"""Liveness: a background task touches a file while the event loop runs; the Docker healthcheck checks its age.

A stuck loop stops touching the file, so the container turns unhealthy even though the process is still up.
`python -m app.health` exits 0 when healthy, 1 otherwise.
"""

import asyncio
import sys
import time
from pathlib import Path

from app.config import RuntimeSettings


async def heartbeat(path: Path, interval: float) -> None:
    while True:
        await asyncio.to_thread(path.touch)
        await asyncio.sleep(interval)


def is_alive(path: Path, max_age: float, now: float | None = None) -> bool:
    try:
        age = (time.time() if now is None else now) - path.stat().st_mtime
    except FileNotFoundError:
        return False
    return age <= max_age


def main() -> None:
    rt = RuntimeSettings()
    sys.exit(0 if is_alive(rt.heartbeat_file, rt.heartbeat_max_age) else 1)


if __name__ == "__main__":
    main()