"""Text normalization for accent-insensitive search.

Strips diacritics so "phở" -> "pho" and "ñandú" -> "nandu".
Used now for display/utility; drives `title_norm` shadow column in Phase 2 listings.
"""
import unicodedata

# Vietnamese đ/Đ do not decompose via NFKD, map explicitly.
_EXPLICIT = {
    "đ": "d", "Đ": "d",
    "ð": "d", "Ð": "d",
}


def normalize(text: str) -> str:
    if not text:
        return ""
    out = []
    for ch in text:
        if ch in _EXPLICIT:
            out.append(_EXPLICIT[ch])
            continue
        decomposed = unicodedata.normalize("NFKD", ch)
        stripped = "".join(c for c in decomposed if not unicodedata.combining(c))
        out.append(stripped)
    return "".join(out).lower().strip()