kstd: rework formatting to be closer to std

11 files changed, 692 insertions, 412 deletions

diff --git a/kapi/include/kapi/memory/address.hpp b/kapi/include/kapi/memory/address.hpp
index 587aeac..13bdf4c 100644
--- a/kapi/include/kapi/memory/address.hpp
+++ b/kapi/include/kapi/memory/address.hpp
@@ -229,13 +229,13 @@ namespace kstd
   {
     constexpr auto static suffix = Type == kapi::memory::address_type::linear ? "%lin" : "%phy";
 
-    constexpr auto parse(std::string_view context) -> std::string_view
+    constexpr auto parse(format_parse_context & context) -> format_parse_context::iterator
     {
       auto result = formatter<std::uintptr_t>::parse(context);
-      if (!this->specs.type)
+      if (!this->specifiers.type)
       {
-        this->specs.type = 'p';
-        this->specs.alternative_form = true;
+        this->specifiers.type = 'p';
+        this->specifiers.alternative_form = true;
       }
       return result;
     }
diff --git a/kernel/kstd/print.cpp b/kernel/kstd/print.cpp
index c7d26ba..44f80a7 100644
--- a/kernel/kstd/print.cpp
+++ b/kernel/kstd/print.cpp
@@ -70,74 +70,113 @@ namespace kstd::os
     auto writer = write_buffer{(sink == print_sink::stderr) ? kapi::cio::output_stream::stderr
                                                             : kapi::cio::output_stream::stdout};
     auto context = kstd::format_context{.writer = write_buffer::callback, .user_data = &writer};
+    auto parse_context = kstd::format_parse_context{format, args.size()};
 
-    auto current = format.begin();
-    auto end = format.end();
-    auto next_automatic_index = 0uz;
+    auto it = parse_context.begin();
+    auto end = parse_context.end();
 
-    while (current != end)
+    while (it != end)
     {
-      if (*current != '{')
+      if (*it != '{' && *it != '}')
       {
-        auto start = current;
-        while (current != end && *current != '{')
+        auto start = it;
+        while (it != end && *it != '{' && *it != '}')
         {
-          std::advance(current, 1);
+          std::advance(it, 1);
         }
-        context.push(std::string_view(start, current - start));
+        parse_context.advance_to(it);
+        context.push(std::string_view(start, it - start));
         continue;
       }
 
-      if (std::next(current) != end && *(std::next(current)) == '{')
+      if (*it == '{')
       {
-        context.push('{');
-        std::advance(current, 2);
-        continue;
-      }
+        std::advance(it, 1);
+        if (it != end && *it == '{')
+        {
+          context.push('{');
+          std::advance(it, 1);
+          parse_context.advance_to(it);
+          continue;
+        }
 
-      std::advance(current, 1);
+        parse_context.advance_to(it);
+        auto index = 0uz;
 
-      auto index = 0uz;
-      if (current != end && *current >= '0' && *current <= '9')
-      {
-        while (current != end && *current >= '0' && *current <= '9')
+        if (it != end && *it >= '0' && *it <= '9')
         {
-          index = index * 10 + static_cast<std::size_t>(*current - '0');
-          std::advance(current, 1);
+          while (it != end && *it >= '0' && *it <= '9')
+          {
+            index = index * 10 + static_cast<std::size_t>(*it - '0');
+            std::advance(it, 1);
+          }
+          parse_context.check_arg_id(index);
+        }
+        else
+        {
+          index = parse_context.next_arg_id();
         }
-      }
-      else
-      {
-        index = next_automatic_index++;
-      }
 
-      auto remaining_fmt = std::string_view{current, static_cast<std::size_t>(std::distance(current, end))};
+        if (it != end && *it == ':')
+        {
+          std::advance(it, 1);
+        }
 
-      auto const arg = args.get(index);
-      if (arg.format)
-      {
-        auto const after_specs = arg.format(arg.value, remaining_fmt, context);
-        auto const consumed = remaining_fmt.size() - after_specs.size();
-        std::advance(current, consumed);
-      }
-      else
-      {
-        context.push("{?}");
-        while (current != end && *current != '}')
-          std::advance(current, 1);
-      }
+        parse_context.advance_to(it);
 
