"""Realtime synchronization for chat access changes.

The channel layer is an integration boundary: model signals publish only a
small access invalidation event, while the consumer owns group membership.
"""

from __future__ import annotations

import logging

from asgiref.sync import async_to_sync
from channels.layers import get_channel_layer
from django.db import transaction

logger = logging.getLogger(__name__)


def schedule_chat_access_changed(
    *,
    chat_id: int,
    user_id: int,
    membership_active: bool,
) -> None:
    """Notify every live session after the membership transaction commits."""

    def _send() -> None:
        channel_layer = get_channel_layer()
        if channel_layer is None:
            logger.warning(
                "Chat access update skipped because channel layer is unavailable",
                extra={
                    "event": "chat.realtime_access.channel_layer_unavailable",
                    "chat_id": chat_id,
                    "participant_id": user_id,
                },
            )
            return

        try:
            async_to_sync(channel_layer.group_send)(
                f"user_{user_id}",
                {
                    "type": "chat_access_changed",
                    "chat_id": chat_id,
                    "membership_active": membership_active,
                },
            )
        except Exception as error:
            logger.exception(
                "Chat access realtime update failed",
                extra={
                    "event": "chat.realtime_access.send_failed",
                    "chat_id": chat_id,
                    "participant_id": user_id,
                    "membership_active": membership_active,
                    "error_type": type(error).__name__,
                },
            )

    transaction.on_commit(_send)