    {-# LANGUAGE CPP #-}

    {-# OPTIONS_GHC -fno-cse #-}

    {-# OPTIONS_GHC -fno-warn-orphans #-}

    module Agda.Interaction.InteractionTop
      ( module Agda.Interaction.InteractionTop
      )
      where

    import Prelude hiding (null)

    import Control.Applicative hiding (empty)
    import Control.Concurrent
    import Control.Concurrent.Async
    import Control.Concurrent.STM.TChan
    import Control.Concurrent.STM.TVar
    import qualified Control.Exception as E
    import Control.Monad.Identity
    import Control.Monad.Reader
    import Control.Monad.State
    import Control.Monad.STM

    import qualified Data.Char as Char
    import Data.Foldable (Foldable)
    import Data.Function
    import qualified Data.List as List
    import Data.Maybe
    import Data.Map (Map)
    import qualified Data.Map as Map
    import Data.Monoid
    import Data.Traversable (Traversable)
    import qualified Data.Traversable as Trav

    import System.Directory
    import System.FilePath

    import Agda.TypeChecking.Monad as TM
      hiding (initState, setCommandLineOptions)
    import qualified Agda.TypeChecking.Monad as TM
    import qualified Agda.TypeChecking.Pretty as TCP
    import Agda.TypeChecking.Rules.Term (checkExpr, isType_)
    import Agda.TypeChecking.Errors
    import Agda.TypeChecking.MetaVars.Mention

    import Agda.Syntax.Fixity
    import Agda.Syntax.Position
    import Agda.Syntax.Parser
    import Agda.Syntax.Common
    import Agda.Syntax.Literal
    import Agda.Syntax.Concrete as C
    import Agda.Syntax.Concrete.Generic as C
    import Agda.Syntax.Concrete.Pretty ()
    import Agda.Syntax.Abstract as A
    import Agda.Syntax.Abstract.Pretty
    import qualified Agda.Syntax.Internal as I
    import Agda.Syntax.Info (mkDefInfo)
    import Agda.Syntax.Translation.ConcreteToAbstract
    import Agda.Syntax.Translation.AbstractToConcrete hiding (withScope)
    import Agda.Syntax.Scope.Base

    import Agda.Interaction.FindFile
    import Agda.Interaction.Options
    import Agda.Interaction.Options.Lenses as Lenses
    import Agda.Interaction.MakeCase
    import Agda.Interaction.SearchAbout
    import Agda.Interaction.Response hiding (Function, ExtendedLambda)
    import qualified Agda.Interaction.Response as R
    import qualified Agda.Interaction.BasicOps as B
    import Agda.Interaction.BasicOps hiding (whyInScope)
    import Agda.Interaction.Highlighting.Precise hiding (Error, Postulate)
    import qualified Agda.Interaction.Imports as Imp
    import Agda.TypeChecking.Warnings
    import Agda.Interaction.Highlighting.Generate
    import qualified Agda.Interaction.Highlighting.LaTeX as LaTeX
    import qualified Agda.Interaction.Highlighting.Range as H

    import Agda.Compiler.Common (IsMain (..))
    import Agda.Compiler.Backend

    import Agda.Auto.Auto as Auto

    import Agda.Utils.Except
      ( ExceptT
      , mkExceptT
      , MonadError(catchError, throwError)
      , runExceptT
      )

    import Agda.Utils.Either
    import Agda.Utils.FileName
    import Agda.Utils.Function
    import Agda.Utils.Hash
    import qualified Agda.Utils.HashMap as HMap
    import Agda.Utils.Lens
    import Agda.Utils.Maybe
    import qualified Agda.Utils.Maybe.Strict as Strict
    import Agda.Utils.Monad
    import Agda.Utils.Null
    import Agda.Utils.Pretty as P
    import Agda.Utils.String
    import Agda.Utils.Time
    import Agda.Utils.Tuple

    #include "undefined.h"
    import Agda.Utils.Impossible

    ------------------------------------------------------------------------
    -- The CommandM monad

    -- | Auxiliary state of an interactive computation.

    data CommandState = CommandState
      { theInteractionPoints :: [InteractionId]
        -- ^ The interaction points of the buffer, in the order in which
        --   they appear in the buffer. The interaction points are
        --   recorded in 'theTCState', but when new interaction points are
        --   added by give or refine Agda does not ensure that the ranges
        --   of later interaction points are updated.
      , theCurrentFile       :: Maybe (AbsolutePath, ClockTime)
        -- ^ The file which the state applies to. Only stored if the
        -- module was successfully type checked (potentially with
        -- warnings). The 'ClockTime' is the modification time stamp of
        -- the file when it was last loaded.
      , optionsOnReload :: CommandLineOptions
        -- ^ Reset the options on each reload to these.
      , oldInteractionScopes :: !OldInteractionScopes
        -- ^ We remember (the scope of) old interaction points to make it
        --   possible to parse and compute highlighting information for the
        --   expression that it got replaced by.
      , commandQueue :: !CommandQueue
        -- ^ The command queue.
        --
        -- This queue should only be manipulated by
        -- 'initialiseCommandQueue' and 'maybeAbort'.
      }

    type OldInteractionScopes = Map InteractionId ScopeInfo

    -- | Initial auxiliary interaction state

    initCommandState :: CommandQueue -> CommandState
    initCommandState commandQueue =
      CommandState
        { theInteractionPoints = []
        , theCurrentFile       = Nothing
        , optionsOnReload      = defaultOptions
        , oldInteractionScopes = Map.empty
        , commandQueue         = commandQueue
        }

    -- | Monad for computing answers to interactive commands.
    --
    --   'CommandM' is 'TCM' extended with state 'CommandState'.

    type CommandM = StateT CommandState TCM

    -- | Restore both 'TCState' and 'CommandState'.

    localStateCommandM :: CommandM a -> CommandM a
    localStateCommandM m = do
      cSt <- get
      tcSt <- getTC
      x <- m
      putTC tcSt
      put cSt
      return x

    -- | Restore 'TCState', do not touch 'CommandState'.

    liftLocalState :: TCM a -> CommandM a
    liftLocalState = lift . localTCState

    -- | Build an opposite action to 'lift' for state monads.

    revLift
        :: MonadState st m
        => (forall c . m c -> st -> k (c, st))      -- ^ run
        -> (forall b . k b -> m b)                  -- ^ lift
        -> (forall x . (m a -> k x) -> k x) -> m a  -- ^ reverse lift in double negative position
    revLift run lift f = do
        st <- get
        (a, st) <- lift $ f (`run` st)
        put st
        return a

    revLiftTC
        :: MonadTCState m
        => (forall c . m c -> TCState -> k (c, TCState))  -- ^ run
        -> (forall b . k b -> m b)                        -- ^ lift
        -> (forall x . (m a -> k x) -> k x) -> m a        -- ^ reverse lift in double negative position
    revLiftTC run lift f = do
        st <- getTC
        (a, st) <- lift $ f (`run` st)
        putTC st
        return a

    -- | Opposite of 'liftIO' for 'CommandM'.
    --   Use only if main errors are already catched.

    commandMToIO :: (forall x . (CommandM a -> IO x) -> IO x) -> CommandM a
    commandMToIO ci_i = revLift runStateT lift $ \ct -> revLiftTC runSafeTCM liftIO $ ci_i . (. ct)

    -- | Lift a TCM action transformer to a CommandM action transformer.

    liftCommandMT :: (forall a . TCM a -> TCM a) -> CommandM a -> CommandM a
    liftCommandMT f m = revLift runStateT lift $ f . ($ m)

    -- | Ditto, but restore state.

    liftCommandMTLocalState :: (forall a . TCM a -> TCM a) -> CommandM a -> CommandM a
    liftCommandMTLocalState f = liftCommandMT f . localStateCommandM

    -- | Put a response by the callback function given by 'stInteractionOutputCallback'.

    putResponse :: Response -> CommandM ()
    putResponse = lift . appInteractionOutputCallback

    -- | A Lens for 'theInteractionPoints'.

    modifyTheInteractionPoints :: ([InteractionId] -> [InteractionId]) -> CommandM ()
    modifyTheInteractionPoints f = modify $ \ s ->
      s { theInteractionPoints = f (theInteractionPoints s) }

    -- * Operations for manipulating 'oldInteractionScopes'.

