import json
import queue
import threading

_clients = set()
_clients_lock = threading.Lock()


def stream_events():
    q = queue.Queue()
    with _clients_lock:
        _clients.add(q)

    try:
        yield 'data: {"type":"connected"}\n\n'
        while True:
            try:
                payload = q.get(timeout=20)
                yield f"data: {payload}\n\n"
            except queue.Empty:
                yield ": heartbeat\n\n"
    finally:
        with _clients_lock:
            _clients.discard(q)


def broadcast(data):
    payload = json.dumps(data)
    with _clients_lock:
        clients = list(_clients)
    for q in clients:
        q.put_nowait(payload)