import json
import re
from pathlib import Path

_LATIN_RUN_RE = re.compile(r"[A-Za-z]+")

# Фонетические правила en->ru. Применяются слева направо, длиннейшее
# совпадение выигрывает (триграфы раньше диграфов, диграфы раньше букв).
_RULES: dict[str, str] = {
    "tion": "шн",
    "sure": "шур",
    "ture": "тур",
    "ough": "оф",
    "tch": "ч",
    "sch": "ш",
    "igh": "ай",
    "ng": "нг",
    "nk": "нк",
    "qu": "кв",
    "th": "т",
    "sh": "ш",
    "ch": "ч",
    "ck": "к",
    "ph": "ф",
    "wh": "у",
    "wr": "р",
    "kn": "н",
    "ee": "и",
    "ea": "и",
    "oo": "у",
    "ou": "ау",
    "ow": "ау",
    "ai": "ай",
    "ay": "эй",
    "oi": "ой",
    "oy": "ой",
    "au": "о",
    "aw": "о",
    "ir": "ер",
    "ur": "ер",
    "er": "ер",
    "ar": "ар",
    "or": "ор",
    "a": "а",
    "b": "б",
    "c": "к",
    "d": "д",
    "e": "е",
    "f": "ф",
    "g": "г",
    "h": "х",
    "i": "и",
    "j": "дж",
    "k": "к",
    "l": "л",
    "m": "м",
    "n": "н",
    "o": "о",
    "p": "п",
    "q": "к",
    "r": "р",
    "s": "с",
    "t": "т",
    "u": "у",
    "v": "в",
    "w": "у",
    "x": "кс",
    "y": "и",
    "z": "з",
}
_RULE_KEYS = sorted(_RULES, key=len, reverse=True)

_dict_path = Path("translit_dict.json")
_cache: tuple[dict[str, str], dict[str, str]] | None = None


def set_dict_path(path: str | Path) -> None:
    global _dict_path, _cache
    _dict_path = Path(path)
    _cache = None


def _load_dict() -> tuple[dict[str, str], dict[str, str]]:
    global _cache
    if _cache is None:
        data = json.loads(_dict_path.read_text(encoding="utf-8"))
        exact = {k.lower(): v for k, v in data.get("exact", {}).items()}
        abbrev = {k.upper(): v for k, v in data.get("abbreviations", {}).items()}
        _cache = (exact, abbrev)
    return _cache


def _apply_rules(word: str) -> str:
    out: list[str] = []
    i = 0
    n = len(word)
    while i < n:
        for key in _RULE_KEYS:
            if word.startswith(key, i):
                out.append(_RULES[key])
                i += len(key)
                break
        else:
            out.append(word[i])
            i += 1
    result = "".join(out)
    if word.endswith("e") and len(result) > 2 and result.endswith("е"):
        result = result[:-1]
    return result


def _match_case(token: str, lower_out: str) -> str:
    if token.isupper():
        return lower_out.upper()
    if token[:1].isupper():
        return lower_out.capitalize()
    return lower_out


def transliterate_token(token: str) -> str:
    exact, abbrev = _load_dict()
    if token.isupper() and token in abbrev:
        return abbrev[token]
    key = token.lower()
    if key in exact:
        return _match_case(token, exact[key])
    return _match_case(token, _apply_rules(key))


def transliterate_latin(text: str) -> str:
    return _LATIN_RUN_RE.sub(lambda m: transliterate_token(m.group()), text)