from __future__ import annotations

from typing import Any


def is_thread_event(event: Any) -> tuple[bool, str | None]:
    content = event.source.get("content", {})
    relates_to = content.get("m.relates_to", {})

    if relates_to.get("rel_type") == "m.thread":
        root_event_id = relates_to.get("event_id")
        if root_event_id:
            return True, root_event_id

    return False, None