Dummy client to learn the other half of WebSockets

This is mostly a copy of ambiso/bevy_websocket_example:
https://github.com/ambiso/bevy_websocket_example/tree/main

It demonstrates how to hold and use a (Tungstenite) WebSocket in a Bevy
app. I've altered it slightly (and skipped impl'ing the send function)
to fit my own chatroom dummy target.

This is completely useless as a chatroom app, but it's not supposed to
be one. Now I can move on to building the actual Pong game!

Cargo.toml

@@ -1,3 +1,9 @@
 [workspace]
 members = ["client", "server"]
 resolver = "3"
+
+[profile.dev]
+opt-level = 1
+
+[profile.dev.package."*"]
+opt-level = 3

client/Cargo.toml

@@ -4,3 +4,7 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+bevy = { version = "0.17.2", features = ["serialize"] }
+rustls = "0.23.33"
+thiserror = "2.0.17"
+tungstenite = { version = "0.28.0", features = ["rustls-tls-webpki-roots", "rustls"] }

client/src/main.rs

@@ -1,3 +1,204 @@
+use std::{io::ErrorKind, net::TcpStream, time::Duration};
+
+use bevy::{
+    ecs::world::CommandQueue,
+    prelude::*,
+    tasks::{AsyncComputeTaskPool, Task, block_on, futures_lite::future},
+};
+use thiserror::Error;
+use tungstenite::{WebSocket, http::Response, stream::MaybeTlsStream};
+
 fn main() {
-    println!("Hello, world!");
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .add_systems(Startup, setup)
+        .add_systems(
+            Update,
+            (
+                input_handler,
+                setup_connection,
+                handle_tasks,
+                send_info,
+                recv_info,
+            ),
+        )
+        .add_message::<WebSocketConnectionMessage>()
+        .insert_resource(ChatTimer {
+            timer: Timer::new(Duration::from_secs(1), TimerMode::Repeating),
+        })
+        .run();
+}
+
+/// Initialize the scene
+fn setup(
+    mut commands: Commands,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<ColorMaterial>>,
+) {
+    commands.spawn(Camera2d);
+    commands.spawn((
+        Mesh2d(meshes.add(Circle::new(10.0))),
+        MeshMaterial2d(materials.add(Color::srgb(1.0, 0.0, 0.0))),
+        Transform::default(),
+    ));
+}
+
+/// ECS Component to hold the WebSocket. I guess there's going to be a magic
+/// entity that controls the networking.
+#[derive(Component)]
+struct WsClient(
+    (
+        WebSocket<MaybeTlsStream<TcpStream>>,
+        Response<Option<Vec<u8>>>,
+    ),
+);
+
+/// Container component for a bevy task. Specifically, the async Websocket
+/// setup.
+#[derive(Component)]
+struct WsSetupTask(Task<Result<CommandQueue, ConnSetupError>>);
+
+/// Used to signal user input to other systems -- in particular, the notice to
+/// open a connection to the server.
+#[derive(Message)]
+enum WebSocketConnectionMessage {
+    SetupConnection,
+    // TODO: Presumably a TeardownConnection, right?
+}
+
+#[derive(Error, Debug)]
+enum ConnSetupError {
+    #[error("IO")]
+    Io(#[from] std::io::Error),
+    #[error("WebSocket")]
+    WebSocket(#[from] tungstenite::Error),
+}
+
+/// The keyboard input handler (mainly to trigger WS connection)
+fn input_handler(
+    input: Res<ButtonInput<KeyCode>>,
+    mut messages: MessageWriter<WebSocketConnectionMessage>,
+) {
+    if input.just_pressed(KeyCode::Space) {
+        messages.write(WebSocketConnectionMessage::SetupConnection);
+    }
+}
+
+/// The system which establishes the WS connection. It responds to [`WebSocketConnectionMessage`]s.
+///
+/// When a [`WebSocketConnectionMessage::SetupConnection`] message is emitted,
+/// this system responds by creating a new (bevy) [`Task`]. This task is stored
+/// in the component [`WsSetupTask`] which is attached to a new entity.
+///
+/// The closure executed by this task attempts to reach out to a WebSocket URL.
+/// Upon successful connection, the socket is placed in a [`WsClient`]
+/// component and added to the same entity. At the same time, the [`WsSetupTask`]
+/// is removed since the task has now finished.
+///
+/// Monitoring for completion of the task is done by the system [`handle_tasks()`].
