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**
** Copyright (C) 2015 The Qt Company Ltd.
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** This file is part of Qbs.
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** 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
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****************************************************************************/

#include "buildgraphlocker.h"

#include "error.h"
#include "hostosinfo.h"
#include "processutils.h"
#include "progressobserver.h"
#include "version.h"

#include <logging/translator.h>

#include <QDir>
#include <QDirIterator>
#include <QFileInfo>
#include <QString>

namespace qbs {
namespace Internal {

static bool hasQtBug45497()
{
    return Version::fromString(QLatin1String(qVersion())) < Version(5, 5, 1);
}

static bool hasQtBug53392()
{
    if (!HostOsInfo::isWindowsHost())
        return false;
    const Version qtVersion = Version::fromString(QLatin1String(qVersion()));
    // The fix is included in 5.6.2 and 5.7.1, but not in 5.7.0.
    return qtVersion == Version(5, 7, 0) || qtVersion < Version(5, 6, 2);
}

static void tryCreateBuildDirectory(const QString &buildDir, const QString &buildGraphFilePath)
{
    if (!QDir::root().mkpath(buildDir)) {
        throw ErrorInfo(Tr::tr("Cannot lock build graph file '%1': Failed to create directory.")
                        .arg(buildGraphFilePath));
    }
}

BuildGraphLocker::BuildGraphLocker(const QString &buildGraphFilePath, const Logger &logger,
                                   bool waitIndefinitely, ProgressObserver *observer)
    : m_lockFile(buildGraphFilePath + QLatin1String(".lock"))
    , m_logger(logger)
{
    const QString buildDir = QFileInfo(buildGraphFilePath).absolutePath();
    rememberCreatedDirectories(buildDir);
    if (waitIndefinitely)
        m_logger.qbsDebug() << "Waiting to acquire lock file...";
    m_lockFile.setStaleLockTime(0);
    int attemptsToGetInfo = 0;
    do {
        if (observer->canceled())
            break;
        tryCreateBuildDirectory(buildDir, buildGraphFilePath);
        if (m_lockFile.tryLock(250))
            return;
        switch (m_lockFile.error()) {
        case QLockFile::LockFailedError: {
            if (waitIndefinitely)
                continue;
            qint64 pid;
            QString hostName;
            QString appName;
            if (m_lockFile.getLockInfo(&pid, &hostName, &appName)) {
                if ((!hasQtBug45497() && !hasQtBug53392()) || appName == processNameByPid(pid)) {
                    throw ErrorInfo(Tr::tr("Cannot lock build graph file '%1': "
                                           "Already locked by '%2' (PID %3).")
                                    .arg(buildGraphFilePath, appName).arg(pid));
                }

                // The process id was reused by some other process.
                m_logger.qbsInfo() << Tr::tr("Removing stale lock file.");
                m_lockFile.removeStaleLockFile();
            }
            break;
        }
        case QLockFile::PermissionError:
            throw ErrorInfo(Tr::tr("Cannot lock build graph file '%1': Permission denied.")
                            .arg(buildGraphFilePath));
        case QLockFile::UnknownError:
        case QLockFile::NoError:
            throw ErrorInfo(Tr::tr("Cannot lock build graph file '%1' (reason unknown).")
                            .arg(buildGraphFilePath));
        }
    } while (++attemptsToGetInfo < 10 || waitIndefinitely);

    // This very unlikely case arises if tryLock() repeatedly returns LockFailedError
    // with the subsequent getLockInfo() failing as well.
    throw ErrorInfo(Tr::tr("Cannot lock build graph file '%1' (reason unknown).")
                    .arg(buildGraphFilePath));
}

BuildGraphLocker::~BuildGraphLocker()
{
    m_lockFile.unlock();
    removeEmptyCreatedDirectories();
}

void BuildGraphLocker::rememberCreatedDirectories(const QString &buildDir)
{
    QString parentDir = buildDir;
    while (!QFileInfo::exists(parentDir)) {
        m_createdParentDirs.enqueue(parentDir);
        parentDir = QDir::cleanPath(parentDir + QLatin1String("/.."));
    }
}

void BuildGraphLocker::removeEmptyCreatedDirectories()
{
    QDir root = QDir::root();
    while (!m_createdParentDirs.isEmpty()) {
        const QString parentDir = m_createdParentDirs.dequeue();
        QDirIterator it(parentDir, QDir::AllEntries | QDir::NoDotAndDotDot | QDir::System,
                        QDirIterator::Subdirectories);
        if (it.hasNext())
            break;
        if (!root.rmdir(parentDir)) {
            m_logger.printWarning(ErrorInfo(Tr::tr("Failed to remove empty directory '%1'.")
                                            .arg(parentDir)));
        }
    }
}

} // namespace Internal
} // namespace qbs
