use rs_tcp::*;
use std::{
    collections::{hash_map::Entry, HashMap},
    io,
};

fn main() -> io::Result<()> {
    let mut nic = tun_tap::Iface::without_packet_info("mytun0", tun_tap::Mode::Tun)?;
    let mut buffer = vec![0; 1500];
    // 保存所有连接对应的状态
    let mut connections: HashMap<Quad, Connection> = HashMap::new();

    loop {
        let nbytes = nic.recv(&mut buffer).unwrap();
        // 忽略非TCP数据包
        match etherparse::Ipv4HeaderSlice::from_slice(&buffer) {
            Ok(iph) => {
                let src = iph.source_addr();
                let dst = iph.destination_addr();
                let proto = iph.protocol();
                if proto != etherparse::IpNumber(0x06) {
                    continue;
                }
                match etherparse::TcpHeaderSlice::from_slice(&buffer[iph.slice().len()..nbytes]) {
                    Ok(tcph) => {
                        let payload_offset = iph.slice().len() + tcph.slice().len();
                        let mut payload = &buffer[payload_offset..nbytes];
                        
                        let recv_quad = Quad {
                            src: (src, tcph.source_port()),
                            dst: (dst, tcph.destination_port()),
                        };
                        // 这里我们需要处理接收到的Tcp数据包
                        match connections.entry(recv_quad) {
                            Entry::Occupied(mut occupied_entry) => {
                                // 已经存在的连接
                                occupied_entry.get_mut().on_packet(iph, tcph, &payload);
                            },
                            Entry::Vacant(vacant_entry) => {
                                eprintln!(
                                    "{}:{} -> {}:{} first handpacket syn: {}, seq: {}",
                                    src,
                                    tcph.source_port(),
                                    dst,
                                    tcph.destination_port(),
                                    tcph.syn(),
                                    tcph.sequence_number()
                                );
                                // 第一次接受的包
                                if let Some(c) = Connection::accept(&mut nic, iph, tcph)?{
                                    vacant_entry.insert(c);
                                }
                            },
                        }
                    }
                    Err(e) => {
                        // 这不是一个TCP包 但是协议是TCP
                        eprintln!("ignoring weird packet: {:?}", e)
                    }
                }
            }
            Err(_) => {
                // 非IP标准包 忽略
                continue;
            }
        };
    }
    Ok(())
}