feat(sounds): add stream_watch data-channel protocol helpers

packages/web/src/utils/streamWatchProtocol.test.ts

@@ -0,0 +1,36 @@
+import { describe, it, expect } from 'vitest';
+import {
+  encodeStreamWatch,
+  parseStreamWatch,
+  isStreamWatchPayload,
+} from './streamWatchProtocol';
+
+describe('streamWatchProtocol', () => {
+  it('round-trips an encoded payload', () => {
+    const payload = { type: 'stream_watch' as const, target: 'user-1', watching: true };
+    const encoded = encodeStreamWatch(payload);
+    expect(encoded).toBeDefined();
+    expect(encoded.length).toBeGreaterThan(0);
+    const parsed = parseStreamWatch(encoded);
+    expect(parsed).toEqual(payload);
+  });
+
+  it('parseStreamWatch returns null on invalid JSON', () => {
+    const bad = new TextEncoder().encode('not json');
+    expect(parseStreamWatch(bad)).toBeNull();
+  });
+
+  it('parseStreamWatch returns null on wrong message type', () => {
+    const other = new TextEncoder().encode(JSON.stringify({ type: 'deafen', deafened: true }));
+    expect(parseStreamWatch(other)).toBeNull();
+  });
+
+  it('isStreamWatchPayload validates shape', () => {
+    expect(isStreamWatchPayload({ type: 'stream_watch', target: 'u', watching: true })).toBe(true);
+    expect(isStreamWatchPayload({ type: 'stream_watch', target: 'u', watching: 'yes' })).toBe(false);
+    expect(isStreamWatchPayload({ type: 'stream_watch', watching: true })).toBe(false);
+    expect(isStreamWatchPayload({ type: 'other', target: 'u', watching: true })).toBe(false);
+    expect(isStreamWatchPayload(null)).toBe(false);
+    expect(isStreamWatchPayload('string')).toBe(false);
+  });
+});

packages/web/src/utils/streamWatchProtocol.ts

@@ -0,0 +1,35 @@
+/**
+ * Wire format for the LiveKit data-channel ping that announces a viewer
+ * has begun (or stopped) watching a screen share. Sent only from explicit
+ * user-action sites (StreamTile click handlers); receiver maintains the
+ * streamer-side watcher set.
+ */
+export interface StreamWatchPayload {
+  type: 'stream_watch';
+  target: string;
+  watching: boolean;
+}
+
+export function encodeStreamWatch(payload: StreamWatchPayload): Uint8Array {
+  return new TextEncoder().encode(JSON.stringify(payload));
+}
+
+export function isStreamWatchPayload(value: unknown): value is StreamWatchPayload {
+  if (typeof value !== 'object' || value === null) return false;
+  const v = value as Record<string, unknown>;
+  return (
+    v.type === 'stream_watch' &&
+    typeof v.target === 'string' &&
+    typeof v.watching === 'boolean'
+  );
+}
+
+export function parseStreamWatch(payload: Uint8Array): StreamWatchPayload | null {
+  try {
+    const text = new TextDecoder().decode(payload);
+    const parsed: unknown = JSON.parse(text);
+    return isStreamWatchPayload(parsed) ? parsed : null;
+  } catch {
+    return null;
+  }
+}