import asyncio
import json


class EventStream:

    def __init__(self):

        self.subscribers = set()

    # -----------------------------
    # SUBSCRIBE (WebSocket clients)
    # -----------------------------
    def subscribe(self, ws):

        self.subscribers.add(ws)

    def unsubscribe(self, ws):

        self.subscribers.discard(ws)

    # -----------------------------
    # EMIT EVENT (REALTIME FANOUT)
    # -----------------------------
    async def emit(self, event_type, payload):

        message = json.dumps({
            "type": event_type,
            "data": payload
        })

        dead = set()

        for ws in self.subscribers:

            try:
                await ws.send(message)
            except Exception:
                dead.add(ws)

        for ws in dead:
            self.subscribers.discard(ws)