{-# LANGUAGE GADTs #-}
module Connection.Tox where

import qualified Connection   as G
         ;import Connection   (Manager (..), Policy (..))
import Control.Concurrent.STM
-- import Crypto.Tox
import Data.Dependent.Sum
import Data.Functor.Identity
import qualified Data.Map     as Map
-- import Data.Maybe
-- import Network.Tox
import Network.Tox.NodeId
import PingMachine
import Text.Read


-- | This type indicates the progress of a tox encrypted friend link
-- connection.  Two scenarios are illustrated below.  The parenthesis show the
-- current 'G.Status' 'ToxProgress' of the session.
--
--
-- Perfect handshake scenario:
--
--  Peer 1                                  Peer 2
--  (InProgress AcquiringCookie)            (Dormant/InProgress AcquiringCookie)
--                     Cookie request ->
--                                       <- Cookie response
--  (InProgress AwaitingHandshake)          (Dormant/InProgress AcquiringCookie)
--                   Handshake packet ->
--                                          * accepts connection
--                                          (InProgress AwaitingSessionPacket)
--                                       <- Handshake packet
--  *accepts connection
--  (InProgress AwaitingSessionPacket)
--                   Encrypted packet -> <- Encrypted packet
--  *confirms connection                    *confirms connection
--  (Established)                           (Established)
--
--                           Connection successful.
--
--                  Encrypted packets -> <- Encrypted packets
--
--
--
--
--  More realistic handshake scenario:
--  Peer 1                                  Peer 2
--  (InProgress AcquiringCookie)            (Dormant/InProgress AcquiringCookie)
--                      Cookie request ->   *packet lost*
--                      Cookie request ->
--                                        <- Cookie response
--  (InProgress AwaitingHandshake)           (Dormant/InProgress AcquiringCookie)
--
--                                           *Peer 2 randomly starts new connection to peer 1
--                                           (InProgress AcquiringCookie)
--                                        <- Cookie request
--                     Cookie response ->
--                                           (InProgress AwaitingHandshake)
--
--                    Handshake packet -> <- Handshake packet
--  *accepts connection                      * accepts connection
--  (InProgress AwaitingSessionPacket)      (InProgress AwaitingSessionPacket)
--
--                    Encrypted packet -> <- Encrypted packet
--  *confirms connection                     *confirms connection
--  (Established)                           (Established)
--
--                              Connection successful.
--
--                   Encrypted packets -> <- Encrypted packets
data ToxProgress
    = AwaitingDHTKey        -- ^ Waiting to receive their DHT key.
    | AcquiringIPAddress    -- ^ Searching DHT to obtain their node's IP & port.
    | AcquiringCookie       -- ^ Attempting to obtain a cookie.
    | AwaitingHandshake     -- ^ Waiting to receive a handshake.
    | AwaitingSessionPacket -- ^ Connection is "accepted" but not yet "confirmed".
    deriving (Eq,Ord,Enum,Show)


data Parameters = Parameters
    { -- | Various Tox transports and clients.
      -- toxTransports :: Tox
      -- | Thread to be forked when a connection is established.
      -- TODO: this function should accept relevant parameters.
     onToxSession  :: IO ()
    }

data Key = Key NodeId{-me-} NodeId{-them-}

instance Show Key where show = show . showKey_


-- | A conneciton status that is tagged with a state type that is specific to
-- the status.
data Transient a where
    IsDormant               :: Transient ()
    IsAwaitingDHTKey        :: Transient ()
    IsAcquiringIPAddress    :: Transient ()
    IsAcquiringCookie       :: Transient ()
    IsAwaitingHandshake     :: Transient ()
    IsAwaitingSessionPacket :: Transient ()
    IsEstablished           :: Transient ()


untag :: DSum Transient Identity -> G.Status ToxProgress
untag (IsDormant               :=> _) = G.Dormant
untag (IsAwaitingDHTKey        :=> _) = G.InProgress AwaitingDHTKey
untag (IsAcquiringIPAddress    :=> _) = G.InProgress AcquiringIPAddress
untag (IsAcquiringCookie       :=> _) = G.InProgress AcquiringCookie
untag (IsAwaitingHandshake     :=> _) = G.InProgress AwaitingHandshake
untag (IsAwaitingSessionPacket :=> _) = G.InProgress AwaitingSessionPacket
untag (IsEstablished           :=> _) = G.Established


data SessionState = SessionState
    { transient     :: TVar (DSum Transient Identity)
    , connPolicy    :: TVar Policy
    , connPingLogic :: PingMachine
    }

sessionStatus :: SessionState -> G.Connection ToxProgress
sessionStatus st = G.Connection
    { G.connStatus    = untag <$> readTVar (transient st)
    , G.connPolicy    = readTVar (connPolicy st)
    , G.connPingLogic = connPingLogic st
    }


-- | This function will fork threads as necessary.
setToxPolicy :: Parameters
             -> TVar (Map.Map Key SessionState)
             -> Key
             -> Policy
             -> IO ()
setToxPolicy params conmap k policy = case policy of
    TryingToConnect -> do
        -- TODO initiate connecting if we haven't already
        -- When established, invoke 'onToxSession'.
        return ()
    RefusingToConnect -> do
        -- TODO disconnect or cancel any pending connection
        return ()
    OpenToConnect -> do
        -- TODO passively accept connections if they initiate.
        return ()


showKey_ :: Key -> String
showKey_ (Key me them) = show me ++ ":" ++ show them

stringToKey_ :: String -> Maybe Key
stringToKey_ s = let (xs,ys) = break (==':') s
                 in if null ys then Nothing
                               else do me <- readMaybe xs
                                       them <- readMaybe (drop 1 ys)
                                       return $ Key me them

toxManager :: Parameters -> IO (Manager ToxProgress Key)
toxManager params = do
    conmap <- newTVarIO Map.empty
    return Manager
        { setPolicy    = setToxPolicy params conmap             -- k -> Policy -> IO ()
        , connections  = fmap sessionStatus <$> readTVar conmap -- STM (Map k (Connection status))
        , stringToKey  = stringToKey_                           -- String -> Maybe k
        , showProgress = show                                   -- status -> String
        , showKey      = showKey_                               -- k -> String
        }