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