#  Copyright 2026 zhaoxi826
#
#  Licensed under the Apache License, Version 2.0 (the "License");
#  you may not use this file except in compliance with the License.
#  You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#  See the License for the specific language governing permissions and
#  limitations under the License.

"""KiloStar 轻量级国际化工具。

设计原则：
- 纯内存字典，无文件 IO，Ray 远程序列化零成本。
- 支持环境变量 ``KILOSTAR_LANG`` 作为全局默认语言。
- API 层通过请求头 ``Accept-Language`` 解析首选语言。

当前支持：``zh`` (简体中文), ``en`` (English)。
"""

from __future__ import annotations

from typing import Dict

from kilostar.utils.settings import get_settings

_DEFAULT_LOCALE: str = get_settings().kilostar_lang

# ─── API / 通用消息 ────────────────────────────────────────────────────────

_MESSAGES: Dict[str, Dict[str, str]] = {
    "internal_error": {
        "zh": "服务内部错误，请稍后重试",
        "en": "Internal server error, please try again later.",
    },
    "user_not_found": {
        "zh": "用户不存在或已被删除，请重新登录",
        "en": "User does not exist or has been deleted. Please log in again.",
    },
    "provider_not_registered": {
        "zh": "Provider {provider_title} 未注册",
        "en": "Provider {provider_title} is not registered.",
    },
    "model_not_exist": {
        "zh": "模型不存在",
        "en": "Model does not exist.",
    },
    "api_not_found": {
        "zh": "API endpoint not found",
        "en": "API endpoint not found",
    },
    "frontend_not_found": {
        "zh": "Frontend build not found",
        "en": "Frontend build not found",
    },
}

# ─── 工具函数 ──────────────────────────────────────────────────────────────


def _resolve_locale(locale: str | None = None, accept_language: str | None = None) -> str:
    """确定最终使用的 locale。

    优先级：显式传入 > Accept-Language 头 > KILOSTAR_LANG 环境变量 > 默认 zh。
    """
    if locale:
        return locale if locale in ("zh", "en") else _DEFAULT_LOCALE
    if accept_language:
        first = accept_language.split(",")[0].split(";")[0].strip().lower()
        if "zh" in first:
            return "zh"
        if "en" in first:
            return "en"
    return _DEFAULT_LOCALE


def t(key: str, locale: str | None = None, accept_language: str | None = None, **kwargs) -> str:
    """通用消息翻译。

    Args:
        key: 消息键，如 ``internal_error``。
        locale: 显式指定语言代码（``zh`` / ``en``）。
        accept_language: 前端传来的 ``Accept-Language`` 头内容。
        **kwargs: 模板变量插值。

    Returns:
        翻译后的字符串；若 key 不存在则返回 key 本身。
    """
    loc = _resolve_locale(locale, accept_language)
    text = _MESSAGES.get(loc, {}).get(key) or _MESSAGES.get(_DEFAULT_LOCALE, {}).get(key) or key
    return text.format(**kwargs) if kwargs else text