/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
 * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
 * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
 * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
 * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
 * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
 * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
 * Copyright (C) Research In Motion Limited 2011. 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.
 */

#include "config.h"
#include "core/css/SelectorChecker.h"

#include "HTMLNames.h"
#include "core/css/CSSSelector.h"
#include "core/css/CSSSelectorList.h"
#include "core/css/SiblingTraversalStrategies.h"
#include "core/dom/Document.h"
#include "core/dom/Element.h"
#include "core/dom/FullscreenElementStack.h"
#include "core/dom/NodeRenderStyle.h"
#include "core/dom/Text.h"
#include "core/dom/shadow/InsertionPoint.h"
#include "core/dom/shadow/ShadowRoot.h"
#include "core/editing/FrameSelection.h"
#include "core/html/HTMLAnchorElement.h"
#include "core/html/HTMLDocument.h"
#include "core/html/HTMLFrameElementBase.h"
#include "core/html/HTMLInputElement.h"
#include "core/html/HTMLOptGroupElement.h"
#include "core/html/HTMLOptionElement.h"
#include "core/html/parser/HTMLParserIdioms.h"
#include "core/inspector/InspectorInstrumentation.h"
#include "core/page/FocusController.h"
#include "core/page/Frame.h"
#include "core/page/Page.h"
#include "core/platform/ScrollableArea.h"
#include "core/platform/ScrollbarTheme.h"
#include "core/rendering/RenderObject.h"
#include "core/rendering/RenderScrollbar.h"
#include "core/rendering/style/RenderStyle.h"

#include "core/html/track/WebVTTElement.h"

namespace WebCore {

using namespace HTMLNames;

SelectorChecker::SelectorChecker(Document& document, Mode mode)
    : m_strictParsing(!document.inQuirksMode())
    , m_documentIsHTML(document.isHTMLDocument())
    , m_mode(mode)
{
}

static bool matchesCustomPseudoElement(const Element* element, const CSSSelector* selector)
{
    ShadowRoot* root = element->containingShadowRoot();
    if (!root)
        return false;

    if (selector->pseudoType() != CSSSelector::PseudoPart) {
        const AtomicString& pseudoId = selector->pseudoType() == CSSSelector::PseudoWebKitCustomElement ? element->shadowPseudoId() : element->pseudo();
        if (pseudoId != selector->value())
            return false;
        if (selector->pseudoType() == CSSSelector::PseudoWebKitCustomElement && root->type() != ShadowRoot::UserAgentShadowRoot)
            return false;
        return true;
    }

    if (element->part() != selector->argument())
        return false;
    if (selector->isMatchUserAgentOnly() && root->type() != ShadowRoot::UserAgentShadowRoot)
        return false;
    return true;
}

Element* SelectorChecker::parentElement(const SelectorCheckingContext& context) const
{
    // CrossesBoundary means we don't care any context.scope. So we can walk up from a shadow root to its shadow host.
    if ((context.behaviorAtBoundary & SelectorChecker::BoundaryBehaviorMask) == SelectorChecker::CrossesBoundary)
        return context.element->parentOrShadowHostElement();

    // If context.scope is not a shadow host, we cannot walk up from a shadow root to its shadow host.
    if (!(context.behaviorAtBoundary & SelectorChecker::ScopeIsShadowHost))
        return context.element->parentElement();

    // If behaviorAtBoundary is StaysWithInTreeScope, we cannot walk up from a shadow root to its shadow host.
    return (context.behaviorAtBoundary & SelectorChecker::BoundaryBehaviorMask) != SelectorChecker::StaysWithinTreeScope ? context.element->parentOrShadowHostElement() : context.element->parentElement();
}

bool SelectorChecker::scopeContainsLastMatchedElement(const SelectorCheckingContext& context) const
{
    if (!(context.behaviorAtBoundary & SelectorChecker::ScopeContainsLastMatchedElement))
        return true;

    ASSERT(context.scope);
    // If behaviorAtBoundary is not ScopeIsShadowHost, we can use "contains".
    if (!(context.behaviorAtBoundary & SelectorChecker::ScopeIsShadowHost))
        return context.scope->contains(context.element);

    // If a given element is scope, i.e. shadow host, matches.
    if (context.element == context.scope)
        return true;

    ShadowRoot* root = context.element->containingShadowRoot();
    if (!root)
        return false;

    // If a host of the containing shadow root is scope, matches.
    return root->host() == context.scope;
}

// Recursive check of selectors and combinators
// It can return 4 different values:
// * SelectorMatches          - the selector matches the element e
// * SelectorFailsLocally     - the selector fails for the element e
// * SelectorFailsAllSiblings - the selector fails for e and any sibling of e
// * SelectorFailsCompletely  - the selector fails for e and any sibling or ancestor of e
template<typename SiblingTraversalStrategy>
SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext& context, PseudoId& dynamicPseudo, const SiblingTraversalStrategy& siblingTraversalStrategy) const
{
    // first selector has to match
    if (!checkOne(context, siblingTraversalStrategy))
        return SelectorFailsLocally;

    if (context.selector->m_match == CSSSelector::PseudoElement) {
        if (context.selector->isCustomPseudoElement()) {
            if (!matchesCustomPseudoElement(context.element, context.selector))
                return SelectorFailsLocally;
        } else if (context.selector->isContentPseudoElement()) {
            if (!context.element->isInShadowTree() || !context.element->isInsertionPoint())
                return SelectorFailsLocally;
        } else {
            if ((!context.elementStyle && m_mode == ResolvingStyle) || m_mode == QueryingRules)
                return SelectorFailsLocally;

