QGCTileCacheWorker.cpp

/****************************************************************************
 *
 *   (c) 2009-2016 QGROUNDCONTROL PROJECT <http://www.qgroundcontrol.org>
 *
 * QGroundControl is licensed according to the terms in the file
 * COPYING.md in the root of the source code directory.
 *
 ****************************************************************************/


/**
 * @file
 *   @brief Map Tile Cache Worker Thread
 *
 *   @author Gus Grubba <mavlink@grubba.com>
 *
 */

#include "QGCMapEngine.h"
#include "QGCMapTileSet.h"

#include <QVariant>
#include <QtSql/QSqlQuery>
#include <QSqlError>
#include <QDebug>
#include <QDateTime>
#include <QApplication>
#include <QFile>

#include "time.h"

const char* kDefaultSet = "Default Tile Set";
const QString kSession  = QLatin1String("QGeoTileWorkerSession");

QGC_LOGGING_CATEGORY(QGCTileCacheLog, "QGCTileCacheLog")

//-- Update intervals

#define LONG_TIMEOUT        5
#define SHORT_TIMEOUT       2

//-----------------------------------------------------------------------------
QGCCacheWorker::QGCCacheWorker()
    : _db(NULL)
    , _valid(false)
    , _failed(false)
    , _defaultSet(UINT64_MAX)
    , _totalSize(0)
    , _totalCount(0)
    , _defaultSize(0)
    , _defaultCount(0)
    , _lastUpdate(0)
    , _updateTimeout(SHORT_TIMEOUT)
{

}

//-----------------------------------------------------------------------------
QGCCacheWorker::~QGCCacheWorker()
{

}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::setDatabaseFile(const QString& path)
{
    _databasePath = path;
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::quit()
{
    _mutex.lock();
    while(_taskQueue.count()) {
        QGCMapTask* task = _taskQueue.dequeue();
        delete task;
    }
    _mutex.unlock();
    if(this->isRunning()) {
        _waitc.wakeAll();
    }
}

//-----------------------------------------------------------------------------
bool
QGCCacheWorker::enqueueTask(QGCMapTask* task)
{
    //-- If not initialized, the only allowed task is Init
    if(!_valid && task->type() != QGCMapTask::taskInit) {
        task->setError("Database Not Initialized");
        task->deleteLater();
        return false;
    }
    if(!_taskQueue.contains(task))
    {
        _mutex.lock();
        _taskQueue.enqueue(task);
        _mutex.unlock();
        if(this->isRunning()) {
            _waitc.wakeAll();
        } else {
            this->start(QThread::NormalPriority);
        }
        return true;
    }
    //-- Should never happen
    return false;
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::run()
{
    if(!_valid && !_failed) {
        _init();
    }
    if(_valid) {
        _db = new QSqlDatabase(QSqlDatabase::addDatabase("QSQLITE", kSession));
        _db->setDatabaseName(_databasePath);
        _db->setConnectOptions("QSQLITE_ENABLE_SHARED_CACHE");
        _valid = _db->open();
    }
    while(true) {
        QGCMapTask* task;
        if(_taskQueue.count()) {
            _mutex.lock();
            task = _taskQueue.dequeue();
            _mutex.unlock();
            switch(task->type()) {
                case QGCMapTask::taskInit:
                    break;
                case QGCMapTask::taskCacheTile:
                    _saveTile(task);
                    break;
                case QGCMapTask::taskFetchTile:
                    _getTile(task);
                    break;
                case QGCMapTask::taskFetchTileSets:
                    _getTileSets(task);
                    break;
                case QGCMapTask::taskCreateTileSet:
                    _createTileSet(task);
                    break;
                case QGCMapTask::taskGetTileDownloadList:
                    _getTileDownloadList(task);
                    break;
                case QGCMapTask::taskUpdateTileDownloadState:
                    _updateTileDownloadState(task);
                    break;
                case QGCMapTask::taskDeleteTileSet:
                    _deleteTileSet(task);
                    break;
                case QGCMapTask::taskPruneCache:
                    _pruneCache(task);
                    break;
                case QGCMapTask::taskReset:
                    _resetCacheDatabase(task);
                    break;
            }
            task->deleteLater();
            //-- Check for update timeout
            size_t count = _taskQueue.count();
            if(count > 100) {
                _updateTimeout = LONG_TIMEOUT;
            } else if(count < 25) {
                _updateTimeout = SHORT_TIMEOUT;
            }
            if(!count || (time(0) - _lastUpdate > _updateTimeout)) {
                if(_valid) {
                    _updateTotals();
                }
            }
        } else {
            //-- Wait a bit before shutting things down
            _waitmutex.lock();
            int timeout = 5000;
            if(!_waitc.wait(&_waitmutex, timeout))
            {
                _waitmutex.unlock();
                _mutex.lock();
                //-- If nothing to do, close db and leave thread
                if(!_taskQueue.count()) {
                    _mutex.unlock();
                    break;
                }
                _mutex.unlock();
            }
            _waitmutex.unlock();
        }
    }
    if(_db) {
        delete _db;
        _db = NULL;
        QSqlDatabase::removeDatabase(kSession);
    }
}
//-----------------------------------------------------------------------------
bool
QGCCacheWorker::_findTileSetID(const QString name, quint64& setID)
{
    QSqlQuery query(*_db);
    QString s = QString("SELECT setID FROM TileSets WHERE name = \"%1\"").arg(name);
    if(query.exec(s)) {
        if(query.next()) {
            setID = query.value(0).toULongLong();
            return true;
        }
    }
    return false;
}

