/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/**
 * Copyright (c) 2013-2017, Regents of the University of California.
 *
 * This file is part of ChronoShare, a decentralized file sharing application over NDN.
 *
 * ChronoShare 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 3 of the License, or (at your option) any later version.
 *
 * ChronoShare 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 copies of the GNU General Public License along with
 * ChronoShare, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
 *
 * See AUTHORS.md for complete list of ChronoShare authors and contributors.
 */

#ifndef CHRONOSHARE_FS_WATCHER_FS_WATCHER_HPP
#define CHRONOSHARE_FS_WATCHER_FS_WATCHER_HPP

#include "db-helper.hpp"
#include "core/chronoshare-common.hpp"

#include <QFileSystemWatcher>
#include <sqlite3.h>
#include <vector>

#include <ndn-cxx/util/scheduler-scoped-event-id.hpp>
#include <ndn-cxx/util/scheduler.hpp>

#include <boost/asio/io_service.hpp>
#include <boost/filesystem.hpp>

namespace ndn {
namespace chronoshare {

class FsWatcher : public QObject
{
  Q_OBJECT

public:
  class Error : public DbHelper::Error
  {
  public:
    explicit Error(const std::string& what)
      : DbHelper::Error(what)
    {
    }
  };

  typedef std::function<void(const boost::filesystem::path&)> LocalFile_Change_Callback;

  // constructor
  FsWatcher(boost::asio::io_service& io, QString dirPath, LocalFile_Change_Callback onChange,
            LocalFile_Change_Callback onDelete, QObject* parent = 0);

  // destructor
  ~FsWatcher();

private slots:
  // handle callback from watcher
  void
  DidDirectoryChanged(QString dirPath);

  /**
   * @brief This even will be triggered either by actual file change or via directory change event
   * (i.e., can happen twice in a row, as well as trigger false alarm)
   */
  void
  DidFileChanged(QString filePath);

private:
  // handle callback from the watcher
  // scan directory and notify callback about any file changes
  void
  ScanDirectory_NotifyUpdates_Execute(QString dirPath);

  void
  ScanDirectory_NotifyRemovals_Execute(QString dirPath);

  void
  initFileStateDb();

  bool
  fileExists(const boost::filesystem::path& filename);

  void
  addFile(const boost::filesystem::path& filename);

  void
  deleteFile(const boost::filesystem::path& filename);

  void
  getFilesInDir(const boost::filesystem::path& dir, std::vector<std::string>& files);

  void
  rescheduleEvent(const std::string& eventType, const std::string& dirPath,
                  const time::milliseconds& period, const Scheduler::Event& callback);

private:
  QFileSystemWatcher* m_watcher; // filesystem watcher
  Scheduler m_scheduler;

  QString m_dirPath; // monitored path

  LocalFile_Change_Callback m_onChange;
  LocalFile_Change_Callback m_onDelete;

  sqlite3* m_db;

  std::map<std::string, util::scheduler::ScopedEventId> m_events;
};

} // namespace chronoshare
} // namespace ndn

#endif // CHRONOSHARE_FS_WATCHER_FS_WATCHER_HPP