            PseudoId pseudoId = CSSSelector::pseudoId(context.selector->pseudoType());
            if (pseudoId == FIRST_LETTER)
                context.element->document().styleEngine()->setUsesFirstLetterRules(true);
            if (pseudoId != NOPSEUDO && m_mode != SharingRules)
                dynamicPseudo = pseudoId;
        }
    }

    // The rest of the selectors has to match
    CSSSelector::Relation relation = context.selector->relation();

    // Prepare next selector
    const CSSSelector* historySelector = context.selector->tagHistory();
    if (!historySelector)
        return scopeContainsLastMatchedElement(context) ? SelectorMatches : SelectorFailsLocally;

    SelectorCheckingContext nextContext(context);
    nextContext.selector = historySelector;

    PseudoId ignoreDynamicPseudo = NOPSEUDO;
    if (relation != CSSSelector::SubSelector) {
        // Abort if the next selector would exceed the scope.
        if (context.element == context.scope && (context.behaviorAtBoundary & BoundaryBehaviorMask) != StaysWithinTreeScope)
            return SelectorFailsCompletely;

        // Bail-out if this selector is irrelevant for the pseudoId
        if (context.pseudoId != NOPSEUDO && context.pseudoId != dynamicPseudo)
            return SelectorFailsCompletely;

        // Disable :visited matching when we see the first link or try to match anything else than an ancestors.
        if (!context.isSubSelector && (context.element->isLink() || (relation != CSSSelector::Descendant && relation != CSSSelector::Child)))
            nextContext.visitedMatchType = VisitedMatchDisabled;

        nextContext.pseudoId = NOPSEUDO;
    }

    switch (relation) {
    case CSSSelector::Descendant:
        if (context.selector->relationIsAffectedByPseudoContent()) {
            for (Element* element = context.element; element; element = element->parentElement()) {
                if (matchForShadowDistributed(element, siblingTraversalStrategy, ignoreDynamicPseudo, nextContext) == SelectorMatches)
                    return SelectorMatches;
            }
            return SelectorFailsCompletely;
        }
        nextContext.isSubSelector = false;
        nextContext.elementStyle = 0;
        for (nextContext.element = parentElement(context); nextContext.element; nextContext.element = parentElement(nextContext)) {
            Match match = this->match(nextContext, ignoreDynamicPseudo, siblingTraversalStrategy);
            if (match == SelectorMatches || match == SelectorFailsCompletely)
                return match;
            if (nextContext.element == nextContext.scope && (nextContext.behaviorAtBoundary & BoundaryBehaviorMask) != StaysWithinTreeScope)
                return SelectorFailsCompletely;
        }
        return SelectorFailsCompletely;
    case CSSSelector::Child:
        {
            if (context.selector->relationIsAffectedByPseudoContent())
                return matchForShadowDistributed(context.element, siblingTraversalStrategy, ignoreDynamicPseudo, nextContext);

            nextContext.element = parentElement(context);
            if (!nextContext.element)
                return SelectorFailsCompletely;

            nextContext.isSubSelector = false;
            nextContext.elementStyle = 0;
            return match(nextContext, ignoreDynamicPseudo, siblingTraversalStrategy);
        }
    case CSSSelector::DirectAdjacent:
        if (m_mode == ResolvingStyle) {
            if (Element* parent = parentElement(context))
                parent->setChildrenAffectedByDirectAdjacentRules();
        }
        nextContext.element = context.element->previousElementSibling();
        if (!nextContext.element)
            return SelectorFailsAllSiblings;
        nextContext.isSubSelector = false;
        nextContext.elementStyle = 0;
        return match(nextContext, ignoreDynamicPseudo, siblingTraversalStrategy);

    case CSSSelector::IndirectAdjacent:
        if (m_mode == ResolvingStyle) {
            if (Element* parent = parentElement(context))
                parent->setChildrenAffectedByForwardPositionalRules();
        }
        nextContext.element = context.element->previousElementSibling();
        nextContext.isSubSelector = false;
        nextContext.elementStyle = 0;
        for (; nextContext.element; nextContext.element = nextContext.element->previousElementSibling()) {
            Match match = this->match(nextContext, ignoreDynamicPseudo, siblingTraversalStrategy);
            if (match == SelectorMatches || match == SelectorFailsAllSiblings || match == SelectorFailsCompletely)
                return match;
        };
        return SelectorFailsAllSiblings;

