"""Timezone utilities for converting UTC datetimes to the venue's local time."""
from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
from datetime import datetime, timezone

from database import SessionLocal
from models.settings import PosSettings

_FALLBACK = "Europe/Athens"


def _get_tz_name() -> str:
    db = SessionLocal()
    try:
        row = db.query(PosSettings).filter(PosSettings.key == "system.timezone").first()
        return row.value if row and row.value else _FALLBACK
    except Exception:
        return _FALLBACK
    finally:
        db.close()


def to_local(dt: datetime) -> datetime:
    """Convert a UTC-aware datetime to the venue's configured local timezone."""
    if dt is None:
        return dt
    if dt.tzinfo is None:
        dt = dt.replace(tzinfo=timezone.utc)
    try:
        tz = ZoneInfo(_get_tz_name())
    except ZoneInfoNotFoundError:
        tz = ZoneInfo(_FALLBACK)
    return dt.astimezone(tz)


def local_strftime(dt: datetime, fmt: str) -> str:
    """Format a UTC-aware datetime in local time using the venue's timezone."""
    if dt is None:
        return "—"
    return to_local(dt).strftime(fmt)