    module Vectorise.Env (
      Scope(..),

      -- * Local Environments
      LocalEnv(..),
      emptyLocalEnv,

      -- * Global Environments
      GlobalEnv(..),
      initGlobalEnv,
      extendImportedVarsEnv,
      extendFamEnv,
      setPAFunsEnv,
      setPRFunsEnv,
      modVectInfo
    ) where

    import HscTypes
    import InstEnv
    import FamInstEnv
    import CoreSyn
    import Type
    import Class
    import TyCon
    import DataCon
    import VarEnv
    import VarSet
    import Var
    import NameSet
    import Name
    import NameEnv
    import FastString

    import Data.Maybe

    -- |Indicates what scope something (a variable) is in.
    --
    data Scope a b
            = Global a
            | Local  b

    -- LocalEnv -------------------------------------------------------------------

    -- |The local environment.
    --
    data LocalEnv
            = LocalEnv
            { local_vars      :: VarEnv (Var, Var)
              -- ^Mapping from local variables to their vectorised and lifted versions.

            , local_tyvars    :: [TyVar]
              -- ^In-scope type variables.

            , local_tyvar_pa  :: VarEnv CoreExpr
              -- ^Mapping from tyvars to their PA dictionaries.

            , local_bind_name :: FastString
              -- ^Local binding name. This is only used to generate better names for hoisted
              -- expressions.
            }

    -- |Create an empty local environment.
    --
    emptyLocalEnv :: LocalEnv
    emptyLocalEnv = LocalEnv
                    { local_vars      = emptyVarEnv
                    , local_tyvars    = []
                    , local_tyvar_pa  = emptyVarEnv
                    , local_bind_name = fsLit "fn"
                    }

    -- GlobalEnv ------------------------------------------------------------------

    -- |The global environment: entities that exist at top-level.
    --
    data GlobalEnv
            = GlobalEnv
            { global_vect_avoid           :: Bool
              -- ^'True' implies to avoid vectorisation as far as possible.

            , global_vars                 :: VarEnv Var
              -- ^Mapping from global variables to their vectorised versions — aka the /vectorisation
              -- map/.

            , global_parallel_vars        :: VarSet
              -- ^The domain of 'global_vars'.
              --
              -- This information is not redundant as it is impossible to extract the domain from a
              -- 'VarEnv' (which is keyed on uniques alone). Moreover, we have mapped variables that
              -- do not involve parallelism — e.g., the workers of vectorised, but scalar data types.
              -- In addition, workers of parallel data types that we could not vectorise also need to
              -- be tracked.

            , global_vect_decls           :: VarEnv (Maybe (Type, CoreExpr))
              -- ^Mapping from global variables that have a vectorisation declaration to the right-hand
              -- side of that declaration and its type and mapping variables that have NOVECTORISE
              -- declarations to 'Nothing'.

            , global_tycons               :: NameEnv TyCon
              -- ^Mapping from TyCons to their vectorised versions. The vectorised version will be
              -- identical to the original version if it is not changed by vectorisation. In any case,
              -- if a tycon appears in the domain of this mapping, it was successfully vectorised.

            , global_parallel_tycons      :: NameSet
              -- ^Type constructors whose definition directly or indirectly includes a parallel type,
              -- such as '[::]'.
              --
              -- NB: This information is not redundant as some types have got a mapping in
              --     'global_tycons' (to a type other than themselves) and are still not parallel. An
              --     example is '(->)'. Moreover, some types have *not* got a mapping in 'global_tycons'
              --     (because they couldn't be vectorised), but still contain parallel types.

            , global_datacons             :: NameEnv DataCon
              -- ^Mapping from DataCons to their vectorised versions.

            , global_pa_funs              :: NameEnv Var
              -- ^Mapping from TyCons to their PA dfuns.

            , global_pr_funs              :: NameEnv Var
              -- ^Mapping from TyCons to their PR dfuns.

            , global_inst_env             :: InstEnvs
              -- ^External package inst-env & home-package inst-env for class instances.

            , global_fam_inst_env         :: FamInstEnvs
              -- ^External package inst-env & home-package inst-env for family instances.