    case CSSSelector::SubSelector:
        // a selector is invalid if something follows a pseudo-element
        // We make an exception for scrollbar pseudo elements and allow a set of pseudo classes (but nothing else)
        // to follow the pseudo elements.
        nextContext.hasScrollbarPseudo = dynamicPseudo != NOPSEUDO && (context.scrollbar || dynamicPseudo == SCROLLBAR_CORNER || dynamicPseudo == RESIZER);
        nextContext.hasSelectionPseudo = dynamicPseudo == SELECTION;
        if ((context.elementStyle || m_mode == CollectingRules || m_mode == QueryingRules) && dynamicPseudo != NOPSEUDO
            && !nextContext.hasSelectionPseudo
            && !(nextContext.hasScrollbarPseudo && nextContext.selector->m_match == CSSSelector::PseudoClass))
            return SelectorFailsCompletely;
        nextContext.isSubSelector = true;
        return match(nextContext, dynamicPseudo, siblingTraversalStrategy);

    case CSSSelector::ShadowPseudo:
        {
            // If we're in the same tree-scope as the scoping element, then following a shadow descendant combinator would escape that and thus the scope.
            if (context.scope && &context.scope->treeScope() == &context.element->treeScope() && (context.behaviorAtBoundary & BoundaryBehaviorMask) != StaysWithinTreeScope)
                return SelectorFailsCompletely;
            Element* shadowHostNode = context.element->shadowHost();
            if (!shadowHostNode)
                return SelectorFailsCompletely;
            nextContext.element = shadowHostNode;
            nextContext.isSubSelector = false;
            nextContext.elementStyle = 0;
            return match(nextContext, ignoreDynamicPseudo, siblingTraversalStrategy);
        }
    }

    ASSERT_NOT_REACHED();
    return SelectorFailsCompletely;
}

template<typename SiblingTraversalStrategy>
SelectorChecker::Match SelectorChecker::matchForShadowDistributed(const Element* element, const SiblingTraversalStrategy& siblingTraversalStrategy, PseudoId& dynamicPseudo, SelectorCheckingContext& nextContext) const
{
    Vector<InsertionPoint*, 8> insertionPoints;
    collectInsertionPointsWhereNodeIsDistributed(element, insertionPoints);
    for (size_t i = 0; i < insertionPoints.size(); ++i) {
        nextContext.element = insertionPoints[i];
        nextContext.isSubSelector = false;
        nextContext.elementStyle = 0;
        if (match(nextContext, dynamicPseudo, siblingTraversalStrategy) == SelectorMatches)
            return SelectorMatches;
    }
    return SelectorFailsCompletely;
}

static inline bool containsHTMLSpace(const AtomicString& string)
{
    for (unsigned i = 0; i < string.length(); i++)
        if (isHTMLSpace<UChar>(string[i]))
            return true;
    return false;
}

static bool attributeValueMatches(const Attribute* attributeItem, CSSSelector::Match match, const AtomicString& selectorValue, bool caseSensitive)
{
    const AtomicString& value = attributeItem->value();
    if (value.isNull())
        return false;

    switch (match) {
    case CSSSelector::Exact:
        if (caseSensitive ? selectorValue != value : !equalIgnoringCase(selectorValue, value))
            return false;
        break;
    case CSSSelector::List:
        {
            // Ignore empty selectors or selectors containing HTML spaces
            if (selectorValue.isEmpty() || containsHTMLSpace(selectorValue))
                return false;

            unsigned startSearchAt = 0;
            while (true) {
                size_t foundPos = value.find(selectorValue, startSearchAt, caseSensitive);
                if (foundPos == kNotFound)
                    return false;
                if (!foundPos || isHTMLSpace<UChar>(value[foundPos - 1])) {
                    unsigned endStr = foundPos + selectorValue.length();
                    if (endStr == value.length() || isHTMLSpace<UChar>(value[endStr]))
                        break; // We found a match.
                }

                // No match. Keep looking.
                startSearchAt = foundPos + 1;
            }
            break;
        }
    case CSSSelector::Contain:
        if (!value.contains(selectorValue, caseSensitive) || selectorValue.isEmpty())
            return false;
        break;
    case CSSSelector::Begin:
        if (!value.startsWith(selectorValue, caseSensitive) || selectorValue.isEmpty())
            return false;
        break;
    case CSSSelector::End:
        if (!value.endsWith(selectorValue, caseSensitive) || selectorValue.isEmpty())
            return false;
        break;
    case CSSSelector::Hyphen:
        if (value.length() < selectorValue.length())
            return false;
        if (!value.startsWith(selectorValue, caseSensitive))
            return false;
        // It they start the same, check for exact match or following '-':
        if (value.length() != selectorValue.length() && value[selectorValue.length()] != '-')
            return false;
        break;
    case CSSSelector::PseudoClass:
    case CSSSelector::PseudoElement:
    default:
        break;
    }

    return true;
}

static bool anyAttributeMatches(Element* element, CSSSelector::Match match, const QualifiedName& selectorAttr, const AtomicString& selectorValue, bool caseSensitive)
{
    ASSERT(element->hasAttributesWithoutUpdate());
    for (size_t i = 0; i < element->attributeCount(); ++i) {
        const Attribute* attributeItem = element->attributeItem(i);

        if (!attributeItem->matches(selectorAttr))
            continue;

        if (attributeValueMatches(attributeItem, match, selectorValue, caseSensitive))
            return true;
    }

