/ghc/InteractiveUI.hs

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{-# OPTIONS -fno-cse #-}
-- -fno-cse is needed for GLOBAL_VAR's to behave properly

-----------------------------------------------------------------------------
--
-- GHC Interactive User Interface
--
-- (c) The GHC Team 2005-2006
--
-----------------------------------------------------------------------------

module InteractiveUI (
        interactiveUI,
        GhciSettings(..),
        defaultGhciSettings,
        ghciCommands,
        ghciWelcomeMsg
    ) where

#include "HsVersions.h"

-- GHCi
import qualified GhciMonad ( args, runStmt )
import GhciMonad hiding ( args, runStmt )
import GhciTags
import Debugger

-- The GHC interface
import DynFlags
import GhcMonad ( modifySession )
import qualified GHC
import GHC ( LoadHowMuch(..), Target(..),  TargetId(..), InteractiveImport(..),
             TyThing(..), Phase, BreakIndex, Resume, SingleStep, Ghc,
             handleSourceError )
import HsImpExp
import HscTypes ( tyThingParent_maybe, handleFlagWarnings, getSafeMode, hsc_IC, 
                  setInteractivePrintName )
import Module
import Name
import Packages ( trusted, getPackageDetails, exposed, exposedModules, pkgIdMap )
import PprTyThing
import RdrName ( getGRE_NameQualifier_maybes )
import SrcLoc
import qualified Lexer

import StringBuffer
import UniqFM ( eltsUFM )
import Outputable hiding ( printForUser, printForUserPartWay, bold )

-- Other random utilities
import BasicTypes hiding ( isTopLevel )
import Config
import Digraph
import Encoding
import FastString
import Linker
import Maybes ( orElse, expectJust )
import NameSet
import Panic hiding ( showException )
import Util

-- Haskell Libraries
import System.Console.Haskeline as Haskeline

import Control.Applicative hiding (empty)
import Control.Monad as Monad
import Control.Monad.Trans.Class
import Control.Monad.IO.Class

import Data.Array
import qualified Data.ByteString.Char8 as BS
import Data.Char
import Data.Function
import Data.IORef ( IORef, readIORef, writeIORef )
import Data.List ( find, group, intercalate, intersperse, isPrefixOf, nub,
                   partition, sort, sortBy )
import Data.Maybe

import Exception hiding (catch)

import Foreign.C
import Foreign.Safe

import System.Directory
import System.Environment
import System.Exit ( exitWith, ExitCode(..) )
import System.FilePath
import System.IO
import System.IO.Error
import System.IO.Unsafe ( unsafePerformIO )
import System.Process
import Text.Printf
import Text.Read ( readMaybe )

#ifndef mingw32_HOST_OS
import System.Posix hiding ( getEnv )
#else
import qualified System.Win32
#endif

import GHC.Exts ( unsafeCoerce# )
import GHC.IO.Exception ( IOErrorType(InvalidArgument) )
import GHC.IO.Handle ( hFlushAll )
import GHC.TopHandler ( topHandler )


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

data GhciSettings = GhciSettings {
        availableCommands :: [Command],
        shortHelpText     :: String,
        fullHelpText      :: String,
        defPrompt         :: String,
        defPrompt2        :: String
    }

defaultGhciSettings :: GhciSettings
defaultGhciSettings =
    GhciSettings {
        availableCommands = ghciCommands,
        shortHelpText     = defShortHelpText,
        fullHelpText      = defFullHelpText,
        defPrompt         = default_prompt,
        defPrompt2        = default_prompt2
    }

ghciWelcomeMsg :: String
ghciWelcomeMsg = "GHCi, version " ++ cProjectVersion ++
                 ": http://www.haskell.org/ghc/  :? for help"

cmdName :: Command -> String
cmdName (n,_,_) = n

GLOBAL_VAR(macros_ref, [], [Command])

ghciCommands :: [Command]
ghciCommands = [
  -- Hugs users are accustomed to :e, so make sure it doesn't overlap
  ("?",         keepGoing help,                 noCompletion),
  ("add",       keepGoingPaths addModule,       completeFilename),
  ("abandon",   keepGoing abandonCmd,           noCompletion),
  ("break",     keepGoing breakCmd,             completeIdentifier),
  ("back",      keepGoing backCmd,              noCompletion),
  ("browse",    keepGoing' (browseCmd False),   completeModule),
  ("browse!",   keepGoing' (browseCmd True),    completeModule),
  ("cd",        keepGoing' changeDirectory,     completeFilename),
  ("check",     keepGoing' checkModule,         completeHomeModule),
  ("continue",  keepGoing continueCmd,          noCompletion),
  ("complete",  keepGoing completeCmd,          noCompletion),
  ("cmd",       keepGoing cmdCmd,               completeExpression),
  ("ctags",     keepGoing createCTagsWithLineNumbersCmd, completeFilename),
  ("ctags!",    keepGoing createCTagsWithRegExesCmd, completeFilename),
  ("def",       keepGoing (defineMacro False),  completeExpression),
  ("def!",      keepGoing (defineMacro True),   completeExpression),
  ("delete",    keepGoing deleteCmd,            noCompletion),
  ("edit",      keepGoing' editFile,            completeFilename),
  ("etags",     keepGoing createETagsFileCmd,   completeFilename),
  ("force",     keepGoing forceCmd,             completeExpression),
  ("forward",   keepGoing forwardCmd,           noCompletion),
  ("help",      keepGoing help,                 noCompletion),
  ("history",   keepGoing historyCmd,           noCompletion),
  ("info",      keepGoing' (info False),        completeIdentifier),
  ("info!",     keepGoing' (info True),         completeIdentifier),
  ("issafe",    keepGoing' isSafeCmd,           completeModule),
  ("kind",      keepGoing' (kindOfType False),  completeIdentifier),
  ("kind!",     keepGoing' (kindOfType True),   completeIdentifier),
  ("load",      keepGoingPaths loadModule_,     completeHomeModuleOrFile),
  ("list",      keepGoing' listCmd,             noCompletion),
  ("module",    keepGoing moduleCmd,            completeSetModule),
  ("main",      keepGoing runMain,              completeFilename),
  ("print",     keepGoing printCmd,             completeExpression),
  ("quit",      quit,                           noCompletion),
  ("reload",    keepGoing' reloadModule,        noCompletion),
  ("run",       keepGoing runRun,               completeFilename),
  ("script",    keepGoing' scriptCmd,           completeFilename),
  ("set",       keepGoing setCmd,               completeSetOptions),
  ("seti",      keepGoing setiCmd,              completeSeti),
  ("show",      keepGoing showCmd,              completeShowOptions),
  ("showi",     keepGoing showiCmd,             completeShowiOptions),
  ("sprint",    keepGoing sprintCmd,            completeExpression),
  ("step",      keepGoing stepCmd,              completeIdentifier),
  ("steplocal", keepGoing stepLocalCmd,         completeIdentifier),
  ("stepmodule",keepGoing stepModuleCmd,        completeIdentifier),
  ("type",      keepGoing' typeOfExpr,          completeExpression),
  ("trace",     keepGoing traceCmd,             completeExpression),
  ("undef",     keepGoing undefineMacro,        completeMacro),
  ("unset",     keepGoing unsetOptions,         completeSetOptions)
  ]


