% (c) The University of Glasgow 2001-2006 % \begin{code}

    module MkExternalCore (
    	emitExternalCore
    ) where

    #include "HsVersions.h"

    import qualified ExternalCore as C
    import Module
    import CoreSyn
    import HscTypes
    import TyCon
    import TypeRep
    import Type
    import PprExternalCore () -- Instances
    import DataCon
    import Coercion
    import Var
    import IdInfo
    import Literal
    import Name
    import Outputable
    import Encoding
    import ForeignCall
    import DynFlags
    import FastString

    import Data.Char
    import System.IO

    emitExternalCore :: DynFlags -> CgGuts -> IO ()
    emitExternalCore dflags cg_guts
     | dopt Opt_EmitExternalCore dflags
     = (do handle <- openFile corename WriteMode
           hPutStrLn handle (show (mkExternalCore cg_guts))
           hClose handle)
       `catch` (\_ -> pprPanic "Failed to open or write external core output file"
                               (text corename))
       where corename = extCoreName dflags
    emitExternalCore _ _
     | otherwise
     = return ()

    -- Reinventing the Reader monad; whee.
    newtype CoreM a = CoreM (CoreState -> (CoreState, a))
    type CoreState = Module
    instance Monad CoreM where
      (CoreM m) >>= f = CoreM (\ s -> case m s of
                                        (s',r) -> case f r of
                                                    CoreM f' -> f' s')
      return x = CoreM (\ s -> (s, x))
    runCoreM :: CoreM a -> CoreState -> a
    runCoreM (CoreM f) s = snd $ f s
    ask :: CoreM CoreState
    ask = CoreM (\ s -> (s,s))

    mkExternalCore :: CgGuts -> C.Module
    -- The ModGuts has been tidied, but the implicit bindings have
    -- not been injected, so we have to add them manually here
    -- We don't include the strange data-con *workers* because they are
    -- implicit in the data type declaration itself
    mkExternalCore (CgGuts {cg_module=this_mod, cg_tycons = tycons,
                            cg_binds = binds})
    {- Note that modules can be mutually recursive, but even so, we
       print out dependency information within each module. -}
      = C.Module mname tdefs (runCoreM (mapM (make_vdef True) binds) this_mod)
      where
        mname  = make_mid this_mod
        tdefs  = foldr collect_tdefs [] tycons

    collect_tdefs :: TyCon -> [C.Tdef] -> [C.Tdef]
    collect_tdefs tcon tdefs
      | isAlgTyCon tcon = tdef: tdefs
      where
        tdef | isNewTyCon tcon =
                    C.Newtype (qtc tcon)
                      (case newTyConCo_maybe tcon of
                         Just co -> qtc co
                         Nothing       -> pprPanic ("MkExternalCore: newtype tcon\
                                           should have a coercion: ") (ppr tcon))
                      (map make_tbind tyvars)
                      (make_ty (snd (newTyConRhs tcon)))
             | otherwise =
                    C.Data (qtc tcon) (map make_tbind tyvars)
                       (map make_cdef (tyConDataCons tcon))
        tyvars = tyConTyVars tcon

    collect_tdefs _ tdefs = tdefs

    qtc :: TyCon -> C.Qual C.Tcon
    qtc = make_con_qid . tyConName

    make_cdef :: DataCon -> C.Cdef
    make_cdef dcon =  C.Constr dcon_name existentials tys
      where
        dcon_name    = make_qid False False (dataConName dcon)
        existentials = map make_tbind ex_tyvars
        ex_tyvars    = dataConExTyVars dcon
        tys 	 = map make_ty (dataConRepArgTys dcon)

    make_tbind :: TyVar -> C.Tbind
    make_tbind tv = (make_var_id (tyVarName tv), make_kind (tyVarKind tv))

    make_vbind :: Var -> C.Vbind
    make_vbind v = (make_var_id  (Var.varName v), make_ty (varType v))

    make_vdef :: Bool -> CoreBind -> CoreM C.Vdefg
    make_vdef topLevel b =
      case b of
        NonRec v e -> f (v,e)     >>= (return . C.Nonrec)
        Rec ves    -> mapM f ves  >>= (return . C.Rec)
      where
      f :: (CoreBndr,CoreExpr) -> CoreM C.Vdef
      f (v,e) = do
              localN <- isALocal vName
              let local = not topLevel || localN
              rhs <- make_exp e
              -- use local flag to determine where to add the module name
              return (local, make_qid local True vName, make_ty (varType v),rhs)
      	where vName = Var.varName v

