CSSSelector.h

/*
 * Copyright (C) 1999-2003 Lars Knoll (knoll@kde.org)
 *               1999 Waldo Bastian (bastian@kde.org)
 * Copyright (C) 2004-2022 Apple Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#pragma once

#include "CSSSelectorEnums.h"
#include "QualifiedName.h"
#include "RenderStyleConstants.h"
#include <wtf/EnumTraits.h>
#include <wtf/FixedVector.h>

namespace WebCore {

class CSSSelectorList;
struct CSSSelectorParserContext;

struct PossiblyQuotedIdentifier {
    AtomString identifier;
    bool wasQuoted { false };

    bool isNull() const { return identifier.isNull(); }
};

enum class SelectorSpecificityIncrement {
    ClassA = 0x10000,
    ClassB = 0x100,
    ClassC = 1
};

// Selector for a StyleRule.
DECLARE_ALLOCATOR_WITH_HEAP_IDENTIFIER(CSSSelectorRareData);
class CSSSelector {
    WTF_MAKE_FAST_ALLOCATED;
public:
    CSSSelector() = default;
    CSSSelector(const CSSSelector&);
    explicit CSSSelector(const QualifiedName&, bool tagIsForNamespaceRule = false);

    ~CSSSelector();

    // Re-create selector text from selector's data.
    String selectorText(StringView separator = { }, StringView rightSide = { }) const;

    unsigned computeSpecificity() const;
    std::array<uint8_t, 3> computeSpecificityTuple() const;
    unsigned specificityForPage() const;

    bool visitAllSimpleSelectors(auto& apply) const;

    bool hasExplicitNestingParent() const;
    bool hasExplicitPseudoClassScope() const;
    void resolveNestingParentSelectors(const CSSSelectorList& parent);
    void replaceNestingParentByPseudoClassScope();

    using PseudoClass = CSSSelectorPseudoClass;
    using PseudoElement = CSSSelectorPseudoElement;

    // How the attribute value has to match. Default is Exact.
    enum class Match : uint8_t {
        Unknown = 0,
        Tag,
        Id,
        Class,
        Exact,
        Set,
        List,
        Hyphen,
        PseudoClass,
        PseudoElement,
        Contain, // css3: E[foo*="bar"]
        Begin, // css3: E[foo^="bar"]
        End, // css3: E[foo$="bar"]
        PagePseudoClass,
        NestingParent, // &
        HasScope, // matches the :has() scope
        ForgivingUnknown,
        ForgivingUnknownNestContaining
    };

    enum class Relation : uint8_t {
        Subselector,
        DescendantSpace,
        Child,
        DirectAdjacent,
        IndirectAdjacent,
        ShadowDescendant,
        ShadowPartDescendant,
        ShadowSlotted
    };

    enum class PagePseudoClass : uint8_t {
        First,
        Left,
        Right,
    };

    enum AttributeMatchType { CaseSensitive, CaseInsensitive };

    static PseudoId pseudoId(PseudoElement);
    static bool isPseudoClassEnabled(PseudoClass, const CSSSelectorParserContext&);
    static bool isPseudoElementEnabled(PseudoElement, StringView, const CSSSelectorParserContext&);
    static std::optional<PseudoElement> parsePseudoElementName(StringView, const CSSSelectorParserContext&);
    static bool pseudoClassRequiresArgument(PseudoClass);
    static bool pseudoElementRequiresArgument(PseudoElement);
    static bool pseudoClassMayHaveArgument(PseudoClass);
    static bool pseudoElementMayHaveArgument(PseudoElement);

    static const ASCIILiteral selectorTextForPseudoClass(PseudoClass);
    static const ASCIILiteral nameForUserAgentPartLegacyAlias(StringView);

