    -- (c) The University of Glasgow 2002-2006

    {-# LANGUAGE CPP, RankNTypes #-}

    module IfaceEnv (
            newGlobalBinder, newInteractiveBinder,
            externaliseName,
            lookupIfaceTop,
            lookupOrig, lookupOrigNameCache, extendNameCache,
            newIfaceName, newIfaceNames,
            extendIfaceIdEnv, extendIfaceTyVarEnv,
            tcIfaceLclId, tcIfaceTyVar, lookupIfaceVar,
            lookupIfaceTyVar, extendIfaceEnvs,

            ifaceExportNames,

            -- Name-cache stuff
            allocateGlobalBinder,
            initNameCache, updNameCache,
            mkNameCacheUpdater, NameCacheUpdater(..)
       ) where

    #include "HsVersions.h"

    import TcRnMonad
    import TysWiredIn
    import HscTypes
    import Type
    import Var
    import Name
    import Avail
    import Module
    import FastString
    import FastStringEnv
    import IfaceType
    import UniqSupply
    import SrcLoc
    import Util

    import Outputable
    import Data.List     ( partition )

    {-
    *********************************************************
    *                                                      *
            Allocating new Names in the Name Cache
    *                                                      *
    *********************************************************

    Note [The Name Cache]
    ~~~~~~~~~~~~~~~~~~~~~
    The Name Cache makes sure that, during any invocation of GHC, each
    External Name "M.x" has one, and only one globally-agreed Unique.

    * The first time we come across M.x we make up a Unique and record that
      association in the Name Cache.

    * When we come across "M.x" again, we look it up in the Name Cache,
      and get a hit.

    The functions newGlobalBinder, allocateGlobalBinder do the main work.
    When you make an External name, you should probably be calling one
    of them.
    -}

    newGlobalBinder :: Module -> OccName -> SrcSpan -> TcRnIf a b Name
    -- Used for source code and interface files, to make the
    -- Name for a thing, given its Module and OccName
    -- See Note [The Name Cache]
    --
    -- The cache may already already have a binding for this thing,
    -- because we may have seen an occurrence before, but now is the
    -- moment when we know its Module and SrcLoc in their full glory

    newGlobalBinder mod occ loc
      = do { mod `seq` occ `seq` return ()    -- See notes with lookupOrig
           ; name <- updNameCache $ \name_cache ->
                     allocateGlobalBinder name_cache mod occ loc
           ; traceIf (text "newGlobalBinder" <+>
                      (vcat [ ppr mod <+> ppr occ <+> ppr loc, ppr name]))
           ; return name }

    newInteractiveBinder :: HscEnv -> OccName -> SrcSpan -> IO Name
    -- Works in the IO monad, and gets the Module
    -- from the interactive context
    newInteractiveBinder hsc_env occ loc
     = do { let mod = icInteractiveModule (hsc_IC hsc_env)
           ; updNameCacheIO hsc_env $ \name_cache ->
             allocateGlobalBinder name_cache mod occ loc }

    allocateGlobalBinder
      :: NameCache
      -> Module -> OccName -> SrcSpan
      -> (NameCache, Name)
    -- See Note [The Name Cache]
    allocateGlobalBinder name_supply mod occ loc
      = case lookupOrigNameCache (nsNames name_supply) mod occ of
            -- A hit in the cache!  We are at the binding site of the name.
            -- This is the moment when we know the SrcLoc
            -- of the Name, so we set this field in the Name we return.
            --
            -- Then (bogus) multiple bindings of the same Name
            -- get different SrcLocs can can be reported as such.
            --
            -- Possible other reason: it might be in the cache because we
            --      encountered an occurrence before the binding site for an
            --      implicitly-imported Name.  Perhaps the current SrcLoc is
            --      better... but not really: it'll still just say 'imported'
            --
            -- IMPORTANT: Don't mess with wired-in names.
            --            Their wired-in-ness is in their NameSort
            --            and their Module is correct.

