// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef Nullable_h
#define Nullable_h

#include "platform/heap/Handle.h"
#include "wtf/Assertions.h"

namespace blink {

enum class UnionTypeConversionMode {
  Nullable,
  NotNullable,
};

template <typename T>
class Nullable {
  DISALLOW_NEW();

 public:
  Nullable() : m_value(), m_isNull(true) {}

  Nullable(std::nullptr_t) : m_value(), m_isNull(true) {}

  Nullable(const T& value) : m_value(value), m_isNull(false) {}

  Nullable(const Nullable& other)
      : m_value(other.m_value), m_isNull(other.m_isNull) {}

  Nullable& operator=(const Nullable& other) {
    m_value = other.m_value;
    m_isNull = other.m_isNull;
    return *this;
  }

  Nullable& operator=(std::nullptr_t) {
    m_value = T();
    m_isNull = true;
    return *this;
  }

  void set(const T& value) {
    m_value = value;
    m_isNull = false;
  }

  void set(std::nullptr_t) {
    m_value = T();
    m_isNull = true;
  }

  const T& get() const {
    ASSERT(!m_isNull);
    return m_value;
  }
  T& get() {
    ASSERT(!m_isNull);
    return m_value;
  }
  bool isNull() const { return m_isNull; }

  explicit operator bool() const { return !m_isNull; }

  bool operator==(const Nullable& other) const {
    return (m_isNull && other.m_isNull) ||
           (!m_isNull && !other.m_isNull && m_value == other.m_value);
  }

  DEFINE_INLINE_TRACE() { TraceIfNeeded<T>::trace(visitor, m_value); }

 private:
  T m_value;
  bool m_isNull;
};

}  // namespace blink

#endif  // Nullable_h