-      if (current != end && *current == '}')
-      {
-        std::advance(current, 1);
+        if (index < args.size())
+        {
+          auto const & arg = args[index];
+          if (arg.format_function)
+          {
+            arg.format_function(arg.value_pointer, parse_context, context);
+          }
+          else
+          {
+            context.push("{?}");
+          }
+        }
+        else
+        {
+          context.push("{fmt-err: bound}");
+        }
+
+        it = parse_context.begin();
+
+        if (it != end && *it == '}')
+        {
+          std::advance(it, 1);
+          parse_context.advance_to(it);
+        }
+        else
+        {
+          context.push("{fmt-err: unconsumed}");
+          while (it != end && *it != '}')
+          {
+            std::advance(it, 1);
+          }
+
+          if (it != end)
+          {
+            std::advance(it, 1);
+            parse_context.advance_to(it);
+          }
+        }
       }
-      else
+      else if (*it == '}')
       {
-        context.push("{fmt-err}");
-        while (current != end && *current != '}')
-          std::advance(current, 1);
-        if (current != end)
-          std::advance(current, 1);
+        std::advance(it, 1);
+        if (it != end && *it == '}')
+        {
+          context.push('}');
+          std::advance(it, 1);
+          parse_context.advance_to(it);
+        }
+        else
+        {
+          context.push("{fmt-err: unescaped}");
+          parse_context.advance_to(it);
+        }
       }
     }
   }
diff --git a/libs/kstd/include/kstd/bits/format_args.hpp b/libs/kstd/include/kstd/bits/format_args.hpp
new file mode 100644
index 0000000..d236a23
--- /dev/null
+++ b/libs/kstd/include/kstd/bits/format_args.hpp
@@ -0,0 +1,62 @@
+#ifndef KSTD_BITS_FORMAT_ARGS_HPP
+#define KSTD_BITS_FORMAT_ARGS_HPP
+
+// IWYU pragma: private, include <kstd/format>
+
+#include "kstd/bits/format_context.hpp"
+
+#include <array>
+#include <cstddef>
+#include <span>
+#include <type_traits>
+
+namespace kstd
+{
+  template<typename>
+  struct formatter;
+
+  struct format_arg
+  {
+    using format_function_type = auto(void const * value, format_parse_context & parse_context,
+                                      format_context & context) -> void;
+
+    void const * value_pointer;
+    format_function_type * format_function;
+  };
+
+  using format_args = std::span<format_arg const>;
+
+  template<std::size_t Count>
+  struct format_arg_store
+  {
+    std::array<format_arg, Count> args{};
+  };
+
+  template<typename ValueType>
+  auto format_trampoline(void const * value_pointer, format_parse_context & parse_context, format_context & context)
+      -> void
+  {
+    auto typed_value_pointer = static_cast<ValueType const *>(value_pointer);
+    auto fmt = formatter<std::remove_cvref_t<ValueType>>{};
+    auto const it = fmt.parse(parse_context);
+    parse_context.advance_to(it);
+    fmt.format(*typed_value_pointer, context);
+  }
+
+  template<typename... Arguments>
+  [[nodiscard]] auto make_format_args(Arguments const &... args) noexcept -> format_arg_store<sizeof...(Arguments)>
+  {
+    if constexpr (sizeof...(Arguments) == 0)
+    {
+      return format_arg_store<0>{};
+    }
+    else
+    {
+      return format_arg_store<sizeof...(Arguments)>{std::array<format_arg, sizeof...(Arguments)>{
+        format_arg{static_cast<void const *>(&args), format_trampoline<Arguments>}...}};
+    }
+  }
+
+}  // namespace kstd
+
+#endif
\ No newline at end of file
diff --git a/libs/kstd/include/kstd/bits/format_context.hpp b/libs/kstd/include/kstd/bits/format_context.hpp
index b5c7d21..863047d 100644
--- a/libs/kstd/include/kstd/bits/format_context.hpp
+++ b/libs/kstd/include/kstd/bits/format_context.hpp
@@ -3,11 +3,100 @@
 