            Just name | isWiredInName name
                      -> (name_supply, name)
                      | otherwise
                      -> (new_name_supply, name')
                      where
                        uniq            = nameUnique name
                        name'           = mkExternalName uniq mod occ loc
                                          -- name' is like name, but with the right SrcSpan
                        new_cache       = extendNameCache (nsNames name_supply) mod occ name'
                        new_name_supply = name_supply {nsNames = new_cache}

            -- Miss in the cache!
            -- Build a completely new Name, and put it in the cache
            _ -> (new_name_supply, name)
                      where
                        (uniq, us')     = takeUniqFromSupply (nsUniqs name_supply)
                        name            = mkExternalName uniq mod occ loc
                        new_cache       = extendNameCache (nsNames name_supply) mod occ name
                        new_name_supply = name_supply {nsUniqs = us', nsNames = new_cache}

    ifaceExportNames :: [IfaceExport] -> TcRnIf gbl lcl [AvailInfo]
    ifaceExportNames exports = return exports

    -- | Look up the 'Name' for a given 'Module' and 'OccName'.
    -- Consider alternately using 'lookupIfaceTop' if you're in the 'IfL' monad
    -- and 'Module' is simply that of the 'ModIface' you are typechecking.
    lookupOrig :: Module -> OccName -> TcRnIf a b Name
    lookupOrig mod occ
      = do  {       -- First ensure that mod and occ are evaluated
                    -- If not, chaos can ensue:
                    --      we read the name-cache
                    --      then pull on mod (say)
                    --      which does some stuff that modifies the name cache
                    -- This did happen, with tycon_mod in TcIface.tcIfaceAlt (DataAlt..)
              mod `seq` occ `seq` return ()
    --      ; traceIf (text "lookup_orig" <+> ppr mod <+> ppr occ)

            ; updNameCache $ \name_cache ->
              case lookupOrigNameCache (nsNames name_cache) mod occ of {
                  Just name -> (name_cache, name);
                  Nothing   ->
                  case takeUniqFromSupply (nsUniqs name_cache) of {
                  (uniq, us) ->
                      let
                        name      = mkExternalName uniq mod occ noSrcSpan
                        new_cache = extendNameCache (nsNames name_cache) mod occ name
                      in (name_cache{ nsUniqs = us, nsNames = new_cache }, name)
        }}}

    externaliseName :: Module -> Name -> TcRnIf m n Name
    -- Take an Internal Name and make it an External one,
    -- with the same unique
    externaliseName mod name
      = do { let occ = nameOccName name
                 loc = nameSrcSpan name
                 uniq = nameUnique name
           ; occ `seq` return ()  -- c.f. seq in newGlobalBinder
           ; updNameCache $ \ ns ->
             let name' = mkExternalName uniq mod occ loc
                 ns'   = ns { nsNames = extendNameCache (nsNames ns) mod occ name' }
             in (ns', name') }

    {-
    ************************************************************************
    *                                                                      *
                    Name cache access
    *                                                                      *
    ************************************************************************

    See Note [The Name Cache] above.

    Note [Built-in syntax and the OrigNameCache]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    You might think that usin isBuiltInOcc_maybe in lookupOrigNameCache is
    unnecessary because tuple TyCon/DataCons are parsed as Exact RdrNames
    and *don't* appear as original names in interface files (because
    serialization gives them special treatment), so we will never look
    them up in the original name cache.

    However, there are two reasons why we might look up an Orig RdrName:

      * If you use setRdrNameSpace on an Exact RdrName it may be
        turned into an Orig RdrName.

      * Template Haskell turns a BuiltInSyntax Name into a TH.NameG
        (DsMeta.globalVar), and parses a NameG into an Orig RdrName
        (Convert.thRdrName).  So, eg $(do { reify '(,); ... }) will
        go this route (Trac #8954).
    -}

    lookupOrigNameCache :: OrigNameCache -> Module -> OccName -> Maybe Name
    lookupOrigNameCache nc mod occ
      | Just name <- isBuiltInOcc_maybe occ
      =     -- See Note [Known-key names], 3(c) in PrelNames
            -- Special case for tuples; there are too many
            -- of them to pre-populate the original-name cache
        Just name

      | otherwise
      = case lookupModuleEnv nc mod of
            Nothing      -> Nothing
            Just occ_env -> lookupOccEnv occ_env occ

    extendOrigNameCache :: OrigNameCache -> Name -> OrigNameCache
    extendOrigNameCache nc name
      = ASSERT2( isExternalName name, ppr name )
        extendNameCache nc (nameModule name) (nameOccName name) name

    extendNameCache :: OrigNameCache -> Module -> OccName -> Name -> OrigNameCache
    extendNameCache nc mod occ name
      = extendModuleEnvWith combine nc mod (unitOccEnv occ name)
      where
        combine _ occ_env = extendOccEnv occ_env occ name

    updNameCache :: (NameCache -> (NameCache, c)) -> TcRnIf a b c
    updNameCache upd_fn = do { hsc_env <- getTopEnv
                             ; liftIO $ updNameCacheIO hsc_env upd_fn }

