From a0720bbe3cdfe3174e3d064356b21f0fcd37832e Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Mon, 13 Apr 2026 15:05:38 +0200
Subject: kstd/format: add kstd::format_to

---
 libs/kstd/include/kstd/bits/format/vformat.hpp | 42 +++++++++++++++++++++++---
 1 file changed, 37 insertions(+), 5 deletions(-)

(limited to 'libs/kstd/include')

diff --git a/libs/kstd/include/kstd/bits/format/vformat.hpp b/libs/kstd/include/kstd/bits/format/vformat.hpp
index d032c3a..69c7f33 100644
--- a/libs/kstd/include/kstd/bits/format/vformat.hpp
+++ b/libs/kstd/include/kstd/bits/format/vformat.hpp
@@ -8,6 +8,8 @@
 #include <kstd/bits/format/string.hpp>
 #include <kstd/string>
 
+#include <algorithm>
+#include <iterator>
 #include <string_view>
 #include <type_traits>
 
@@ -36,15 +38,30 @@ namespace kstd
       string m_result{};
     };
 
-    struct string_iterator_writer : output_buffer
+    template<std::output_iterator<char> Output>
+    struct iterator_writer : output_buffer
     {
-      explicit string_iterator_writer(string::iterator iterator);
+      explicit iterator_writer(Output iterator)
+          : m_output{iterator}
+      {}
 
-      auto push(std::string_view text) -> void override;
-      auto push(char character) -> void override;
+      auto iterator() const -> Output
+      {
+        return m_output;
+      }
+
+      auto push(std::string_view text) -> void override
+      {
+        m_output = std::ranges::copy(text, m_output);
+      }
+
+      auto push(char character) -> void override
+      {
+        *m_output++ = character;
+      }
 
     private:
-      string::iterator m_iter{};
+      Output m_output{};
     };
 
   }  // namespace bits::format
@@ -62,6 +79,21 @@ namespace kstd
     return buffer.release();
   }
 
+  //! Format a given string with the provided arguments.
+  //!
+  //! @param iterator The iterator to write to.
+  //! @param format The format string.
+  //! @param args The arguments for the format string.
+  //! @return An iterator past the last element written.
+  template<std::output_iterator<char> Output, typename... ArgumentTypes>
+  auto format_to(Output iterator, format_string<std::type_identity_t<ArgumentTypes>...> format,
+                 ArgumentTypes &&... args) -> Output
+  {
+    auto buffer = bits::format::iterator_writer{iterator};
+    bits::format::vformat_to(buffer, format.str_view, std::forward<ArgumentTypes>(args)...);
+    return buffer.iterator();
+  }
+
 }  // namespace kstd
 
 #endif
\ No newline at end of file
-- 
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