//-----------------------------------------------------------------------------
quint64
QGCCacheWorker::_getDefaultTileSet()
{
    if(_defaultSet != UINT64_MAX)
        return _defaultSet;
    QSqlQuery query(*_db);
    QString s = QString("SELECT setID FROM TileSets WHERE defaultSet = 1");
    if(query.exec(s)) {
        if(query.next()) {
            _defaultSet = query.value(0).toULongLong();
            return _defaultSet;
        }
    }
    return 1L;
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::_saveTile(QGCMapTask *mtask)
{
    if(_valid) {
        QGCSaveTileTask* task = static_cast<QGCSaveTileTask*>(mtask);
        QSqlQuery query(*_db);
        query.prepare("INSERT INTO Tiles(hash, format, tile, size, type, date) VALUES(?, ?, ?, ?, ?, ?)");
        query.addBindValue(task->tile()->hash());
        query.addBindValue(task->tile()->format());
        query.addBindValue(task->tile()->img());
        query.addBindValue(task->tile()->img().size());
        query.addBindValue(task->tile()->type());
        query.addBindValue(QDateTime::currentDateTime().toTime_t());
        if(query.exec()) {
            quint64 tileID = query.lastInsertId().toULongLong();
            quint64 setID = task->tile()->set() == UINT64_MAX ? _getDefaultTileSet() : task->tile()->set();
            QString s = QString("INSERT INTO SetTiles(tileID, setID) VALUES(%1, %2)").arg(tileID).arg(setID);
            query.prepare(s);
            if(!query.exec()) {
                qWarning() << "Map Cache SQL error (add tile into SetTiles):" << query.lastError().text();
            }
            qCDebug(QGCTileCacheLog) << "_saveTile() HASH:" << task->tile()->hash();
        } else {
            //-- Tile was already there.
            //   QtLocation some times requests the same tile twice in a row. The first is saved, the second is already there.
        }
    } else {
        qWarning() << "Map Cache SQL error (saveTile() open db):" << _db->lastError();
    }
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::_getTile(QGCMapTask* mtask)
{
    if(!_valid) {
        mtask->setError("No Cache Database");
        return;
    }
    bool found = false;
    QGCFetchTileTask* task = static_cast<QGCFetchTileTask*>(mtask);
    QSqlQuery query(*_db);
    QString s = QString("SELECT tile, format, type FROM Tiles WHERE hash = \"%1\"").arg(task->hash());
    if(query.exec(s)) {
        if(query.next()) {
            QByteArray ar   = query.value(0).toByteArray();
            QString format  = query.value(1).toString();
            UrlFactory::MapType type = (UrlFactory::MapType)query.value(2).toInt();
            qCDebug(QGCTileCacheLog) << "_getTile() (Found in DB) HASH:" << task->hash();
            QGCCacheTile* tile = new QGCCacheTile(task->hash(), ar, format, type);
            task->setTileFetched(tile);
            found = true;
        }
    }
    if(!found) {
        qCDebug(QGCTileCacheLog) << "_getTile() (NOT in DB) HASH:" << task->hash();
        task->setError("Tile not in cache database");
    }
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::_getTileSets(QGCMapTask* mtask)
{
    if(!_valid) {
        mtask->setError("No Cache Database");
        return;
    }
    QGCFetchTileSetTask* task = static_cast<QGCFetchTileSetTask*>(mtask);
    QSqlQuery query(*_db);
    QString s = QString("SELECT * FROM TileSets ORDER BY defaultSet DESC, name ASC");
    qCDebug(QGCTileCacheLog) << "_getTileSets(): " << s;
    if(query.exec(s)) {
        while(query.next()) {
            QString name = query.value("name").toString();
            QGCCachedTileSet* set = new QGCCachedTileSet(name);
            set->setId(query.value("setID").toULongLong());
            set->setMapTypeStr(query.value("typeStr").toString());
            set->setTopleftLat(query.value("topleftLat").toDouble());
            set->setTopleftLon(query.value("topleftLon").toDouble());
            set->setBottomRightLat(query.value("bottomRightLat").toDouble());
            set->setBottomRightLon(query.value("bottomRightLon").toDouble());
            set->setMinZoom(query.value("minZoom").toInt());
            set->setMaxZoom(query.value("maxZoom").toInt());
            set->setType((UrlFactory::MapType)query.value("type").toInt());
