-- | Indicate that something contains only a `Single` part of something.
module NewtypeZoo.Single
  ( Single(Single)
  , _theSingle
  , theSingle
  ) where

import           Control.DeepSeq (NFData)
import           Control.Monad.Fix (MonadFix)
import           Control.Monad.Zip (MonadZip)
import           Data.Bits       (Bits,FiniteBits)
import           Data.Copointed  (Copointed)
import           Data.Default    (Default)
import           Data.Functor.Classes (Eq1, Ord1, Read1, Show1)
import           Data.Functor.Identity
import           Data.Ix         (Ix)
import           Data.Profunctor (Profunctor, dimap)
import           Data.Pointed    (Pointed)
import           Data.String     (IsString)
import           Data.Typeable   (Typeable)
import           Foreign.Storable (Storable)
import           GHC.Generics    (Generic, Generic1)
import           System.Random   (Random)
import           Test.QuickCheck (Arbitrary)

newtype Single a = Single a
  deriving ( Eq
           , Ord
           , Read
           , Show
           , NFData
           , Foldable
           , Traversable
           , Functor
           , Default
           , Monoid
           , Semigroup
           , Typeable
           , Generic
           , Generic1
           , Random
           , Arbitrary
           , Bounded
           , Enum
           , Floating
           , Fractional
           , Integral
           , Num
           , Real
           , RealFloat
           , RealFrac
           , Ix
           , IsString
           , Bits
           , FiniteBits
           )
  deriving ( Eq1
           , Ord1
           , Read1
           , Show1
           , Pointed
           , Copointed
           , Applicative
           , MonadFix
           , Monad
           , MonadZip

           )
           via Identity

_theSingle :: Single x -> x
_theSingle (Single !x) = x
{-# INLINE _theSingle #-}

theSingle :: forall a b p f. (Profunctor p, Functor f) => p a (f b) -> p (Single a) (f (Single b))
theSingle = dimap _theSingle (fmap Single)
{-# INLINE theSingle #-}