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{-# LANGUAGE NondecreasingIndentation #-}
import Control.Applicative
import Control.Monad
import Data.Function
import Control.Monad.IO.Class
import Data.Char
import Data.List
import Network.Socket as Socket
import System.Console.Haskeline
import System.Environment
import System.Exit
import System.IO
import System.IO.Unsafe
import qualified Data.ByteString as B
-- | Reads one character. If it is not a digit,
-- then it is discarded and 'Nothing' is returned.
hReadDigit :: Handle -> IO (Maybe Char)
hReadDigit h = do c <- hGetChar h
return $ guard (isDigit c) >> pure c
-- | Expected input: "nnn:..."
-- Here we read the digit sequence "nnn" and drop the colon
-- as it is the first non-digit.
hReadInt :: Handle -> IO Int
hReadInt h = do
nstr <- fix $ \readDigits ->
maybe (return []) -- dropped non-digit character
(($ unsafeInterleaveIO readDigits) . fmap . (:))
=<< hReadDigit h
readIO nstr :: IO Int
-- | Read a length prefixed string from a handle.
-- The format is "nnn:..." where /nnn/ is an ascii-encoded character count
-- and /.../ is the sequence of characters
--
-- Note: The first byte after the count is ignored and discarded.
readResponse :: Handle -> IO (Char, String)
readResponse h = do
c <- hGetChar h
n <- hReadInt h
s <- sequence $ replicate n (hGetChar h)
return (c,s)
-- | Send a command to the dhtd daemon and then print the response.
sendCommand :: Handle -> String -> InputT IO ()
sendCommand h cmd = do liftIO $ hPutStrLn h cmd
fix $ \again -> do
(c, resp) <- liftIO $ readResponse h
if c /= '.'
then outputStr resp >> again
else outputStrLn resp
-- | Get one line of input and send it to the daemon, then run the
-- passed continuation if it wasn't "quit".
interactiveMode :: Handle -> InputT IO () -> InputT IO ()
interactiveMode h repl = do
minput <- getInputLine "dht> "
case minput of
Nothing -> return ()
Just "quit" -> sendCommand h "quit" >> return ()
Just cmd -> sendCommand h cmd >> repl
main :: IO ()
main = do
-- Open the control socket to the daemon.
h <- liftIO $ handle (\e -> do hPutStrLn stderr (show (e ::IOError))
exitFailure)
$ do sock <- socket AF_UNIX Stream defaultProtocol
connect sock (SockAddrUnix "dht.sock")
socketToHandle sock ReadWriteMode
-- Haskeline's default looks only at our stdin and not our stdout.
-- That's a bad idea because we can take input from the command line.
behavior <- do
useTerminal <- and <$> mapM hIsTerminalDevice [stdin,stdout]
return $ if useTerminal then preferTerm else useFileHandle stdin
runInputTBehaviorWithPrefs behavior defaultPrefs defaultSettings $ do
-- A command may be specified on the command line
-- or else we enter an interactive shell.
args <- dropWhile isSpace . unwords <$> liftIO getArgs
case args of
(_:_) -> do
let cs = filter (not . null) $ map (drop 1) $ groupBy (\_ c -> (c/=';')) (';':args)
forM_ cs $ \cmd -> sendCommand h cmd
sendCommand h "quit"
_ -> fix $ interactiveMode h
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