    make_exp :: CoreExpr -> CoreM C.Exp
    make_exp (Var v) = do
      let vName = Var.varName v
      isLocal <- isALocal vName
      return $
         case idDetails v of
           FCallId (CCall (CCallSpec (StaticTarget nm _) callconv _))
               -> C.External (unpackFS nm) (showSDoc (ppr callconv)) (make_ty (varType v))
           FCallId (CCall (CCallSpec DynamicTarget     callconv _))
               -> C.DynExternal            (showSDoc (ppr callconv)) (make_ty (varType v))
           -- Constructors are always exported, so make sure to declare them
           -- with qualified names
           DataConWorkId _ -> C.Var (make_var_qid False vName)
           DataConWrapId _ -> C.Var (make_var_qid False vName)
           _ -> C.Var (make_var_qid isLocal vName)
    make_exp (Lit (MachLabel s _ _)) = return $ C.Label (unpackFS s)
    make_exp (Lit l) = return $ C.Lit (make_lit l)
    make_exp (App e (Type t)) = make_exp e >>= (\ b -> return $ C.Appt b (make_ty t))
    make_exp (App e1 e2) = do
       rator <- make_exp e1
       rand <- make_exp e2
       return $ C.App rator rand
    make_exp (Lam v e) | isTyCoVar v = make_exp e >>= (\ b ->
                                        return $ C.Lam (C.Tb (make_tbind v)) b)
    make_exp (Lam v e) | otherwise = make_exp e >>= (\ b ->
                                        return $ C.Lam (C.Vb (make_vbind v)) b)
    make_exp (Cast e co) = make_exp e >>= (\ b -> return $ C.Cast b (make_ty co))
    make_exp (Let b e) = do
      vd   <- make_vdef False b
      body <- make_exp e
      return $ C.Let vd body
    make_exp (Case e v ty alts) = do
      scrut <- make_exp e
      newAlts  <- mapM make_alt alts
      return $ C.Case scrut (make_vbind v) (make_ty ty) newAlts
    make_exp (Note (SCC _) e) = make_exp e >>= (return . C.Note "SCC") -- temporary
    make_exp (Note (CoreNote s) e) = make_exp e >>= (return . C.Note s)  -- hdaume: core annotations
    make_exp _ = error "MkExternalCore died: make_exp"

    make_alt :: CoreAlt -> CoreM C.Alt
    make_alt (DataAlt dcon, vs, e) = do
        newE <- make_exp e
        return $ C.Acon (make_con_qid (dataConName dcon))
               (map make_tbind tbs)
               (map make_vbind vbs)
    	   newE
    	where (tbs,vbs) = span isTyCoVar vs
    make_alt (LitAlt l,_,e)   = make_exp e >>= (return . (C.Alit (make_lit l)))
    make_alt (DEFAULT,[],e)   = make_exp e >>= (return . C.Adefault)
    -- This should never happen, as the DEFAULT alternative binds no variables,
    -- but we might as well check for it:
    make_alt a@(DEFAULT,_ ,_) = pprPanic ("MkExternalCore: make_alt: DEFAULT "
                 ++ "alternative had a non-empty var list") (ppr a)

    make_lit :: Literal -> C.Lit
    make_lit l =
      case l of
        -- Note that we need to check whether the character is "big".
        -- External Core only allows character literals up to '\xff'.
        MachChar i | i <= chr 0xff -> C.Lchar i t
        -- For a character bigger than 0xff, we represent it in ext-core
        -- as an int lit with a char type.
        MachChar i             -> C.Lint (fromIntegral $ ord i) t
        MachStr s -> C.Lstring (unpackFS s) t
        MachNullAddr -> C.Lint 0 t
        MachInt i -> C.Lint i t
        MachInt64 i -> C.Lint i t
        MachWord i -> C.Lint i t
        MachWord64 i -> C.Lint i t
        MachFloat r -> C.Lrational r t
        MachDouble r -> C.Lrational r t
        _ -> error "MkExternalCore died: make_lit"
      where
        t = make_ty (literalType l)

    -- Expand type synonyms, then convert.
    make_ty :: Type -> C.Ty                 -- Be sure to expand types recursively!
                                            -- example: FilePath ~> String ~> [Char]
    make_ty t | Just expanded <- tcView t = make_ty expanded
    make_ty t = make_ty' t

    -- note calls to make_ty so as to expand types recursively
    make_ty' :: Type -> C.Ty
    make_ty' (TyVarTy tv)    	 = C.Tvar (make_var_id (tyVarName tv))
    make_ty' (AppTy t1 t2) 		 = C.Tapp (make_ty t1) (make_ty t2)
    make_ty' (FunTy t1 t2) 		 = make_ty (TyConApp funTyCon [t1,t2])
    make_ty' (ForAllTy tv t) 	 = C.Tforall (make_tbind tv) (make_ty t)
    make_ty' (TyConApp tc ts) 	 = make_tyConApp tc ts