    return false;
}

template<typename SiblingTraversalStrategy>
bool SelectorChecker::checkOne(const SelectorCheckingContext& context, const SiblingTraversalStrategy& siblingTraversalStrategy) const
{
    Element* const & element = context.element;
    const CSSSelector* const & selector = context.selector;
    ASSERT(element);
    ASSERT(selector);

    if (selector->m_match == CSSSelector::Tag)
        return SelectorChecker::tagMatches(element, selector->tagQName());

    if (selector->m_match == CSSSelector::Class)
        return element->hasClass() && element->classNames().contains(selector->value());

    if (selector->m_match == CSSSelector::Id)
        return element->hasID() && element->idForStyleResolution() == selector->value();

    if (selector->isAttributeSelector()) {
        const QualifiedName& attr = selector->attribute();

        if (!element->hasAttributes())
            return false;

        bool caseSensitive = !m_documentIsHTML || HTMLDocument::isCaseSensitiveAttribute(attr);

        if (!anyAttributeMatches(element, static_cast<CSSSelector::Match>(selector->m_match), attr, selector->value(), caseSensitive))
            return false;
    }

    if (selector->m_match == CSSSelector::PseudoClass) {
        // Handle :not up front.
        if (selector->pseudoType() == CSSSelector::PseudoNot) {
            SelectorCheckingContext subContext(context);
            subContext.isSubSelector = true;
            ASSERT(selector->selectorList());
            for (subContext.selector = selector->selectorList()->first(); subContext.selector; subContext.selector = subContext.selector->tagHistory()) {
                // :not cannot nest. I don't really know why this is a
                // restriction in CSS3, but it is, so let's honor it.
                // the parser enforces that this never occurs
                ASSERT(subContext.selector->pseudoType() != CSSSelector::PseudoNot);
                // We select between :visited and :link when applying. We don't know which one applied (or not) yet.
                if (subContext.selector->pseudoType() == CSSSelector::PseudoVisited || (subContext.selector->pseudoType() == CSSSelector::PseudoLink && subContext.visitedMatchType == VisitedMatchEnabled))
                    return true;
                if (!checkOne(subContext, DOMSiblingTraversalStrategy()))
                    return true;
            }
        } else if (context.hasScrollbarPseudo) {
            // CSS scrollbars match a specific subset of pseudo classes, and they have specialized rules for each
            // (since there are no elements involved).
            return checkScrollbarPseudoClass(context, &element->document(), selector);
        } else if (context.hasSelectionPseudo) {
            if (selector->pseudoType() == CSSSelector::PseudoWindowInactive)
                return !element->document().page()->focusController().isActive();
        }

        // Normal element pseudo class checking.
        switch (selector->pseudoType()) {
            // Pseudo classes:
        case CSSSelector::PseudoNot:
            break; // Already handled up above.
        case CSSSelector::PseudoEmpty:
            {
                bool result = true;
                for (Node* n = element->firstChild(); n; n = n->nextSibling()) {
                    if (n->isElementNode()) {
                        result = false;
                        break;
                    }
                    if (n->isTextNode()) {
                        Text* textNode = toText(n);
                        if (!textNode->data().isEmpty()) {
                            result = false;
                            break;
                        }
                    }
                }
                if (m_mode == ResolvingStyle) {
                    element->setStyleAffectedByEmpty();
                    if (context.elementStyle)
                        context.elementStyle->setEmptyState(result);
                    else if (element->renderStyle() && (element->document().styleEngine()->usesSiblingRules() || element->renderStyle()->unique()))
                        element->renderStyle()->setEmptyState(result);
                }
                return result;
            }
        case CSSSelector::PseudoFirstChild:
            // first-child matches the first child that is an element
            if (Element* parent = element->parentElement()) {
                bool result = siblingTraversalStrategy.isFirstChild(element);
                if (m_mode == ResolvingStyle) {
                    RenderStyle* childStyle = context.elementStyle ? context.elementStyle : element->renderStyle();
                    parent->setChildrenAffectedByFirstChildRules();
                    if (result && childStyle)
                        childStyle->setFirstChildState();
                }
                return result;
            }
            break;
        case CSSSelector::PseudoFirstOfType:
            // first-of-type matches the first element of its type
            if (Element* parent = element->parentElement()) {
                bool result = siblingTraversalStrategy.isFirstOfType(element, element->tagQName());
                if (m_mode == ResolvingStyle)
                    parent->setChildrenAffectedByForwardPositionalRules();
                return result;
            }
            break;
        case CSSSelector::PseudoLastChild:
            // last-child matches the last child that is an element
            if (Element* parent = element->parentElement()) {
                bool result = parent->isFinishedParsingChildren() && siblingTraversalStrategy.isLastChild(element);
                if (m_mode == ResolvingStyle) {
                    RenderStyle* childStyle = context.elementStyle ? context.elementStyle : element->renderStyle();
                    parent->setChildrenAffectedByLastChildRules();
                    if (result && childStyle)
                        childStyle->setLastChildState();
                }
                return result;
            }
            break;
        case CSSSelector::PseudoLastOfType:
            // last-of-type matches the last element of its type
            if (Element* parent = element->parentElement()) {
                if (m_mode == ResolvingStyle)
                    parent->setChildrenAffectedByBackwardPositionalRules();
                if (!parent->isFinishedParsingChildren())
                    return false;
                return siblingTraversalStrategy.isLastOfType(element, element->tagQName());
            }
            break;
        case CSSSelector::PseudoOnlyChild:
            if (Element* parent = element->parentElement()) {
                bool firstChild = siblingTraversalStrategy.isFirstChild(element);
                bool onlyChild = firstChild && parent->isFinishedParsingChildren() && siblingTraversalStrategy.isLastChild(element);
                if (m_mode == ResolvingStyle) {
                    RenderStyle* childStyle = context.elementStyle ? context.elementStyle : element->renderStyle();
                    parent->setChildrenAffectedByFirstChildRules();
                    parent->setChildrenAffectedByLastChildRules();
                    if (firstChild && childStyle)
                        childStyle->setFirstChildState();
                    if (onlyChild && childStyle)
                        childStyle->setLastChildState();
                }
                return onlyChild;
            }
            break;
        case CSSSelector::PseudoOnlyOfType:
            // FIXME: This selector is very slow.
            if (Element* parent = element->parentElement()) {
                if (m_mode == ResolvingStyle) {
                    parent->setChildrenAffectedByForwardPositionalRules();
                    parent->setChildrenAffectedByBackwardPositionalRules();
                }
                if (!parent->isFinishedParsingChildren())
                    return false;
                return siblingTraversalStrategy.isFirstOfType(element, element->tagQName()) && siblingTraversalStrategy.isLastOfType(element, element->tagQName());
            }
            break;
        case CSSSelector::PseudoNthChild:
            if (!selector->parseNth())
                break;
            if (Element* parent = element->parentElement()) {
                int count = 1 + siblingTraversalStrategy.countElementsBefore(element);
                if (m_mode == ResolvingStyle) {
                    RenderStyle* childStyle = context.elementStyle ? context.elementStyle : element->renderStyle();
                    element->setChildIndex(count);
                    if (childStyle)
                        childStyle->setUnique();
                    parent->setChildrenAffectedByForwardPositionalRules();
                }

