"""Background scheduler for periodic tasks.

All user-scoped jobs iterate over every active user (with that user's
timezone/context active) so each user's alarms, reminders, calendars,
pomodoro, countdowns and weather are serviced independently.
"""
from apscheduler.schedulers.background import BackgroundScheduler
from backend.calendar_mgr import sync_all_subscriptions, get_upcoming_reminders
from backend.weather_mgr import fetch_weather, fetch_hourly
from backend.alarm_mgr import check_alarms
from backend.countdown_mgr import check_countdowns
from backend.pomodoro_mgr import check_and_trigger
from backend.models import get_db
from backend.time_util import set_thread_user, clear_thread_user


_scheduler: BackgroundScheduler | None = None


def _each_user(app, fn):
    """Run fn(user_id) for every active user inside the app context."""
    with app.app_context():
        db = get_db(app.config.get("DB_PATH", "data.db"))
        rows = db.execute("SELECT id FROM users WHERE status='active' ORDER BY id").fetchall()
        db.close()
        for u in rows:
            uid = u["id"]
            try:
                set_thread_user(uid)
                fn(uid)
            except Exception as e:
                app.logger.error(f"Scheduler error for user {uid}: {e}")
            finally:
                clear_thread_user()


def start_scheduler(app):
    global _scheduler
    _scheduler = BackgroundScheduler()

    @_scheduler.scheduled_job("interval", seconds=10, id="check_alarms")
    def _check_alarms():
        _each_user(app, check_alarms)

    @_scheduler.scheduled_job("interval", minutes=1, id="check_reminders")
    def _check_reminders():
        def _run(uid):
            due = get_upcoming_reminders(uid)
            if due:
                app.event_bus.publish("reminder_due", {"events": due}, user_id=uid)
                app.logger.info(f"Reminders due for user {uid}: {len(due)} events")
        _each_user(app, _run)

    @_scheduler.scheduled_job("interval", minutes=30, id="sync_calendars")
    def _sync_calendars():
        with app.app_context():
            sync_all_subscriptions()

    @_scheduler.scheduled_job("cron", minute="0,30", id="fetch_weather")
    def _fetch_weather():
        _each_user(app, fetch_weather)

    @_scheduler.scheduled_job("interval", seconds=1, id="check_pomodoro")
    def _check_pomodoro():
        _each_user(app, check_and_trigger)

    @_scheduler.scheduled_job("cron", minute="1", id="fetch_hourly")
    def _fetch_hourly():
        _each_user(app, fetch_hourly)

    @_scheduler.scheduled_job("interval", seconds=1, id="check_countdowns")
    def _check_countdowns():
        def _run(uid):
            triggered = check_countdowns(uid)
            if triggered:
                app.logger.info(f"Countdowns triggered for user {uid}: {[c['label'] for c in triggered]}")
        _each_user(app, _run)

    _scheduler.start()


def stop_scheduler():
    global _scheduler
    if _scheduler:
        _scheduler.shutdown(wait=False)
        _scheduler = None