            set->setTotalTileCount(query.value("numTiles").toUInt());
            set->setDefaultSet(query.value("defaultSet").toInt() != 0);
            set->setCreationDate(QDateTime::fromTime_t(query.value("date").toUInt()));
            _updateSetTotals(set);
            //-- Object created here must be moved to app thread to be used there
            set->moveToThread(QApplication::instance()->thread());
            task->tileSetFetched(set);
        }
    } else {
        task->setError("No tile set in database");
    }
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::_updateSetTotals(QGCCachedTileSet* set)
{
    if(set->defaultSet()) {
        _updateTotals();
        set->setSavedTileCount(_totalCount);
        set->setSavedTileSize(_totalSize);
        set->setTotalTileCount(_defaultCount);
        set->setTotalTileSize(_defaultSize);
        return;
    }
    QSqlQuery subquery(*_db);
    QString sq = QString("SELECT COUNT(size), SUM(size) FROM Tiles A INNER JOIN SetTiles B on A.tileID = B.tileID WHERE B.setID = %1").arg(set->id());
    qCDebug(QGCTileCacheLog) << "_updateSetTotals(): " << sq;
    if(subquery.exec(sq)) {
        if(subquery.next()) {
            set->setSavedTileCount(subquery.value(0).toUInt());
            set->setSavedTileSize(subquery.value(1).toULongLong());
            qCDebug(QGCTileCacheLog) << "Set" << set->id() << "Totals:" << set->savedTileCount() << " " << set->savedTileSize() << "Expected: " << set->totalTileCount() << " " << set->totalTilesSize();
            //-- Update (estimated) size
            quint64 avg = UrlFactory::averageSizeForType(set->type());
            if(set->totalTileCount() <= set->savedTileCount()) {
                //-- We're done so the saved size is the total size
                set->setTotalTileSize(set->savedTileSize());
            } else {
                //-- Otherwise we need to estimate it.
                if(set->savedTileCount() > 10 && set->savedTileSize()) {
                    avg = set->savedTileSize() / set->savedTileCount();
                }
                set->setTotalTileSize(avg * set->totalTileCount());
            }
            //-- Now figure out the count for tiles unique to this set
            quint32 ucount = 0;
            quint64 usize  = 0;
            sq = QString("SELECT COUNT(size), SUM(size) FROM Tiles WHERE tileID IN (SELECT A.tileID FROM SetTiles A join SetTiles B on A.tileID = B.tileID WHERE B.setID = %1 GROUP by A.tileID HAVING COUNT(A.tileID) = 1)").arg(set->id());
            if(subquery.exec(sq)) {
                if(subquery.next()) {
                    //-- This is only accurate when all tiles are downloaded
                    ucount = subquery.value(0).toUInt();
                    usize  = subquery.value(1).toULongLong();
                }
            }
            //-- If we haven't downloaded it all, estimate size of unique tiles
            quint32 expectedUcount = set->totalTileCount() - set->savedTileCount();
            if(!ucount) {
                usize = expectedUcount * avg;
            } else {
                expectedUcount = ucount;
            }
            set->setUniqueTileCount(expectedUcount);
            set->setUniqueTileSize(usize);
        }
    }
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::_updateTotals()
{
    QSqlQuery query(*_db);
    QString s;
    s = QString("SELECT COUNT(size), SUM(size) FROM Tiles");
    qCDebug(QGCTileCacheLog) << "_updateTotals(): " << s;
    if(query.exec(s)) {
        if(query.next()) {
            _totalCount = query.value(0).toUInt();
            _totalSize  = query.value(1).toULongLong();
        }
    }
    s = QString("SELECT COUNT(size), SUM(size) FROM Tiles WHERE tileID IN (SELECT A.tileID FROM SetTiles A join SetTiles B on A.tileID = B.tileID WHERE B.setID = %1 GROUP by A.tileID HAVING COUNT(A.tileID) = 1)").arg(_getDefaultTileSet());
    qCDebug(QGCTileCacheLog) << "_updateTotals(): " << s;
    if(query.exec(s)) {
        if(query.next()) {
            _defaultCount = query.value(0).toUInt();
            _defaultSize  = query.value(1).toULongLong();
        }
    }
    emit updateTotals(_totalCount, _totalSize, _defaultCount, _defaultSize);
    _lastUpdate = time(0);
}

