/*

 * Copyright (C) 2005 Frerich Raabe <raabe@kde.org>

 * Copyright (C) 2006, 2009 Apple Inc. All rights reserved.

 * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#include "config.h"

#include "XPathStep.h"

#if ENABLE(XPATH)

#include "Attr.h"

#include "Document.h"

#include "Element.h"

#include "NamedNodeMap.h"

#include "XMLNSNames.h"

#include "XPathParser.h"

#include "XPathUtil.h"

namespace WebCore {

namespace XPath {

Step::Step(Axis axis, const NodeTest& nodeTest, const Vector<Predicate*>& predicates)

    : m_axis(axis)

    , m_nodeTest(nodeTest)

    , m_predicates(predicates)

{

}

Step::~Step()

{

    deleteAllValues(m_predicates);

    deleteAllValues(m_nodeTest.mergedPredicates());

}

void Step::optimize()

{

    // Evaluate predicates as part of node test if possible to avoid building unnecessary NodeSets.

    // E.g., there is no need to build a set of all "foo" nodes to evaluate "foo[@bar]", we can check the predicate while enumerating.

    // This optimization can be applied to predicates that are not context node list sensitive, or to first predicate that is only context position sensitive, e.g. foo[position() mod 2 = 0].

    Vector<Predicate*> remainingPredicates;

    for (size_t i = 0; i < m_predicates.size(); ++i) {

        Predicate* predicate = m_predicates[i];

        if ((!predicate->isContextPositionSensitive() || m_nodeTest.mergedPredicates().isEmpty()) && !predicate->isContextSizeSensitive() && remainingPredicates.isEmpty()) {

            m_nodeTest.mergedPredicates().append(predicate);

        } else

            remainingPredicates.append(predicate);

    }

    swap(remainingPredicates, m_predicates);

}

void optimizeStepPair(Step* first, Step* second, bool& dropSecondStep)

{

    dropSecondStep = false;

    if (first->m_axis == Step::DescendantOrSelfAxis

        && first->m_nodeTest.kind() == Step::NodeTest::AnyNodeTest

        && !first->m_predicates.size()

        && !first->m_nodeTest.mergedPredicates().size()) {

        ASSERT(first->m_nodeTest.data().isEmpty());

        ASSERT(first->m_nodeTest.namespaceURI().isEmpty());

        // Optimize the common case of "//" AKA /descendant-or-self::node()/child::NodeTest to /descendant::NodeTest.

        if (second->m_axis == Step::ChildAxis && second->predicatesAreContextListInsensitive()) {

            first->m_axis = Step::DescendantAxis;

            first->m_nodeTest = Step::NodeTest(second->m_nodeTest.kind(), second->m_nodeTest.data(), second->m_nodeTest.namespaceURI());

            swap(second->m_nodeTest.mergedPredicates(), first->m_nodeTest.mergedPredicates());

            swap(second->m_predicates, first->m_predicates);

            first->optimize();

            dropSecondStep = true;

        }

    }

}

bool Step::predicatesAreContextListInsensitive() const

{

    for (size_t i = 0; i < m_predicates.size(); ++i) {

        Predicate* predicate = m_predicates[i];

        if (predicate->isContextPositionSensitive() || predicate->isContextSizeSensitive())

            return false;

    }

    for (size_t i = 0; i < m_nodeTest.mergedPredicates().size(); ++i) {

        Predicate* predicate = m_nodeTest.mergedPredicates()[i];

        if (predicate->isContextPositionSensitive() || predicate->isContextSizeSensitive())

            return false;

    }

    return true;

}

void Step::evaluate(Node* context, NodeSet& nodes) const

{

    EvaluationContext& evaluationContext = Expression::evaluationContext();

    evaluationContext.position = 0;

    nodesInAxis(context, nodes);

    // Check predicates that couldn't be merged into node test.

    for (unsigned i = 0; i < m_predicates.size(); i++) {

        Predicate* predicate = m_predicates[i];

        NodeSet newNodes;

        if (!nodes.isSorted())

            newNodes.markSorted(false);

        for (unsigned j = 0; j < nodes.size(); j++) {

            Node* node = nodes[j];

            evaluationContext.node = node;

            evaluationContext.size = nodes.size();

            evaluationContext.position = j + 1;

            if (predicate->evaluate())

                newNodes.append(node);

        }

        nodes.swap(newNodes);

    }

}

static inline Node::NodeType primaryNodeType(Step::Axis axis)

{

    switch (axis) {

        case Step::AttributeAxis:

            return Node::ATTRIBUTE_NODE;

        case Step::NamespaceAxis:

            return Node::XPATH_NAMESPACE_NODE;

        default:

            return Node::ELEMENT_NODE;

    }

}

// Evaluate NodeTest without considering merged predicates.

static inline bool nodeMatchesBasicTest(Node* node, Step::Axis axis, const Step::NodeTest& nodeTest)