            , global_bindings             :: [(Var, CoreExpr)]
              -- ^Hoisted bindings — temporary storage for toplevel bindings during code gen.
            }

    -- |Create an initial global environment.
    --
    -- We add scalar variables and type constructors identified by vectorisation pragmas already here
    -- to the global table, so that we can query scalarness during vectorisation, and especially, when
    -- vectorising the scalar entities' definitions themselves.
    --
    initGlobalEnv :: Bool
                  -> VectInfo
                  -> [CoreVect]
                  -> InstEnvs
                  -> FamInstEnvs
                  -> GlobalEnv
    initGlobalEnv vectAvoid info vectDecls instEnvs famInstEnvs
      = GlobalEnv
      { global_vect_avoid           = vectAvoid
      , global_vars                 = mapVarEnv snd $ vectInfoVar info
      , global_vect_decls           = mkVarEnv vects
      , global_parallel_vars        = vectInfoParallelVars info
      , global_parallel_tycons      = vectInfoParallelTyCons info
      , global_tycons               = mapNameEnv snd $ vectInfoTyCon info
      , global_datacons             = mapNameEnv snd $ vectInfoDataCon info
      , global_pa_funs              = emptyNameEnv
      , global_pr_funs              = emptyNameEnv
      , global_inst_env             = instEnvs
      , global_fam_inst_env         = famInstEnvs
      , global_bindings             = []
      }
      where
        vects         = [(var, Just (ty, exp)) | Vect   var   exp@(Var rhs_var) <- vectDecls
                                               , let ty = varType rhs_var] ++
                                            -- FIXME: we currently only allow RHSes consisting of a
                                            --   single variable to be able to obtain the type without
                                            --   inference — see also 'TcBinds.tcVect'
                        [(var, Nothing)        | NoVect var                     <- vectDecls]

    -- Operators on Global Environments -------------------------------------------

    -- |Extend the list of global variables in an environment.
    --
    extendImportedVarsEnv :: [(Var, Var)] -> GlobalEnv -> GlobalEnv
    extendImportedVarsEnv ps genv
      = genv { global_vars = extendVarEnvList (global_vars genv) ps }

    -- |Extend the list of type family instances.
    --
    extendFamEnv :: [FamInst] -> GlobalEnv -> GlobalEnv
    extendFamEnv new genv
      = genv { global_fam_inst_env = (g_fam_inst, extendFamInstEnvList l_fam_inst new) }
      where (g_fam_inst, l_fam_inst) = global_fam_inst_env genv

    -- |Set the list of PA functions in an environment.
    --
    setPAFunsEnv :: [(Name, Var)] -> GlobalEnv -> GlobalEnv
    setPAFunsEnv ps genv = genv { global_pa_funs = mkNameEnv ps }

    -- |Set the list of PR functions in an environment.
    --
    setPRFunsEnv :: [(Name, Var)] -> GlobalEnv -> GlobalEnv
    setPRFunsEnv ps genv = genv { global_pr_funs = mkNameEnv ps }

    -- |Compute vectorisation information that goes into 'ModGuts' (and is stored in interface files).
    -- The incoming 'vectInfo' is that from the 'HscEnv' and 'EPS'.  The outgoing one contains only the
    -- declarations for the currently compiled module; this includes variables, type constructors, and
    -- data constructors referenced in VECTORISE pragmas, even if they are defined in an imported
    -- module.
    --
    -- The variables explicitly include class selectors and dfuns.
    --
    modVectInfo :: GlobalEnv -> [Id] -> [TyCon] -> [CoreVect]-> VectInfo -> VectInfo
    modVectInfo env mg_ids mg_tyCons vectDecls info
      = info
        { vectInfoVar            = mk_env ids      (global_vars     env)
        , vectInfoTyCon          = mk_env tyCons   (global_tycons   env)
        , vectInfoDataCon        = mk_env dataCons (global_datacons env)
        , vectInfoParallelVars   = (global_parallel_vars   env `minusVarSet`  vectInfoParallelVars   info)
                                   `intersectVarSet` (mkVarSet ids)
        , vectInfoParallelTyCons =  global_parallel_tycons env `minusNameSet` vectInfoParallelTyCons info
        }
      where
        vectIds         = [id    | Vect     id    _   <- vectDecls] ++
                          [id    | VectInst id        <- vectDecls]
        vectTypeTyCons  = [tycon | VectType _ tycon _ <- vectDecls] ++
                          [tycon | VectClass tycon    <- vectDecls]
        vectDataCons    = concatMap tyConDataCons vectTypeTyCons
        ids             = mg_ids ++ vectIds ++ dataConIds ++ selIds
        tyCons          = mg_tyCons ++ vectTypeTyCons
        dataCons        = concatMap tyConDataCons mg_tyCons ++ vectDataCons
        dataConIds      = map dataConWorkId dataCons
        selIds          = concat [ classAllSelIds cls
                                 | tycon <- tyCons
                                 , cls <- maybeToList . tyConClass_maybe $ tycon]

        -- Produce an entry for every declaration that is mentioned in the domain of the 'inspectedEnv'
        mk_env decls inspectedEnv
          = mkNameEnv [(name, (decl, to))
                      | decl     <- decls
                      , let name = getName decl
                      , Just to  <- [lookupNameEnv inspectedEnv name]]