    -- Newtypes are treated just like any other type constructor; not expanded
    -- Reason: predTypeRep does substitution and, while substitution deals
    -- 	   correctly with name capture, it's only correct if you see the uniques!
    --	   If you just see occurrence names, name capture may occur.
    -- Example: newtype A a = A (forall b. b -> a)
    --	    test :: forall q b. q -> A b
    --	    test _ = undefined
    -- 	Here the 'a' gets substituted by 'b', which is captured.
    -- Another solution would be to expand newtypes before tidying; but that would
    -- expose the representation in interface files, which definitely isn't right.
    -- Maybe CoreTidy should know whether to expand newtypes or not?

    make_ty' (PredTy p)	= make_ty (predTypeRep p)

    make_tyConApp :: TyCon -> [Type] -> C.Ty
    make_tyConApp tc [t1, t2] | tc == transCoercionTyCon =
      C.TransCoercion (make_ty t1) (make_ty t2)
    make_tyConApp tc [t]      | tc == symCoercionTyCon =
      C.SymCoercion (make_ty t)
    make_tyConApp tc [t1, t2] | tc == unsafeCoercionTyCon =
      C.UnsafeCoercion (make_ty t1) (make_ty t2)
    make_tyConApp tc [t]      | tc == leftCoercionTyCon =
      C.LeftCoercion (make_ty t)
    make_tyConApp tc [t]      | tc == rightCoercionTyCon =
      C.RightCoercion (make_ty t)
    make_tyConApp tc [t1, t2] | tc == instCoercionTyCon =
      C.InstCoercion (make_ty t1) (make_ty t2)
    -- this fails silently if we have an application
    -- of a wired-in coercion tycon to the wrong number of args.
    -- Not great...
    make_tyConApp tc ts =
      foldl C.Tapp (C.Tcon (qtc tc))
    	    (map make_ty ts)

    make_kind :: Kind -> C.Kind
    make_kind (PredTy p) | isEqPred p = C.Keq (make_ty t1) (make_ty t2)
        where (t1, t2) = getEqPredTys p
    make_kind (FunTy k1 k2)  = C.Karrow (make_kind k1) (make_kind k2)
    make_kind k
      | isLiftedTypeKind k   = C.Klifted
      | isUnliftedTypeKind k = C.Kunlifted
      | isOpenTypeKind k     = C.Kopen
    make_kind _ = error "MkExternalCore died: make_kind"

    {- Id generation. -}

    make_id :: Bool -> Name -> C.Id
    -- include uniques for internal names in order to avoid name shadowing
    make_id _is_var nm = ((occNameString . nameOccName) nm)
      ++ (if isInternalName nm then (show . nameUnique) nm else "")

    make_var_id :: Name -> C.Id
    make_var_id = make_id True

    -- It's important to encode the module name here, because in External Core,
    -- base:GHC.Base => base:GHCziBase
    -- We don't do this in pprExternalCore because we
    -- *do* want to keep the package name (we don't want baseZCGHCziBase,
    -- because that would just be ugly.)
    -- SIGH.
    -- We encode the package name as well.
    make_mid :: Module -> C.Id
    -- Super ugly code, but I can't find anything else that does quite what I
    -- want (encodes the hierarchical module name without encoding the colon
    -- that separates the package name from it.)
    make_mid m = showSDoc $
                  (text $ zEncodeString $ packageIdString $ modulePackageId m)
                  <> text ":"
                  <> (pprEncoded $ pprModuleName $ moduleName m)
         where pprEncoded = pprCode CStyle

    make_qid :: Bool -> Bool -> Name -> C.Qual C.Id
    make_qid force_unqual is_var n = (mname,make_id is_var n)
        where mname =
               case nameModule_maybe n of
                Just m | not force_unqual -> make_mid m
                _ -> ""

    make_var_qid :: Bool -> Name -> C.Qual C.Id
    make_var_qid force_unqual = make_qid force_unqual True

    make_con_qid :: Name -> C.Qual C.Id
    make_con_qid = make_qid False False

    -------
    isALocal :: Name -> CoreM Bool
    isALocal vName = do
      modName <- ask
      return $ case nameModule_maybe vName of
                 -- Not sure whether isInternalName corresponds to "local"ness
                 -- in the External Core sense; need to re-read the spec.
                 Just m | m == modName -> isInternalName vName
                 _                     -> False

\end{code}