module Tcp (runServer) where

import Control.Concurrent (forkFinally)
import qualified Control.Exception as E
import Control.Monad (forever, void)
import Intro
import Network.Socket
  ( AddrInfoFlag (AI_PASSIVE)
  , HostName
  , ServiceName
  , Socket
  , SocketOption (ReuseAddr)
  , SocketType (Stream)
  , accept
  , addrAddress
  , addrFlags
  , addrSocketType
  , bind
  , close
  , defaultHints
  , getAddrInfo
  , gracefulClose
  , listen
  , openSocket
  , setCloseOnExecIfNeeded
  , setSocketOption
  , withFdSocket
  , withSocketsDo
  )

runServer :: Maybe HostName -> ServiceName -> (Socket -> IO a) -> IO a
runServer host port server = withSocketsDo $ do
  addr <- resolve
  E.bracket (open addr) close go
 where
  resolve = do
    let hints = defaultHints{addrFlags = [AI_PASSIVE], addrSocketType = Stream}
    head <$> getAddrInfo (Just hints) host (Just port)
  open addr = E.bracketOnError (openSocket addr) close $ \sock -> do
    setSocketOption sock ReuseAddr 1
    withFdSocket sock setCloseOnExecIfNeeded
    bind sock $ addrAddress addr
    listen sock 1024
    pure sock
  go :: Socket -> IO a
  go sock = forever
    $ E.bracketOnError (accept sock) (close . fst)
    $ \(conn, _peer) ->
      void
        $ forkFinally (server conn) (const $ gracefulClose conn 5000)