    -- | A Lens for 'oldInteractionScopes'.
    modifyOldInteractionScopes :: (OldInteractionScopes -> OldInteractionScopes) -> CommandM ()
    modifyOldInteractionScopes f = modify $ \ s ->
      s { oldInteractionScopes = f $ oldInteractionScopes s }

    insertOldInteractionScope :: InteractionId -> ScopeInfo -> CommandM ()
    insertOldInteractionScope ii scope = do
      lift $ reportSLn "interaction.scope" 20 $ "inserting old interaction scope " ++ show ii
      modifyOldInteractionScopes $ Map.insert ii scope

    removeOldInteractionScope :: InteractionId -> CommandM ()
    removeOldInteractionScope ii = do
      lift $ reportSLn "interaction.scope" 20 $ "removing old interaction scope " ++ show ii
      modifyOldInteractionScopes $ Map.delete ii

    getOldInteractionScope :: InteractionId -> CommandM ScopeInfo
    getOldInteractionScope ii = do
      ms <- gets $ Map.lookup ii . oldInteractionScopes
      case ms of
        Nothing    -> fail $ "not an old interaction point: " ++ show ii
        Just scope -> return scope

    -- | Do setup and error handling for a command.

    handleCommand_ :: CommandM () -> CommandM ()
    handleCommand_ = handleCommand id (return ())

    handleCommand :: (forall a. CommandM a -> CommandM a) -> CommandM () -> CommandM () -> CommandM ()
    handleCommand wrap onFail cmd = handleNastyErrors $ wrap $ do
        oldState <- getTC

        -- -- Andreas, 2016-11-18 OLD CODE:
        -- -- onFail and handleErr are executed in "new" command state (not TCState).
        -- -- But it seems that if an exception is raised, it is identical to the old state,
        -- -- see code for catchErr.
        -- res <- (`catchErr` (return . Just)) $ Nothing <$ cmd
        -- maybe (return ()) (\ e -> onFail >> handleErr e) res

        -- Andreas, 2016-11-18 NEW CODE: execute onFail and handleErr in handler
        -- which means (looking at catchErr) they run in state s rathern than s'.
        -- Yet, it looks like s == s' in case the command failed.
        cmd `catchErr` \ e -> do
          onFail
          handleErr e
          -- Andreas, 2016-11-18, issue #2174
          -- Reset TCState after error is handled, to get rid of metas created during failed command
          lift $ do
            newPersistentState <- useTC lensPersistentState
            putTC oldState
            lensPersistentState `setTCLens` newPersistentState

      where
        -- Preserves state so we can do unsolved meta highlighting
        catchErr :: CommandM a -> (TCErr -> CommandM a) -> CommandM a
        catchErr m h = do
          s       <- get
          (x, s') <- lift $ do runStateT m s
             `catchError_` \ e ->
               runStateT (h e) s
          put s'
          return x

        -- | Handle every possible kind of error (#637), except for
        -- ThreadKilled, which is used to abort Agda.
        handleNastyErrors :: CommandM () -> CommandM ()
        handleNastyErrors m = commandMToIO $ \ toIO -> do
          let handle e =
                Right <$>
                  (toIO $ handleErr $ Exception noRange $ text $ show e)

              asyncHandler e@AsyncCancelled = return (Left e)

              generalHandler (e :: E.SomeException) = handle e

          r <- ((Right <$> toIO m) `E.catch` asyncHandler)
                 `E.catch` generalHandler
          case r of
            Right x -> return x
            Left e  -> E.throwIO e

        -- | Displays an error and instructs Emacs to jump to the site of the
        -- error. Because this function may switch the focus to another file
        -- the status information is also updated.
        handleErr e = do
            unsolvedNotOK <- lift $ not . optAllowUnsolved <$> pragmaOptions
            meta    <- lift $ computeUnsolvedMetaWarnings
            constr  <- lift $ computeUnsolvedConstraints
            err     <- lift $ errorHighlighting e
            modFile <- lift $ useTC stModuleToSource
            method  <- lift $ viewTC eHighlightingMethod
            let info = compress $ mconcat $
                         -- Errors take precedence over unsolved things.
                         err : if unsolvedNotOK then [meta, constr] else []
            s1 <- lift $ prettyError e
            s2 <- lift $ prettyTCWarnings' =<< Imp.getAllWarningsOfTCErr e
            let strErr  = if null s2 then s1
                                     else delimiter "Error" ++ "\n" ++ s1
            let strWarn = List.intercalate "\n" $ delimiter "Warning(s)"
                                                : filter (not . null) s2
            let str     = if null s2 then strErr else strErr ++ "\n\n" ++ strWarn
            x <- lift $ optShowImplicit <$> useTC stPragmaOptions
            unless (null s1) $ mapM_ putResponse $
                [ Resp_DisplayInfo $ Info_Error str ] ++
                tellEmacsToJumpToError (getRange e) ++
                [ Resp_HighlightingInfo info KeepHighlighting
                                        method modFile ] ++
                [ Resp_Status $ Status { sChecked = False
                                       , sShowImplicitArguments = x
                                       } ]

    -- | Run an 'IOTCM' value, catch the exceptions, emit output
    --
    --   If an error happens the state of 'CommandM' does not change,
    --   but stPersistent may change (which contains successfully
    --   loaded interfaces for example).

    runInteraction :: IOTCM -> CommandM ()
    runInteraction (IOTCM current highlighting highlightingMethod cmd) =
      handleCommand inEmacs onFail $ do
        current <- liftIO $ absolute current
        -- Raises an error if the given file is not the one currently
        -- loaded.
        cf <- gets theCurrentFile
        when (not (independent cmd) && Just current /= (fst <$> cf)) $
            lift $ typeError $ GenericError "Error: First load the file."

        withCurrentFile $ interpret cmd

        cf <- gets theCurrentFile
        when (updateInteractionPointsAfter cmd
                &&
              Just current == (fst <$> cf)) $
            putResponse . Resp_InteractionPoints =<< gets theInteractionPoints

      where
        inEmacs = liftCommandMT $ withEnv $ initEnv
                { envHighlightingLevel  = highlighting
                , envHighlightingMethod = highlightingMethod
                }

        -- If an independent command fails we should reset theCurrentFile (Issue853).
        onFail | independent cmd = modify $ \ s -> s { theCurrentFile = Nothing }
               | otherwise       = return ()

    ------------------------------------------------------------------------
    -- Command queues

    -- | A generalised command type.

    data Command' a
      = Command !a
        -- ^ A command.
      | Done
        -- ^ Stop processing commands.
      | Error String
        -- ^ An error message for a command that could not be parsed.
      deriving Show

    -- | IOTCM commands.

    type Command = Command' IOTCM

    -- | Command queues.

    data CommandQueue = CommandQueue
      { commands :: !(TChan (Integer, Command))
        -- ^ Commands that should be processed, in the order in which they
        -- should be processed. Each command is associated with a number,
        -- and the numbers are strictly increasing. Abort commands are not
        -- put on this queue.
      , abort :: !(TVar (Maybe Integer))
        -- ^ When this variable is set to @Just n@ an attempt is made to
        -- abort all commands with a command number that is at most @n@.
      }

    -- | If the next command from the command queue is anything but an
    -- actual command, then the command is returned.
    --
    -- If the command is an 'IOTCM' command, then the following happens:
    -- The given computation is applied to the command and executed. If an
    -- abort command is encountered (and acted upon), then the computation
    -- is interrupted, the persistent state and all options are restored,
    -- and some commands are sent to the frontend. If the computation was
    -- not interrupted, then its result is returned.

