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 <string_view>
#include <type_traits>
#include <utility>
#include <variant>
#include <vector>

#include "string_utils/any_of.h"
#include "string_utils/forwards.h"
#include "string_utils/traits.h"

#define SAFE_NUMBER_PARSE(func, ...)                                           \
  [](char const * in, char ** out) { return func(in, out, ##__VA_ARGS__); }

namespace string_utils::detail {
template <typename Actual, typename Out>
bool ctor_cast(Out & out, std::string_view str) noexcept {
  auto [rval, found] = cast<Actual>(str);
  if (found) { out = Out(std::move(rval)); }
  return found;
}

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

template <typename T, typename F>
bool cast_number(std::string_view str, T & to, F func) noexcept {
  char * counter = nullptr;
  to = func(str.data(), &counter);
  return counter == str.end();
}

inline std::vector<std::string_view> keyval(std::string_view input) noexcept {
  if (size_t const pos = input.find('='); pos < input.size()) {
    return {input.substr(0, pos), input.substr(pos + 1)};
  }
  return {input};
}

inline bool cast_bool(bool & out, std::string_view str) noexcept {
  if (any_of(str, "true", "TRUE", "YES", "1")) {
    out = true;
    return true;
  } else if (any_of(str, "false", "FALSE", "NO", "0")) {
    out = false;
    return true;
  }
  return false;
}
}

// This should be placed last in the file
namespace string_utils {

template <typename Out> bool cast(Out & out, std::string_view str) noexcept {
  if constexpr (std::is_same_v<Out, long>) {
    return detail::cast_number(str, out, SAFE_NUMBER_PARSE(std::strtol, 10));
  } else if constexpr (std::is_same_v<Out, unsigned long>) {
    return detail::cast_number(str, out, SAFE_NUMBER_PARSE(std::strtoul, 10));
  } else if constexpr (std::is_same_v<Out, long long>) {
    return detail::cast_number(str, out, SAFE_NUMBER_PARSE(std::strtoll, 10));
  } else if constexpr (std::is_same_v<Out, unsigned long long>) {
    return detail::cast_number(str, out, SAFE_NUMBER_PARSE(std::strtoull, 10));
  } else if constexpr (std::is_same_v<Out, float>) {
    return detail::cast_number(str, out, SAFE_NUMBER_PARSE(std::strtof));
  } else if constexpr (std::is_same_v<Out, double>) {
    return detail::cast_number(str, out, SAFE_NUMBER_PARSE(std::strtod));
  } else if constexpr (std::is_same_v<Out, long double>) {
    return detail::cast_number(str, out, SAFE_NUMBER_PARSE(std::strtold));
  } else if constexpr (std::is_same_v<Out, bool>) {
    return detail::cast_bool(out, str);
  } else if constexpr (std::is_same_v<Out, char>) {
    out = str[0];
    return str.size() == 1;
  } else if constexpr (std::is_constructible_v<Out, std::string_view>) {
    out = Out(str);
    return true;
  } else if constexpr (std::is_integral_v<Out>) {
    using V = std::conditional_t<std::is_unsigned_v<Out>, unsigned long, long>;
    auto [tmp, success] = cast<V>(str);
    out = static_cast<Out>(tmp);
    return success && tmp == static_cast<V>(out);
  } else {
    static_assert(detail::always_false<Out>{}, "No match for cast(string)");
  }
}

template <typename... Ts>
bool cast(std::variant<Ts...> & out, std::string_view str) noexcept {
  return (detail::ctor_cast<Ts>(out, str) || ...);
}

template <typename Out>
bool cast(std::optional<Out> & out, std::string_view str) noexcept {
  return detail::ctor_cast<Out>(out, str) || true;
}

template <typename Out>
bool cast(Out & out, std::vector<std::string_view> const & strs) noexcept {
  if constexpr (detail::is_associative_v<Out>) {
    for (auto elem : strs) {
      auto [tmp, success] =
          cast<typename Out::value_type>(detail::keyval(elem));
      if (!success) { return false; }
      out.insert(std::move(tmp));
    }
    return true;
  } else if constexpr (detail::is_container_v<Out>) {
    for (auto elem : strs) {
      auto [tmp, success] = cast<typename Out::value_type>(elem);
      if (!success) { return false; }
      out.insert(out.end(), std::move(tmp));
    }
    return true;
  } else if constexpr (detail::is_tuple_v<Out>) {
    constexpr size_t N = std::tuple_size_v<Out>;
    return strs.size() == N &&
           detail::cast_tuple(strs, out, std::make_index_sequence<N>{});
  } else {
    static_assert(detail::always_false<Out>{},
                  "No match for cast(vector<string>)");
  }
}

template <typename T> std::pair<T, bool> cast(std::string_view str) noexcept {
  std::pair<detail::decay_t<T>, bool> rval;
  using ::string_utils::cast;
  rval.second = cast(rval.first, str);
  return rval;
}

template <typename T, typename S>
std::pair<T, bool> cast(std::vector<S> const & strs) noexcept {
  std::vector<std::string_view> tmp{strs.begin(), strs.end()};
  std::pair<detail::decay_t<T>, bool> rval;
  using ::string_utils::cast;
  rval.second = cast(rval.first, tmp);
  return rval;
}
}

#undef CAST_NUMBER_IMPL