//! QUIC server accept loop.

use std::{net::SocketAddr, time::Duration};

use s2n_quic::{Connection, Server, provider::limits::Limits};
use tokio::sync::mpsc::UnboundedSender;

use crate::{
    PeerEvent,
    config::{CERT_PEM, KEY_PEM},
    context::PeerCtx,
    events,
    services::{
        advertise::{monitor_mdns_events, start_mdns_advertiser},
        stream::handle_peer_stream,
    },
};

/// Runs the QUIC server and mDNS advertiser.
pub async fn run_server_component(
    addr: SocketAddr,
    ctx: PeerCtx,
    tx_notify_ui: UnboundedSender<PeerEvent>,
) -> eyre::Result<()> {
    let limits = Limits::default()
        .with_max_handshake_duration(Duration::from_secs(3))?
        .with_max_idle_timeout(Duration::from_secs(3))?;

    let mut server = Server::builder()
        .with_tls((CERT_PEM, KEY_PEM))?
        .with_io(addr)?
        .with_limits(limits)?
        .start()?;

    let server_addr = server.local_addr()?;
    log::info!("Peer server listening on {server_addr}");

    let mdns_advertiser = start_mdns_advertiser(&ctx, server_addr).await?;
    let mdns_monitor = mdns_advertiser.monitor.clone();
    let mdns_shutdown = ctx.shutdown.clone();
    ctx.task_tracker.spawn(async move {
        monitor_mdns_events(mdns_monitor, mdns_shutdown).await;
    });
    let ready_addr =
        (*ctx.local_peer_addr.read().await).unwrap_or_else(|| direct_connect_addr(server_addr));
    let _mdns_advertiser = mdns_advertiser;

    events::send(
        &tx_notify_ui,
        PeerEvent::LocalPeerReady {
            peer_id: ctx.peer_id.as_ref().clone(),
            addr: ready_addr,
        },
    );

    loop {
        let connection = tokio::select! {
            () = ctx.shutdown.cancelled() => return Ok(()),
            connection = server.accept() => connection,
        };

        let Some(connection) = connection else {
            eyre::bail!("QUIC server accept loop ended unexpectedly");
        };

        let ctx = ctx.clone();
        let tx_notify_ui = tx_notify_ui.clone();
        let task_tracker = ctx.task_tracker.clone();

        task_tracker.spawn(async move {
            if let Err(err) = handle_peer_connection(connection, ctx, tx_notify_ui).await {
                log::error!("Peer connection error: {err}");
            }
        });
    }
}

fn direct_connect_addr(server_addr: SocketAddr) -> SocketAddr {
    if server_addr.ip().is_unspecified() {
        return SocketAddr::from(([127, 0, 0, 1], server_addr.port()));
    }
    server_addr
}

async fn handle_peer_connection(
    mut connection: Connection,
    ctx: PeerCtx,
    tx_notify_ui: UnboundedSender<PeerEvent>,
) -> eyre::Result<()> {
    let remote_addr = connection.remote_addr()?;
    log::info!("{remote_addr} peer connected");
    events::send(&tx_notify_ui, PeerEvent::PeerConnected(remote_addr));

    loop {
        let stream = tokio::select! {
            () = ctx.shutdown.cancelled() => break,
            stream = connection.accept_bidirectional_stream() => stream,
        };

        let Some(stream) = stream? else {
            break;
        };

        let ctx = ctx.clone();
        let task_tracker = ctx.task_tracker.clone();
        task_tracker.spawn(async move {
            if let Err(err) = handle_peer_stream(stream, ctx, Some(remote_addr)).await {
                log::error!("{remote_addr:?} peer stream error: {err}");
            }
        });
    }

    events::send(&tx_notify_ui, PeerEvent::PeerDisconnected(remote_addr));
    Ok(())
}