chatapp

backend/.gitignore

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+/target

backend/Cargo.toml

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+[package]
+name = "backend"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+futures-util = "0.3.31"
+rocket = { version = "0.5.1", features = ["json"] }
+rocket_db_pools = { version = "0.2.0", features = ["sqlx_sqlite"] }
+serde = { version = "1.0.228", features = ["derive"] }
+tokio = { version = "1.47.1", features = ["full"] }

backend/Rocket.toml

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+[debug]
+port = 8001

backend/src/main.rs

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+// src/main.rs
+#[macro_use]
+extern crate rocket;
+
+use rocket::response::stream::{Event, EventStream};
+use rocket::serde::json::Json;
+use rocket::{Build, Rocket};
+use serde::Deserialize;
+use std::sync::Arc;
+use tokio::sync::broadcast;
+
+/// ---------- shared broadcaster ----------
+struct ChatBroadcaster {
+    sender: broadcast::Sender<String>,
+}
+
+impl ChatBroadcaster {
+    fn new(buffer_size: usize) -> Self {
+        let (sender, _rx) = broadcast::channel::<String>(buffer_size);
+        Self { sender }
+    }
+
+    async fn publish(&self, msg: String) {
+        let _ = self.sender.send(msg);
+    }
+
+    fn subscribe(&self) -> broadcast::Receiver<String> {
+        self.sender.subscribe()
+    }
+}
+
+/// ---------- Rocket routes ----------
+#[derive(Debug, Deserialize)]
+struct ChatMsg {
+    text: String,
+}
+
+#[post("/chat", format = "json", data = "<msg>")]
+async fn post_message(
+    msg: Json<ChatMsg>,
+    chat: &rocket::State<Arc<ChatBroadcaster>>,
+) -> &'static str {
+    let text = msg.text.clone();
+    chat.publish(text).await;
+    "Message sent"
+}
+
+#[get("/events")]
+async fn event_stream(chat: &rocket::State<Arc<ChatBroadcaster>>) -> EventStream![] {
+    let mut rx = chat.subscribe();
+
+    EventStream! {
+        loop {
+            match rx.recv().await {
+                Ok(msg) => yield Event::data(msg),
+                Err(broadcast::error::RecvError::Lagged(_)) => {
+                    yield Event::comment("lagged");
+                }
+                Err(broadcast::error::RecvError::Closed) => break,
+            }
+        }
+    }
+}
+
+/// ---------- launch ----------
+#[launch]
+fn rocket() -> Rocket<Build> {
+    let chat = Arc::new(ChatBroadcaster::new(32));
+
+    rocket::build()
+        .manage(chat)
+        .mount("/", routes![post_message, event_stream])
+}