use crate::sessionhandler::{PduSender, SessionHandler};
use crate::UnixStream;
use anyhow::Context;
use async_ossl::AsyncSslStream;
use codec::{DecodedPdu, Pdu};
use futures::FutureExt;
use mux::{Mux, MuxNotification};
use smol::prelude::*;
use smol::Async;

#[cfg(unix)]
pub trait AsRawDesc: std::os::unix::io::AsRawFd {}
#[cfg(windows)]
pub trait AsRawDesc: std::os::windows::io::AsRawSocket {}

impl AsRawDesc for UnixStream {}
impl AsRawDesc for AsyncSslStream {}

#[derive(Debug)]
enum Item {
    Notif(MuxNotification),
    WritePdu(DecodedPdu),
    Readable,
}

pub async fn process<T>(stream: T) -> anyhow::Result<()>
where
    T: 'static,
    T: std::io::Read,
    T: std::io::Write,
    T: AsRawDesc,
    T: std::fmt::Debug,
{
    let stream = smol::Async::new(stream)?;
    process_async(stream).await
}

pub async fn process_async<T>(mut stream: Async<T>) -> anyhow::Result<()>
where
    T: 'static,
    T: std::io::Read,
    T: std::io::Write,
    T: std::fmt::Debug,
{
    log::trace!("process_async called");

    let (item_tx, item_rx) = smol::channel::unbounded::<Item>();

    let pdu_sender = PduSender::new({
        let item_tx = item_tx.clone();
        move |pdu| {
            item_tx
                .try_send(Item::WritePdu(pdu))
                .map_err(|e| anyhow::anyhow!("{:?}", e))
        }
    });
    let mut handler = SessionHandler::new(pdu_sender);

    {
        let mux = Mux::get().expect("to be running on gui thread");
        let tx = item_tx.clone();
        mux.subscribe(move |n| tx.try_send(Item::Notif(n)).is_ok());
    }

    loop {
        let rx_msg = item_rx.recv();
        let wait_for_read = stream.readable().map(|_| Ok(Item::Readable));

        match smol::future::or(rx_msg, wait_for_read).await {
            Ok(Item::Readable) => {
                let decoded = Pdu::decode_async(&mut stream).await?;
                handler.process_one(decoded);
            }
            Ok(Item::WritePdu(decoded)) => {
                decoded
                    .pdu
                    .encode_async(&mut stream, decoded.serial)
                    .await?;
                stream.flush().await.context("flushing PDU to client")?;
            }
            Ok(Item::Notif(MuxNotification::PaneOutput(pane_id))) => {
                handler.schedule_pane_push(pane_id);
            }
            Ok(Item::Notif(MuxNotification::Alert { pane_id, alert: _ })) => {
                // FIXME: queue notification to send to client!
                handler.schedule_pane_push(pane_id);
            }
            Ok(Item::Notif(MuxNotification::WindowCreated(_window_id))) => {}
            Ok(Item::Notif(MuxNotification::WindowInvalidated(_window_id))) => {}
            Ok(Item::Notif(MuxNotification::Empty)) => {}
            Err(err) => {
                log::error!("process_async Err {}", err);
                return Ok(());
            }
        }
    }
}