-- We initialize readline (in the interactiveUI function) to use
-- word_break_chars as the default set of completion word break characters.
-- This can be overridden for a particular command (for example, filename
-- expansion shouldn't consider '/' to be a word break) by setting the third
-- entry in the Command tuple above.
--
-- NOTE: in order for us to override the default correctly, any custom entry
-- must be a SUBSET of word_break_chars.
word_break_chars :: String
word_break_chars = let symbols = "!#$%&*+/<=>?@\\^|-~"
                       specials = "(),;[]`{}"
                       spaces = " \t\n"
                   in spaces ++ specials ++ symbols

flagWordBreakChars :: String
flagWordBreakChars = " \t\n"


keepGoing :: (String -> GHCi ()) -> (String -> InputT GHCi Bool)
keepGoing a str = keepGoing' (lift . a) str

keepGoing' :: Monad m => (String -> m ()) -> String -> m Bool
keepGoing' a str = a str >> return False

keepGoingPaths :: ([FilePath] -> InputT GHCi ()) -> (String -> InputT GHCi Bool)
keepGoingPaths a str
 = do case toArgs str of
          Left err -> liftIO $ hPutStrLn stderr err
          Right args -> a args
      return False

defShortHelpText :: String
defShortHelpText = "use :? for help.\n"

defFullHelpText :: String
defFullHelpText =
  " Commands available from the prompt:\n" ++
  "\n" ++
  "   <statement>                 evaluate/run <statement>\n" ++
  "   :                           repeat last command\n" ++
  "   :{\\n ..lines.. \\n:}\\n       multiline command\n" ++
  "   :add [*]<module> ...        add module(s) to the current target set\n" ++
  "   :browse[!] [[*]<mod>]       display the names defined by module <mod>\n" ++
  "                               (!: more details; *: all top-level names)\n" ++
  "   :cd <dir>                   change directory to <dir>\n" ++
  "   :cmd <expr>                 run the commands returned by <expr>::IO String\n" ++
  "   :complete <dom> [<rng>] <s> list completions for partial input string\n" ++
  "   :ctags[!] [<file>]          create tags file for Vi (default: \"tags\")\n" ++
  "                               (!: use regex instead of line number)\n" ++
  "   :def <cmd> <expr>           define command :<cmd> (later defined command has\n" ++
  "                               precedence, ::<cmd> is always a builtin command)\n" ++
  "   :edit <file>                edit file\n" ++
  "   :edit                       edit last module\n" ++
  "   :etags [<file>]             create tags file for Emacs (default: \"TAGS\")\n" ++
  "   :help, :?                   display this list of commands\n" ++
  "   :info[!] [<name> ...]       display information about the given names\n" ++
  "                               (!: do not filter instances)\n" ++
  "   :issafe [<mod>]             display safe haskell information of module <mod>\n" ++
  "   :kind <type>                show the kind of <type>\n" ++
  "   :load [*]<module> ...       load module(s) and their dependents\n" ++
  "   :main [<arguments> ...]     run the main function with the given arguments\n" ++
  "   :module [+/-] [*]<mod> ...  set the context for expression evaluation\n" ++
  "   :quit                       exit GHCi\n" ++
  "   :reload                     reload the current module set\n" ++
  "   :run function [<arguments> ...] run the function with the given arguments\n" ++
  "   :script <filename>          run the script <filename>\n" ++
  "   :type <expr>                show the type of <expr>\n" ++
  "   :undef <cmd>                undefine user-defined command :<cmd>\n" ++
  "   :!<command>                 run the shell command <command>\n" ++
  "\n" ++
  " -- Commands for debugging:\n" ++
  "\n" ++
  "   :abandon                    at a breakpoint, abandon current computation\n" ++
  "   :back                       go back in the history (after :trace)\n" ++
  "   :break [<mod>] <l> [<col>]  set a breakpoint at the specified location\n" ++
  "   :break <name>               set a breakpoint on the specified function\n" ++
  "   :continue                   resume after a breakpoint\n" ++
  "   :delete <number>            delete the specified breakpoint\n" ++
  "   :delete *                   delete all breakpoints\n" ++
  "   :force <expr>               print <expr>, forcing unevaluated parts\n" ++
  "   :forward                    go forward in the history (after :back)\n" ++
  "   :history [<n>]              after :trace, show the execution history\n" ++
  "   :list                       show the source code around current breakpoint\n" ++
  "   :list identifier            show the source code for <identifier>\n" ++
  "   :list [<module>] <line>     show the source code around line number <line>\n" ++
  "   :print [<name> ...]         prints a value without forcing its computation\n" ++
  "   :sprint [<name> ...]        simplifed version of :print\n" ++
  "   :step                       single-step after stopping at a breakpoint\n"++
  "   :step <expr>                single-step into <expr>\n"++
  "   :steplocal                  single-step within the current top-level binding\n"++
  "   :stepmodule                 single-step restricted to the current module\n"++
  "   :trace                      trace after stopping at a breakpoint\n"++
  "   :trace <expr>               evaluate <expr> with tracing on (see :history)\n"++