                if (selector->matchNth(count))
                    return true;
            }
            break;
        case CSSSelector::PseudoNthOfType:
            if (!selector->parseNth())
                break;
            if (Element* parent = element->parentElement()) {
                int count = 1 + siblingTraversalStrategy.countElementsOfTypeBefore(element, element->tagQName());
                if (m_mode == ResolvingStyle)
                    parent->setChildrenAffectedByForwardPositionalRules();

                if (selector->matchNth(count))
                    return true;
            }
            break;
        case CSSSelector::PseudoNthLastChild:
            if (!selector->parseNth())
                break;
            if (Element* parent = element->parentElement()) {
                if (m_mode == ResolvingStyle)
                    parent->setChildrenAffectedByBackwardPositionalRules();
                if (!parent->isFinishedParsingChildren())
                    return false;
                int count = 1 + siblingTraversalStrategy.countElementsAfter(element);
                if (selector->matchNth(count))
                    return true;
            }
            break;
        case CSSSelector::PseudoNthLastOfType:
            if (!selector->parseNth())
                break;
            if (Element* parent = element->parentElement()) {
                if (m_mode == ResolvingStyle)
                    parent->setChildrenAffectedByBackwardPositionalRules();
                if (!parent->isFinishedParsingChildren())
                    return false;

