/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
 * met:
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 * notice, this list of conditions and the following disclaimer.
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 * in the documentation and/or other materials provided with the
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
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 */

#ifndef AnimatableValue_h
#define AnimatableValue_h

#include "core/css/CSSValue.h"
#include "wtf/RefCounted.h"

namespace WebCore {

class CSSValue;

class AnimatableValue : public RefCounted<AnimatableValue> {
public:
    virtual ~AnimatableValue() { }
    static PassRefPtr<AnimatableValue> create(CSSValue*);
    virtual PassRefPtr<CSSValue> toCSSValue() const = 0;

    static const AnimatableValue* neutralValue();
    virtual bool isNeutral() const { return false; }

    static PassRefPtr<AnimatableValue> interpolate(const AnimatableValue*, const AnimatableValue*, double fraction);
    // For noncommutative values read add(A, B) to mean the value A with B composed onto it.
    static PassRefPtr<AnimatableValue> add(const AnimatableValue*, const AnimatableValue*);

protected:
    enum AnimatableType {
        TypeNeutral,
        TypeNumber,
        TypeUnknown,
    };

    AnimatableValue(AnimatableType type) : m_type(type) { }

    bool isSameType(const AnimatableValue* value) const
    {
        ASSERT(value);
        return value->m_type == m_type;
    }

    virtual PassRefPtr<AnimatableValue> interpolateTo(const AnimatableValue*, double fraction) const = 0;
    static PassRefPtr<AnimatableValue> defaultInterpolateTo(const AnimatableValue* left, const AnimatableValue* right, double fraction) { return takeConstRef((fraction < 0.5) ? left : right); }

    // For noncommutative values read A->addWith(B) to mean the value A with B composed onto it.
    virtual PassRefPtr<AnimatableValue> addWith(const AnimatableValue*) const = 0;
    static PassRefPtr<AnimatableValue> defaultAddWith(const AnimatableValue* left, const AnimatableValue* right) { return takeConstRef(right); }

    template <class T>
    static PassRefPtr<T> takeConstRef(const T* value) { return PassRefPtr<T>(const_cast<T*>(value)); }

    AnimatableType m_type;
};

} // namespace WebCore

#endif // AnimatableValue_h