  "\n" ++
  " -- Commands for changing settings:\n" ++
  "\n" ++
  "   :set <option> ...           set options\n" ++
  "   :seti <option> ...          set options for interactive evaluation only\n" ++
  "   :set args <arg> ...         set the arguments returned by System.getArgs\n" ++
  "   :set prog <progname>        set the value returned by System.getProgName\n" ++
  "   :set prompt <prompt>        set the prompt used in GHCi\n" ++
  "   :set prompt2 <prompt>       set the continuation prompt used in GHCi\n" ++
  "   :set editor <cmd>           set the command used for :edit\n" ++
  "   :set stop [<n>] <cmd>       set the command to run when a breakpoint is hit\n" ++
  "   :unset <option> ...         unset options\n" ++
  "\n" ++
  "  Options for ':set' and ':unset':\n" ++
  "\n" ++
  "    +m            allow multiline commands\n" ++
  "    +r            revert top-level expressions after each evaluation\n" ++
  "    +s            print timing/memory stats after each evaluation\n" ++
  "    +t            print type after evaluation\n" ++
  "    -<flags>      most GHC command line flags can also be set here\n" ++
  "                         (eg. -v2, -fglasgow-exts, etc.)\n" ++
  "                    for GHCi-specific flags, see User's Guide,\n"++
  "                    Flag reference, Interactive-mode options\n" ++
  "\n" ++
  " -- Commands for displaying information:\n" ++
  "\n" ++
  "   :show bindings              show the current bindings made at the prompt\n" ++
  "   :show breaks                show the active breakpoints\n" ++
  "   :show context               show the breakpoint context\n" ++
  "   :show imports               show the current imports\n" ++
  "   :show linker                show current linker state\n" ++
  "   :show modules               show the currently loaded modules\n" ++
  "   :show packages              show the currently active package flags\n" ++
  "   :show language              show the currently active language flags\n" ++
  "   :show <setting>             show value of <setting>, which is one of\n" ++
  "                                  [args, prog, prompt, editor, stop]\n" ++
  "   :showi language             show language flags for interactive evaluation\n" ++
  "\n"

findEditor :: IO String
findEditor = do
  getEnv "EDITOR"
    `catchIO` \_ -> do
#if mingw32_HOST_OS
        win <- System.Win32.getWindowsDirectory
        return (win </> "notepad.exe")
#else
        return ""
#endif

foreign import ccall unsafe "rts_isProfiled" isProfiled :: IO CInt

default_progname, default_prompt, default_prompt2, default_stop :: String
default_progname = "<interactive>"
default_prompt = "%s> "
default_prompt2 = "%s| "
default_stop = ""

default_args :: [String]
default_args = []

interactiveUI :: GhciSettings -> [(FilePath, Maybe Phase)] -> Maybe [String]
              -> Ghc ()
interactiveUI config srcs maybe_exprs = do
   -- although GHCi compiles with -prof, it is not usable: the byte-code
   -- compiler and interpreter don't work with profiling.  So we check for
   -- this up front and emit a helpful error message (#2197)
   i <- liftIO $ isProfiled
   when (i /= 0) $
     throwGhcException (InstallationError "GHCi cannot be used when compiled with -prof")

   -- HACK! If we happen to get into an infinite loop (eg the user
   -- types 'let x=x in x' at the prompt), then the thread will block
   -- on a blackhole, and become unreachable during GC.  The GC will
   -- detect that it is unreachable and send it the NonTermination
   -- exception.  However, since the thread is unreachable, everything
   -- it refers to might be finalized, including the standard Handles.
   -- This sounds like a bug, but we don't have a good solution right
   -- now.
   _ <- liftIO $ newStablePtr stdin
   _ <- liftIO $ newStablePtr stdout
   _ <- liftIO $ newStablePtr stderr

    -- Initialise buffering for the *interpreted* I/O system
   initInterpBuffering

   -- The initial set of DynFlags used for interactive evaluation is the same
   -- as the global DynFlags, plus -XExtendedDefaultRules and
   -- -XNoMonomorphismRestriction.
   dflags <- getDynFlags
   let dflags' = (`xopt_set` Opt_ExtendedDefaultRules)
               . (`xopt_unset` Opt_MonomorphismRestriction)
               $ dflags
   GHC.setInteractiveDynFlags dflags'

   liftIO $ when (isNothing maybe_exprs) $ do
        -- Only for GHCi (not runghc and ghc -e):

        -- Turn buffering off for the compiled program's stdout/stderr
        turnOffBuffering
        -- Turn buffering off for GHCi's stdout
        hFlush stdout
        hSetBuffering stdout NoBuffering
        -- We don't want the cmd line to buffer any input that might be
        -- intended for the program, so unbuffer stdin.
        hSetBuffering stdin NoBuffering
#if defined(mingw32_HOST_OS)
        -- On Unix, stdin will use the locale encoding.  The IO library
        -- doesn't do this on Windows (yet), so for now we use UTF-8,
        -- for consistency with GHC 6.10 and to make the tests work.
        hSetEncoding stdin utf8
#endif

   default_editor <- liftIO $ findEditor

   startGHCi (runGHCi srcs maybe_exprs)
        GHCiState{ progname       = default_progname,
                   GhciMonad.args = default_args,
                   prompt         = defPrompt config,
                   prompt2        = defPrompt2 config,
                   stop           = default_stop,
                   editor         = default_editor,
                   options        = [],
                   line_number    = 1,
                   break_ctr      = 0,
                   breaks         = [],
                   tickarrays     = emptyModuleEnv,
                   ghci_commands  = availableCommands config,
                   last_command   = Nothing,
                   cmdqueue       = [],
                   remembered_ctx = [],
                   transient_ctx  = [],
                   ghc_e          = isJust maybe_exprs,
                   short_help     = shortHelpText config,
                   long_help      = fullHelpText config
                 }

   return ()

withGhcAppData :: (FilePath -> IO a) -> IO a -> IO a
withGhcAppData right left = do
    either_dir <- tryIO (getAppUserDataDirectory "ghc")
    case either_dir of
        Right dir ->
            do createDirectoryIfMissing False dir `catchIO` \_ -> return ()
               right dir
        _ -> left

runGHCi :: [(FilePath, Maybe Phase)] -> Maybe [String] -> GHCi ()
runGHCi paths maybe_exprs = do
  dflags <- getDynFlags
  let
   read_dot_files = not (gopt Opt_IgnoreDotGhci dflags)

   current_dir = return (Just ".ghci")

   app_user_dir = liftIO $ withGhcAppData
                    (\dir -> return (Just (dir </> "ghci.conf")))
                    (return Nothing)