                int count = 1 + siblingTraversalStrategy.countElementsOfTypeAfter(element, element->tagQName());
                if (selector->matchNth(count))
                    return true;
            }
            break;
        case CSSSelector::PseudoTarget:
            if (element == element->document().cssTarget())
                return true;
            break;
        case CSSSelector::PseudoAny:
            {
                SelectorCheckingContext subContext(context);
                subContext.isSubSelector = true;
                PseudoId ignoreDynamicPseudo = NOPSEUDO;
                ASSERT(selector->selectorList());
                for (subContext.selector = selector->selectorList()->first(); subContext.selector; subContext.selector = CSSSelectorList::next(subContext.selector)) {
                    if (match(subContext, ignoreDynamicPseudo, siblingTraversalStrategy) == SelectorMatches)
                        return true;
                }
            }
            break;
        case CSSSelector::PseudoAutofill:
            if (!element || !element->isFormControlElement())
                break;
            if (element->hasTagName(inputTag))
                return toHTMLInputElement(element)->isAutofilled();
            break;
        case CSSSelector::PseudoAnyLink:
        case CSSSelector::PseudoLink:
            // :visited and :link matches are separated later when applying the style. Here both classes match all links...
            return element->isLink();
        case CSSSelector::PseudoVisited:
            // ...except if :visited matching is disabled for ancestor/sibling matching.
            return element->isLink() && context.visitedMatchType == VisitedMatchEnabled;
        case CSSSelector::PseudoDrag:
            if (m_mode == ResolvingStyle) {
                if (context.elementStyle)
                    context.elementStyle->setAffectedByDrag();
                else
                    element->setChildrenAffectedByDrag(true);
            }
            if (element->renderer() && element->renderer()->isDragging())
                return true;
            break;
        case CSSSelector::PseudoFocus:
            return matchesFocusPseudoClass(element);
        case CSSSelector::PseudoHover:
            // If we're in quirks mode, then hover should never match anchors with no
            // href and *:hover should not match anything. This is important for sites like wsj.com.
            if (m_strictParsing || context.isSubSelector || (selector->m_match == CSSSelector::Tag && selector->tagQName() != anyQName() && !isHTMLAnchorElement(element)) || element->isLink()) {
                if (m_mode == ResolvingStyle) {
                    if (context.elementStyle)
                        context.elementStyle->setAffectedByHover();
                    else
                        element->setChildrenAffectedByHover(true);
                }
                if (element->hovered() || InspectorInstrumentation::forcePseudoState(element, CSSSelector::PseudoHover))
                    return true;
            }
            break;
        case CSSSelector::PseudoActive:
            // If we're in quirks mode, then :active should never match anchors with no
            // href and *:active should not match anything.
            if (m_strictParsing || context.isSubSelector || (selector->m_match == CSSSelector::Tag && selector->tagQName() != anyQName() && !isHTMLAnchorElement(element)) || element->isLink()) {
                if (m_mode == ResolvingStyle) {
                    if (context.elementStyle)
                        context.elementStyle->setAffectedByActive();
                    else
                        element->setChildrenAffectedByActive(true);
                }
                if (element->active() || InspectorInstrumentation::forcePseudoState(element, CSSSelector::PseudoActive))
                    return true;
            }
            break;
        case CSSSelector::PseudoEnabled:
            if (element && (element->isFormControlElement() || element->hasTagName(optionTag) || isHTMLOptGroupElement(element)))
                return !element->isDisabledFormControl();
            break;
        case CSSSelector::PseudoFullPageMedia:
            return element && element->document().isMediaDocument();
            break;
        case CSSSelector::PseudoDefault:
            return element && element->isDefaultButtonForForm();
        case CSSSelector::PseudoDisabled:
            if (element && (element->isFormControlElement() || element->hasTagName(optionTag) || isHTMLOptGroupElement(element)))
                return element->isDisabledFormControl();
            break;
        case CSSSelector::PseudoReadOnly:
            return element && element->matchesReadOnlyPseudoClass();
        case CSSSelector::PseudoReadWrite:
            return element && element->matchesReadWritePseudoClass();
        case CSSSelector::PseudoOptional:
            return element && element->isOptionalFormControl();
        case CSSSelector::PseudoRequired:
            return element && element->isRequiredFormControl();
        case CSSSelector::PseudoValid:
            if (!element)
                return false;
            element->document().setContainsValidityStyleRules();
            return element->willValidate() && element->isValidFormControlElement();
        case CSSSelector::PseudoInvalid:
            if (!element)
                return false;
            element->document().setContainsValidityStyleRules();
            return element->willValidate() && !element->isValidFormControlElement();
        case CSSSelector::PseudoChecked:
            {
                if (!element)
                    break;
                if (element->hasTagName(inputTag)) {
                    HTMLInputElement* inputElement = toHTMLInputElement(element);
                    // Even though WinIE allows checked and indeterminate to
                    // co-exist, the CSS selector spec says that you can't be
                    // both checked and indeterminate. We will behave like WinIE
                    // behind the scenes and just obey the CSS spec here in the
                    // test for matching the pseudo.
                    if (inputElement->shouldAppearChecked() && !inputElement->shouldAppearIndeterminate())
                        return true;
                } else if (element->hasTagName(optionTag) && toHTMLOptionElement(element)->selected())
                    return true;
                break;
            }
        case CSSSelector::PseudoIndeterminate:
            return element && element->shouldAppearIndeterminate();
        case CSSSelector::PseudoRoot:
            if (element == element->document().documentElement())
                return true;
            break;
        case CSSSelector::PseudoLang:
            {
                AtomicString value;
                if (element->isWebVTTElement())
                    value = toWebVTTElement(element)->language();
                else
                    value = element->computeInheritedLanguage();
                const AtomicString& argument = selector->argument();
                if (value.isEmpty() || !value.startsWith(argument, false))
                    break;
                if (value.length() != argument.length() && value[argument.length()] != '-')
                    break;
                return true;
            }
        case CSSSelector::PseudoFullScreen:
            // While a Document is in the fullscreen state, and the document's current fullscreen
            // element is an element in the document, the 'full-screen' pseudoclass applies to
            // that element. Also, an <iframe>, <object> or <embed> element whose child browsing
            // context's Document is in the fullscreen state has the 'full-screen' pseudoclass applied.
            if (element->isFrameElementBase() && element->containsFullScreenElement())
                return true;
            if (FullscreenElementStack* fullscreen = FullscreenElementStack::fromIfExists(&element->document())) {
                if (!fullscreen->webkitIsFullScreen())
                    return false;
                return element == fullscreen->webkitCurrentFullScreenElement();
            }
            return false;
        case CSSSelector::PseudoFullScreenAncestor:
            return element->containsFullScreenElement();
        case CSSSelector::PseudoFullScreenDocument:
            // While a Document is in the fullscreen state, the 'full-screen-document' pseudoclass applies
            // to all elements of that Document.
            if (!FullscreenElementStack::isFullScreen(&element->document()))
                return false;
            return true;
        case CSSSelector::PseudoSeamlessDocument:
            // While a document is rendered in a seamless iframe, the 'seamless-document' pseudoclass applies
            // to all elements of that Document.
            return element->document().shouldDisplaySeamlesslyWithParent();
        case CSSSelector::PseudoInRange:
            if (!element)
                return false;
            element->document().setContainsValidityStyleRules();
            return element->isInRange();
        case CSSSelector::PseudoOutOfRange:
            if (!element)
                return false;
            element->document().setContainsValidityStyleRules();
            return element->isOutOfRange();
        case CSSSelector::PseudoFutureCue:
            return (element->isWebVTTElement() && !toWebVTTElement(element)->isPastNode());
        case CSSSelector::PseudoPastCue:
            return (element->isWebVTTElement() && toWebVTTElement(element)->isPastNode());

