# app/api/events_store.py — Chain-scoped pub/sub for SSE node-status events
#
# Each SSE connection subscribes with subscribe(chain_id) → Queue.
# Background generation tasks call broadcast(chain_id, event) to push
# node state transitions (pending → generating → ready/error) to all listeners.
from __future__ import annotations

import asyncio
from collections import defaultdict
from typing import Any

# chain_id → list of subscriber queues
_listeners: dict[str, list[asyncio.Queue[Any]]] = defaultdict(list)


def subscribe(chain_id: str) -> asyncio.Queue[Any]:
    """Register a new SSE listener for chain_id. Returns its Queue."""
    q: asyncio.Queue[Any] = asyncio.Queue()
    _listeners[chain_id].append(q)
    return q


def unsubscribe(chain_id: str, q: asyncio.Queue[Any]) -> None:
    """Remove a listener Queue. Safe to call if already removed."""
    try:
        _listeners[chain_id].remove(q)
    except ValueError:
        pass


async def broadcast(chain_id: str, event: dict[str, Any]) -> None:
    """Push event dict to all active listeners for chain_id."""
    for q in list(_listeners.get(chain_id, [])):
        await q.put(event)