{-# OPTIONS -cpp #-}
-----------------------------------------------------------------------------
-- |
-- Module : System.Console.SimpleLineEditor
-- Copyright : (c) 2000,2003, Malcolm Wallace
-- License : GPL (if it depends on readline, which is GPL)
-- BSD (otherwise)
--
-- Maintainer : libraries@haskell.org
-- Stability : experimental
-- Portability : non-portable (unix-specific at the moment)
--
-- A simple line editor, using the GNU readline library if available,
-- or a small emulation otherwise.
--
-----------------------------------------------------------------------------
module SimpleLineEditor
( initialise -- :: IO ()
, restore -- :: IO ()
, getLineEdited -- :: String -> IO (Maybe String)
, delChars -- :: String -> IO ()
) where
import IO
import Monad (when)
import Char (isSpace)
#if USE_READLINE
import System.Console.Readline
#else
#if defined(__HBC__)
import IOExts (IORef, newIORef, readIORef, writeIORef, unsafePerformIO)
#else
import Data.IORef (IORef, newIORef, readIORef, writeIORef)
import System.IO.Unsafe (unsafePerformIO)
#endif
import System (system)
#endif
-- | Set up the environment so that the terminal passes characters directly
-- into the Haskell program, for immediate interpretation by the line editor.
initialise :: IO ()
initialise = do
-- The following call is probably non-portable. Better suggestions?
-- Note, we turn OFF terminal echoing of input characters
#if ! USE_READLINE
system("stty -icanon min 1 -echo")
#endif
hSetBuffering stdout NoBuffering
hSetBuffering stdin NoBuffering
#if USE_READLINE
initialize
#endif
-- | Restore the environment so that the terminal is usable in normal
-- mode once again.
restore :: IO ()
restore = do
-- The following call is probably non-portable. Better suggestions?
-- Note, we assume the terminal DOES NOT echo any input character
#if ! USE_READLINE
system("stty icanon echo")
#endif
hSetBuffering stdout LineBuffering
hSetBuffering stdin LineBuffering
-- | Remove the given string from immediately behind (to the left of) the
-- current cursor position.
delChars :: String -> IO ()
delChars [] = return ()
delChars (_:xs) = do putStr "\BS \BS"
delChars xs
-- | 'getLineEdited p' uses the string 'p' as a prompt, and returns a line
-- of input from the user. The user can edit the line in-place before
-- completion, using common readline-like command keys. (The real readline
-- is used when available, or otherwise a simplified emulation.)
#if USE_READLINE
getLineEdited :: String -> IO (Maybe String)
getLineEdited prompt = do
ms <- readline prompt
case ms of
Nothing -> return ms
Just s -> when (not (all isSpace s)) (addHistory s) >> return ms
#else
-- nasty imperative state holds the command history
history :: IORef [String]
history = unsafePerformIO (newIORef [])
getLineEdited :: String -> IO (Maybe String)
getLineEdited prompt = do
putStr prompt
previous <- readIORef history
ms <- gl "" 0 ([],previous)
case ms of
Nothing -> return ms
Just s -> do when (not (all isSpace s))
(writeIORef history (reverse s: previous))
return ms
where
gl s 0 hist = do -- s is accumulated line (in reverse)
-- 0 is cursor position FROM THE END of the string
cmd <- lineCmd
case cmd of
Char c -> putChar c >> gl (c:s) 0 hist
Accept -> return (Just (reverse s))
Cancel -> return Nothing
Delete L -> if null s then gl s 0 hist
else delChars "_" >> gl (tail s) 0 hist
Delete Begin -> delChars s >> gl "" 0 hist
Move L -> if not (null s) then putStr ("\BS") >> gl s 1 hist
else gl s 0 hist
