"""
Ops/health metrics exported as Prometheus metrics (4B Ops).

These are low-frequency filesystem-based metrics (safe on scrape).
"""

from __future__ import annotations

from datetime import datetime
from pathlib import Path

from app.config import get_settings


settings = get_settings()

try:
    from prometheus_client import Gauge
except Exception:  # pragma: no cover
    Gauge = None  # type: ignore


if Gauge is not None:
    db_backups_enabled = Gauge("pounce_db_backups_enabled", "DB backups enabled (1/0)")
    db_backup_latest_unixtime = Gauge("pounce_db_backup_latest_unixtime", "Unix time of latest backup file (0 if none)")
    db_backup_latest_age_seconds = Gauge("pounce_db_backup_latest_age_seconds", "Age of latest backup file (seconds)")
else:  # pragma: no cover
    db_backups_enabled = None  # type: ignore
    db_backup_latest_unixtime = None  # type: ignore
    db_backup_latest_age_seconds = None  # type: ignore


def _backup_root() -> Path:
    root = Path(settings.backup_dir)
    if not root.is_absolute():
        root = (Path.cwd() / root).resolve()
    return root


async def update_prometheus_ops_metrics() -> None:
    if Gauge is None:
        return

    db_backups_enabled.set(1 if settings.enable_db_backups else 0)

    root = _backup_root()
    if not root.exists() or not root.is_dir():
        db_backup_latest_unixtime.set(0)
        db_backup_latest_age_seconds.set(0)
        return

    files = [p for p in root.glob("*") if p.is_file()]
    if not files:
        db_backup_latest_unixtime.set(0)
        db_backup_latest_age_seconds.set(0)
        return

    latest = max(files, key=lambda p: p.stat().st_mtime)
    mtime = float(latest.stat().st_mtime)
    now = datetime.utcnow().timestamp()
    age = max(0.0, now - mtime)

    db_backup_latest_unixtime.set(mtime)
    db_backup_latest_age_seconds.set(age)