/****************************************************************************
**
** Copyright (C) 2015 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing
**
** This file is part of the Qt Build Suite.
**
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
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** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 or version 3 as published by the Free
** Software Foundation and appearing in the file LICENSE.LGPLv21 and
** LICENSE.LGPLv3 included in the packaging of this file.  Please review the
** following information to ensure the GNU Lesser General Public License
** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, The Qt Company gives you certain additional
** rights.  These rights are described in The Qt Company LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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****************************************************************************/
#include "executor.h"

#include "buildgraph.h"
#include "command.h"
#include "emptydirectoriesremover.h"
#include "productbuilddata.h"
#include "projectbuilddata.h"
#include "cycledetector.h"
#include "executorjob.h"
#include "inputartifactscanner.h"
#include "productinstaller.h"
#include "rescuableartifactdata.h"
#include "rulenode.h"
#include "rulesevaluationcontext.h"

#include <buildgraph/transformer.h>
#include <language/language.h>
#include <language/scriptengine.h>
#include <logging/translator.h>
#include <tools/error.h>
#include <tools/fileinfo.h>
#include <tools/progressobserver.h>
#include <tools/qbsassert.h>

#include <QDir>
#include <QPair>
#include <QSet>
#include <QTimer>

#include <algorithm>
#include <climits>

namespace qbs {
namespace Internal {

bool Executor::ComparePriority::operator() (const BuildGraphNode *x, const BuildGraphNode *y) const
{
    return x->product->buildData->buildPriority < y->product->buildData->buildPriority;
}


Executor::Executor(const Logger &logger, QObject *parent)
    : QObject(parent)
    , m_productInstaller(0)
    , m_logger(logger)
    , m_progressObserver(0)
    , m_state(ExecutorIdle)
    , m_cancelationTimer(new QTimer(this))
    , m_doTrace(logger.traceEnabled())
    , m_doDebug(logger.debugEnabled())
{
    m_inputArtifactScanContext = new InputArtifactScannerContext(&m_scanResultCache);
    m_cancelationTimer->setSingleShot(false);
    m_cancelationTimer->setInterval(1000);
    connect(m_cancelationTimer, SIGNAL(timeout()), SLOT(checkForCancellation()));
}

Executor::~Executor()
{
    // jobs must be destroyed before deleting the shared scan result cache
    foreach (ExecutorJob *job, m_availableJobs)
        delete job;
    foreach (ExecutorJob *job, m_processingJobs.keys())
        delete job;
    delete m_inputArtifactScanContext;
    delete m_productInstaller;
}

FileTime Executor::recursiveFileTime(const QString &filePath) const
{
    FileTime newest;
    FileInfo fileInfo(filePath);
    if (!fileInfo.exists()) {
        const QString nativeFilePath = QDir::toNativeSeparators(filePath);
        m_logger.qbsWarning() << Tr::tr("File '%1' not found.").arg(nativeFilePath);
        return newest;
    }
    newest = qMax(fileInfo.lastModified(), fileInfo.lastStatusChange());
    if (!fileInfo.isDir())
        return newest;
    const QStringList dirContents = QDir(filePath)
            .entryList(QDir::Files | QDir::Dirs | QDir::NoDotAndDotDot);
    foreach (const QString &curFileName, dirContents) {
        const FileTime ft = recursiveFileTime(filePath + QLatin1Char('/') + curFileName);
        if (ft > newest)
            newest = ft;
    }
    return newest;
}

void Executor::retrieveSourceFileTimestamp(Artifact *artifact) const
{
    QBS_CHECK(artifact->artifactType == Artifact::SourceFile);

    if (m_buildOptions.changedFiles().isEmpty())
        artifact->setTimestamp(recursiveFileTime(artifact->filePath()));
    else if (m_buildOptions.changedFiles().contains(artifact->filePath()))
        artifact->setTimestamp(FileTime::currentTime());
    else if (!artifact->timestamp().isValid())
        artifact->setTimestamp(recursiveFileTime(artifact->filePath()));

    artifact->timestampRetrieved = true;
}

void Executor::build()
{
    try {
        doBuild();
    } catch (const ErrorInfo &e) {
        handleError(e);
    }
}

void Executor::setProject(const TopLevelProjectPtr &project)
{
    m_project = project;
}

void Executor::setProducts(const QList<ResolvedProductPtr> &productsToBuild)
{
    m_productsToBuild = productsToBuild;
}

class ProductPrioritySetter
{
    const TopLevelProject *m_topLevelProject;
    unsigned int m_priority;
    QSet<ResolvedProductPtr> m_seenProducts;
public:
    ProductPrioritySetter(const TopLevelProject *tlp)
        : m_topLevelProject(tlp)
    {
    }

