{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ExistentialQuantification #-}
{-# LANGUAGE ForeignFunctionInterface #-}
{-# LANGUAGE InterruptibleFFI #-}
{-# LANGUAGE EmptyDataDecls #-}

module System.IO.Uniform.Targets (TlsSettings(..), UniformIO(..), SocketIO, FileIO, StdIO, TlsStream, BoundedPort, SomeIO(..), connectTo, connectToHost, bindPort, accept, openFile, getPeer, closePort) where

import Foreign
import Foreign.C.Types
import Foreign.C.String
import Foreign.C.Error
import qualified Data.IP as IP
import Data.ByteString (ByteString)
import qualified Data.ByteString as BS
import qualified Data.List as L
import Control.Exception
import Control.Applicative ((<$>))
import qualified Network.Socket as Soc
import System.IO.Error

import Data.Default.Class

import System.Posix.Types (Fd(..))

-- | Settings for starttls functions.
data TlsSettings = TlsSettings {tlsPrivateKeyFile :: String, tlsCertificateChainFile :: String, tlsDHParametersFile :: String} deriving (Read, Show)

instance Default TlsSettings where
  def = TlsSettings "" "" ""

-- |
-- Typeclass for uniform IO targets.
class UniformIO a where
  -- | uRead fd n
  --
  --  Reads a block of at most n bytes of data from the IO target.
  --  Reading will block if there's no data available, but will return immediately
  --  if any amount of data is availble.
  uRead  :: a -> Int -> IO ByteString
  -- | uPut fd text
  --
  --  Writes all the bytes of text into the IO target. Takes care of retrying if needed.
  uPut   :: a -> ByteString -> IO ()
  -- | fClose fd
  --
  --  Closes the IO target, releasing any allocated resource. Resources may leak if not called
  --  for every oppened fd.
  uClose :: a -> IO ()
  -- | startTLS fd
  --
  --  Starts a TLS connection over the IO target.
  startTls :: TlsSettings -> a -> IO TlsStream
  -- | isSecure fd
  --
  --  Indicates whether the data written or read from fd is secure at transport.
  isSecure :: a -> Bool
  
-- | A type that wraps any type in the UniformIO class.
data SomeIO = forall a. (UniformIO a) => SomeIO a

instance UniformIO SomeIO where
  uRead (SomeIO s) n = uRead s n
  uPut (SomeIO s) t  = uPut s t
  uClose (SomeIO s) = uClose s
  startTls set (SomeIO s) = startTls set s
  isSecure (SomeIO s) = isSecure s

data Nethandler
-- | A bounded IP port from where to accept SocketIO connections.
newtype BoundedPort = BoundedPort {lis :: (Ptr Nethandler)}
data Ds
newtype SocketIO = SocketIO {sock :: (Ptr Ds)}
newtype FileIO = FileIO {fd :: (Ptr Ds)}
data TlsDs
newtype TlsStream = TlsStream {tls :: (Ptr TlsDs)}
data StdIO

-- | UniformIO IP connections.
instance UniformIO SocketIO where
  uRead s n = do
    allocaArray n (
      \b -> do
        count <- c_recv (sock s) b (fromIntegral n)
        if count < 0
          then throwErrno "could not read"
          else BS.packCStringLen (b, fromIntegral count)
      )
  uPut s t = do
    BS.useAsCStringLen t (
      \(str, n) -> do
        count <- c_send (sock s) str $ fromIntegral n
        if count < 0
          then throwErrno "could not write"
          else return ()
      )
  uClose s = do
    f <- Fd <$> c_prepareToClose (sock s)
    closeFd f
  startTls st s = withCString (tlsCertificateChainFile st) (
    \cert -> withCString (tlsPrivateKeyFile st) (
      \key -> withCString (tlsDHParametersFile st) (
        \para -> do
          r <- c_startSockTls (sock s) cert key para
          if r == nullPtr
            then throwErrno "could not start TLS"
            else return . TlsStream $ r
        )
      )
    )
  isSecure _ = False
  
