{-# LANGUAGE MagicHash #-}

-----------------------------------------------------------------------------
--
-- GHCi Interactive debugging commands 
--
-- Pepe Iborra (supported by Google SoC) 2006
--
-- ToDo: lots of violation of layering here.  This module should
-- decide whether it is above the GHC API (import GHC and nothing
-- else) or below it.
-- 
-----------------------------------------------------------------------------

module Debugger (pprintClosureCommand, showTerm, pprTypeAndContents) where

import Linker
import RtClosureInspect

import GhcMonad
import HscTypes
import Id
import Name
import Var hiding ( varName )
import VarSet
import UniqSupply
import Type
import Kind
import GHC
import Outputable
import PprTyThing
import ErrUtils
import MonadUtils
import DynFlags
import Exception

import Control.Monad
import Data.List
import Data.Maybe
import Data.IORef

import GHC.Exts

-------------------------------------
-- | The :print & friends commands
-------------------------------------
pprintClosureCommand :: GhcMonad m => Bool -> Bool -> String -> m ()
pprintClosureCommand bindThings force str = do
  tythings <- (catMaybes . concat) `liftM`
                 mapM (\w -> GHC.parseName w >>=
                                mapM GHC.lookupName)
                      (words str)
  let ids = [id | AnId id <- tythings]

  -- Obtain the terms and the recovered type information
  (subst, terms) <- mapAccumLM go emptyTvSubst ids

  -- Apply the substitutions obtained after recovering the types
  modifySession $ \hsc_env ->
    hsc_env{hsc_IC = substInteractiveContext (hsc_IC hsc_env) subst}

  -- Finally, print the Terms
  unqual  <- GHC.getPrintUnqual
  docterms <- mapM showTerm terms
  dflags <- getDynFlags
  liftIO $ (printOutputForUser dflags unqual . vcat)
           (zipWith (\id docterm -> ppr id <+> char '=' <+> docterm)
                    ids
                    docterms)
 where
   -- Do the obtainTerm--bindSuspensions-computeSubstitution dance
   go :: GhcMonad m => TvSubst -> Id -> m (TvSubst, Term)
   go subst id = do
       let id' = id `setIdType` substTy subst (idType id) 
       term_    <- GHC.obtainTermFromId maxBound force id'
       term     <- tidyTermTyVars term_
       term'    <- if bindThings &&
                      False == isUnliftedTypeKind (termType term)
                     then bindSuspensions term
                     else return term
     -- Before leaving, we compare the type obtained to see if it's more specific
     --  Then, we extract a substitution,
     --  mapping the old tyvars to the reconstructed types.
       let reconstructed_type = termType term
       hsc_env <- getSession
       case (improveRTTIType hsc_env (idType id) (reconstructed_type)) of
         Nothing     -> return (subst, term')
         Just subst' -> do { traceOptIf Opt_D_dump_rtti
                               (fsep $ [text "RTTI Improvement for", ppr id,
                                text "is the substitution:" , ppr subst'])
                           ; return (subst `unionTvSubst` subst', term')}

   tidyTermTyVars :: GhcMonad m => Term -> m Term
   tidyTermTyVars t =
     withSession $ \hsc_env -> do
     let env_tvs      = tyThingsTyVars $ ic_tythings $ hsc_IC hsc_env
         my_tvs       = termTyVars t
         tvs          = env_tvs `minusVarSet` my_tvs
         tyvarOccName = nameOccName . tyVarName
         tidyEnv      = (initTidyOccEnv (map tyvarOccName (varSetElems tvs))
                        , env_tvs `intersectVarSet` my_tvs)
     return$ mapTermType (snd . tidyOpenType tidyEnv) t

-- | Give names, and bind in the interactive environment, to all the suspensions
--   included (inductively) in a term
bindSuspensions :: GhcMonad m => Term -> m Term
bindSuspensions t = do
      hsc_env <- getSession
      inScope <- GHC.getBindings
      let ictxt        = hsc_IC hsc_env
          prefix       = "_t"
          alreadyUsedNames = map (occNameString . nameOccName . getName) inScope
          availNames   = map ((prefix++) . show) [(1::Int)..] \\ alreadyUsedNames
      availNames_var  <- liftIO $ newIORef availNames
      (t', stuff)     <- liftIO $ foldTerm (nameSuspensionsAndGetInfos availNames_var) t
      let (names, tys, hvals) = unzip3 stuff
      let ids = [ mkVanillaGlobal name ty 
                | (name,ty) <- zip names tys]
          new_ic = extendInteractiveContextWithIds ictxt ids
      liftIO $ extendLinkEnv (zip names hvals)
      modifySession $ \_ -> hsc_env {hsc_IC = new_ic }
      return t'
     where

