module E.ToHs(compileToHs) where

import Char
import Control.Monad.Identity
import Control.Monad
import Control.Monad.RWS
import Control.Monad.Trans
import Control.Monad.Writer
import Data.Monoid
import System.IO
import Text.PrettyPrint.HughesPJ(render,($$),nest,Doc())
import qualified Data.Traversable as T
import qualified System
import qualified Data.Set as Set

import Data.DeriveTH
import Data.Derive.All
import PackedString
import C.Prims
import C.Arch
import DataConstructors
import Doc.PPrint
import Doc.DocLike
import E.E
import E.FreeVars
import E.Program
import E.Subst
import E.Traverse
import E.Values
import Name.Id
import Name.Name
import Name.Names
import Name.Prim
import Name.VConsts
import Numeric
import Options
import RawFiles(viaghc_hs)
import Support.CanType
import Support.FreeVars
import Util.Gen
import Util.SetLike
import qualified FlagDump as FD

progress str = wdump FD.Progress $  (putErrLn str) >> hFlush stderr


{-# NOINLINE compileToHs #-}
compileToHs :: Program -> IO ()
compileToHs prog = do
    (v,_,Coll { collNames = ns, collPrims = prims }) <- runRWST (fromTM $ transE (programE prog)) emptyEnvironment 1


    let rv = render (text "theRealMain = " <> v)
    let data_decls = render (transDataTable (progDataTable prog) ns) ++ "\n"
    let foreign_decls = render (transForeign $ Set.toList prims) ++ "\n"
    let fn = optOutName options
    let cf = (fn ++ "_code.hs")
    progress ("Writing " ++ show cf)
    name <- System.getProgName
    args <- getArguments
    let argstring = simpleQuote (name:args)
        comm = shellQuote $ ["ghc", "-O", cf, "-o", fn ]
    writeFile cf $ unlines ["-- " ++ argstring,"-- " ++ comm,"",viaghc_hs,render restate,data_decls,rv,"",foreign_decls]
    progress ("Running: " ++ comm)
    r <- System.system comm
    when (r /= System.ExitSuccess) $ fail "Hs code did not compile."
    return ()

cTypeInfoT (ELit LitCons { litAliasFor = Just af }) = cTypeInfoT af
cTypeInfoT (ELit LitCons { litName = n }) | (RawType,t) <- fromName n = cTypeInfo t

cTypeInfo "wchar_t" = ("Char#","C#","Char")
cTypeInfo "HsChar" = ("Char#","C#","Char")
cTypeInfo "HsPtr" =  ("Addr#","Ptr","(Ptr ())")
cTypeInfo "HsFunPtr" =  ("Addr#","Ptr","(Ptr ())")
cTypeInfo n = (if primTypeIsSigned pi then "Int#" else "Word#",v,i) where
        (v,i) = if primTypeIsSigned pi then ('I':nn ++ "#","Int" ++ nn) else ('W':nn ++ "#","Word" ++ nn)
        nn = show $ primTypeSizeOf pi * 8
        Just pi = primitiveInfo n

showCType n = fst3 $ cTypeInfo n

restate = vcat $ map f restated where
    f (n,nn,v) = g (nameType n) <> text v <+> text "=" <+> showTCName nn n
    g DataConstructor = empty
    g TypeConstructor = text "type "
    restated = [
        (dc_Cons,0,"lhc_Cons"),
        (dc_EmptyList,0,"lhc_EmptyList"),
        (tc_List,1,"ListTCon")
        ]