    -- TODO: It might be nice if some of the changes to the persistent
    -- state inflicted by the interrupted computation were preserved.

    maybeAbort :: (IOTCM -> CommandM a) -> CommandM (Command' (Maybe a))
    maybeAbort m = do
      commandState <- get
      let q = commandQueue commandState
      (n, c) <- liftIO $ atomically $ readTChan (commands q)
      case c of
        Done      -> return Done
        Error e   -> return (Error e)
        Command c -> do
          tcState <- getTC
          tcEnv   <- askTC
          result  <- liftIO $ race
                       (runTCM tcEnv tcState $ runStateT (m c) commandState)
                       (waitForAbort n q)
          case result of
            Left ((x, commandState), tcState) -> do
              putTC tcState
              put commandState
              return (Command (Just x))
            Right a -> do
              liftIO $ popAbortedCommands q a
              putTC $ initState
                { stPersistentState = stPersistentState tcState
                , stPreScopeState   =
                    (stPreScopeState initState)
                      { stPrePragmaOptions =
                          stPrePragmaOptions
                            (stPreScopeState tcState)
                      }
                }
              put $ (initCommandState (commandQueue commandState))
                { optionsOnReload = optionsOnReload commandState
                }
              putResponse Resp_DoneAborting
              displayStatus
              return (Command Nothing)
      where

      -- | Returns if the currently executing command should be aborted.
      -- The "abort number" is returned.

      waitForAbort
        :: Integer
           -- ^ The number of the currently executing command.
        -> CommandQueue
           -- ^ The command queue.
        -> IO Integer
      waitForAbort n q = do
        atomically $ do
          a <- readTVar (abort q)
          case a of
            Just a | n <= a -> return a
            _               -> retry

      -- | Removes every command for which the command number is at most
      -- the given number (the "abort number") from the command queue.
      --
      -- New commands could be added to the end of the queue while this
      -- computation is running. This does not lead to a race condition,
      -- because those commands have higher command numbers, so they will
      -- not be removed.

      popAbortedCommands :: CommandQueue -> Integer -> IO ()
      popAbortedCommands q n = do
        done <- atomically $ do
          c <- tryReadTChan (commands q)
          case c of
            Nothing -> return True
            Just c  ->
              if fst c <= n then
                return False
               else do
                unGetTChan (commands q) c
                return True
        unless done $
          popAbortedCommands q n

    -- | Creates a command queue, and forks a thread that writes commands
    -- to the queue. The queue is returned.

    initialiseCommandQueue
      :: IO Command
         -- ^ Returns the next command.
      -> IO CommandQueue
    initialiseCommandQueue next = do
      commands <- newTChanIO
      abort    <- newTVarIO Nothing

      let -- Read commands. The argument is the number of the previous
          -- command (other than abort commands) that was read, if any.
          readCommands n = do
            c <- next
            case c of
              Command (IOTCM _ _ _ Cmd_abort) -> do
                atomically $ writeTVar abort (Just n)
                readCommands n
              _ -> do
                n <- return (succ n)
                atomically $ writeTChan commands (n, c)
                case c of
                  Done -> return ()
                  _    -> readCommands n

      _ <- forkIO (readCommands 0)

      return (CommandQueue { .. })

    ----------------------------------------------------------------------------
    -- | An interactive computation.

    type Interaction = Interaction' Range

    data Interaction' range
        -- | @cmd_load m argv@ loads the module in file @m@, using
        -- @argv@ as the command-line options.
      = Cmd_load            FilePath [String]

        -- | @cmd_compile b m argv@ compiles the module in file @m@ using
        -- the backend @b@, using @argv@ as the command-line options.
      | Cmd_compile         CompilerBackend FilePath [String]

      | Cmd_constraints

        -- | Show unsolved metas. If there are no unsolved metas but unsolved constraints
        -- show those instead.
      | Cmd_metas

        -- | Shows all the top-level names in the given module, along with
        -- their types. Uses the top-level scope.
      | Cmd_show_module_contents_toplevel
                            B.Rewrite
                            String

        -- | Shows all the top-level names in scope which mention all the given
        -- identifiers in their type.
      | Cmd_search_about_toplevel B.Rewrite String

        -- | Solve (all goals / the goal at point) whose values are determined by
        -- the constraints.
      | Cmd_solveAll B.Rewrite
      | Cmd_solveOne B.Rewrite InteractionId range String

        -- | Solve (all goals / the goal at point) by using Auto.
      | Cmd_autoOne            InteractionId range String
      | Cmd_autoAll

        -- | Parse the given expression (as if it were defined at the
        -- top-level of the current module) and infer its type.
      | Cmd_infer_toplevel  B.Rewrite  -- Normalise the type?
                            String

        -- | Parse and type check the given expression (as if it were defined
        -- at the top-level of the current module) and normalise it.
      | Cmd_compute_toplevel B.ComputeMode
                             String

        ------------------------------------------------------------------------
        -- Syntax highlighting

        -- | @cmd_load_highlighting_info source@ loads syntax highlighting
        -- information for the module in @source@, and asks Emacs to apply
        -- highlighting info from this file.
        --
        -- If the module does not exist, or its module name is malformed or
        -- cannot be determined, or the module has not already been visited,
        -- or the cached info is out of date, then no highlighting information
        -- is printed.
        --
        -- This command is used to load syntax highlighting information when a
        -- new file is opened, and it would probably be annoying if jumping to
        -- the definition of an identifier reset the proof state, so this
        -- command tries not to do that. One result of this is that the
        -- command uses the current include directories, whatever they happen
        -- to be.
      | Cmd_load_highlighting_info FilePath

        -- | Tells Agda to compute token-based highlighting information
        -- for the file.
        --
        -- This command works even if the file's module name does not
        -- match its location in the file system, or if the file is not
        -- scope-correct. Furthermore no file names are put in the
        -- generated output. Thus it is fine to put source code into a
        -- temporary file before calling this command. However, the file
        -- extension should be correct.
        --
        -- If the second argument is 'Remove', then the (presumably
        -- temporary) file is removed after it has been read.
      | Cmd_tokenHighlighting FilePath Remove

        -- | Tells Agda to compute highlighting information for the expression just
        --   spliced into an interaction point.
      | Cmd_highlight InteractionId range String

        ------------------------------------------------------------------------
        -- Implicit arguments

        -- | Tells Agda whether or not to show implicit arguments.
      | ShowImplicitArgs    Bool -- Show them?

        -- | Toggle display of implicit arguments.
      | ToggleImplicitArgs

        ------------------------------------------------------------------------
        -- | Goal commands
        --
        -- If the range is 'noRange', then the string comes from the
        -- minibuffer rather than the goal.

      | Cmd_give            UseForce InteractionId range String

      | Cmd_refine          InteractionId range String

      | Cmd_intro           Bool InteractionId range String

      | Cmd_refine_or_intro Bool InteractionId range String

      | Cmd_context         B.Rewrite InteractionId range String

      | Cmd_helper_function B.Rewrite InteractionId range String

      | Cmd_infer           B.Rewrite InteractionId range String

      | Cmd_goal_type       B.Rewrite InteractionId range String

      -- | Grabs the current goal's type and checks the expression in the hole
      -- against it. Returns the elaborated term.
      | Cmd_elaborate_give
                            B.Rewrite InteractionId range String

        -- | Displays the current goal and context.
      | Cmd_goal_type_context B.Rewrite InteractionId range String

        -- | Displays the current goal and context /and/ infers the type of an
        -- expression.
      | Cmd_goal_type_context_infer
                            B.Rewrite InteractionId range String

      -- | Grabs the current goal's type and checks the expression in the hole
      -- against it.
      | Cmd_goal_type_context_check
                            B.Rewrite InteractionId range String

        -- | Shows all the top-level names in the given module, along with
        -- their types. Uses the scope of the given goal.
      | Cmd_show_module_contents
                            B.Rewrite InteractionId range String

      | Cmd_make_case       InteractionId range String

      | Cmd_compute         B.ComputeMode
                            InteractionId range String

      | Cmd_why_in_scope    InteractionId range String
      | Cmd_why_in_scope_toplevel String
        -- | Displays version of the running Agda
      | Cmd_show_version
      | Cmd_abort
        -- ^ Abort the current computation.
        --
        -- Does nothing if no computation is in progress.
            deriving (Show, Read, Functor, Foldable, Traversable)

    type IOTCM = IOTCM' Range
    data IOTCM' range
        = IOTCM
            FilePath
             -- -^ The current file. If this file does not match
             -- 'theCurrentFile, and the 'Interaction' is not
             -- \"independent\", then an error is raised.
            HighlightingLevel
            HighlightingMethod
            (Interaction' range)
             -- -^ What to do
                deriving (Show, Read, Functor, Foldable, Traversable)

    -- | Used to indicate whether something should be removed or not.

    data Remove
      = Remove
      | Keep
      deriving (Show, Read)

    ---------------------------------------------------------
    -- Read instances

    -- | The 'Parse' monad.
    --   'StateT' state holds the remaining input.

    type Parse a = ExceptT String (StateT String Identity) a

    -- | Converter from the type of 'reads' to 'Parse'
    --   The first paramter is part of the error message
    --   in case the parse fails.

    readsToParse :: String -> (String -> Maybe (a, String)) -> Parse a
    readsToParse s f = do
        st <- lift get
        case f st of
            Nothing -> throwError s
            Just (a, st) -> do
                lift $ put st
                return a

    parseToReadsPrec :: Parse a -> Int -> String -> [(a, String)]
    parseToReadsPrec p i s = case runIdentity . flip runStateT s . runExceptT $ parens' p of
        (Right a, s) -> [(a,s)]
        _ -> []

    -- | Demand an exact string.