{

    switch (nodeTest.kind()) {

        case Step::NodeTest::TextNodeTest:

            return node->nodeType() == Node::TEXT_NODE || node->nodeType() == Node::CDATA_SECTION_NODE;

        case Step::NodeTest::CommentNodeTest:

            return node->nodeType() == Node::COMMENT_NODE;

        case Step::NodeTest::ProcessingInstructionNodeTest: {

            const AtomicString& name = nodeTest.data();

            return node->nodeType() == Node::PROCESSING_INSTRUCTION_NODE && (name.isEmpty() || node->nodeName() == name);

        }

        case Step::NodeTest::AnyNodeTest:

            return true;

        case Step::NodeTest::NameTest: {

            const AtomicString& name = nodeTest.data();

            const AtomicString& namespaceURI = nodeTest.namespaceURI();

            if (axis == Step::AttributeAxis) {

                ASSERT(node->isAttributeNode());

                // In XPath land, namespace nodes are not accessible on the attribute axis.

                if (node->namespaceURI() == XMLNSNames::xmlnsNamespaceURI)

                    return false;

                if (name == starAtom)

                    return namespaceURI.isEmpty() || node->namespaceURI() == namespaceURI;

                return node->localName() == name && node->namespaceURI() == namespaceURI;

            }

            // Node test on the namespace axis is not implemented yet, the caller has a check for it.

            ASSERT(axis != Step::NamespaceAxis);

            // For other axes, the principal node type is element.

            ASSERT(primaryNodeType(axis) == Node::ELEMENT_NODE);

            if (node->nodeType() != Node::ELEMENT_NODE)

                return false;

            if (name == starAtom)

                return namespaceURI.isEmpty() || namespaceURI == node->namespaceURI();

            if (node->document()->isHTMLDocument()) {

                if (node->isHTMLElement()) {

                    // Paths without namespaces should match HTML elements in HTML documents despite those having an XHTML namespace. Names are compared case-insensitively.

                    return equalIgnoringCase(static_cast<Element*>(node)->localName(), name) && (namespaceURI.isNull() || namespaceURI == node->namespaceURI());

                }

                // An expression without any prefix shouldn't match no-namespace nodes (because HTML5 says so).

                return static_cast<Element*>(node)->hasLocalName(name) && namespaceURI == node->namespaceURI() && !namespaceURI.isNull();

            }

            return static_cast<Element*>(node)->hasLocalName(name) && namespaceURI == node->namespaceURI();

        }

    }

    ASSERT_NOT_REACHED();

    return false;

}

static inline bool nodeMatches(Node* node, Step::Axis axis, const Step::NodeTest& nodeTest)

{

    if (!nodeMatchesBasicTest(node, axis, nodeTest))

        return false;

    EvaluationContext& evaluationContext = Expression::evaluationContext();

    // Only the first merged predicate may depend on position.

    ++evaluationContext.position;

    const Vector<Predicate*>& mergedPredicates = nodeTest.mergedPredicates();

    for (unsigned i = 0; i < mergedPredicates.size(); i++) {

        Predicate* predicate = mergedPredicates[i];

        evaluationContext.node = node;

        // No need to set context size - we only get here when evaluating predicates that do not depend on it.

        if (!predicate->evaluate())

            return false;

    }

    return true;

}

// Result nodes are ordered in axis order. Node test (including merged predicates) is applied.

void Step::nodesInAxis(Node* context, NodeSet& nodes) const

{

    ASSERT(nodes.isEmpty());

    switch (m_axis) {

        case ChildAxis:

            if (context->isAttributeNode()) // In XPath model, attribute nodes do not have children.

                return;

            for (Node* n = context->firstChild(); n; n = n->nextSibling())

                if (nodeMatches(n, ChildAxis, m_nodeTest))

                    nodes.append(n);

            return;

        case DescendantAxis:

            if (context->isAttributeNode()) // In XPath model, attribute nodes do not have children.

                return;

            for (Node* n = context->firstChild(); n; n = n->traverseNextNode(context))

                if (nodeMatches(n, DescendantAxis, m_nodeTest))

                    nodes.append(n);

            return;

        case ParentAxis:

            if (context->isAttributeNode()) {

                Node* n = static_cast<Attr*>(context)->ownerElement();

                if (nodeMatches(n, ParentAxis, m_nodeTest))

                    nodes.append(n);

            } else {

                Node* n = context->parentNode();

                if (n && nodeMatches(n, ParentAxis, m_nodeTest))

                    nodes.append(n);

            }

            return;

        case AncestorAxis: {

            Node* n = context;

            if (context->isAttributeNode()) {

                n = static_cast<Attr*>(context)->ownerElement();

                if (nodeMatches(n, AncestorAxis, m_nodeTest))

                    nodes.append(n);

