/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtXmlPatterns module of the Qt Toolkit.
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** ensure the GNU Lesser General Public License version 3 requirements
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** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
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****************************************************************************/

#include "qxsdparticlechecker_p.h"

#include "qxsdelement_p.h"
#include "qxsdmodelgroup_p.h"
#include "qxsdschemahelper_p.h"
#include "qxsdstatemachine_p.h"
#include "qxsdstatemachinebuilder_p.h"
#include "qxsdtypechecker_p.h"

#include <QtCore/QFile>

QT_BEGIN_NAMESPACE

using namespace QPatternist;

namespace QPatternist
{
    /**
     * This template specialization is picked up by XsdStateMachine and allows us
     * to print nice edge labels.
     */
    template <>
    QString XsdStateMachine<XsdTerm::Ptr>::transitionTypeToString(XsdTerm::Ptr term) const
    {
        if (!term)
            return QLatin1String("(empty)");

        if (term->isElement()) {
            return XsdElement::Ptr(term)->displayName(m_namePool);
        } else if (term->isWildcard()) {
            const XsdWildcard::Ptr wildcard(term);
            return QLatin1String("(wildcard)");
        } else {
            return QString();
        }
    }
}

/**
 * This method is used by the isUPAConform method to check whether @p term and @p otherTerm
 * are the same resp. match each other.
 */
static bool termMatches(const XsdTerm::Ptr &term, const XsdTerm::Ptr &otherTerm, const NamePool::Ptr &namePool)
{
    if (term->isElement()) {
        const XsdElement::Ptr element(term);

        if (otherTerm->isElement()) {
            // both, the term and the other term are elements

            const XsdElement::Ptr otherElement(otherTerm);

            // if they have the same name they match
            if (element->name(namePool) == otherElement->name(namePool))
                return true;

        } else if (otherTerm->isWildcard()) {
            // the term is an element and the other term a wildcard

            const XsdWildcard::Ptr wildcard(otherTerm);

            // wildcards using XsdWildcard::absentNamespace, so we have to fix that here
            QXmlName name = element->name(namePool);
            if (name.namespaceURI() == StandardNamespaces::empty)
                name.setNamespaceURI(namePool->allocateNamespace(XsdWildcard::absentNamespace()));

            // if the wildcards namespace constraint allows the elements name, they match
            if (XsdSchemaHelper::wildcardAllowsExpandedName(name, wildcard, namePool))
                return true;
        }
    } else if (term->isWildcard()) {
        const XsdWildcard::Ptr wildcard(term);

        if (otherTerm->isElement()) {
            // the term is a wildcard and the other term an element

            const XsdElement::Ptr otherElement(otherTerm);

            // wildcards using XsdWildcard::absentNamespace, so we have to fix that here
            QXmlName name = otherElement->name(namePool);
            if (name.namespaceURI() == StandardNamespaces::empty)
                name.setNamespaceURI(namePool->allocateNamespace(XsdWildcard::absentNamespace()));

            // if the wildcards namespace constraint allows the elements name, they match
            if (XsdSchemaHelper::wildcardAllowsExpandedName(name, wildcard, namePool))
                return true;

        } else if (otherTerm->isWildcard()) {
            // both, the term and the other term are wildcards

            const XsdWildcard::Ptr otherWildcard(otherTerm);

            // check if the range of the wildcard overlaps.
            const XsdWildcard::Ptr intersectionWildcard = XsdSchemaHelper::wildcardIntersection(wildcard, otherWildcard);
            if (!intersectionWildcard ||
                (intersectionWildcard && !(intersectionWildcard->namespaceConstraint()->variety() != XsdWildcard::NamespaceConstraint::Not && intersectionWildcard->namespaceConstraint()->namespaces().isEmpty())))
                return true;
        }
    }

    return false;
}

/**
 * This method is used by the subsumes algorithm to check whether the @p derivedTerm is validly derived from the @p baseTerm.
 *
 * @param baseTerm The term of the base component (type or group).
 * @param derivedTerm The term of the derived component (type or group).
 * @param particles A hash to map the passed base and derived term to the particles they belong to.
 * @param context The schema context.
 * @param errorMsg The error message in the case that an error occurs.
 */
static bool derivedTermValid(const XsdTerm::Ptr &baseTerm, const XsdTerm::Ptr &derivedTerm, const QHash<XsdTerm::Ptr, XsdParticle::Ptr> &particles, const XsdSchemaContext::Ptr &context, QString &errorMsg)
{
    const NamePool::Ptr namePool(context->namePool());

