{-# LANGUAGE UndecidableInstances #-}

module Pandora.Paradigm.Primary.Transformer.Tap where

import Pandora.Core.Functor (type (:=))
import Pandora.Core.Appliable ((!))
import Pandora.Pattern.Semigroupoid ((.))
import Pandora.Pattern.Category (($), (#))
import Pandora.Pattern.Functor.Covariant (Covariant ((<$>)))
import Pandora.Pattern.Functor.Semimonoidal (Semimonoidal (mult))
import Pandora.Pattern.Functor.Monoidal (Monoidal (unit))
import Pandora.Pattern.Functor.Traversable (Traversable ((<<-)))
import Pandora.Pattern.Functor.Extendable (Extendable ((<<=)))
import Pandora.Pattern.Functor.Bivariant ((<->))
import Pandora.Pattern.Transformer.Liftable (Liftable (lift))
import Pandora.Pattern.Transformer.Lowerable (Lowerable (lower))
import Pandora.Pattern.Transformer.Hoistable (Hoistable ((/|\)))
import Pandora.Paradigm.Inventory.Store (Store (Store))
import Pandora.Paradigm.Controlflow.Effect.Interpreted (run)
import Pandora.Paradigm.Primary.Algebraic ((<-*-), extract)
import Pandora.Paradigm.Primary.Algebraic.Product ((:*:) ((:*:)), twosome)
import Pandora.Paradigm.Primary.Algebraic.Exponential (type (<--), type (-->), (%))
import Pandora.Paradigm.Primary.Functor.Identity (Identity (Identity))
import Pandora.Paradigm.Primary.Functor.Wye (Wye (Left, Right))
import Pandora.Pattern.Morphism.Flip (Flip (Flip))
import Pandora.Pattern.Morphism.Straight (Straight (Straight))
import Pandora.Paradigm.Primary.Transformer.Reverse (Reverse (Reverse))
import Pandora.Paradigm.Schemes.T_U (T_U (T_U), type (<:.:>))
import Pandora.Paradigm.Schemes.P_Q_T (P_Q_T (P_Q_T))
import Pandora.Paradigm.Structure.Ability.Substructure
	(Substructure (Available, Substance, substructure), Segment (Root))

data Tap t a = Tap a (t a)

instance Covariant (->) (->) t => Covariant (->) (->) (Tap t) where
	f <$> Tap x xs = Tap # f x # f <$> xs

instance Semimonoidal (-->) (:*:) (:*:) t => Semimonoidal (-->) (:*:) (:*:) (Tap t) where
	mult = Straight $ \(Tap x xs :*: Tap y ys) -> Tap (x :*: y) $ mult @(-->) ! xs :*: ys

instance Semimonoidal (<--) (:*:) (:*:) t => Semimonoidal (<--) (:*:) (:*:) (Tap t) where
	mult = Flip $ \(Tap (x :*: y) xys) ->
		(Tap x <-> Tap y) $ mult @(<--) ! xys

instance Semimonoidal (<--) (:*:) (:*:) t => Monoidal (<--) (->) (:*:) (:*:) (Tap t) where
	unit _ = Flip $ \(Tap x _) -> (\_ -> x)

instance Traversable (->) (->) t => Traversable (->) (->) (Tap t) where
	f <<- Tap x xs = Tap <$> f x <-*- f <<- xs

instance (Semimonoidal (<--) (:*:) (:*:) t, Extendable (->) t, Covariant (->) (->) t) => Extendable (->) (Tap t) where
	f <<= x = Tap # f x $ f . Tap (extract x) <<= lower x

instance Lowerable (->) Tap where
	lower (Tap _ xs) = xs

instance Hoistable Tap where
	f /|\ Tap x xs = Tap x # f xs

instance {-# OVERLAPS #-} Semimonoidal (-->) (:*:) (:*:) t => Semimonoidal (-->) (:*:) (:*:) (Tap (t <:.:> t := (:*:))) where
	mult = Straight $ \(Tap x (T_U (xls :*: xrs)) :*: Tap y (T_U (yls :*: yrs))) -> Tap (x :*: y)
		$ T_U $ (mult @(-->) ! (xls :*: yls)) :*: (mult @(-->) ! (xrs :*: yrs))

instance {-# OVERLAPS #-} Traversable (->) (->) t => Traversable (->) (->) (Tap (t <:.:> t := (:*:))) where
	f <<- Tap x (T_U (future :*: past)) = (\past' x' future' -> Tap x' $ twosome # future' # run past')
		<$> f <<- Reverse past <-*- f x <-*- f <<- future

instance (Covariant (->) (->) t) => Substructure Root (Tap (t <:.:> t := (:*:))) where
	type Available Root (Tap (t <:.:> t := (:*:))) = Identity
	type Substance Root (Tap (t <:.:> t := (:*:))) = Identity
	substructure = P_Q_T $ \zipper -> case lower zipper of
		Tap x xs -> Store $ Identity (Identity x) :*: lift . (Tap % xs) . extract . extract

instance (Covariant (->) (->) t) => Substructure Left (Tap (t <:.:> t := (:*:))) where
	type Available Left (Tap (t <:.:> t := (:*:))) = Identity
	type Substance Left (Tap (t <:.:> t := (:*:))) = t
	substructure = P_Q_T $ \zipper -> case lower zipper of
		Tap x (T_U (future :*: past)) -> Store $ Identity future :*: lift . Tap x . T_U . (:*: past) . extract

instance (Covariant (->) (->) t) => Substructure Right (Tap (t <:.:> t := (:*:))) where
	type Available Right (Tap (t <:.:> t := (:*:))) = Identity
	type Substance Right (Tap (t <:.:> t := (:*:))) = t
	substructure = P_Q_T $ \zipper -> case lower zipper of
		Tap x (T_U (future :*: past)) -> Store $ Identity past :*: lift . Tap x . T_U . (future :*:) . extract