orphan.hs

{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}

module Orphan where

import qualified Hedgehog                 as H
import qualified Hedgehog.Gen             as Gen
import qualified Hedgehog.Range           as Range

import qualified Crypto.PubKey.Curve25519 as Curve25519
import           Crypto.Random.Types      (MonadRandom (..))
import qualified Data.ByteArray           as BA

-- the orphan instance I'd like to get rid of
instance Monad m => MonadRandom (H.GenT m) where
  getRandomBytes size = do
    bytes <- Gen.bytes (Range.singleton size)
    pure $ BA.convert bytes

genSecretKeyOrphan :: (H.MonadGen m, MonadRandom m) => m Curve25519.SecretKey
genSecretKeyOrphan = Curve25519.generateSecretKey


newtype Foo a = Foo { runFoo :: H.Gen a }
  deriving (Functor, Applicative, Monad, H.MonadGen)

instance MonadRandom Foo where
  getRandomBytes size = do
    bytes <- Gen.bytes (Range.singleton size)
    pure $ BA.convert bytes

-- -- question is, how do I use that?
-- genSecretKey :: (H.MonadGen m) => m Curve25519.SecretKey
-- -- genSecretKey = runFoo $ Foo $ do ????