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#pragma once

#include <array>
#include <cstddef>
#include <string_view>
#include <utility>

namespace OpenVic::ConstexprIntToStr {
   template<class T, T... values1, T... values2>
   constexpr decltype(auto) append_sequence(std::integer_sequence<T, values1...>, std::integer_sequence<T, values2...>) {
      return std::integer_sequence<T, values1..., values2...> {};
   }

   template<class sequence_t>
   struct string_sequence_to_view;

   template<char... chars>
   struct string_sequence_to_view<std::integer_sequence<char, chars...>> {
      static constexpr decltype(auto) get() {
         return std::string_view { c_str };
      }

      static constexpr const char c_str[] { chars..., char {} };
   };

   template<std::size_t value>
   constexpr decltype(auto) integer_to_string_sequence() {
      constexpr auto digits = []() {
         return "0123456789abcdefghijklmnopqrstuvwxyz";
      };

      constexpr std::size_t remainder = value % 10;
      constexpr std::size_t next_value = value / 10;

      if constexpr (next_value != 0) {
         return append_sequence(integer_to_string_sequence<next_value>(), std::integer_sequence<char, digits()[remainder]> {});
      } else {
         return std::integer_sequence<char, digits()[remainder]> {};
      }
   }
   template<std::size_t i>
   constexpr std::string_view make_string() {
      return string_sequence_to_view<decltype(integer_to_string_sequence<i>())> {}.c_str;
   }

   template<std::size_t... ManyIntegers>
   constexpr auto generate_itosv_array(std::integer_sequence<std::size_t, ManyIntegers...>) {
      return std::array<std::string_view, sizeof...(ManyIntegers)> { make_string<ManyIntegers>()... };
   }

   // Make array of N string views, countings up from 0 to N - 1
   template<std::size_t N>
   constexpr auto make_itosv_array() {
      return generate_itosv_array(std::make_integer_sequence<std::size_t, N>());
   }
}