{-# LANGUAGE ScopedTypeVariables #-}
module DynLoad (
    loadSourceGhc,
    execFnGhc
    ) where

import Control.Exception (throw)
import GHC hiding (loadModule)
import GHC.Paths (libdir)
import HscTypes (SourceError, srcErrorMessages)
import DynFlags
import Unsafe.Coerce
import Bag (bagToList)

execFnGhc :: String -> String -> Ghc a
execFnGhc modname fn = do
        mod <- findModule (mkModuleName modname) Nothing
        setContext [] [mod]
        value <- compileExpr (modname ++ "." ++ fn)

        let value' = (unsafeCoerce value) :: a
        return value'

loadSourceGhc :: String -> Ghc (Maybe String)
loadSourceGhc path = let
        throwingLogger (Just e) = throw e
        throwingLogger _ = return ()
    in do
        dflags <- getSessionDynFlags
        setSessionDynFlags (dflags{
            ghcLink = LinkInMemory,
            hscTarget = HscInterpreted,
            packageFlags = [ExposePackage "ghc"]
            })
        target <- guessTarget path Nothing
        addTarget target
        r <- loadWithLogger throwingLogger LoadAllTargets
        case r of
            Failed    -> return $ Just "Generic module load error"
            Succeeded -> return Nothing

        `gcatch` \(e :: SourceError) -> let
                errors e = concat $ map show (bagToList $ srcErrorMessages e)
            in
                return $ Just (errors e)