//! Testing against pppd:
//!
//!     echo myuser $(hostname) mypass 192.168.7.10 >> /etc/ppp/pap-secrets
//!     socat -v -x PTY,link=pty1,rawer PTY,link=pty2,rawer
//!     sudo pppd $PWD/pty1 115200 192.168.7.1: ms-dns 8.8.4.4 ms-dns 8.8.8.8 nodetach debug local persist silent noproxyarp
//!     RUST_LOG=trace cargo run --bin net_ppp -- --device pty2
//!     ping 192.168.7.10
//!     nc 192.168.7.10 1234

#![feature(type_alias_impl_trait)]
#![feature(async_fn_in_trait)]

#[path = "../serial_port.rs"]
mod serial_port;

use async_io::Async;
use clap::Parser;
use embassy_executor::{Executor, Spawner};
use embassy_net::tcp::TcpSocket;
use embassy_net::{Config, ConfigV4, Ipv4Address, Ipv4Cidr, Stack, StackResources};
use embassy_net_ppp::Runner;
use embedded_io_async::Write;
use futures::io::BufReader;
use heapless::Vec;
use log::*;
use nix::sys::termios;
use rand_core::{OsRng, RngCore};
use static_cell::{make_static, StaticCell};

use crate::serial_port::SerialPort;

#[derive(Parser)]
#[clap(version = "1.0")]
struct Opts {
    /// Serial port device name
    #[clap(short, long)]
    device: String,
}

#[embassy_executor::task]
async fn net_task(stack: &'static Stack<embassy_net_ppp::Device<'static>>) -> ! {
    stack.run().await
}

#[embassy_executor::task]
async fn ppp_task(
    stack: &'static Stack<embassy_net_ppp::Device<'static>>,
    mut runner: Runner<'static>,
    port: SerialPort,
) -> ! {
    let port = Async::new(port).unwrap();
    let port = BufReader::new(port);
    let port = adapter::FromFutures::new(port);

    let config = embassy_net_ppp::Config {
        username: b"myuser",
        password: b"mypass",
    };

    runner
        .run(port, config, |ipv4| {
            let Some(addr) = ipv4.address else {
                warn!("PPP did not provide an IP address.");
                return;
            };
            let mut dns_servers = Vec::new();
            for s in ipv4.dns_servers.iter().flatten() {
                let _ = dns_servers.push(Ipv4Address::from_bytes(&s.0));
            }
            let config = ConfigV4::Static(embassy_net::StaticConfigV4 {
                address: Ipv4Cidr::new(Ipv4Address::from_bytes(&addr.0), 0),
                gateway: None,
                dns_servers,
            });
            stack.set_config_v4(config);
        })
        .await
        .unwrap();
    unreachable!()
}

#[embassy_executor::task]
async fn main_task(spawner: Spawner) {
    let opts: Opts = Opts::parse();

    // Open serial port
    let baudrate = termios::BaudRate::B115200;
    let port = SerialPort::new(opts.device.as_str(), baudrate).unwrap();

    // Init network device
    let state = make_static!(embassy_net_ppp::State::<4, 4>::new());
    let (device, runner) = embassy_net_ppp::new(state);

    // Generate random seed
    let mut seed = [0; 8];
    OsRng.fill_bytes(&mut seed);
    let seed = u64::from_le_bytes(seed);

    // Init network stack
    let stack = &*make_static!(Stack::new(
        device,
        Config::default(), // don't configure IP yet
        make_static!(StackResources::<3>::new()),
        seed
    ));

    // Launch network task
    spawner.spawn(net_task(stack)).unwrap();
    spawner.spawn(ppp_task(stack, runner, port)).unwrap();

    // Then we can use it!
    let mut rx_buffer = [0; 4096];
    let mut tx_buffer = [0; 4096];
    let mut buf = [0; 4096];

    loop {
        let mut socket = TcpSocket::new(stack, &mut rx_buffer, &mut tx_buffer);
        socket.set_timeout(Some(embassy_time::Duration::from_secs(10)));

        info!("Listening on TCP:1234...");
        if let Err(e) = socket.accept(1234).await {
            warn!("accept error: {:?}", e);
            continue;
        }

        info!("Received connection from {:?}", socket.remote_endpoint());

        loop {
            let n = match socket.read(&mut buf).await {
                Ok(0) => {
                    warn!("read EOF");
                    break;
                }
                Ok(n) => n,
                Err(e) => {
                    warn!("read error: {:?}", e);
                    break;
                }
            };

            info!("rxd {:02x?}", &buf[..n]);

            match socket.write_all(&buf[..n]).await {
                Ok(()) => {}
                Err(e) => {
                    warn!("write error: {:?}", e);
                    break;
                }
            };
        }
    }
}

static EXECUTOR: StaticCell<Executor> = StaticCell::new();

fn main() {
    env_logger::builder()
        .filter_level(log::LevelFilter::Trace)
        .filter_module("polling", log::LevelFilter::Info)
        .filter_module("async_io", log::LevelFilter::Info)
        .format_timestamp_nanos()
        .init();

    let executor = EXECUTOR.init(Executor::new());
    executor.run(|spawner| {
        spawner.spawn(main_task(spawner)).unwrap();
    });
}

mod adapter {
    use core::future::poll_fn;
    use core::pin::Pin;

    use futures::AsyncBufReadExt;

    /// Adapter from `futures::io` traits.
    #[derive(Clone)]
    pub struct FromFutures<T: ?Sized> {
        inner: T,
    }

    impl<T> FromFutures<T> {
        /// Create a new adapter.
        pub fn new(inner: T) -> Self {
            Self { inner }
        }
    }

    impl<T: ?Sized> embedded_io_async::ErrorType for FromFutures<T> {
        type Error = std::io::Error;
    }

    impl<T: futures::io::AsyncRead + Unpin + ?Sized> embedded_io_async::Read for FromFutures<T> {
        async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
            poll_fn(|cx| Pin::new(&mut self.inner).poll_read(cx, buf)).await
        }
    }

    impl<T: futures::io::AsyncBufRead + Unpin + ?Sized> embedded_io_async::BufRead for FromFutures<T> {
        async fn fill_buf(&mut self) -> Result<&[u8], Self::Error> {
            self.inner.fill_buf().await
        }

        fn consume(&mut self, amt: usize) {
            Pin::new(&mut self.inner).consume(amt)
        }
    }

    impl<T: futures::io::AsyncWrite + Unpin + ?Sized> embedded_io_async::Write for FromFutures<T> {
        async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
            poll_fn(|cx| Pin::new(&mut self.inner).poll_write(cx, buf)).await
        }

        async fn flush(&mut self) -> Result<(), Self::Error> {
            poll_fn(|cx| Pin::new(&mut self.inner).poll_flush(cx)).await
        }
    }
}