    exact :: String -> Parse ()
    exact s = readsToParse (show s) $ fmap (\x -> ((),x)) . List.stripPrefix s . dropWhile (==' ')

    readParse :: Read a => Parse a
    readParse = readsToParse "read failed" $ listToMaybe . reads

    parens' :: Parse a -> Parse a
    parens' p = do
        exact "("
        x <- p
        exact ")"
        return x
      `mplus`
        p

    instance Read InteractionId where
        readsPrec = parseToReadsPrec $
            fmap InteractionId readParse

    -- | Note that the grammar implemented by this instance does not
    -- necessarily match the current representation of ranges.

    instance Read a => Read (Range' a) where
        readsPrec = parseToReadsPrec $
          (exact "intervalsToRange" >>
           liftM2 intervalsToRange readParse readParse)
            `mplus`
          (exact "noRange" >> return noRange)

    instance Read a => Read (Interval' a) where
        readsPrec = parseToReadsPrec $ do
            exact "Interval"
            liftM2 Interval readParse readParse

    instance Read AbsolutePath where
        readsPrec = parseToReadsPrec $ do
            exact "mkAbsolute"
            fmap mkAbsolute readParse

    instance Read a => Read (Position' a) where
        readsPrec = parseToReadsPrec $ do
            exact "Pn"
            liftM4 Pn readParse readParse readParse readParse

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

    -- | Can the command run even if the relevant file has not been loaded
    --   into the state?

    independent :: Interaction -> Bool
    independent (Cmd_load {})                   = True
    independent (Cmd_compile {})                = True
    independent (Cmd_load_highlighting_info {}) = True
    independent Cmd_tokenHighlighting {}        = True
    independent Cmd_show_version                = True
    independent _                               = False

    -- | Should 'Resp_InteractionPoints' be issued after the command has
    -- run?

    updateInteractionPointsAfter :: Interaction -> Bool
    updateInteractionPointsAfter Cmd_load{}                          = True
    updateInteractionPointsAfter Cmd_compile{}                       = True
    updateInteractionPointsAfter Cmd_constraints{}                   = False
    updateInteractionPointsAfter Cmd_metas{}                         = False
    updateInteractionPointsAfter Cmd_show_module_contents_toplevel{} = False
    updateInteractionPointsAfter Cmd_search_about_toplevel{}         = False
    updateInteractionPointsAfter Cmd_solveAll{}                      = True
    updateInteractionPointsAfter Cmd_solveOne{}                      = True
    updateInteractionPointsAfter Cmd_infer_toplevel{}                = False
    updateInteractionPointsAfter Cmd_compute_toplevel{}              = False
    updateInteractionPointsAfter Cmd_load_highlighting_info{}        = False
    updateInteractionPointsAfter Cmd_tokenHighlighting{}             = False
    updateInteractionPointsAfter Cmd_highlight{}                     = True
    updateInteractionPointsAfter ShowImplicitArgs{}                  = False
    updateInteractionPointsAfter ToggleImplicitArgs{}                = False
    updateInteractionPointsAfter Cmd_give{}                          = True
    updateInteractionPointsAfter Cmd_refine{}                        = True
    updateInteractionPointsAfter Cmd_intro{}                         = True
    updateInteractionPointsAfter Cmd_refine_or_intro{}               = True
    updateInteractionPointsAfter Cmd_autoOne{}                       = True
    updateInteractionPointsAfter Cmd_autoAll{}                       = True
    updateInteractionPointsAfter Cmd_context{}                       = False
    updateInteractionPointsAfter Cmd_helper_function{}               = False
    updateInteractionPointsAfter Cmd_infer{}                         = False
    updateInteractionPointsAfter Cmd_goal_type{}                     = False
    updateInteractionPointsAfter Cmd_elaborate_give{}                = True
    updateInteractionPointsAfter Cmd_goal_type_context{}             = False
    updateInteractionPointsAfter Cmd_goal_type_context_infer{}       = False
    updateInteractionPointsAfter Cmd_goal_type_context_check{}       = False
    updateInteractionPointsAfter Cmd_show_module_contents{}          = False
    updateInteractionPointsAfter Cmd_make_case{}                     = True
    updateInteractionPointsAfter Cmd_compute{}                       = False
    updateInteractionPointsAfter Cmd_why_in_scope{}                  = False
    updateInteractionPointsAfter Cmd_why_in_scope_toplevel{}         = False
    updateInteractionPointsAfter Cmd_show_version{}                  = False
    updateInteractionPointsAfter Cmd_abort{}                         = False

    -- | Interpret an interaction

    interpret :: Interaction -> CommandM ()

    interpret (Cmd_load m argv) =
      cmd_load' m argv True Imp.TypeCheck $ \_ -> interpret Cmd_metas

    interpret (Cmd_compile b file argv) =
      cmd_load' file argv (b `elem` [LaTeX, QuickLaTeX])
                (if b == QuickLaTeX
                 then Imp.ScopeCheck
                 else Imp.TypeCheck) $ \(i, mw) -> do
        mw <- lift $ Imp.applyFlagsToMaybeWarnings mw
        case mw of
          Imp.NoWarnings -> do
            lift $ case b of
              LaTeX                    -> LaTeX.generateLaTeX i
              QuickLaTeX               -> LaTeX.generateLaTeX i
              OtherBackend "GHCNoMain" -> callBackend "GHC" NotMain i   -- for backwards compatibility
              OtherBackend b           -> callBackend b IsMain  i
            (pwe, pwa) <- interpretWarnings
            display_info $ Info_CompilationOk pwa pwe
          Imp.SomeWarnings w -> do
            pw <- lift $ prettyTCWarnings w
            display_info $ Info_Error $ unlines
              [ "You need to fix the following errors before you can compile"
              , "the module:"
              , ""
              , pw
              ]

    interpret Cmd_constraints =
        display_info . Info_Constraints . show . vcat . map pretty =<< lift B.getConstraints

    interpret Cmd_metas = do -- CL.showMetas []
      unsolvedNotOK <- lift $ not . optAllowUnsolved <$> pragmaOptions
      ms <- lift showOpenMetas
      (pwe, pwa) <- interpretWarnings
      display_info $ Info_AllGoalsWarnings (unlines ms) pwa pwe

    interpret (Cmd_show_module_contents_toplevel norm s) =
      liftCommandMT B.atTopLevel $ showModuleContents norm noRange s

    interpret (Cmd_search_about_toplevel norm s) =
      liftCommandMT B.atTopLevel $ searchAbout norm noRange s

    interpret (Cmd_solveAll norm)        = solveInstantiatedGoals norm Nothing
    interpret (Cmd_solveOne norm ii _ _) = solveInstantiatedGoals norm' (Just ii)
      -- `solveOne` is called via `agda2-maybe-normalised` which does not use
      -- AsIs < Simplified < Normalised but rather Simplified < Instantiated < Normalised
      -- So we remap the Rewrite modifiers to match solveAll's behaviour.
      -- NB: instantiate is called in getSolvedInteractionPoints no matter what.
      where norm' = case norm of
                      Simplified   -> AsIs
                      Instantiated -> Simplified
                      _            -> norm

    interpret (Cmd_infer_toplevel norm s) =
      parseAndDoAtToplevel (prettyA <=< B.typeInCurrent norm) Info_InferredType s

    interpret (Cmd_compute_toplevel cmode s) =
      parseAndDoAtToplevel action Info_NormalForm $ computeWrapInput cmode s
      where
      action = allowNonTerminatingReductions
             . (if computeIgnoreAbstract cmode then ignoreAbstractMode else inConcreteMode)
             . (B.showComputed cmode <=< B.evalInCurrent)

    interpret (ShowImplicitArgs showImpl) = do
      opts <- lift commandLineOptions
      setCommandLineOpts $
        opts { optPragmaOptions =
                 (optPragmaOptions opts) { optShowImplicit = showImpl } }

    interpret ToggleImplicitArgs = do
      opts <- lift commandLineOptions
      let ps = optPragmaOptions opts
      setCommandLineOpts $
        opts { optPragmaOptions =
                 ps { optShowImplicit = not $ optShowImplicit ps } }

    interpret (Cmd_load_highlighting_info source) = do
      l <- asksTC envHighlightingLevel
      when (l /= None) $ do
        -- Make sure that the include directories have
        -- been set.
        setCommandLineOpts =<< lift commandLineOptions