 // IWYU pragma: private, include <kstd/format>
 
+#include "kstd/os/error.hpp"
+
+#include <cstddef>
 #include <string_view>
 
 namespace kstd
 {
 
+  constexpr auto report_format_error(char const * message) -> void
+  {
+    if consteval
+    {
+      extern void compile_time_format_error_triggered(char const *);
+      compile_time_format_error_triggered(message);
+    }
+    else
+    {
+      kstd::os::panic("Error while formatting a string.");
+    }
+  }
+
+  struct format_parse_context
+  {
+    using iterator = std::string_view::const_iterator;
+
+    constexpr format_parse_context(std::string_view format, std::size_t argument_count)
+        : m_current(format.begin())
+        , m_end(format.end())
+        , m_argument_count(argument_count)
+    {}
+
+    [[nodiscard]] constexpr auto begin() const -> iterator
+    {
+      return m_current;
+    }
+
+    [[nodiscard]] constexpr auto end() const -> iterator
+    {
+      return m_end;
+    }
+
+    constexpr auto advance_to(iterator position) -> void
+    {
+      m_current = position;
+    }
+
+    constexpr auto next_arg_id() -> std::size_t
+    {
+      if (m_mode == index_mode::manual)
+      {
+        report_format_error("Cannot mix automatic and manual indexing.");
+      }
+
+      m_mode = index_mode::automatic;
+
+      if (m_next_argument_id >= m_argument_count)
+      {
+        report_format_error("Argument index out of bounds.");
+      }
+      return m_next_argument_id++;
+    }
+
+    constexpr auto check_arg_id(std::size_t index) -> void
+    {
+      if (m_mode == index_mode::automatic)
+      {
+        report_format_error("Cannot mix automatic and manual indexing.");
+      }
+
+      m_mode = index_mode::manual;
+
+      if (index >= m_argument_count)
+      {
+        report_format_error("Argument index out of bounds.");
+      }
+    }
+
+  private:
+    enum class index_mode
+    {
+      unknown,
+      automatic,
+      manual,
+    };
+
+    iterator m_current{};
+    iterator m_end{};
+    index_mode m_mode{};
+    std::size_t m_next_argument_id{};
+    std::size_t m_argument_count{};
+
+  public:
+  };
+
   struct format_context
   {
     using writer_function = void(void *, std::string_view);
diff --git a/libs/kstd/include/kstd/bits/format_specifiers.hpp b/libs/kstd/include/kstd/bits/format_specifiers.hpp
new file mode 100644
index 0000000..8fb50ef
--- /dev/null
+++ b/libs/kstd/include/kstd/bits/format_specifiers.hpp
@@ -0,0 +1,204 @@
+#ifndef KSTD_BITS_FORMAT_SPECS_HPP
+#define KSTD_BITS_FORMAT_SPECS_HPP
+
+// IWYU pragma: private
+
+#include "kstd/bits/format_context.hpp"
+
+#include <cstddef>
+#include <cstdint>
+#include <iterator>
+
+namespace kstd::bits
+{
+  enum struct alignment : std::uint8_t
+  {
+    none,
+    left,
+    right,
+    center,
+  };
+
+  enum struct sign_mode : std::uint8_t
+  {
+    none,
+    plus,
+    minus,
+    space,
+  };
+
+  enum struct width_mode : std::uint8_t
+  {
+    none,
+    static_value,
+    dynamic_argument_id
+  };
+
+  struct format_specifiers
+  {
+    char fill{' '};
+    alignment align{};
+    sign_mode sign{};
+    bool alternative_form{};
+    bool zero_pad{};
+
+    width_mode width_mode{};
+    std::size_t width_value{};
+    char type{};
+  };
+
+  struct format_padding
+  {
+    std::size_t left{};
+    std::size_t right{};
+  };
+
+  constexpr auto parse_format_specifiers(format_parse_context & context) -> format_specifiers
+  {
+    auto specifiers = format_specifiers{};
+    auto it = context.begin();
+    auto const end = context.end();
+
+    if (it != end && *it == '}')
+    {
+      return specifiers;
+    }
+
+    if (std::next(it) != end && ((*std::next(it)) == '<' || (*std::next(it)) == '>' || (*std::next(it)) == '^'))
+    {
+      specifiers.fill = *it;
+      switch (*std::next(it))
+      {
+        case '<':
+          specifiers.align = alignment::left;
+          break;
+        case '>':
+          specifiers.align = alignment::right;
+          break;
+        case '^':
+        default:
+          specifiers.align = alignment::center;
+          break;
+      }
+      std::advance(it, 2);
+    }
+    else if (*it == '<' || *it == '>' || *it == '^')
+    {
+      switch (*it)
+      {
+        case '<':
+          specifiers.align = alignment::left;
+          break;
+        case '>':
+          specifiers.align = alignment::right;
+          break;
+        case '^':
+        default:
+          specifiers.align = alignment::center;
+          break;
+      }
+      std::advance(it, 1);
+    }
+
+    if (it != end && (*it == '+' || *it == '-' || *it == ' '))
+    {
+      switch (*it)
+      {
+        case '+':
+          specifiers.sign = sign_mode::plus;
+          break;
+        case '-':
+          specifiers.sign = sign_mode::minus;
+          break;
+        case ' ':
+        default:
+          specifiers.sign = sign_mode::space;
+          break;
+      }
+      std::advance(it, 1);
+    }
+
+    if (it != end && *it == '#')
