from datetime import datetime

from sqlalchemy.orm import Session

from models import ChatAttachment


def purge_expired_chat_attachments(
    db: Session,
    *,
    now: datetime | None = None,
) -> int:
    """Remove expired derived image data; raw image bytes are never persisted."""
    count = db.query(ChatAttachment).filter(
        ChatAttachment.expires_at < (now or datetime.utcnow())
    ).delete(synchronize_session=False)
    if count:
        db.commit()
        db.expire_all()
    return count