Add first-visit language redirect middleware

mandelstudio/middleware_language_redirect.py

@@ -0,0 +1,80 @@
+from __future__ import annotations
+
+from django.conf import settings
+from django.http import HttpRequest, HttpResponseRedirect
+from django.utils.translation import get_language_from_request
+
+
+class FirstVisitLanguageRedirectMiddleware:
+    """Redirect first-visit requests to a supported language path."""
+
+    SKIP_PREFIXES = (
+        "/admin",
+        "/cms",
+        "/dashboard",
+        "/manage",
+        "/api",
+        "/static",
+        "/media",
+        "/i18n/setlang",
+    )
+
+    def __init__(self, get_response):
+        self.get_response = get_response
+        self.language_cookie_name = getattr(
+            settings, "LANGUAGE_COOKIE_NAME", "django_language"
+        )
+        self.default_language = settings.LANGUAGE_CODE.split("-")[0].lower()
+        self.supported_languages = {
+            code.split("-")[0].lower() for code, _label in settings.LANGUAGES
+        }
+
+    def __call__(self, request: HttpRequest):
+        redirect_url = self._build_redirect_url(request)
+        if redirect_url:
+            return HttpResponseRedirect(redirect_url)
+        return self.get_response(request)
+
+    def _build_redirect_url(self, request: HttpRequest) -> str | None:
+        if request.method != "GET":
+            return None
+        if self.language_cookie_name in request.COOKIES:
+            return None
+
+        path = request.path_info or "/"
+        if self._should_skip_path(path):
+            return None
+        if self._is_localized_path(path):
+            return None
+
+        target_lang = self._preferred_language(request)
+        if not target_lang or target_lang == self.default_language:
+            return None
+
+        if path == "/":
+            localized_path = f"/{target_lang}/"
+        else:
+            localized_path = f"/{target_lang}{path}"
+
+        query = request.META.get("QUERY_STRING")
+        if query:
+            return f"{localized_path}?{query}"
+        return localized_path
+
+    def _should_skip_path(self, path: str) -> bool:
+        for prefix in self.SKIP_PREFIXES:
+            if path == prefix or path.startswith(f"{prefix}/"):
+                return True
+        return False
+
+    def _is_localized_path(self, path: str) -> bool:
+        parts = [part for part in path.split("/") if part]
+        if not parts:
+            return False
+        return parts[0].lower() in self.supported_languages
+
+    def _preferred_language(self, request: HttpRequest) -> str | None:
+        matched = get_language_from_request(request, check_path=False)
+        if not matched:
+            return None
+        return matched.split("-")[0].lower()

mandelstudio/settings/base.py

@@ -119,6 +119,22 @@ if "django.middleware.locale.LocaleMiddleware" not in MIDDLEWARE:
     else:
         MIDDLEWARE.insert(0, "django.middleware.locale.LocaleMiddleware")
 
+# First-visit language redirect (does not override manual language cookie choice).
+if (
+    "mandelstudio.middleware_language_redirect.FirstVisitLanguageRedirectMiddleware"
+    not in MIDDLEWARE
+):
+    if "django.middleware.locale.LocaleMiddleware" in MIDDLEWARE:
+        idx = MIDDLEWARE.index("django.middleware.locale.LocaleMiddleware") + 1
+        MIDDLEWARE.insert(
+            idx,
+            "mandelstudio.middleware_language_redirect.FirstVisitLanguageRedirectMiddleware",
+        )
+    else:
+        MIDDLEWARE.append(
+            "mandelstudio.middleware_language_redirect.FirstVisitLanguageRedirectMiddleware"
+        )
+
 # Redirect production apex to `www` for a single canonical domain.
 if "mandelstudio.middleware.RedirectApexToWwwMiddleware" not in MIDDLEWARE:
     MIDDLEWARE.insert(0, "mandelstudio.middleware.RedirectApexToWwwMiddleware")