From dcd4ef58d0cb3ae3d5c88f50736f7716f0c5d893 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Kacprzak?= <michal@e-kacprzak.eu>
Date: Mon, 3 Aug 2026 01:06:47 +0200
Subject: [PATCH] Detect GUI language from browser settings

---
 frigate_camera_control_bridge/app.py | 50 ++++++++++++++++++++++++----
 tests/test_language.py               | 27 +++++++++++++++
 2 files changed, 70 insertions(+), 7 deletions(-)
 create mode 100644 tests/test_language.py

diff --git a/frigate_camera_control_bridge/app.py b/frigate_camera_control_bridge/app.py
index 1215bc3..5a092b0 100644
--- a/frigate_camera_control_bridge/app.py
+++ b/frigate_camera_control_bridge/app.py
@@ -20,7 +20,7 @@ DEFAULT_CONFIG = "/etc/frigate-camera-control-bridge.json"
 LOG = logging.getLogger("frigate-camera-control-bridge")
 STREAM_URL_RE = re.compile(r"(?:rtsp|rtsps|http|https)://[^\s'\"<>]+", re.IGNORECASE)
 
-from .i18n import DEFAULT_LANGUAGE, normalize_language, text_for
+from .i18n import DEFAULT_LANGUAGE, available_languages, normalize_language, text_for
 from .ui import read_static_file, render_page
 
 
@@ -113,6 +113,39 @@ def env_secret(name):
         raise RuntimeError(f"failed to read {name}_FILE={path}: {exc}") from exc
 
 
+def language_from_accept_header(value):
+    # HTTP Accept-Language can contain regional tags and q weights. The GUI
+    # ships language catalogs by base code, so pl-PL and pl both resolve to pl.
+    if not value:
+        return DEFAULT_LANGUAGE
+    supported = available_languages()
+    matches = []
+    for index, raw_item in enumerate(value.split(",")):
+        parts = [item.strip() for item in raw_item.split(";") if item.strip()]
+        if not parts:
+            continue
+        tag = parts[0].lower().replace("_", "-")
+        if tag == "*":
+            continue
+        quality = 1.0
+        for param in parts[1:]:
+            if not param.lower().startswith("q="):
+                continue
+            try:
+                quality = float(param.split("=", 1)[1])
+            except ValueError:
+                quality = 0.0
+        if quality <= 0:
+            continue
+        base = tag.split("-", 1)[0]
+        if base in supported:
+            matches.append((-quality, index, base))
+    if not matches:
+        return DEFAULT_LANGUAGE
+    matches.sort()
+    return matches[0][2]
+
+
 def config_from_env():
     # Env mode is the preferred sidecar mode. It needs only a Frigate API URL,
     # MQTT connection parameters, and camera credentials. The old JSON config is
@@ -1582,7 +1615,7 @@ class CameraControlBridge:
         class Handler(BaseHTTPRequestHandler):
             def do_GET(self):
                 parsed = urllib.parse.urlsplit(self.path)
-                lang = bridge.request_language(parsed.query)
+                lang = bridge.request_language(parsed.query, self.headers)
                 if parsed.path in ("/healthz", "/readyz"):
                     self.send_json({"ok": True, "actions": bridge.action_count()})
                     return
@@ -1622,7 +1655,7 @@ class CameraControlBridge:
 
             def do_POST(self):
                 parsed = urllib.parse.urlsplit(self.path)
-                lang = bridge.request_language(parsed.query)
+                lang = bridge.request_language(parsed.query, self.headers)
                 if not bridge.http_authorized(self.headers, parsed.query):
                     self.send_response(401)
                     self.end_headers()
@@ -1697,12 +1730,15 @@ class CameraControlBridge:
     def html_page(self, lang=None, token_param=None):
         with self.action_lock:
             actions = list(self.actions.values())
-        return render_page(actions, lang or self.default_language, token_param)
+        return render_page(actions, lang or DEFAULT_LANGUAGE, token_param)
 
-    def request_language(self, query):
+    def request_language(self, query, headers=None):
         values = urllib.parse.parse_qs(query)
-        requested = values.get("lang", [self.default_language])[0]
-        return normalize_language(requested)
+        requested = values.get("lang", [None])[0]
+        if requested:
+            return normalize_language(requested)
+        accept_language = headers.get("Accept-Language") if headers else None
+        return language_from_accept_header(accept_language)
 
     def _handle_signal(self, signum, _frame):
         LOG.info("received signal %s, stopping", signum)
diff --git a/tests/test_language.py b/tests/test_language.py
new file mode 100644
index 0000000..a85bf56
--- /dev/null
+++ b/tests/test_language.py
@@ -0,0 +1,27 @@
+import unittest
+
+from frigate_camera_control_bridge.app import language_from_accept_header
+
+
+class LanguageDetectionTest(unittest.TestCase):
+    def test_browser_language_uses_supported_base_code(self):
+        self.assertEqual(
+            language_from_accept_header("pl-PL,pl;q=0.9,en-US;q=0.8"),
+            "pl",
+        )
+
+    def test_quality_weight_wins_over_order(self):
+        self.assertEqual(
+            language_from_accept_header("en-US;q=0.4,pl-PL;q=0.9"),
+            "pl",
+        )
+
+    def test_unsupported_languages_fall_back_to_english(self):
+        self.assertEqual(language_from_accept_header("fr-FR,de;q=0.8"), "en")
+
+    def test_empty_header_falls_back_to_english(self):
+        self.assertEqual(language_from_accept_header(None), "en")
+
+
+if __name__ == "__main__":
+    unittest.main()