"""get_lang and t(): language from Telegram user, translate by key with fallback to en."""

from typing import TYPE_CHECKING

import duty_teller.config as config
from duty_teller.i18n.messages import MESSAGES

if TYPE_CHECKING:
    from telegram import User


def get_lang(user: "User | None") -> str:
    """
    Normalize Telegram user language to 'ru' or 'en'.
    If user has language_code starting with 'ru' (e.g. ru, ru-RU) return 'ru', else 'en'.
    When user is None or has no language_code, return config.DEFAULT_LANGUAGE.
    """
    if user is None or not getattr(user, "language_code", None):
        return config.DEFAULT_LANGUAGE
    code = (user.language_code or "").strip().lower()
    return "ru" if code.startswith("ru") else "en"


def t(lang: str, key: str, **kwargs: str) -> str:
    """
    Return translated string for lang and key; substitute kwargs into placeholders like {phone}.
    Fallback to 'en' if key missing for lang.
    """
    lang = "ru" if lang == "ru" else "en"
    messages = MESSAGES.get(lang) or MESSAGES["en"]
    template = messages.get(key)
    if template is None:
        template = MESSAGES["en"].get(key, key)
    try:
        return template.format(**kwargs)
    except KeyError:
        return template