"""Scheduler for recurring-task spawning.

Every 15 minutes, creates the next occurrence of any recurring task whose spawn
time has arrived — draining `recurrence_next_spawn_at`, which is armed on task
completion. Without this job, recurring tasks would never recur.

Uses the BackgroundScheduler pattern shared with the other *_scheduler modules.
(Formerly event_scheduler.py, which also ran event reminders + CalDAV sync;
those were removed when the calendar surface was retired.)
"""
from __future__ import annotations

import asyncio
import logging

from apscheduler.schedulers.background import BackgroundScheduler
from apscheduler.triggers.interval import IntervalTrigger

logger = logging.getLogger(__name__)

_scheduler: BackgroundScheduler | None = None
_loop: asyncio.AbstractEventLoop | None = None


async def _run_recurrence_spawn() -> None:
    from scribe.services.recurrence import spawn_recurring_tasks  # noqa: PLC0415
    try:
        await spawn_recurring_tasks()
    except Exception:
        logger.warning("Recurring-task spawn job failed", exc_info=True)


def _run_recurrence_spawn_threadsafe(loop: asyncio.AbstractEventLoop) -> None:
    asyncio.run_coroutine_threadsafe(_run_recurrence_spawn(), loop)


def start_recurrence_scheduler(loop: asyncio.AbstractEventLoop) -> None:
    global _scheduler, _loop
    if _scheduler is not None:
        return
    _loop = loop
    _scheduler = BackgroundScheduler()

    # Spawn the next occurrence of due recurring tasks every 15 minutes.
    # Without this job, recurrence_next_spawn_at is armed on completion but
    # never drained, so recurring tasks never recur.
    _scheduler.add_job(
        _run_recurrence_spawn_threadsafe,
        trigger=IntervalTrigger(minutes=15),
        args=[loop],
        id="recurrence_spawn",
        replace_existing=True,
    )

    _scheduler.start()
    logger.info("Recurrence scheduler started (recurring-task spawn every 15m)")


def stop_recurrence_scheduler() -> None:
    global _scheduler
    if _scheduler is not None:
        _scheduler.shutdown(wait=False)
        _scheduler = None
        logger.info("Recurrence scheduler stopped")