affection/src/Affection/MessageBus/Class.hs

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{-# LANGUAGE MultiParamTypeClasses #-}
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{-# LANGUAGE TypeFamilies #-}
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{-# LANGUAGE FlexibleContexts #-}
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{-# LANGUAGE AllowAmbiguousTypes #-}
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{-# LANGUAGE ExistentialQuantification #-}
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module Affection.MessageBus.Class
( Participant(..)
, genUUID
, UUID
) where
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import Affection.MessageBus.Message
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import Affection.Types
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import Control.Monad.IO.Class (liftIO)
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import Data.UUID
import Data.UUID.V4
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import Data.String as S (fromString)
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import Affection.Logging
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-- | This typeclass defines the behaviour of a participant in the message system
class (Message (Mesg prt), Show (Mesg prt)) => Participant prt where
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-- | Message datatype
type Mesg prt :: *
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-- | Function to get the list of subscribers from the participant
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partSubscribers
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:: prt
-- ^ the 'Participant''s subscriber storage
-> Affection [Mesg prt -> Affection ()]
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-- ^ List of Subscriber functions
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-- | Subscribe to the 'Participant''s events
partSubscribe
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:: prt
-- ^ The 'Participant''s subscriber storage
-> (Mesg prt -> Affection ())
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-- ^ What to do in case of a 'Message'
-- (Subscriber function)
-> Affection UUID
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-- ^ 'UUID' of the registered subscriber Function
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-- | Unsubscribe a Subscriber function from Participant
partUnSubscribe
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:: prt
-- ^ The 'Participant''s subscriber storage to unsubscribe from
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-> UUID
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-- ^ The subscriber function's 'UUID'
-> Affection ()
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-- | Get the 'Participant' to emit a 'Message' on all of its subscribers
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partEmit
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:: prt
-- ^ The 'Participant''s subscriber storage
-> Mesg prt
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-- ^ The 'Message' to emit
-> Affection ()
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partEmit p m = do
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liftIO $ logIO Verbose $ "Emitting message: " <> S.fromString (show m)
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l <- partSubscribers p
mapM_ ($ m) l
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-- | Helper function to generate new 'UUID's
genUUID :: Affection UUID
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genUUID = liftIO nextRandom