// This file is part of RSS Guard.
//
// Copyright (C) 2011-2016 by Martin Rotter <rotter.martinos@gmail.com>
//
// RSS Guard 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.
//
// RSS Guard 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 RSS Guard. If not, see <http://www.gnu.org/licenses/>.

#include "core/feeddownloader.h"

#include "services/abstract/feed.h"
#include "definitions/definitions.h"

#include <QThread>
#include <QDebug>
#include <QThreadPool>
#include <QMutexLocker>


FeedDownloader::FeedDownloader(QObject *parent)
  : QObject(parent), m_feeds(QList<Feed*>()), m_mutex(new QMutex()), m_threadPool(new QThreadPool(this)),
    m_results(FeedDownloadResults()), m_feedsUpdated(0),
    m_feedsUpdating(0), m_feedsTotalCount(0) {
  qRegisterMetaType<FeedDownloadResults>("FeedDownloadResults");
  m_threadPool->setMaxThreadCount(FEED_DOWNLOADER_MAX_THREADS);
}

FeedDownloader::~FeedDownloader() {
  m_mutex->tryLock();
  m_mutex->unlock();
  delete m_mutex;

  qDebug("Destroying FeedDownloader instance.");
}

bool FeedDownloader::isUpdateRunning() const {
  QMutexLocker locker(m_mutex);

  return !m_feeds.isEmpty() || m_feedsUpdating > 0;
}

void FeedDownloader::updateAvailableFeeds() {
  while (!m_feeds.isEmpty()) {
    connect(m_feeds.first(), &Feed::messagesObtained, this, &FeedDownloader::oneFeedUpdateFinished,
            (Qt::ConnectionType) (Qt::UniqueConnection | Qt::AutoConnection));
    if (m_threadPool->tryStart(m_feeds.first())) {
      m_feeds.removeFirst();
      m_feedsUpdating++;
    }
    else {
      // We want to start update of some feeds but all working threads are occupied.
      break;
    }
  }
}

void FeedDownloader::updateFeeds(const QList<Feed*> &feeds) {
  QMutexLocker locker(m_mutex);

  if (feeds.isEmpty()) {
    qDebug("No feeds to update in worker thread, aborting update.");
    finalizeUpdate();
  }
  else {
    qDebug().nospace() << "Starting feed updates from worker in thread: \'" << QThread::currentThreadId() << "\'.";

    m_feeds = feeds;
    m_results.clear();
    m_feedsUpdated = m_feedsUpdating = 0;

    // Job starts now.
    emit updateStarted();
    updateAvailableFeeds();
  }
}

void FeedDownloader::stopRunningUpdate() {
  //QMutexLocker locker(m_mutex);

  m_threadPool->clear();
  m_feeds.clear();
}

void FeedDownloader::oneFeedUpdateFinished(const QList<Message> &messages) {
  QMutexLocker locker(m_mutex);

  m_feedsUpdated++;
  m_feedsUpdating--;

  Feed *feed = qobject_cast<Feed*>(sender());

  disconnect(feed, &Feed::messagesObtained, this, &FeedDownloader::oneFeedUpdateFinished);

  // Now, we check if there are any feeds we would like to update too.
  updateAvailableFeeds();

  // Now make sure, that messages are actually stored to SQL in a locked state.
  qDebug().nospace() << "Saving messages of feed "
                     << feed->id() << " in thread: \'"
                     << QThread::currentThreadId() << "\'.";

  int updated_messages;

  QMetaObject::invokeMethod(feed, "updateMessages", Qt::BlockingQueuedConnection,
                            Q_RETURN_ARG(int, updated_messages),
                            Q_ARG(QList<Message>, messages));

  if (updated_messages > 0) {
    m_results.appendUpdatedFeed(QPair<QString,int>(feed->title(), updated_messages));
  }

  qDebug("Made progress in feed updates, total feeds count %d/%d (id of feed is %d).", m_feedsUpdated, m_feedsTotalCount, feed->id());
  emit updateProgress(feed, m_feedsUpdated, m_feedsTotalCount);

  if (m_feeds.isEmpty() && m_feedsUpdating <= 0) {
    finalizeUpdate();
  }
}

void FeedDownloader::finalizeUpdate() {
  qDebug().nospace() << "Finished feed updates in thread: \'" << QThread::currentThreadId() << "\'.";

  m_results.sort();

  // Update of feeds has finished.
  // NOTE: This means that now "update lock" can be unlocked
  // and feeds can be added/edited/deleted and application
  // can eventually quit.
  emit updateFinished(m_results);
}

FeedDownloadResults::FeedDownloadResults() : m_updatedFeeds(QList<QPair<QString,int> >()) {
}

QString FeedDownloadResults::overview(int how_many_feeds) const {
  QStringList result;

  for (int i = 0, number_items_output = qMin(how_many_feeds, m_updatedFeeds.size()); i < number_items_output; i++) {
    result.append(m_updatedFeeds.at(i).first + QSL(": ") + QString::number(m_updatedFeeds.at(i).second));
  }

  QString res_str = result.join(QSL("\n"));

  if (m_updatedFeeds.size() > how_many_feeds) {
    res_str += QObject::tr("\n\n+ %n other feeds.", 0, m_updatedFeeds.size() - how_many_feeds);
  }

  return res_str;
}

void FeedDownloadResults::appendUpdatedFeed(const QPair<QString,int> &feed) {
  m_updatedFeeds.append(feed);
}

void FeedDownloadResults::sort() {
  qSort(m_updatedFeeds.begin(), m_updatedFeeds.end(), FeedDownloadResults::lessThan);
}

bool FeedDownloadResults::lessThan(const QPair<QString, int> &lhs, const QPair<QString, int> &rhs) {
  return lhs.second > rhs.second;
}

void FeedDownloadResults::clear() {
  m_updatedFeeds.clear();
}

QList<QPair<QString,int> > FeedDownloadResults::updatedFeeds() const {
  return m_updatedFeeds;
}