import Network.Socket
import qualified Network.BSD as BSD
import ControlMaybe
import Control.Exception ({-evaluate,-}handle,SomeException(..),bracketOnError,ErrorCall(..))
import System.IO.Error (isDoesNotExistError)
import System.Endian
import Data.List (nub)
import qualified Data.Text as Text
import GetHostByAddr (getHostByAddr)
import Control.Concurrent
import Control.Concurrent.STM
import Control.Monad
import System.Environment

unmap6mapped4 addr@(SockAddrInet6 port _ (0,0,0xFFFF,a) _) =
    SockAddrInet port (toBE32 a)
unmap6mapped4 addr = addr

make6mapped4 addr@(SockAddrInet6 {}) = addr
make6mapped4 addr@(SockAddrInet port a) = SockAddrInet6 port 0 (0,0,0xFFFF,fromBE32 a) 0


reverseResolve addr = 
    handleIO_ (return []) $ do
        ent <- getHostByAddr (unmap6mapped4 addr) --  AF_UNSPEC addr
        let names = BSD.hostName ent : BSD.hostAliases ent
        return $ map Text.pack $ nub names

forwardResolve addrtext = do
    r <- atomically newEmptyTMVar
    mvar <- atomically newEmptyTMVar
    rt <- forkOS $ resolver r mvar
    tt <- forkIO $ timer r rt
    atomically $ putTMVar mvar tt
    atomically $ readTMVar r
 where
    resolver r mvar = do
      xs <- handle (\e -> let _ = isDoesNotExistError e in return [])
            $ do fmap (map $ make6mapped4 . addrAddress) $ 
                  getAddrInfo (Just $ defaultHints { addrFlags = [ AI_CANONNAME, AI_V4MAPPED ]})
                    (Just $ Text.unpack $ strip_brackets addrtext)
                    (Just "5269")
      did <- atomically $ tryPutTMVar r (nub xs)
      when did $ do
      tt <- atomically $ readTMVar mvar
      throwTo tt (ErrorCall "Interrupted delay")
      return ()
    timer r rt = do
      handle (\(ErrorCall _)-> return ()) $ do
      threadDelay 2000000
      did <- atomically $ tryPutTMVar r []
      when did $ do
      putStrLn $ "timeout resolving: "++show addrtext
      killThread rt
    strip_brackets s = 
      case Text.uncons s of
          Just ('[',t) -> Text.takeWhile (/=']') t
          _            -> s

main = do
    args <- getArgs
    forM args $ \arg -> do
    putStrLn $ arg ++ ":"
    let targ = Text.pack arg
    addrs <- forwardResolve targ
    putStrLn $ "  forward: " ++ show addrs
    forM addrs $ \addr -> do
        names <- reverseResolve addr
        putStrLn $ "  reverse "++show addr++": "++show names
    return ()