    void apply()
    {
        QList<ResolvedProductPtr> allProducts = m_topLevelProject->allProducts();
        QSet<ResolvedProductPtr> allDependencies;
        foreach (const ResolvedProductPtr &product, allProducts)
            allDependencies += product->dependencies;
        QSet<ResolvedProductPtr> rootProducts = allProducts.toSet() - allDependencies;
        m_priority = UINT_MAX;
        m_seenProducts.clear();
        foreach (const ResolvedProductPtr &rootProduct, rootProducts)
            traverse(rootProduct);
    }

private:
    void traverse(const ResolvedProductPtr &product)
    {
        if (m_seenProducts.contains(product))
            return;
        m_seenProducts += product;
        foreach (const ResolvedProductPtr &dependency, product->dependencies)
            traverse(dependency);
        if (!product->buildData)
            return;
        product->buildData->buildPriority = m_priority--;
    }
};

void Executor::doBuild()
{
    if (m_buildOptions.maxJobCount() <= 0) {
        m_buildOptions.setMaxJobCount(BuildOptions::defaultMaxJobCount());
        m_logger.qbsDebug() << "max job count not explicitly set, using value of "
                            << m_buildOptions.maxJobCount();
    }
    QBS_CHECK(m_state == ExecutorIdle);
    m_leaves = Leaves();
    m_changedSourceArtifacts.clear();
    m_error.clear();
    m_explicitlyCanceled = false;
    m_activeFileTags = FileTags::fromStringList(m_buildOptions.activeFileTags());
    m_artifactsRemovedFromDisk.clear();
    setState(ExecutorRunning);

    if (m_productsToBuild.isEmpty()) {
        m_logger.qbsTrace() << "No products to build, finishing.";
        QTimer::singleShot(0, this, SLOT(finish())); // Don't call back on the caller.
        return;
    }

    doSanityChecks();
    m_evalContext = m_project->buildData->evaluationContext;
    if (!m_evalContext) { // Is null before the first build.
        m_evalContext = RulesEvaluationContextPtr(new RulesEvaluationContext(m_logger));
        m_project->buildData->evaluationContext = m_evalContext;
    }


    InstallOptions installOptions;
    installOptions.setDryRun(m_buildOptions.dryRun());
    installOptions.setInstallRoot(m_productsToBuild.first()->moduleProperties
                                  ->qbsPropertyValue(QLatin1String("installRoot")).toString());
    installOptions.setKeepGoing(m_buildOptions.keepGoing());
    m_productInstaller = new ProductInstaller(m_project, m_productsToBuild, installOptions,
                                              m_progressObserver, m_logger);
    if (m_buildOptions.removeExistingInstallation())
        m_productInstaller->removeInstallRoot();

    addExecutorJobs();
    prepareAllNodes();
    prepareProducts();
    setupRootNodes();
    prepareReachableNodes();
    setupProgressObserver();
    initLeaves();
    if (!scheduleJobs()) {
        m_logger.qbsTrace() << "Nothing to do at all, finishing.";
        QTimer::singleShot(0, this, SLOT(finish())); // Don't call back on the caller.
    }
    if (m_progressObserver)
        m_cancelationTimer->start();
}

void Executor::setBuildOptions(const BuildOptions &buildOptions)
{
    m_buildOptions = buildOptions;
}


void Executor::initLeaves()
{
    updateLeaves(m_roots);
}

void Executor::updateLeaves(const NodeSet &nodes)
{
    NodeSet seenNodes;
    foreach (BuildGraphNode * const node, nodes)
        updateLeaves(node, seenNodes);
}

void Executor::updateLeaves(BuildGraphNode *node, NodeSet &seenNodes)
{
    if (seenNodes.contains(node))
        return;
    seenNodes += node;

    // Artifacts that appear in the build graph after
    // prepareBuildGraph() has been called, must be initialized.
    if (node->buildState == BuildGraphNode::Untouched) {
        node->buildState = BuildGraphNode::Buildable;
        Artifact *artifact = dynamic_cast<Artifact *>(node);
        if (artifact && artifact->artifactType == Artifact::SourceFile)
            retrieveSourceFileTimestamp(artifact);
    }

    bool isLeaf = true;
    foreach (BuildGraphNode *child, node->children) {
        if (child->buildState != BuildGraphNode::Built) {
            isLeaf = false;
            updateLeaves(child, seenNodes);
        }
    }

    if (isLeaf) {
        if (m_doDebug)
            m_logger.qbsDebug() << "[EXEC] adding leaf " << node->toString();
        m_leaves.push(node);
    }
}