transForeign ps = vcat (map f ps) where
    f (AddrOf s) = text $ "foreign import ccall \"&" ++ unpackPS s ++ "\" addr_" ++ mangleIdent (unpackPS s) ++ " :: Ptr ()"
    f furc@Func { funcName = fn, funcIOLike = True, primArgTypes = as, primRetType = "void" } = ans <$> ans' where
        ans  = text $ "foreign import ccall unsafe \"" ++ unpackPS fn ++ "\" " ++ '_':cfuncname furc ++ " :: " ++ intercalate " -> " (map (snd . snd) vals ++ ["IO ()"])
        ans' = text $ cfuncname furc <+> "w" <+> unwords (fsts vals) <+> " = case _" ++ cfuncname furc <+> intercalate " " [ parens (c <+> a) | (a,(c,_)) <- vals ] <+> "of IO f -> case f w of (# w, _ #) -> w"
        vals = [ ('a':show n,ioInfo a) | a <- as | n <- naturals ]
    f furc@Func { funcName = fn, funcIOLike = True, primArgTypes = as, primRetType = rt' } = ans <$> ans' where
        ans  = text $ "foreign import ccall unsafe \"" ++ unpackPS fn ++ "\" " ++ '_':cfuncname furc ++ " :: " ++ intercalate " -> " (map (snd . snd) vals ++ ["IO " ++ rt])
        ans' = text $ cfuncname furc <+> "w" <+> unwords (fsts vals) <+> " = case _" ++ cfuncname furc <+> intercalate " " [ parens (c <+> a) | (a,(c,_)) <- vals ] <+> "of IO f -> case f w of (# w, " ++ rc ++ " r #) -> (# w, r #)"
        vals = [ ('a':show n,ioInfo a) | a <- as | n <- naturals ]
        (rc,rt) = ioInfo rt'
    f furc@Func { funcName = fn, funcIOLike = False, primArgTypes = as, primRetType = rt' } = ans <$> ans' where
        ans  = text $ "foreign import ccall unsafe \"" ++ unpackPS fn ++ "\" " ++ '_':cfuncname furc ++ " :: " ++ intercalate " -> " (map (snd . snd) vals ++ [rt])
        ans' = text $ cfuncname furc <+> unwords (fsts vals) <+> " = case _" ++ cfuncname furc <+> intercalate " " [ parens (c <+> a) | (a,(c,_)) <- vals ] <+> "of " ++ rc ++ " r -> r"
        vals = [ ('a':show n,ioInfo a) | a <- as | n <- naturals ]
        (rc,rt) = ioInfo rt'
--    f furc@Func { funcName = fn, funcIOLike = False, primArgTypes = as, primRetType = rt } = ans where
--       ans = text $ "foreign import ccall unsafe \"" ++ fn ++ "\" " ++ cfuncname furc ++ " :: " ++ intercalate " -> " (map showCType (as ++ [rt]))
--    f furc@Func { funcName = fn, funcIOLike = True, primArgTypes = as, primRetType = rt } = ans where
--        ans = text $ "foreign import ccall unsafe \"" ++ fn ++ "\" " ++ cfuncname furc ++ " :: " ++ intercalate " -> " ("World__":(map showCType as ++ ["(# World__, " ++ showCType rt ++ " #)"]))
    f n = text "{- Foreign.Error " <+> tshow n <+> text "-}"
    ioInfo n = (x,y) where
        (_,x,y) = cTypeInfo n

transDataTable dataTable ns = vcat (theType:map g (lefts wtd)) where
    wtd =  Set.toList (mconcatMap f (Set.toList ns))
    f (n,_,_) | n `elem` builtIns = Set.empty
    f (n,_,_) | Just _ <- fromUnboxedNameTuple n = Set.empty
    f (n,_,_) | Just _ <- fromTupname n = Set.empty
    f w@(n,nn,tl) = case (nameType n,tl) of
        (DataConstructor,False) -> Set.fromList $ do
            c <- getConstructor n dataTable
            return (Left $ conInhabits c)
        (TypeConstructor,True) -> Set.singleton (Left n)
        (TypeConstructor,False) -> Set.singleton (Right (n,nn))
        (RawType,_) -> Set.empty
        (nt,_) -> error (show (w,nt))
    theType = text "data Type = Char | Int" <+> case rights wtd of
        [] -> empty
        as -> text "|" <+> hcat (punctuate (text " | ") (map tt as))
    tt (n,nn) = hsep (showTCName nn n:replicate nn (text "Type"))

    g n = ans where
        ans = text "data" <+> hsep (showTCName (length $ conSlots con) n:[ text ('x':show i) | _ <- conSlots con | i <- [2::Int,4 ..] ]) <+> dchildren
        Just con = getConstructor n dataTable
        childs = conChildren con
        dchildren | DataNormal [] <- childs = empty
                  | DataNormal childs <- childs  =  text "=" <+> hcat (punctuate (text " | ") (map dc childs))
                  | otherwise = empty
    dc cn = ans where
        ans = hsep (showCName cn: map showSlot (conSlots con))
        Just con = getConstructor cn dataTable
    showSlot (EVar v) = pprint v
    showSlot (ELit LitCons { litArgs = es, litAliasFor = Just af }) = showSlot (foldl eAp af es)
    showSlot (EPi TVr { tvrType = a } b) = parens $ showSlot a <+> text "->" <+> showSlot b
    showSlot (ELit (LitCons { litName = c, litArgs = as })) = showCon c (map showSlot as)
    --builtIns = [tc_Int,tc_Char,dc_Int,dc_Char,rt_int,rt_HsChar,tc_World__,tc_Array__,tc_MutArray__,tc_Ref__,rt_HsPtr]
    builtIns = [tc_Int,tc_Char,dc_Int,dc_Char,tc_World__,tc_Array__,tc_MutArray__,tc_Ref__]