        resp <- lift $ liftIO . tellToUpdateHighlighting =<< do
          ex <- liftIO $ doesFileExist source
          absSource <- liftIO $ absolute source
          case ex of
            False -> return Nothing
            True  -> (do
              si <- Imp.sourceInfo absSource
              let m = Imp.siModuleName si
              checkModuleName m absSource Nothing
              mmi <- getVisitedModule m
              case mmi of
                Nothing -> return Nothing
                Just mi ->
                  if hashText (Imp.siSource si) ==
                     iSourceHash (miInterface mi)
                   then do
                    modFile <- useTC stModuleToSource
                    method  <- viewTC eHighlightingMethod
                    return $ Just (iHighlighting $ miInterface mi, method, modFile)
                   else
                    return Nothing)
                `catchError`
              \_ -> return Nothing
        mapM_ putResponse resp

    interpret (Cmd_tokenHighlighting source remove) = do
      info <- do l <- asksTC envHighlightingLevel
                 if l == None
                   then return Nothing
                   else do
                     source <- liftIO (absolute source)
                     lift $ (Just <$> generateTokenInfo source)
                               `catchError` \_ ->
                            return Nothing
          `finally`
        case remove of
          Remove -> liftIO $ removeFile source
          Keep   -> return ()
      case info of
        Just info -> lift $ printHighlightingInfo RemoveHighlighting info
        Nothing   -> return ()

    interpret (Cmd_highlight ii rng s) = do
      l <- asksTC envHighlightingLevel
      when (l /= None) $ do
        scope <- getOldInteractionScope ii
        removeOldInteractionScope ii
        handle $ do
          e <- try ("Highlighting failed to parse expression in " ++ show ii) $
                 B.parseExpr rng s
          e <- try ("Highlighting failed to scope check expression in " ++ show ii) $
                 concreteToAbstract scope e
          lift $ printHighlightingInfo KeepHighlighting =<<
                   generateTokenInfoFromString rng s
          lift $ highlightExpr e
      where
        handle :: ExceptT String TCM () -> CommandM ()
        handle m = do
          res <- lift $ runExceptT m
          case res of
            Left s  -> display_info $ Info_Error s
            Right _ -> return ()
        try :: String -> TCM a -> ExceptT String TCM a
        try err m = mkExceptT $ do
          (mapLeft (const err) <$> freshTCM m) `catchError` \ _ -> return (Left err)
          -- freshTCM to avoid scope checking creating new interaction points

    interpret (Cmd_give   force ii rng s) = give_gen force ii rng s Give
    interpret (Cmd_refine ii rng s) = give_gen WithoutForce ii rng s Refine

    interpret (Cmd_intro pmLambda ii rng _) = do
      ss <- lift $ B.introTactic pmLambda ii
      liftCommandMT (B.withInteractionId ii) $ case ss of
        []    -> do
          display_info $ Info_Intro $ "No introduction forms found."
        [s]   -> give_gen WithoutForce ii rng s Intro
        _:_:_ -> do
          display_info $ Info_Intro $
            sep [ "Don't know which constructor to introduce of"
                , let mkOr []     = []
                      mkOr [x, y] = [text x <+> "or" <+> text y]
                      mkOr (x:xs) = text x : mkOr xs
                  in nest 2 $ fsep $ punctuate comma (mkOr ss)
                ]

    interpret (Cmd_refine_or_intro pmLambda ii r s) = interpret $
      let s' = trim s
      in (if null s' then Cmd_intro pmLambda else Cmd_refine) ii r s'

    interpret (Cmd_autoOne ii rng s) = do
      -- Andreas, 2014-07-05 Issue 1226:
      -- Save the state to have access to even those interaction ids
      -- that Auto solves (since Auto gives the solution right away).
      st <- getTC
      (time , res) <- maybeTimed $ Auto.auto ii rng s
      case autoProgress res of
       Solutions sols -> do
        lift $ reportSLn "auto" 10 $ "Auto produced the following solutions " ++ show sols
        forM_ sols $ \(ii, s) -> do
          -- Andreas, 2014-07-05 Issue 1226:
          -- For highlighting, Resp_GiveAction needs to access
          -- the @oldInteractionScope@s of the interaction points solved by Auto.
          -- We dig them out from the state before Auto was invoked.
          insertOldInteractionScope ii =<< liftLocalState (putTC st >> getInteractionScope ii)
          -- Andreas, 2014-07-07: NOT TRUE:
          -- -- Andreas, 2014-07-05: The following should be obsolete,
          -- -- as Auto has removed the interaction points already:
          -- modifyTheInteractionPoints $ filter (/= ii)
          putResponse $ Resp_GiveAction ii $ Give_String s
        -- Andreas, 2014-07-07: Remove the interaction points in one go.
        modifyTheInteractionPoints (List.\\ (map fst sols))
        case autoMessage res of
         Nothing  -> interpret Cmd_metas
         Just msg -> display_info $ Info_Auto msg
       FunClauses cs -> do
        case autoMessage res of
         Nothing  -> return ()
         Just msg -> display_info $ Info_Auto msg
        putResponse $ Resp_MakeCase R.Function cs
       Refinement s -> give_gen WithoutForce ii rng s Refine
      maybe (return ()) (display_info . Info_Time) time

    interpret Cmd_autoAll = do
      iis <- getInteractionPoints
      unless (null iis) $ do
        let time = 1000 `div` length iis
        st <- getTC
        solved <- forM iis $ \ ii -> do
          rng <- getInteractionRange ii
          res <- Auto.auto ii rng ("-t " ++ show time ++ "ms")
          case autoProgress res of
            Solutions sols -> forM sols $ \ (jj, s) -> do
                oldInteractionScope <- liftLocalState (putTC st >> getInteractionScope jj)
                insertOldInteractionScope jj oldInteractionScope
                putResponse $ Resp_GiveAction ii $ Give_String s
                return jj
            _ -> return []
        modifyTheInteractionPoints (List.\\ concat solved)

    interpret (Cmd_context norm ii _ _) =
      display_info . Info_Context =<< liftLocalState (prettyContext norm False ii)

    interpret (Cmd_helper_function norm ii rng s) =
      display_info . Info_HelperFunction =<< liftLocalState (cmd_helper_function norm ii rng s)

    interpret (Cmd_infer norm ii rng s) =
      display_info . Info_InferredType
        =<< liftLocalState (B.withInteractionId ii
              (prettyATop =<< B.typeInMeta ii norm =<< B.parseExprIn ii rng s))

    interpret (Cmd_goal_type norm ii _ _) =
      display_info . Info_CurrentGoal
        =<< liftLocalState (B.withInteractionId ii $ prettyTypeOfMeta norm ii)

    interpret (Cmd_elaborate_give norm ii rng s) = do
      have <- liftLocalState $ B.withInteractionId ii $ do
        expr <- B.parseExprIn ii rng s
        goal <- B.typeOfMeta AsIs ii
        term <- case goal of
          OfType _ ty -> checkExpr expr =<< isType_ ty
          _           -> __IMPOSSIBLE__
        nf <- normalForm norm term
        txt <- localTC (\ e -> e { envPrintMetasBare = True }) (TCP.prettyTCM nf)
        return $ show txt
      give_gen WithoutForce ii rng have ElaborateGive

    interpret (Cmd_goal_type_context norm ii rng s) =
      cmd_goal_type_context_and empty norm ii rng s

    interpret (Cmd_goal_type_context_infer norm ii rng s) = do
      -- In case of the empty expression to type, don't fail with
      -- a stupid parse error, but just fall back to
      -- Cmd_goal_type_context.
      have <- if all Char.isSpace s then return empty else liftLocalState $ do
        typ <- B.withInteractionId ii $
          prettyATop =<< B.typeInMeta ii norm =<< B.parseExprIn ii rng s
        return $ "Have:" <+> typ
      cmd_goal_type_context_and have norm ii rng s

    interpret (Cmd_goal_type_context_check norm ii rng s) = do
      have <- liftLocalState $ B.withInteractionId ii $ do
        expr <- B.parseExprIn ii rng s
        goal <- B.typeOfMeta AsIs ii
        term <- case goal of
          OfType _ ty -> checkExpr expr =<< isType_ ty
          _           -> __IMPOSSIBLE__
        txt <- TCP.prettyTCM =<< normalForm norm term
        return $ "Elaborates to:" <+> txt
      cmd_goal_type_context_and have norm ii rng s

    interpret (Cmd_show_module_contents norm ii rng s) =
      liftCommandMT (B.withInteractionId ii) $ showModuleContents norm rng s

    interpret (Cmd_why_in_scope_toplevel s) =
      liftCommandMT B.atTopLevel $ whyInScope s

