#pragma once

#include <charconv>
#include <concepts>
#include <expected>
#include <string>
#include <string_view>
#include <system_error>
#include <type_traits>

#include <modulus/result.hpp>

#include <vamp_zero/errors.hpp>


namespace vamp_zero {

template <std::integral VALUE>
  requires(!std::is_same_v<VALUE, std::bool_t>)
auto parse_integer(std::string_view text, std::string_view name) -> std::expected<VALUE, modulus::error> {
  auto invalid = [&](std::string_view reason) {
    return modulus::fail<VALUE>(
      make_error(error_code::INVALID_ARGUMENT, std::string{name} + " " + std::string{reason}));
  };
  if (text.empty()) {
    return invalid("must be an integer");
  }
  auto value = VALUE{};
  auto end = text.data() + text.size();
  auto parsed = std::from_chars(text.data(), end, value);
  if (parsed.ec == std::errc::result_out_of_range) {
    return invalid("is out of range");
  }
  if (parsed.ec != std::errc{} || parsed.ptr != end) {
    return invalid("must be an integer");
  }
  return modulus::success(value);
}

}