/**************************************************************************
**
** This file is part of Qt Creator
**
** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
**
** Contact:  Qt Software Information (qt-info@nokia.com)
**
** Commercial Usage
**
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** 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 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at qt-sales@nokia.com.
**
**************************************************************************/

#include "settingsdatabase.h"

#include <QtCore/QMap>
#include <QtSql/QSqlDatabase>
#include <QtSql/QSqlQuery>
#include <QDebug>

using namespace Core;
using namespace Core::Internal;

enum { debug_settings = 1 };

namespace Core {
namespace Internal {

typedef QMap<QString, QVariant> SettingsMap;

class SettingsDatabasePrivate
{
public:
    QString effectiveGroup() const
    {
        return m_groups.join(QLatin1String("/"));
    }

    QString effectiveKey(const QString &key) const
    {
        QString g = effectiveGroup();
        if (!g.isEmpty())
            g += QLatin1Char('/');
        g += key;
        return g;
    }

    SettingsMap m_settings;

    QStringList m_groups;
    QStringList m_dirtyKeys;

    QSqlDatabase m_db;
};

} // namespace Internal
} // namespace Core

SettingsDatabase::SettingsDatabase(const QString &path,
                                   const QString &application,
                                   QObject *parent)
    : QObject(parent)
    , d(new SettingsDatabasePrivate)
{
    const QLatin1Char slash('/');

    // TODO: Don't rely on a path, but determine automatically
    QString fileName = path;
    if (!fileName.endsWith(slash))
        fileName += slash;
    fileName += application;
    fileName += QLatin1String(".db");

    d->m_db = QSqlDatabase::addDatabase("QSQLITE", QLatin1String("settings"));
    d->m_db.setDatabaseName(fileName);
    if (!d->m_db.open())
        qWarning() << "Warning: Failed to open settings database!";

    // Create the settings table if it doesn't exist yet
    QSqlQuery query(d->m_db);
    query.prepare(QLatin1String("CREATE TABLE IF NOT EXISTS settings ("
                                "key PRIMARY KEY ON CONFLICT REPLACE, "
                                "value)"));
    if (d->m_db.isOpen() && !query.exec())
        qWarning() << "Warning: Failed to prepare settings database!";

    // Retrieve all available keys (values are retrieved lazily)
    if (query.exec(QLatin1String("SELECT key FROM settings"))) {
        while (query.next()) {
            d->m_settings.insert(query.value(0).toString(), QVariant());
        }
    }
}

SettingsDatabase::~SettingsDatabase()
{
    sync();

    delete d;
    QSqlDatabase::removeDatabase(QLatin1String("settings"));
}

void SettingsDatabase::setValue(const QString &key, const QVariant &value)
{
    const QString effectiveKey = d->effectiveKey(key);

    // Add to cache
    d->m_settings.insert(effectiveKey, value);

    // Instant apply (TODO: Delay writing out settings)
    QSqlQuery query(d->m_db);
    query.prepare(QLatin1String("INSERT INTO settings VALUES (?, ?)"));
    query.addBindValue(effectiveKey);
    query.addBindValue(value);
    query.exec();

    if (debug_settings)
        qDebug() << "Stored:" << effectiveKey << "=" << value;
}

QVariant SettingsDatabase::value(const QString &key, const QVariant &defaultValue) const
{
    const QString effectiveKey = d->effectiveKey(key);
    QVariant value = defaultValue;

    SettingsMap::const_iterator i = d->m_settings.constFind(effectiveKey);
    if (i != d->m_settings.constEnd() && i.value().isValid()) {
        value = i.value();
    } else {
        // Try to read the value from the database
        QSqlQuery query(d->m_db);
        query.prepare(QLatin1String("SELECT value FROM settings WHERE key = ?"));
        query.addBindValue(effectiveKey);
        query.exec();
        if (query.next()) {
            value = query.value(0);

            if (debug_settings)
                qDebug() << "Retrieved:" << effectiveKey << "=" << value;
        }

        // Cache the result
        d->m_settings.insert(effectiveKey, value);
    }

    return value;
}

bool SettingsDatabase::contains(const QString &key) const
{
    return d->m_settings.contains(d->effectiveKey(key));
}

void SettingsDatabase::remove(const QString &key)
{
    Q_UNUSED(key);
    // TODO: Remove key and all subkeys
}

void SettingsDatabase::beginGroup(const QString &prefix)
{
    d->m_groups.append(prefix);
}

void SettingsDatabase::endGroup()
{
    d->m_groups.removeLast();
}

QString SettingsDatabase::group() const
{
    return d->effectiveGroup();
}

QStringList SettingsDatabase::childKeys() const
{
    QStringList childs;

    const QString g = group();
    QMapIterator<QString, QVariant> i(d->m_settings);
    while (i.hasNext()) {
        const QString &key = i.next().key();
        if (key.startsWith(g) && key.indexOf(QLatin1Char('/'), g.length() + 1) == -1) {
            childs.append(key.mid(g.length() + 1));
        }
    }

    return childs;
}

void SettingsDatabase::sync()
{
    // TODO: Delay writing of dirty keys and save them here
}