{-# LANGUAGE Arrows, ExistentialQuantification, GADTs, Rank2Types, FlexibleContexts, ScopedTypeVariables
    , EmptyDataDecls, MultiParamTypeClasses, FlexibleInstances, OverlappingInstances, FunctionalDependencies, UndecidableInstances
  #-}

module Language.Grammars.SyntaxMacros where

import Language.AbstractSyntax.TTTAS
import Control.Arrow

import qualified UU.Parsing as UU
import Language.Grammars.SyntaxMacros.Scanner

import Language.Grammars.Grammar 
import Language.Grammars.Transformations.RemoveFix
import Language.Grammars.Transformations.RemoveEmpties
import Language.Grammars.Transformations.LeftCorner


type GramTrafo = Trafo Unit (Productions TL)
type ExtGram      env  start  nts   
           = GramTrafo env  ()   (Export start nts env)
type SyntaxMacro  env  start  nts  start' nts'  
           = GramTrafo env  (Export start nts env)  (Export start' nts' env)

data Export start nts env = Export (Symbol start TNonT env) (nts env)

-- add a new non-terminal to the grammar
addNT  ::  GramTrafo env (ListProd TL env a) (Symbol a TNonT env)
addNT  =  proc  p -> do 
                r  <- newSRef -< prod p
                returnA -< Nont r


-- add productions to an existing non-terminal
addProds  ::  GramTrafo  env 
                         (Symbol a TNonT env, ListProd TL env a) ()
addProds  = proc (nont, prds) -> do
      updateFinalEnv  -< 
         updateEnv (\ps -> PS $ (unPP prds) ++ (unPS ps)) (getRefNT nont)

 
-- close the grammar
closeGram :: (forall env. ExtGram  env a nts) 
                -> Grammar a 
closeGram prds  = case runTrafo prds Unit () of
     Result _ (Export (Nont r) _) gram 
            -> (leftCorner . removeEmpties . removeFix) $ Grammar r gram

extendGram  ::  (NTRecord (nts env), NTRecord (nts' env))  
            =>  ExtGram env start nts 
                -> SyntaxMacro env start nts start' nts' 
                -> ExtGram env start' nts'
extendGram g sm = g >>> sm

(<++>)      ::  (NTRecord (nts env), NTRecord (nts' env))  
            =>  ExtGram env start nts 
                -> SyntaxMacro env start nts start' nts' 
                -> ExtGram env start' nts'

(<++>) = extendGram

exportNTs ::  NTRecord (nts env) => GramTrafo env (Export start nts env) (Export start nts env)
exportNTs = returnA


-- extensible record


data  NTCons nt v l env  = NTCons (LSPair nt v TNonT env) (l env)
data  NTNil         env  = NTNil

class NTRecord r 
instance NTRecord (NTNil env)
instance (NTRecord (l env), NotDuplicated nt (l env)) => NTRecord (NTCons nt v l env)


class Fail err

data Duplicated nt

class NotDuplicated nt r
instance NotDuplicated nt (NTNil env)
instance Fail (Duplicated nt)      => NotDuplicated nt  (NTCons nt v l env) -- using overlapping
instance NotDuplicated nt1 (l env) => NotDuplicated nt1 (NTCons nt2 v l env)

ntNil :: NTNil env
ntNil = NTNil



infixr 4 ^| 
(^|) :: NTRecord (NTCons nt a l env) => LSPair nt a TNonT env -> l env -> NTCons nt a l env
(^|) = NTCons


class GetNT nt r v | nt r -> v where
  getNT :: nt -> r -> v

data NotFound nt

instance Fail (NotFound nt) => GetNT nt (NTNil env) r where
 getNT = undefined
instance GetNT nt  (NTCons nt v l env) (Symbol v TNonT env) where -- using overlapping
 getNT _     (NTCons f _)    = symLSPair f
instance GetNT nt1 (l env) r => GetNT nt1 (NTCons nt2 v l env) r where
 getNT nont  (NTCons _ l)    = getNT nont l

instance GetNT nt (nts env) r => GetNT nt (Export start nts env) r where
 getNT nont  (Export _ nts)  = getNT nont nts

getStart :: Export start nts env ->  (Symbol start TNonT env)
getStart (Export start _) = start

exportList :: Symbol start TNonT env -> (NTNil env -> nts env) -> Export start nts env
exportList r l = Export r $ l ntNil

export  ::  (NTRecord (l env), NotDuplicated nt (l env))
        =>  nt -> Symbol a TNonT env 
        -> l env ->  NTCons nt a l env
export l nont = (^|) (l ^= nont) 

-- COMPILE --------------------------------------------------------------------

pInt            ::   UU.Parser Token Int
pChr            ::   UU.Parser Token Char
pCon            ::   UU.Parser Token String
pVar            ::   UU.Parser Token String
pOp             ::   UU.Parser Token String

pChr            =    head UU.<$> pChar
pInt            =    read UU.<$> pInteger
pCon            =    id UU.<$> pConid
pVar            =    id UU.<$> pVarid
pOp             =    id UU.<$> pVarsym

pTerm           ::  (UU.IsParser p Token) 
                =>  String -> p DTerm
pTerm t         =   pKey t

newtype Const f a s = C {unC :: f a}


compile :: Grammar a -> UU.Parser Token a
compile (Grammar (start :: Ref a env) rules) 
                       = unC (lookupEnv start result)
  where  result  =  
          mapEnv 
          (\ (PS ps) -> C (foldr1 (UU.<|>) [ comp p | p <- ps]))
          rules

         comp :: forall t . Prod TL t env -> UU.Parser Token t

         comp (Star     x y)   = comp x UU.<*>   comp y
         comp (FlipStar x y)   = comp x UU.<**>  comp y
         comp (Pure     x)     = UU.pLow x

         comp (Sym (Term t))   = pTerm t
         comp (Sym (Nont n))   = unC (lookupEnv n result)

         comp (Sym TermInt)    = pInt
         comp (Sym TermChar)   = pChr
         comp (Sym TermVarid)  = pVar
         comp (Sym TermConid)  = pCon
         comp (Sym TermOp)     = pOp

         comp (Fix _)          = error "This shouldn't be happening!"

mapEnv  ::  (forall a . f a s -> g a s)  
        ->  Env f s env -> Env g s env
mapEnv  _ Empty       = Empty
mapEnv  f (Ext r v)   = Ext (mapEnv f r) (f v)


-- PARSE ----------------------------------------------------------------------

type ParseMsg = UU.Message Token (Maybe Token)

data ParseResult a = Ok  a
                   | Rep a [ParseMsg] 
      deriving Show

parse :: UU.Parser Token a -> [Token] -> ParseResult a
parse p input = case rparse p input of
                  (a,[]  ) -> Ok a
                  (a,msgs) -> Rep a msgs


rparse :: UU.Parser Token a -> [Token] -> (a, [ParseMsg])
rparse p input = let (UU.Pair a _,msgs) =  eval (UU.parse p input)
                 in (a,msgs)
 where eval :: UU.Steps a Token (Maybe Token) -> (a, [ParseMsg])
       eval (UU.OkVal v        r) = let (a,msgs) = v `seq` eval r 
                                    in  (v a,msgs)
       eval (UU.Ok             r) = eval r
       eval (UU.Cost  _        r) = eval  r
       eval (UU.StRepair _ msg r) = let (v,msgs) = eval r 
                                    in  (v,msg:msgs)
       eval (UU.Best _   r     _) = eval  r
       eval (UU.NoMoreSteps v   ) = (v,[])