    // find the particles where the base and derived term belongs to
    const XsdParticle::Ptr baseParticle = particles.value(baseTerm);
    const XsdParticle::Ptr derivedParticle = particles.value(derivedTerm);

    // check that an empty particle can not be derived from a non-empty particle
    if (derivedParticle && baseParticle) {
        if (XsdSchemaHelper::isParticleEmptiable(derivedParticle) && !XsdSchemaHelper::isParticleEmptiable(baseParticle)) {
            errorMsg = QtXmlPatterns::tr("Empty particle cannot be derived from non-empty particle.");
            return false;
        }
    }

    if (baseTerm->isElement()) {
        const XsdElement::Ptr element(baseTerm);

        if (derivedTerm->isElement()) {
            // if both terms are elements

            const XsdElement::Ptr derivedElement(derivedTerm);

            // check names are equal
            if (element->name(namePool) != derivedElement->name(namePool)) {
                errorMsg = QtXmlPatterns::tr("Derived particle is missing element %1.").arg(formatKeyword(element->displayName(namePool)));
                return false;
            }

            // check value constraints are equal (if available)
            if (element->valueConstraint() && element->valueConstraint()->variety() == XsdElement::ValueConstraint::Fixed) {
                if (!derivedElement->valueConstraint()) {
                    errorMsg = QtXmlPatterns::tr("Derived element %1 is missing value constraint as defined in base particle.").arg(formatKeyword(derivedElement->displayName(namePool)));
                    return false;
                }

                if (derivedElement->valueConstraint()->variety() != XsdElement::ValueConstraint::Fixed) {
                    errorMsg = QtXmlPatterns::tr("Derived element %1 has weaker value constraint than base particle.").arg(formatKeyword(derivedElement->displayName(namePool)));
                    return false;
                }

                const QSourceLocation dummyLocation(QUrl(QLatin1String("http://dummy.org")), 1, 1);
                const XsdTypeChecker checker(context, QVector<QXmlName>(), dummyLocation);
                if (!checker.valuesAreEqual(element->valueConstraint()->value(), derivedElement->valueConstraint()->value(), derivedElement->type())) {
                    errorMsg = QtXmlPatterns::tr("Fixed value constraint of element %1 differs from value constraint in base particle.").arg(formatKeyword(derivedElement->displayName(namePool)));
                    return false;
                }
            }

            // check that a derived element can not be nillable if the base element is not nillable
            if (!element->isNillable() && derivedElement->isNillable()) {
                errorMsg = QtXmlPatterns::tr("Derived element %1 cannot be nillable as base element is not nillable.").arg(formatKeyword(derivedElement->displayName(namePool)));
                return false;
            }

            // check that the constraints of the derived element are more strict then the constraints of the base element
            const XsdElement::BlockingConstraints baseConstraints = element->disallowedSubstitutions();
            const XsdElement::BlockingConstraints derivedConstraints = derivedElement->disallowedSubstitutions();
            if (((baseConstraints & XsdElement::RestrictionConstraint) && !(derivedConstraints & XsdElement::RestrictionConstraint)) ||
                ((baseConstraints & XsdElement::ExtensionConstraint) && !(derivedConstraints & XsdElement::ExtensionConstraint)) ||
                ((baseConstraints & XsdElement::SubstitutionConstraint) && !(derivedConstraints & XsdElement::SubstitutionConstraint))) {
                errorMsg = QtXmlPatterns::tr("Block constraints of derived element %1 must not be more weaker than in the base element.").arg(formatKeyword(derivedElement->displayName(namePool)));
                return false;
            }

            // if the type of both elements is the same we can stop testing here
            if (element->type()->name(namePool) == derivedElement->type()->name(namePool))
                return true;

            // check that the type of the derived element can validly derived from the type of the base element
            if (derivedElement->type()->isSimpleType()) {
                if (!XsdSchemaHelper::isSimpleDerivationOk(derivedElement->type(), element->type(), SchemaType::DerivationConstraints())) {
                    errorMsg = QtXmlPatterns::tr("Simple type of derived element %1 cannot be validly derived from base element.").arg(formatKeyword(derivedElement->displayName(namePool)));
                    return false;
                }
            } else if (derivedElement->type()->isComplexType()) {
                if (!XsdSchemaHelper::isComplexDerivationOk(derivedElement->type(), element->type(), SchemaType::DerivationConstraints())) {
                    errorMsg = QtXmlPatterns::tr("Complex type of derived element %1 cannot be validly derived from base element.").arg(formatKeyword(derivedElement->displayName(namePool)));
                    return false;
                }
            }

