{-# LANGUAGE ScopedTypeVariables #-}

module Language.Haskell.GhcMod.GHCApi (
    withGHC
  , withGHCDummyFile
  , initializeFlags
  , initializeFlagsWithCradle
  , setTargetFile
  , getDynamicFlags
  , setSlowDynFlags
  , checkSlowAndSet
  , canCheckFast
  ) where

import Control.Applicative
import Control.Exception
import Control.Monad
import CoreMonad
import Data.Maybe (isJust)
import DynFlags
import Exception
import GHC
import GHC.Paths (libdir)
import Language.Haskell.GhcMod.CabalApi
import Language.Haskell.GhcMod.ErrMsg
import Language.Haskell.GhcMod.GHCChoice
import Language.Haskell.GhcMod.Types
import qualified Language.Haskell.GhcMod.Gap as Gap
import System.Exit
import System.IO

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

-- | 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 = ghandle ignore $ runGhc (Just libdir) $ 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
initializeFlagsWithCradle opt cradle ghcOptions logging
  | cabal     = withCabal |||> withoutCabal
  | otherwise = withoutCabal
  where
    cabal = isJust $ cradleCabalFile cradle
    withCabal = do
        (gopts,idirs,depPkgs) <- liftIO $ fromCabalFile ghcOptions cradle
        initSession CabalPkg opt gopts idirs (Just depPkgs) logging
    withoutCabal =
        initSession SingleFile opt ghcOptions importDirs Nothing logging

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

initSession :: GhcMonad m => Build
            -> Options
            -> [GHCOption]
            -> [IncludeDir]
            -> Maybe [Package]
            -> Bool
            -> m LogReader
initSession build opt cmdOpts idirs mDepPkgs logging = do
    dflags0 <- getSessionDynFlags
    (dflags1,readLog) <- setupDynamicFlags dflags0
    _ <- setSessionDynFlags dflags1
    return readLog
  where
    setupDynamicFlags df0 = do
        df1 <- modifyFlagsWithOpts df0 cmdOpts
        let df2 = modifyFlags df1 idirs mDepPkgs (expandSplice opt) build
        df3 <- modifyFlagsWithOpts df2 $ ghcOpts opt
        liftIO $ setLogger logging df3

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

initializeFlags :: GhcMonad m => Options -> m ()
initializeFlags opt = do
    dflags0 <- getSessionDynFlags
    dflags1 <- modifyFlagsWithOpts dflags0 $ ghcOpts opt
    void $ setSessionDynFlags dflags1

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

-- FIXME removing Options
modifyFlags :: DynFlags -> [IncludeDir] -> Maybe [Package] -> Bool -> Build -> DynFlags
modifyFlags d0 idirs mDepPkgs splice build
  | splice    = setSplice d4
  | otherwise = d4
  where
    d1 = d0 { importPaths = idirs }
    d2 = setFastOrNot d1 Fast
    d3 = maybe d2 (Gap.addDevPkgs d2) mDepPkgs
    d4 | build == CabalPkg = Gap.setCabalPkg d3
       | otherwise         = d3

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

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

setFastOrNot :: DynFlags -> CheckSpeed -> DynFlags
setFastOrNot dflags Slow = dflags {
    ghcLink   = LinkInMemory
  , hscTarget = HscInterpreted
  }
setFastOrNot dflags Fast = dflags {
    ghcLink   = NoLink
  , hscTarget = HscNothing
  }

setSlowDynFlags :: GhcMonad m => m ()
setSlowDynFlags = (flip setFastOrNot Slow <$> getSessionDynFlags)
                  >>= void . setSessionDynFlags

-- | To check TH, a session module graph is necessary.
-- "load" sets a session module graph using "depanal".
-- But we have to set "-fno-code" to DynFlags before "load".
-- So, this is necessary redundancy.
checkSlowAndSet :: GhcMonad m => m ()
checkSlowAndSet = do
    fast <- canCheckFast <$> depanal [] False
    unless fast setSlowDynFlags

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

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

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

-- | Set the file that GHC will load / compile
setTargetFile :: (GhcMonad m) => String -> m ()
setTargetFile file = do
    target <- guessTarget file Nothing
    setTargets [target]

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

-- | Return the 'DynFlags' currently in use in the GHC session
getDynamicFlags :: IO DynFlags
getDynamicFlags = runGhc (Just libdir) getSessionDynFlags

canCheckFast :: ModuleGraph -> Bool
canCheckFast = not . any (hasTHorQQ . ms_hspp_opts)
  where
    hasTHorQQ :: DynFlags -> Bool
    hasTHorQQ dflags = any (`xopt` dflags) [Opt_TemplateHaskell, Opt_QuasiQuotes]