data Environment = Env {
    envParen  :: Bool,
    envType   :: Bool,
    envCoerce :: IdSet
    }

emptyEnvironment = Env {
    envParen  = False,
    envType   = False,
    envCoerce = mempty
    }

data Collect = Coll { collNames :: Set.Set (Name,Int,Bool), collPrims :: Set.Set Prim }
$(derive makeMonoid ''Collect)

newtype TM a = TM { fromTM :: RWST Environment Collect Int IO a }
    deriving(MonadState Int,MonadReader Environment,MonadWriter Collect,Monad,Functor,MonadIO)


mparen xs = do
    Env { envParen = p } <- ask
    x <- local (\e -> e { envParen = True }) xs
    if p then return $ parens x else return x

nparen xs = do local (\e -> e { envParen = True }) xs

noParens x = local (\e -> e { envParen = False }) x

showCon c ts | Just 0 <- fromUnboxedNameTuple c, nameType c == TypeConstructor = text "Nothing"
showCon c ts | Just 0 <- fromUnboxedNameTuple c, nameType c == DataConstructor = text "theNothing"
showCon c ts | Just _ <- fromUnboxedNameTuple c = text "(# " <> hsep (punctuate comma ts) <> text " #)"
showCon c ts | Just _ <- fromTupname c = text "(" <> hsep (punctuate comma ts) <> text ")"
showCon c [] | c == tc_World__ = text "World__"
showCon c [a] | c == tc_Array__ = parens $ text "Array__" <+> a
showCon c [a] | c == tc_MutArray__ = parens $ text "MutArray__" <+> a
showCon c [a] | c == tc_Ref__ = parens $ text "Ref__" <+> a
showCon c [] | (RawType,v) <- fromName c = text $ showCType v
showCon c [] | c == tc_Int = text "Int"
showCon c [] | c == tc_Char = text "Char"
showCon c [] = showTCName 0 c
showCon c ts = parens $ hsep (showTCName (length ts) c:ts)

showTCName n c | nameType c == TypeConstructor = showCName c <> text "_" <> tshow n
showTCName _ c = showCName c


showCName c  | c == dc_Char = text "C#"
showCName c  | c == dc_Int = text "I#"
showCName c = text $ case nameType c of
    DataConstructor -> 'D':mangleIdent (show c)
    TypeConstructor -> 'T':mangleIdent (show c)
    n -> 'U':mangleIdent (show n ++ "_" ++ show c)

transType :: E -> TM Doc
transType e | typeLike e = return $ text "Type"
transType (EPi TVr {tvrType = a } b) = local (\e -> e { envType = True }) $ mparen $ do
    a <- transType a
    b <- transType b
    return $ a <+> text "->" <+> b
transType (ELit LitCons { litArgs = es, litAliasFor = Just af }) = transType (foldl eAp af es)
transType (ELit LitCons { litName = c, litArgs =  ts }) = nparen $ do
    Env { envType = inType } <- ask
    tell mempty { collNames = Set.singleton (c,length ts,inType) }
    ts <- mapM transType ts
    return $ showCon c ts
transType e = return $ text "{- ERROR " <> tshow e <> text " -} Type"

typeLike (ESort EStar) = True
typeLike (EPi TVr { tvrType = a } b) = typeLike a && typeLike b
typeLike _ = False