            // if both, derived and base element, have a complex type that contains a particle itself, apply the subsumes algorithm
            // recursive on their particles
            if (element->type()->isComplexType() && derivedElement->type()->isComplexType()) {
                if (element->type()->isDefinedBySchema() && derivedElement->type()->isDefinedBySchema()) {
                    const XsdComplexType::Ptr baseType(element->type());
                    const XsdComplexType::Ptr derivedType(derivedElement->type());
                    if ((baseType->contentType()->variety() == XsdComplexType::ContentType::ElementOnly ||
                        baseType->contentType()->variety() == XsdComplexType::ContentType::Mixed) &&
                        (derivedType->contentType()->variety() == XsdComplexType::ContentType::ElementOnly ||
                         derivedType->contentType()->variety() == XsdComplexType::ContentType::Mixed)) {

                        return XsdParticleChecker::subsumes(baseType->contentType()->particle(), derivedType->contentType()->particle(), context, errorMsg);
                    }
                }
            }

            return true;
        } else if (derivedTerm->isWildcard()) {
            // derive a wildcard from an element is not allowed
            errorMsg = QtXmlPatterns::tr("Element %1 is missing in derived particle.").arg(formatKeyword(element->displayName(namePool)));
            return false;
        }
    } else if (baseTerm->isWildcard()) {
        const XsdWildcard::Ptr wildcard(baseTerm);

        if (derivedTerm->isElement()) {
            // the base term is a wildcard and derived term an element

            const XsdElement::Ptr derivedElement(derivedTerm);

            // wildcards using XsdWildcard::absentNamespace, so we have to fix that here
            QXmlName name = derivedElement->name(namePool);
            if (name.namespaceURI() == StandardNamespaces::empty)
                name.setNamespaceURI(namePool->allocateNamespace(XsdWildcard::absentNamespace()));

            // check that name of the element is allowed by the wildcards namespace constraint
            if (!XsdSchemaHelper::wildcardAllowsExpandedName(name, wildcard, namePool)) {
                errorMsg = QtXmlPatterns::tr("Element %1 does not match namespace constraint of wildcard in base particle.").arg(formatKeyword(derivedElement->displayName(namePool)));
                return false;
            }

        } else if (derivedTerm->isWildcard()) {
            // both, derived and base term are wildcards

            const XsdWildcard::Ptr derivedWildcard(derivedTerm);

            // check that the derived wildcard is a valid subset of the base wildcard
            if (!XsdSchemaHelper::isWildcardSubset(derivedWildcard, wildcard)) {
                errorMsg = QtXmlPatterns::tr("Wildcard in derived particle is not a valid subset of wildcard in base particle.");
                return false;
            }

            if (!XsdSchemaHelper::checkWildcardProcessContents(wildcard, derivedWildcard)) {
                errorMsg = QtXmlPatterns::tr("processContent of wildcard in derived particle is weaker than wildcard in base particle.");
                return false;
            }
        }

        return true;
    }

    return false;
}

typedef QHash<QXmlName, XsdElement::Ptr> ElementHash;

/**
 * Internal helper method that checks if the given @p particle contains an element with the
 * same name and type twice.
 */
static bool hasDuplicatedElementsInternal(const XsdParticle::Ptr &particle, const NamePool::Ptr &namePool, ElementHash &hash, XsdElement::Ptr &conflictingElement)
{
    const XsdTerm::Ptr term = particle->term();
    if (term->isElement()) {
        const XsdElement::Ptr mainElement(term);
        XsdElement::List substGroups = mainElement->substitutionGroups();
        if (substGroups.isEmpty())
            substGroups << mainElement;

        for (int i = 0; i < substGroups.count(); ++i) {
            const XsdElement::Ptr element = substGroups.at(i);
            if (hash.contains(element->name(namePool))) {
                if (element->type()->name(namePool) != hash.value(element->name(namePool))->type()->name(namePool)) {
                    conflictingElement = element;
                    return true;
                }
            } else {
                hash.insert(element->name(namePool), element);
            }
        }
    } else if (term->isModelGroup()) {
        const XsdModelGroup::Ptr group(term);
        const XsdParticle::List particles = group->particles();
        for (int i = 0; i < particles.count(); ++i) {
            if (hasDuplicatedElementsInternal(particles.at(i), namePool, hash, conflictingElement))
                return true;
        }
    }

    return false;
}

bool XsdParticleChecker::hasDuplicatedElements(const XsdParticle::Ptr &particle, const NamePool::Ptr &namePool, XsdElement::Ptr &conflictingElement)
{
    ElementHash hash;
    return hasDuplicatedElementsInternal(particle, namePool, hash, conflictingElement);
}

bool XsdParticleChecker::isUPAConform(const XsdParticle::Ptr &particle, const NamePool::Ptr &namePool)
{

