#include "kapi/cio.hpp"

#include <kstd/format>
#include <kstd/os/print.hpp>
#include <kstd/print>

#include <array>
#include <cstddef>
#include <iterator>
#include <string_view>

namespace kstd::os
{

  namespace
  {
    struct write_buffer
    {
      using output_stream = kapi::cio::output_stream;

      constexpr auto static size = 128uz;

      write_buffer(write_buffer const &) = delete;
      write_buffer(write_buffer &&) = delete;
      auto operator=(write_buffer const &) -> write_buffer & = delete;
      auto operator=(write_buffer &&) -> write_buffer & = delete;

      explicit write_buffer(output_stream stream)
          : m_stream{stream}
      {}

      ~write_buffer() noexcept
      {
        flush();
      }

      auto flush() noexcept -> void
      {
        if (m_position > 0)
        {
          std::string_view chunk{m_buffer.data(), m_position};
          kapi::cio::write(m_stream, chunk);
          m_position = 0;
        }
      }

      auto static callback(void * object, std::string_view text) -> void
      {
        auto * self = static_cast<write_buffer *>(object);
        for (char const character : text)
        {
          if (self->m_position >= size)
          {
            self->flush();
          }
          self->m_buffer.at(self->m_position++) = character;
        }
      }

    private:
      output_stream m_stream;
      std::array<char, size> m_buffer{};
      std::size_t m_position{};
    };

  }  // namespace

  auto vprint(print_sink sink, std::string_view format, kstd::format_args args) -> void
  {
    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, .args = args};
    auto parse_context = kstd::format_parse_context{format, args.size()};

    auto it = parse_context.begin();
    auto end = parse_context.end();

    while (it != end)
    {
      if (*it != '{' && *it != '}')
      {
        auto start = it;
        while (it != end && *it != '{' && *it != '}')
        {
          std::advance(it, 1);
        }
        parse_context.advance_to(it);
        context.push(std::string_view(start, it - start));
        continue;
      }

      if (*it == '{')
      {
        std::advance(it, 1);
        if (it != end && *it == '{')
        {
          context.push('{');
          std::advance(it, 1);
          parse_context.advance_to(it);
          continue;
        }

        parse_context.advance_to(it);
        auto index = 0uz;

        if (it != end && *it >= '0' && *it <= '9')
        {
          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();
        }

        if (it != end && *it == ':')
        {
          std::advance(it, 1);
        }

        parse_context.advance_to(it);

        if (index < args.size())
        {
          auto const & arg = args[index];
          switch (arg.type)
          {
            case kstd::bits::format::arg_type::boolean:
            {
              auto fmt = kstd::formatter<bool>{};
              auto const parsed = fmt.parse(parse_context);
              parse_context.advance_to(parsed);
              fmt.format(arg.value.boolean, context);
              break;
            }
            case kstd::bits::format::arg_type::character:
            {
              auto fmt = kstd::formatter<char>{};
              auto const parsed = fmt.parse(parse_context);
              parse_context.advance_to(parsed);
              fmt.format(arg.value.character, context);
              break;
            }
            case kstd::bits::format::arg_type::integer:
            {
              auto fmt = kstd::formatter<long long>{};
              auto const parsed = fmt.parse(parse_context);
              parse_context.advance_to(parsed);
              fmt.format(arg.value.integer, context);
              break;
            }
            case kstd::bits::format::arg_type::unsigned_integer:
            {
              auto fmt = kstd::formatter<unsigned long long>{};
              auto const parsed = fmt.parse(parse_context);
              parse_context.advance_to(parsed);
              fmt.format(arg.value.unsigned_integer, context);
              break;
            }
            case kstd::bits::format::arg_type::string_view:
            {
              auto fmt = kstd::formatter<std::string_view>{};
              auto const parsed = fmt.parse(parse_context);
              parse_context.advance_to(parsed);
              fmt.format(arg.value.string_view, context);
              break;
            }
            case kstd::bits::format::arg_type::c_string:
            {
              auto fmt = kstd::formatter<char const *>{};
              auto const parsed = fmt.parse(parse_context);
              parse_context.advance_to(parsed);
              fmt.format(arg.value.c_string, context);
              break;
            }
            case kstd::bits::format::arg_type::pointer:
            {
              auto fmt = kstd::formatter<void const *>{};
              auto const parsed = fmt.parse(parse_context);
              parse_context.advance_to(parsed);
              fmt.format(arg.value.pointer, context);
              break;
            }
            case kstd::bits::format::arg_type::user_defined:
            {
              if (arg.value.user_defined.format)
              {
                arg.value.user_defined.format(arg.value.user_defined.pointer, parse_context, context);
              }
              else
              {
                context.push("{?}");
              }
              break;
            }
            default:
            {
              context.push("{fmt-err: unknown-type}");
              break;
            }
          }
        }
        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 if (*it == '}')
      {
        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);
        }
      }
    }
  }

}  // namespace kstd::os