//-----------------------------------------------------------------------------
quint64 QGCCacheWorker::_findTile(const QString hash)
{
    quint64 tileID = 0;
    QSqlQuery query(*_db);
    QString s = QString("SELECT tileID FROM Tiles WHERE hash = \"%1\"").arg(hash);
    if(query.exec(s)) {
        if(query.next()) {
            tileID = query.value(0).toULongLong();
        }
    }
    return tileID;
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::_createTileSet(QGCMapTask *mtask)
{
    if(_valid) {
        //-- Create Tile Set
        quint32 actual_count = 0;
        QGCCreateTileSetTask* task = static_cast<QGCCreateTileSetTask*>(mtask);
        QSqlQuery query(*_db);
        query.prepare("INSERT INTO TileSets("
            "name, typeStr, topleftLat, topleftLon, bottomRightLat, bottomRightLon, minZoom, maxZoom, type, numTiles, date"
            ") VALUES(?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)");
        query.addBindValue(task->tileSet()->name());
        query.addBindValue(task->tileSet()->mapTypeStr());
        query.addBindValue(task->tileSet()->topleftLat());
        query.addBindValue(task->tileSet()->topleftLon());
        query.addBindValue(task->tileSet()->bottomRightLat());
        query.addBindValue(task->tileSet()->bottomRightLon());
        query.addBindValue(task->tileSet()->minZoom());
        query.addBindValue(task->tileSet()->maxZoom());
        query.addBindValue(task->tileSet()->type());
        query.addBindValue(task->tileSet()->totalTileCount());
        query.addBindValue(QDateTime::currentDateTime().toTime_t());
        if(!query.exec()) {
            qWarning() << "Map Cache SQL error (add tileSet into TileSets):" << query.lastError().text();
        } else {
            //-- Get just created (auto-incremented) setID
            quint64 setID = query.lastInsertId().toULongLong();
            task->tileSet()->setId(setID);
            //-- Prepare Download List
            quint64 tileCount = 0;
            for(int z = task->tileSet()->minZoom(); z <= task->tileSet()->maxZoom(); z++) {
                QGCTileSet set = QGCMapEngine::getTileCount(z,
                    task->tileSet()->topleftLon(), task->tileSet()->topleftLat(),
                    task->tileSet()->bottomRightLon(), task->tileSet()->bottomRightLat(), task->tileSet()->type());
                tileCount += set.tileCount;
                UrlFactory::MapType type = task->tileSet()->type();
                for(int x = set.tileX0; x <= set.tileX1; x++) {
                    for(int y = set.tileY0; y <= set.tileY1; y++) {
                        //-- See if tile is already downloaded
                        QString hash = QGCMapEngine::getTileHash(type, x, y, z);
                        quint64 tileID = _findTile(hash);
                        if(!tileID) {
                            //-- Set to download
                            query.prepare("INSERT OR IGNORE INTO TilesDownload(setID, hash, type, x, y, z, state) VALUES(?, ?, ?, ?, ? ,? ,?)");
                            query.addBindValue(setID);
                            query.addBindValue(hash);
                            query.addBindValue(type);
                            query.addBindValue(x);