    interpret (Cmd_why_in_scope ii rng s) =
      liftCommandMT (B.withInteractionId ii) $ whyInScope s

    interpret (Cmd_make_case ii rng s) = do
      (f, casectxt, cs) <- lift $ makeCase ii rng s
      liftCommandMT (B.withInteractionId ii) $ do
        hidden <- lift $ showImplicitArguments
        tel <- lift $ lookupSection (qnameModule f) -- don't shadow the names in this telescope
        unicode <- getsTC $ optUseUnicode . getPragmaOptions
        pcs      :: [Doc]      <- lift $ inTopContext $ addContext tel $ mapM prettyA cs
        let pcs' :: [String]    = List.map (extlam_dropName unicode casectxt . render) pcs
        lift $ reportSDoc "interaction.case" 60 $ TCP.vcat
          [ "InteractionTop.Cmd_make_case"
          , TCP.nest 2 $ TCP.vcat
            [ "cs   = " TCP.<+> TCP.vcat (map prettyA cs)
            , "pcs  = " TCP.<+> TCP.vcat (map return pcs)
            , "pcs' = " TCP.<+> TCP.vcat (map TCP.text pcs')
            ]
          ]
        lift $ reportSDoc "interaction.case" 90 $ TCP.vcat
          [ "InteractionTop.Cmd_make_case"
          , TCP.nest 2 $ TCP.vcat
            [ "cs   = " TCP.<+> TCP.text (show cs)
            ]
          ]
        putResponse $ Resp_MakeCase (makeCaseVariant casectxt) pcs'
      where
        render = renderStyle (style { mode = OneLineMode })

        makeCaseVariant :: CaseContext -> MakeCaseVariant
        makeCaseVariant Nothing = R.Function
        makeCaseVariant Just{}  = R.ExtendedLambda

        -- very dirty hack, string manipulation by dropping the function name
        -- and replacing the last " = " with " -> ". It's important not to replace
        -- the equal sign in named implicit with an arrow!
        extlam_dropName :: Bool -> CaseContext -> String -> String
        extlam_dropName _ Nothing x = x
        extlam_dropName unicode Just{}  x
            = unwords $ reverse $ replEquals $ reverse $ drop 1 $ words x
          where
            replEquals ("=" : ws)
               | unicode   = "→" : ws
               | otherwise = "->" : ws
            replEquals (w   : ws) = w : replEquals ws
            replEquals []         = []

    interpret (Cmd_compute cmode ii rng s) = display_info . Info_NormalForm =<< do
      liftLocalState $ do
        e <- B.parseExprIn ii rng $ computeWrapInput cmode s
        B.withInteractionId ii $ do
          showComputed cmode =<< do applyWhen (computeIgnoreAbstract cmode) ignoreAbstractMode $ B.evalInCurrent e

    interpret Cmd_show_version = display_info Info_Version

    interpret Cmd_abort = return ()

    -- | Show warnings
    interpretWarnings :: CommandM (String, String)
    interpretWarnings = do
      mws <- lift $ Imp.getMaybeWarnings AllWarnings
      case filter isNotMeta <$> mws of
        Imp.SomeWarnings ws@(_:_) -> do
          let (we, wa) = classifyWarnings ws
          pwe <- lift $ prettyTCWarnings we
          pwa <- lift $ prettyTCWarnings wa
          return (pwe, pwa)
        _ -> return ("", "")
       where isNotMeta w = case tcWarning w of
                             UnsolvedInteractionMetas{} -> False
                             UnsolvedMetaVariables{}    -> False
                             _                          -> True

    -- | Solved goals already instantiated internally
    -- The second argument potentially limits it to one specific goal.
    solveInstantiatedGoals :: B.Rewrite -> Maybe InteractionId -> CommandM ()
    solveInstantiatedGoals norm mii = do
      -- Andreas, 2016-10-23 issue #2280: throw away meta elims.
      out <- lift $ localTC (\ e -> e { envPrintMetasBare = True }) $ do
        sip <- B.getSolvedInteractionPoints False norm
               -- only solve metas which have a proper instantiation, i.e., not another meta
        let sip' = maybe id (\ ii -> filter ((ii ==) . fst3)) mii sip
        mapM prt sip'
      putResponse $ Resp_SolveAll out
      where
          prt (i, m, e) = do
            mi <- getMetaInfo <$> lookupMeta m
            e <- withMetaInfo mi $ abstractToConcreteCtx TopCtx e
            return (i, e)

    -- | Print open metas nicely.
    showOpenMetas :: TCM [String]
    showOpenMetas = do
      ims <- B.typesOfVisibleMetas B.AsIs
      di <- forM ims $ \ i ->
        B.withInteractionId (B.outputFormId $ B.OutputForm noRange [] i) $
          prettyATop i
      -- Show unsolved implicit arguments simplified.
      unsolvedNotOK <- not . optAllowUnsolved <$> pragmaOptions
      hms <- (guard unsolvedNotOK >>) <$> B.typesOfHiddenMetas B.Simplified
      dh <- mapM showA' hms
      return $ map show di ++ dh
      where
        metaId (B.OfType i _) = i
        metaId (B.JustType i) = i
        metaId (B.JustSort i) = i
        metaId (B.Assign i e) = i
        metaId _ = __IMPOSSIBLE__
        showA' :: B.OutputConstraint A.Expr NamedMeta -> TCM String
        showA' m = do
          let i = nmid $ metaId m
          r <- getMetaRange i
          d <- B.withMetaId i (prettyATop m)
          return $ show d ++ "  [ at " ++ show r ++ " ]"

    -- | @cmd_load' file argv unsolvedOk cmd@
    --   loads the module in file @file@,
    --   using @argv@ as the command-line options.
    --
    -- If type checking completes without any exceptions having been
    -- encountered then the command @cmd r@ is executed, where @r@ is the
    -- result of 'Imp.typeCheckMain'.

    cmd_load' :: FilePath -> [String]
              -> Bool      -- ^ Allow unsolved meta-variables?
              -> Imp.Mode  -- ^ Full type-checking, or only
                           --   scope-checking?
              -> ((Interface, Imp.MaybeWarnings) -> CommandM ())
              -> CommandM ()
    cmd_load' file argv unsolvedOK mode cmd = do
        f <- liftIO $ absolute file
        ex <- liftIO $ doesFileExist $ filePath f
        unless ex $ typeError $ GenericError $
          "The file " ++ file ++ " was not found."

        -- Forget the previous "current file" and interaction points.
        modify $ \ st -> st { theInteractionPoints = []
                            , theCurrentFile       = Nothing
                            }

        t <- liftIO $ getModificationTime file

        -- Parse the file.
        si <- lift (Imp.sourceInfo f)

        -- All options are reset when a file is reloaded, including the
        -- choice of whether or not to display implicit arguments.
        opts0 <- gets optionsOnReload
        backends <- useTC stBackends
        z <- liftIO $ runOptM $ parseBackendOptions backends argv opts0
        case z of
          Left err   -> lift $ typeError $ GenericError err
          Right (_, opts) -> do
            let update o = o { optAllowUnsolved = unsolvedOK && optAllowUnsolved o}
                root     = projectRoot f (Imp.siModuleName si)
            lift $ TM.setCommandLineOptions' root $ mapPragmaOptions update opts
            displayStatus

        -- Reset the state, preserving options and decoded modules. Note
        -- that if the include directories have changed, then the decoded
        -- modules are reset when cmd_load' is run by ioTCM.
        lift resetState

        -- Clear the info buffer to make room for information about which
        -- module is currently being type-checked.
        putResponse Resp_ClearRunningInfo

        -- Remove any prior syntax highlighting.
        putResponse (Resp_ClearHighlighting NotOnlyTokenBased)

        ok <- lift $ Imp.typeCheckMain f mode si

        -- The module type checked. If the file was not changed while the
        -- type checker was running then the interaction points and the
        -- "current file" are stored.
        t' <- liftIO $ getModificationTime file
        when (t == t') $ do
          is <- lift $ sortInteractionPoints =<< getInteractionPoints
          modify $ \st -> st { theInteractionPoints = is
                             , theCurrentFile       = Just (f, t)
                             }

        cmd ok

    -- | Set 'envCurrentPath' to 'theCurrentFile', if any.
    withCurrentFile :: CommandM a -> CommandM a
    withCurrentFile m = do
      mfile <- fmap fst <$> gets theCurrentFile
      localTC (\ e -> e { envCurrentPath = mfile }) m

    -- | Available backends.

