MQ2.hs

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

module MQ where

import Database.Edis
import Data.ByteString
import Data.Serialize
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 msg = unEdis $ start
    >>> declare         (Proxy :: Proxy "id")       (Proxy :: Proxy Integer)
    >>> declare         (Proxy :: Proxy "queue")    (Proxy :: Proxy (ListOf Message))
    >>> incr            (Proxy :: Proxy "id")
    `bind` \i -> lpush  (Proxy :: Proxy "queue")    (Msg msg (fromRight i))

pop = unEdis $ start
    >>> declare         (Proxy :: Proxy "queue")    (Proxy :: Proxy (ListOf Message))
    >>> lpop            (Proxy :: Proxy "queue")


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

    print $ result
    return ()