// Returns true if some artifacts are still waiting to be built or currently building.
bool Executor::scheduleJobs()
{
    QBS_CHECK(m_state == ExecutorRunning);
    while (!m_leaves.empty() && !m_availableJobs.isEmpty()) {
        BuildGraphNode * const nodeToBuild = m_leaves.top();
        m_leaves.pop();

        switch (nodeToBuild->buildState) {
        case BuildGraphNode::Untouched:
            QBS_ASSERT(!"untouched node in leaves list",
                       qDebug("%s", qPrintable(nodeToBuild->toString())));
            break;
        case BuildGraphNode::Buildable:
            // This is the only state in which we want to build a node.
            nodeToBuild->accept(this);
            break;
        case BuildGraphNode::Building:
            if (m_doDebug) {
                m_logger.qbsDebug() << "[EXEC] " << nodeToBuild->toString();
                m_logger.qbsDebug() << "[EXEC] node is currently being built. Skipping.";
            }
            break;
        case BuildGraphNode::Built:
            if (m_doDebug) {
                m_logger.qbsDebug() << "[EXEC] " << nodeToBuild->toString();
                m_logger.qbsDebug() << "[EXEC] node already built. Skipping.";
            }
            break;
        }
    }
    return !m_leaves.empty() || !m_processingJobs.isEmpty();
}

bool Executor::isUpToDate(Artifact *artifact) const
{
    QBS_CHECK(artifact->artifactType == Artifact::Generated);

    if (m_doDebug) {
        m_logger.qbsDebug() << "[UTD] check " << artifact->filePath() << " "
                            << artifact->timestamp().toString();
    }

    if (m_buildOptions.forceTimestampCheck()) {
        artifact->setTimestamp(FileInfo(artifact->filePath()).lastModified());
        if (m_doDebug) {
            m_logger.qbsDebug() << "[UTD] timestamp retrieved from filesystem: "
                                << artifact->timestamp().toString();
        }
    }

    if (!artifact->timestamp().isValid()) {
        if (m_doDebug)
            m_logger.qbsDebug() << "[UTD] invalid timestamp. Out of date.";
        return false;
    }

    foreach (Artifact *childArtifact, ArtifactSet::fromNodeSet(artifact->children)) {
        QBS_CHECK(childArtifact->timestamp().isValid());
        if (m_doDebug) {
            m_logger.qbsDebug() << "[UTD] child timestamp "
                                << childArtifact->timestamp().toString() << " "
                                << childArtifact->filePath();
        }
        if (artifact->timestamp() < childArtifact->timestamp())
            return false;
    }

    foreach (FileDependency *fileDependency, artifact->fileDependencies) {
        if (!fileDependency->timestamp().isValid()) {
            FileInfo fi(fileDependency->filePath());
            fileDependency->setTimestamp(fi.lastModified());
            if (!fileDependency->timestamp().isValid()) {
                if (m_doDebug) {
                    m_logger.qbsDebug() << "[UTD] file dependency doesn't exist "
                                        << fileDependency->filePath();
                }
                return false;
            }
        }
        if (m_doDebug) {
            m_logger.qbsDebug() << "[UTD] file dependency timestamp "
                                << fileDependency->timestamp().toString() << " "
                                << fileDependency->filePath();
        }
        if (artifact->timestamp() < fileDependency->timestamp())
            return false;
    }

    return true;
}

bool Executor::mustExecuteTransformer(const TransformerPtr &transformer) const
{
    bool hasAlwaysUpdatedArtifacts = false;
    foreach (Artifact *artifact, transformer->outputs) {
        if (artifact->alwaysUpdated)
            hasAlwaysUpdatedArtifacts = true;
        else if (!m_buildOptions.forceTimestampCheck())
            continue;
        const bool upToDate = isUpToDate(artifact);

        // The invariant is that all output artifacts of a transformer have the same
        // "virtual" timestamp. However, if the user requested that on-disk timestamps be evaluated,
        // they can differ and the oldest output file of the transformer decides.
        if (!upToDate || !m_buildOptions.forceTimestampCheck())
            return !upToDate;
    }

    // If all artifacts in a transformer have "alwaysUpdated" set to false, that transformer
    // is always run.
    return !hasAlwaysUpdatedArtifacts;
}

void Executor::buildArtifact(Artifact *artifact)
{
    if (m_doDebug)
        m_logger.qbsDebug() << "[EXEC] " << relativeArtifactFileName(artifact);

    QBS_CHECK(artifact->buildState == BuildGraphNode::Buildable);