    data CompilerBackend = LaTeX | QuickLaTeX | OtherBackend String
        deriving (Eq)

    instance Show CompilerBackend where
      show LaTeX            = "LaTeX"
      show QuickLaTeX       = "QuickLaTeX"
      show (OtherBackend s) = s

    instance Read CompilerBackend where
      readsPrec _ s = do
        (t, s) <- lex s
        let b = case t of
                  "LaTeX"      -> LaTeX
                  "QuickLaTeX" -> QuickLaTeX
                  _            -> OtherBackend t
        return (b, s)

    data GiveRefine = Give | Refine | Intro | ElaborateGive
      deriving (Eq, Show)

    -- | A "give"-like action (give, refine, etc).
    --
    --   @give_gen force ii rng s give_ref mk_newtxt@
    --   acts on interaction point @ii@
    --   occupying range @rng@,
    --   placing the new content given by string @s@,
    --   and replacing @ii@ by the newly created interaction points
    --   in the state if safety checks pass (unless @force@ is applied).
    give_gen
      :: UseForce       -- ^ Should safety checks be skipped?
      -> InteractionId
      -> Range
      -> String
      -> GiveRefine
      -> CommandM ()
    give_gen force ii rng s0 giveRefine = do
      let s = trim s0
      lift $ reportSLn "interaction.give" 20 $ "give_gen  " ++ s
      -- Andreas, 2015-02-26 if string is empty do nothing rather
      -- than giving a parse error.
      unless (null s) $ do
        let give_ref =
              case giveRefine of
                Give          -> B.give
                Refine        -> B.refine
                Intro         -> B.refine
                ElaborateGive -> B.give
        -- save scope of the interaction point (for printing the given expr. later)
        scope     <- lift $ getInteractionScope ii
        -- parse string and "give", obtaining an abstract expression
        -- and newly created interaction points
        (time, (ae, ae0, iis)) <- maybeTimed $ lift $ do
            mis  <- getInteractionPoints
            reportSLn "interaction.give" 30 $ "interaction points before = " ++ show mis
            given <- B.parseExprIn ii rng s
            ae    <- give_ref force ii Nothing given
            mis' <- getInteractionPoints
            reportSLn "interaction.give" 30 $ "interaction points after = " ++ show mis'
            return (ae, given, mis' List.\\ mis)
        -- favonia: backup the old scope for highlighting
        insertOldInteractionScope ii scope
        -- sort the new interaction points and put them into the state
        -- in replacement of the old interaction point
        iis       <- lift $ sortInteractionPoints iis
        modifyTheInteractionPoints $ replace ii iis
        -- print abstract expr
        ce        <- lift $ abstractToConcreteScope scope ae
        lift $ reportSLn "interaction.give" 30 $ unlines
          [ "ce = " ++ show ce
          , "scopePrecedence = " ++ show (scopePrecedence scope)
          ]
        -- if the command was @Give@, use the literal user input;
        -- Andreas, 2014-01-15, see issue 1020:
        -- Refine could solve a goal by introducing the sole constructor
        -- without arguments.  Then there are no interaction metas, but
        -- we still cannot just `give' the user string (which may be empty).
        -- WRONG: also, if no interaction metas were created by @Refine@
        -- WRONG: let literally = (giveRefine == Give || null iis) && rng /= noRange
        -- Ulf, 2015-03-30, if we're doing intro we can't do literal give since
        -- there is nothing in the hole (issue 1892).
        let literally = giveRefine /= Intro && giveRefine /= ElaborateGive && ae == ae0 && rng /= noRange
        -- Ulf, 2014-01-24: This works for give since we're highlighting the string
        -- that's already in the buffer. Doing it before the give action means that
        -- the highlighting is moved together with the text when the hole goes away.
        -- To make it work for refine we'd have to adjust the ranges.
        when literally $ lift $ do
          l <- asksTC envHighlightingLevel
          when (l /= None) $ do
            printHighlightingInfo KeepHighlighting =<<
              generateTokenInfoFromString rng s
            highlightExpr ae
        putResponse $ Resp_GiveAction ii $ mkNewTxt literally ce
        lift $ reportSLn "interaction.give" 30 $ "putResponse GiveAction passed"
        -- display new goal set (if not measuring time)
        maybe (interpret Cmd_metas) (display_info . Info_Time) time
        lift $ reportSLn "interaction.give" 30 $ "interpret Cmd_metas passed"
      where
        -- Substitutes xs for x in ys.
        replace x xs ys = concatMap (\ y -> if y == x then xs else [y]) ys
        -- For @Give@ we can replace the ii by the user given input.
        mkNewTxt True  C.Paren{} = Give_Paren
        mkNewTxt True  _         = Give_NoParen
        -- Otherwise, we replace it by the reified value Agda computed.
        mkNewTxt False ce        = Give_String $ prettyShow ce

    highlightExpr :: A.Expr -> TCM ()
    highlightExpr e =
      localTC (\e -> e { envModuleNestingLevel = 0
                     , envHighlightingLevel  = NonInteractive
                     , envHighlightingMethod = Direct }) $
        generateAndPrintSyntaxInfo decl Full True
      where
        dummy = mkName_ (NameId 0 0) ("dummy" :: String)
        info  = mkDefInfo (nameConcrete dummy) noFixity' PublicAccess ConcreteDef (getRange e)
        decl  = A.Axiom NoFunSig info defaultArgInfo Nothing (qnameFromList [dummy]) e

    -- | Sorts interaction points based on their ranges.

    sortInteractionPoints :: [InteractionId] -> TCM [InteractionId]
    sortInteractionPoints is =
      map fst . List.sortBy (compare `on` snd) <$> do
        forM is $ \ i -> do
          (i,) <$> getInteractionRange i

    -- | Pretty-prints the type of the meta-variable.

    prettyTypeOfMeta :: B.Rewrite -> InteractionId -> TCM Doc
    prettyTypeOfMeta norm ii = do
      form <- B.typeOfMeta norm ii
      case form of
        B.OfType _ e -> prettyATop e
        _            -> prettyATop form

    -- | Pretty-prints the context of the given meta-variable.

    prettyContext
      :: B.Rewrite      -- ^ Normalise?
      -> Bool           -- ^ Print the elements in reverse order?
      -> InteractionId
      -> TCM Doc
    prettyContext norm rev ii = B.withInteractionId ii $ do
      ctx <- filter (not . shouldHide) <$> B.contextOfMeta ii norm
      es  <- mapM (prettyATop . B.ofExpr) ctx
      xs  <- mapM (abstractToConcrete_ . B.ofName) ctx
      let ns = map (nameConcrete . B.ofName) ctx
          ss = map C.isInScope xs
      return $ align 10 $ applyWhen rev reverse $
          zip (zipWith prettyCtxName ns xs)
              (zipWith prettyCtxType es ss)
      where
        shouldHide (OfType' n e) = isNoName n || nameIsRecordName n
        prettyCtxName :: C.Name -> C.Name -> String
        prettyCtxName n x
          | n == x                 = prettyShow x
          | isInScope n == InScope = prettyShow n ++ " = " ++ prettyShow x
          | otherwise              = prettyShow x
        prettyCtxType e nis = ":" <+> (e P.<> notInScopeMarker nis)
        notInScopeMarker nis = case isInScope nis of
          C.InScope    -> ""
          C.NotInScope -> "  (not in scope)"

    -- | Create type of application of new helper function that would solve the goal.

    cmd_helper_function :: B.Rewrite -> InteractionId -> Range -> String -> TCM Doc
    cmd_helper_function norm ii r s = B.withInteractionId ii $ inTopContext $
      prettyATop =<< B.metaHelperType norm ii r s

    -- | Displays the current goal, the given document, and the current
    --   context.
    --
    --   Should not modify the state.

    cmd_goal_type_context_and :: Doc -> B.Rewrite -> InteractionId -> Range ->
                                 String -> StateT CommandState (TCMT IO) ()
    cmd_goal_type_context_and doc norm ii _ _ = display_info . Info_GoalType =<< do
      lift $ do
        goal <- B.withInteractionId ii $ prettyTypeOfMeta norm ii
        ctx  <- prettyContext norm True ii
        m    <- lookupInteractionId ii
        constr <- vcat . map pretty <$> B.getConstraints' (mentionsMeta m)
        let constrDoc = ifNull constr [] $ \constr ->
              [ text $ delimiter "Constraints"
              , constr
              ]
        return $ vcat $
          [ "Goal:" <+> goal
          , doc
          , text (replicate 60 '\x2014')
          , ctx
          ] ++ constrDoc