    // Selectors are kept in an array by CSSSelectorList.
    // The next component of the selector is the next item in the array.
    const CSSSelector* tagHistory() const { return m_isLastInTagHistory ? nullptr : this + 1; }
    const CSSSelector* firstInCompound() const;

    const QualifiedName& tagQName() const;
    const AtomString& tagLowercaseLocalName() const;

    const AtomString& value() const;
    const AtomString& serializingValue() const;
    const QualifiedName& attribute() const;
    const AtomString& argument() const { return m_hasRareData ? m_data.rareData->argument : nullAtom(); }
    bool attributeValueMatchingIsCaseInsensitive() const;
    const FixedVector<PossiblyQuotedIdentifier>* argumentList() const { return m_hasRareData ? &m_data.rareData->argumentList : nullptr; }
    const CSSSelectorList* selectorList() const { return m_hasRareData ? m_data.rareData->selectorList.get() : nullptr; }
    CSSSelectorList* selectorList() { return m_hasRareData ? m_data.rareData->selectorList.get() : nullptr; }

    bool matchNth(int count) const;
    int nthA() const;
    int nthB() const;

    bool hasDescendantRelation() const { return relation() == Relation::DescendantSpace; }
    bool hasDescendantOrChildRelation() const { return relation() == Relation::Child || hasDescendantRelation(); }

    PseudoClass pseudoClass() const;
    PseudoElement pseudoElement() const;
    PagePseudoClass pagePseudoClass() const;

    bool matchesPseudoElement() const;
    bool isSiblingSelector() const;
    bool isAttributeSelector() const;

    Relation relation() const { return static_cast<Relation>(m_relation); }
    Match match() const { return static_cast<Match>(m_match); }

    bool isLastInSelectorList() const { return m_isLastInSelectorList; }
    bool isFirstInTagHistory() const { return m_isFirstInTagHistory; }
    bool isLastInTagHistory() const { return m_isLastInTagHistory; }

    // FIXME: These should ideally be private, but CSSSelectorList and StyleRule use them.
    void setLastInSelectorList() { m_isLastInSelectorList = true; }
    void setNotFirstInTagHistory() { m_isFirstInTagHistory = false; }
    void setNotLastInTagHistory() { m_isLastInTagHistory = false; }

    bool isForPage() const { return m_isForPage; }

    // Implicit means that this selector is not author/UA written.
    bool isImplicit() const { return m_isImplicit; }

private:
    friend class MutableCSSSelector;

    void setValue(const AtomString&, bool matchLowerCase = false);

    void setAttribute(const QualifiedName&, AttributeMatchType);
    void setNth(int a, int b);
    void setArgument(const AtomString&);
    void setArgumentList(FixedVector<PossiblyQuotedIdentifier>);
    void setSelectorList(std::unique_ptr<CSSSelectorList>);

    void setPseudoClass(PseudoClass);
    void setPseudoElement(PseudoElement);
    void setPagePseudoClass(PagePseudoClass);

    void setRelation(Relation);
    void setMatch(Match);

    void setForPage() { m_isForPage = true; }
    void setImplicit() { m_isImplicit = true; }

    unsigned simpleSelectorSpecificityForPage() const;
    CSSSelector* tagHistory() { return m_isLastInTagHistory ? nullptr : this + 1; }

    unsigned m_relation : 4 { enumToUnderlyingType(Relation::DescendantSpace) };
    mutable unsigned m_match : 5 { enumToUnderlyingType(Match::Unknown) };
    mutable unsigned m_pseudoType : 8 { 0 }; // PseudoType.
    // 17 bits
    unsigned m_isLastInSelectorList : 1 { false };
    unsigned m_isFirstInTagHistory : 1 { true };
    unsigned m_isLastInTagHistory : 1 { true };
    unsigned m_hasRareData : 1 { false };
    unsigned m_isForPage : 1 { false };
    unsigned m_tagIsForNamespaceRule : 1 { false };
    unsigned m_caseInsensitiveAttributeValueMatching : 1 { false };
    unsigned m_isImplicit : 1 { false };
    // 25 bits
#if !ASSERT_WITH_SECURITY_IMPLICATION_DISABLED
    unsigned m_destructorHasBeenCalled : 1 { false };
#endif

