\section[Hooks]{Low level API hooks}

\begin{code}
module Hooks ( Hooks
             , emptyHooks
             , lookupHook
             , getHooked
               -- the hooks:
             , dsForeignsHook
             , tcForeignImportsHook
             , tcForeignExportsHook
             , hscFrontendHook
             , hscCompileOneShotHook
             , hscCompileCoreExprHook
             , ghcPrimIfaceHook
             , runPhaseHook
             , linkHook
             , runQuasiQuoteHook
             , getValueSafelyHook
             ) where

import DynFlags
import HsTypes
import Name
import PipelineMonad
import HscTypes
import HsDecls
import HsBinds
import {-# SOURCE #-} DsMonad
import OrdList
import Id
import TcRnTypes
import Bag
import RdrName
import CoreSyn
import BasicTypes
import Type
import SrcLoc

import Data.Maybe
\end{code}

%************************************************************************
%*                                                                      *
\subsection{Hooks}
%*                                                                      *
%************************************************************************

\begin{code}

-- | Hooks can be used by GHC API clients to replace parts of
--   the compiler pipeline. If a hook is not installed, GHC
--   uses the default built-in behaviour

emptyHooks :: Hooks
emptyHooks = Hooks Nothing Nothing Nothing Nothing Nothing Nothing
                   Nothing Nothing Nothing Nothing Nothing

data Hooks = Hooks
  { dsForeignsHook         :: Maybe ([LForeignDecl Id] -> DsM (ForeignStubs, OrdList (Id, CoreExpr)))
  , tcForeignImportsHook   :: Maybe ([LForeignDecl Name] -> TcM ([Id], [LForeignDecl Id], Bag GlobalRdrElt))
  , tcForeignExportsHook   :: Maybe ([LForeignDecl Name] -> TcM (LHsBinds TcId, [LForeignDecl TcId], Bag GlobalRdrElt))
  , hscFrontendHook        :: Maybe (ModSummary -> Hsc TcGblEnv)
  , hscCompileOneShotHook  :: Maybe (HscEnv -> FilePath -> ModSummary -> SourceModified -> IO HscStatus)
  , hscCompileCoreExprHook :: Maybe (HscEnv -> SrcSpan -> CoreExpr -> IO HValue)
  , ghcPrimIfaceHook       :: Maybe ModIface
  , runPhaseHook           :: Maybe (PhasePlus -> FilePath -> DynFlags -> CompPipeline (PhasePlus, FilePath))
  , linkHook               :: Maybe (GhcLink -> DynFlags -> Bool -> HomePackageTable -> IO SuccessFlag)
  , runQuasiQuoteHook      :: Maybe (HsQuasiQuote Name -> RnM (HsQuasiQuote Name))
  , getValueSafelyHook     :: Maybe (HscEnv -> Name -> Type -> IO (Maybe HValue))
  }

getHooked :: (Functor f, HasDynFlags f) => (Hooks -> Maybe a) -> a -> f a
getHooked hook def = fmap (lookupHook hook def) getDynFlags

lookupHook :: (Hooks -> Maybe a) -> a -> DynFlags -> a
lookupHook hook def = fromMaybe def . hook . hooks

\end{code}