From a4408b5ac4ec10421bf9a7d5bf277946ec9f786e Mon Sep 17 00:00:00 2001
From: Rutger Broekhoff
Date: Thu, 10 Sep 2026 10:59:59 +0200
Subject: Timing and slow locale negotation fixes

---
 server/src/locale.cppm | 65 ++++++++++++++++++++------------------------------
 1 file changed, 26 insertions(+), 39 deletions(-)

(limited to 'server/src/locale.cppm')

diff --git a/server/src/locale.cppm b/server/src/locale.cppm
index 263de1d..00a3d36 100644
--- a/server/src/locale.cppm
+++ b/server/src/locale.cppm
@@ -26,65 +26,52 @@ concept locale_input_range =
     && std::
         same_as<std::locale const&, std::ranges::range_const_reference_t<T>>;
 
+class bcp47_tag : public std::locale::facet
+{
+  std::string tag_;
+
+public:
+  static std::locale::id id;
+
+  explicit bcp47_tag(std::locale locale);
+  ~bcp47_tag() override = default;
+
+  auto tag() const -> std::string_view;
+};
+
 // Helps select a locale based on the Accept-Language header in an
 // HTTP request.
 export class selector
 {
+  std::vector<std::locale> supported_;
   std::locale default_;
   icu::LocaleMatcher matcher_;
-  std::shared_ptr<blocale::generator const> lgen_;
 
-  auto make_matcher(
-      locale_input_range auto supported_locales, std::locale default_locale)
-  {
-    auto builder = icu::LocaleMatcher::Builder{};
-    for (auto const& supported_locale : supported_locales)
-    {
-      auto const& supported_locale_info =
-          std::use_facet<blocale::info>(supported_locale);
-      auto supported_icu_locale =
-          icu::Locale{supported_locale_info.name().c_str()};
-      if (supported_icu_locale.isBogus())
-        throw std::runtime_error{
-          "supported locale gives rise to bogus ICU locale"
-        };
-      builder.addSupportedLocale(supported_icu_locale);
-    }
-    auto const& default_locale_info =
-        std::use_facet<blocale::info>(default_locale);
-    auto default_icu_locale = icu::Locale{default_locale_info.name().c_str()};
-    if (default_icu_locale.isBogus())
-      throw std::runtime_error{"default locale gives rise to bogus ICU locale"};
-    builder.setDefaultLocale(&default_icu_locale);
-    auto ec = UErrorCode::U_ZERO_ERROR;
-    auto matcher = builder.build(ec);
-    if (U_FAILURE(ec))
-      throw std::runtime_error{"failed to build icu::LocaleMatcher"};
-    return matcher;
-  }
+  static auto make_matcher(std::vector<std::locale> const& supported_locales)
+      -> icu::LocaleMatcher;
 
   // Trimming optional whitespace as defined in RFC 9110, § 12.4.2.
   static auto ltrim_ows(std::string_view s) -> std::string_view;
   static auto rtrim_ows(std::string_view s) -> std::string_view;
   static auto trim_ows(std::string_view s) -> std::string_view;
 
-  auto from_icu_locale(icu::Locale const& l) const -> std::locale;
-
 public:
-  // Note: lgen must live at least as long as the selector constructed here!
-  // It is unfortunately not possible to copy/move a blocale::generator.
-  explicit selector(
-      locale_input_range auto locales, std::locale default_,
-      std::shared_ptr<blocale::generator const> lgen)
-    : default_{default_}, matcher_{make_matcher(locales, default_)}, lgen_{lgen}
+  explicit selector(locale_input_range auto supported, std::locale default_)
+    : supported_{
+        std::from_range,
+        supported
+            | std::views::transform(
+                [](std::locale const& locale) -> std::locale
+                { return std::locale{locale, new bcp47_tag{locale}}; })
+      },
+      default_{std::locale{default_, new bcp47_tag{default_}}},
+      matcher_{make_matcher(supported_)}
   {
   }
 
   auto select(std::string_view accept_language) const -> std::locale;
 };
 
-auto to_bcp47_lang_tag(std::locale locale) -> std::optional<std::string>;
-
 export auto make_generator() -> std::shared_ptr<blocale::generator const>;
 
 } // namespace routemon::locale
-- 
cgit v1.3