{-# LANGUAGE ScopedTypeVariables #-}

module Language.Haskell.GhcMod.GHCApi (
    withGHC
  , withGHCDummyFile
  , initializeFlags
  , initializeFlagsWithCradle
  , setTargetFiles
  , getDynamicFlags
  ) where

import Control.Applicative
import Control.Exception
import Control.Monad
import CoreMonad
import Data.Maybe (isJust,fromJust)
import Distribution.PackageDescription (PackageDescription)
import DynFlags
import Exception
import GHC
import Language.Haskell.GhcMod.CabalApi
import Language.Haskell.GhcMod.ErrMsg
import Language.Haskell.GhcMod.GHCChoice
import qualified Language.Haskell.GhcMod.Gap as Gap
import Language.Haskell.GhcMod.Types
import System.Exit
import System.IO
import System.Process

----------------------------------------------------------------

getSystemLibDir :: IO (Maybe FilePath)
getSystemLibDir = do
    res <- readProcess "ghc" ["--print-libdir"] []
    return $ case res of
        ""   -> Nothing
        dirn -> Just (init dirn)

----------------------------------------------------------------

-- | Converting the 'Ghc' monad to the 'IO' monad.
withGHCDummyFile :: Alternative m => Ghc (m a) -- ^ 'Ghc' actions created by the Ghc utilities.
                                  -> IO (m a)
withGHCDummyFile = withGHC "Dummy"

-- | Converting the 'Ghc' monad to the 'IO' monad.
withGHC :: Alternative m => FilePath  -- ^ A target file displayed in an error message.
                         -> Ghc (m a) -- ^ 'Ghc' actions created by the Ghc utilities.
                         -> IO (m a)
withGHC file body = do
    mlibdir <- getSystemLibDir
    ghandle ignore $ runGhc mlibdir $ do
        dflags <- getSessionDynFlags
        defaultCleanupHandler dflags body
  where
    ignore :: Alternative m => SomeException -> IO (m a)
    ignore e = do
        hPutStr stderr $ file ++ ":0:0:Error:"
        hPrint stderr e
        exitSuccess

----------------------------------------------------------------

importDirs :: [IncludeDir]
importDirs = [".","..","../..","../../..","../../../..","../../../../.."]

data Build = CabalPkg | SingleFile deriving Eq

-- | Initialize the 'DynFlags' relating to the compilation of a single
-- file or GHC session according to the 'Cradle' and 'Options'
-- provided.
initializeFlagsWithCradle :: GhcMonad m =>  Options -> Cradle -> [GHCOption] -> Bool -> m (LogReader, Maybe PackageDescription)
initializeFlagsWithCradle opt cradle ghcopts logging
  | cabal     = withCabal |||> withoutCabal
  | otherwise = withoutCabal
  where
    mCradleFile = cradleCabalFile cradle
    cabal = isJust mCradleFile
    withCabal = do
        pkgDesc <- liftIO $ parseCabalFile $ fromJust mCradleFile
        compOpts <- liftIO $ getCompilerOptions ghcopts cradle pkgDesc
        logger <- initSession CabalPkg opt compOpts logging
        return (logger, Just pkgDesc)
    withoutCabal = do
        logger <- initSession SingleFile opt compOpts logging
        return (logger, Nothing)
      where
        compOpts = CompilerOptions ghcopts importDirs []

----------------------------------------------------------------

initSession :: GhcMonad m => Build
            -> Options
            -> CompilerOptions
            -> Bool
            -> m LogReader
initSession build opt compOpts logging = do
    dflags0 <- getSessionDynFlags
    (dflags1,readLog) <- setupDynamicFlags dflags0
    _ <- setSessionDynFlags dflags1
    return readLog
  where
    cmdOpts = ghcOptions compOpts
    idirs   = includeDirs compOpts
    depPkgs = depPackages compOpts
    ls = lineSeparator opt
    setupDynamicFlags df0 = do
        df1 <- modifyFlagsWithOpts df0 cmdOpts
        let df2 = modifyFlags df1 idirs depPkgs (expandSplice opt) build
        df3 <- modifyFlagsWithOpts df2 $ ghcOpts opt
        liftIO $ setLogger logging df3 ls

----------------------------------------------------------------

-- | Initialize the 'DynFlags' relating to the compilation of a single
-- file or GHC session.
initializeFlags :: GhcMonad m => Options -> m ()
initializeFlags opt = do
    dflags0 <- getSessionDynFlags
    dflags1 <- modifyFlagsWithOpts dflags0 $ ghcOpts opt
    void $ setSessionDynFlags dflags1

----------------------------------------------------------------

-- FIXME removing Options
modifyFlags :: DynFlags -> [IncludeDir] -> [Package] -> Bool -> Build -> DynFlags
modifyFlags d0 idirs depPkgs splice build
  | splice    = setSplice d4
  | otherwise = d4
  where
    d1 = d0 { importPaths = idirs }
    d2 = d1 {
        ghcLink   = LinkInMemory
      , hscTarget = HscInterpreted
      }
    d3 = Gap.addDevPkgs d2 depPkgs
    d4 | build == CabalPkg = Gap.setCabalPkg d3
       | otherwise         = d3

setSplice :: DynFlags -> DynFlags
setSplice dflag = dopt_set dflag Opt_D_dump_splices

----------------------------------------------------------------

modifyFlagsWithOpts :: GhcMonad m => DynFlags -> [GHCOption] -> m DynFlags
modifyFlagsWithOpts dflags cmdOpts =
    tfst <$> parseDynamicFlags dflags (map noLoc cmdOpts)
  where
    tfst (a,_,_) = a

----------------------------------------------------------------

-- | Set the files that GHC will load / compile.
setTargetFiles :: (GhcMonad m) => [FilePath] -> m ()
setTargetFiles [] = error "ghc-mod: setTargetFiles: No target files given"
setTargetFiles files = do
    targets <- forM files $ \file -> guessTarget file Nothing
    setTargets targets

----------------------------------------------------------------

-- | Return the 'DynFlags' currently in use in the GHC session.
getDynamicFlags :: IO DynFlags
getDynamicFlags = do
    mlibdir <- getSystemLibDir
    runGhc mlibdir getSessionDynFlags