    // skip artifacts without transformer
    if (artifact->artifactType != Artifact::Generated) {
        // For source artifacts, that were not reachable when initializing the build, we must
        // retrieve timestamps. This can happen, if a dependency that's added during the build
        // makes the source artifact reachable.
        if (artifact->artifactType == Artifact::SourceFile && !artifact->timestampRetrieved)
            retrieveSourceFileTimestamp(artifact);

        if (m_doDebug)
            m_logger.qbsDebug() << QString::fromLocal8Bit("[EXEC] artifact type %1. Skipping.")
                                   .arg(toString(artifact->artifactType));
        finishArtifact(artifact);
        return;
    }

    // Every generated artifact must have a transformer.
    QBS_CHECK(artifact->transformer);
    potentiallyRunTransformer(artifact->transformer);
}

void Executor::executeRuleNode(RuleNode *ruleNode)
{
    ArtifactSet changedInputArtifacts;
    if (ruleNode->rule()->isDynamic()) {
        foreach (Artifact *artifact, m_changedSourceArtifacts) {
            if (artifact->product != ruleNode->product)
                continue;
            if (ruleNode->rule()->acceptsAsInput(artifact))
                changedInputArtifacts += artifact;
        }
        foreach (Artifact *artifact,
                ArtifactSet::fromNodeSet(ruleNode->product->buildData->nodes)) {
            if (artifact->artifactType == Artifact::SourceFile)
                continue;
            if (artifact->timestampRetrieved && !isUpToDate(artifact)
                    && ruleNode->rule()->acceptsAsInput(artifact)) {
                changedInputArtifacts += artifact;
            }
        }
    }

    RuleNode::ApplicationResult result;
    ruleNode->apply(m_logger, changedInputArtifacts, &result);

    if (result.upToDate) {
        if (m_doDebug)
            m_logger.qbsDebug() << "[EXEC] " << ruleNode->toString()
                                << " is up to date. Skipping.";
    } else {
        if (m_doDebug)
            m_logger.qbsDebug() << "[EXEC] " << ruleNode->toString();
        const WeakPointer<ResolvedProduct> &product = ruleNode->product;
        QSet<RuleNode *> parentRules;
        if (!result.createdNodes.isEmpty()) {
            foreach (BuildGraphNode *parent, ruleNode->parents) {
                if (RuleNode *parentRule = dynamic_cast<RuleNode *>(parent))
                    parentRules += parentRule;
            }
        }
        foreach (BuildGraphNode *node, result.createdNodes) {
            if (m_doDebug)
                m_logger.qbsDebug() << "[EXEC] rule created " << node->toString();
            loggedConnect(node, ruleNode, m_logger);
            Artifact *outputArtifact = dynamic_cast<Artifact *>(node);
            if (!outputArtifact)
                continue;
            if (outputArtifact->fileTags().matches(product->fileTags))
                product->buildData->roots += outputArtifact;

            foreach (Artifact *inputArtifact, outputArtifact->transformer->inputs)
                loggedConnect(ruleNode, inputArtifact, m_logger);

            foreach (RuleNode *parentRule, parentRules)
                loggedConnect(parentRule, outputArtifact, m_logger);
        }
        updateLeaves(result.createdNodes);
        updateLeaves(result.invalidatedNodes);
    }
    finishNode(ruleNode);
    if (m_progressObserver)
        m_progressObserver->incrementProgressValue();
}

void Executor::finishJob(ExecutorJob *job, bool success)
{
    QBS_CHECK(job);
    QBS_CHECK(m_state != ExecutorIdle);

    const JobMap::Iterator it = m_processingJobs.find(job);
    QBS_CHECK(it != m_processingJobs.end());
    const TransformerPtr transformer = it.value();
    if (success) {
        m_project->buildData->isDirty = true;
        foreach (Artifact *artifact, transformer->outputs) {
            if (artifact->alwaysUpdated)
                artifact->setTimestamp(FileTime::currentTime());
            else
                artifact->setTimestamp(FileInfo(artifact->filePath()).lastModified());
        }
        finishTransformer(transformer);
    }
    m_processingJobs.erase(it);
    m_availableJobs.append(job);

    if (!success && !m_buildOptions.keepGoing())
        cancelJobs();

    if (m_state == ExecutorRunning && m_progressObserver && m_progressObserver->canceled()) {
        m_logger.qbsTrace() << "Received cancel request; canceling build.";
        m_explicitlyCanceled = true;
        cancelJobs();
    }

    if (m_state == ExecutorCanceling) {
        if (m_processingJobs.isEmpty()) {
            m_logger.qbsTrace() << "All pending jobs are done, finishing.";
            finish();
        }
        return;
    }

    if (!scheduleJobs()) {
        m_logger.qbsTrace() << "Nothing left to build; finishing.";
        finish();
    }
}

