
        sendMessage udp (toOnionDestination rpath) $ OnionToRouteResponse asymm
        dput XAnnounce $ "Forwarding data-to-route -->"++show k

type NodeDistance = NodeId

data AnnouncedRoute = AnnouncedRoute NodeInfo (ReturnPath N3)

toOnionDestination :: AnnouncedRoute -> OnionDestination r
toOnionDestination (AnnouncedRoute ni rpath) = OnionToOwner ni rpath

-- |
-- The type 'NodeId' was originally made for the DHT key, but here
-- we reuse it for user keys (public key/real key).
--
-- To find someone using their user (public) key, you search for it on
-- kademlia. At each iteration of the search, you get a response with
-- closest known nodes(DHT keys) to the key you are searching for.
--
-- To do an 'Announce' so your friends can find you, you do a search to
-- find the closest nodes to your own user(public) key. At those nodes,
-- you store a route back to yourself (using Announce message) so your
-- friends can contact you. This means each node needs to store the
-- saved routes, and that is the purpose of the 'AnnouncedKeys' data
-- structure.
--
data AnnouncedKeys = AnnouncedKeys
    { keyByAge :: !(PSQ NodeId (POSIXTime{-Time at which they announced to you-}))
    , keyAssoc :: !(MinMaxPSQ' NodeId NodeDistance (Int{-count of route usage-},AnnouncedRoute))
        -- ^ PSQ using NodeId(user/public key) as Key
        --   and using 'NodeDistance' as priority.
        --   (smaller number is higher priority)
        --
        --  Keeping in a MinMaxPSQ will help us later when we want to make the structure
        --  bounded. (We simply throw away the most NodeDistant keys.
    }


insertKey :: POSIXTime -> NodeId -> AnnouncedRoute -> NodeDistance -> AnnouncedKeys -> AnnouncedKeys
insertKey tm pub toxpath d keydb = AnnouncedKeys
    { keyByAge = PSQ.insert pub tm (keyByAge keydb)
    , keyAssoc = case MinMaxPSQ.lookup' pub (keyAssoc keydb) of
                    Just (_,(cnt,_)) -> MinMaxPSQ.insert' pub (cnt,toxpath) d (keyAssoc keydb)
                    Nothing          -> MinMaxPSQ.insert' pub (0  ,toxpath) d (keyAssoc keydb)
    }

-- | Forks a thread to garbage-collect old key announcements.  Keys may be
-- discarded after 5 minutes.
forkAnnouncedKeysGC :: TVar AnnouncedKeys -> IO ThreadId
forkAnnouncedKeysGC db = forkIO $ do
    myThreadId >>= flip labelThread "gc:toxids"
    fix $ \loop -> do
    cutoff <- getPOSIXTime
    threadDelay 300000000 -- 300 seconds
    dput XAnnounce "(gc:toxids) Garbage collecting announced toxids."
    join $ atomically $ do
        fix $ \gc -> do
        keys <- readTVar db
        case PSQ.minView (keyByAge keys) of
            Nothing -> return loop
            Just (pub :-> tm,kba')
                | tm > cutoff -> return loop
                | otherwise   -> do writeTVar db keys
                                        { keyByAge = kba'
                                        , keyAssoc = MinMaxPSQ.delete pub (keyAssoc keys)
                                        }
                                    gc

areq :: Message -> Either String AnnounceRequest
areq (OnionAnnounce asymm) = Right $ fst $ runIdentity $ asymmData asymm
areq _                     = Left "Unexpected non-announce OnionMessage"

handlers :: Transport err (OnionDestination r) Message
            -> Routing
            -> TVar SessionTokens
            -> TVar AnnouncedKeys
            -> PacketKind
            -> Maybe (MethodHandler String TransactionId (OnionDestination r) Message)
handlers net routing toks keydb AnnounceType
    = Just
    $ MethodHandler areq (\(TransactionId n8 n24) src dst -> OnionAnnounceResponse n8 n24 . Identity)
    $ announceH routing toks keydb
handlers net _ _ keydb _ = Just $ NoReply Right $ dataToRouteH keydb net


toxidSearch :: (OnionDestination r -> STM (OnionDestination r, Int))
               -> TransportCrypto
               -> Client r
               -> Search NodeId (IP, PortNumber) Nonce32 NodeInfo Rendezvous TransactionId
toxidSearch getTimeout crypto client = Search
    { searchSpace       = toxSpace
    , searchNodeAddress = nodeIP &&& nodePort
    , searchQuery       = asyncGetRendezvous getTimeout crypto client
    , searchQueryCancel = cancelQuery client
    , searchAlpha       = 3
    , searchK           = 6
    }

announceSerializer :: (OnionDestination r -> STM (OnionDestination r, Int))
                   -> MethodSerializer
                        TransactionId
                        (OnionDestination r)
                        (OnionMessage Identity)
                        PacketKind
                        AnnounceRequest
                        (Maybe AnnounceResponse)
announceSerializer getTimeout = MethodSerializer
    { methodTimeout = getTimeout
    , method = AnnounceType
    , wrapQuery = \(TransactionId n8 n24) src dst req ->
        -- :: tid -> addr -> addr -> a -> OnionMessage Identity
        OnionAnnounce $ Asymm
            { -- The public key is our real long term public key if we want to
              -- announce ourselves, a temporary one if we are searching for
              -- friends.
              senderKey = onionKey src
            , asymmNonce = n24
            , asymmData = Identity (req, n8)
            }
    , unwrapResponse = \case -- :: OnionMessage Identity -> b
        OnionAnnounceResponse _ _ resp -> Just $ runIdentity resp
        _                              -> Nothing
    }

-- TODO Announce key to announce peers.
--
--   Announce Peers are only put in the 8 closest peers array if they respond
--   to an announce request. If the peers fail to respond to 3 announce
--   requests they are deemed timed out and removed.
--
--   ...
--
--   For this reason, after the peer is announced successfully for 17 seconds,
--   announce packets are sent aggressively every 3 seconds to each known close
--   peer (in the list of 8 peers) to search aggressively for peers that know
--   the peer we are searching for.