History -> case hist of
(_fut, []) -> gl s 0 hist
(fut, p:past) -> do delChars s
putStr (reverse p)
gl p 0 (s:fut, past)
Future -> case hist of
([], _past) -> gl s 0 hist
(f:fut, past) -> do delChars s
putStr (reverse f)
gl f 0 (fut, s:past)
_ -> gl s 0 hist
gl s n hist = do -- s is accumulated line, n(/=0) is cursor position
cmd <- lineCmd
case cmd of
Char c -> do putStr (c: reverse (take n s))
putStr (replicate n '\BS')
gl (take n s ++ c: drop n s) n hist
Accept -> return (Just (reverse s))
Cancel -> return Nothing
Move R -> do let n1 = n-1
putStr (reverse (take n s)++" ")
putStr (replicate n '\BS')
gl s n1 hist
Delete R -> do let n1 = n-1
putStr (reverse (take n1 s) ++ " ")
putStr (replicate (n1+1) '\BS')
gl (take n1 s ++ drop n s) n1 hist
Move L -> do let n1 = n+1
if n1 <= length s then do
putStr ('\BS':reverse (take n1 s))
putStr (replicate n1 '\BS')
gl s n1 hist
else do
putStr (reverse s++" ")
putStr (replicate n1 '\BS')
gl s n hist
Delete L -> do let n1 = n+1
if n1 <= length s then do
putStr ('\BS':reverse (take n s)++" ")
putStr (replicate n1 '\BS')
gl (take n s ++ drop n1 s) n hist
else do
putStr (reverse s++" ")
putStr (replicate n1 '\BS')
gl s n hist
History -> case hist of
(_fut, []) -> gl s n hist
(fut, p:past) -> do putStr (replicate n ' ')
delChars s
putStr (reverse p)
gl p 0 (s:fut, past)
Future -> case hist of
([], _past) -> gl s n hist
(f:fut, past) -> do putStr (replicate n ' ')
delChars s
putStr (reverse f)
gl f 0 (fut, s:past)
_ -> gl s n hist
-- Define a mini-command language, to separate the lexing of input
-- commands from their interpretation. Note there is room for expansion
-- here, e.g. commands include word-at-a-time movement, but we don't
-- currently have a key binding for that.
data LineCmd = Char Char | Move Cursor | Delete Cursor
| Accept | Cancel | History | Future | NoOp
data Cursor = L | R | Begin | End -- not implemented yet: | WordL | WordR
-- This little lexer for keystrokes does a reasonable job, but there
-- are plenty of problems. E.g. the backspace key might generate a
-- ^H character and not display it, which results in a mismatched cursor
-- position. Behaviour is highly dependent on terminal settings I imagine.
lineCmd :: IO LineCmd
lineCmd = do
c1 <- hGetChar stdin
case c1 of
'\n' -> putChar '\n' >> return Accept
'\^K' -> putChar '\n' >> return Cancel
'\DEL' -> return (Delete L)
'\BS' -> return (Delete L)
'\^L' -> return (Move R)
'\^[' -> do
c2 <- hGetChar stdin
case c2 of
'k' -> return History
'j' -> return Future
'[' -> do
c3 <- hGetChar stdin
case c3 of
'D' -> return (Move L)
'C' -> return (Move R)
'A' -> return History
'B' -> return Future
'3' -> do c <- hGetChar stdin
case c of
'~' -> return (Delete R)
_ -> return NoOp
'4' -> do c <- hGetChar stdin
case c of
'~' -> return (Move End)
_ -> return NoOp
'1' -> do c <- hGetChar stdin
case c of
'~' -> return (Move Begin)
_ -> return NoOp
_ -> return NoOp
'O' -> do
c3 <- hGetChar stdin
case c3 of
'D' -> return (Move L)
'C' -> return (Move R)
'A' -> return History
'B' -> return Future
_ -> return NoOp
_ -> return NoOp
_ -> return (Char c1)
#endif /* USE_READLINE */
{-
-- | A simple interactive test for the line-editing functionality.
-- (This illustrates the necessary use of 'initialise' and 'restore'
-- as brackets around the editing loop.)
testIt :: IO ()
testIt = initialise >> loop >> restore
where loop = do l <- getLineEdited "prompt> "
when (isJust l) (putStrLn (fromJust l))
when (l/=Just "quit") loop
-}
|