-- | UniformIO IP connections.
instance UniformIO StdIO where
  uRead _ n = do
    allocaArray n (
      \b -> do
        count <- c_recvStd b (fromIntegral n)
        if count < 0
          then throwErrno "could not read"
          else BS.packCStringLen (b, fromIntegral count)
      )
  uPut _ t = do
    BS.useAsCStringLen t (
      \(str, n) -> do
        count <- c_sendStd str $ fromIntegral n
        if count < 0
          then throwErrno "could not write"
          else return ()
      )
  uClose _ = return ()
  startTls _ _ = return . TlsStream $ nullPtr
  isSecure _ = False
  
-- | UniformIO type for file IO.
instance UniformIO FileIO where
  uRead s n = do
    allocaArray n (
      \b -> do
        count <- c_recv (fd s) b $ fromIntegral n
        if count < 0
          then throwErrno "could not read"
          else  BS.packCStringLen (b, fromIntegral count)
      )
  uPut s t = do
    BS.useAsCStringLen t (
      \(str, n) -> do
        count <- c_send (fd s) str $ fromIntegral n
        if count < 0
          then throwErrno "could not write"
          else return ()
      )
  uClose s = do
    f <- Fd <$> c_prepareToClose (fd s)
    closeFd f
  -- Not implemented yet.
  startTls _ _ = return . TlsStream $ nullPtr
  isSecure _ = False
  
-- | UniformIO wrapper that applies TLS to communication on IO target.
-- This type is constructed by calling startTls on other targets.
instance UniformIO TlsStream where
  uRead s n = do
    allocaArray n (
      \b -> do
        count <- c_recvTls (tls s) b $ fromIntegral n
        if count < 0
          then throwErrno "could not read"
          else BS.packCStringLen (b, fromIntegral count)
      )
  uPut s t = do
    BS.useAsCStringLen t (
      \(str, n) -> do
        count <- c_sendTls (tls s) str $ fromIntegral n
        if count < 0
          then throwErrno "could not write"
          else return ()
      )
  uClose s = do
    d <- c_closeTls (tls s)
    f <- Fd <$> c_prepareToClose d
    closeFd f
  startTls _ s = return s
  isSecure _ = True

-- | connectToHost hostName port
--
--  Connects to the given host and port.
connectToHost :: String -> Int -> IO SocketIO
connectToHost host port = do
  ip <- getAddr
  connectTo ip port
  where
    getAddr :: IO IP.IP
    getAddr = do
      add <- Soc.getAddrInfo Nothing (Just host) Nothing
      case add of
        [] -> throwIO $ mkIOError doesNotExistErrorType "host not found" Nothing Nothing
        (a:_) -> case Soc.addrAddress a of
          Soc.SockAddrInet _ a'  -> return . IP.IPv4 . IP.fromHostAddress $ a'
          Soc.SockAddrInet6 _ _ a' _ -> return . IP.IPv6 . IP.fromHostAddress6 $ a'
          _ -> throwIO $ mkIOError doesNotExistErrorType "host not found" Nothing Nothing


-- | ConnecctTo ipAddress port
--
--  Connects to the given port of the host at the given IP address.
connectTo :: IP.IP -> Int -> IO SocketIO
connectTo host port = do
  r <- case host of
    IP.IPv4 host' -> fmap SocketIO $ c_connect4 (fromIntegral . IP.toHostAddress $ host') (fromIntegral port)
    IP.IPv6 host' -> fmap SocketIO $ withArray (ipToArray host') (
      \add -> c_connect6 add (fromIntegral port)
      )
  if sock r == nullPtr
    then throwErrno "could not connect to host"
    else return r
  where
    ipToArray :: IP.IPv6 -> [CUChar]
    ipToArray ip = let
      (w0, w1, w2, w3) = IP.toHostAddress6 ip
      in L.concat [wtoc w0, wtoc w1, wtoc w2, wtoc w3]
    wtoc :: Word32 -> [CUChar]
    wtoc w = let
      c0 = fromIntegral $ mod w 256
      w1 = div w 256
      c1 = fromIntegral $ mod w1 256
      w2 = div w1 256
      c2 = fromIntegral $ mod w2 256
      c3 = fromIntegral $ div w2 256
      in [c3, c2, c1, c0]
  