static bool allChildrenBuilt(BuildGraphNode *node)
{
    foreach (BuildGraphNode *child, node->children)
        if (child->buildState != BuildGraphNode::Built)
            return false;
    return true;
}

void Executor::finishNode(BuildGraphNode *leaf)
{
    leaf->buildState = BuildGraphNode::Built;
    foreach (BuildGraphNode *parent, leaf->parents) {
        if (parent->buildState != BuildGraphNode::Buildable) {
            if (m_doTrace) {
                m_logger.qbsTrace() << "[EXEC] parent " << parent->toString()
                                    << " build state: " << toString(parent->buildState);
            }
            continue;
        }

        if (allChildrenBuilt(parent)) {
            m_leaves.push(parent);
            if (m_doTrace) {
                m_logger.qbsTrace() << "[EXEC] finishNode adds leaf "
                        << parent->toString() << " " << toString(parent->buildState);
            }
        } else {
            if (m_doTrace) {
                m_logger.qbsTrace() << "[EXEC] parent " << parent->toString()
                                    << " build state: " << toString(parent->buildState);
            }
        }
    }
}

void Executor::finishArtifact(Artifact *leaf)
{
    QBS_CHECK(leaf);
    if (m_doTrace)
        m_logger.qbsTrace() << "[EXEC] finishArtifact " << relativeArtifactFileName(leaf);

    finishNode(leaf);
    m_scanResultCache.remove(leaf->filePath());
}

QString Executor::configString() const
{
    return tr(" for configuration %1").arg(m_project->id());
}

bool Executor::transformerHasMatchingOutputTags(const TransformerConstPtr &transformer) const
{
    if (m_activeFileTags.isEmpty())
        return true; // No filtering requested.

    foreach (Artifact * const output, transformer->outputs) {
        if (m_activeFileTags.matches(output->fileTags()))
            return true;
    }

    return false;
}

bool Executor::transformerHasMatchingInputFiles(const TransformerConstPtr &transformer) const
{
    if (m_buildOptions.filesToConsider().isEmpty())
        return true; // No filtering requested.

    foreach (const Artifact * const input, transformer->inputs) {
        foreach (const QString &filePath, m_buildOptions.filesToConsider()) {
            if (input->filePath() == filePath)
                return true;
        }
    }

    return false;
}

void Executor::cancelJobs()
{
    m_logger.qbsTrace() << "Canceling all jobs.";
    setState(ExecutorCanceling);
    QList<ExecutorJob *> jobs = m_processingJobs.keys();
    foreach (ExecutorJob *job, jobs)
        job->cancel();
}

void Executor::setupProgressObserver()
{
    if (!m_progressObserver)
        return;
    int totalEffort = 1; // For the effort after the last rule application;
    foreach (const ResolvedProductConstPtr &product, m_productsToBuild) {
        QBS_CHECK(product->buildData);
        foreach (const BuildGraphNode * const node, product->buildData->nodes) {
            const RuleNode * const ruleNode = dynamic_cast<const RuleNode *>(node);
            if (ruleNode)
                ++totalEffort;
        }
    }
    m_progressObserver->initialize(tr("Building%1").arg(configString()), totalEffort);
}

void Executor::doSanityChecks()
{
    QBS_CHECK(m_project);
    QBS_CHECK(!m_productsToBuild.isEmpty());
    foreach (const ResolvedProductConstPtr &product, m_productsToBuild) {
        QBS_CHECK(product->buildData);
        QBS_CHECK(product->topLevelProject() == m_project);
    }
}

void Executor::handleError(const ErrorInfo &error)
{
    m_error.append(error.toString());
    if (m_processingJobs.isEmpty())
        finish();
    else
        cancelJobs();
}

void Executor::addExecutorJobs()
{
    m_logger.qbsDebug() << QString::fromLocal8Bit("[EXEC] preparing executor for %1 jobs "
                                                  "in parallel").arg(m_buildOptions.maxJobCount());
    for (int i = 1; i <= m_buildOptions.maxJobCount(); i++) {
        ExecutorJob *job = new ExecutorJob(m_logger, this);
        job->setMainThreadScriptEngine(m_evalContext->engine());
        job->setObjectName(QString::fromLatin1("J%1").arg(i));
        job->setDryRun(m_buildOptions.dryRun());
        job->setEchoMode(m_buildOptions.echoMode());
        m_availableJobs.append(job);
        connect(job, SIGNAL(reportCommandDescription(QString,QString)),
                this, SIGNAL(reportCommandDescription(QString,QString)), Qt::QueuedConnection);
        connect(job, SIGNAL(reportProcessResult(qbs::ProcessResult)),
                this, SIGNAL(reportProcessResult(qbs::ProcessResult)), Qt::QueuedConnection);
        connect(job, SIGNAL(finished(qbs::ErrorInfo)),
                this, SLOT(onJobFinished(qbs::ErrorInfo)), Qt::QueuedConnection);
    }
}

void Executor::rescueOldBuildData(Artifact *artifact, bool *childrenAdded = 0)
{
    if (childrenAdded)
        *childrenAdded = false;
    if (!artifact->oldDataPossiblyPresent)
        return;
    artifact->oldDataPossiblyPresent = false;
    if (artifact->artifactType != Artifact::Generated)
        return;