   home_dir = do
    either_dir <- liftIO $ tryIO (getEnv "HOME")
    case either_dir of
      Right home -> return (Just (home </> ".ghci"))
      _ -> return Nothing

   canonicalizePath' :: FilePath -> IO (Maybe FilePath)
   canonicalizePath' fp = liftM Just (canonicalizePath fp)
                `catchIO` \_ -> return Nothing

   sourceConfigFile :: FilePath -> GHCi ()
   sourceConfigFile file = do
     exists <- liftIO $ doesFileExist file
     when exists $ do
       dir_ok  <- liftIO $ checkPerms (getDirectory file)
       file_ok <- liftIO $ checkPerms file
       when (dir_ok && file_ok) $ do
         either_hdl <- liftIO $ tryIO (openFile file ReadMode)
         case either_hdl of
           Left _e   -> return ()
           -- NOTE: this assumes that runInputT won't affect the terminal;
           -- can we assume this will always be the case?
           -- This would be a good place for runFileInputT.
           Right hdl ->
               do runInputTWithPrefs defaultPrefs defaultSettings $
                            runCommands $ fileLoop hdl
                  liftIO (hClose hdl `catchIO` \_ -> return ())
     where
      getDirectory f = case takeDirectory f of "" -> "."; d -> d
  --

  setGHCContextFromGHCiState

  when (read_dot_files) $ do
    mcfgs0 <- sequence $ [ current_dir, app_user_dir, home_dir ] ++ map (return . Just ) (ghciScripts dflags)
    mcfgs <- liftIO $ mapM canonicalizePath' (catMaybes mcfgs0)
    mapM_ sourceConfigFile $ nub $ catMaybes mcfgs
        -- nub, because we don't want to read .ghci twice if the
        -- CWD is $HOME.

  -- Perform a :load for files given on the GHCi command line
  -- When in -e mode, if the load fails then we want to stop
  -- immediately rather than going on to evaluate the expression.
  when (not (null paths)) $ do
     ok <- ghciHandle (\e -> do showException e; return Failed) $
                -- TODO: this is a hack.
                runInputTWithPrefs defaultPrefs defaultSettings $
                    loadModule paths
     when (isJust maybe_exprs && failed ok) $
        liftIO (exitWith (ExitFailure 1))

  installInteractivePrint (interactivePrint dflags) (isJust maybe_exprs)

  -- if verbosity is greater than 0, or we are connected to a
  -- terminal, display the prompt in the interactive loop.
  is_tty <- liftIO (hIsTerminalDevice stdin)
  let show_prompt = verbosity dflags > 0 || is_tty

  -- reset line number
  getGHCiState >>= \st -> setGHCiState st{line_number=1}

  case maybe_exprs of
        Nothing ->
          do
            -- enter the interactive loop
            runGHCiInput $ runCommands $ nextInputLine show_prompt is_tty
        Just exprs -> do
            -- just evaluate the expression we were given
            enqueueCommands exprs
            let hdle e = do st <- getGHCiState
                            -- flush the interpreter's stdout/stderr on exit (#3890)
                            flushInterpBuffers
                            -- Jump through some hoops to get the
                            -- current progname in the exception text:
                            -- <progname>: <exception>
                            liftIO $ withProgName (progname st)
                                   $ topHandler e
                                   -- this used to be topHandlerFastExit, see #2228
            runInputTWithPrefs defaultPrefs defaultSettings $ do
                runCommands' hdle (return Nothing)

  -- and finally, exit
  liftIO $ when (verbosity dflags > 0) $ putStrLn "Leaving GHCi."

runGHCiInput :: InputT GHCi a -> GHCi a
runGHCiInput f = do
    dflags <- getDynFlags
    histFile <- if gopt Opt_GhciHistory dflags
                then liftIO $ withGhcAppData (\dir -> return (Just (dir </> "ghci_history")))
                                             (return Nothing)
                else return Nothing
    runInputT
        (setComplete ghciCompleteWord $ defaultSettings {historyFile = histFile})
        f

-- | How to get the next input line from the user
nextInputLine :: Bool -> Bool -> InputT GHCi (Maybe String)
nextInputLine show_prompt is_tty
  | is_tty = do
    prmpt <- if show_prompt then lift mkPrompt else return ""
    r <- getInputLine prmpt
    incrementLineNo
    return r
  | otherwise = do
    when show_prompt $ lift mkPrompt >>= liftIO . putStr
    fileLoop stdin

-- NOTE: We only read .ghci files if they are owned by the current user,
-- and aren't world writable.  Otherwise, we could be accidentally
-- running code planted by a malicious third party.

-- Furthermore, We only read ./.ghci if . is owned by the current user
-- and isn't writable by anyone else.  I think this is sufficient: we
-- don't need to check .. and ../.. etc. because "."  always refers to
-- the same directory while a process is running.

checkPerms :: String -> IO Bool
#ifdef mingw32_HOST_OS
checkPerms _ = return True
#else
checkPerms name =
  handleIO (\_ -> return False) $ do
    st <- getFileStatus name
    me <- getRealUserID
    if fileOwner st /= me then do
        putStrLn $ "WARNING: " ++ name ++ " is owned by someone else, IGNORING!"
        return False
     else do
        let mode = System.Posix.fileMode st
        if (groupWriteMode == (mode `intersectFileModes` groupWriteMode))
            || (otherWriteMode == (mode `intersectFileModes` otherWriteMode))
            then do
                putStrLn $ "*** WARNING: " ++ name ++
                           " is writable by someone else, IGNORING!"
                return False
            else return True
#endif

incrementLineNo :: InputT GHCi ()
incrementLineNo = do
   st <- lift $ getGHCiState
   let ln = 1+(line_number st)
   lift $ setGHCiState st{line_number=ln}

fileLoop :: Handle -> InputT GHCi (Maybe String)
fileLoop hdl = do
   l <- liftIO $ tryIO $ hGetLine hdl
   case l of
        Left e | isEOFError e              -> return Nothing
               | -- as we share stdin with the program, the program
                 -- might have already closed it, so we might get a
                 -- handle-closed exception. We therefore catch that
                 -- too.
                 isIllegalOperation e      -> return Nothing
               | InvalidArgument <- etype  -> return Nothing
               | otherwise                 -> liftIO $ ioError e
                where etype = ioeGetErrorType e
                -- treat InvalidArgument in the same way as EOF:
                -- this can happen if the user closed stdin, or
                -- perhaps did getContents which closes stdin at
                -- EOF.
        Right l' -> do
           incrementLineNo
           return (Just l')