-- | bindPort port
--  Binds to the given IP port, becoming ready to accept connections on it.
--  Binding to port numbers under 1024 will fail unless performed by the superuser,
--  once bounded, a process can reduce its privileges and still accept clients on that port.
bindPort :: Int -> IO BoundedPort
bindPort port = do
  r <- fmap BoundedPort $ c_getPort $ fromIntegral port
  if lis r == nullPtr
    then throwErrno "could not bind to port"
    else return r
  
-- | accept port
--
--  Accept clients on a port previously bound with bindPort.
accept :: BoundedPort -> IO SocketIO
accept port = do
  r <- fmap SocketIO $ c_accept (lis port)
  if sock r == nullPtr
    then throwErrno "could not accept connection"
    else return r
  
-- | Open a file for bidirectional IO.
openFile :: String -> IO FileIO
openFile fileName = do
  r <- withCString fileName (
    \f -> fmap FileIO $ c_createFile f
    )
  if fd r == nullPtr
    then throwErrno "could not open file"
    else return r

-- | Gets the address of the peer socket of a internet connection.
getPeer :: SocketIO -> IO (IP.IP, Int)
getPeer s = allocaArray 16 (
  \p6 -> alloca (
    \p4 -> alloca (
      \iptype -> do
        p <- c_getPeer (sock s) p4 p6 iptype
        if p == -1
          then throwErrno "could not get peer address"
          else do
          iptp <- peek iptype
          if iptp == 1
            then do --IPv6
            add <- peekArray 16 p6
            return (IP.IPv6 . IP.toIPv6b $ map fromIntegral add, fromIntegral p)
            else do --IPv4
            add <- peek p4
            return (IP.IPv4 . IP.fromHostAddress . fromIntegral $ add, fromIntegral p)
      )
    )
  )
    
closeFd :: Fd -> IO ()
closeFd (Fd f) = c_closeFd f
            
-- | Closes a BoundedPort, and releases any resource used by it.
closePort :: BoundedPort -> IO ()
closePort p = c_closePort (lis p)

foreign import ccall interruptible "getPort" c_getPort :: CInt -> IO (Ptr Nethandler)
foreign import ccall interruptible "createFromHandler" c_accept :: Ptr Nethandler -> IO (Ptr Ds)
foreign import ccall safe "createFromFileName" c_createFile :: CString -> IO (Ptr Ds)
foreign import ccall interruptible "createToIPv4Host" c_connect4 :: CUInt -> CInt -> IO (Ptr Ds)
foreign import ccall interruptible "createToIPv6Host" c_connect6 :: Ptr CUChar -> CInt -> IO (Ptr Ds)

foreign import ccall interruptible "startSockTls" c_startSockTls :: Ptr Ds -> CString -> CString -> CString -> IO (Ptr TlsDs)
foreign import ccall safe "getPeer" c_getPeer :: Ptr Ds -> Ptr CUInt -> Ptr CUChar -> Ptr CInt -> IO (CInt)

--foreign import ccall safe "getFd" c_getFd :: Ptr Ds -> IO CInt
--foreign import ccall safe "getTlsFd" c_getTlsFd :: Ptr TlsDs -> IO CInt
foreign import ccall safe "closeFd" c_closeFd :: CInt -> IO ()

foreign import ccall safe "prepareToClose" c_prepareToClose :: Ptr Ds -> IO CInt
foreign import ccall safe "closeHandler" c_closePort :: Ptr Nethandler -> IO ()
foreign import ccall safe "closeTls" c_closeTls :: Ptr TlsDs -> IO (Ptr Ds)

foreign import ccall interruptible "sendDs" c_send :: Ptr Ds -> Ptr CChar -> CInt -> IO CInt
foreign import ccall interruptible "stdDsSend" c_sendStd :: Ptr CChar -> CInt -> IO CInt
foreign import ccall interruptible "tlsDsSend" c_sendTls :: Ptr TlsDs -> Ptr CChar -> CInt -> IO CInt

foreign import ccall interruptible "recvDs" c_recv :: Ptr Ds -> Ptr CChar -> CInt -> IO CInt
foreign import ccall interruptible "stdDsRecv" c_recvStd :: Ptr CChar -> CInt -> IO CInt
foreign import ccall interruptible "tlsDsRecv" c_recvTls :: Ptr TlsDs -> Ptr CChar -> CInt -> IO CInt