import base64


def offset_to_page_id(offset: int, has_next: bool) -> str | None:
    if not has_next:
        return None
    next_page_id = base64.b64encode(str(offset).encode()).decode()
    return next_page_id


def page_id_to_offset(page_id: str | None) -> int:
    if not page_id:
        return 0
    offset = int(base64.b64decode(page_id).decode())
    return offset