Add awareness broadcast to session

src/protocol.ts

@@ -6,10 +6,17 @@ export type ClientMessage =
   | { type: "update"; data: number[] } // yjs update as byte array
   | { type: "awareness"; data: number[] };
 
+export type AwarenessState = {
+  clientId: number;
+  cursor?: { line: number; col: number };
+  selection?: { startLine: number; startCol: number; endLine: number; endCol: number };
+  name?: string;
+};
+
 export type ServerMessage =
   | { type: "sync"; data: number[] } // full yjs state
   | { type: "update"; data: number[] }
-  | { type: "awareness"; data: number[] }
+  | { type: "awareness"; data: AwarenessState }
   | { type: "peers"; count: number }
   | { type: "error"; message: string };
 

src/session.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, test } from "bun:test";
 import * as Y from "yjs";
-import { getOrCreateSession, Session, type WsData } from "./session";
+import { getOrCreateSession, Session, type Client, type WsData } from "./session";
 
 describe("Session", () => {
   test("creates yjs doc on init", () => {
@@ -57,3 +57,26 @@ describe("getOrCreateSession", () => {
     expect(s1).not.toBe(s2);
   });
 });
+
+describe("awareness", () => {
+  test("broadcasts awareness to other clients", () => {
+    const session = new Session("test-room");
+    const sent1: unknown[] = [];
+    const sent2: unknown[] = [];
+
+    const client1 = { ws: { send: (m: string) => sent1.push(JSON.parse(m)) } } as Client;
+    const client2 = { ws: { send: (m: string) => sent2.push(JSON.parse(m)) } } as Client;
+
+    session.join(client1);
+    session.join(client2);
+
+    const awareness = { clientId: 1, cursor: { line: 5, col: 10 } };
+    session.broadcastAwareness(client1, awareness);
+
+    // client1 should NOT receive their own awareness
+    expect(sent1.filter(m => m.type === "awareness")).toHaveLength(0);
+    // client2 should receive it
+    expect(sent2.filter(m => m.type === "awareness")).toHaveLength(1);
+    expect(sent2.find(m => m.type === "awareness")?.data).toEqual(awareness);
+  });
+});

src/session.ts

@@ -1,6 +1,6 @@
 import type { ServerWebSocket } from "bun";
 import * as Y from "yjs";
-import { encode } from "./protocol";
+import { encode, type AwarenessState } from "./protocol";
 
 export interface WsData {
   room: string | null;
@@ -84,6 +84,19 @@ export class Session {
       }
     }
   }
+
+  broadcastAwareness(sender: Client, state: AwarenessState): void {
+    const message = encode({ type: "awareness", data: state });
+    for (const client of this.clients) {
+      if (client !== sender) {
+        try {
+          client.ws.send(message);
+        } catch {
+          // client disconnected, ignore
+        }
+      }
+    }
+  }
 }
 
 // room name -> session