    ResolvedProduct * const product = artifact->product.data();
    AllRescuableArtifactData::Iterator it
            = product->buildData->rescuableArtifactData.find(artifact->filePath());
    if (it == product->buildData->rescuableArtifactData.end())
        return;

    const RescuableArtifactData &rad = it.value();
    if (m_logger.traceEnabled()) {
        m_logger.qbsTrace() << QString::fromLocal8Bit("[BG] Attempting to rescue data of "
                                                      "artifact '%1'").arg(artifact->fileName());
    }

    typedef QPair<Artifact *, bool> ChildArtifactData;
    QList<ChildArtifactData> childrenToConnect;
    bool canRescue = commandListsAreEqual(artifact->transformer->commands, rad.commands);
    if (canRescue) {
        ResolvedProductPtr pseudoProduct = ResolvedProduct::create();
        foreach (const RescuableArtifactData::ChildData &cd, rad.children) {
            pseudoProduct->name = cd.productName;
            pseudoProduct->profile = cd.productProfile;
            Artifact * const child = lookupArtifact(pseudoProduct, m_project->buildData.data(),
                                                    cd.childFilePath, true);
            if (artifact->children.contains(child))
                continue;
            if (!child)  {
                // If a child has disappeared, we must re-build even if the commands
                // are the same. Example: Header file included in cpp file does not exist anymore.
                canRescue = false;
                if (m_logger.traceEnabled())
                    m_logger.qbsTrace() << "Former child artifact '" << cd.childFilePath
                                        << "' does not exist anymore";
                break;
            }
            // TODO: Shouldn't addedByScanner always be true here? Otherwise the child would be
            //       in the list already, no?
            childrenToConnect << qMakePair(child, cd.addedByScanner);
        }

        if (canRescue) {
            const int newChildCount = childrenToConnect.count()
                    + ArtifactSet::fromNodeSet(artifact->children).count();
            QBS_CHECK(newChildCount >= rad.children.count());
            if (newChildCount > rad.children.count()) {
                canRescue = false;
                if (m_logger.traceEnabled())
                    m_logger.qbsTrace() << "Artifact has children not present in rescue data";
            }
        }
    } else {
        if (m_logger.traceEnabled())
            m_logger.qbsTrace() << "Transformer commands changed.";
    }

    if (canRescue) {
        artifact->setTimestamp(rad.timeStamp);
        if (childrenAdded && !childrenToConnect.isEmpty())
            *childrenAdded = true;
        foreach (const ChildArtifactData &cad, childrenToConnect) {
            safeConnect(artifact, cad.first, m_logger);
            if (cad.second)
                artifact->childrenAddedByScanner << cad.first;
        }
        if (m_logger.traceEnabled())
            m_logger.qbsTrace() << "Data was rescued.";
    } else {
        removeGeneratedArtifactFromDisk(artifact, m_logger);
        m_artifactsRemovedFromDisk << artifact->filePath();
        if (m_logger.traceEnabled())
            m_logger.qbsTrace() << "Data not rescued.";
    }
    product->buildData->rescuableArtifactData.erase(it);
}

bool Executor::checkForUnbuiltDependencies(Artifact *artifact)
{
    bool buildingDependenciesFound = false;
    NodeSet unbuiltDependencies;
    foreach (BuildGraphNode *dependency, artifact->children) {
        switch (dependency->buildState) {
        case BuildGraphNode::Untouched:
        case BuildGraphNode::Buildable:
            if (m_logger.debugEnabled()) {
                m_logger.qbsDebug() << "[EXEC] unbuilt dependency: "
                                    << dependency->toString();
            }
            unbuiltDependencies += dependency;
            break;
        case BuildGraphNode::Building: {
            if (m_logger.debugEnabled()) {
                m_logger.qbsDebug() << "[EXEC] dependency in state 'Building': "
                                    << dependency->toString();
            }
            buildingDependenciesFound = true;
            break;
        }
        case BuildGraphNode::Built:
            // do nothing
            break;
        }
    }
    if (!unbuiltDependencies.isEmpty()) {
        artifact->inputsScanned = false;
        updateLeaves(unbuiltDependencies);
        return true;
    }
    if (buildingDependenciesFound) {
        artifact->inputsScanned = false;
        return true;
    }
    return false;
}

