I18N middleware implementation was added

telebot/asyncio_middlewares.py

@@ -1,3 +1,15 @@
+import contextvars
+
+try:
+    from babel.support import LazyProxy
+
+    babel_imported = True
+except ImportError:
+    babel_imported = False
+
+from telebot import util
+
+
 class BaseMiddleware:
     """
     Base class for middleware.
@@ -13,3 +25,85 @@ class BaseMiddleware:
 
     async def post_process(self, message, data, exception):
         raise NotImplementedError
+
+
+class I18N(BaseMiddleware):
+    """
+    This middleware provides high-level tool for internationalization
+    It is based on gettext util.
+    """
+
+    context_lang = contextvars.ContextVar('language', default=None)
+
+    def __init__(self, translations_path, domain_name: str):
+        super().__init__()
+        self.update_types = self.process_update_types()
+
+        self.path = translations_path
+        self.domain = domain_name
+        self.translations = util.find_translations(self.path, self.domain)
+
+    @property
+    def available_translations(self):
+        return list(self.translations)
+
+    def gettext(self, text: str, lang: str = None):
+        """
+        Singular translations
+        """
+
+        if lang is None:
+            lang = self.context_lang.get()
+
+        if lang not in self.translations:
+            return text
+
+        translator = self.translations[lang]
+        return translator.gettext(text)
+
+    def ngettext(self, singular: str, plural: str, lang: str = None, n=1):
+        """
+        Plural translations
+        """
+        if lang is None:
+            lang = self.context_lang.get()
+
+        if lang not in self.translations:
+            if n == 1:
+                return singular
+            return plural
+
+        translator = self.translations[lang]
+        return translator.ngettext(singular, plural, n)
+
+    def lazy_gettext(self, text: str, lang: str = None):
+        if not babel_imported:
+            raise RuntimeError('babel module is not imported. Check that you installed it.')
+        return LazyProxy(self.gettext, text, lang, enable_cache=False)
+
+    def lazy_ngettext(self, singular: str, plural: str, lang: str = None, n=1):
+        if not babel_imported:
+            raise RuntimeError('babel module is not imported. Check that you installed it.')
+        return LazyProxy(self.ngettext, singular, plural, lang, n, enable_cache=False)
+
+    async def get_user_language(self, obj):
+        """
+        You need to override this method and return user language
+        """
+        raise NotImplementedError
+
+    def process_update_types(self) -> list:
+        """
+        You need to override this method and return any update types which you want to be processed
+        """
+        raise NotImplementedError
+
+    async def pre_process(self, message, data):
+        """
+        context language variable will be set each time when update from 'process_update_types' comes
+        value is the result of 'get_user_language' method
+        """
+        self.context_lang.set(await self.get_user_language(obj=message))
+
+    async def post_process(self, message, data, exception):
+        pass