transE :: E -> TM Doc
transE (EError s _) = mparen $ return (text "error" <+> tshow s)
transE (EError s _) = mparen $ return (text "error__" <+> tshow s <> text "#" <+> text "`seq`" <+> text "undefined")
transE (ELit (LitInt num t)) = case cTypeInfoT t of
    ("Char#",_,_) -> return $ text (show $ chr $ fromIntegral num) <> text "#"
    ("Int#",_,_)  | num < 0 -> mparen $ return $ text (show num) <> text "#"
                  | otherwise -> return $ text (show num) <> text "#"
    ("Addr#",_,_) | num == 0 -> return $ text "nullAddr#"
                  | otherwise -> mparen $ return $ text "int2Addr#" <+> text (show num) <> text "#"
    ("Word#",_,_) -> mparen $ text "int2Word# (" <> tshow num <> text "# )"
transE (ELit LitCons { litName = c, litArgs =  ts }) = nparen $ do
    Env { envType = inType } <- ask
    tell mempty { collNames = Set.singleton (c,length ts,inType) }
    ts <- mapM transE ts
    return $ showCon c ts
transE ee | (e,ts@(_:_)) <- fromLam ee  = mparen $ do
    ts' <- mapM transTVr ts
    e <- noParens $ transE e
    return $ text "\\" <> hsep ts' <+> text "->" <+> e
transE (EVar tvr) = do
    --env <- asks envCoerce
    t <- transTVr tvr
    --case tvrIdent tvr `member` env of
    case hasBoxes (tvrType tvr) of
        False -> return t
        True -> mparen $ return $ text "unsafeCoerce#" <+> t
transE ee | (e,es@(_:_)) <- fromAp ee = mparen $ do
    e <- transE e
    es <- mapM transE es
    return (hsep (e:es))
transE ELetRec { eDefs = ds, eBody = e } = mparen $ do
    --local (\e -> e { envCoerce = envCoerce e `mappend` fromList [ tvrIdent t | (t,_) <- ds, hasBoxes (tvrType t)] }) $ do
    ds' <- flip mapM ds $ \ (tvr,e) -> do
        let (b,bs) = fromLam e
        tt <- noParens $ transType (tvrType tvr)
        t <- transTVr tvr
        bs <- mapM transTVr bs
        e <- case hasBoxes (tvrType tvr) of
            False -> noParens $ transE b
            True -> do
                t <- transE b
                return $ text "unsafeCoerce#" <+> t
        return (t <+> text "::" <+> tt <> semi $$ hsep (t:bs) <+> text "=" <+> e)
    e <- noParens $ transE e
    return (text "let {" $$ nest 4 (vcat (punctuate (text ";") ds')) $$ text "} in" <+> e)
transE ECase { eCaseBind = TVr { tvrIdent = 0, tvrType = tt }, eCaseScrutinee = scrut, eCaseDefault = Just body, eCaseAlts = [] } | isLifted tt = mparen $ do
    scrut <- transE scrut
    body <- transE body
    return (scrut <+> text "`seq`" <+> body)
transE ECase { eCaseBind = bind, eCaseScrutinee = scrut, eCaseDefault = md, eCaseAlts = as } = mparen $ do
    scrut <- noParens $ transE scrut
    let dobind = 0 /= tvrIdent bind
    b <- transTVr bind
    md <- T.mapM transE md
    let md' = flip fmap md $ \e ->  b <+> text "->" <+> if dobind && isLifted (getType bind) then text "seq" <+> b <+> e else e
    as <- mapM (transAlt dobind b) as
    let alts = as ++ maybeToMonad md'
    return (text "case" <+> scrut <+> text "of {" $$ nest 4  (vcat (punctuate semi alts)) $$ text "}")
transE e | Just (e',_) <- from_unsafeCoerce e = mparen $ do
    e' <- transE e'
    return (text "unsafeCoerce#" <+> e')
transE e@(EPrim (APrim (PrimPrim prim) _) args _) = case (unpackPS prim,args) of
    ("dependingOn",[x,_y])   -> transE x  -- XXX
    (fs,args) | Just ghcprim <- lookup fs ghcPrimTable -> mparen $ mapM transE args >>= \args' -> return $ hsep (text ghcprim:args')
    _ -> mparen $ return $ text "error" <+> tshow ("ToHs.Error: " ++ show e)
--transE (EPrim (APrim Operator { primOp = "-", primRetType = rt } _) [x] _) = mparen $ do
--    x <- transE x
--    return (hsep [text "negateInt#",x])
--transE (EPrim (APrim Operator { primOp = op, primRetType = rt } _) [x,y] _) | Just z <- op2Table (op,rt) = mparen $ do
--    x <- transE x
--    y <- transE y
--    return (hsep [text z,x,y])
--transE (EPrim (APrim Operator { primOp = op, primArgTypes = [at,_] } _) [x,y] _) | Just z <- op2TableCmp (op,showCType at) = mparen $ do
--    x <- transE x
--    y <- transE y
--    return $ text "fromBool" <+> (parens $ hsep [text z,x,y])
transE (EPrim (APrim CConst { primConst = ('"':rs) } _) [] _) = return (text ('"':rs) <> text "#")
transE (EPrim (APrim (PrimString ss)  _) [] _) = return (tshow ss <> text "#")
transE (EPrim (APrim PrimTypeInfo { primArgType = at, primTypeInfo = c }  _) [] _) = ans where
    Just pi = primitiveInfo at
    ans = case c of
        PrimSizeOf -> return $ tshow (primTypeSizeOf pi) <> char '#'