mkPrompt :: GHCi String
mkPrompt = do
  imports <- GHC.getContext
  resumes <- GHC.getResumeContext

  context_bit <-
        case resumes of
            [] -> return empty
            r:_ -> do
                let ix = GHC.resumeHistoryIx r
                if ix == 0
                   then return (brackets (ppr (GHC.resumeSpan r)) <> space)
                   else do
                        let hist = GHC.resumeHistory r !! (ix-1)
                        pan <- GHC.getHistorySpan hist
                        return (brackets (ppr (negate ix) <> char ':'
                                          <+> ppr pan) <> space)
  let
        dots | _:rs <- resumes, not (null rs) = text "... "
             | otherwise = empty

        rev_imports = reverse imports -- rightmost are the most recent
        modules_bit =
             hsep [ char '*' <> ppr m | IIModule m <- rev_imports ] <+>
             hsep (map ppr [ myIdeclName d | IIDecl d <- rev_imports ])

         --  use the 'as' name if there is one
        myIdeclName d | Just m <- ideclAs d = m
                      | otherwise           = unLoc (ideclName d)

        deflt_prompt = dots <> context_bit <> modules_bit

        f ('%':'s':xs) = deflt_prompt <> f xs
        f ('%':'%':xs) = char '%' <> f xs
        f (x:xs) = char x <> f xs
        f [] = empty

  st <- getGHCiState
  dflags <- getDynFlags
  return (showSDoc dflags (f (prompt st)))


queryQueue :: GHCi (Maybe String)
queryQueue = do
  st <- getGHCiState
  case cmdqueue st of
    []   -> return Nothing
    c:cs -> do setGHCiState st{ cmdqueue = cs }
               return (Just c)

-- Reconfigurable pretty-printing Ticket #5461
installInteractivePrint :: Maybe String -> Bool -> GHCi ()
installInteractivePrint Nothing _  = return ()
installInteractivePrint (Just ipFun) exprmode = do
  ok <- trySuccess $ do
                (name:_) <- GHC.parseName ipFun
                modifySession (\he -> let new_ic = setInteractivePrintName (hsc_IC he) name 
                                      in he{hsc_IC = new_ic})
                return Succeeded

  when (failed ok && exprmode) $ liftIO (exitWith (ExitFailure 1))

-- | The main read-eval-print loop
runCommands :: InputT GHCi (Maybe String) -> InputT GHCi ()
runCommands = runCommands' handler

runCommands' :: (SomeException -> GHCi Bool) -- ^ Exception handler
             -> InputT GHCi (Maybe String) -> InputT GHCi ()
runCommands' eh gCmd = do
    b <- ghandle (\e -> case fromException e of
                          Just UserInterrupt -> return $ Just False
                          _ -> case fromException e of
                                 Just ghce ->
                                   do liftIO (print (ghce :: GhcException))
                                      return Nothing
                                 _other ->
                                   liftIO (Exception.throwIO e))
            (runOneCommand eh gCmd)
    case b of
      Nothing -> return ()
      Just _  -> runCommands' eh gCmd

-- | Evaluate a single line of user input (either :<command> or Haskell code)
runOneCommand :: (SomeException -> GHCi Bool) -> InputT GHCi (Maybe String)
            -> InputT GHCi (Maybe Bool)
runOneCommand eh gCmd = do
  -- run a previously queued command if there is one, otherwise get new
  -- input from user
  mb_cmd0 <- noSpace (lift queryQueue)
  mb_cmd1 <- maybe (noSpace gCmd) (return . Just) mb_cmd0
  case mb_cmd1 of
    Nothing -> return Nothing
    Just c  -> ghciHandle (\e -> lift $ eh e >>= return . Just) $
             handleSourceError printErrorAndKeepGoing
               (doCommand c)
               -- source error's are handled by runStmt
               -- is the handler necessary here?
  where
    printErrorAndKeepGoing err = do
        GHC.printException err
        return $ Just True

    noSpace q = q >>= maybe (return Nothing)
                            (\c -> case removeSpaces c of
                                     ""   -> noSpace q
                                     ":{" -> multiLineCmd q
                                     c'   -> return (Just c') )
    multiLineCmd q = do
      st <- lift getGHCiState
      let p = prompt st
      lift $ setGHCiState st{ prompt = prompt2 st }
      mb_cmd <- collectCommand q ""
      lift $ getGHCiState >>= \st' -> setGHCiState st'{ prompt = p }
      return mb_cmd
    -- we can't use removeSpaces for the sublines here, so
    -- multiline commands are somewhat more brittle against
    -- fileformat errors (such as \r in dos input on unix),
    -- we get rid of any extra spaces for the ":}" test;
    -- we also avoid silent failure if ":}" is not found;
    -- and since there is no (?) valid occurrence of \r (as
    -- opposed to its String representation, "\r") inside a
    -- ghci command, we replace any such with ' ' (argh:-(
    collectCommand q c = q >>=
      maybe (liftIO (ioError collectError))
            (\l->if removeSpaces l == ":}"
                 then return (Just $ removeSpaces c)
                 else collectCommand q (c ++ "\n" ++ map normSpace l))
      where normSpace '\r' = ' '
            normSpace   x  = x
    -- SDM (2007-11-07): is userError the one to use here?
    collectError = userError "unterminated multiline command :{ .. :}"

    -- | Handle a line of input
    doCommand :: String -> InputT GHCi (Maybe Bool)

    -- command
    doCommand (':' : cmd) = do
      result <- specialCommand cmd
      case result of
        True -> return Nothing
        _    -> return $ Just True

    -- haskell
    doCommand stmt = do
      ml <- lift $ isOptionSet Multiline
      if ml
        then do
          mb_stmt <- checkInputForLayout stmt gCmd
          case mb_stmt of
            Nothing      -> return $ Just True
            Just ml_stmt -> do
              result <- timeIt $ lift $ runStmt ml_stmt GHC.RunToCompletion
              return $ Just result
        else do
          result <- timeIt $ lift $ runStmt stmt GHC.RunToCompletion
          return $ Just result

