{-# LANGUAGE DataKinds #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE ImportQualifiedPost #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}
module Main where

import Data.Dependent.EnumMap.Strict qualified as DE
import Data.Dependent.EnumMap.Strict.Internal (coe1)
import Data.Dependent.Sum
import Data.Functor.Const

data Tag = A | B | C
  deriving (Show)

data STag tag where
  SA :: STag A
  SB :: STag B
  SC :: STag C
deriving instance Show (STag tag)

instance DE.Enum1 STag where
  type Enum1Info STag = Const ()
  fromEnum1 = \case
                SA -> (0, Const ())
                SB -> (1, Const ())
                SC -> (2, Const ())
  toEnum1 n _ = case n of
                  0 -> coe1 SA
                  1 -> coe1 SB
                  2 -> coe1 SC
                  _ -> error "invalid tag"

data Value tag where
  VA :: Int -> Value A
  VB :: Bool -> Value B
  VC :: String -> Value c
deriving instance Show (Value tag)


main :: IO ()
main = do
  print $ DE.fromList @STag @Value []
  print $ DE.fromList [SB :=> VB False, SA :=> VA 3]