module GhciMonad where

#include "HsVersions.h"

import qualified GHC
import {-#SOURCE#-} Debugger
import Breakpoints
import Outputable
import Panic hiding (showException)
import Util

import Numeric
import Control.Exception as Exception
import Data.Char
import Data.Dynamic
import Data.Int         ( Int64 )
import Data.IORef
import Data.Typeable
import System.CPUTime
import System.IO
import Control.Monad as Monad
import GHC.Exts

-----------------------------------------------------------------------------
-- GHCi monad

data GHCiState = GHCiState
     { 
	progname       :: String,
	args	       :: [String],
        prompt         :: String,
	editor         :: String,
	session        :: GHC.Session,
	options        :: [GHCiOption],
        prelude        :: GHC.Module,
        bkptTable      :: IORef (BkptTable GHC.Module),
	topLevel       :: Bool
     }

data GHCiOption 
	= ShowTiming		-- show time/allocs after evaluation
	| ShowType		-- show the type of expressions
	| RevertCAFs		-- revert CAFs after every evaluation
	deriving Eq

newtype GHCi a = GHCi { unGHCi :: IORef GHCiState -> IO a }

startGHCi :: GHCi a -> GHCiState -> IO a
startGHCi g state = do ref <- newIORef state; unGHCi g ref

instance Monad GHCi where
  (GHCi m) >>= k  =  GHCi $ \s -> m s >>= \a -> unGHCi (k a) s
  return a  = GHCi $ \s -> return a

ghciHandleDyn :: Typeable t => (t -> GHCi a) -> GHCi a -> GHCi a
ghciHandleDyn h (GHCi m) = GHCi $ \s -> 
   Exception.catchDyn (m s) (\e -> unGHCi (h e) s)

getGHCiState   = GHCi $ \r -> readIORef r
setGHCiState s = GHCi $ \r -> writeIORef r s

-- for convenience...
getSession = getGHCiState >>= return . session
getPrelude = getGHCiState >>= return . prelude

GLOBAL_VAR(saved_sess, no_saved_sess, GHC.Session)
no_saved_sess = error "no saved_ses"
saveSession = getSession >>= io . writeIORef saved_sess
splatSavedSession = io (writeIORef saved_sess no_saved_sess)
restoreSession = readIORef saved_sess

getDynFlags = do
  s <- getSession
  io (GHC.getSessionDynFlags s)
setDynFlags dflags = do 
  s <- getSession 
  io (GHC.setSessionDynFlags s dflags)

isOptionSet :: GHCiOption -> GHCi Bool
isOptionSet opt
 = do st <- getGHCiState
      return (opt `elem` options st)

setOption :: GHCiOption -> GHCi ()
setOption opt
 = do st <- getGHCiState
      setGHCiState (st{ options = opt : filter (/= opt) (options st) })

unsetOption :: GHCiOption -> GHCi ()
unsetOption opt
 = do st <- getGHCiState
      setGHCiState (st{ options = filter (/= opt) (options st) })

io :: IO a -> GHCi a
io m = GHCi { unGHCi = \s -> m >>= return }

isTopLevel :: GHCi Bool
isTopLevel = getGHCiState >>= return . topLevel

getBkptTable :: GHCi (BkptTable GHC.Module)
getBkptTable = do table_ref <- getGHCiState >>= return . bkptTable
                  io$ readIORef table_ref

setBkptTable :: BkptTable GHC.Module -> GHCi ()
setBkptTable new_table = do 
    table_ref <- getGHCiState >>= return . bkptTable
    io$ writeIORef table_ref new_table
                  
modifyBkptTable :: (BkptTable GHC.Module -> BkptTable GHC.Module) -> GHCi ()
modifyBkptTable f = do 
    bt <- getBkptTable
    new_bt <- io . evaluate$ f bt 
    setBkptTable new_bt

showForUser :: SDoc -> GHCi String
showForUser doc = do
  session <- getSession
  unqual <- io (GHC.getPrintUnqual session)
  return $! showSDocForUser unqual doc

-----------------------------------------------------------------------------
-- User code exception handling

-- This hierarchy of exceptions is used to signal interruption of a child session
data BkptException = StopChildSession -- A child debugging session requests to be stopped
                   | ChildSessionStopped String  
  deriving Typeable

