/*
 * Copyright 2015 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef COBALT_SCRIPT_UNION_TYPE_INTERNAL_H_
#define COBALT_SCRIPT_UNION_TYPE_INTERNAL_H_

// Details of union type implementation. See union_type.h

#include <limits>

#include "base/memory/ref_counted.h"
#include "base/optional.h"
#include "cobalt/base/enable_if.h"
#include "cobalt/base/type_id.h"

namespace cobalt {
namespace script {
namespace internal {

template <typename T>
struct UnionTypeDefaultTraits {
  typedef const T& ArgType;
  typedef T& ReturnType;
  typedef const T& ConstReturnType;
  static base::TypeId GetTypeID() { return base::GetTypeId<T>(); }
  static const bool is_interface_type = false;
  static const bool is_numeric_type = false;
  static const bool is_boolean_type = false;
  static const bool is_string_type = false;
};

// Default traits for types with no specialization
template <typename T, typename = void>
struct UnionTypeTraits : UnionTypeDefaultTraits<T> {
  // This assert will only be evaluated if the template is instantiated.
  COMPILE_ASSERT(sizeof(T) == 0, UnionTypeNotImplementedForType);
};

template <typename T>
struct UnionTypeTraits<scoped_refptr<T> >
    : UnionTypeDefaultTraits<scoped_refptr<T> > {
  static base::TypeId GetTypeID() { return base::GetTypeId<T>(); }
  static const bool is_interface_type = true;
};

template <>
struct UnionTypeTraits<std::string> : UnionTypeDefaultTraits<std::string> {
  static const bool is_string_type = true;
};

// std::numeric_limits<T>::digits will be 0 for non-specialized types, 1 for
// bool, and something larger for the other types.
template <typename T>
struct UnionTypeTraits<
    T, typename base::enable_if<(std::numeric_limits<T>::digits > 1)>::type>
    : UnionTypeDefaultTraits<T> {
  typedef T ArgType;
  typedef T ReturnType;
  typedef T ConstReturnType;
  static const bool is_numeric_type = true;
};

template <>
struct UnionTypeTraits<bool> : UnionTypeDefaultTraits<bool> {
  typedef bool ArgType;
  typedef bool ReturnType;
  typedef bool ConstReturnType;
  static const bool is_boolean_type = true;
};

// Explicitly blacklist nullable types. None of the union members should be
// nullable. If the union has a nullable member, then the whole union type
// should be declared nullable such as base::optional<base::UnionTypeN<...> >
template <typename T>
struct UnionTypeTraits<base::optional<T> > : UnionTypeDefaultTraits<T> {
  // This assert will only be evaluated if the template is instantiated.
  COMPILE_ASSERT(sizeof(T) == 0, NullableTypesAreNotPermittedInUnionss);
};

}  // namespace internal
}  // namespace script
}  // namespace cobalt

#endif  // COBALT_SCRIPT_UNION_TYPE_INTERNAL_H_