"""Text utilities."""

ELLIPSIS = "\u2026"


def truncate(text: str, n: int) -> str:
    """Return text unchanged if len(text) <= n, else its first n-1 chars followed by '…'.

    Raises ValueError if n < 1.
    """
    if n < 1:
        raise ValueError(f"n must be >= 1, got {n}")
    if len(text) <= n:
        return text
    return text[: n - 1] + ELLIPSIS