{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE StrictData #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE ScopedTypeVariables #-}
module MaybeHelp where
import Control.Lens
import Data.Aeson
import GHC.Generics
import TH.Derive
import Data.Store

data Maybe' a = Just' {__Just' :: a} | Nothing'
    deriving (Eq,Ord,Show,Read,Generic)
instance ToJSON a => ToJSON (Maybe' a) where
  toEncoding = genericToEncoding defaultOptions
instance FromJSON a => FromJSON (Maybe' a)

fromJust' :: Maybe' a -> a
fromJust' mx = case mx of
    Just' x -> x
    Nothing' -> error "no fromJust'"

isJust' :: Maybe' a -> Bool
isJust' Just' {} = True
isJust' Nothing' = False

isNothing' :: Maybe' a -> Bool
isNothing' Just' {} = False
isNothing' Nothing' = True

strictify :: Maybe a -> Maybe' a
strictify Nothing  = Nothing'
strictify (Just x) = Just' x

toggleJust :: Maybe a -> Maybe ()
toggleJust Nothing = Just ()
toggleJust _ = Nothing

makeLenses ''Maybe'
$($(derive [d| instance (Store a => Deriving (Store (Maybe' a))) |]))