cpp-reflection/include/reflection/typecast.h

//
//  typecast.h
//  reflection
//
//  Created by Sam Jaffe on 7/4/22.
//  Copyright © 2022 Sam Jaffe. All rights reserved.
//

#pragma once

#include <functional>
#include <typeindex>
#include <unordered_map>
#include <utility>

#include "reflection/forward.h"
#include "reflection/object.h"

namespace reflection {
template <typename T> class TypeCast {
public:
  static bool has_cast(Object const & obj) { return get_.count(obj.type()); }

  static T get(Object const & obj) { return get_.at(obj.type())(obj); }

  static void set(Object & obj, T const & value) {
    set_.at(obj.type())(obj, value);
  }

  operator bool() const { return true; }

  template <typename I, typename O, typename S>
  TypeCast & bind(T (*to)(I), O (*from)(S)) {
    return bind(std::function(to), std::function(from));
  }

  template <typename I, typename O, typename S>
  TypeCast & bind(std::function<T(I)> to, std::function<O(S)> from) {
    bind_impl(to, from);
    TypeCast<std::decay_t<I>>().template bind_impl(from, to);
    return *this;
  }

  template <typename V> TypeCast & bind() {
    if constexpr (!std::is_same_v<V, T>) {
      bind_impl<V>();
      TypeCast<V>().template bind_impl<T>();
    }
    return *this;
  }

  template <typename V1, typename V2, typename... Vs> TypeCast & bind() {
    return bind<V1>().template bind<V2, Vs...>();
  }

private:
  template <typename I, typename O, typename S>
  void bind_impl(std::function<T(I)> to, std::function<O(S)> from) {
    static_assert(std::is_same_v<std::decay_t<S>, T>,
                  "this types must be compatible");
    static_assert(std::is_same_v<std::decay_t<I>, std::decay_t<I>>,
                  "cast types must be compatible");
    using V = std::decay_t<I>;
    get_.emplace(typeid(V),
                 [to](auto & obj) { return to(static_cast<V const &>(obj)); });
    set_.emplace(typeid(V), [from](auto & obj, T const & val) {
      static_cast<V &>(obj) = from(val);
    });
  }

  template <typename V> void bind_impl() {
    get_.emplace(typeid(V), [](auto & obj) {
      return static_cast<T>(static_cast<V const &>(obj));
    });
    set_.emplace(typeid(V), [](auto & obj, T val) {
      static_cast<V &>(obj) = static_cast<V>(val);
    });
  }

private:
  template <typename S> friend class TypeCast;
  static TypeMap<std::function<T(Object const &)>> get_;
  static TypeMap<std::function<void(Object &, T const &)>> set_;
};

template <typename T>
TypeMap<std::function<T(Object const &)>> TypeCast<T>::get_;
template <typename T>
TypeMap<std::function<void(Object &, T const &)>> TypeCast<T>::set_;
}

#if defined REFLECTION_TYPE_CAST_IMPLEMENTATION
namespace reflection {
INSTANTIATE_REFLECTION_TYPECAST(bool);
INSTANTIATE_REFLECTION_TYPECAST(int16_t);
INSTANTIATE_REFLECTION_TYPECAST(int32_t);
INSTANTIATE_REFLECTION_TYPECAST(int64_t);
INSTANTIATE_REFLECTION_TYPECAST(uint16_t);
INSTANTIATE_REFLECTION_TYPECAST(uint32_t);
INSTANTIATE_REFLECTION_TYPECAST(uint64_t);
INSTANTIATE_REFLECTION_TYPECAST(float);
INSTANTIATE_REFLECTION_TYPECAST(double);
INSTANTIATE_REFLECTION_TYPECAST(long double);
INSTANTIATE_REFLECTION_TYPECAST(std::string);

// Bind boolean types to all integer types
REFLECTION_TYPE_CAST(bool)
    .bind<int16_t, int32_t, int64_t>()
    .bind<uint16_t, uint32_t, uint64_t>();

// Bind all integer types (wider than 1byte) to each other.
REFLECTION_TYPE_CAST(int32_t)
    .bind<int16_t, int32_t, int64_t>()
    .bind<uint16_t, uint32_t, uint64_t>();

REFLECTION_TYPE_CAST(uint32_t)
    .bind<int16_t, int32_t, int64_t>()
    .bind<uint16_t, uint32_t, uint64_t>();

REFLECTION_TYPE_CAST(int16_t)
    .bind<int16_t, int32_t, int64_t>()
    .bind<uint16_t, uint32_t, uint64_t>();

REFLECTION_TYPE_CAST(uint16_t)
    .bind<int16_t, int32_t, int64_t>()
    .bind<uint16_t, uint32_t, uint64_t>();

REFLECTION_TYPE_CAST(int64_t)
    .bind<int16_t, int32_t, int64_t>()
    .bind<uint16_t, uint32_t, uint64_t>();

REFLECTION_TYPE_CAST(uint64_t)
    .bind<int16_t, int32_t, int64_t>()
    .bind<uint16_t, uint32_t, uint64_t>();

// Mututally bind all floating point numbers
REFLECTION_TYPE_CAST(float).bind<float, double, long double>();
REFLECTION_TYPE_CAST(double).bind<float, double, long double>();
REFLECTION_TYPE_CAST(long double).bind<float, double, long double>();
}
#endif