// Copyright 2014 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_CSSOM_PROPERTY_VALUE_H_
#define COBALT_CSSOM_PROPERTY_VALUE_H_

#include <string>

#include "base/memory/ref_counted.h"
#include "cobalt/base/polymorphic_equatable.h"

namespace cobalt {
namespace cssom {

class PropertyValueVisitor;

// A base type for all values of CSS properties.
// All derived classes must be immutable.
class PropertyValue : public base::RefCountedThreadSafe<PropertyValue>,
                      public base::PolymorphicEquatable {
 public:
  virtual void Accept(PropertyValueVisitor* visitor) = 0;

  virtual std::string ToString() const = 0;

 protected:
  virtual ~PropertyValue() {}

  friend class base::RefCountedThreadSafe<PropertyValue>;
};

}  // namespace cssom
}  // namespace cobalt

#endif  // COBALT_CSSOM_PROPERTY_VALUE_H_