/***************************************************************************
 *   Copyright (C) 2009 by Peter Penz <peter.penz@gmx.at>                  *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA            *
 ***************************************************************************/

#include "versioncontrolobserver.h"

#include "dolphinmodel.h"
#include "kversioncontrolplugin.h"

#include <kdirlister.h>
#include <klocale.h>

#include <QAbstractProxyModel>
#include <QAbstractItemView>
#include <QMutexLocker>
#include <QTimer>

/**
 * The performance of updating the version state of items depends
 * on the used plugin. To prevent that Dolphin gets blocked by a
 * slow plugin, the updating is delegated to a thread.
 */
class UpdateItemStatesThread : public QThread
{
public:
    UpdateItemStatesThread(QObject* parent, QMutex* pluginMutex);
    void setData(KVersionControlPlugin* plugin,
                 const QList<VersionControlObserver::ItemState>& itemStates);
    QList<VersionControlObserver::ItemState> itemStates() const;
    bool retrievedItems() const;

protected:
    virtual void run();
    
private:
    bool m_retrievedItems;
    KVersionControlPlugin* m_plugin;
    QMutex* m_pluginMutex;
    QList<VersionControlObserver::ItemState> m_itemStates;
};

UpdateItemStatesThread::UpdateItemStatesThread(QObject* parent, QMutex* pluginMutex) :
    QThread(parent),
    m_retrievedItems(false),
    m_pluginMutex(pluginMutex),
    m_itemStates()
{
}

void UpdateItemStatesThread::setData(KVersionControlPlugin* plugin,
                                     const QList<VersionControlObserver::ItemState>& itemStates)
{
    m_plugin = plugin;
    m_itemStates = itemStates;
}

void UpdateItemStatesThread::run()
{
    Q_ASSERT(!m_itemStates.isEmpty());
    Q_ASSERT(m_plugin != 0);

    // The items from m_itemStates may be located in different directory levels. The version
    // plugin requires the root directory for KVersionControlPlugin::beginRetrieval(). Instead
    // of doing an expensive search, we utilize the knowledge of the implementation of
    // VersionControlObserver::addDirectory() to be sure that the last item contains the root.
    const QString directory = m_itemStates.last().item.url().directory(KUrl::AppendTrailingSlash);

    QMutexLocker locker(m_pluginMutex);
    m_retrievedItems = false;
    if (m_plugin->beginRetrieval(directory)) {
        const int count = m_itemStates.count();
        for (int i = 0; i < count; ++i) {
            m_itemStates[i].version = m_plugin->versionState(m_itemStates[i].item);
        }
        m_plugin->endRetrieval();
        m_retrievedItems = true;
    }
}

QList<VersionControlObserver::ItemState> UpdateItemStatesThread::itemStates() const
{
    return m_itemStates;
}

bool UpdateItemStatesThread::retrievedItems() const
{
    return m_retrievedItems;
}

// ------------------------------------------------------------------------------------------------

VersionControlObserver::VersionControlObserver(QAbstractItemView* view) :
    QObject(view),
    m_pendingItemStatesUpdate(false),
    m_versionedDirectory(false),
    m_silentUpdate(false),
    m_view(view),
    m_dirLister(0),
    m_dolphinModel(0),
    m_dirVerificationTimer(0),
    m_pluginMutex(QMutex::Recursive),
    m_plugin(0),
    m_updateItemStatesThread(0)
{
    Q_ASSERT(view != 0);

    QAbstractProxyModel* proxyModel = qobject_cast<QAbstractProxyModel*>(view->model());
    m_dolphinModel = (proxyModel == 0) ?
                     qobject_cast<DolphinModel*>(view->model()) :
                     qobject_cast<DolphinModel*>(proxyModel->sourceModel());
    if (m_dolphinModel != 0) {
        m_dirLister = m_dolphinModel->dirLister();
        connect(m_dirLister, SIGNAL(completed()),
                this, SLOT(delayedDirectoryVerification()));
 
        // The verification timer specifies the timeout until the shown directory
        // is checked whether it is versioned. Per default it is assumed that users
        // don't iterate through versioned directories and a high timeout is used
        // The timeout will be decreased as soon as a versioned directory has been
        // found (see verifyDirectory()).
        m_dirVerificationTimer = new QTimer(this);
        m_dirVerificationTimer->setSingleShot(true);
        m_dirVerificationTimer->setInterval(500);
        connect(m_dirVerificationTimer, SIGNAL(timeout()),
                this, SLOT(verifyDirectory()));
    }
}

VersionControlObserver::~VersionControlObserver()
{
    if (m_updateItemStatesThread != 0) {
        m_updateItemStatesThread->terminate();
        m_updateItemStatesThread->wait();
    }
    delete m_plugin;
    m_plugin = 0;
}

QList<QAction*> VersionControlObserver::contextMenuActions(const KFileItemList& items) const
{
    if (m_dolphinModel->hasVersionData() && (m_plugin != 0)) {
        QMutexLocker locker(&m_pluginMutex);
        return m_plugin->contextMenuActions(items);
    }
    return QList<QAction*>();
}