void Executor::potentiallyRunTransformer(const TransformerPtr &transformer)
{
    foreach (Artifact * const output, transformer->outputs) {
        // Rescuing build data can introduce new dependencies, potentially delaying execution of
        // this transformer.
        bool childrenAddedDueToRescue;
        rescueOldBuildData(output, &childrenAddedDueToRescue);
        if (childrenAddedDueToRescue && checkForUnbuiltDependencies(output))
            return;
    }

    if (!transformerHasMatchingOutputTags(transformer)) {
        if (m_doDebug)
            m_logger.qbsDebug() << "[EXEC] file tags do not match. Skipping.";
        finishTransformer(transformer);
        return;
    }

    if (!transformerHasMatchingInputFiles(transformer)) {
        if (m_doDebug)
            m_logger.qbsDebug() << "[EXEC] input files do not match. Skipping.";
        finishTransformer(transformer);
        return;
    }

    if (!mustExecuteTransformer(transformer)) {
        if (m_doDebug)
            m_logger.qbsDebug() << "[EXEC] Up to date. Skipping.";
        finishTransformer(transformer);
        return;
    }

    foreach (Artifact * const output, transformer->outputs) {
        // Scan all input artifacts. If new dependencies were found during scanning, delay
        // execution of this transformer.
        InputArtifactScanner scanner(output, m_inputArtifactScanContext, m_logger);
        scanner.scan();
        if (scanner.newDependencyAdded() && checkForUnbuiltDependencies(output))
            return;
    }

    runTransformer(transformer);
}

void Executor::runTransformer(const TransformerPtr &transformer)
{
    QBS_CHECK(transformer);

    // create the output directories
    if (!m_buildOptions.dryRun()) {
        ArtifactSet::const_iterator it = transformer->outputs.begin();
        for (; it != transformer->outputs.end(); ++it) {
            Artifact *output = *it;
            QDir outDir = QFileInfo(output->filePath()).absoluteDir();
            if (!outDir.exists() && !outDir.mkpath(QLatin1String("."))) {
                    throw ErrorInfo(tr("Failed to create directory '%1'.")
                                    .arg(QDir::toNativeSeparators(outDir.absolutePath())));
            }
        }
    }

    QBS_CHECK(!m_availableJobs.isEmpty());
    ExecutorJob *job = m_availableJobs.takeFirst();
    foreach (Artifact * const artifact, transformer->outputs)
        artifact->buildState = BuildGraphNode::Building;
    m_processingJobs.insert(job, transformer);
    job->run(transformer.data());
}

void Executor::finishTransformer(const TransformerPtr &transformer)
{
    foreach (Artifact * const artifact, transformer->outputs) {
        possiblyInstallArtifact(artifact);
        finishArtifact(artifact);
    }
}

void Executor::possiblyInstallArtifact(const Artifact *artifact)
{
    if (m_buildOptions.install()
            && artifact->properties->qbsPropertyValue(QLatin1String("install")).toBool()) {
            m_productInstaller->copyFile(artifact);
    }
}

void Executor::onJobFinished(const qbs::ErrorInfo &err)
{
    if (err.hasError()) {
        if (m_buildOptions.keepGoing()) {
            ErrorInfo fullWarning(err);
            fullWarning.prepend(Tr::tr("Ignoring the following errors on user request:"));
            m_logger.printWarning(fullWarning);
        } else {
            if (!m_error.hasError())
                m_error = err; // All but the first one could be due to canceling.
        }
    }

    try {
        ExecutorJob * const job = qobject_cast<ExecutorJob *>(sender());
        QBS_CHECK(job);
        finishJob(job, !err.hasError());
    } catch (const ErrorInfo &error) {
        handleError(error);
    }
}

void Executor::finish()
{
    QBS_ASSERT(m_state != ExecutorIdle, /* ignore */);

