#!/usr/bin/env python3
"""Run plex-label-sync on a cron schedule from env."""

from __future__ import annotations

import os
import subprocess
import sys
import time
from datetime import datetime
from zoneinfo import ZoneInfo

from croniter import croniter

CRON_MACROS = {
    '@yearly': '0 0 1 1 *',
    '@annually': '0 0 1 1 *',
    '@monthly': '0 0 1 * *',
    '@weekly': '0 0 * * 0',
    '@daily': '0 0 * * *',
    '@midnight': '0 0 * * *',
    '@hourly': '0 * * * *',
}


def log(msg: str) -> None:
    print(f"[{datetime.now().astimezone().isoformat(timespec='seconds')}] {msg}", flush=True)


def zone() -> ZoneInfo:
    name = os.environ.get('TZ') or 'UTC'
    try:
        return ZoneInfo(name)
    except Exception as exc:
        raise SystemExit(f"Invalid TZ '{name}': {exc}") from exc


def resolve_cron_expr() -> str:
    for key in ('CRON_SCHEDULE', 'CRON', 'SYNC_CRON'):
        value = os.environ.get(key, '').strip()
        if value:
            expr = CRON_MACROS.get(value.lower(), value)
            if not croniter.is_valid(expr):
                raise SystemExit(
                    f"Invalid {key} '{value}' (expected a 5-field cron expression)"
                )
            return expr
    return '0 */6 * * *'


def next_run(expr: str, after: datetime) -> datetime:
    return croniter(expr, after).get_next(datetime)


def run_sync() -> int:
    log('Starting sync…')
    result = subprocess.run([sys.executable, '/app/sync.py'], check=False)
    log(f'Sync finished with code {result.returncode}.')
    return result.returncode


def main() -> int:
    tz = zone()
    expr = resolve_cron_expr()
    run_on_start = os.environ.get('RUN_ON_START', 'true').lower() in {'1', 'true', 'yes'}

    log(f"plex-label-sync scheduler (TZ={tz.key}, CRON_SCHEDULE='{expr}')")

    if run_on_start:
        run_sync()

    while True:
        now = datetime.now(tz=tz)
        nxt = next_run(expr, now)
        sleep_for = max(1.0, (nxt - now).total_seconds())
        log(f"Next run at {nxt.isoformat(timespec='seconds')} (sleep {sleep_for:.0f}s)")
        time.sleep(sleep_for)
        run_sync()


if __name__ == '__main__':
    sys.exit(main())