-- #4316
-- lex the input.  If there is an unclosed layout context, request input
checkInputForLayout :: String -> InputT GHCi (Maybe String)
                    -> InputT GHCi (Maybe String)
checkInputForLayout stmt getStmt = do
   dflags' <- lift $ getDynFlags
   let dflags = xopt_set dflags' Opt_AlternativeLayoutRule
   st0 <- lift $ getGHCiState
   let buf'   =  stringToStringBuffer stmt
       loc    = mkRealSrcLoc (fsLit (progname st0)) (line_number st0) 1
       pstate = Lexer.mkPState dflags buf' loc
   case Lexer.unP goToEnd pstate of
     (Lexer.POk _ False) -> return $ Just stmt
     _other              -> do
       st1 <- lift getGHCiState
       let p = prompt st1
       lift $ setGHCiState st1{ prompt = prompt2 st1 }
       mb_stmt <- ghciHandle (\ex -> case fromException ex of
                            Just UserInterrupt -> return Nothing
                            _ -> case fromException ex of
                                 Just ghce ->
                                   do liftIO (print (ghce :: GhcException))
                                      return Nothing
                                 _other -> liftIO (Exception.throwIO ex))
                     getStmt
       lift $ getGHCiState >>= \st' -> setGHCiState st'{ prompt = p }
       -- the recursive call does not recycle parser state
       -- as we use a new string buffer
       case mb_stmt of
         Nothing  -> return Nothing
         Just str -> if str == ""
           then return $ Just stmt
           else do
             checkInputForLayout (stmt++"\n"++str) getStmt
     where goToEnd = do
             eof <- Lexer.nextIsEOF
             if eof
               then Lexer.activeContext
               else Lexer.lexer return >> goToEnd

enqueueCommands :: [String] -> GHCi ()
enqueueCommands cmds = do
  st <- getGHCiState
  setGHCiState st{ cmdqueue = cmds ++ cmdqueue st }

-- | If we one of these strings prefixes a command, then we treat it as a decl
-- rather than a stmt.
declPrefixes :: [String]
declPrefixes = ["class ","data ","newtype ","type ","instance ", "deriving ",
                "foreign ", "default ", "default("]

-- | Entry point to execute some haskell code from user
runStmt :: String -> SingleStep -> GHCi Bool
runStmt stmt step
 -- empty
 | null (filter (not.isSpace) stmt)
 = return False

 -- import
 | "import " `isPrefixOf` stmt
 = do addImportToContext stmt; return False

 -- data, class, newtype...
 | any (flip isPrefixOf stmt) declPrefixes
 = do _ <- liftIO $ tryIO $ hFlushAll stdin
      result <- GhciMonad.runDecls stmt
      afterRunStmt (const True) (GHC.RunOk result)

 | otherwise
 = do -- In the new IO library, read handles buffer data even if the Handle
      -- is set to NoBuffering.  This causes problems for GHCi where there
      -- are really two stdin Handles.  So we flush any bufferred data in
      -- GHCi's stdin Handle here (only relevant if stdin is attached to
      -- a file, otherwise the read buffer can't be flushed).
      _ <- liftIO $ tryIO $ hFlushAll stdin
      m_result <- GhciMonad.runStmt stmt step
      case m_result of
        Nothing     -> return False
        Just result -> afterRunStmt (const True) result

-- | Clean up the GHCi environment after a statement has run
afterRunStmt :: (SrcSpan -> Bool) -> GHC.RunResult -> GHCi Bool
afterRunStmt _ (GHC.RunException e) = liftIO $ Exception.throwIO e
afterRunStmt step_here run_result = do
  resumes <- GHC.getResumeContext
  case run_result of
     GHC.RunOk names -> do
        show_types <- isOptionSet ShowType
        when show_types $ printTypeOfNames names
     GHC.RunBreak _ names mb_info
         | isNothing  mb_info ||
           step_here (GHC.resumeSpan $ head resumes) -> do
               mb_id_loc <- toBreakIdAndLocation mb_info
               let bCmd = maybe "" ( \(_,l) -> onBreakCmd l ) mb_id_loc
               if (null bCmd)
                 then printStoppedAtBreakInfo (head resumes) names
                 else enqueueCommands [bCmd]
               -- run the command set with ":set stop <cmd>"
               st <- getGHCiState
               enqueueCommands [stop st]
               return ()
         | otherwise -> resume step_here GHC.SingleStep >>=
                        afterRunStmt step_here >> return ()
     _ -> return ()

  flushInterpBuffers
  liftIO installSignalHandlers
  b <- isOptionSet RevertCAFs
  when b revertCAFs

  return (case run_result of GHC.RunOk _ -> True; _ -> False)

toBreakIdAndLocation ::
  Maybe GHC.BreakInfo -> GHCi (Maybe (Int, BreakLocation))
toBreakIdAndLocation Nothing = return Nothing
toBreakIdAndLocation (Just inf) = do
  let md = GHC.breakInfo_module inf
      nm = GHC.breakInfo_number inf
  st <- getGHCiState
  return $ listToMaybe [ id_loc | id_loc@(_,loc) <- breaks st,
                                  breakModule loc == md,
                                  breakTick loc == nm ]

printStoppedAtBreakInfo :: Resume -> [Name] -> GHCi ()
printStoppedAtBreakInfo res names = do
  printForUser $ ptext (sLit "Stopped at") <+>
    ppr (GHC.resumeSpan res)
  --  printTypeOfNames session names
  let namesSorted = sortBy compareNames names
  tythings <- catMaybes `liftM` mapM GHC.lookupName namesSorted
  docs <- mapM pprTypeAndContents [i | AnId i <- tythings]
  printForUserPartWay $ vcat docs

printTypeOfNames :: [Name] -> GHCi ()
printTypeOfNames names
 = mapM_ (printTypeOfName ) $ sortBy compareNames names

compareNames :: Name -> Name -> Ordering
n1 `compareNames` n2 = compareWith n1 `compare` compareWith n2
    where compareWith n = (getOccString n, getSrcSpan n)

printTypeOfName :: Name -> GHCi ()
printTypeOfName n
   = do maybe_tything <- GHC.lookupName n
        case maybe_tything of
            Nothing    -> return ()
            Just thing -> printTyThing thing


