import re

def blocking_key(name: str, lang: str) -> str:
    """
    Generate a blocking key for grouping candidate pairs.
    Strips legal suffixes, normalizes, takes first 4 chars.
    """
    canonical = canonical_form(name, lang)

    legal_suffixes = [
        r"\b(co|corp|inc|ltd|llc|plc|gmbh|ag|sa|bv)\b\.?",
        r"\b(주식회사|kabushiki kaisha|kk|株式会社|有限公司)\b",
    ]
    for pattern in legal_suffixes:
        canonical = re.sub(pattern, "", canonical, flags=re.IGNORECASE)

    canonical = re.sub(r"[^a-z0-9]", "", canonical)
    return canonical[:4]