attempt at json serialization in haskell

changes.hs

{-# LANGUAGE DeriveGeneric, DeriveAnyClass, StandaloneDeriving #-}

import Data.Map (empty, fromList, insert, delete, Map)
import GHC.Generics
import Data.Aeson
import qualified Data.Text.Lazy.IO as T
import qualified Data.Text.Lazy.Encoding as T

data Task = Task
    { id :: String
    , description :: String
    , dependsOn :: [String]
    , dependentTasks :: [String]
    } deriving (Eq, Show, Generic, ToJSON, FromJSON)

type Storage = Map String Task
type Change = Storage -> Storage

s :: Storage
s = empty

addTask :: Task -> Change
addTask (Task id desc dep dept) = insert id (Task id desc dep dept)

instance ToJSON Change where
    parseJSON (Array v) = do
        name <- parseJSON $ v V.! 0
        task <- parseJSON $ v V.! 1
        return (addTask task)

removeTask :: String -> Change
removeTask tid = delete tid

changes = [addTask (Task "1" "Description" [] []), removeTask "1"]

-- main = putStrLn . show $ foldl (\s c -> c s) s changes

d = "[addTask, {\"id\": \"1\", \"description\": \"d\", \"dependsOn\": [], \"dependentTasks\": []}]"

main = putStrLn . show $ decode d $ s

-- main = T.putStrLn . T.decodeUtf8 . encode $ changes