use etherparse::Icmpv4Header;
use ipstack::{IpNumber, IpStackStream};
use std::net::{Ipv4Addr, SocketAddr};
use tokio::{io::AsyncWriteExt, net::TcpStream};
use udp_stream::UdpStream;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    const MTU: u16 = 1500;
    let ipv4 = Ipv4Addr::new(10, 0, 0, 1);
    let netmask = Ipv4Addr::new(255, 255, 255, 0);
    let mut config = tun::Configuration::default();
    config.address(ipv4).netmask(netmask).mtu(MTU).up();

    #[cfg(target_os = "linux")]
    config.platform_config(|config| {
        config.ensure_root_privileges(true);
    });

    #[cfg(target_os = "windows")]
    config.platform_config(|config| {
        config.device_guid(12324323423423434234_u128);
    });

    let mut ipstack_config = ipstack::IpStackConfig::default();
    ipstack_config.mtu(MTU)?;
    let mut ip_stack = ipstack::IpStack::new(ipstack_config, tun::create_as_async(&config)?);

    while let Ok(stream) = ip_stack.accept().await {
        match stream {
            IpStackStream::Tcp(mut tcp) => {
                let mut rhs = TcpStream::connect("1.1.1.1:80").await?;
                tokio::spawn(async move {
                    let _ = tokio::io::copy_bidirectional(&mut tcp, &mut rhs).await;
                    let _ = rhs.shutdown().await;
                    let _ = tcp.shutdown().await;
                });
            }
            IpStackStream::Udp(mut udp) => {
                let addr: SocketAddr = "1.1.1.1:53".parse()?;
                let mut rhs = UdpStream::connect(addr).await?;
                tokio::spawn(async move {
                    let _ = tokio::io::copy_bidirectional(&mut udp, &mut rhs).await;
                    rhs.shutdown();
                    let _ = udp.shutdown().await;
                });
            }
            IpStackStream::UnknownTransport(u) => {
                if u.src_addr().is_ipv4() && u.ip_protocol() == IpNumber::ICMP {
                    let (icmp_header, req_payload) = Icmpv4Header::from_slice(u.payload())?;
                    if let etherparse::Icmpv4Type::EchoRequest(echo) = icmp_header.icmp_type {
                        println!("ICMPv4 echo");
                        let mut resp = Icmpv4Header::new(etherparse::Icmpv4Type::EchoReply(echo));
                        resp.update_checksum(req_payload);
                        let mut payload = resp.to_bytes().to_vec();
                        payload.extend_from_slice(req_payload);
                        u.send(payload)?;
                    } else {
                        println!("ICMPv4");
                    }
                    continue;
                }
                println!("unknown transport - Ip Protocol {:?}", u.ip_protocol());
            }
            IpStackStream::UnknownNetwork(pkt) => {
                println!("unknown transport - {} bytes", pkt.len());
            }
        }
    }
    Ok(())
}