+    {
+      specifiers.alternative_form = true;
+      std::advance(it, 1);
+    }
+
+    if (it != end && *it == '0')
+    {
+      specifiers.zero_pad = true;
+      std::advance(it, 1);
+    }
+
+    if (it != end && *it == '{')
+    {
+      specifiers.width_mode = width_mode::dynamic_argument_id;
+      std::advance(it, 1);
+      auto argument_id = 0uz;
+
+      if (it != end && *it >= '0' && *it <= '9')
+      {
+        while (it != end && *it >= '0' && *it <= '9')
+        {
+          argument_id = argument_id * 10 + static_cast<std::size_t>(*it - '0');
+          std::advance(it, 1);
+        }
+        context.check_arg_id(argument_id);
+      }
+      else
+      {
+        argument_id = context.next_arg_id();
+      }
+
+      if (it == end || *it != '}')
+      {
+        report_format_error("Expected '}' for dynamic width.");
+      }
+      std::advance(it, 1);
+      specifiers.width_value = argument_id;
+    }
+    else if (it != end && *it >= '0' && *it <= '9')
+    {
+      specifiers.width_mode = width_mode::static_value;
+      while (it != end && *it >= '0' && *it <= '9')
+      {
+        specifiers.width_value = specifiers.width_value * 10 + static_cast<std::size_t>(*it - '0');
+        std::advance(it, 1);
+      }
+    }
+
+    context.advance_to(it);
+    return specifiers;
+  }
+
+  constexpr auto calculate_format_padding(std::size_t target_width, std::size_t content_length,
+                                          alignment requested_alignment, alignment default_alignment) -> format_padding
+  {
+    if (target_width <= content_length)
+    {
+      return {};
+    }
+
+    auto total_padding = target_width - content_length;
+    auto effective_alignment = (requested_alignment == alignment::none) ? default_alignment : requested_alignment;
+
+    switch (effective_alignment)
+    {
+      case alignment::center:
+      {
+        auto left = total_padding / 2;
+        auto right = total_padding - left;
+        return {left, right};
+      }
+      case alignment::left:
+        return {0, total_padding};
+      case alignment::right:
+      default:
+        return {total_padding, 0};
+        break;
+    }
+  }
+
+}  // namespace kstd::bits
+
+#endif
\ No newline at end of file
diff --git a/libs/kstd/include/kstd/bits/format_specs.hpp b/libs/kstd/include/kstd/bits/format_specs.hpp
deleted file mode 100644
index 092a875..0000000
--- a/libs/kstd/include/kstd/bits/format_specs.hpp
+++ /dev/null
@@ -1,104 +0,0 @@
-#ifndef KSTD_BITS_FORMAT_SPECS_HPP
-#define KSTD_BITS_FORMAT_SPECS_HPP
-
-// IWYU pragma: private
-
-#include <cstddef>
-#include <iterator>
-#include <string_view>
-
-namespace kstd::bits
-{
-
-  struct format_specs
-  {
-    std::size_t width{};
-    char fill{' '};
-    char type{};
-    bool align_left{};
-    bool sign_plus{};
-    bool sign_space{};
-    bool alternative_form{};
-    bool zero_pad{};
-  };
-
-  constexpr auto parse_specs(std::string_view string, format_specs & specs) -> std::string_view
-  {
-    auto current = string.begin();
-    auto end = string.end();
-
-    if (current == end || *current != ':')
-    {
-      return {current, end};
-    }
-
-    std::advance(current, 1);
-
-    if (current != end && std::next(current) != end && (*std::next(current) == '<' || *std::next(current) == '>'))
-    {
-      specs.fill = *current;
-      specs.align_left = *std::next(current) == '<';
-      std::advance(current, 2);
-    }
-    else if (current != end)
-    {
-      if (*current == '<')
-      {
-        specs.align_left = true;
-        std::advance(current, 1);
-      }
-      else if (*current == '>')
-      {
-        specs.align_left = false;
-        std::advance(current, 1);
-      }
-    }
-
-    if (current != end)
-    {
-      if (*current == '+')
-      {
-        specs.sign_plus = true;
-        std::advance(current, 1);
-      }
-      else if (*current == ' ')
-      {
-        specs.sign_space = true;
-        std::advance(current, 1);
-      }
-      else if (*current == '-')
-      {
-        std::advance(current, 1);
-      }
-    }
-
-    if (current != end && *current == '#')
-    {
-      specs.alternative_form = true;
-      std::advance(current, 1);
-    }
-
-    if (current != end && *current == '0')
-    {
-      specs.zero_pad = true;
-      std::advance(current, 1);
-    }
-
-    while (current != end && *current >= '0' && *current <= '9')
-    {
-      specs.width = specs.width * 10 + (*current - '0');
-      std::advance(current, 1);
-    }
-
-    if (current != end && *current != '}')
-    {
-      specs.type = *current;
-      std::advance(current, 1);
-    }
-
-    return {current, end};
-  }
-
-}  // namespace kstd::bits
-
-#endif
\ No newline at end of file
diff --git a/libs/kstd/include/kstd/bits/format_string.hpp b/libs/kstd/include/kstd/bits/format_string.hpp
index 3a15bf0..cbdfb7d 100644
--- a/libs/kstd/include/kstd/bits/format_string.hpp
+++ b/libs/kstd/include/kstd/bits/format_string.hpp
@@ -3,127 +3,114 @@
 