transE (EPrim (APrim Peek { primArgType = at } _) [w,x] _) = mparen ans where
    ans = do
        w <- transE w
        x <- transE x
        return (text func <+> x <+> text "0#" <+> w)
    (tt,_,_) = cTypeInfo at
    Just pi = primitiveInfo at
    size = primTypeSizeOf pi * 8
    sign = primTypeIsSigned pi
    func = case tt of
        "Char#" -> "readWideCharOffAddr#"
        "Addr#" -> "readAddrOffAddr#"
        "Int#" -> "readInt" ++ show size ++ "OffAddr#"
        "Word#" -> "readWord" ++ show size ++ "OffAddr#"
transE (EPrim (APrim Peek { primArgType = at } _) [x] (ELit LitCons { litName = n })) = mparen $ ans where
    ans = do x <- ans'; castVal at (show n) x
    ans' = mparen $ do
        x <- transE x
        return (text func <+> x <+> text "0#")
    (tt,_,_) = cTypeInfo at
    Just pi = primitiveInfo at
    size = primTypeSizeOf pi * 8
    sign = primTypeIsSigned pi
    func = case tt of
        "Char#" -> "indexWideCharOffAddr#"
        "Addr#" -> "indexAddrOffAddr#"
        "Int#" -> "indexInt" ++ show size ++ "OffAddr#"
        "Word#" -> "indexWord" ++ show size ++ "OffAddr#"
transE (EPrim (APrim Poke { primArgType = at } _) [w,ptr,v] _) = mparen ans where
    ans = do
        w <- transE w
        ptr <- transE ptr
        v <- transE v
        return (text func <+> ptr <+> text "0#" <+> v <+> w)
    Just pi = primitiveInfo at
    size = primTypeSizeOf pi * 8
    sign = primTypeIsSigned pi
    (tt,_,_) = cTypeInfo at
    func = case tt of
        "Char#" -> "writeWideCharOffAddr#"
        "Addr#" -> "writeAddrOffAddr#"
        "Int#" -> "writeInt" ++ show size ++ "OffAddr#"
        "Word#" -> "writeWord" ++ show size ++ "OffAddr#"
transE (EPrim (APrim (AddrOf addr) _) [] _) = mparen $ do
    tell mempty { collPrims = Set.singleton (AddrOf addr) }
    return (text $ "unPtr addr_" ++ mangleIdent (unpackPS addr))

transE (EPrim (APrim func@Func {} _) xs _) = mparen $ do
    tell mempty { collPrims = Set.singleton func }
    xs <- mapM transE xs
    return (hsep (text (cfuncname func):xs))
--transE (EPrim (APrim cast@CCast { primArgType = at, primRetType = rt } _) [x] _) = mparen $ transE x >>= \x ->  castVal at rt x

transE e = mparen $ return $ text "error" <+> tshow ("ToHs.Error: " ++ show e)

ghcPrimTable = [
    ("newWorld__","newWorld__"),
    ("catch__","catch#"),
    ("raiseIO__","raiseIO#"),
    ("newRef__","newMutVar#"),
    ("readRef__","readMutVar#"),
    ("writeRef__","writeMutVar#"),
    ("newMutArray__","newArray#"),
    ("readArray__","readArray#"),
    ("writeArray__","writeArray#"),
    ("indexArray__","indexArray#"),
    ("unsafeFreezeArray__","unsafeFreezeArray#"),
    ("alloca__","alloca__")
    ]

