Build a translation facility for FastAPI

Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

aurweb/l10n.py

@@ -16,3 +16,25 @@ class Translator:
                                                          self._localedir,
                                                          languages=[lang])
         return self._translator[lang].gettext(s)
+
+
+def get_translator_for_request(request):
+    """
+    Determine the preferred language from a FastAPI request object and build a
+    translator function for it.
+
+    Example:
+    ```python
+    _ = get_translator_for_request(request)
+    print(_("Hello"))
+    ```
+    """
+    lang = request.cookies.get("AURLANG")
+    if lang is None:
+        lang = aurweb.config.get("options", "default_lang")
+    translator = Translator()
+
+    def translate(message):
+        return translator.translate(message, lang)
+
+    return translate