4 files changed, 21 insertions, 0 deletions
diff --git a/AK/String.cpp b/AK/String.cpp
index c5e6f7965c..a74dec2c41 100644
--- a/AK/String.cpp
+++ b/AK/String.cpp
@@ -388,6 +388,11 @@ String String::to_titlecase() const
     return StringUtils::to_titlecase(*this);
 }
 
+String String::invert_case() const
+{
+    return StringUtils::invert_case(*this);
+}
+
 bool operator<(char const* characters, String const& string)
 {
     return string.view() > characters;
diff --git a/AK/String.h b/AK/String.h
index 674cfdb6cb..2c73bdc838 100644
--- a/AK/String.h
+++ b/AK/String.h
@@ -121,6 +121,7 @@ public:
     [[nodiscard]] String to_uppercase() const;
     [[nodiscard]] String to_snakecase() const;
     [[nodiscard]] String to_titlecase() const;
+    [[nodiscard]] String invert_case() const;
 
     [[nodiscard]] bool is_whitespace() const { return StringUtils::is_whitespace(*this); }
 
diff --git a/AK/StringUtils.cpp b/AK/StringUtils.cpp
index 2c66ec68d5..8e7a4bc646 100644
--- a/AK/StringUtils.cpp
+++ b/AK/StringUtils.cpp
@@ -462,6 +462,20 @@ String to_titlecase(StringView str)
     return builder.to_string();
 }
 
+String invert_case(StringView str)
+{
+    StringBuilder builder(str.length());
+
+    for (auto ch : str) {
+        if (is_ascii_lower_alpha(ch))
+            builder.append(to_ascii_uppercase(ch));
+        else
+            builder.append(to_ascii_lowercase(ch));
+    }
+
+    return builder.to_string();
+}
+
 String replace(StringView str, StringView needle, StringView replacement, bool all_occurrences)
 {
     if (str.is_empty())
diff --git a/AK/StringUtils.h b/AK/StringUtils.h
index 9ba0012041..0e8470b4d5 100644
--- a/AK/StringUtils.h
+++ b/AK/StringUtils.h
@@ -78,6 +78,7 @@ Optional<size_t> find_any_of(StringView haystack, StringView needles, SearchDire
 
 String to_snakecase(StringView);
 String to_titlecase(StringView);
+String invert_case(StringView);
 
 String replace(StringView, StringView needle, StringView replacement, bool all_occurrences = false);
 size_t count(StringView, StringView needle);