{-# LANGUAGE GHC2024, TemplateHaskell, DerivingStrategies #-}

module INTx where

import GHC.TypeLits (Nat, KnownNat)
import qualified Language.Haskell.TH              as TH

-- | ABI integer value types, where @s@ is for signess and @n@ is the multiple of 8 bits
newtype INTx (s :: Bool) (n :: Nat) = INT Integer deriving newtype (Eq, Ord, Enum)

-- | A constraint that restricts what Nat values are valid for 'INTx'.
class KnownNat n => ValidINTn n

-- | A top-level splice that declares all the valid INTx n values.
flip foldMap [1..32] $ \i -> [d| instance ValidINTn $(TH.litT (TH.numTyLit i)) |]

-- | Sign of the INTx type. Use type application on @a@.
intxSign :: forall a (s :: Bool) (n :: Nat). (a ~ INTx s n, KnownBool s, ValidINTn n) => Bool
intxSign = toBool (SBool @s)

-- | Number of bits for the INTx type. Use type application on @a@.
intxNBits :: forall a (s :: Bool) (n :: Nat). (a ~ INTx s n, ValidINTn n) => Int
intxNBits = fromEnum (8 * natVal (Proxy @n))