data MaybeCommand = GotCommand Command | BadCommand | NoLastCommand

-- | Entry point for execution a ':<command>' input from user
specialCommand :: String -> InputT GHCi Bool
specialCommand ('!':str) = lift $ shellEscape (dropWhile isSpace str)
specialCommand str = do
  let (cmd,rest) = break isSpace str
  maybe_cmd <- lift $ lookupCommand cmd
  htxt <- lift $ short_help `fmap` getGHCiState
  case maybe_cmd of
    GotCommand (_,f,_) -> f (dropWhile isSpace rest)
    BadCommand ->
      do liftIO $ hPutStr stdout ("unknown command ':" ++ cmd ++ "'\n"
                           ++ htxt)
         return False
    NoLastCommand ->
      do liftIO $ hPutStr stdout ("there is no last command to perform\n"
                           ++ htxt)
         return False

shellEscape :: String -> GHCi Bool
shellEscape str = liftIO (system str >> return False)

lookupCommand :: String -> GHCi (MaybeCommand)
lookupCommand "" = do
  st <- getGHCiState
  case last_command st of
      Just c -> return $ GotCommand c
      Nothing -> return NoLastCommand
lookupCommand str = do
  mc <- lookupCommand' str
  st <- getGHCiState
  setGHCiState st{ last_command = mc }
  return $ case mc of
           Just c -> GotCommand c
           Nothing -> BadCommand

lookupCommand' :: String -> GHCi (Maybe Command)
lookupCommand' ":" = return Nothing
lookupCommand' str' = do
  macros    <- liftIO $ readIORef macros_ref
  ghci_cmds <- ghci_commands `fmap` getGHCiState
  let{ (str, cmds) = case str' of
      ':' : rest -> (rest, ghci_cmds) -- "::" selects a builtin command
      _ -> (str', ghci_cmds ++ macros) } -- otherwise prefer macros
  -- look for exact match first, then the first prefix match
  return $ case [ c | c <- cmds, str == cmdName c ] of
           c:_ -> Just c
           [] -> case [ c | c@(s,_,_) <- cmds, str `isPrefixOf` s ] of
                 [] -> Nothing
                 c:_ -> Just c

getCurrentBreakSpan :: GHCi (Maybe SrcSpan)
getCurrentBreakSpan = do
  resumes <- GHC.getResumeContext
  case resumes of
    [] -> return Nothing
    (r:_) -> do
        let ix = GHC.resumeHistoryIx r
        if ix == 0
           then return (Just (GHC.resumeSpan r))
           else do
                let hist = GHC.resumeHistory r !! (ix-1)
                pan <- GHC.getHistorySpan hist
                return (Just pan)

getCurrentBreakModule :: GHCi (Maybe Module)
getCurrentBreakModule = do
  resumes <- GHC.getResumeContext
  case resumes of
    [] -> return Nothing
    (r:_) -> do
        let ix = GHC.resumeHistoryIx r
        if ix == 0
           then return (GHC.breakInfo_module `liftM` GHC.resumeBreakInfo r)
           else do
                let hist = GHC.resumeHistory r !! (ix-1)
                return $ Just $ GHC.getHistoryModule  hist

-----------------------------------------------------------------------------
--
-- Commands
--
-----------------------------------------------------------------------------

noArgs :: GHCi () -> String -> GHCi ()
noArgs m "" = m
noArgs _ _  = liftIO $ putStrLn "This command takes no arguments"

withSandboxOnly :: String -> GHCi () -> GHCi ()
withSandboxOnly cmd this = do
   dflags <- getDynFlags
   if not (gopt Opt_GhciSandbox dflags)
      then printForUser (text cmd <+>
                         ptext (sLit "is not supported with -fno-ghci-sandbox"))
      else this

-----------------------------------------------------------------------------
-- :help

help :: String -> GHCi ()
help _ = do
    txt <- long_help `fmap` getGHCiState
    liftIO $ putStr txt

-----------------------------------------------------------------------------
-- :info

info :: Bool -> String -> InputT GHCi ()
info _ "" = throwGhcException (CmdLineError "syntax: ':i <thing-you-want-info-about>'")
info allInfo s  = handleSourceError GHC.printException $ do
    unqual <- GHC.getPrintUnqual
    dflags <- getDynFlags
    sdocs  <- mapM (infoThing allInfo) (words s)
    mapM_ (liftIO . putStrLn . showSDocForUser dflags unqual) sdocs

infoThing :: GHC.GhcMonad m => Bool -> String -> m SDoc
infoThing allInfo str = do
    dflags    <- getDynFlags
    let pefas = gopt Opt_PrintExplicitForalls dflags
    names     <- GHC.parseName str
    mb_stuffs <- mapM (GHC.getInfo allInfo) names
    let filtered = filterOutChildren (\(t,_f,_ci,_fi) -> t) (catMaybes mb_stuffs)
    return $ vcat (intersperse (text "") $ map (pprInfo pefas) filtered)

  -- Filter out names whose parent is also there Good
  -- example is '[]', which is both a type and data
  -- constructor in the same type
filterOutChildren :: (a -> TyThing) -> [a] -> [a]
filterOutChildren get_thing xs
  = filterOut has_parent xs
  where
    all_names = mkNameSet (map (getName . get_thing) xs)
    has_parent x = case tyThingParent_maybe (get_thing x) of
                     Just p  -> getName p `elemNameSet` all_names
                     Nothing -> False

pprInfo :: PrintExplicitForalls
        -> (TyThing, Fixity, [GHC.ClsInst], [GHC.FamInst]) -> SDoc
pprInfo pefas (thing, fixity, cls_insts, fam_insts)
  =  pprTyThingInContextLoc pefas thing
  $$ show_fixity
  $$ vcat (map GHC.pprInstance cls_insts)
  $$ vcat (map GHC.pprFamInst  fam_insts)
  where
    show_fixity
        | fixity == GHC.defaultFixity = empty
        | otherwise                   = ppr fixity <+> pprInfixName (GHC.getName thing)

-----------------------------------------------------------------------------
-- :main

runMain :: String -> GHCi ()
runMain s = case toArgs s of
            Left err   -> liftIO (hPutStrLn stderr err)
            Right args ->
                do dflags <- getDynFlags
                   case mainFunIs dflags of
                       Nothing -> doWithArgs args "main"
                       Just f  -> doWithArgs args f

-----------------------------------------------------------------------------
-- :run

runRun :: String -> GHCi ()
runRun s = case toCmdArgs s of
           Left err          -> liftIO (hPutStrLn stderr err)
           Right (cmd, args) -> doWithArgs args cmd

doWithArgs :: [String] -> String -> GHCi ()
doWithArgs args cmd = enqueueCommands ["System.Environment.withArgs " ++
                                       show args ++ " (" ++ cmd ++ ")"]

