--  SpawnEchoShiftLetters.hs
--
--  Test program for popen function.
--  This is essentially the same program as SpawnEchoShiftLetters.c,
--  written to use the Haskell interface (POpen.hs) to spawnProc.c

module SpawnEchoShiftLetters
where

import Win32.POpen (popen, popenEnvDir)

import System.Environment( getArgs )
import System.Exit( ExitCode(ExitSuccess,ExitFailure) )
import Data.Char( isSpace )

main :: IO ()
main =
    do  { argv <- getArgs
        ; mainBody argv
        ; return ()
        }

mainBody :: [String] -> IO String
mainBody argv =
    do  { (res, errs, pid) <- popen "EchoShiftLetters.exe" []
                (Just "abcdefghijklmnopqrstuvwxyz")
        ; putStrLn ("pid:    "++(show pid))
        ; putStrLn ("input:  "++"abcdefghijklmnopqrstuvwxyz")
        ; putStrLn ("errout: "++errs)
        ; putStrLn ("stdout: "++res)
        ; return res
        }

-- Function for running program within Hugs
runMain :: String -> IO ExitCode
runMain cmdline =
    do  { let argv = breakAll isSpace cmdline
        ; res <- mainBody argv
        ; let ec = if null res then (ExitFailure 2) else ExitSuccess
        ; if (ec /= ExitSuccess)
            then (putStrLn $ "HXml Parser exit: "++show ec)
            else (return ())
        ; return ec
        }

-- |Break list into a list of sublists, separated by element
--  satisfying supplied condition.
breakAll :: (a -> Bool) -> [a] -> [[a]]
breakAll _ [] = []
breakAll p s  = let (h,s') = break p s
                    in h : breakAll p (drop 1 s')

--  Quick run test case
runTest = runMain ""