castVal :: ExtType -> ExtType -> Doc -> TM Doc
castVal at rt x = case (showCType at,showCType rt) of
        (a,b) | a == b -> return x
        z | Just co <- lookup z coercions -> mparen $ return (text co <+> x)
        xs -> fail $ "unknown coercion: " ++ show xs
    where
    coercions = [
        (("Int#","Char#"),"chr#"),
        (("Char#","Int#"),"ord#"),
        (("Addr#","Int#"),"addr2Int#"),
        (("Int#","Addr#"),"int2Addr#"),
        (("Word#","Int#"),"word2Int#"),
        (("Int#","Word#"),"int2Word#"),
        (("Char#","Word#"),"char2Word__"),
        (("Word#","Char#"),"word2Char__"),
        (("Addr#","Word#"),"addr2Word__"),
        (("Word#","Addr#"),"word2Addr__")
        ]

cfuncname Func { funcName = fn, funcIOLike = iol, primArgTypes = as, primRetType = r  } =  text $ ("func_" ++ (if iol then "io" else "pure") ++ "_" ++ unpackPS fn ++ intercalate "_" (r:as))

hasBoxes e = or $ execWriter (f e) where
    f e | e == tBox = tell [True] >> return e
    f e = emapEGH f f f e

op2Table (op,rt) = lookup (showCType rt) table >>= lookup op where
    table = [ ("Int#",intTable),("Word#",wordTable),("Addr#",addrTable)]
    intTable = [
        ("+","(+#)"),
        ("-","(-#)"),
        ("*","(*#)"),
        ("%","remInt#"),
        ("/","quotInt#")
        ]
    wordTable = [
        ("+","plusWord#"),
        ("-","minusWord#"),
        ("*","timesWord#"),
        ("%","remWord#"),
        ("/","quotWord#")
        ]
    addrTable = [ ("+","plusAddr__") ]

op2TableCmp (op,rt) = lookup rt table >>= lookup op where
    table = [ ("Int#",intTable), ("Char#",charTable), ("Addr#",addrTable),("Word#",wordTable)]
    intTable = [
        (">","(>#)"),
        ("==","(==#)"),
        ("<","(<#)"),
        (">=","(>=#)"),
        ("<=","(<=#)")
        ]
    charTable = [
        (">","gtChar#"),
        ("==","eqChar#"),
        ("<","ltChar#"),
        (">=","gteChar#"),
        ("<=","lteChar#")
        ]
    addrTable = [
        (">","gtAddr#"),
        ("==","eqAddr#"),
        ("<","ltAddr#"),
        (">=","gteAddr#"),
        ("<=","lteAddr#")
        ]
    wordTable = [
        (">","gtWord#"),
        ("==","eqWord#"),
        ("<","ltWord#"),
        (">=","gteWord#"),
        ("<=","lteWord#")
        ]

transAlt :: Bool -> Doc -> Alt E -> TM Doc
transAlt dobind b (Alt LitInt { litNumber = i, litType = tt } e) = do
    let (t,_,_) = cTypeInfoT tt
    e <- noParens $ transE e
    case t of
        "Int#" -> return $ (if dobind then b <> char '@' else empty) <> tshow i <> text "#" <+> text "->" <+> e
        "Char#" -> return $ (if dobind then b <> char '@' else empty) <> text (show $ chr $ fromIntegral i) <> text "#" <+> text "->" <+> e
        _ -> do
            let bvar = if dobind then b else text "_bvar"
                Just eq = op2TableCmp ("==",t)
            v <- transE (ELit (LitInt i tt))
            return (bvar <+> text "|" <+> text eq <+> bvar <+> v <+> text "->" <+> e)
transAlt dobind b (Alt LitCons { litName = c, litArgs = ts } e) = do
    tell mempty { collNames = Set.singleton (c,length ts,False) }  -- XXX this shouldn't be needed
    ts <- mapM transTVr ts
    e <- noParens $ transE e
    return ( (if dobind then b <> char '@' else empty) <> showCon c ts <+> text "->" <+> e)




transTVr :: TVr -> TM Doc
transTVr TVr { tvrIdent = 0 } = return $ char '_'
transTVr tvr = return (text $ 'v':mangleIdent (pprint tvr))

mangleIdent xs =  concatMap f xs where
        f '.' = "__"
        f '@' = "_a"
        f ',' = "_c"
        f '(' = "_L"
        f ')' = "_R"
        f '$' = "_d"
        f '%' = "_P"
        f '#' = "_h"
        f '/' = "_s"
        f '=' = "_e"
        f '+' = "_p"
        f '-' = "_m"
        f '!' = "_b"
        f '>' = "_r"
        f '<' = "_l"
        f '\'' = "_t"
        f '_' = "_u"
        f c | isAlphaNum c = [c]
        f c = '_':'x':showHex (ord c) ""