rmw-stun 0.0.2

use async_std::io;
use async_std::net::UdpSocket;
use std::net::{SocketAddr, ToSocketAddrs};
use std::time::Duration;
use stun::agent::TransactionId;
use stun::message::{Getter, Message, BINDING_REQUEST};
use stun::xoraddr::XorMappedAddress;

pub async fn external_addr<T: ToSocketAddrs>(
  udp: &UdpSocket,
  server: T,
  timeout: u64,
) -> Option<SocketAddr> {
  let mut bin = Message::new();
  bin
    .build(&[
      Box::new(TransactionId::default()),
      Box::new(BINDING_REQUEST),
    ])
    .unwrap();
  let bin = bin.marshal_binary().unwrap();
  if let Ok(mut li) = server.to_socket_addrs() {
    if let Some(addr) = li.next() {
      udp.send_to(&bin, addr).await.unwrap();
      match io::timeout(Duration::from_secs(timeout), async move {
        loop {
          let mut buf = vec![0u8; 1472];
          if let Ok((n, peer)) = udp.recv_from(&mut buf).await {
            if peer == addr {
              let mut xor_addr = XorMappedAddress::default();
              let mut msg = Message::new();
              if msg.unmarshal_binary(&buf[..n]).is_ok() && xor_addr.get_from(&msg).is_ok() {
                return Ok(SocketAddr::new(xor_addr.ip, xor_addr.port));
              }
            }
          }
        }
      })
      .await
      {
        Ok(r) => return Some(r),
        _ => return None,
      }
    }
  }
  None
}