cpp-string-utils/include/string_utils/cast.h

//
//  cast.h
//  string-utils
//
//  Created by Sam Jaffe on 2/13/21.
//  Copyright © 2021 Sam Jaffe. All rights reserved.
//

#pragma once

#include <cstdlib>
#include <optional>
#include <string>
#include <type_traits>
#include <utility>
#include <variant>
#include <vector>

#include "any_of.h"

#define CAST_NUMBER_IMPL(type, func, ...)                                      \
  inline bool cast(std::string const & str, type & to) {                       \
    char * rval;                                                               \
    to = func(str.c_str(), &rval, ##__VA_ARGS__);                              \
    return rval == str.c_str() + str.length();                                 \
  }

namespace string_utils { namespace traits {
template <typename T, typename = void> struct is_stringy : std::false_type {};

template <typename> struct is_variant : std::false_type {};
template <typename... Ts>
struct is_variant<std::variant<Ts...>> : std::true_type {};

template <typename T>
struct is_stringy<
    T, std::enable_if_t<std::is_constructible<T, std::string const &>{} &&
                        !is_variant<T>{}>> : std::true_type {};

}}

namespace string_utils {
template <typename T> std::pair<T, bool> cast(std::string const & str);
template <typename T> bool cast(std::string const & str, std::optional<T> & to);
template <typename... Ts>
bool cast(std::string const & str, std::variant<Ts...> & to);

template <typename... Ts>
bool cast(std::vector<std::string> const & str, std::tuple<Ts...> & to);
template <typename K, typename V>
bool cast(std::vector<std::string> const & str, std::pair<K, V> & to);
}

namespace string_utils {
template <typename T, typename = std::enable_if_t<traits::is_stringy<T>{}>>
bool cast(std::string const & str, T & to) {
  to = T(str);
  return true;
}

CAST_NUMBER_IMPL(long, std::strtol, 10);
CAST_NUMBER_IMPL(long long, std::strtoll, 10);
CAST_NUMBER_IMPL(float, std::strtof);
CAST_NUMBER_IMPL(double, std::strtod);
CAST_NUMBER_IMPL(long double, std::strtold);

inline bool cast(std::string const & str, int & to) {
  long tmp;
  bool rval = cast(str, tmp);
  to = static_cast<int>(tmp);
  return rval && tmp == static_cast<long>(to);
}

inline bool cast(std::string const & str, bool & to) {
  if (any_of(str, "true", "TRUE", "YES", "1")) {
    to = true;
    return true;
  } else if (any_of(str, "false", "FALSE", "NO", "0")) {
    to = false;
    return true;
  }
  return false;
}
}

namespace string_utils::detail {
template <typename T, typename... Ts>
bool cast_alternative(std::string const & str, std::variant<Ts...> & to) {
  auto [rval, found] = cast<T>(str);
  if (found) { to = std::move(rval); }
  return found;
}

template <typename Tuple, size_t... Is>
bool cast_tuple(std::vector<std::string> const & str, Tuple & to,
                std::index_sequence<Is...>) {
  return ((cast(str[Is], std::get<Is>(to))) && ...);
}

template <typename Tuple>
bool cast_tuple(std::vector<std::string> const & str, Tuple & to) {
  constexpr size_t N = std::tuple_size_v<Tuple>;
  return str.size() == N && cast_tuple(str, to, std::make_index_sequence<N>{});
}
}

namespace string_utils {

template <typename... Ts>
bool cast(std::string const & str, std::variant<Ts...> & to) {
  return (detail::cast_alternative<Ts>(str, to) || ...);
}

template <typename T>
bool cast(std::string const & str, std::optional<T> & to) {
  auto [value, success] = cast<T>(str);
  if (success) { to = std::move(value); }
  return true;
}

template <typename... Ts>
bool cast(std::vector<std::string> const & str, std::tuple<Ts...> & to) {
  return detail::cast_tuple(str, to);
}

template <typename K, typename V>
bool cast(std::vector<std::string> const & str, std::pair<K, V> & to) {
  return detail::cast_tuple(str, to);
}

}

// This should be placed last in the file
namespace string_utils {
template <typename T> std::pair<T, bool> cast(std::string const & str) {
  using string_utils::cast;
  std::pair<T, bool> rval;
  rval.second = cast(str, rval.first);
  return rval;
}
}

#undef CAST_NUMBER_IMPL