        case CSSSelector::PseudoScope:
            {
                const Node* contextualReferenceNode = !context.scope || (context.behaviorAtBoundary & BoundaryBehaviorMask) == CrossesBoundary ? element->document().documentElement() : context.scope;
                if (element == contextualReferenceNode)
                    return true;
                break;
            }

        case CSSSelector::PseudoUnresolved:
            if (element->isUnresolvedCustomElement())
                return true;
            break;

        case CSSSelector::PseudoHost:
            {
                // :host only matches a shadow host when :host is in a shadow tree of the shadow host.
                if (!context.scope || !(context.behaviorAtBoundary & ScopeIsShadowHost) || context.scope != element)
                    return false;
                ASSERT(element->shadow());

                // For empty parameter case, i.e. just :host or :host().
                if (!selector->selectorList())
                    return true;

                SelectorCheckingContext subContext(context);
                subContext.isSubSelector = true;
                subContext.behaviorAtBoundary = CrossesBoundary;
                subContext.scope = 0;
                // Use NodeRenderingTraversal to traverse a composed ancestor list of a given element.
                for (Element* nextElement = NodeRenderingTraversal::parentElement(element); nextElement; nextElement = NodeRenderingTraversal::parentElement(nextElement)) {
                    // If one of simple selectors matches an element, returns SelectorMatches. Just "OR".
                    for (subContext.selector = selector->selectorList()->first(); subContext.selector; subContext.selector = CSSSelectorList::next(subContext.selector)) {
                        PseudoId ignoreDynamicPseudo = NOPSEUDO;
                        subContext.element = nextElement;
                        if (match(subContext, ignoreDynamicPseudo, siblingTraversalStrategy) == SelectorMatches)
                            return true;
                    }
                }
            }
            break;

        case CSSSelector::PseudoHorizontal:
        case CSSSelector::PseudoVertical:
        case CSSSelector::PseudoDecrement:
        case CSSSelector::PseudoIncrement:
        case CSSSelector::PseudoStart:
        case CSSSelector::PseudoEnd:
        case CSSSelector::PseudoDoubleButton:
        case CSSSelector::PseudoSingleButton:
        case CSSSelector::PseudoNoButton:
        case CSSSelector::PseudoCornerPresent:
            return false;

        case CSSSelector::PseudoUnknown:
        case CSSSelector::PseudoNotParsed:
        default:
            ASSERT_NOT_REACHED();
            break;
        }
        return false;
    }
    else if (selector->m_match == CSSSelector::PseudoElement && selector->pseudoType() == CSSSelector::PseudoCue) {
        SelectorCheckingContext subContext(context);
        subContext.isSubSelector = true;
        subContext.behaviorAtBoundary = StaysWithinTreeScope;

        PseudoId ignoreDynamicPseudo = NOPSEUDO;
        const CSSSelector* const & selector = context.selector;
        for (subContext.selector = selector->selectorList()->first(); subContext.selector; subContext.selector = CSSSelectorList::next(subContext.selector)) {
            if (match(subContext, ignoreDynamicPseudo, siblingTraversalStrategy) == SelectorMatches)
                return true;
        }
        return false;
    }
    // ### add the rest of the checks...
    return true;
}

bool SelectorChecker::checkScrollbarPseudoClass(const SelectorCheckingContext& context, Document* document, const CSSSelector* selector) const
{
    RenderScrollbar* scrollbar = context.scrollbar;
    ScrollbarPart part = context.scrollbarPart;

    // FIXME: This is a temporary hack for resizers and scrollbar corners. Eventually :window-inactive should become a real
    // pseudo class and just apply to everything.
    if (selector->pseudoType() == CSSSelector::PseudoWindowInactive)
        return !document->page()->focusController().isActive();

    if (!scrollbar)
        return false;

