{-# Language TypeFamilyDependencies  #-}
{-# Language FunctionalDependencies  #-}
module HasProtocol where

import Data.Kind
import Data.Proxy
import GHC.TypeLits
import Data.Hashable

-- e -> Transport (like, UDP or TChan)
-- p -> L4 Protocol (like Ping/Pong)

class (Hashable (Peer e), Eq (Peer e)) =>HasPeer e where
  data family (Peer e) :: Type

class (KnownNat (ProtocolId p), HasPeer e) => HasProtocol e p | p -> e  where
  type family ProtocolId p = (id :: Nat) | id -> p
  type family Encoded e :: Type

  protoId :: forall . KnownNat (ProtocolId p) => Proxy p -> Integer
  protoId _ = natVal (Proxy @(ProtocolId p))

  decode :: Encoded e -> Maybe p
  encode :: p -> Encoded e