 // IWYU pragma: private, include <kstd/format>
 
-#include <algorithm>
+#include "kstd/bits/format_context.hpp"
+
 #include <cstddef>
-#include <iterator>
 #include <string_view>
+#include <type_traits>
 
 namespace kstd
 {
 
+  template<typename>
+  struct formatter;
+
   namespace bits
   {
-    auto invalid_format_string(char const *) -> void;
-
-    consteval auto validate_format_string(std::string_view string, std::size_t argument_count) -> void
+    template<typename... Args>
+    constexpr auto validate_argument(std::size_t target_index, format_parse_context & context) -> void
     {
-      auto next_automatic_index = 0uz;
-      auto placeholder_count = 0uz;
-      auto has_manual_index = false;
-      auto has_automatic_index = false;
+      auto found = false;
+      auto current_index = 0uz;
+
+      (..., [&] {
+        if (current_index == target_index && !found)
+        {
+          using decay_type = std::remove_cvref_t<Args>;
+          auto fmt = formatter<decay_type>{};
+
+          auto it = fmt.parse(context);
+          context.advance_to(it);
+          found = true;
+        }
+        ++current_index;
+      }());
+
+      if (!found)
+      {
+        report_format_error("Argument index out of bounds.");
+      }
+    }
+  }  // namespace bits
 
-      auto current = string.begin();
-      auto end = string.end();
+  template<typename... Args>
+  struct format_string
+  {
+    template<std::size_t Size>
+    consteval format_string(char const (&str)[Size]) noexcept(false)  // NOLINT
+        : str_view{str}
+    {
+      auto context = format_parse_context{str_view, sizeof...(Args)};
+      auto it = context.begin();
 
-      while (current != end)
+      while (it != context.end())
       {
-        if (*current == '{')
+        if (*it == '{')
         {
-          if (std::next(current) != end && *std::next(current) == '{')
+          ++it;
+          if (it != context.end() && *it == '{')
           {
-            std::advance(current, 2);
+            ++it;
+            context.advance_to(it);
             continue;
           }
 
