{-
 Copyright (C) 2012-2013 Jimmy Liang <http://gsd.uwaterloo.ca>

 Permission is hereby granted, free of charge, to any person obtaining a copy of
 this software and associated documentation files (the "Software"), to deal in
 the Software without restriction, including without limitation the rights to
 use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
 of the Software, and to permit persons to whom the Software is furnished to do
 so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
-}

module Language.Clafer.IG.Process (Process, executableDirectory, waitFor, getContentsVerbatim, getMessage, readMessage, putMessage, pipeProcess) where

import Control.Monad
import Control.Monad.IO.Class
import System.Environment.Executable
import System.IO
import System.Process
import GHC.IO.Exception

data Process = Process{stdIn::Handle, stdOut::Handle, procHandle::ProcessHandle}



executableDirectory :: IO FilePath
executableDirectory = fst `liftM` splitExecutablePath


-- | Start another process and return the piped std_in, std_out stream
pipeProcess :: FilePath -> [String] -> IO Process
pipeProcess exec args =
    do
        let process = (proc exec args) { std_in = CreatePipe, std_out = CreatePipe }
        (Just stdIn', Just stdOut', _, proceHandle) <- createProcess process
        hSetNewlineMode stdIn' noNewlineTranslation
        return $ Process stdIn' stdOut' proceHandle -- Pipe always has a handle according to docs
    
    
-- | Wait until the process terminates
waitFor :: Process -> IO ExitCode
waitFor proce = waitForProcess (procHandle proce)


-- | Reads the entire output verbatim
getContentsVerbatim :: Process -> IO String
getContentsVerbatim proce =
    do
        contents <- hGetContents $ stdOut proce
        -- hGetContents is lazy. Force it to evaluate by mapping over everything doing nothing
        mapM_ return contents
        return contents

    
-- | Read the message
getMessage :: MonadIO m => Process -> m String
getMessage proce =
    liftIO $ do
        len <- read `liftM` hGetLine (stdOut proce)
        mapM hGetChar $ replicate len (stdOut proce)

readMessage :: (Read r, MonadIO m) => Process -> m r   
readMessage proce = read `liftM` getMessage proce

-- | Put the message
putMessage :: MonadIO m => Process -> String -> m ()
putMessage proce message =
    liftIO $ do
        hPutStrLn (stdIn proce) (show $ length message)
        hPutStr (stdIn proce) message
        hFlush (stdIn proce)