                            query.addBindValue(y);
                            query.addBindValue(z);
                            query.addBindValue(0);
                            if(!query.exec()) {
                                qWarning() << "Map Cache SQL error (add tile into TilesDownload):" << query.lastError().text();
                                mtask->setError("Error creating tile set download list");
                                return;
                            } else
                                actual_count++;
                        } else {
                            //-- Tile already in the database. No need to dowload.
                            QString s = QString("INSERT OR IGNORE INTO SetTiles(tileID, setID) VALUES(%1, %2)").arg(tileID).arg(setID);
                            query.prepare(s);
                            if(!query.exec()) {
                                qWarning() << "Map Cache SQL error (add tile into SetTiles):" << query.lastError().text();
                            }
                            qCDebug(QGCTileCacheLog) << "_createTileSet() Already Cached HASH:" << hash;
                        }
                    }
                }
            }
            //-- Done
            _updateSetTotals(task->tileSet());
            task->setTileSetSaved();
            return;
        }
    }
    mtask->setError("Error saving tile set");
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::_getTileDownloadList(QGCMapTask* mtask)
{
    if(!_valid) {
        mtask->setError("No Cache Database");
        return;
    }
    QList<QGCTile*> tiles;
    QGCGetTileDownloadListTask* task = static_cast<QGCGetTileDownloadListTask*>(mtask);
    QSqlQuery query(*_db);
    QString s = QString("SELECT hash, type, x, y, z FROM TilesDownload WHERE setID = %1 AND state = 0 LIMIT %2").arg(task->setID()).arg(task->count());
    if(query.exec(s)) {
        while(query.next()) {
            QGCTile* tile = new QGCTile;
            tile->setHash(query.value("hash").toString());
            tile->setType((UrlFactory::MapType)query.value("type").toInt());
            tile->setX(query.value("x").toInt());
            tile->setY(query.value("y").toInt());
            tile->setZ(query.value("z").toInt());
            tiles.append(tile);
        }
        for(int i = 0; i < tiles.size(); i++) {
            s = QString("UPDATE TilesDownload SET state = %1 WHERE setID = %2 and hash = \"%3\"").arg((int)QGCTile::StateDownloading).arg(task->setID()).arg(tiles[i]->hash());
            if(!query.exec(s)) {
                qWarning() << "Map Cache SQL error (set TilesDownload state):" << query.lastError().text();
            }
        }
    }
    task->setTileListFetched(tiles);
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::_updateTileDownloadState(QGCMapTask* mtask)
{
    if(!_valid) {
        mtask->setError("No Cache Database");
        return;
    }
    QGCUpdateTileDownloadStateTask* task = static_cast<QGCUpdateTileDownloadStateTask*>(mtask);
    QSqlQuery query(*_db);
    QString s;
    if(task->state() == QGCTile::StateComplete) {
        s = QString("DELETE FROM TilesDownload WHERE setID = %1 AND hash = \"%2\"").arg(task->setID()).arg(task->hash());
