Detect GUI language from browser settings

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()