i18n.py

# encoding = utf-8

import json
from pathlib import Path
from typing import Dict, Any, Optional

class I18n:
    _instance: Optional["I18n"] = None

    def __new__(cls, *args, **kwargs):
        # Keep a shared i18n state so repeated I18n() calls use the same language.
        if cls._instance is None:
            cls._instance = super().__new__(cls)
        return cls._instance

    def __init__(self, locale_dir: str = "locales", default_lang: str = "zh_CN"):
        if getattr(self, "_initialized", False):
            return
        self.locale_dir = Path(locale_dir)
        self.default_lang = default_lang
        self.current_lang = default_lang
        self.translations: Dict[str, Any] = {}
        self._load_translations()
        self._initialized = True
    
    def _load_translations(self):
        """加载所有语言包"""
        # 重新扫描并加载所有 json 文件
        self.translations = {}
        if not self.locale_dir.exists():
            return
        for lang_file in self.locale_dir.glob("*.json"):
            lang = lang_file.stem
            try:
                with open(lang_file, 'r', encoding='utf-8') as f:
                    self.translations[lang] = json.load(f)
            except Exception:
                # 忽略单个语言文件的解析错误
                continue

    def reload(self):
        """手动重新加载 locales 目录下的语言文件（当文件变化时调用）。"""
        self._load_translations()

    def available_languages(self):
        """返回当前可用的语言代码列表（按字母排序）。"""
        return sorted(list(self.translations.keys()))
    
    def set_language(self, lang: str):
        """切换当前语言"""
        if lang in self.translations:
            self.current_lang = lang
        else:
            raise ValueError(f"Language {lang} not supported")
    
    def get(self, key: str, **kwargs) -> str:
        """获取翻译文本"""
        # 尝试获取当前语言的翻译
        text = self._get_nested(self.translations.get(self.current_lang, {}), key)
        
        # 如果当前语言没有，尝试默认语言
        if text is None and self.current_lang != self.default_lang:
            text = self._get_nested(self.translations.get(self.default_lang, {}), key)
        
        # 如果都没有，返回key本身
        if text is None:
            return key
        
        # 格式化字符串
        if kwargs:
            try:
                return text.format(**kwargs)
            except KeyError:
                return text
        return text
    
    def _get_nested(self, data: dict, key: str):
        """支持点号分隔的嵌套key"""
        keys = key.split('.')
        for k in keys:
            if isinstance(data, dict):
                data = data.get(k)
            else:
                return None
        return data
    
    def __getitem__(self, key: str, **kwargs) -> str:
        """使实例可以用[]调用"""
        return self.get(key, **kwargs)
if __name__ == "__main__":
    # 使用示例
    i18n = I18n()

    # 切换语言
    i18n.set_language('en_US')

    # 获取翻译
    print(i18n['errors.not_found'])