QList<QAction*> VersionControlObserver::contextMenuActions(const QString& directory) const
{
    if (m_dolphinModel->hasVersionData() && (m_plugin != 0)) {
        QMutexLocker locker(&m_pluginMutex);
        return m_plugin->contextMenuActions(directory);
    }

    return QList<QAction*>();
}

void VersionControlObserver::delayedDirectoryVerification()
{
    m_silentUpdate = false;
    m_dirVerificationTimer->start();
}

void VersionControlObserver::silentDirectoryVerification()
{
    m_silentUpdate = true;
    m_dirVerificationTimer->start();
}

void VersionControlObserver::verifyDirectory()
{
    KUrl versionControlUrl = m_dirLister->url();
    if (!versionControlUrl.isLocalFile()) {
        return;
    }

    if (m_plugin == 0) {
        // TODO: just for testing purposes. A plugin approach will be used later.
        m_plugin = new SubversionPlugin();
        connect(m_plugin, SIGNAL(infoMessage(const QString&)),
                this, SIGNAL(infoMessage(const QString&)));
        connect(m_plugin, SIGNAL(errorMessage(const QString&)),
                this, SIGNAL(errorMessage(const QString&)));
        connect(m_plugin, SIGNAL(operationCompletedMessage(const QString&)),
                this, SIGNAL(operationCompletedMessage(const QString&)));
    }

    versionControlUrl.addPath(m_plugin->fileName());
    const KFileItem item = m_dirLister->findByUrl(versionControlUrl);

    bool foundVersionInfo = !item.isNull();
    if (!foundVersionInfo && m_versionedDirectory) {
        // Version control systems like Git provide the version information
        // file only in the root directory. Check whether the version information file can
        // be found in one of the parent directories.

        // TODO...
    }

    if (foundVersionInfo) {
        if (!m_versionedDirectory) {
            m_versionedDirectory = true;

            // The directory is versioned. Assume that the user will further browse through
            // versioned directories and decrease the verification timer.
            m_dirVerificationTimer->setInterval(100);
            connect(m_dirLister, SIGNAL(refreshItems(const QList<QPair<KFileItem,KFileItem>>&)),
                    this, SLOT(delayedDirectoryVerification()));
            connect(m_dirLister, SIGNAL(newItems(const KFileItemList&)),
                    this, SLOT(delayedDirectoryVerification()));
            connect(m_plugin, SIGNAL(versionStatesChanged()),
                    this, SLOT(silentDirectoryVerification()));
        }
        updateItemStates();
    } else if (m_versionedDirectory) {
        m_versionedDirectory = false;

        // The directory is not versioned. Reset the verification timer to a higher
        // value, so that browsing through non-versioned directories is not slown down
        // by an immediate verification.
        m_dirVerificationTimer->setInterval(500);
        disconnect(m_dirLister, SIGNAL(refreshItems(const QList<QPair<KFileItem,KFileItem>>&)),
                   this, SLOT(delayedDirectoryVerification()));
        disconnect(m_dirLister, SIGNAL(newItems(const KFileItemList&)),
                   this, SLOT(delayedDirectoryVerification()));
        disconnect(m_plugin, SIGNAL(versionStatesChanged()),
                   this, SLOT(silentDirectoryVerification()));
    }
}

void VersionControlObserver::applyUpdatedItemStates()
{
    if (!m_updateItemStatesThread->retrievedItems()) {
        // ignore m_silentUpdate for an error message
        emit errorMessage(i18nc("@info:status", "Update of version information failed."));
        return;
    }

    // QAbstractItemModel::setData() triggers a bottleneck in combination with QListView
    // (a detailed description of the root cause is given in the class KFilePreviewGenerator
    // from kdelibs). To bypass this bottleneck, the signals of the model are temporary blocked.
    // This works as the update of the data does not require a relayout of the views used in Dolphin.
    const bool signalsBlocked = m_dolphinModel->signalsBlocked();
    m_dolphinModel->blockSignals(true);

    const QList<ItemState> itemStates = m_updateItemStatesThread->itemStates();
    foreach (const ItemState& itemState, itemStates) {
        m_dolphinModel->setData(itemState.index,
                                QVariant(static_cast<int>(itemState.version)),
                                Qt::DecorationRole);
    }

    m_dolphinModel->blockSignals(signalsBlocked);
    m_view->viewport()->repaint();

    if (!m_silentUpdate) {
        // Using an empty message results in clearing the previously shown information message and showing
        // the default status bar information. This is useful as the user already gets feedback that the
        // operation has been completed because of the icon emblems.
        emit operationCompletedMessage(QString());
    }
    
    if (m_pendingItemStatesUpdate) {
        m_pendingItemStatesUpdate = false;
        updateItemStates();
    }
}

void VersionControlObserver::updateItemStates()
{
    Q_ASSERT(m_plugin != 0);
    if (m_updateItemStatesThread == 0) {
        m_updateItemStatesThread = new UpdateItemStatesThread(this, &m_pluginMutex);
        connect(m_updateItemStatesThread, SIGNAL(finished()),
                this, SLOT(applyUpdatedItemStates()));
    }
    if (m_updateItemStatesThread->isRunning()) {
        // An update is currently ongoing. Wait until the thread has finished
        // the update (see applyUpdatedItemStates()).
        m_pendingItemStatesUpdate = true;
        return;
    }
    
    QList<ItemState> itemStates;
    addDirectory(QModelIndex(), itemStates);
    if (!itemStates.isEmpty()) {
        if (!m_silentUpdate) {
            emit infoMessage(i18nc("@info:status", "Updating version information..."));
        }
        m_updateItemStatesThread->setData(m_plugin, itemStates);
        m_updateItemStatesThread->start(); // applyUpdatedItemStates() is called when finished
    }
}

void VersionControlObserver::addDirectory(const QModelIndex& parentIndex, QList<ItemState>& itemStates)
{
    const int rowCount = m_dolphinModel->rowCount(parentIndex);
    for (int row = 0; row < rowCount; ++row) {
        const QModelIndex index = m_dolphinModel->index(row, DolphinModel::Version, parentIndex);
        addDirectory(index, itemStates);
        
        ItemState itemState;
        itemState.index = index;
        itemState.item = m_dolphinModel->itemForIndex(index);
        itemState.version = KVersionControlPlugin::UnversionedVersion;

        itemStates.append(itemState);
    }
}

#include "versioncontrolobserver.moc"