-          std::advance(current, 1);
-
-          auto index = 0uz;
-          auto is_manual_index = false;
+          context.advance_to(it);
+          auto argument_id = 0uz;
 
-          if (current != end && *current >= '0' && *current <= '9')
+          if (it != context.end() && *it >= '0' && *it <= '9')
           {
-            is_manual_index = true;
-            while (current != end && *current >= '0' && *current <= '9')
+            while (it != context.end() && *it >= '0' && *it <= '9')
             {
-              index = index * 10 + (*current - '0');
-              std::advance(current, 1);
-            }
-          }
-
-          if (is_manual_index)
-          {
-            placeholder_count = std::max(placeholder_count, index + 1);
-            if (has_automatic_index)
-            {
-              invalid_format_string("Cannot mix automatic and manual indexing.");
-            }
-            has_manual_index = true;
-            if (index >= argument_count)
-            {
-              invalid_format_string("Argument index out of range");
+              argument_id = argument_id * 10 + static_cast<std::size_t>(*it - '0');
+              ++it;
             }
+            context.check_arg_id(argument_id);
+            context.advance_to(it);
           }
           else
           {
-            if (has_manual_index)
-            {
-              invalid_format_string("Cannot mix automatic and manual indexing.");
-            }
-            has_automatic_index = true;
-            ++placeholder_count;
-            if (next_automatic_index >= argument_count)
-            {
-              invalid_format_string("Not enough arguments provided for format string.");
-            }
-            index = next_automatic_index++;
+            argument_id = context.next_arg_id();
           }
 
-          while (current != end && *current != '}')
+          if (it != context.end() && *it == ':')
           {
-            std::advance(current, 1);
+            ++it;
+            context.advance_to(it);
           }
 
-          if (current == end)
+          bits::validate_argument<Args...>(argument_id, context);
+
+          it = context.begin();
+          if (it == context.end() || *it != '}')
           {
-            invalid_format_string("Unexpected end of format string.");
+            report_format_error("Missing closing '}' in format string.");
           }
-          std::advance(current, 1);
         }
-        else if (*current == '}')
+        else if (*it == '}')
         {
-          if (std::next(current) != end && *std::next(current) == '}')
+          ++it;
+          if (it != context.end() && *it == '}')
           {
-            std::advance(current, 2);
-            continue;
+            report_format_error("Unescaped '}' in format string.");
           }
-          invalid_format_string("Unexpected '}' in format string.");
-        }
-        else
-        {
-          std::advance(current, 1);
         }
-      }
-      if (argument_count < placeholder_count)
-      {
-        invalid_format_string("Not enough arguments provided for format string.");
-      }
-      else if (argument_count > placeholder_count)
-      {
-        invalid_format_string("Too many arguments provided for format string.");
+        ++it;
+        context.advance_to(it);
       }
     }
-  }  // namespace bits
-
-  template<typename... Args>
-  struct format_string
-  {
-    std::string_view str;
 
-    consteval format_string(char const * format)
-        : str{format}
-    {
-      bits::validate_format_string(str, sizeof...(Args));
-    }
+    std::string_view str_view;
   };
 
 }  // namespace kstd
diff --git a/libs/kstd/include/kstd/bits/formatter.hpp b/libs/kstd/include/kstd/bits/formatter.hpp
index 7c9c31d..e9a45e0 100644
--- a/libs/kstd/include/kstd/bits/formatter.hpp
+++ b/libs/kstd/include/kstd/bits/formatter.hpp
@@ -3,8 +3,9 @@
 
 // IWYU pragma: private, include <kstd/format>
 
-#include <kstd/bits/format_context.hpp>
-#include <kstd/bits/format_specs.hpp>
+#include "kstd/bits/format_context.hpp"
+#include "kstd/bits/format_specifiers.hpp"
+
 #include <kstd/os/error.hpp>
 
 #include <array>
@@ -21,30 +22,98 @@
 namespace kstd
 {
 
-  template<typename T>
+  template<typename>
   struct formatter;
 
