module;

#include <asio.hpp>

#include <format>
#include <string_view>

export module ttwhy.routers:echo;

import ttwhy;
import ttwhy.scanners;

namespace ttwhy::routers
{

  using namespace std::string_view_literals;

  constexpr auto vte_backspace_sequence = "\b \b"sv;
  constexpr auto vte_newline_sequence = "\r\n"sv;
  constexpr auto vte_horizontal_tab_sequqnce = "\t"sv;

  export template<typename StreamType>
  struct echo
  {
    using terminal_policy = scanners::xterm_policy;

    explicit echo(StreamType & stream)
        : m_output_stream{stream}
    {}

    auto process(scanners::input_event event) -> asio::awaitable<void>
    {
      co_await std::visit(
          [&](auto && event) -> asio::awaitable<void> {
            using event_type = std::decay_t<decltype(event)>;

            if constexpr (std::same_as<scanners::character_event, event_type>)
            {
              co_await process_character(event.value);
            }
            else if constexpr (std::same_as<scanners::control_event, event_type>)
            {
              co_await process_control_key(event.key);
            }
            else if constexpr (std::same_as<scanners::navigation_event, event_type>)
            {
              co_await process_navigation_key(event);
            }
          },
          event);
    }

  private:
    auto process_character(char character) -> asio::awaitable<void>
    {
      co_await asio::async_write(m_output_stream, asio::buffer(&character, 1), asio::as_tuple(asio::use_awaitable));
    }

    auto process_control_key(scanners::control_key key) -> asio::awaitable<void>
    {
      switch (key)
      {
        case scanners::control_key::backspace:
          co_await asio::async_write(m_output_stream, asio::buffer(vte_backspace_sequence),
                                     asio::as_tuple(asio::use_awaitable));
          break;
        case scanners::control_key::enter:
          co_await asio::async_write(m_output_stream, asio::buffer(vte_newline_sequence),
                                     asio::as_tuple(asio::use_awaitable));
          break;
        case scanners::control_key::tab:
          co_await asio::async_write(m_output_stream, asio::buffer(vte_horizontal_tab_sequqnce),
                                     asio::as_tuple(asio::use_awaitable));
          break;
        default:
          co_await asio::async_write(m_output_stream, asio::buffer(std::format("{{CTRL:{}}}", std::to_underlying(key))),
                                     asio::as_tuple(asio::use_awaitable));
          break;
      };
    }

    auto process_navigation_key(scanners::navigation_event event) -> asio::awaitable<void>
    {
      auto modifiers = std::to_underlying(event.modifiers);

      switch (event.key)
      {
        case scanners::navigation_key::delete_key:
        {
          auto message = std::format("{{DEL, MODS:{}}}", static_cast<int>(modifiers));
          co_await asio::async_write(m_output_stream, asio::buffer(message), asio::as_tuple(asio::use_awaitable));
          break;
        }
        default:
        {
          auto message = std::format("{{NAV:{}, MODS:{}}}", static_cast<int>(event.key), static_cast<int>(modifiers));
          co_await asio::async_write(m_output_stream, asio::buffer(message), asio::as_tuple(asio::use_awaitable));
        }
      }
    }

    StreamType & m_output_stream;
  };

}  // namespace ttwhy::routers