    ASSERT(selector->m_match == CSSSelector::PseudoClass);
    switch (selector->pseudoType()) {
    case CSSSelector::PseudoEnabled:
        return scrollbar->enabled();
    case CSSSelector::PseudoDisabled:
        return !scrollbar->enabled();
    case CSSSelector::PseudoHover:
        {
            ScrollbarPart hoveredPart = scrollbar->hoveredPart();
            if (part == ScrollbarBGPart)
                return hoveredPart != NoPart;
            if (part == TrackBGPart)
                return hoveredPart == BackTrackPart || hoveredPart == ForwardTrackPart || hoveredPart == ThumbPart;
            return part == hoveredPart;
        }
    case CSSSelector::PseudoActive:
        {
            ScrollbarPart pressedPart = scrollbar->pressedPart();
            if (part == ScrollbarBGPart)
                return pressedPart != NoPart;
            if (part == TrackBGPart)
                return pressedPart == BackTrackPart || pressedPart == ForwardTrackPart || pressedPart == ThumbPart;
            return part == pressedPart;
        }
    case CSSSelector::PseudoHorizontal:
        return scrollbar->orientation() == HorizontalScrollbar;
    case CSSSelector::PseudoVertical:
        return scrollbar->orientation() == VerticalScrollbar;
    case CSSSelector::PseudoDecrement:
        return part == BackButtonStartPart || part == BackButtonEndPart || part == BackTrackPart;
    case CSSSelector::PseudoIncrement:
        return part == ForwardButtonStartPart || part == ForwardButtonEndPart || part == ForwardTrackPart;
    case CSSSelector::PseudoStart:
        return part == BackButtonStartPart || part == ForwardButtonStartPart || part == BackTrackPart;
    case CSSSelector::PseudoEnd:
        return part == BackButtonEndPart || part == ForwardButtonEndPart || part == ForwardTrackPart;
    case CSSSelector::PseudoDoubleButton:
        {
            ScrollbarButtonsPlacement buttonsPlacement = scrollbar->theme()->buttonsPlacement();
            if (part == BackButtonStartPart || part == ForwardButtonStartPart || part == BackTrackPart)
                return buttonsPlacement == ScrollbarButtonsDoubleStart || buttonsPlacement == ScrollbarButtonsDoubleBoth;
            if (part == BackButtonEndPart || part == ForwardButtonEndPart || part == ForwardTrackPart)
                return buttonsPlacement == ScrollbarButtonsDoubleEnd || buttonsPlacement == ScrollbarButtonsDoubleBoth;
            return false;
        }
    case CSSSelector::PseudoSingleButton:
        {
            ScrollbarButtonsPlacement buttonsPlacement = scrollbar->theme()->buttonsPlacement();
            if (part == BackButtonStartPart || part == ForwardButtonEndPart || part == BackTrackPart || part == ForwardTrackPart)
                return buttonsPlacement == ScrollbarButtonsSingle;
            return false;
        }
    case CSSSelector::PseudoNoButton:
        {
            ScrollbarButtonsPlacement buttonsPlacement = scrollbar->theme()->buttonsPlacement();
            if (part == BackTrackPart)
                return buttonsPlacement == ScrollbarButtonsNone || buttonsPlacement == ScrollbarButtonsDoubleEnd;
            if (part == ForwardTrackPart)
                return buttonsPlacement == ScrollbarButtonsNone || buttonsPlacement == ScrollbarButtonsDoubleStart;
            return false;
        }
    case CSSSelector::PseudoCornerPresent:
        return scrollbar->scrollableArea()->isScrollCornerVisible();
    default:
        return false;
    }
}

unsigned SelectorChecker::determineLinkMatchType(const CSSSelector* selector)
{
    unsigned linkMatchType = MatchAll;

    // Statically determine if this selector will match a link in visited, unvisited or any state, or never.
    // :visited never matches other elements than the innermost link element.
    for (; selector; selector = selector->tagHistory()) {
        switch (selector->pseudoType()) {
        case CSSSelector::PseudoNot:
            {
                // :not(:visited) is equivalent to :link. Parser enforces that :not can't nest.
                ASSERT(selector->selectorList());
                for (const CSSSelector* subSelector = selector->selectorList()->first(); subSelector; subSelector = subSelector->tagHistory()) {
                    CSSSelector::PseudoType subType = subSelector->pseudoType();
                    if (subType == CSSSelector::PseudoVisited)
                        linkMatchType &= ~SelectorChecker::MatchVisited;
                    else if (subType == CSSSelector::PseudoLink)
                        linkMatchType &= ~SelectorChecker::MatchLink;
                }
            }
            break;
        case CSSSelector::PseudoLink:
            linkMatchType &= ~SelectorChecker::MatchVisited;
            break;
        case CSSSelector::PseudoVisited:
            linkMatchType &= ~SelectorChecker::MatchLink;
            break;
        default:
            // We don't support :link and :visited inside :-webkit-any.
            break;
        }
        CSSSelector::Relation relation = selector->relation();
        if (relation == CSSSelector::SubSelector)
            continue;
        if (relation != CSSSelector::Descendant && relation != CSSSelector::Child)
            return linkMatchType;
        if (linkMatchType != MatchAll)
            return linkMatchType;
    }
    return linkMatchType;
}

bool SelectorChecker::isFrameFocused(const Element* element)
{
    return element->document().frame() && element->document().frame()->selection().isFocusedAndActive();
}

bool SelectorChecker::matchesFocusPseudoClass(const Element* element)
{
    if (InspectorInstrumentation::forcePseudoState(const_cast<Element*>(element), CSSSelector::PseudoFocus))
        return true;
    return element->focused() && isFrameFocused(element);
}

template
SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, PseudoId&, const DOMSiblingTraversalStrategy&) const;

template
SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, PseudoId&, const ShadowDOMSiblingTraversalStrategy&) const;

}