module Pandora.Paradigm.Basis.Jack (Jack (..), jack) where

import Pandora.Core.Morphism ((.), ($))
import Pandora.Pattern.Functor.Covariant (Covariant ((<$>)), comap)
import Pandora.Pattern.Functor.Pointable (Pointable (point))
import Pandora.Pattern.Functor.Extractable (Extractable (extract))
import Pandora.Pattern.Functor.Alternative (Alternative ((<+>)))
import Pandora.Pattern.Functor.Exclusive (Exclusive (exclusive))
import Pandora.Pattern.Functor.Applicative (Applicative ((<*>)))
import Pandora.Pattern.Functor.Traversable (Traversable ((->>), traverse))
import Pandora.Pattern.Functor.Distributive (Distributive ((>>-), distribute))
import Pandora.Pattern.Functor.Liftable (Liftable (lift))

data Jack t a = It a | Other (t a)

instance Covariant t => Covariant (Jack t) where
        f <$> It x = It $ f x
        f <$> Other y = Other $ f <$> y

instance Covariant t => Pointable (Jack t) where
        point = It

instance Alternative t => Alternative (Jack t) where
        It x <+> _ = It x
        Other _ <+> It y = It y
        Other x <+> Other y = Other (x <+> y)

instance Exclusive t => Exclusive (Jack t) where
        exclusive = Other exclusive

instance Applicative t => Applicative (Jack t) where
        It f <*> It x = It $ f x
        It f <*> Other y = Other $ f <$> y
        Other f <*> It x = Other $ ($ x) <$> f
        Other f <*> Other y = Other $ f <*> y

instance Traversable t => Traversable (Jack t) where
        It x ->> f = It <$> f x
        Other y ->> f = comap Other . traverse f $ y

instance Distributive t => Distributive (Jack t) where
        x >>- f = distribute $ f <$> x

instance Liftable Jack where
        lift = Other

jack :: (a -> r) -> (t a -> r) -> Jack t a -> r
jack f _ (It x) = f x
jack _ g (Other y) = g y