From 74b5e399a38fac0bbb8f03fb9c75638748dab430 Mon Sep 17 00:00:00 2001
From: Ali Ismayilov <993934+aliismayilov@users.noreply.github.com>
Date: Tue, 25 Nov 2025 15:09:30 +0100
Subject: [PATCH] Offer case locale specific case manipulation

---
 lib/i18n.rb       | 16 ++++++++++++++++
 test/i18n_test.rb | 17 +++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/lib/i18n.rb b/lib/i18n.rb
index 578a5969..d4917197 100644
--- a/lib/i18n.rb
+++ b/lib/i18n.rb
@@ -388,6 +388,22 @@ def available_locales_initialized?
       config.available_locales_initialized?
     end
 
+    def capitalize(string, locale: nil, rules: t(:'i18n.case_map.rules', locale:, default: nil))
+      string.capitalize(*rules)
+    end
+
+    def downcase(string, locale: nil, rules: t(:'i18n.case_map.rules', locale:, default: nil))
+      string.downcase(*rules)
+    end
+
+    def swapcase(string, locale: nil, rules: t(:'i18n.case_map.rules', locale:, default: nil))
+      string.swapcase(*rules)
+    end
+
+    def upcase(string, locale: nil, rules: t(:'i18n.case_map.rules', locale:, default: nil))
+      string.upcase(*rules)
+    end
+
   private
 
     def translate_key(key, throw, raise, locale, backend, options)
diff --git a/test/i18n_test.rb b/test/i18n_test.rb
index 90077147..436e1361 100644
--- a/test/i18n_test.rb
+++ b/test/i18n_test.rb
@@ -455,6 +455,23 @@ def call(exception, locale, key, options); key; end
     assert_equal "???", I18n.transliterate("日本語")
   end
 
+  test "upcase string" do
+    assert_equal "TÜRKIYE", I18n.upcase("Türkiye")
+  end
+
+  test "upcase string with locale" do
+    assert_equal "TÜRKIYE", I18n.upcase("Türkiye", locale: nil)
+  end
+
+  test "upcase string with rules" do
+    assert_equal "TÜRKİYE", I18n.upcase("Türkiye", rules: :turkic)
+  end
+
+  test "upcase string with stored rules" do
+    store_translations(:tr, {i18n: {case_map: {rules: [:turkic]}}})
+    assert_equal "TÜRKİYE", I18n.upcase("Türkiye", locale: :tr)
+  end
+
   test "I18n.locale_available? returns true when the passed locale is available" do
     I18n.available_locales = [:en, :de]
     assert_equal true, I18n.locale_available?(:de)