+  template<>
+  struct formatter<std::string_view>
+  {
+    constexpr auto parse(format_parse_context & context) -> format_parse_context::iterator
+    {
+      auto it = context.begin();
+
+      if (it != context.end() && *it == 's')
+      {
+        ++it;
+      }
+
+      if (it != context.end() && *it != '}')
+      {
+        report_format_error("Invalid specifier for string_view.");
+      }
+      return it;
+    }
+
+    auto format(std::string_view const & string, format_context & context) const -> void
+    {
+      context.push(string);
+    }
+  };
+
+  template<>
+  struct formatter<char const *> : formatter<std::string_view>
+  {
+    auto format(char const * string, format_context & context) const -> void
+    {
+      formatter<std::string_view>::format(string ? std::string_view{string} : "(null)", context);
+    }
+  };
+
   template<std::integral T>
   struct formatter<T>
   {
-    bits::format_specs specs{};
+    bits::format_specifiers specifiers{};
+
+    constexpr auto static maximum_digits = 80;
 
-    constexpr auto parse(std::string_view context) -> std::string_view
+    enum struct base
     {
-      return bits::parse_specs(context, specs);
+      bin = 2,
+      oct = 8,
+      dec = 10,
+      hex = 16,
+    };
+
+    constexpr auto parse(format_parse_context & context) -> format_parse_context::iterator
+    {
+      specifiers = bits::parse_format_specifiers(context);
+
+      auto it = context.begin();
+      auto const end = context.end();
+
+      if (it != end && *it != '}')
+      {
+        if (*it == 'b' || *it == 'B' || *it == 'd' || *it == 'o' || *it == 'x' || *it == 'X' || *it == 'p')
+        {
+          specifiers.type = *it;
+          std::advance(it, 1);
+        }
+        else
+        {
+          report_format_error("Invalid type specifier for integral type.");
+        }
+      }
+
+      if (it != end && *it != '}')
+      {
+        report_format_error("Missing terminating '}' in format string.");
+      }
+
+      return it;
     }
 
     auto format(T value, format_context & context) const -> void
     {
-      enum struct base
+      auto final_width = 0uz;
+      if (specifiers.width_mode == bits::width_mode::static_value)
       {
-        bin = 2,
-        oct = 8,
-        dec = 10,
-        hex = 16,
-      };
-
-      constexpr auto static maximum_digits = 80;
+        final_width = specifiers.width_value;
+      }
+      else if (specifiers.width_mode == bits::width_mode::dynamic_argument_id)
+      {
+        // TODO: implement argument references so we can read the dynamic width argument.
+        final_width = 0;
+      }
 
       using unsigned_T = std::make_unsigned_t<T>;
       auto absolute_value = static_cast<unsigned_T>(value);
@@ -55,11 +124,11 @@ namespace kstd
         if (value < 0)
         {
           is_negative = true;
-          absolute_value = 0 - value;
+          absolute_value = 0 - static_cast<unsigned_T>(value);
         }
       }
 
-      auto const base = [type = specs.type] -> auto {
+      auto const base = [type = specifiers.type] -> auto {
         switch (type)
         {
           case 'x':
@@ -77,7 +146,7 @@ namespace kstd
       }();
 
       auto buffer = std::array<char, maximum_digits>{};
-      auto digits = (specs.type == 'X') ? "0123456789ABCDEF" : "0123456789abcdef";
+      auto digits = (specifiers.type == 'X') ? "0123456789ABCDEF" : "0123456789abcdef";
       auto current = buffer.rbegin();
 
       if (absolute_value == 0)
@@ -95,21 +164,22 @@ namespace kstd
         }
       }
 
+      auto content_length = static_cast<std::size_t>(std::distance(buffer.rbegin(), current));
       auto prefix = std::array<char, 2>{'0', '\0'};
       auto prefix_length = 0uz;
-      if (specs.alternative_form)
+      if (specifiers.alternative_form)
       {
         switch (base)
         {
           case base::bin:
-            prefix[1] = specs.type == 'B' ? 'B' : 'b';
+            prefix[1] = specifiers.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[1] = specifiers.type == 'X' ? 'X' : 'x';
             prefix_length = 2;
             break;
           default:
@@ -122,53 +192,50 @@ namespace kstd