    /**
     * In case we encounter an <xsd:all> element, don't construct a state machine, but use the approach
     * described at http://www.w3.org/TR/xmlschema-1/#non-ambig
     * Reason: For n elements inside the <xsd:all>, represented in the NDA, the state machine
     * constructs n! states in the DFA, which does not scale.
     */
    if (particle->term()->isModelGroup()) {
        const XsdModelGroup::Ptr group(particle->term());
        if (group->compositor() == XsdModelGroup::AllCompositor)
            return isUPAConformXsdAll(particle, namePool);
    }

    /**
     * The algorithm is implemented like described in http://www.ltg.ed.ac.uk/~ht/XML_Europe_2003.html#S2.2
     */

    // create a state machine for the given particle
    XsdStateMachine<XsdTerm::Ptr> stateMachine(namePool);

    XsdStateMachineBuilder builder(&stateMachine, namePool);
    const XsdStateMachine<XsdTerm::Ptr>::StateId endState = builder.reset();
    const XsdStateMachine<XsdTerm::Ptr>::StateId startState = builder.buildParticle(particle, endState);
    builder.addStartState(startState);

/*
    static int counter = 0;
    {
        QFile file(QString("/tmp/file_upa%1.dot").arg(counter));
        file.open(QIODevice::WriteOnly);
        stateMachine.outputGraph(&file, "Base");
        file.close();
    }
    ::system(QString("dot -Tpng /tmp/file_upa%1.dot -o/tmp/file_upa%1.png").arg(counter).toLatin1().data());
*/
    const XsdStateMachine<XsdTerm::Ptr> dfa = stateMachine.toDFA();
/*
    {
        QFile file(QString("/tmp/file_upa%1dfa.dot").arg(counter));
        file.open(QIODevice::WriteOnly);
        dfa.outputGraph(&file, "Base");
        file.close();
    }
    ::system(QString("dot -Tpng /tmp/file_upa%1dfa.dot -o/tmp/file_upa%1dfa.png").arg(counter).toLatin1().data());
*/
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateType> states = dfa.states();
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > > transitions = dfa.transitions();

    // the basic idea of that algorithm is to iterate over all states of that machine and check that no two edges
    // that match on the same term leave a state, so for a given term it should always be obvious which edge to take
    for (auto stateIt = states.cbegin(), end = states.cend(); stateIt != end; ++stateIt) {
        // fetch all transitions the current state allows
        const QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > currentTransitions = transitions.value(stateIt.key());
        for (auto transitionIt = currentTransitions.cbegin(), end = currentTransitions.cend(); transitionIt != end; ++transitionIt) {
            if (transitionIt.value().size() > 1) {
                // we have one state with two edges leaving it, that means
                // the XsdTerm::Ptr exists twice, that is an error
                return false;
            }

            for (auto innerTransitionIt = currentTransitions.cbegin(), end = currentTransitions.cend(); innerTransitionIt != end; ++innerTransitionIt) {

                if (transitionIt.key() == innerTransitionIt.key()) // do no compare with ourself
                    continue;

                // use the helper method termMatches to check if both term matches
                if (termMatches(transitionIt.key(), innerTransitionIt.key(), namePool))
                    return false;
            }
        }
    }

    return true;
}

bool XsdParticleChecker::isUPAConformXsdAll(const XsdParticle::Ptr &particle, const NamePool::Ptr &namePool)
{
    /**
     * see http://www.w3.org/TR/xmlschema-1/#non-ambig
     */
    const XsdModelGroup::Ptr group(particle->term());
    const XsdParticle::List particles = group->particles();
    const int count = particles.count();
    for (int left = 0; left < count; ++left) {
        for (int right = left+1; right < count; ++right) {
            if (termMatches(particles.at(left)->term(), particles.at(right)->term(), namePool))
                return false;
        }
    }
    return true;
}

bool XsdParticleChecker::subsumes(const XsdParticle::Ptr &particle, const XsdParticle::Ptr &derivedParticle, const XsdSchemaContext::Ptr &context, QString &errorMsg)
{
    /**
     * The algorithm is implemented like described in http://www.ltg.ed.ac.uk/~ht/XML_Europe_2003.html#S2.3
     */

    const NamePool::Ptr namePool(context->namePool());

    XsdStateMachine<XsdTerm::Ptr> baseStateMachine(namePool);
    XsdStateMachine<XsdTerm::Ptr> derivedStateMachine(namePool);