            }

            for (n = n->parentNode(); n; n = n->parentNode())

                if (nodeMatches(n, AncestorAxis, m_nodeTest))

                    nodes.append(n);

            nodes.markSorted(false);

            return;

        }

        case FollowingSiblingAxis:

            if (context->nodeType() == Node::ATTRIBUTE_NODE ||

                 context->nodeType() == Node::XPATH_NAMESPACE_NODE) 

                return;

            for (Node* n = context->nextSibling(); n; n = n->nextSibling())

                if (nodeMatches(n, FollowingSiblingAxis, m_nodeTest))

                    nodes.append(n);

            return;

        case PrecedingSiblingAxis:

            if (context->nodeType() == Node::ATTRIBUTE_NODE ||

                 context->nodeType() == Node::XPATH_NAMESPACE_NODE)

                return;

            for (Node* n = context->previousSibling(); n; n = n->previousSibling())

                if (nodeMatches(n, PrecedingSiblingAxis, m_nodeTest))

                    nodes.append(n);

            nodes.markSorted(false);

            return;

        case FollowingAxis:

            if (context->isAttributeNode()) {

                Node* p = static_cast<Attr*>(context)->ownerElement();

                while ((p = p->traverseNextNode()))

                    if (nodeMatches(p, FollowingAxis, m_nodeTest))

                        nodes.append(p);

            } else {

                for (Node* p = context; !isRootDomNode(p); p = p->parentNode()) {

                    for (Node* n = p->nextSibling(); n; n = n->nextSibling()) {

                        if (nodeMatches(n, FollowingAxis, m_nodeTest))

                            nodes.append(n);

                        for (Node* c = n->firstChild(); c; c = c->traverseNextNode(n))

                            if (nodeMatches(c, FollowingAxis, m_nodeTest))

                                nodes.append(c);

                    }

                }

            }

            return;

        case PrecedingAxis: {

            if (context->isAttributeNode())

                context = static_cast<Attr*>(context)->ownerElement();

            Node* n = context;

            while (Node* parent = n->parent()) {

                for (n = n->traversePreviousNode(); n != parent; n = n->traversePreviousNode())

                    if (nodeMatches(n, PrecedingAxis, m_nodeTest))

                        nodes.append(n);

                n = parent;

            }

            nodes.markSorted(false);

            return;

        }

        case AttributeAxis: {

            if (context->nodeType() != Node::ELEMENT_NODE)

                return;

            // Avoid lazily creating attribute nodes for attributes that we do not need anyway.

            if (m_nodeTest.kind() == NodeTest::NameTest && m_nodeTest.data() != starAtom) {

                RefPtr<Node> n = static_cast<Element*>(context)->getAttributeNodeNS(m_nodeTest.namespaceURI(), m_nodeTest.data());

                if (n && n->namespaceURI() != XMLNSNames::xmlnsNamespaceURI) { // In XPath land, namespace nodes are not accessible on the attribute axis.

                    if (nodeMatches(n.get(), AttributeAxis, m_nodeTest)) // Still need to check merged predicates.

                        nodes.append(n.release());

                }

                return;

            }

            NamedNodeMap* attrs = context->attributes();

            if (!attrs)

                return;

            for (unsigned i = 0; i < attrs->length(); ++i) {

                RefPtr<Attr> attr = attrs->attributeItem(i)->createAttrIfNeeded(static_cast<Element*>(context));

                if (nodeMatches(attr.get(), AttributeAxis, m_nodeTest))

                    nodes.append(attr.release());

            }

            return;

        }

        case NamespaceAxis:

            // XPath namespace nodes are not implemented yet.

            return;

        case SelfAxis:

            if (nodeMatches(context, SelfAxis, m_nodeTest))

                nodes.append(context);

            return;

        case DescendantOrSelfAxis:

            if (nodeMatches(context, DescendantOrSelfAxis, m_nodeTest))

                nodes.append(context);

            if (context->isAttributeNode()) // In XPath model, attribute nodes do not have children.

                return;

            for (Node* n = context->firstChild(); n; n = n->traverseNextNode(context))

            if (nodeMatches(n, DescendantOrSelfAxis, m_nodeTest))

                nodes.append(n);

            return;

        case AncestorOrSelfAxis: {

            if (nodeMatches(context, AncestorOrSelfAxis, m_nodeTest))

                nodes.append(context);

            Node* n = context;

            if (context->isAttributeNode()) {

                n = static_cast<Attr*>(context)->ownerElement();

                if (nodeMatches(n, AncestorOrSelfAxis, m_nodeTest))

                    nodes.append(n);

            }

            for (n = n->parentNode(); n; n = n->parentNode())

                if (nodeMatches(n, AncestorOrSelfAxis, m_nodeTest))

                    nodes.append(n);

            nodes.markSorted(false);

            return;

        }

    }

    ASSERT_NOT_REACHED();

}

}

}

#endif // ENABLE(XPATH)