    } else {
        if(task->hash() == "*") {
            s = QString("UPDATE TilesDownload SET state = %1 WHERE setID = %2").arg((int)task->state()).arg(task->setID());
        } else {
            s = QString("UPDATE TilesDownload SET state = %1 WHERE setID = %2 AND hash = \"%3\"").arg((int)task->state()).arg(task->setID()).arg(task->hash());
        }
    }
    if(!query.exec(s)) {
        qWarning() << "QGCCacheWorker::_updateTileDownloadState() Error:" << query.lastError().text();
    }
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::_pruneCache(QGCMapTask* mtask)
{
    if(!_valid) {
        mtask->setError("No Cache Database");
        return;
    }
    QGCPruneCacheTask* task = static_cast<QGCPruneCacheTask*>(mtask);
    QSqlQuery query(*_db);
    QString s;
    //-- Select tiles in default set only, sorted by oldest.
    s = QString("SELECT tileID, size, hash FROM Tiles WHERE tileID IN (SELECT A.tileID FROM SetTiles A join SetTiles B on A.tileID = B.tileID WHERE B.setID = %1 GROUP by A.tileID HAVING COUNT(A.tileID) = 1) ORDER BY DATE ASC LIMIT 128").arg(_getDefaultTileSet());
    qint64 amount = (qint64)task->amount();
    QList<quint64> tlist;
    if(query.exec(s)) {
        while(query.next() && amount >= 0) {
            tlist << query.value(0).toULongLong();
            amount -= query.value(1).toULongLong();
            qCDebug(QGCTileCacheLog) << "_pruneCache() HASH:" << query.value(2).toString();
        }
        while(tlist.count()) {
            s = QString("DELETE FROM Tiles WHERE tileID = %1").arg(tlist[0]);
            tlist.removeFirst();
            if(!query.exec(s))
                break;
        }
        task->setPruned();
    }
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::_deleteTileSet(QGCMapTask* mtask)
{
    if(!_valid) {
        mtask->setError("No Cache Database");
        return;
    }
    QGCDeleteTileSetTask* task = static_cast<QGCDeleteTileSetTask*>(mtask);
    QSqlQuery query(*_db);
    QString s;
    //-- Only delete tiles unique to this set
    s = QString("DELETE FROM Tiles WHERE tileID IN (SELECT A.tileID FROM SetTiles A JOIN SetTiles B ON A.tileID = B.tileID WHERE B.setID = %1 GROUP BY A.tileID HAVING COUNT(A.tileID) = 1)").arg(task->setID());
    query.exec(s);
    s = QString("DELETE FROM TilesDownload WHERE setID = %1").arg(task->setID());
    query.exec(s);
    s = QString("DELETE FROM TileSets WHERE setID = %1").arg(task->setID());
    query.exec(s);
    s = QString("DELETE FROM SetTiles WHERE setID = %1").arg(task->setID());
    query.exec(s);
    _updateTotals();
    task->setTileSetDeleted();
}
//-----------------------------------------------------------------------------
void
QGCCacheWorker::_resetCacheDatabase(QGCMapTask* mtask)
{
    if(!_valid) {
        mtask->setError("No Cache Database");
        return;
    }
    QGCResetTask* task = static_cast<QGCResetTask*>(mtask);
    QSqlQuery query(*_db);
    QString s;
    s = QString("DROP TABLE Tiles");
    query.exec(s);
    s = QString("DROP TABLE TileSets");
    query.exec(s);
    s = QString("DROP TABLE SetTiles");
    query.exec(s);
    s = QString("DROP TABLE TilesDownload");
    query.exec(s);
    _createDB();
    task->setResetCompleted();
}

