"""Cross-reference slugs shared by the export backends."""

from __future__ import annotations

import re

_LABEL_RE = re.compile(r"[^\w\-]+", re.UNICODE)


def sanitize_label(name: str | None, prefix: str = "obj", separator: str = ":") -> str:
    """
    Turn a `%id` caption name into a target usable as an anchor.

    `separator` differs per backend: LaTeX `\\label` accepts a colon, an
    XML `NCName` does not.
    """
    if not name:
        return prefix
    cleaned = _LABEL_RE.sub("-", name.strip()).strip("-")
    return f"{prefix}{separator}{cleaned or 'x'}"