Define an enum that can be converted to a string

enum_with_string.h

//
// Created by shawnfeng([email protected]) on 2021/11/1.
//
#pragma once

#include <map>
#include <string>
#include <vector>

// reference:
// https://stackoverflow.com/questions/207976/how-to-easily-map-c-enums-to-strings
// https://stackoverflow.com/questions/201593/is-there-a-simple-way-to-convert-c-enum-to-string#201792

namespace enum_string {

template <typename T>
static inline void split_string_for_each(const std::string &str,
                                         const std::string &delimiter,
                                         const T &foreach_function,
                                         ssize_t max_number = -1) {
  ssize_t num = 0;
  std::string::size_type start;
  std::string::size_type end = -1;
  while (true) {
    start = str.find_first_not_of(delimiter, end + 1);
    if (start == std::string::npos) break;  // over

    end = str.find_first_of(delimiter, start + 1);

    if (end == std::string::npos) {
      foreach_function(num, str.substr(start));
      break;
    }
    foreach_function(num, str.substr(start, end - start));
    ++num;

    if (max_number > 0 && num == max_number) break;
  }
}

/**
 * Strip function, delete the specified characters on both sides of the string.
 */
inline std::string &strip(std::string &s,
                          const std::string &characters = " \t\r\n") {
  s.erase(0, s.find_first_not_of(characters));
  return s.erase(s.find_last_not_of(characters) + 1);
}

template <typename UnderlyingType>
static inline std::map<UnderlyingType, std::string> ParserEnumDefine(
    const std::string &name, const std::string &define_str) {
  UnderlyingType cur_num = 0;
  std::string cur_item_str;
  std::map<UnderlyingType, std::string> result_map;
  split_string_for_each(define_str, ",", [&](int num, const std::string &str) {
    split_string_for_each(
        str, "=",
        [&](int num, const std::string &str) {
          if (num == 0) cur_item_str = str;
          if (num == 1) cur_num = std::stoi(str);
        },
        2);
    result_map.emplace(cur_num, name + "::" + strip(cur_item_str));
    cur_num++;
  });
  return result_map;
}

}  // namespace enum_string

/**
 * Example:
 * @code
#include <iostream>

#include "enum_with_string.h"

ENUM_WITH_STRING(Animal, dog, cat, monkey = 50, fish, human = 100, duck)
int main() {
  std::cout << to_string(Animal::dog) << std::endl;
  std::cout << to_string(Animal::cat) << std::endl;
  std::cout << to_string(Animal::monkey) << std::endl;
  std::cout << to_string(Animal::fish) << std::endl;
  std::cout << to_string(Animal::human) << std::endl;
  std::cout << to_string(Animal::duck) << std::endl;
}
 * @endcode
 */
#define ENUM_WITH_STRING(Name, ...)                                          \
  enum class Name { __VA_ARGS__, __COUNT };                                  \
  static inline const std::string &to_string(Name value) {                   \
    using underlying_type = std::underlying_type<Name>::type;                \
    static const auto map =                                                  \
        enum_string::ParserEnumDefine<underlying_type>(#Name, #__VA_ARGS__); \
    static const std::string cannot_converted =                              \
        "Cannot be converted to string";                                     \
    underlying_type under_value = static_cast<underlying_type>(value);       \
    if (map.count(under_value))                                              \
      return map.at(under_value);                                            \
    else                                                                     \
      return cannot_converted;                                               \
  }