    -- | Shows all the top-level names in the given module, along with
    -- their types.

    showModuleContents :: B.Rewrite -> Range -> String -> CommandM ()
    showModuleContents norm rng s = display_info . Info_ModuleContents =<< do
      liftLocalState $ do
        (modules, tel, types) <- B.moduleContents norm rng s
        types' <- addContext tel $ forM types $ \ (x, t) -> do
          t <- TCP.prettyTCM t
          return (prettyShow x, ":" <+> t)
        return $ vcat
          [ "Modules"
          , nest 2 $ vcat $ map pretty modules
          , "Names"
          , nest 2 $ align 10 types'
          ]

    -- | Shows all the top-level names in scope which mention all the given
    -- identifiers in their type.

    searchAbout :: B.Rewrite -> Range -> String -> CommandM ()
    searchAbout norm rg nm = do
      let tnm = trim nm
      unless (null tnm) $ do
        fancy <- lift $ B.atTopLevel $ do
           hits <- findMentions norm rg tnm
           forM hits $ \ (x, t) -> do
             t <- TCP.prettyTCM t
             return (prettyShow x, ":" <+> t)
        display_info $ Info_SearchAbout $
          "Definitions about" <+> text (List.intercalate ", " $ words nm) $$
          nest 2 (align 10 fancy)

    -- | Explain why something is in scope.

    whyInScope :: String -> CommandM ()
    whyInScope s = display_info . Info_WhyInScope =<< do
      Just (file, _) <- gets theCurrentFile
      let cwd = takeDirectory $ filePath file
      liftLocalState $ do
        (v, xs, ms) <- B.whyInScope s
        explanation cwd v xs ms
      where
        explanation _ Nothing [] [] = TCP.text (s ++ " is not in scope.")
        explanation cwd v xs ms = TCP.vcat
          [ TCP.text (s ++ " is in scope as")
          , TCP.nest 2 $ TCP.vcat [variable v xs, modules ms]
          ]
          where
            prettyRange :: Range -> TCM Doc
            prettyRange r = pretty . (fmap . fmap) mkRel <$> do
              return r
            mkRel = makeRelative cwd . filePath

            -- variable :: Maybe _ -> [_] -> TCM Doc
            variable Nothing xs = names xs
            variable (Just x) xs
              | null xs   = asVar
              | otherwise = TCP.vcat
                 [ TCP.sep [ asVar, TCP.nest 2 $ shadowing x]
                 , TCP.nest 2 $ names xs
                 ]
              where
                asVar :: TCM Doc
                asVar = do
                  "* a variable bound at" TCP.<+> TCP.prettyTCM (nameBindingSite $ localVar x)
                shadowing :: LocalVar -> TCM Doc
                shadowing (LocalVar _ _ [])    = "shadowing"
                shadowing _ = "in conflict with"
            names   xs = TCP.vcat $ map pName xs
            modules ms = TCP.vcat $ map pMod ms

            pKind DefName        = "defined name"
            pKind ConName        = "constructor"
            pKind FldName        = "record field"
            pKind PatternSynName = "pattern synonym"
            pKind GeneralizeName = "generalizable variable"
            pKind DisallowedGeneralizeName = "generalizable variable from let open"
            pKind MacroName      = "macro name"
            pKind QuotableName   = "quotable name"

            pName :: AbstractName -> TCM Doc
            pName a = TCP.sep
              [ "* a"
                TCP.<+> pKind (anameKind a)
                TCP.<+> TCP.text (prettyShow $ anameName a)
              , TCP.nest 2 $ "brought into scope by"
              ] TCP.$$
              TCP.nest 2 (pWhy (nameBindingSite $ qnameName $ anameName a) (anameLineage a))
            pMod :: AbstractModule -> TCM Doc
            pMod  a = TCP.sep
              [ "* a module" TCP.<+> TCP.text (prettyShow $ amodName a)
              , TCP.nest 2 $ "brought into scope by"
              ] TCP.$$
              TCP.nest 2 (pWhy (nameBindingSite $ qnameName $ mnameToQName $ amodName a) (amodLineage a))

            pWhy :: Range -> WhyInScope -> TCM Doc
            pWhy r Defined = "- its definition at" TCP.<+> TCP.prettyTCM r
            pWhy r (Opened (C.QName x) w) | isNoName x = pWhy r w
            pWhy r (Opened m w) =
              "- the opening of"
              TCP.<+> TCP.prettyTCM m
              TCP.<+> "at"
              TCP.<+> TCP.prettyTCM (getRange m)
              TCP.$$
              pWhy r w
            pWhy r (Applied m w) =
              "- the application of"
              TCP.<+> TCP.prettyTCM m
              TCP.<+> "at"
              TCP.<+> TCP.prettyTCM (getRange m)
              TCP.$$
              pWhy r w

    -- | Sets the command line options and updates the status information.

    setCommandLineOpts :: CommandLineOptions -> CommandM ()
    setCommandLineOpts opts = do
        lift $ TM.setCommandLineOptions opts
        displayStatus

    -- | Computes some status information.
    --
    --   Does not change the state.

    status :: CommandM Status
    status = do
      cf <- gets theCurrentFile
      showImpl <- lift showImplicitArguments

      -- Check if the file was successfully type checked, and has not
      -- changed since. Note: This code does not check if any dependencies
      -- have changed, and uses a time stamp to check for changes.
      checked  <- lift $ case cf of
        Nothing     -> return False
        Just (f, t) -> do
          t' <- liftIO $ getModificationTime $ filePath f
          case t == t' of
            False -> return False
            True  -> do
              mm <- lookupModuleFromSource f
              case mm of
                Nothing -> return False -- work-around for Issue1007
                Just m  -> maybe False (not . miWarnings) <$> getVisitedModule m

      return $ Status { sShowImplicitArguments = showImpl
                      , sChecked               = checked
                      }

    -- | Displays or updates status information.
    --
    --   Does not change the state.

    displayStatus :: CommandM ()
    displayStatus =
      putResponse . Resp_Status  =<< status

    -- | @display_info@ does what @'display_info'' False@ does, but
    --   additionally displays some status information (see 'status' and
    --   'displayStatus').

    display_info :: DisplayInfo -> CommandM ()
    display_info info = do
      displayStatus
      putResponse $ Resp_DisplayInfo info

    refreshStr :: [String] -> String -> ([String], String)
    refreshStr taken s = go nameModifiers where
      go (m:mods) = let s' = s ++ m in
                    if s' `elem` taken then go mods else (s':taken, s')
      go _        = __IMPOSSIBLE__

    nameModifiers :: [String]
    nameModifiers = "" : "'" : "''" : [show i | i <-[3..]]

    -- | Parses and scope checks an expression (using the \"inside scope\"
    -- as the scope), performs the given command with the expression as
    -- input, and displays the result.

    parseAndDoAtToplevel
      :: (A.Expr -> TCM Doc)
         -- ^ The command to perform.
      -> (Doc -> DisplayInfo)
         -- ^ The name to use for the buffer displaying the output.
      -> String
         -- ^ The expression to parse.
      -> CommandM ()
    parseAndDoAtToplevel cmd title s = do
      (time, res) <- localStateCommandM $ do
        e <- lift $ runPM $ parse exprParser s
        maybeTimed $ lift $ B.atTopLevel $ do
          cmd =<< concreteToAbstract_ e
      display_info $ title $ fromMaybe empty time $$ res

    maybeTimed :: CommandM a -> CommandM (Maybe Doc, a)
    maybeTimed work = do
      doTime <- lift $ hasVerbosity "profile.interactive" 10
      if not doTime then (Nothing,) <$> work else do
        (r, time) <- measureTime work
        return (Just $ "Time:" <+> pretty time, r)

    -- | Tell to highlight the code using the given highlighting
    -- info (unless it is @Nothing@).

    tellToUpdateHighlighting
      :: Maybe (HighlightingInfo, HighlightingMethod, ModuleToSource) -> IO [Response]
    tellToUpdateHighlighting Nothing                = return []
    tellToUpdateHighlighting (Just (info, method, modFile)) =
      return [Resp_HighlightingInfo info KeepHighlighting method modFile]

    -- | Tells the Emacs mode to go to the first error position (if any).

    tellEmacsToJumpToError :: Range -> [Response]
    tellEmacsToJumpToError r =
      case rStart r of
        Nothing                                           -> []
        Just (Pn { srcFile = Strict.Nothing })            -> []
        Just (Pn { srcFile = Strict.Just f, posPos = p }) ->
           [ Resp_JumpToError (filePath f) p ]