    QList<ResolvedProductPtr> unbuiltProducts;
    foreach (const ResolvedProductPtr &product, m_productsToBuild) {
        bool productBuilt = true;
        foreach (BuildGraphNode *rootNode, product->buildData->roots) {
            if (rootNode->buildState != BuildGraphNode::Built) {
                productBuilt = false;
                unbuiltProducts += product;
                break;
            }
        }
        if (productBuilt) {
            // Any element still left after a successful build has not been re-created
            // by any rule and therefore does not exist anymore as an artifact.
            foreach (const QString &filePath, product->buildData->rescuableArtifactData.keys()) {
                removeGeneratedArtifactFromDisk(filePath, m_logger);
                m_artifactsRemovedFromDisk << filePath;
            }
            product->buildData->rescuableArtifactData.clear();
        }
    }

    if (unbuiltProducts.isEmpty()) {
        m_logger.qbsInfo() << Tr::tr("Build done%1.").arg(configString());
    } else {
        m_error.append(Tr::tr("The following products could not be built%1:").arg(configString()));
        foreach (const ResolvedProductConstPtr &p, unbuiltProducts) {
            QString errorMessage = Tr::tr("\t%1").arg(p->name);
            if (p->profile != m_project->profile())
                errorMessage += Tr::tr(" (for profile '%1')").arg(p->profile);
            m_error.append(errorMessage);
        }
    }

    if (m_explicitlyCanceled)
        m_error.append(Tr::tr("Build canceled%1.").arg(configString()));
    setState(ExecutorIdle);
    if (m_progressObserver) {
        m_progressObserver->setFinished();
        m_cancelationTimer->stop();
    }

    EmptyDirectoriesRemover(m_project.data(), m_logger)
            .removeEmptyParentDirectories(m_artifactsRemovedFromDisk);

    emit finished();
}

void Executor::checkForCancellation()
{
    QBS_ASSERT(m_progressObserver, return);
    if (m_state == ExecutorRunning && m_progressObserver->canceled()) {
        cancelJobs();
        m_evalContext->engine()->cancel();
    }
}

bool Executor::visit(Artifact *artifact)
{
    QBS_CHECK(artifact->buildState != BuildGraphNode::Untouched);
    QBS_CHECK(artifact->artifactType == Artifact::SourceFile
              || m_productsToBuild.contains(artifact->product));
    buildArtifact(artifact);
    return false;
}

bool Executor::visit(RuleNode *ruleNode)
{
    QBS_CHECK(ruleNode->buildState != BuildGraphNode::Untouched);
    QBS_CHECK(m_productsToBuild.contains(ruleNode->product));
    executeRuleNode(ruleNode);
    return false;
}

/**
  * Sets the state of all artifacts in the graph to "untouched".
  * This must be done before doing a build.
  *
  * Retrieves the timestamps of source artifacts.
  *
  * This function also fills the list of changed source files.
  */
void Executor::prepareAllNodes()
{
    foreach (const ResolvedProductPtr &product, m_productsToBuild) {
        foreach (BuildGraphNode *node, product->buildData->nodes) {
            node->buildState = BuildGraphNode::Untouched;
            Artifact *artifact = dynamic_cast<Artifact *>(node);
            if (artifact)
                prepareArtifact(artifact);
        }
    }
}

void Executor::prepareArtifact(Artifact *artifact)
{
    artifact->inputsScanned = false;
    artifact->timestampRetrieved = false;

    if (artifact->artifactType == Artifact::SourceFile) {
        const FileTime oldTimestamp = artifact->timestamp();
        retrieveSourceFileTimestamp(artifact);
        if (oldTimestamp != artifact->timestamp())
            m_changedSourceArtifacts.append(artifact);
        possiblyInstallArtifact(artifact);
    }

    // Timestamps of file dependencies must be invalid for every build.
    foreach (FileDependency *fileDependency, artifact->fileDependencies)
        fileDependency->clearTimestamp();
}

/**
 * Walk the build graph top-down from the roots and for each reachable node N
 *  - mark N as buildable.
 */
void Executor::prepareReachableNodes()
{
    foreach (BuildGraphNode *root, m_roots)
        prepareReachableNodes_impl(root);
}

void Executor::prepareReachableNodes_impl(BuildGraphNode *node)
{
    if (node->buildState != BuildGraphNode::Untouched)
        return;

    node->buildState = BuildGraphNode::Buildable;
    foreach (BuildGraphNode *child, node->children)
        prepareReachableNodes_impl(child);
}

void Executor::prepareProducts()
{
    ProductPrioritySetter prioritySetter(m_project.data());
    prioritySetter.apply();
    foreach (ResolvedProductPtr product, m_productsToBuild)
        product->setupBuildEnvironment(m_evalContext->engine(), m_project->environment);
}

void Executor::setupRootNodes()
{
    m_roots.clear();
    foreach (const ResolvedProductPtr &product, m_productsToBuild) {
        foreach (BuildGraphNode *root, product->buildData->roots)
            m_roots += root;
    }
}

void Executor::setState(ExecutorState s)
{
    if (m_state == s)
        return;
    m_state = s;
}

} // namespace Internal
} // namespace qbs
