module Protocol where

import System.IO
import Options
import Network (PortID(..), Socket, listenOn)
import System.Random (randomRIO)

data Protocol
    = Exec String
    | Kill
    | GetOptions
    | SetOptions String
      deriving (Show, Read)

put :: Handle -> Protocol -> IO()
put handle msg
    = do hPutStrLn handle $ show msg
         hFlush handle

get :: (Read a) => Handle -> IO a
get handle = hGetLine handle >>= readIO

{- From GUI-API -}

isExecuting :: Handle -> IO (Maybe Bool)
isExecuting handle
    = do x <- hReady handle
         case x of
           False -> return Nothing
           True  -> do msg <- hGetLine handle
                       readIO msg >>= return . Just

kill :: Handle -> IO ()
kill handle
    = do put handle Kill

getOptions :: Handle -> IO Options
getOptions handle
    = do put handle GetOptions
         get handle
         
setOptions :: Options -> Handle -> IO ()
setOptions options handle
    = do put handle $ SetOptions $ show options

executeStmt :: String -> Handle -> IO ()
executeStmt stmt handle
    = do put handle $ Exec stmt

{- From GHCProcess to GUI -}
setIsExecuting :: Handle -> Bool -> IO()
setIsExecuting handle is = do hPutStrLn handle $ show is
                              hFlush handle

listenOnRandomPort :: Int               -- ^ Number of tries
                   -> IO(Socket, Int)
listenOnRandomPort 0 = error "Could not establish socket connection"
listenOnRandomPort tries = tryGetSocket `catch` tryAgain where
    tryGetSocket = do port <- randomRIO (16384, 65535)
                      socket <- listenOn (PortNumber $ fromIntegral port)
                      return (socket, port)
    tryAgain _   = listenOnRandomPort (tries-1)