-----------------------------------------------------------------------------
-- :cd

changeDirectory :: String -> InputT GHCi ()
changeDirectory "" = do
  -- :cd on its own changes to the user's home directory
  either_dir <- liftIO $ tryIO getHomeDirectory
  case either_dir of
     Left _e -> return ()
     Right dir -> changeDirectory dir
changeDirectory dir = do
  graph <- GHC.getModuleGraph
  when (not (null graph)) $
        liftIO $ putStrLn "Warning: changing directory causes all loaded modules to be unloaded,\nbecause the search path has changed."
  GHC.setTargets []
  _ <- GHC.load LoadAllTargets
  lift $ setContextAfterLoad False []
  GHC.workingDirectoryChanged
  dir' <- expandPath dir
  liftIO $ setCurrentDirectory dir'

trySuccess :: GHC.GhcMonad m => m SuccessFlag -> m SuccessFlag
trySuccess act =
    handleSourceError (\e -> do GHC.printException e
                                return Failed) $ do
      act

-----------------------------------------------------------------------------
-- :edit

editFile :: String -> InputT GHCi ()
editFile str =
  do file <- if null str then lift chooseEditFile else return str
     st <- lift getGHCiState
     let cmd = editor st
     when (null cmd)
       $ throwGhcException (CmdLineError "editor not set, use :set editor")
     code <- liftIO $ system (cmd ++ ' ':file)
     when (code == ExitSuccess)
       $ reloadModule ""

-- The user didn't specify a file so we pick one for them.
-- Our strategy is to pick the first module that failed to load,
-- or otherwise the first target.
--
-- XXX: Can we figure out what happened if the depndecy analysis fails
--      (e.g., because the porgrammeer mistyped the name of a module)?
-- XXX: Can we figure out the location of an error to pass to the editor?
-- XXX: if we could figure out the list of errors that occured during the
-- last load/reaload, then we could start the editor focused on the first
-- of those.
chooseEditFile :: GHCi String
chooseEditFile =
  do let hasFailed x = fmap not $ GHC.isLoaded $ GHC.ms_mod_name x

     graph <- GHC.getModuleGraph
     failed_graph <- filterM hasFailed graph
     let order g  = flattenSCCs $ GHC.topSortModuleGraph True g Nothing
         pick xs  = case xs of
                      x : _ -> GHC.ml_hs_file (GHC.ms_location x)
                      _     -> Nothing

     case pick (order failed_graph) of
       Just file -> return file
       Nothing   ->
         do targets <- GHC.getTargets
            case msum (map fromTarget targets) of
              Just file -> return file
              Nothing   -> throwGhcException (CmdLineError "No files to edit.")

  where fromTarget (GHC.Target (GHC.TargetFile f _) _ _) = Just f
        fromTarget _ = Nothing -- when would we get a module target?


-----------------------------------------------------------------------------
-- :def

defineMacro :: Bool{-overwrite-} -> String -> GHCi ()
defineMacro _ (':':_) =
  liftIO $ putStrLn "macro name cannot start with a colon"
defineMacro overwrite s = do
  let (macro_name, definition) = break isSpace s
  macros <- liftIO (readIORef macros_ref)
  let defined = map cmdName macros
  if (null macro_name)
        then if null defined
                then liftIO $ putStrLn "no macros defined"
                else liftIO $ putStr ("the following macros are defined:\n" ++
                                      unlines defined)
        else do
  if (not overwrite && macro_name `elem` defined)
        then throwGhcException (CmdLineError
                ("macro '" ++ macro_name ++ "' is already defined"))
        else do

  let filtered = [ cmd | cmd <- macros, cmdName cmd /= macro_name ]

  -- give the expression a type signature, so we can be sure we're getting
  -- something of the right type.
  let new_expr = '(' : definition ++ ") :: String -> IO String"

  -- compile the expression
  handleSourceError (\e -> GHC.printException e) $
   do
    hv <- GHC.compileExpr new_expr
    liftIO (writeIORef macros_ref -- later defined macros have precedence
            ((macro_name, lift . runMacro hv, noCompletion) : filtered))

runMacro :: GHC.HValue{-String -> IO String-} -> String -> GHCi Bool
runMacro fun s = do
  str <- liftIO ((unsafeCoerce# fun :: String -> IO String) s)
  -- make sure we force any exceptions in the result, while we are still
  -- inside the exception handler for commands:
  seqList str (return ())
  enqueueCommands (lines str)
  return False


-----------------------------------------------------------------------------
-- :undef

undefineMacro :: String -> GHCi ()
undefineMacro str = mapM_ undef (words str)
 where undef macro_name = do
        cmds <- liftIO (readIORef macros_ref)
        if (macro_name `notElem` map cmdName cmds)
           then throwGhcException (CmdLineError
                ("macro '" ++ macro_name ++ "' is not defined"))
           else do
            liftIO (writeIORef macros_ref (filter ((/= macro_name) . cmdName) cmds))


-----------------------------------------------------------------------------
-- :cmd

cmdCmd :: String -> GHCi ()
cmdCmd str = do
  let expr = '(' : str ++ ") :: IO String"
  handleSourceError (\e -> GHC.printException e) $
   do
    hv <- GHC.compileExpr expr
    cmds <- liftIO $ (unsafeCoerce# hv :: IO String)
    enqueueCommands (lines cmds)
    return ()


-----------------------------------------------------------------------------
-- :check

checkModule :: String -> InputT GHCi ()
checkModule m = do
  let modl = GHC.mkModuleName m
  ok <- handleSourceError (\e -> GHC.printException e >> return False) $ do
          r <- GHC.typecheckModule =<< GHC.parseModule =<< GHC.getModSummary modl
          dflags <- getDynFlags
          liftIO $ putStrLn $ showSDoc dflags $
           case GHC.moduleInfo r of
             cm | Just scope <- GHC.modInfoTopLevelScope cm ->
                let
                    (loc, glob) = ASSERT( all isExternalName scope )
                                  partition ((== modl) . GHC.moduleName . GHC.nameModule) scope
                in
                        (text "global names: " <+> ppr glob) $$
                        (text "local  names: " <+> ppr loc)
        …