"""Daily APScheduler cron for basic DB maintenance (targeted VACUUM ANALYZE).

One ScheduledJob (services/scheduler.py). Scheduled for 04:00 UTC by default
— after the 03:30 trash purge — so it collects the dead tuples that night's
delete sweeps leave behind.

Two things are operator-tunable from the admin Settings card:
  - db_maintenance_enabled ("true"/"false") — checked at fire time, so toggling
    it needs no reschedule.
  - db_maintenance_hour ("0".."23", UTC) — the cron hour. Changing it calls
    reschedule_db_maintenance() so the live job moves without a restart.
"""
from __future__ import annotations

import asyncio
import logging

from apscheduler.triggers.cron import CronTrigger

from scribe.services.scheduler import ScheduledJob
from scribe.services.settings import get_admin_setting

logger = logging.getLogger(__name__)

_JOB_ID = "db_maintenance_vacuum"
_DEFAULT_HOUR = 4


async def get_maintenance_hour() -> int:
    """The configured run-hour (UTC, 0–23), clamped; default 04:00."""
    raw = await get_admin_setting("db_maintenance_hour", str(_DEFAULT_HOUR))
    try:
        hour = int(raw)
    except (TypeError, ValueError):
        return _DEFAULT_HOUR
    return hour if 0 <= hour <= 23 else _DEFAULT_HOUR


async def is_maintenance_enabled() -> bool:
    """Whether the scheduled run is enabled (default on)."""
    return (await get_admin_setting("db_maintenance_enabled", "true")) != "false"


async def _run_maintenance() -> None:
    if not await is_maintenance_enabled():
        logger.debug("db maintenance: disabled, skipping scheduled run")
        return
    from scribe.services.db_maintenance import run_maintenance
    await run_maintenance()


_JOB = ScheduledJob(_JOB_ID, _run_maintenance, label="DB maintenance")


def _trigger(hour: int) -> CronTrigger:
    hour = hour if 0 <= hour <= 23 else _DEFAULT_HOUR
    return CronTrigger(hour=hour, minute=0, timezone="UTC")


def start_db_maintenance_scheduler(
    loop: asyncio.AbstractEventLoop, hour: int = _DEFAULT_HOUR
) -> None:
    """Start the daily job. `hour` is the configured UTC run-hour, resolved by
    the caller (which has an async context) via get_maintenance_hour() — passed
    in rather than read here so we never block the event loop at startup. The
    job's enabled-gate is re-checked at every fire, so only the hour is needed
    up front."""
    hour = hour if 0 <= hour <= 23 else _DEFAULT_HOUR
    _JOB.start(loop, _trigger(hour), describe=f"daily {hour:02d}:00 UTC")


def reschedule_db_maintenance(hour: int) -> None:
    """Move the live job to a new UTC hour (called when the admin changes it)."""
    hour = hour if 0 <= hour <= 23 else _DEFAULT_HOUR
    _JOB.reschedule(_trigger(hour), describe=f"{hour:02d}:00 UTC")


def stop_db_maintenance_scheduler() -> None:
    _JOB.stop()
