import re
import unicodedata


def slugify(title: str, max_length: int = 80) -> str:
    """
    Convert a title to a filesystem-friendly slug:
    - normalize unicode to NFKD and strip accents
    - lowercase
    - replace non alphanum with hyphens
    - collapse duplicate hyphens
    - trim hyphens at edges
    - limit length (keeping whole segments if possible)
    """
    if not title:
        return "untitled"

    # Normalize accents
    normalized = unicodedata.normalize("NFKD", title)
    ascii_str = normalized.encode("ascii", "ignore").decode("ascii")

    # Lowercase and replace non-alphanum with hyphen
    slug = re.sub(r"[^a-z0-9]+", "-", ascii_str.lower()).strip("-")

    if not slug:
        slug = "untitled"

    # Collapse multiple hyphens
    slug = re.sub(r"-{2,}", "-", slug)

    # Respect max length, try not to cut segments
    if len(slug) > max_length:
        parts = slug.split("-")
        cut = []
        total = 0
        for p in parts:
            # +1 for the hyphen when joining (except first)
            add = len(p) + (1 if cut else 0)
            if total + add > max_length:
                break
            cut.append(p)
            total += add
        slug = "-".join(cut) if cut else slug[:max_length].rstrip("-")

    return slug