{-# LANGUAGE UndecidableInstances #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
-- | Symantic for 'Alternative'.
module Language.Symantic.Lib.Alternative where

import Control.Applicative (Alternative)
import Control.Monad (liftM2)
import Data.Proxy
import Data.Type.Equality ((:~:)(Refl))
import Prelude hiding (Functor(..), (<$>), id, const)
import qualified Control.Applicative as Alternative
import qualified Data.Function as Fun

import Language.Symantic.Parsing hiding (Alter(..))
import Language.Symantic.Typing
import Language.Symantic.Compiling
import Language.Symantic.Lib.Lambda
import Language.Symantic.Lib.Functor (Sym_Functor(..))
import Language.Symantic.Interpreting
import Language.Symantic.Transforming

-- * Class 'Sym_Alternative'
class Sym_Functor term => Sym_Alternative term where
	empty :: Alternative f => term (f a)
	(<|>) :: Alternative f => term (f a) -> term (f a) -> term (f a)
	infixl 3 <|>
	
	default empty :: (Trans t term, Alternative f) => t term (f a)
	default (<|>) :: (Trans t term, Alternative f)
	 => t term (f a) -> t term (f a) -> t term (f a)
	
	empty = trans_lift empty
	(<|>) = trans_map2 (<|>)

type instance Sym_of_Iface (Proxy Alternative) = Sym_Alternative
type instance TyConsts_of_Iface (Proxy Alternative) = Proxy Alternative ': TyConsts_imported_by (Proxy Alternative)
type instance TyConsts_imported_by (Proxy Alternative) = '[]

instance Sym_Alternative HostI where
	empty = HostI Alternative.empty
	(<|>) = liftM2 (Alternative.<|>)
instance Sym_Alternative TextI where
	empty = textI0 "empty"
	(<|>) = textI_infix "<|>" (infixL 3)
instance (Sym_Alternative r1, Sym_Alternative r2) => Sym_Alternative (DupI r1 r2) where
	empty = dupI0 @Sym_Alternative empty
	(<|>) = dupI2 @Sym_Alternative (<|>)

instance
 ( Read_TyNameR TyName cs rs
 , Inj_TyConst cs Alternative
 ) => Read_TyNameR TyName cs (Proxy Alternative ': rs) where
	read_TyNameR _cs (TyName "Alternative") k = k (ty @Alternative)
	read_TyNameR _rs raw k = read_TyNameR (Proxy @rs) raw k
instance Show_TyConst cs => Show_TyConst (Proxy Alternative ': cs) where
	show_TyConst TyConstZ{} = "Alternative"
	show_TyConst (TyConstS c) = show_TyConst c

instance Proj_TyConC cs (Proxy Alternative)
data instance TokenT meta (ts::[*]) (Proxy Alternative)
 = Token_Term_Alternative_empty (EToken meta '[Proxy Token_Type]) (EToken meta '[Proxy Token_Type])
 | Token_Term_Alternative_alt   (EToken meta ts)
deriving instance (Eq meta, Eq_Token meta ts) => Eq (TokenT meta ts (Proxy Alternative))
deriving instance (Show meta, Show_Token meta ts) => Show (TokenT meta ts (Proxy Alternative))

instance -- CompileI
 ( Read_TyName TyName cs
 , Inj_TyConst        cs Alternative
 , Inj_TyConst        cs (->)
 , Proj_TyCon         cs
 , Compile cs is
 ) => CompileI cs is (Proxy Alternative) where
	compileI tok ctx k =
		case tok of
		 Token_Term_Alternative_empty tok_ty_f tok_ty_a ->
			-- empty :: Alternative f => f a
			compile_Type tok_ty_f $ \(ty_f::Type cs f) ->
			compile_Type tok_ty_a $ \(ty_a::Type cs a) ->
			check_Kind
			 (At Nothing $ SKiType `SKiArrow` SKiType)
			 (At (Just tok_ty_f) $ kind_of ty_f) $ \Refl ->
			check_TyCon (At (Just tok_ty_f) (ty @Alternative :$ ty_f)) $ \TyCon ->
			check_Kind
			 (At Nothing $ SKiType)
			 (At (Just tok_ty_a) $ kind_of ty_a) $ \Refl ->
			k (ty_f :$ ty_a) $ Term $
			 Fun.const empty
		 Token_Term_Alternative_alt tok_fl ->
			-- (<|>) :: Alternative f => f a -> f a -> f a
			compile tok_fl ctx $ \ty_fa (Term fl) ->
			check_TyCon1 (ty @Alternative)
			 (At (Just tok_fl) ty_fa) $ \Refl TyCon _ty_f _ty_a ->
			k (ty_fa ~> ty_fa) $ Term $
			 \c -> lam $ \fr -> (<|>) (fl c) fr
instance -- TokenizeT
 Inj_Token meta ts Alternative =>
 TokenizeT meta ts (Proxy Alternative) where
	tokenizeT _t = mempty
	 { tokenizers_infix = tokenizeTMod []
		 [ (TeName "empty",) ProTok_Term
			 { protok_term = \meta -> ProTokPi $ \f -> ProTokPi $ \a ->
				ProTok $ inj_EToken meta $ Token_Term_Alternative_empty f a
			 , protok_fixity = infixN5
			 }
		 , tokenize1 "<|>" (infixL 3) Token_Term_Alternative_alt
		 ]
	 }
instance Gram_Term_AtomsT meta ts (Proxy Alternative) g