    // build up state machines for both particles
    {
        XsdStateMachineBuilder builder(&baseStateMachine, namePool);
        const XsdStateMachine<XsdTerm::Ptr>::StateId endState = builder.reset();
        const XsdStateMachine<XsdTerm::Ptr>::StateId startState = builder.buildParticle(particle, endState);
        builder.addStartState(startState);

        baseStateMachine = baseStateMachine.toDFA();
    }
    {
        XsdStateMachineBuilder builder(&derivedStateMachine, namePool);
        const XsdStateMachine<XsdTerm::Ptr>::StateId endState = builder.reset();
        const XsdStateMachine<XsdTerm::Ptr>::StateId startState = builder.buildParticle(derivedParticle, endState);
        builder.addStartState(startState);

        derivedStateMachine = derivedStateMachine.toDFA();
    }

    QHash<XsdTerm::Ptr, XsdParticle::Ptr> particlesHash = XsdStateMachineBuilder::particleLookupMap(particle);
    particlesHash.insert(XsdStateMachineBuilder::particleLookupMap(derivedParticle));

/*
    static int counter = 0;
    {
        QFile file(QString("/tmp/file_base%1.dot").arg(counter));
        file.open(QIODevice::WriteOnly);
        baseStateMachine.outputGraph(&file, QLatin1String("Base"));
        file.close();
    }
    {
        QFile file(QString("/tmp/file_derived%1.dot").arg(counter));
        file.open(QIODevice::WriteOnly);
        derivedStateMachine.outputGraph(&file, QLatin1String("Base"));
        file.close();
    }
    ::system(QString("dot -Tpng /tmp/file_base%1.dot -o/tmp/file_base%1.png").arg(counter).toLatin1().data());
    ::system(QString("dot -Tpng /tmp/file_derived%1.dot -o/tmp/file_derived%1.png").arg(counter).toLatin1().data());
*/

    const XsdStateMachine<XsdTerm::Ptr>::StateId baseStartState = baseStateMachine.startState();
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateType> baseStates = baseStateMachine.states();
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > > baseTransitions = baseStateMachine.transitions();

    const XsdStateMachine<XsdTerm::Ptr>::StateId derivedStartState = derivedStateMachine.startState();
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateType> derivedStates = derivedStateMachine.states();
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > > derivedTransitions = derivedStateMachine.transitions();

    // @see http://www.ltg.ed.ac.uk/~ht/XML_Europe_2003.html#S2.3.1

    // define working set
    QList<QPair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId> > workSet;
    QList<QPair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId> > processedSet;

    // 1) fill working set initially with start states
    workSet.append(qMakePair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId>(baseStartState, derivedStartState));
    processedSet.append(qMakePair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId>(baseStartState, derivedStartState));

    while (!workSet.isEmpty()) { // while there are state sets to process

        // 3) dequeue on state set
        const QPair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId> set = workSet.takeFirst();

        const QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > derivedTrans = derivedTransitions.value(set.second);

        const QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > baseTrans = baseTransitions.value(set.first);

        for (auto derivedIt = derivedTrans.cbegin(), end = derivedTrans.cend(); derivedIt != end; ++derivedIt) {

            bool found = false;
            for (auto baseIt = baseTrans.cbegin(), end = baseTrans.cend(); baseIt != end; ++baseIt) {
                if (derivedTermValid(baseIt.key(), derivedIt.key(), particlesHash, context, errorMsg)) {
                    const QPair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId> endSet =
                             qMakePair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId>(baseIt.value().first(), derivedIt.value().first());
                    if (!processedSet.contains(endSet) && !workSet.contains(endSet)) {
                        workSet.append(endSet);
                        processedSet.append(endSet);
                    }

                    found = true;
                }
            }

            if (!found) {
                return false;
            }
        }
    }

    // 5)
    for (auto it = derivedStates.cbegin(), end = derivedStates.cend(); it != end; ++it) {
        if (it.value() == XsdStateMachine<XsdTerm::Ptr>::EndState || it.value() == XsdStateMachine<XsdTerm::Ptr>::StartEndState) {
            for (int i = 0; i < processedSet.count(); ++i) {
                if (processedSet.at(i).second == it.key() &&
                    (baseStates.value(processedSet.at(i).first) != XsdStateMachine<XsdTerm::Ptr>::EndState &&
                     baseStates.value(processedSet.at(i).first) != XsdStateMachine<XsdTerm::Ptr>::StartEndState)) {
                    errorMsg = QtXmlPatterns::tr("Derived particle allows content that is not allowed in the base particle.");
                    return false;
                }
            }
        }
    }

    return true;
}

QT_END_NAMESPACE
