MQ3.hs

{-# LANGUAGE OverloadedStrings, DataKinds, DeriveGeneric, TypeFamilies #-}

module MQ where

import Database.Edis
import Data.ByteString
import Data.Serialize hiding (Get)
import GHC.Generics

data Message = Msg ByteString Integer deriving (Show, Generic)
instance Serialize Message where

fromRight :: Either a b -> b
fromRight (Right x) = x
fromRight (Left _) = error "Left"

push :: (StringOfIntegerOrNX xs "id", ListOrNX xs "queue")
    => ByteString
    -> Edis xs (Set xs "queue" (ListOf Message)) (Either Reply Integer)
push msg =          incr    (Proxy :: Proxy "id")
    `bind` \i ->    lpush   (Proxy :: Proxy "queue")    (Msg msg (fromRight i))

pop :: (Get xs "queue" ~ (ListOf Message))
    => Edis xs xs (Either Reply (Maybe Message))
pop = lpop (Proxy :: Proxy "queue")

main :: IO ()
main = do
    conn <- connect defaultConnectInfo
    result <- runRedis conn $ unEdis $ start
        >>> push "hello"
        >>> pop

    print $ result
    return ()