from __future__ import annotations

import unicodedata
from functools import lru_cache

_ZERO_WIDTH_CHARS = {
    "\u200b",
    "\u200c",
    "\u200d",
    "\ufeff",
    "\u2060",
}


@lru_cache(maxsize=1)
def _opencc_converter():
    try:
        from opencc import OpenCC
    except Exception:
        return None
    try:
        return OpenCC("t2s")
    except Exception:
        return None


def _to_simplified(value: str) -> str:
    converter = _opencc_converter()
    if converter is None:
        return value
    return converter.convert(value)


def normalize_text(value: str | None) -> str:
    """Normalize text before keyword matching.

    The local keyword MVP removes obvious bypass characters only; it does not
    attempt semantic rewriting or fuzzy matching.
    """
    if not value:
        return ""

    normalized = unicodedata.normalize("NFKC", value).lower()
    normalized = _to_simplified(normalized)

    chars: list[str] = []
    for char in normalized:
        if char in _ZERO_WIDTH_CHARS:
            continue
        category = unicodedata.category(char)
        if category[0] in {"P", "Z"}:
            continue
        chars.append(char)
    return "".join(chars)