{-# LANGUAGE BangPatterns, CPP #-}

module HIE.Bios.Ghc.Logger (
    withLogger
  ) where

import GHC (DynFlags(..), SrcSpan(..), GhcMonad, getSessionDynFlags)
import qualified GHC as G
import Control.Monad.IO.Class

#if __GLASGOW_HASKELL__ >= 902
import GHC.Data.Bag
import GHC.Data.FastString (unpackFS)
import GHC.Driver.Session (dopt, DumpFlag(Opt_D_dump_splices))
import GHC.Types.SourceError
import GHC.Utils.Error
import GHC.Utils.Logger
#elif __GLASGOW_HASKELL__ >= 900
import GHC.Data.Bag
import GHC.Data.FastString (unpackFS)
import GHC.Driver.Session (dopt, DumpFlag(Opt_D_dump_splices), LogAction)
import GHC.Driver.Types (SourceError, srcErrorMessages)
import GHC.Utils.Error
import GHC.Utils.Outputable (SDoc)
#else
import Bag (Bag, bagToList)
import DynFlags (LogAction, dopt, DumpFlag(Opt_D_dump_splices))
import ErrUtils
import FastString (unpackFS)
import HscTypes (SourceError, srcErrorMessages)
import Outputable (SDoc)
#endif

import Data.IORef (IORef, newIORef, readIORef, writeIORef, modifyIORef)
import Data.Maybe (fromMaybe)

import System.FilePath (normalise)

import HIE.Bios.Ghc.Doc (showPage, getStyle)
import HIE.Bios.Ghc.Api (withDynFlags)
import qualified HIE.Bios.Ghc.Gap as Gap

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

type Builder = [String] -> [String]

newtype LogRef = LogRef (IORef Builder)

newLogRef :: IO LogRef
newLogRef = LogRef <$> newIORef id

readAndClearLogRef :: LogRef -> IO String
readAndClearLogRef (LogRef ref) = do
    b <- readIORef ref
    writeIORef ref id
    return $! unlines (b [])

appendLogRef :: DynFlags -> Gap.PprStyle -> LogRef -> LogAction
appendLogRef df style (LogRef ref) _ _ sev src
#if __GLASGOW_HASKELL__ < 900
  _style
#endif
  msg = do
        let !l = ppMsg src sev df style msg
        modifyIORef ref (\b -> b . (l:))

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

-- | Set the session flag (e.g. "-Wall" or "-w:") then
--   executes a body. Log messages are returned as 'String'.
--   Right is success and Left is failure.
withLogger ::
  (GhcMonad m)
  => (DynFlags -> DynFlags) -> m () -> m (Either String String)
withLogger setDF body = Gap.handle sourceError $ do
    logref <- liftIO newLogRef
    dflags <- getSessionDynFlags
    style <- getStyle dflags
#if __GLASGOW_HASKELL__ >= 902
    G.pushLogHookM (const $ appendLogRef dflags style logref)
    let setLogger _ df = df
#else
    let setLogger logref_ df = df { log_action =  appendLogRef df style logref_ }
#endif
    r <- withDynFlags (setLogger logref . setDF) $ do
      body
      liftIO $ Right <$> readAndClearLogRef logref
#if __GLASGOW_HASKELL__ >= 902
    G.popLogHookM
#endif
    pure r



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

-- | Converting 'SourceError' to 'String'.
sourceError ::
  (GhcMonad m)
  => SourceError -> m (Either String String)
sourceError err = do
    dflag <- getSessionDynFlags
    style <- getStyle dflag
    let ret = unlines . errBagToStrList dflag style . srcErrorMessages $ err
    return (Left ret)

#if __GLASGOW_HASKELL__ >= 902
errBagToStrList :: DynFlags -> Gap.PprStyle -> Bag (MsgEnvelope DecoratedSDoc) -> [String]
errBagToStrList dflag style = map (ppErrMsg dflag style) . reverse . bagToList


ppErrMsg :: DynFlags -> Gap.PprStyle -> MsgEnvelope DecoratedSDoc -> String
ppErrMsg dflag style err = ppMsg spn SevError dflag style msg -- ++ ext
   where
     spn = errMsgSpan err
     msg = pprLocMsgEnvelope err
     -- fixme
#else
errBagToStrList :: DynFlags -> Gap.PprStyle -> Bag ErrMsg -> [String]
errBagToStrList dflag style = map (ppErrMsg dflag style) . reverse . bagToList

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

ppErrMsg :: DynFlags -> Gap.PprStyle -> ErrMsg -> String
ppErrMsg dflag style err = ppMsg spn SevError dflag style msg -- ++ ext
   where
     spn = errMsgSpan err
     msg = pprLocErrMsg err
     -- fixme
--     ext = showPage dflag style (pprLocErrMsg $ errMsgReason err)
#endif

ppMsg :: SrcSpan -> G.Severity-> DynFlags -> Gap.PprStyle -> SDoc -> String
ppMsg spn sev dflag style msg = prefix ++ cts
  where
    cts  = showPage dflag style msg
    defaultPrefix
      | isDumpSplices dflag = ""
      | otherwise           = checkErrorPrefix
    prefix = fromMaybe defaultPrefix $ do
        (line,col,_,_) <- getSrcSpan spn
        file <- normalise <$> getSrcFile spn
        let severityCaption = showSeverityCaption sev
        return $ file ++ ":" ++ show line ++ ":" ++ show col ++ ":" ++ severityCaption

checkErrorPrefix :: String
checkErrorPrefix = "Dummy:0:0:Error:"

showSeverityCaption :: G.Severity -> String
showSeverityCaption G.SevWarning = "Warning: "
showSeverityCaption _          = ""

getSrcFile :: SrcSpan -> Maybe String
getSrcFile (Gap.RealSrcSpan spn) = Just . unpackFS . G.srcSpanFile $ spn
getSrcFile _                   = Nothing

isDumpSplices :: DynFlags -> Bool
isDumpSplices dflag = dopt Opt_D_dump_splices dflag

getSrcSpan :: SrcSpan -> Maybe (Int,Int,Int,Int)
getSrcSpan (Gap.RealSrcSpan spn) =
    Just ( G.srcSpanStartLine spn
         , G.srcSpanStartCol spn
         , G.srcSpanEndLine spn
         , G.srcSpanEndCol spn)
getSrcSpan _ = Nothing