{-# Language FunctionalDependencies #-}
module TestAbstractDispatch where

import HBS2.Prelude
import HBS2.Net.Proto
import HBS2.Net.Messaging
import HBS2.Clock

import Control.Monad
import Control.Concurrent.Async
import Data.Cache (Cache)
import Data.Cache qualified as Cache
import Data.Foldable
import Data.Function
import Data.Functor
import Data.Hashable
import Data.Kind
import Data.Proxy
import Data.Word
import Data.Dynamic
import Prettyprinter
import System.Random qualified as Random
import GHC.TypeLits
import Data.Maybe

import Debug.Trace

import FakeMessaging

-- newtype Cookie = Cookie Word32
--                  deriving stock (Eq,Ord)
--                  deriving newtype Hashable

data family Cookie p :: Type

class Monad m => CookieGenerator p m where
  genCookie :: Hashable s => s -> m (Cookie p)

class Monad m => HasTimeout msg m where
  timeoutFor :: Proxy msg -> m (Timeout 'Seconds)

class HasCookie p msg | msg -> p where
  getCookie :: msg -> Maybe (Cookie p)


data DefAnswer p = forall msg . (IsEncoded p msg) => DefAnswer msg

class HasDefAnswer p a | p -> a where
  defAnswer :: a -> DefAnswer p


-- still okay

type family Encoded  p :: Type

class IsEncoded p msg | msg -> p where
  encode :: msg -> Encoded p
  decode :: Encoded p -> Maybe msg

-- still okay
data MessageWithCookie p = MessageWithCookie (Cookie p) (Encoded p)

-- ЧТО МЫ ХОТИМ:
-- СООБЩЕНИЯ РАЗНЫХ ТИПОВ. ОБРАБАТЫВАТЬ НЕЗАВИСИМО, В РАЗНЫХ ОБРАБОТЧИКАХ
--
-- ПОЧЕМУ МЫ ЭТОГО ХОТИМ:
--
--   ЧТО БЫ НЕ ДЕЛАТЬ ОДИН СЛОЖНЫЙ ОБРАБОТЧИК С БОЛЬШИМ СТЕЙТОМ
--   ТАКОЕ УЖЕ ДЕЛАЛИ, ТАМ ХУЙ НОГУ СЛОМИТ ПОТОМ ОТЛАЖИВАТЬ
--   НАДО СДЕЛАТЬ, ЧТО БЫ МОЖНО БЫЛО ОТЛАДИТЬ ПО КУСКАМ
--   ТЕМ БОЛЕЕ, ЧТО ОНИ ДРУГ ОТ ДРУГА НЕ ЗАВИСЯТ
--

data Handler p m  = forall msg . IsEncoded p msg =>
  Handler ( (From p, Cookie p) -> msg -> m () )

-- for convenience
handler :: forall msg m p . (IsEncoded p (msg p))
        => ((From p, Cookie p) -> msg p -> m ())
        -> Handler p m

handler = Handler

data Fabrique p = forall bus . Messaging bus p (MessageWithCookie p)
  =>  Fabrique bus

data Dispatcher p m =
  Dispatcher
  { self     :: Peer p
  , handlers :: Cache (Cookie p) (Handler p m) --- FIXME: class + maybe cookie
  , fabriq   :: Fabrique p
  }

newDispatcher :: (MonadIO m, (Messaging bus p (MessageWithCookie p)))
              => Peer p
              -> bus
              -> m (Dispatcher p m)

newDispatcher me bus = do
  let fab = Fabrique bus
  cache <- liftIO $ Cache.newCache Nothing
  pure $ Dispatcher me cache fab

sendRequest :: forall p msg m. ( MonadIO m
                               , IsEncoded p msg
                               , Messaging (Fabrique p) p (MessageWithCookie p)
                               , Hashable (Cookie p)
                               , CookieGenerator p m
                               , HasTimeout msg m
                               )
            => Dispatcher p m
            -> Peer p
            -> Maybe (Cookie p)
            -> msg
            -> Handler p m
            -> m ()

sendRequest d p mbCoo msg answ = do
  -- liftIO $ print "sending request!"
  cookie  <- maybe (genCookie p) pure mbCoo
  timeout <- timeoutFor (Proxy @msg) <&> Just . toTimeSpec
  liftIO $ Cache.insert' (handlers d) Nothing cookie answ
  sendTo (fabriq d) (To p) (From (self d)) (MessageWithCookie cookie (encode msg))

dispatcher :: forall p m . ( MonadIO m, Hashable (Cookie p), Pretty (Cookie p), Pretty (Peer p)
                           , Messaging (Fabrique p) p (MessageWithCookie p)
                           , HasDefAnswer p (Cookie p)
                           )
           => Dispatcher p m
           -> m ()

dispatcher d = fix \next -> do

  -- FIXME: if receive is non-blocking we'll get a busy loop
  -- FIXME: if receive is blocking - we'll block here forever
  received <- receive (fabriq d) (To (self d))

  for_ received $ \(who@(From peer), MessageWithCookie coo bs) -> do

    -- поискали в мапе по куке
    found <- liftIO $ Cache.lookup (handlers d) coo

    case found of
      Nothing -> do
        case defAnswer @p coo of
          DefAnswer msg -> do
            sendTo (fabriq d) (To peer) (From (self d)) (MessageWithCookie coo (encode msg))

      Just (Handler dispatch) -> maybe (pure ()) (dispatch (who,coo)) (decode bs)
    --                           ^^^^^^^^^^^^^^ CAN NOT DECODE CASE

  next


data PingPong p = Ping
                | Pong
                deriving stock (Typeable)

newtype instance Cookie Fake = CookieFake Word32
                               deriving stock (Eq)
                               deriving newtype (Hashable,Num,Pretty)


instance CookieGenerator Fake IO where
  genCookie s = do
    i <- Random.randomIO :: IO Int
    pure $ fromIntegral $ hash (i + hash s)

type instance Encoded Fake = Dynamic

instance Typeable (PingPong p) =>  IsEncoded Fake (PingPong p) where
  encode = toDyn
  decode = fromDynamic

instance Messaging (Fabrique Fake) Fake (MessageWithCookie Fake) where
  sendTo (Fabrique bus) = sendTo bus
  receive (Fabrique bus) = receive bus

instance HasTimeout (PingPong Fake) IO where
  timeoutFor _ = pure 1

instance HasDefAnswer Fake (Cookie Fake) where
  defAnswer _ = let _ = trace "ATTEMPT TO SEND DEF ANSWER" in DefAnswer (Pong @Fake)

testAbstractDispatch :: IO ()
testAbstractDispatch = do

  let peers = [1..2] :: [Peer Fake]

  bus  <- newFakeP2P @Fake @(MessageWithCookie Fake) True

  threads <- forM peers $ \p -> do
      disp <- newDispatcher p bus
      dispThread <- async (dispatcher disp)

      for_ [ px | px <- peers, px /= p ] $ \pip -> do

        -- liftIO $ print "sending ping"
        sendRequest disp pip Nothing (Ping @Fake) $ handler @PingPong $ \(From who, coo) ->
         \case
            Ping -> pure () -- we do not expect ping here

            Pong -> do

              liftIO $ print $ "got pong 2" <+> pretty who
                                            <+> "->"
                                            <+> pretty (self disp)
                                            <+> brackets (pretty coo)

      pure dispThread

    -- -- pure dispThread
  pause ( 1 :: Timeout 'Seconds)

  mapM_ cancel threads

  void $ waitAnyCatchCancel threads