{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE DefaultSignatures #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE UndecidableInstances #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
-- | Expression for 'MonoFunctor'.
module Language.Symantic.Expr.MonoFunctor where

import Control.Monad (liftM2)
import Data.Proxy (Proxy(..))
import Data.Type.Equality ((:~:)(Refl))
import Prelude hiding (fmap)
-- import qualified Data.Function as Fun
import qualified Data.MonoTraversable as MT
import Data.MonoTraversable (MonoFunctor)

import Language.Symantic.Type
import Language.Symantic.Repr
import Language.Symantic.Expr.Root
import Language.Symantic.Expr.Error
import Language.Symantic.Expr.From
import Language.Symantic.Expr.Lambda
import Language.Symantic.Trans.Common

-- * Class 'Sym_MonoFunctor'
-- | Symantic.
class Sym_Lambda repr => Sym_MonoFunctor repr where
	omap :: MonoFunctor m => repr (MT.Element m -> MT.Element m) -> repr m -> repr m
	default omap :: (Trans t repr, MonoFunctor m)
	 => t repr (MT.Element m -> MT.Element m) -> t repr m -> t repr m
	omap = trans_map2 omap
instance Sym_MonoFunctor Repr_Host where
	omap = liftM2 MT.omap
instance Sym_MonoFunctor Repr_Text where
	omap = repr_text_app2 "omap"
instance
 ( Sym_MonoFunctor r1
 , Sym_MonoFunctor r2
 ) => Sym_MonoFunctor (Repr_Dup r1 r2) where
	omap (f1 `Repr_Dup` f2) (m1 `Repr_Dup` m2) =
		omap f1 m1 `Repr_Dup` omap f2 m2

-- * Type 'Expr_MonoFunctor'
-- | Expression.
data Expr_MonoFunctor (root:: *)
type instance Root_of_Expr      (Expr_MonoFunctor root)      = root
type instance Type_of_Expr      (Expr_MonoFunctor root)      = No_Type
type instance Sym_of_Expr       (Expr_MonoFunctor root) repr = (Sym_MonoFunctor repr)
type instance Error_of_Expr ast (Expr_MonoFunctor root)      = No_Error_Expr

-- | Parse 'omap'.
omap_from
 :: forall root ty ast hs ret.
 ( ty ~ Type_Root_of_Expr (Expr_MonoFunctor root)
 , Type0_Eq ty
 , Expr_From ast root
 , Type0_Lift   Type_Fun (Type_of_Expr root)
 , Type0_Unlift Type_Fun (Type_of_Expr root)
 , Error_Expr_Lift (Error_Expr (Error_of_Type ast ty) ty ast)
                   (Error_of_Expr ast root)
 , Root_of_Expr root ~ root
 , Type0_Constraint MonoFunctor ty
 , Type0_Family Type_Family_MonoElement ty
 ) => ast -> ast
 -> ExprFrom ast (Expr_MonoFunctor root) hs ret
omap_from ast_f ast_m ex ast ctx k =
 -- NOTE: omap :: (Element mono -> Element mono) -> mono -> mono
	expr_from (Proxy::Proxy root) ast_f ctx $
	 \(ty_f::ty h_f) (Forall_Repr_with_Context f) ->
	expr_from (Proxy::Proxy root) ast_m ctx $
	 \(ty_m::ty h_m) (Forall_Repr_with_Context m) ->
	check_type_fun ex ast ty_f $ \(Type2 Proxy ty_f_a ty_f_b) ->
	check_type0_constraint ex (Proxy::Proxy MonoFunctor) ast ty_m $ \Dict ->
	check_type0_eq ex ast ty_f_a ty_f_b $ \Refl ->
	check_type0_family (Proxy::Proxy Type_Family_MonoElement) ex ast ty_m $ \ty_m_ele ->
	check_type0_eq ex ast ty_f_a ty_m_ele $ \Refl ->
	k ty_m $ Forall_Repr_with_Context $
	 \c -> omap (f c) (m c)