    CSSSelector& operator=(const CSSSelector&) = delete;
    CSSSelector(CSSSelector&&) = delete;

    struct RareData : public RefCounted<RareData> {
        WTF_MAKE_STRUCT_FAST_ALLOCATED_WITH_HEAP_IDENTIFIER(CSSSelectorRareData);
        static Ref<RareData> create(AtomString);
        WEBCORE_EXPORT ~RareData();

        bool matchNth(int count);

        // For quirks mode, class and id are case-insensitive. In the case where uppercase
        // letters are used in quirks mode, |m_matchingValue| holds the lowercase class/id
        // and |m_serializingValue| holds the original string.
        AtomString matchingValue;
        AtomString serializingValue;

        int a { 0 }; // Used for :nth-*
        int b { 0 }; // Used for :nth-*
        QualifiedName attribute; // used for attribute selector
        AtomString argument; // Used for :contains and :nth-*
        FixedVector<PossiblyQuotedIdentifier> argumentList; // Used for :lang and ::part arguments.
        std::unique_ptr<CSSSelectorList> selectorList; // Used for :is(), :matches(), and :not().

        Ref<RareData> deepCopy() const;

    private:
        RareData(AtomString&& value);
        RareData(const RareData& other);
    };
    void createRareData();

    union DataUnion {
        AtomStringImpl* value { nullptr };
        QualifiedName::QualifiedNameImpl* tagQName;
        RareData* rareData;
    } m_data;
};

inline bool operator==(const AtomString& a, const PossiblyQuotedIdentifier& b) { return a == b.identifier; }
inline bool operator==(const PossiblyQuotedIdentifier& a, const AtomString& b) { return a.identifier == b; }

inline const QualifiedName& CSSSelector::attribute() const
{
    ASSERT(isAttributeSelector());
    ASSERT(m_hasRareData);
    return m_data.rareData->attribute;
}

inline bool CSSSelector::matchesPseudoElement() const
{
    return match() == Match::PseudoElement;
}

static inline bool pseudoClassIsRelativeToSiblings(CSSSelector::PseudoClass type)
{
    return type == CSSSelector::PseudoClass::Empty
        || type == CSSSelector::PseudoClass::FirstChild
        || type == CSSSelector::PseudoClass::FirstOfType
        || type == CSSSelector::PseudoClass::LastChild
        || type == CSSSelector::PseudoClass::LastOfType
        || type == CSSSelector::PseudoClass::OnlyChild
        || type == CSSSelector::PseudoClass::OnlyOfType
        || type == CSSSelector::PseudoClass::NthChild
        || type == CSSSelector::PseudoClass::NthOfType
        || type == CSSSelector::PseudoClass::NthLastChild
        || type == CSSSelector::PseudoClass::NthLastOfType;
}

static inline bool isTreeStructuralPseudoClass(CSSSelector::PseudoClass type)
{
    return pseudoClassIsRelativeToSiblings(type) || type == CSSSelector::PseudoClass::Root;
}

inline bool isLogicalCombinationPseudoClass(CSSSelector::PseudoClass pseudoClass)
{
    switch (pseudoClass) {
    case CSSSelector::PseudoClass::Is:
    case CSSSelector::PseudoClass::Where:
    case CSSSelector::PseudoClass::WebKitAny:
    case CSSSelector::PseudoClass::Not:
    case CSSSelector::PseudoClass::Has:
        return true;
    default:
        return false;
    }
}

inline bool CSSSelector::isSiblingSelector() const
{
    return relation() == Relation::DirectAdjacent
        || relation() == Relation::IndirectAdjacent
        || (match() == CSSSelector::Match::PseudoClass && pseudoClassIsRelativeToSiblings(pseudoClass()));
}

inline bool CSSSelector::isAttributeSelector() const
{
    return match() == CSSSelector::Match::Exact
        || match() == CSSSelector::Match::Set
        || match() == CSSSelector::Match::List
        || match() == CSSSelector::Match::Hyphen
        || match() == CSSSelector::Match::Contain
        || match() == CSSSelector::Match::Begin
        || match() == CSSSelector::Match::End;
}

inline void CSSSelector::setValue(const AtomString& value, bool matchLowerCase)
{
    ASSERT(match() != Match::Tag);
    auto matchingValue = matchLowerCase ? value.convertToASCIILowercase() : value;
    if (!m_hasRareData && matchingValue != value)
        createRareData();

