{-# LANGUAGE UndecidableInstances #-}
module Pandora.Paradigm.Primary.Transformer.Instruction where

import Pandora.Core.Functor (type (:.), type (>>>))
import Pandora.Pattern.Semigroupoid ((.))
import Pandora.Pattern.Category ((<--), (<---), (<----), (<-----), (<------))
import Pandora.Pattern.Morphism.Straight (Straight (Straight))
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.Bindable (Bindable ((=<<)))
import Pandora.Pattern.Functor.Monad (Monad)
import Pandora.Pattern.Transformation.Liftable (Liftable (lift))
import Pandora.Pattern.Transformation.Lowerable (Lowerable (lower))
import Pandora.Pattern.Transformation.Hoistable (Hoistable ((/|\)))
import Pandora.Pattern.Operation.Exponential (type (-->))
import Pandora.Pattern.Operation.Product ((:*:)((:*:)))
import Pandora.Pattern.Operation.One (One (One))
import Pandora.Paradigm.Algebraic (point)
import Pandora.Core.Interpreted ((<~), (<~~~))

data Instruction t a = Enter a | Instruct (t :. Instruction t >>> a)

instance Covariant (->) (->) t => Covariant (->) (->) (Instruction t) where
	f <-|- Enter x = Enter <-- f x
	f <-|- Instruct xs = Instruct <------ f <-|-|- xs

instance (Covariant (->) (->) t, Semimonoidal (-->) (:*:) (:*:) t) => Semimonoidal (-->) (:*:) (:*:) (Instruction t) where
	mult = Straight <-- \case
		Enter x :*: Enter y -> Enter <--- x :*: y
		Enter x :*: Instruct y -> (x :*:) <-|- Instruct y
		Instruct x :*: Enter y -> (:*: y) <-|- Instruct x
		Instruct x :*: Instruct y -> Instruct <----- (mult @(-->) <~) <-|-- mult @(-->) <~~~ x :*: y

instance (Covariant (->) (->) t, Semimonoidal (-->) (:*:) (:*:) t) => Monoidal (-->) (-->) (:*:) (:*:) (Instruction t) where
	unit _ = Straight <-- Enter . (<~ One)

instance Covariant (->) (->) t => Bindable (->) (Instruction t) where
	f =<< Enter x = f x
	f =<< Instruct xs = Instruct <---- (f =<<) <-|- xs

instance Monad (->) t => Monad (->) (Instruction t) where

instance Traversable (->) (->) t => Traversable (->) (->) (Instruction t) where
	f <-/- Enter x = Enter <-|- f x
	f <-/- Instruct xs = Instruct <-|- (f <-/-/- xs)

instance Liftable (->) Instruction where
	lift x = Instruct <---- Enter <-|- x

instance (forall t . Bindable (->) t, forall t . Monoidal (-->) (-->) (:*:) (:*:) t) => Lowerable (->) Instruction where
	lower (Enter x) = point x
	lower (Instruct xs) = lower =<< xs

instance (forall v . Covariant (->) (->) v) => Hoistable (->) Instruction where
	_ /|\ Enter x = Enter x
	f /|\ Instruct xs = Instruct <---- (f /|\) <-|- f xs