{-# LANGUAGE OverloadedStrings #-}

module Main where

import Network.Socket hiding (send, sendTo, recv, recvFrom)
import Network.Socket.ByteString
import Control.Concurrent
import Control.Exception
import Control.Monad (forever)
import System.IO (
        IOMode (ReadWriteMode)
                 )
import qualified Data.ByteString as BS

main = do
    sock <- socket AF_INET6 Datagram defaultProtocol
    -- lookup destination to get a SockAddr
    let hints = defaultHints { addrFamily = AF_INET6, addrSocketType = Datagram}
    serverAddr <- addrAddress . head <$> getAddrInfo (Just hints) (Just "::1") (Just "7331")
    print serverAddr
    bind sock serverAddr
    print sock
    forever $ do
        receivedStuff <- recvFrom sock 65535    -- blocks
        forkIO $ bracket newSendSocket close (serveReceive receivedStuff)

serveReceive :: (BS.ByteString, SockAddr) -> Socket -> IO ()
serveReceive (msg, fromAddr) sendSocket = do
    print sendSocket
    putStrLn $ "Got message " ++ show msg ++ " from " ++ show fromAddr
    -- important: as new socket sends from a different port, the receiving client must use an unconnected socket!
    sentBytes <- sendTo sendSocket ("Hi, thx for " `BS.append` msg) fromAddr
    putStrLn $ "sent response of " ++ show sentBytes ++ "bytes"
    return ()

newSendSocket :: IO Socket
newSendSocket = socket AF_INET6 Datagram defaultProtocol