urus/examples/channels_chat.rs

//! Phoenix-style channels (v0.6): join/leave/event protocol over the
//! v0.4 WebSocket duplex, pubsub underneath, phoenix V2 JSON on the
//! wire.
//!
//!   cargo run --example channels_chat --features phoenix
//!   websocat ws://127.0.0.1:8080/socket          (run two of these)
//!   ["1","1","room:lobby","phx_join",{"name":"alice"}]
//!   ["1","2","room:lobby","shout",{"text":"hi"}]
//!   ["1","3","room:lobby","phx_leave",{}]
//!
//! The shapes this demonstrates:
//!
//! - **One `ChannelHub` for the whole app**, built lazily on the first
//!   connection via the NON-static `Arc<OnceLock<...>>` pattern (the
//!   hub spawns the pubsub table; same in-runtime + shutdown laws as
//!   `examples/ws_chat.rs`, see the docs there).
//!
//! - **A channel per joined topic, not per socket.** `Room` never sees
//!   frames, refs, or the transport heartbeat — the conn-side handler
//!   answers heartbeats, routes `phx_join`, and the per-join channel
//!   actor (linked to the connection) runs the callbacks sequentially.
//!
//! - **`Json<T>` is the phoenix codec's opt-in newtype.** The
//!   `"channels"` core is wire-neutral (`Encode`/`Decode`, zero deps);
//!   `Json<Value>` here buys phoenix.js V2 interop. Typed payloads work
//!   the same way: `Json<MyPayload>` for any serde type.
//!
//! - **`session::*` topics persist across reconnects** (opt-in via
//!   `channel_session`): drop a websocat mid-room, reconnect and rejoin
//!   within 30s, and the broadcasts you missed drain to you in order —
//!   the buffer holds the relay path's own `Arc`s, nothing is copied.
//!   The session is keyed by the `"name"` in the join payload.

use std::sync::{Arc, OnceLock};

use serde_json::{json, Value};
use urus::channels::phoenix::Json;
use urus::{
    serve_with_shutdown, shutdown_handle, Channel, ChannelHub, ChannelSession, ChannelSocket,
    Config, Conn, Next, Pipeline, PrefixRouter, Router, Status,
};

type P = Json<Value>;

/// One chat room. State lives across callbacks (and, for `session:*`
/// topics, across transports).
#[derive(Default)]
struct Room {
    name: String,
    msgs_seen: u64,
}

impl Channel<P> for Room {
    fn join(&mut self, topic: &str, payload: P, _s: &ChannelSocket<P>) -> Result<P, P> {
        // Re-entrant by contract for session topics: a rejoin lands
        // here again on the same instance — re-auth, then ack.
        self.name = payload.0["name"].as_str().unwrap_or("anon").to_string();
        Ok(Json(json!({ "joined": topic, "as": self.name, "seen": self.msgs_seen })))
    }

    fn handle_in(&mut self, event: &str, payload: P, s: &ChannelSocket<P>) {
        match event {
            "shout" => {
                self.msgs_seen += 1;
                s.broadcast("shouted", Json(json!({ "from": self.name, "msg": payload.0 })));
            }
            _ => s.reply(Status::Ok, Json(json!({ "echo": event }))),
        }
    }

    fn terminate(&mut self) {
        println!("room channel for {:?} is over", self.name);
    }
}

/// Session config for `session:*`: the join payload's `"name"` is the
/// session token. Defaults: 128 buffered broadcasts, 30s TTL.
struct BySessionName;

impl ChannelSession<P> for BySessionName {
    type Key = String;
    fn session_key(topic: &str, join_payload: &P) -> String {
        format!("{topic}/{}", join_payload.0["name"].as_str().unwrap_or("anon"))
    }
}

fn main() {
    let hub: Arc<OnceLock<ChannelHub<P>>> = Arc::new(OnceLock::new());

    let router = Router::new().get("/socket", move |c: Conn, _n: Next| {
        // Hub construction is in-runtime only (it spawns the pubsub
        // table and, for session patterns, their registries); the
        // non-static cell is what lets shutdown drain them all.
        let hub = hub.get_or_init(|| {
            ChannelHub::new(
                PrefixRouter::new()
                    .channel_default::<Room>("room:*")
                    .channel_session::<BySessionName>("session:*", |_: &str| {
                        Box::new(Room::default()) as Box<dyn Channel<P>>
                    }),
            )
        });
        hub.upgrade(c)
    });

    let (handle, signal) = shutdown_handle();
    std::thread::spawn(move || {
        println!("channels_chat on ws://127.0.0.1:8080/socket — press Enter to shut down");
        let mut line = String::new();
        let _ = std::io::stdin().read_line(&mut line);
        handle.shutdown();
    });

    serve_with_shutdown(
        Config::new("0.0.0.0:8080".parse().unwrap()),
        smarm::Config::default(),
        Pipeline::new().plug(router),
        signal,
    )
        .unwrap();
    println!("channels_chat: drained, bye");
}