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.cpp | 121 ++++++++++++++++++++++----------------------------
 1 file changed, 53 insertions(+), 68 deletions(-)

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

diff --git a/server/src/locale.cpp b/server/src/locale.cpp
index 652349c..92bc33b 100644
--- a/server/src/locale.cpp
+++ b/server/src/locale.cpp
@@ -69,6 +69,55 @@ public:
   ~icu_priority_locale_vec_iterator() override = default;
 };
 
+auto to_bcp47_lang_tag(std::locale locale) -> std::optional<std::string>
+{
+  auto const& locale_info = std::use_facet<blocale::info>(locale);
+  auto ec = UErrorCode::U_ZERO_ERROR;
+  auto bcp47_lang_tag =
+      icu::Locale{locale_info.name().c_str()}.toLanguageTag<std::string>(ec);
+  if (U_FAILURE(ec))
+    return std::nullopt;
+  return bcp47_lang_tag;
+}
+
+auto bcp47_tag::id = std::locale::id{};
+
+bcp47_tag::bcp47_tag(std::locale locale)
+{
+  auto mtag = to_bcp47_lang_tag(locale);
+  if (!mtag)
+    throw std::invalid_argument{
+      "locale name cannot be expressed as a BCP 47 language tag"
+    };
+  tag_ = *mtag;
+}
+
+auto bcp47_tag::tag() const -> std::string_view { return tag_; }
+
+auto selector::make_matcher(std::vector<std::locale> const& supported_locales)
+    -> icu::LocaleMatcher
+{
+  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);
+  }
+  builder.setNoDefaultLocale();
+  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;
+}
+
 // Trimming optional whitespace as defined in RFC 9110, § 12.4.2.
 auto selector::ltrim_ows(std::string_view s) -> std::string_view
 {
@@ -87,59 +136,6 @@ auto selector::trim_ows(std::string_view s) -> std::string_view
   return rtrim_ows(ltrim_ows(s));
 }
 
-auto selector::from_icu_locale(icu::Locale const& l) const -> std::locale
-{
-  auto posix_name = std::string{l.getLanguage()};
-  if (l.getScript() && std::strlen(l.getScript()) > 0)
-  {
-    posix_name += "_";
-    posix_name += l.getScript();
-  }
-  if (l.getCountry() && std::strlen(l.getCountry()) > 0)
-  {
-    posix_name += "_";
-    posix_name += l.getCountry();
-  }
-  posix_name += ".UTF-8";
-  auto added_at = false;
-  if (l.getVariant() && std::strlen(l.getVariant()) > 0)
-  {
-    added_at = true;
-    posix_name += "@";
-    posix_name += l.getVariant();
-  }
-  auto ec = UErrorCode::U_ZERO_ERROR;
-  auto* keywords = l.createKeywords(ec);
-  if (U_FAILURE(ec))
-    throw std::runtime_error{"failed to create keywords"};
-  if (keywords)
-  {
-    std::int32_t kw_len = 0;
-    char const* kw = nullptr;
-    while (kw = keywords->next(&kw_len, ec), !U_FAILURE(ec) && kw)
-    {
-      auto value =
-          l.getKeywordValue<std::string>(icu::StringPiece(kw, kw_len), ec);
-      if (!added_at)
-      {
-        posix_name += "@";
-        added_at = true;
-      }
-      else
-      {
-        posix_name += ";";
-      }
-      posix_name += kw;
-      posix_name += "=";
-      posix_name += value;
-    }
-    if (U_FAILURE(ec))
-      throw std::runtime_error{"failed to iterate over keywords"};
-    delete keywords;
-  }
-  return lgen_->generate(posix_name);
-}
-
 auto selector::select(std::string_view accept_language) const -> std::locale
 {
   using namespace std::literals::string_view_literals;
@@ -194,21 +190,10 @@ auto selector::select(std::string_view accept_language) const -> std::locale
   auto res = matcher_.getBestMatchResult(it, ec);
   if (U_FAILURE(ec))
     return default_;
-  auto resolved = res.makeResolvedLocale(ec); // TODO: maybe don't?
-  if (U_FAILURE(ec))
-    return from_icu_locale(*res.getSupportedLocale());
-  return from_icu_locale(resolved);
-}
-
-auto to_bcp47_lang_tag(std::locale locale) -> std::optional<std::string>
-{
-  auto const& locale_info = std::use_facet<blocale::info>(locale);
-  auto ec = UErrorCode::U_ZERO_ERROR;
-  auto bcp47_lang_tag =
-      icu::Locale{locale_info.name().c_str()}.toLanguageTag<std::string>(ec);
-  if (U_FAILURE(ec))
-    return std::nullopt;
-  return bcp47_lang_tag;
+  auto i = res.getSupportedIndex();
+  if (i == -1)
+    return default_;
+  return supported_[util::size_from_int(i).value()];
 }
 
 #ifdef LOCALEDIR
-- 
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