{-# LANGUAGE ScopedTypeVariables, RecordWildCards #-}

module Language.Haskell.GhcMod.GHCApi (
    withGHC
  , withGHC'
  , initializeFlagsWithCradle
  , setTargetFiles
  , addTargetFiles
  , getDynamicFlags
  , getSystemLibDir
  , withDynFlags
  , setNoWaringFlags
  , setAllWaringFlags
  ) where

import Language.Haskell.GhcMod.CabalApi
import Language.Haskell.GhcMod.GHCChoice
import Language.Haskell.GhcMod.GhcPkg

import Control.Applicative ((<$>))
import Control.Monad (forM, void)
import CoreMonad (liftIO)
import Data.IntSet (IntSet, empty)
import Data.Maybe (isJust, fromJust)
import Exception (ghandle, SomeException(..))
import GHC (Ghc, GhcMonad, DynFlags(..), GhcLink(..), HscTarget(..), LoadHowMuch(..))
import qualified GHC as G
import qualified Language.Haskell.GhcMod.Gap as Gap
import Language.Haskell.GhcMod.Types
import System.Exit (exitSuccess)
import System.IO (hPutStr, hPrint, stderr)
import System.IO.Unsafe (unsafePerformIO)
import System.Process (readProcess)

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

-- | Obtaining the directory for system libraries.
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.
withGHC :: FilePath  -- ^ A target file displayed in an error message.
        -> Ghc a -- ^ 'Ghc' actions created by the Ghc utilities.
        -> IO a
withGHC file body = ghandle ignore $ withGHC' body
  where
    ignore :: SomeException -> IO a
    ignore e = do
        hPutStr stderr $ file ++ ":0:0:Error:"
        hPrint stderr e
        exitSuccess

withGHC' :: Ghc a -> IO a
withGHC' body = do
    mlibdir <- getSystemLibDir
    G.runGhc mlibdir $ do
        dflags <- G.getSessionDynFlags
        G.defaultCleanupHandler dflags body

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

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
        -> m ()
initializeFlagsWithCradle opt cradle
  | cabal     = withCabal |||> withSandbox
  | otherwise = withSandbox
  where
    mCradleFile = cradleCabalFile cradle
    cabal = isJust mCradleFile
    ghcopts = ghcOpts opt
    withCabal = do
        pkgDesc <- liftIO $ parseCabalFile $ fromJust mCradleFile
        compOpts <- liftIO $ getCompilerOptions ghcopts cradle pkgDesc
        initSession CabalPkg opt compOpts
    withSandbox = initSession SingleFile opt compOpts
      where
        pkgOpts = ghcDbStackOpts $ cradlePkgDbStack cradle
        compOpts
          | null pkgOpts = CompilerOptions ghcopts importDirs []
          | otherwise    = CompilerOptions (ghcopts ++ pkgOpts) [wdir,rdir] []
        wdir = cradleCurrentDir cradle
        rdir = cradleRootDir    cradle

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

initSession :: GhcMonad m
            => Build
            -> Options
            -> CompilerOptions
            -> m ()
initSession build Options {..} CompilerOptions {..} = do
    df <- G.getSessionDynFlags
    void $ G.setSessionDynFlags =<< (addCmdOpts ghcOptions
      $ setLinkerOptions
      $ setIncludeDirs includeDirs
      $ setBuildEnv build
      $ setEmptyLogger
      $ Gap.addPackageFlags depPackages df)

setEmptyLogger :: DynFlags -> DynFlags
setEmptyLogger df = Gap.setLogAction df $ \_ _ _ _ _ -> return ()

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

-- we don't want to generate object code so we compile to bytecode
-- (HscInterpreted) which implies LinkInMemory
-- HscInterpreted
setLinkerOptions :: DynFlags -> DynFlags
setLinkerOptions df = df {
    ghcLink   = LinkInMemory
  , hscTarget = HscInterpreted
  }

setIncludeDirs :: [IncludeDir] -> DynFlags -> DynFlags
setIncludeDirs idirs df = df { importPaths = idirs }

setBuildEnv :: Build -> DynFlags -> DynFlags
setBuildEnv build = setHideAllPackages build . setCabalPackage build

-- At the moment with this option set ghc only prints different error messages,
-- suggesting the user to add a hidden package to the build-depends in his cabal
-- file for example
setCabalPackage :: Build -> DynFlags -> DynFlags
setCabalPackage CabalPkg df = Gap.setCabalPkg df
setCabalPackage _ df = df

-- | Enable hiding of all package not explicitly exposed (like Cabal does)
setHideAllPackages :: Build -> DynFlags -> DynFlags
setHideAllPackages CabalPkg df = Gap.setHideAllPackages df
setHideAllPackages _ df = df

-- | Parse command line ghc options and add them to the 'DynFlags' passed
addCmdOpts :: GhcMonad m => [GHCOption] -> DynFlags -> m DynFlags
addCmdOpts cmdOpts df =
    tfst <$> G.parseDynamicFlags df (map G.noLoc cmdOpts)
  where
    tfst (a,_,_) = a

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

-- | Set the files and load
setTargetFiles :: (GhcMonad m) => [FilePath] -> m ()
setTargetFiles files = do
    targets <- forM files $ \file -> G.guessTarget file Nothing
    G.setTargets targets
    void $ G.load LoadAllTargets

-- | Adding the files to the targets.
addTargetFiles :: (GhcMonad m) => [FilePath] -> m ()
addTargetFiles files = do
    targets <- forM files $ \file -> G.guessTarget file Nothing
    mapM_ G.addTarget targets
    void $ G.load LoadAllTargets

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

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

withDynFlags :: (DynFlags -> DynFlags) -> Ghc a -> Ghc a
withDynFlags setFlag body = G.gbracket setup teardown (\_ -> body)
  where
    setup = do
        dflag <- G.getSessionDynFlags
        void $ G.setSessionDynFlags (setFlag dflag)
        return dflag
    teardown = void . G.setSessionDynFlags

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

setNoWaringFlags :: DynFlags -> DynFlags
setNoWaringFlags df = df { warningFlags = empty}

setAllWaringFlags :: DynFlags -> DynFlags
setAllWaringFlags df = df { warningFlags = allWarningFlags }

allWarningFlags :: IntSet
allWarningFlags = unsafePerformIO $ do
    mlibdir <- getSystemLibDir
    G.runGhc mlibdir $ do
        df <- G.getSessionDynFlags
        df' <- addCmdOpts ["-Wall"] df
        return $ G.warningFlags df'