-- TODO
-- If toxcore goes offline (no onion traffic for 20 seconds) toxcore will
-- aggressively reannounce itself and search for friends as if it was just
-- started.

showResponse :: Bool -> NodeInfo -> AnnounceRequest -> AnnounceResponse -> String
showResponse is_async them req r = unlines $ map (mappend $ show them ++ " --> ") $
    [ "AnnounceResponse" ++ if is_async then " -- async" else ""
    , "  { announceSeeking = " ++ show (announceSeeking req)
    , "  , is_stored     = " ++ show (is_stored r)
    , "  , announceNodes = "
    ] ++ case announceNodes r of
        SendNodes ns -> map (mappend "      " . show) ns
    ++ [ "  }" ]

sendOnion :: (OnionDestination r -> STM (OnionDestination r, Int))
            -> Client r
            -> AnnounceRequest
            -> OnionDestination r
            -> (NodeInfo -> AnnounceResponse -> t)
            -> IO (QR.Result t)
sendOnion getTimeout client req oaddr unwrap =
    -- Four tries and then we tap out.
    flip fix 4 $ \loop n -> do
        mb <- QR.sendQuery client (announceSerializer getTimeout) req oaddr
        forM_ mb $ \mr -> forM_ mr $ \r ->
            dput XAnnounceResponse $ showResponse False (onionNodeInfo oaddr) req r
        let re = if n>0 then loop $! n - 1 else return Canceled
        case mb of
            Success x -> maybe re (return . Success . unwrap (onionNodeInfo oaddr)) x
            Canceled  -> return Canceled
            TimedOut  -> re

asyncOnion :: (OnionDestination r -> STM (OnionDestination r, Int))
            -> Client r
            -> AnnounceRequest
            -> OnionDestination r
            -> (NodeInfo -> AnnounceResponse -> t)
            -> (TransactionId -> QR.Result t -> IO ())
            -> IO TransactionId
asyncOnion getTimeout client req oaddr unwrap withResult = do
    -- TODO: Restore "Four tries and then we tap out" behavior.
    qid <- QR.asyncQuery client (announceSerializer getTimeout) req oaddr $ \k mb -> do
            forM_ mb $ \mr -> forM_ mr $ \r ->
                dput XAnnounceResponse $ showResponse True (onionNodeInfo oaddr) req r
            withResult k $ case mb of
                Success x -> maybe (TimedOut)
                                   (Success . unwrap (onionNodeInfo oaddr))
                                   (x :: Maybe AnnounceResponse)
                Canceled  -> Canceled
                TimedOut  -> TimedOut
    return qid


-- | Lookup the secret counterpart for a given alias key.
getRendezvous :: (OnionDestination r -> STM (OnionDestination r, Int))
            -> TransportCrypto
            -> Client r
            -> NodeId
            -> NodeInfo
            -> IO (Result ([NodeInfo],[Rendezvous],Maybe Nonce32))
getRendezvous getTimeout crypto client nid ni = do
    asel <- atomically $ selectAlias crypto nid
    let oaddr = OnionDestination asel ni Nothing
        rkey  = case asel of
                    SearchingAlias -> Nothing
                    _              -> Just $ key2id $ rendezvousPublic crypto
    sendOnion getTimeout client
        (AnnounceRequest zeros32 nid $ fromMaybe zeroID rkey)
        oaddr
        (unwrapAnnounceResponse rkey)

asyncGetRendezvous ::
            (OnionDestination r -> STM (OnionDestination r, Int))
            -> TransportCrypto
            -> Client r
            -> NodeId
            -> NodeInfo
            -> (TransactionId -> Result ([NodeInfo],[Rendezvous],Maybe Nonce32) -> IO ())
            -> IO TransactionId
asyncGetRendezvous getTimeout crypto client nid ni withResult = do
    asel <- atomically $ selectAlias crypto nid
    let oaddr = OnionDestination asel ni Nothing
        rkey  = case asel of
                    SearchingAlias -> Nothing
                    _              -> Just $ key2id $ rendezvousPublic crypto
    asyncOnion getTimeout client
        (AnnounceRequest zeros32 nid $ fromMaybe zeroID rkey)
        oaddr
        (unwrapAnnounceResponse rkey)
        withResult


putRendezvous :: (OnionDestination r -> STM (OnionDestination r, Int))
               -> TransportCrypto
               -> Client r
               -> PublicKey
               -> Nonce32
               -> NodeInfo
               -> IO (Maybe (Rendezvous, AnnounceResponse))
putRendezvous getTimeout crypto client pubkey nonce32 ni = do
    let longTermKey   = key2id pubkey
        rkey          = rendezvousPublic crypto
        rendezvousKey = key2id rkey
    asel <- atomically $ selectAlias crypto longTermKey
    let oaddr = OnionDestination asel ni Nothing
    dput XPublish $ "putRendezvous at " ++ show ni
    fmap resultToMaybe
        $ sendOnion getTimeout client (AnnounceRequest nonce32 longTermKey rendezvousKey) oaddr
        $ \ni resp -> (Rendezvous rkey ni, resp)