From 0c8e77b367ca617beb2c30cd7e032cd9b24aeea4 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Thu, 18 Dec 2025 13:59:50 +0100
Subject: kstd: finish integral formatting implementation

---
 libs/kstd/include/kstd/bits/format_context.hpp |   2 +-
 libs/kstd/include/kstd/bits/formatter.hpp      | 104 +++++++++++++++----------
 2 files changed, 62 insertions(+), 44 deletions(-)

diff --git a/libs/kstd/include/kstd/bits/format_context.hpp b/libs/kstd/include/kstd/bits/format_context.hpp
index 69f0629..b5c7d21 100644
--- a/libs/kstd/include/kstd/bits/format_context.hpp
+++ b/libs/kstd/include/kstd/bits/format_context.hpp
@@ -12,7 +12,7 @@ namespace kstd
   {
     using writer_function = void(void *, std::string_view);
 
-    writer_function writer;
+    writer_function * writer;
     void * user_data;
 
     constexpr auto push(std::string_view string) -> void
diff --git a/libs/kstd/include/kstd/bits/formatter.hpp b/libs/kstd/include/kstd/bits/formatter.hpp
index ce29b59..0fea5ef 100644
--- a/libs/kstd/include/kstd/bits/formatter.hpp
+++ b/libs/kstd/include/kstd/bits/formatter.hpp
@@ -12,6 +12,7 @@
 #include <iterator>
 #include <string_view>
 #include <type_traits>
+#include <utility>
 
 namespace kstd
 {
@@ -31,7 +32,17 @@ namespace kstd
 
     auto format(T value, format_context & context) -> void
     {
-      using unsigned_T = std::make_unsigned<T>;
+      enum struct base
+      {
+        bin = 2,
+        oct = 8,
+        dec = 10,
+        hex = 16,
+      };
+
+      constexpr auto static maximum_digits = 80;
+
+      using unsigned_T = std::make_unsigned_t<T>;
       auto absolute_value = static_cast<unsigned_T>(value);
       auto is_negative = false;
 
@@ -50,31 +61,33 @@ namespace kstd
           case 'x':
           case 'X':
           case 'p':
-            return 16;
+            return base::hex;
           case 'b':
           case 'B':
-            return 2;
+            return base::bin;
           case 'o':
-            return 8;
+            return base::oct;
           default:
-            return 10;
+            return base::dec;
         }
       }();
 
-      auto buffer = std::array<char, 80>{};
-      auto digits = (base == 16) ? "0123456789abcdef" : "0123456789";
+      auto buffer = std::array<char, maximum_digits>{};
+      auto digits = (base == base::hex) ? "0123456789abcdef" : "0123456789";
       auto current = buffer.rbegin();
 
       if (absolute_value == 0)
       {
-        *std::next(current) = '0';
+        *current = '0';
+        std::advance(current, 1);
       }
       else
       {
         while (absolute_value != 0)
         {
-          *std::next(current) = digits[absolute_value % base];
-          absolute_value /= base;
+          *current = digits[absolute_value % std::to_underlying(base)];
+          std::advance(current, 1);
+          absolute_value /= std::to_underlying(base);
         }
       }
 
@@ -82,19 +95,21 @@ namespace kstd
       auto prefix_length = 0uz;
       if (specs.alternative_form && value != 0)
       {
-        if (base == 16)
+        switch (base)
         {
-          prefix[1] = specs.type == 'X' ? 'X' : 'x';
-          prefix_length = 2;
-        }
-        else if (base == 8)
-        {
-          prefix_length = 1;
-        }
-        else if (base == 2)
-        {
-          prefix[1] = specs.type == 'B' ? 'B' : 'b';
-          prefix_length = 2;
+          case base::bin:
+            prefix[1] = specs.type == 'B' ? 'B' : 'b';
+            prefix_length = 2;
+            break;
+          case base::oct:
+            prefix_length = 1;
+            break;
+          case base::hex:
+            prefix[1] = specs.type == 'X' ? 'X' : 'x';
+            prefix_length = 2;
+            break;
+          default:
+            break;
         }
       }
 
@@ -156,38 +171,41 @@ namespace kstd
 
   struct format_arg
   {
+    using formatting_function = std::string_view(void const *, std::string_view, format_context &);
+
     void const * value;
-    auto (*format)(void const *, std::string_view, format_context &) -> std::string_view;
+    formatting_function * format;
   };
 
-  template<typename T>
-  auto format_dispatcher(void const * val, std::string_view spec, format_context & ctx) -> std::string_view
+  struct format_args
   {
-    formatter<T> f;
-    auto const remainder = f.parse(spec);
-    f.format(*static_cast<T const *>(val), ctx);
-    return remainder;
-  }
-
-  class format_args
-  {
-    format_arg const * args_;
-    std::size_t count_;
-
-  public:
-    constexpr format_args(format_arg const * args, std::size_t count)
-        : args_(args)
-        , count_(count)
+    constexpr format_args(format_arg const * args, std::size_t number_of_args)
+        : m_args(args)
+        , m_number_of_args(number_of_args)
     {}
 
-    [[nodiscard]] constexpr auto get(std::size_t idx) const -> format_arg
+    [[nodiscard]] constexpr auto get(std::size_t index) const -> format_arg
     {
-      if (idx >= count_)
+      if (index >= m_number_of_args)
         return {.value = nullptr, .format = nullptr};
-      return args_[idx];
+      // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-pointer-arithmetic)
+      return m_args[index];
     }
+
+  private:
+    format_arg const * m_args;
+    std::size_t m_number_of_args;
   };
 
+  template<typename T>
+  auto format_dispatcher(void const * value, std::string_view format_spec, format_context & context) -> std::string_view
+  {
+    auto formatter_for_T = formatter<T>{};
+    auto const remainder = formatter_for_T.parse(format_spec);
+    formatter_for_T.format(*static_cast<T const *>(value), context);
+    return remainder;
+  }
+
 }  // namespace kstd
 
 #endif
\ No newline at end of file
-- 
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