/*
 * Copyright (C) by Klaas Freitag <freitag@owncloud.com>
 *
 * 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; version 2 of the License.
 *
 * 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.
 */

#include "config.h"

#include <sys/inotify.h>

#include "folder.h"
#include "folderwatcher_linux.h"

#include <cerrno>
#include <QDebug>
#include <QStringList>
#include <QObject>
#include <QVarLengthArray>

namespace OCC {

FolderWatcherPrivate::FolderWatcherPrivate(FolderWatcher *p, const QString& path)
    : QObject(),
      _parent(p),
      _folder(path)
{
    _fd = inotify_init();
    if (_fd != -1) {
        _socket.reset( new QSocketNotifier(_fd, QSocketNotifier::Read) );
        connect(_socket.data(), SIGNAL(activated(int)), SLOT(slotReceivedNotification(int)));
    } else {
        qDebug() << Q_FUNC_INFO << "notify_init() failed: " << strerror(errno);
    }

    QMetaObject::invokeMethod(this, "slotAddFolderRecursive", Q_ARG(QString, path));

}

FolderWatcherPrivate::~FolderWatcherPrivate()
{

}

// attention: result list passed by reference!
bool FolderWatcherPrivate::findFoldersBelow( const QDir& dir, QStringList& fullList )
{
    bool ok = true;
    if( !(dir.exists() && dir.isReadable()) ) {
        qDebug() << "Non existing path coming in: " << dir.absolutePath();
        ok = false;
    } else {
        QStringList nameFilter;
        nameFilter << QLatin1String("*");
        QDir::Filters filter = QDir::Dirs | QDir::NoDotAndDotDot|QDir::NoSymLinks;
        const QStringList pathes = dir.entryList(nameFilter, filter);

        QStringList::const_iterator constIterator;
        for (constIterator = pathes.constBegin(); constIterator != pathes.constEnd();
               ++constIterator) {
            const QString fullPath(dir.path()+QLatin1String("/")+(*constIterator));
            fullList.append(fullPath);
            ok = findFoldersBelow(QDir(fullPath), fullList);
        }
    }

    return ok;
}

void FolderWatcherPrivate::inotifyRegisterPath(const QString& path)
{
    if( !path.isEmpty()) {
        int wd = inotify_add_watch(_fd, path.toUtf8().constData(),
                                   IN_CLOSE_WRITE | IN_ATTRIB | IN_MOVE |
                                   IN_CREATE |IN_DELETE | IN_DELETE_SELF |
                                   IN_MOVE_SELF |IN_UNMOUNT |IN_ONLYDIR);
        if( wd > -1 ) {
            _watches.insert(wd, path);
         }
    }
}

void FolderWatcherPrivate::slotAddFolderRecursive(const QString &path)
{
    int subdirs = 0;
    qDebug() << "(+) Watcher:" << path;

    QDir inPath(path);
    inotifyRegisterPath(inPath.absolutePath());

    const QStringList watchedFolders = _watches.values();

    QStringList allSubfolders;
    if( !findFoldersBelow(QDir(path), allSubfolders)) {
        qDebug() << "Could not traverse all sub folders";
    }
    // qDebug() << "currently watching " << watchedFolders;
    QStringListIterator subfoldersIt(allSubfolders);
    while (subfoldersIt.hasNext()) {
        QString subfolder = subfoldersIt.next();
        // qDebug() << "  (**) subfolder: " << subfolder;
        QDir folder (subfolder);
        if (folder.exists() && !watchedFolders.contains(folder.absolutePath())) {
            subdirs++;
            if( _parent->pathIsIgnored(subfolder) ) {
                qDebug() << "* Not adding" << folder.path();
                continue;
            }
            inotifyRegisterPath(folder.absolutePath());
        } else {
            qDebug() << "    `-> discarded:" << folder.path();
        }
    }

    if (subdirs >0) {
        qDebug() << "    `-> and" << subdirs << "subdirectories";
    }
}

void FolderWatcherPrivate::slotReceivedNotification(int fd)
{
    int len;
    struct inotify_event* event;
    int i;
    int error;
    QVarLengthArray<char, 2048> buffer(2048);

    do {
         len = read(fd, buffer.data(), buffer.size());
         error = errno;
         /**
          * From inotify documentation:
          *
          * The behavior when the buffer given to read(2) is too
          * small to return information about the next event
          * depends on the kernel version: in kernels  before 2.6.21,
          * read(2) returns 0; since kernel 2.6.21, read(2) fails with
          * the error EINVAL.
          */
         if (len < 0 && error == EINVAL)
         {
             // double the buffer size
             buffer.resize(buffer.size() * 2);
             /* and try again ... */
             continue;
         }
     } while (false);

    // reset counter
    i = 0;
    // while there are enough events in the buffer
    while(i + sizeof(struct inotify_event) < static_cast<unsigned int>(len)) {
        // cast an inotify_event
        event = (struct inotify_event*)&buffer[i];
        if (event == NULL) {
            qDebug() << "NULL event";
            i += sizeof(struct inotify_event);
            continue;
        }

        // Fire event for the path that was changed.
        if (event->len > 0 && event->wd > -1) {
            QByteArray fileName(event->name);
            // qDebug() << Q_FUNC_INFO << event->name;
            if (fileName.startsWith(".csync_journal.db") ||
                    fileName.startsWith(".owncloudsync.log")) {
                // qDebug() << "ignore journal";
            } else {
                const QString p = _watches[event->wd] + '/' + fileName;
                //qDebug() << "found a change in " << p;
                _parent->changeDetected(p);
            }
        }

        // increment counter
        i += sizeof(struct inotify_event) + event->len;
    }

}

void FolderWatcherPrivate::addPath(const QString& path)
{
    slotAddFolderRecursive(path);
}

void FolderWatcherPrivate::removePath(const QString& path)
{
    int wid = -1;
    // Remove the inotify watch.
    QHash<int, QString>::const_iterator i = _watches.constBegin();

    while (i != _watches.constEnd()) {
        if( i.value() == path ) {
            wid = i.key();
            break;
        }
        ++i;
    }
    if( wid > -1 )  {
        inotify_rm_watch(_fd, wid);
        _watches.remove(wid);
    }
}

} // ns mirall