-- This is the exception handler for exceptions generated by the
-- user's code and exceptions coming from children sessions; 
-- it normally just prints out the exception.  The
-- handler must be recursive, in case showing the exception causes
-- more exceptions to be raised.
--
-- Bugfix: if the user closed stdout or stderr, the flushing will fail,
-- raising another exception.  We therefore don't put the recursive
-- handler arond the flushing operation, so if stderr is closed
-- GHCi will just die gracefully rather than going into an infinite loop.
handler :: Exception -> GHCi Bool
handler (DynException dyn)        
  | Just StopChildSession <- fromDynamic dyn 
 -- propagate to the parent session
  = do ASSERTM (liftM not isTopLevel) 
       throwDyn StopChildSession

  | Just (ChildSessionStopped msg) <- fromDynamic dyn 
 -- Revert CAFs and display some message
  = do ASSERTM (isTopLevel) 
       io (revertCAFs >> putStrLn msg)
       return False

handler exception = do
  flushInterpBuffers
  io installSignalHandlers
  ghciHandle handler (showException exception >> return False)

showException (DynException dyn) =
  case fromDynamic dyn of
    Nothing               -> io (putStrLn ("*** Exception: (unknown)"))
    Just Interrupted      -> io (putStrLn "Interrupted.")
    Just (CmdLineError s) -> io (putStrLn s)	 -- omit the location for CmdLineError
    Just ph@PhaseFailed{} -> io (putStrLn (showGhcException ph "")) -- ditto
    Just other_ghc_ex     -> io (print other_ghc_ex)

showException other_exception
  = io (putStrLn ("*** Exception: " ++ show other_exception))

-----------------------------------------------------------------------------
-- recursive exception handlers

-- Don't forget to unblock async exceptions in the handler, or if we're
-- in an exception loop (eg. let a = error a in a) the ^C exception
-- may never be delivered.  Thanks to Marcin for pointing out the bug.

ghciHandle :: (Exception -> GHCi a) -> GHCi a -> GHCi a
ghciHandle h (GHCi m) = GHCi $ \s -> 
   Exception.catch (m s) 
	(\e -> unGHCi (ghciUnblock (h e)) s)

ghciUnblock :: GHCi a -> GHCi a
ghciUnblock (GHCi a) = GHCi $ \s -> Exception.unblock (a s)

-----------------------------------------------------------------------------
-- timing & statistics

timeIt :: GHCi a -> GHCi a
timeIt action
  = do b <- isOptionSet ShowTiming
       if not b 
	  then action 
	  else do allocs1 <- io $ getAllocations
		  time1   <- io $ getCPUTime
		  a <- action
		  allocs2 <- io $ getAllocations
		  time2   <- io $ getCPUTime
		  io $ printTimes (fromIntegral (allocs2 - allocs1)) 
				  (time2 - time1)
		  return a

foreign import ccall unsafe "getAllocations" getAllocations :: IO Int64
	-- defined in ghc/rts/Stats.c

printTimes :: Integer -> Integer -> IO ()
printTimes allocs psecs
   = do let secs = (fromIntegral psecs / (10^12)) :: Float
	    secs_str = showFFloat (Just 2) secs
	putStrLn (showSDoc (
		 parens (text (secs_str "") <+> text "secs" <> comma <+> 
			 text (show allocs) <+> text "bytes")))

-----------------------------------------------------------------------------
-- reverting CAFs
	
revertCAFs :: IO ()
revertCAFs = do
  rts_revertCAFs
  turnOffBuffering
	-- Have to turn off buffering again, because we just 
	-- reverted stdout, stderr & stdin to their defaults.

foreign import ccall "revertCAFs" rts_revertCAFs  :: IO ()  
	-- Make it "safe", just in case

-----------------------------------------------------------------------------
-- To flush buffers for the *interpreted* computation we need
-- to refer to *its* stdout/stderr handles

GLOBAL_VAR(flush_interp,       error "no flush_interp", IO ())
GLOBAL_VAR(turn_off_buffering, error "no flush_stdout", IO ())

no_buf_cmd = "System.IO.hSetBuffering System.IO.stdout System.IO.NoBuffering" ++
	     " Prelude.>> System.IO.hSetBuffering System.IO.stderr System.IO.NoBuffering"
flush_cmd  = "System.IO.hFlush System.IO.stdout Prelude.>> System.IO.hFlush System.IO.stderr"

initInterpBuffering :: GHC.Session -> IO ()
initInterpBuffering session
 = do maybe_hval <- GHC.compileExpr session no_buf_cmd
	
      case maybe_hval of
	Just hval -> writeIORef turn_off_buffering (unsafeCoerce# hval :: IO ())
	other	  -> panic "interactiveUI:setBuffering"
	
      maybe_hval <- GHC.compileExpr session flush_cmd
      case maybe_hval of
	Just hval -> writeIORef flush_interp (unsafeCoerce# hval :: IO ())
	_         -> panic "interactiveUI:flush"

      return ()


flushInterpBuffers :: GHCi ()
flushInterpBuffers
 = io $ do Monad.join (readIORef flush_interp)
           return ()

turnOffBuffering :: IO ()
turnOffBuffering
 = do Monad.join (readIORef turn_off_buffering)
      return ()