    // Need to do ref counting manually for the union.
    if (!m_hasRareData) {
        if (m_data.value)
            m_data.value->deref();
        m_data.value = value.impl();
        m_data.value->ref();
        return;
    }

    m_data.rareData->matchingValue = WTFMove(matchingValue);
    m_data.rareData->serializingValue = value;
}

inline CSSSelector::~CSSSelector()
{
    ASSERT_WITH_SECURITY_IMPLICATION(!m_destructorHasBeenCalled);
#if !ASSERT_WITH_SECURITY_IMPLICATION_DISABLED
    m_destructorHasBeenCalled = true;
#endif
    if (m_hasRareData) {
        m_data.rareData->deref();
        m_data.rareData = nullptr;
        m_hasRareData = false;
    } else if (match() == Match::Tag) {
        m_data.tagQName->deref();
        m_data.tagQName = nullptr;
        m_match = enumToUnderlyingType(Match::Unknown);
    } else if (m_data.value) {
        m_data.value->deref();
        m_data.value = nullptr;
    }
}

inline const QualifiedName& CSSSelector::tagQName() const
{
    return *reinterpret_cast<const QualifiedName*>(&m_data.tagQName);
}

inline const AtomString& CSSSelector::tagLowercaseLocalName() const
{
    return tagQName().localNameLowercase();
}

inline const AtomString& CSSSelector::value() const
{
    ASSERT(match() != Match::Tag);
    if (m_hasRareData)
        return m_data.rareData->matchingValue;

    // AtomString is really just an AtomStringImpl* so the cast below is safe.
    return *reinterpret_cast<const AtomString*>(&m_data.value);
}

inline const AtomString& CSSSelector::serializingValue() const
{
    ASSERT(match() != Match::Tag);
    if (m_hasRareData)
        return m_data.rareData->serializingValue;

    // AtomString is really just an AtomStringImpl* so the cast below is safe.
    return *reinterpret_cast<const AtomString*>(&m_data.value);
}

inline bool CSSSelector::attributeValueMatchingIsCaseInsensitive() const
{
    return m_caseInsensitiveAttributeValueMatching;
}

inline auto CSSSelector::pseudoClass() const -> PseudoClass
{
    ASSERT(match() == Match::PseudoClass);
    return static_cast<PseudoClass>(m_pseudoType);
}

inline void CSSSelector::setPseudoClass(PseudoClass pseudoClass)
{
    m_pseudoType = enumToUnderlyingType(pseudoClass);
    ASSERT(static_cast<PseudoClass>(m_pseudoType) == pseudoClass);
}

inline auto CSSSelector::pseudoElement() const -> PseudoElement
{
    ASSERT(match() == Match::PseudoElement);
    return static_cast<PseudoElement>(m_pseudoType);
}

inline void CSSSelector::setPseudoElement(PseudoElement pseudoElement)
{
    m_pseudoType = enumToUnderlyingType(pseudoElement);
    ASSERT(static_cast<PseudoElement>(m_pseudoType) == pseudoElement);
}

inline auto CSSSelector::pagePseudoClass() const -> PagePseudoClass
{
    ASSERT(match() == Match::PagePseudoClass);
    return static_cast<PagePseudoClass>(m_pseudoType);
}

inline void CSSSelector::setPagePseudoClass(PagePseudoClass pagePseudoClass)
{
    m_pseudoType = enumToUnderlyingType(pagePseudoClass);
    ASSERT(static_cast<PagePseudoClass>(m_pseudoType) == pagePseudoClass);
}

inline void CSSSelector::setRelation(Relation relation)
{
    m_relation = enumToUnderlyingType(relation);
}

inline void CSSSelector::setMatch(Match match)
{
    m_match = enumToUnderlyingType(match);
}

} // namespace WebCore