feat: add WebSocket announce manager

Made-with: Cursor

tests/test_websocket.py

@@ -0,0 +1,45 @@
+import pytest
+from ntr_fetcher.websocket import AnnounceManager
+
+
+@pytest.fixture
+def manager():
+    return AnnounceManager()
+
+
+def test_no_subscribers_initially(manager):
+    assert manager.subscriber_count == 0
+
+
+@pytest.mark.asyncio
+async def test_subscribe_and_broadcast(manager):
+    received = []
+
+    class FakeWS:
+        async def send_json(self, data):
+            received.append(data)
+
+    ws = FakeWS()
+    manager.add_subscriber(ws)
+    assert manager.subscriber_count == 1
+
+    await manager.broadcast({"type": "announce", "message": "Now Playing: Song #1"})
+    assert len(received) == 1
+    assert received[0]["message"] == "Now Playing: Song #1"
+
+    manager.remove_subscriber(ws)
+    assert manager.subscriber_count == 0
+
+
+@pytest.mark.asyncio
+async def test_broadcast_skips_dead_connections(manager):
+    class DeadWS:
+        async def send_json(self, data):
+            raise Exception("connection closed")
+
+    ws = DeadWS()
+    manager.add_subscriber(ws)
+    assert manager.subscriber_count == 1
+
+    await manager.broadcast({"type": "announce", "message": "test"})
+    assert manager.subscriber_count == 0