--    Processing suspensions. Give names and recopilate info
        nameSuspensionsAndGetInfos :: IORef [String] ->
                                       TermFold (IO (Term, [(Name,Type,HValue)]))
        nameSuspensionsAndGetInfos freeNames = TermFold
                      {
                        fSuspension = doSuspension freeNames
                      , fTerm = \ty dc v tt -> do
                                    tt' <- sequence tt
                                    let (terms,names) = unzip tt'
                                    return (Term ty dc v terms, concat names)
                      , fPrim    = \ty n ->return (Prim ty n,[])
                      , fNewtypeWrap  = 
                                \ty dc t -> do 
                                    (term, names) <- t
                                    return (NewtypeWrap ty dc term, names)
                      , fRefWrap = \ty t -> do
                                    (term, names) <- t 
                                    return (RefWrap ty term, names)
                      }
        doSuspension freeNames ct ty hval _name = do
          name <- atomicModifyIORef freeNames (\x->(tail x, head x))
          n <- newGrimName name
          return (Suspension ct ty hval (Just n), [(n,ty,hval)])


--  A custom Term printer to enable the use of Show instances
showTerm :: GhcMonad m => Term -> m SDoc
showTerm term = do
    dflags       <- GHC.getSessionDynFlags
    if gopt Opt_PrintEvldWithShow dflags
       then cPprTerm (liftM2 (++) (\_y->[cPprShowable]) cPprTermBase) term
       else cPprTerm cPprTermBase term
 where
  cPprShowable prec t@Term{ty=ty, val=val} =
    if not (isFullyEvaluatedTerm t)
     then return Nothing
     else do
        hsc_env <- getSession
        dflags  <- GHC.getSessionDynFlags
        do
           (new_env, bname) <- bindToFreshName hsc_env ty "showme"
           setSession new_env
                      -- XXX: this tries to disable logging of errors
                      -- does this still do what it is intended to do
                      -- with the changed error handling and logging?
           let noop_log _ _ _ _ _ = return ()
               expr = "show " ++ showPpr dflags bname
           _ <- GHC.setSessionDynFlags dflags{log_action=noop_log}
           txt_ <- withExtendedLinkEnv [(bname, val)]
                                       (GHC.compileExpr expr)
           let myprec = 10 -- application precedence. TODO Infix constructors
           let txt = unsafeCoerce# txt_ :: [a]
           if not (null txt) then
             return $ Just $ cparen (prec >= myprec && needsParens txt)
                                    (text txt)
            else return Nothing
         `gfinally` do
           setSession hsc_env
           GHC.setSessionDynFlags dflags
  cPprShowable prec NewtypeWrap{ty=new_ty,wrapped_term=t} = 
      cPprShowable prec t{ty=new_ty}
  cPprShowable _ _ = return Nothing

  needsParens ('"':_) = False   -- some simple heuristics to see whether parens
                                -- are redundant in an arbitrary Show output
  needsParens ('(':_) = False
  needsParens txt = ' ' `elem` txt


  bindToFreshName hsc_env ty userName = do
    name <- newGrimName userName
    let id       = mkVanillaGlobal name ty 
        new_ic   = extendInteractiveContextWithIds (hsc_IC hsc_env) [id]
    return (hsc_env {hsc_IC = new_ic }, name)

--    Create new uniques and give them sequentially numbered names
newGrimName :: MonadIO m => String -> m Name
newGrimName userName  = do
    us <- liftIO $ mkSplitUniqSupply 'b'
    let unique  = uniqFromSupply us
        occname = mkOccName varName userName
        name    = mkInternalName unique occname noSrcSpan
    return name

pprTypeAndContents :: GhcMonad m => Id -> m SDoc
pprTypeAndContents id = do
  dflags  <- GHC.getSessionDynFlags
  let pcontents = gopt Opt_PrintBindContents dflags
      pprdId    = (PprTyThing.pprTyThing . AnId) id
  if pcontents 
    then do
      let depthBound = 100
      -- If the value is an exception, make sure we catch it and
      -- show the exception, rather than propagating the exception out.
      e_term <- gtry $ GHC.obtainTermFromId depthBound False id
      docs_term <- case e_term of
                      Right term -> showTerm term
                      Left  exn  -> return (text "*** Exception:" <+>
                                            text (show (exn :: SomeException)))
      return $ pprdId <+> equals <+> docs_term
    else return pprdId

--------------------------------------------------------------
-- Utils 

traceOptIf :: GhcMonad m => DumpFlag -> SDoc -> m ()
traceOptIf flag doc = do
  dflags <- GHC.getSessionDynFlags
  when (dopt flag dflags) $ liftIO $ printInfoForUser dflags alwaysQualify doc
