use std::collections::HashMap;
use std::net::SocketAddr;
use tokio::io::copy;
use tokio::net::{TcpListener, TcpStream};

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let filename = std::env::args()
        .next()
        .unwrap_or_else(|| "config.toml".to_string());

    let contents = std::fs::read_to_string(filename)?;

    let mut ports: HashMap<u16, SocketAddr> = toml::from_str(&contents)?;

    let listener = TcpListener::bind("0.0.0.0:8000").await?;

    loop {
        let (stream, addr) = listener.accept().await?;
        let to_addr = match ports.get(&addr.port()) {
            Some(v) => *v,
            None => continue,
        };
        let to_stream = TcpStream::connect(to_addr).await?; // TODO: remove this placeholder

        tokio::spawn(async move {
            proxy(stream, to_stream).await?;

            Ok::<(), anyhow::Error>(())
        });
    }
}

async fn proxy(left: TcpStream, right: TcpStream) -> anyhow::Result<()> {
    let (mut left_read, mut left_write) = left.into_split();
    let (mut right_read, mut right_write) = right.into_split();

    tokio::select! {
        r = copy(&mut left_read, &mut right_write) => r?,
        r = copy(&mut right_read, &mut left_write) => r?
    };

    Ok(())
}