//-----------------------------------------------------------------------------
bool
QGCCacheWorker::_init()
{
    _failed = false;
    if(!_databasePath.isEmpty()) {
        qCDebug(QGCTileCacheLog) << "Mapping cache directory:" << _databasePath;
        //-- Initialize Database
        _db = new QSqlDatabase(QSqlDatabase::addDatabase("QSQLITE", kSession));
        _db->setDatabaseName(_databasePath);
        _db->setConnectOptions("QSQLITE_ENABLE_SHARED_CACHE");
        if (_db->open()) {
            _createDB();
        } else {
            qCritical() << "Map Cache SQL error (init() open db):" << _db->lastError();
            _failed = true;
        }
        delete _db;
        _db = NULL;
        QSqlDatabase::removeDatabase(kSession);
    } else {
        qCritical() << "Could not find suitable cache directory.";
        _failed = true;
    }
    return _failed;
}

//-----------------------------------------------------------------------------
void
QGCCacheWorker::_createDB()
{
    QSqlQuery query(*_db);
    if(!query.exec(
        "CREATE TABLE IF NOT EXISTS Tiles ("
        "tileID INTEGER PRIMARY KEY NOT NULL, "
        "hash TEXT NOT NULL UNIQUE, "
        "format TEXT NOT NULL, "
        "tile BLOB NULL, "
        "size INTEGER, "
        "type INTEGER, "
        "date INTEGER DEFAULT 0)"))
    {
        qWarning() << "Map Cache SQL error (create Tiles db):" << query.lastError().text();
    } else {
        if(!query.exec(
            "CREATE TABLE IF NOT EXISTS TileSets ("
            "setID INTEGER PRIMARY KEY NOT NULL, "
            "name TEXT NOT NULL UNIQUE, "
            "typeStr TEXT, "
            "topleftLat REAL DEFAULT 0.0, "
            "topleftLon REAL DEFAULT 0.0, "
            "bottomRightLat REAL DEFAULT 0.0, "
            "bottomRightLon REAL DEFAULT 0.0, "
            "minZoom INTEGER DEFAULT 3, "
            "maxZoom INTEGER DEFAULT 3, "
            "type INTEGER DEFAULT -1, "
            "numTiles INTEGER DEFAULT 0, "
            "defaultSet INTEGER DEFAULT 0, "
            "date INTEGER DEFAULT 0)"))
        {
            qWarning() << "Map Cache SQL error (create TileSets db):" << query.lastError().text();
        } else {
            if(!query.exec(
                "CREATE TABLE IF NOT EXISTS SetTiles ("
                "setID INTEGER, "
                "tileID INTEGER)"))
            {
                qWarning() << "Map Cache SQL error (create SetTiles db):" << query.lastError().text();
            } else {
                if(!query.exec(
                    "CREATE TABLE IF NOT EXISTS TilesDownload ("
                    "setID INTEGER, "
                    "hash TEXT NOT NULL UNIQUE, "
                    "type INTEGER, "
                    "x INTEGER, "
                    "y INTEGER, "
                    "z INTEGER, "
                    "state INTEGER DEFAULT 0)"))
                {
                    qWarning() << "Map Cache SQL error (create TilesDownload db):" << query.lastError().text();
                } else {
                    //-- Database it ready for use
                    _valid = true;
                }
            }
        }
    }
    //-- Create default tile set
    if(_valid) {
        QString s = QString("SELECT name FROM TileSets WHERE name = \"%1\"").arg(kDefaultSet);
        if(query.exec(s)) {
            if(!query.next()) {
                query.prepare("INSERT INTO TileSets(name, defaultSet, date) VALUES(?, ?, ?)");
                query.addBindValue(kDefaultSet);
                query.addBindValue(1);
                query.addBindValue(QDateTime::currentDateTime().toTime_t());
                if(!query.exec()) {
                    qWarning() << "Map Cache SQL error (Creating default tile set):" << _db->lastError();
                    _valid = false;
                }
            }
        } else {
            qWarning() << "Map Cache SQL error (Looking for default tile set):" << _db->lastError();
        }
    }
    if(!_valid) {
        QFile file(_databasePath);
        file.remove();
    }
    _failed = !_valid;
}