Move chat app example to README

Author: uellenberg

…ects/030_chat_app_backend/user/README.md …_projects/030_chat_app_backend/README.mdsections/01_rust_projects/030_chat_app_backend/user/README.md renamed to sections/01_rust_projects/030_chat_app_backend/README.md sections/01_rust_projects/030_chat_app_backend/user/README.md renamed to sections/01_rust_projects/030_chat_app_backend/README.md

@@ -449,9 +449,107 @@ Here's some important information to get you started:
 This project involves a lot of concepts that are probably new to you, and you
 probably will get stuck somewhere along the way. That's okay! Try to get as far
 as you can, and consult resources when you get stuck. Once you've given it a
-good try,
-[click here to open the completed example code](../example/src/main.rs).
+good try, you can compare your code to the example below.
 
 Good luck! If you get stuck along the way, look online for other resources or
 examples. The axum repository has some great examples showcasing different
 features, not just WebSockets.
+
+## Example Code
+
+Here's an example implementation of this project. You can use it as a reference
+for your own code, but please give the project a try before consulting the
+example! The best way to learn is by spending some time struggling with the
+problem.
+
+```rust
+use axum::extract::{
+    ws::{Message, WebSocket},
+    State, WebSocketUpgrade,
+};
+use axum::response::IntoResponse;
+use axum::routing::any;
+use axum::Router;
+use std::sync::{Arc, Mutex};
+use tokio::net::TcpListener;
+use tokio::sync::broadcast;
+use tower_http::services::ServeDir;
+
+#[derive(Clone)]
+struct ServerState {
+    /// The list of every message that this server has received.
+    message_history: Arc<Mutex<Vec<String>>>,
+    /// A channel to share messages between all connected clients.
+    message_channel: broadcast::Sender<String>,
+}
+
+#[tokio::main]
+async fn main() {
+    let message_history = Arc::new(Mutex::new(Vec::new()));
+    let (tx, _rx) = broadcast::channel(32);
+
+    let state = ServerState {
+        // This is syntax sugar for message_history: message_history.
+        message_history,
+        message_channel: tx,
+    };
+
+    let app = Router::new()
+        .route("/socket", any(ws_handler))
+        .fallback_service(ServeDir::new("public"))
+        .with_state(state);
+
+    let listener = TcpListener::bind("localhost:3000").await.unwrap();
+    axum::serve(listener, app).await.unwrap();
+}
+
+async fn ws_handler(ws: WebSocketUpgrade, State(state): State<ServerState>) -> impl IntoResponse {
+    ws.on_upgrade(move |socket| handle_socket(socket, state))
+}
+
+async fn handle_socket(mut socket: WebSocket, state: ServerState) {
+    // Send over every message to the client.
+    let messages = state.message_history.lock().unwrap().clone();
+
+    for msg in messages {
+        if let Err(err) = socket.send(Message::text(msg)).await {
+            eprintln!("Error while sending initial data: {err:?}");
+            return;
+        }
+    }
+
+    let mut recv = state.message_channel.subscribe();
+
+    // Receive loop.
+    loop {
+        tokio::select! {
+            val = recv.recv() => {
+                let Ok(val) = val else {
+                    break;
+                };
+
+                if let Err(err) = socket.send(Message::text(val)).await {
+                    eprintln!("Error while sending message to socket: {err:?}");
+                    return;
+                }
+            }
+            val = socket.recv() => {
+                let Some(Ok(val)) = val else {
+                    break;
+                };
+
+                // Only handle text messages.
+                if let Message::Text(text) = val {
+                    // Send message to all connected clients.
+                    if state.message_channel.send(text.to_string()).is_err() {
+                        break;
+                    }
+
+                    // Save message to history.
+                    state.message_history.lock().unwrap().push(text.to_string());
+                }
+            }
+        }
+    }
+}
+```

sections/01_rust_projects/030_chat_app_backend/config.json

@@ -1,23 +1,7 @@
 {
-    "root": "/user",
     "defaultFile": "src/main.rs",
     "source": "https://github.com/Cratecode/rust/tree/master/sections/01_rust_projects/030_chat_app_backend",
     "showShareButton": true,
     "outputView": "console",
-    "outputViews": ["console", "web"],
-    "run": {
-        "command": {
-            "value": "cargo run --manifest-path ~/project/user/Cargo.toml\n"
-        }
-    },
-    "commands": {
-        "0": {
-            "cmd": "cargo build --manifest-path ~/project/user/Cargo.toml",
-            "mode": "once"
-        },
-        "1": {
-            "cmd": "echo \"cd /home/user/project/user\" >> /home/user/.bashrc",
-            "mode": "once"
-        }
-    }
+    "outputViews": ["console", "web"]
 }