+fn setup_connection(
+    mut commands: Commands,
+    mut messages: MessageReader<WebSocketConnectionMessage>,
+) {
+    for msg in messages.read() {
+        match msg {
+            WebSocketConnectionMessage::SetupConnection => {
+                info!("Connecting to server...");
+                let url = "ws://localhost:4000/websocket";
+                let entity = commands.spawn_empty().id();
+                {
+                    let pool = AsyncComputeTaskPool::get();
+                    let task = pool.spawn(async move {
+                        let mut client = tungstenite::connect(url)?;
+                        match client.0.get_mut() {
+                            MaybeTlsStream::Plain(p) => p.set_nonblocking(true)?,
+                            MaybeTlsStream::Rustls(stream_owned) => {
+                                stream_owned.get_mut().set_nonblocking(true)?
+                            }
+                            _ => todo!(),
+                        };
+
+                        info!("Connected!");
+                        // First message is this client's username. I'll hard-code
+                        // a value for this PoC.
+                        client.0.send(tungstenite::Message::Text("Dingus".into()))?;
+                        let mut command_queue = CommandQueue::default();
+
+                        command_queue.push(move |world: &mut World| {
+                            world
+                                .entity_mut(entity)
+                                .insert(WsClient(client))
+                                .remove::<WsSetupTask>();
+                        });
+
+                        Ok(command_queue)
+                    });
+                    commands.entity(entity).insert(WsSetupTask(task));
+                }
+            } // _ => { there are no other variants right now, so this is pretty silly }
+        }
+    }
+}
+
+/// Polls the websocket setup task(s) to check for progress.
+///
+/// If the task has succeeded, it will give back a [`CommandQueue`]. This is
+/// appended to the current [`Commands`] so they are acted upon this tick.
+///
+/// If it has failed, an error is printed to the console.
+///
+/// The task is self-removing, so we don't need to delete the [`WsSetupTask`]
+/// component here.
+fn handle_tasks(mut commands: Commands, mut transform_tasks: Query<&mut WsSetupTask>) {
+    for mut task in &mut transform_tasks {
+        if let Some(result) = block_on(future::poll_once(&mut task.0)) {
+            match result {
+                Ok(mut commands_queue) => {
+                    commands.append(&mut commands_queue);
+                }
+                Err(e) => info!("Connection failed. Err: {e:?}"),
+            }
+        }
+    }
+}
+
+#[derive(Resource)]
+struct ChatTimer {
+    timer: Timer,
+}
+
+/// Unused, left over from example code.
+///
+/// It *would* tick a timer, sending a message to the echo server each time the
+/// timer expires. But I have a chatroom not an echo server, so this bit
+/// doesn't make sense.
+///
+/// If I were to make a full chat client, I would replace this with some kind
+/// of event handler.
+fn send_info(
+    some_data: Query<(&Transform,)>,
+    time: Res<Time>,
+    mut client_entt: Query<(&mut WsClient,)>,
+    mut cfg: ResMut<ChatTimer>,
+) {
+    // cfg.timer.tick(time.delta());
+    // if cfg.timer.just_finished() {
+    //     info!("Sending username to server.");
+    //     for
+    // }
+}
+
+/// Reads & prints all messages from all websockets in [`WsClient`]s.
+///
+/// For a real chat app, this would need to print to the screen somehow. I'd
+/// need a lot of other things, too, and this is supposed to be Pong. So I'm
+/// not going to fix any of that.
+fn recv_info(mut q: Query<&mut WsClient>) {
+    for mut client in q.iter_mut() {
+        match client.0.0.read() {
+            Ok(m) => info!("Received message {m:?}"),
+            Err(tungstenite::Error::Io(e)) if e.kind() == ErrorKind::WouldBlock => { /* ignore */ }
+            Err(e) => warn!("error receiving: {e}"),
+        }
+    }
 }