"""
scheduler.py — Background scan scheduler using APScheduler.
"""

import logging
import threading

from apscheduler.schedulers.background import BackgroundScheduler

from config import Settings
from scanner import (
    create_scan_record,
    has_any_scan_completed,
    run_full_scan,
    run_incremental_scan,
)

logger = logging.getLogger(__name__)

_scheduler: BackgroundScheduler | None = None
_scan_lock = threading.Lock()
_active_scan_id: int | None = None


def get_active_scan_id() -> int | None:
    return _active_scan_id


def is_scan_running() -> bool:
    return _active_scan_id is not None


def _run_scan_protected(scan_type: str, settings: Settings) -> int | None:
    """Try to acquire lock and run a scan. Returns scan_id or None if already running."""
    global _active_scan_id
    if not _scan_lock.acquire(blocking=False):
        logger.warning("Scan already in progress — skipping %s scan request", scan_type)
        return None

    scan_id = create_scan_record(scan_type)
    _active_scan_id = scan_id
    logger.info("Scan %s started (id=%d)", scan_type, scan_id)

    def _run():
        global _active_scan_id
        try:
            if scan_type == "full":
                run_full_scan(settings, scan_id)
            else:
                run_incremental_scan(settings, scan_id)
        finally:
            _active_scan_id = None
            _scan_lock.release()
            logger.info("Scan %s finished (id=%d)", scan_type, scan_id)

    thread = threading.Thread(target=_run, daemon=True, name=f"scan-{scan_type}-{scan_id}")
    thread.start()
    return scan_id


def trigger_full_scan(settings: Settings) -> int | None:
    return _run_scan_protected("full", settings)


def trigger_incremental_scan(settings: Settings) -> int | None:
    return _run_scan_protected("incremental", settings)


def start_scheduler(settings: Settings) -> None:
    global _scheduler

    _scheduler = BackgroundScheduler(timezone="UTC")
    _scheduler.add_job(
        func=lambda: trigger_incremental_scan(settings),
        trigger="interval",
        hours=settings.scan_interval_hours,
        id="incremental_scan",
        replace_existing=True,
    )
    _scheduler.start()
    logger.info(
        "Scheduler started — incremental scan every %d hour(s)",
        settings.scan_interval_hours,
    )

    # Trigger initial full scan if the database has never been scanned
    if not has_any_scan_completed():
        logger.info("No prior completed scan found — launching initial full scan")
        trigger_full_scan(settings)


def stop_scheduler() -> None:
    if _scheduler and _scheduler.running:
        _scheduler.shutdown(wait=False)
        logger.info("Scheduler stopped")