// Copyright 2015 The Chromium Authors. All rights reserved.
// Copyright (C) 2016-2021 Apple Inc. All rights reserved.
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#pragma once

#include "CSSValue.h"
#include "CSSValueKeywords.h"

namespace WebCore {

class CSSParserToken;
class CSSParserTokenRange;
class CSSVariableData;
struct CSSParserContext;

namespace Style {
class BuilderState;
}

enum CSSPropertyID : uint16_t;

class CSSVariableReferenceValue : public CSSValue {
public:
    static Ref<CSSVariableReferenceValue> create(const CSSParserTokenRange&, const CSSParserContext&);
    static Ref<CSSVariableReferenceValue> create(Ref<CSSVariableData>&&);

    bool equals(const CSSVariableReferenceValue&) const;
    String customCSSText() const;

    RefPtr<CSSVariableData> resolveVariableReferences(Style::BuilderState&) const;
    const CSSParserContext& context() const;

    RefPtr<CSSValue> resolveSingleValue(Style::BuilderState&, CSSPropertyID) const;
    RefPtr<CSSValue> resolveSubstitutionValue(Style::BuilderState&, CSSPropertyID, CSSPropertyID shorthandID) const;

    // The maximum number of tokens that may be produced by a var() reference or var() fallback value.
    // https://drafts.csswg.org/css-variables/#long-variables
    static constexpr size_t maxSubstitutionTokens = 65536;
    
    const CSSVariableData& data() const { return m_data.get(); }

private:
    explicit CSSVariableReferenceValue(Ref<CSSVariableData>&&);

    std::optional<Vector<CSSParserToken>> resolveTokenRange(CSSParserTokenRange, Style::BuilderState&) const;
    bool resolveVariableReference(CSSParserTokenRange, CSSValueID, Vector<CSSParserToken>&, Style::BuilderState&) const;
    enum class FallbackResult : uint8_t { None, Valid, Invalid };
    std::pair<FallbackResult, Vector<CSSParserToken>> resolveVariableFallback(const AtomString& variableName, CSSParserTokenRange, CSSValueID functionId, Style::BuilderState&) const;

    void cacheSimpleReference();
    RefPtr<CSSVariableData> tryResolveSimpleReference(Style::BuilderState&) const;

    template<typename ParseFunction> RefPtr<CSSValue> resolveAndCacheValue(Style::BuilderState&, CSSPropertyID, CSSPropertyID shorthandID, ParseFunction&&) const;

    Ref<CSSVariableData> m_data;
    mutable String m_stringValue;

    // For quicky resolving simple var(--foo) values.
    struct SimpleReference {
        AtomString name;
        CSSValueID functionId;
    };
    std::optional<SimpleReference> m_simpleReference;

    struct ResolvedValue {
        WTF_MAKE_STRUCT_FAST_ALLOCATED;

        RefPtr<CSSValue> value;
        CSSPropertyID propertyID;
        CSSPropertyID shorthandID;
        RefPtr<CSSVariableData> dependencyData;
    };
    mutable std::unique_ptr<ResolvedValue> m_cachedResolvedValue;
};

} // namespace WebCore

SPECIALIZE_TYPE_TRAITS_CSS_VALUE(CSSVariableReferenceValue, isVariableReferenceValue())