    -- | A function that atomically updates the name cache given a modifier
    -- function.  The second result of the modifier function will be the result
    -- of the IO action.
    newtype NameCacheUpdater
          = NCU { updateNameCache :: forall c. (NameCache -> (NameCache, c)) -> IO c }

    -- | Return a function to atomically update the name cache.
    mkNameCacheUpdater :: TcRnIf a b NameCacheUpdater
    mkNameCacheUpdater = do { hsc_env <- getTopEnv
                            ; return (NCU (updNameCacheIO hsc_env)) }

    initNameCache :: UniqSupply -> [Name] -> NameCache
    initNameCache us names
      = NameCache { nsUniqs = us,
                    nsNames = initOrigNames names }

    initOrigNames :: [Name] -> OrigNameCache
    initOrigNames names = foldl extendOrigNameCache emptyModuleEnv names

    {-
    ************************************************************************
    *                                                                      *
                    Type variables and local Ids
    *                                                                      *
    ************************************************************************
    -}

    tcIfaceLclId :: FastString -> IfL Id
    tcIfaceLclId occ
      = do  { lcl <- getLclEnv
            ; case (lookupFsEnv (if_id_env lcl) occ) of
                Just ty_var -> return ty_var
                Nothing     -> failIfM (text "Iface id out of scope: " <+> ppr occ)
            }

    extendIfaceIdEnv :: [Id] -> IfL a -> IfL a
    extendIfaceIdEnv ids thing_inside
      = do  { env <- getLclEnv
            ; let { id_env' = extendFsEnvList (if_id_env env) pairs
                  ; pairs   = [(occNameFS (getOccName id), id) | id <- ids] }
            ; setLclEnv (env { if_id_env = id_env' }) thing_inside }

    tcIfaceTyVar :: FastString -> IfL TyVar
    tcIfaceTyVar occ
      = do  { lcl <- getLclEnv
            ; case (lookupFsEnv (if_tv_env lcl) occ) of
                Just ty_var -> return ty_var
                Nothing     -> failIfM (text "Iface type variable out of scope: " <+> ppr occ)
            }

    lookupIfaceTyVar :: IfaceTvBndr -> IfL (Maybe TyVar)
    lookupIfaceTyVar (occ, _)
      = do  { lcl <- getLclEnv
            ; return (lookupFsEnv (if_tv_env lcl) occ) }

    lookupIfaceVar :: IfaceBndr -> IfL (Maybe TyCoVar)
    lookupIfaceVar (IfaceIdBndr (occ, _))
      = do  { lcl <- getLclEnv
            ; return (lookupFsEnv (if_id_env lcl) occ) }
    lookupIfaceVar (IfaceTvBndr (occ, _))
      = do  { lcl <- getLclEnv
            ; return (lookupFsEnv (if_tv_env lcl) occ) }

    extendIfaceTyVarEnv :: [TyVar] -> IfL a -> IfL a
    extendIfaceTyVarEnv tyvars thing_inside
      = do  { env <- getLclEnv
            ; let { tv_env' = extendFsEnvList (if_tv_env env) pairs
                  ; pairs   = [(occNameFS (getOccName tv), tv) | tv <- tyvars] }
            ; setLclEnv (env { if_tv_env = tv_env' }) thing_inside }

    extendIfaceEnvs :: [TyCoVar] -> IfL a -> IfL a
    extendIfaceEnvs tcvs thing_inside
      = extendIfaceTyVarEnv tvs $
        extendIfaceIdEnv    cvs $
        thing_inside
      where
        (tvs, cvs) = partition isTyVar tcvs

    {-
    ************************************************************************
    *                                                                      *
                    Getting from RdrNames to Names
    *                                                                      *
    ************************************************************************
    -}

    lookupIfaceTop :: OccName -> IfL Name
    -- Look up a top-level name from the current Iface module
    lookupIfaceTop occ
      = do  { env <- getLclEnv; lookupOrig (if_mod env) occ }

    newIfaceName :: OccName -> IfL Name
    newIfaceName occ
      = do  { uniq <- newUnique
            ; return $! mkInternalName uniq occ noSrcSpan }

    newIfaceNames :: [OccName] -> IfL [Name]
    newIfaceNames occs
      = do  { uniqs <- newUniqueSupply
            ; return [ mkInternalName uniq occ noSrcSpan
                     | (occ,uniq) <- occs `zip` uniqsFromSupply uniqs] }