/* -*- 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.
 */

#include "fetch-manager.hpp"
#include <boost/lexical_cast.hpp>
#include <boost/make_shared.hpp>
#include <boost/ref.hpp>
#include <boost/throw_exception.hpp>

#include "logging.hpp"
#include "simple-interval-generator.hpp"

_LOG_INIT(FetchManager);

using namespace boost;
using namespace std;
using namespace Ndnx;

//The disposer object function
struct fetcher_disposer
{
  void
  operator()(Fetcher* delete_this)
  {
    delete delete_this;
  }
};

static const string SCHEDULE_FETCHES_TAG = "ScheduleFetches";

FetchManager::FetchManager(Ccnx::CcnxWrapperPtr ccnx,
                           const Mapping& mapping,
                           const Name& broadcastForwardingHint,
                           uint32_t parallelFetches, // = 3
                           const SegmentCallback& defaultSegmentCallback,
                           const FinishCallback& defaultFinishCallback,
                           const FetchTaskDbPtr& taskDb)
  : m_ccnx(ccnx)
  , m_mapping(mapping)
  , m_maxParallelFetches(parallelFetches)
  , m_currentParallelFetches(0)
  , m_scheduler(new Scheduler)
  , m_executor(new Executor(1))
  , m_defaultSegmentCallback(defaultSegmentCallback)
  , m_defaultFinishCallback(defaultFinishCallback)
  , m_taskDb(taskDb)
  , m_broadcastHint(broadcastForwardingHint)
{
  m_scheduler->start();
  m_executor->start();

  m_scheduleFetchesTask =
    Scheduler::schedulePeriodicTask(m_scheduler,
                                    make_shared<SimpleIntervalGenerator>(
                                      300), // no need to check to often. if needed, will be rescheduled
                                    bind(&FetchManager::ScheduleFetches, this),
                                    SCHEDULE_FETCHES_TAG);
  // resume un-finished fetches if there is any
  if (m_taskDb) {
    m_taskDb->foreachTask(bind(&FetchManager::Enqueue, this, _1, _2, _3, _4, _5));
  }
}

FetchManager::~FetchManager()
{
  m_scheduler->shutdown();
  m_executor->shutdown();

  m_ccnx.reset();

  m_fetchList.clear_and_dispose(fetcher_disposer());
}

// Enqueue using default callbacks
void
FetchManager::Enqueue(const Ccnx::Name& deviceName, const Ccnx::Name& baseName, uint64_t minSeqNo,
                      uint64_t maxSeqNo, int priority)
{
  Enqueue(deviceName, baseName, m_defaultSegmentCallback, m_defaultFinishCallback, minSeqNo,
          maxSeqNo, priority);
}

void
FetchManager::Enqueue(const Ccnx::Name& deviceName, const Ccnx::Name& baseName,
                      const SegmentCallback& segmentCallback, const FinishCallback& finishCallback,
                      uint64_t minSeqNo, uint64_t maxSeqNo, int priority /*PRIORITY_NORMAL*/)
{
  // Assumption for the following code is minSeqNo <= maxSeqNo
  if (minSeqNo > maxSeqNo) {
    return;
  }

  // we may need to guarantee that LookupLocator will gives an answer and not throw exception...
  Name forwardingHint;
  forwardingHint = m_mapping(deviceName);

  if (m_taskDb) {
    m_taskDb->addTask(deviceName, baseName, minSeqNo, maxSeqNo, priority);
  }

  unique_lock<mutex> lock(m_parellelFetchMutex);

  _LOG_TRACE("++++ Create fetcher: " << baseName);
  Fetcher* fetcher =
    new Fetcher(m_ccnx, m_executor, segmentCallback, finishCallback,
                bind(&FetchManager::DidFetchComplete, this, _1, _2, _3),
                bind(&FetchManager::DidNoDataTimeout, this, _1), deviceName, baseName, minSeqNo,
                maxSeqNo, boost::posix_time::seconds(30), forwardingHint);

  switch (priority) {
    case PRIORITY_HIGH:
      _LOG_TRACE("++++ Push front fetcher: " << fetcher->GetName());
      m_fetchList.push_front(*fetcher);
      break;

    case PRIORITY_NORMAL:
    default:
      _LOG_TRACE("++++ Push back fetcher: " << fetcher->GetName());
      m_fetchList.push_back(*fetcher);
      break;
  }

  _LOG_DEBUG("++++ Reschedule fetcher task");
  m_scheduler->rescheduleTaskAt(m_scheduleFetchesTask, 0);
  // ScheduleFetches (); // will start a fetch if m_currentParallelFetches is less than max, otherwise does nothing
}

void
FetchManager::ScheduleFetches()
{
  unique_lock<mutex> lock(m_parellelFetchMutex);

  boost::posix_time::ptime currentTime =
    date_time::second_clock<boost::posix_time::ptime>::universal_time();
  boost::posix_time::ptime nextSheduleCheck =
    currentTime + posix_time::seconds(300); // no reason to have anything, but just in case

  for (FetchList::iterator item = m_fetchList.begin();
       m_currentParallelFetches < m_maxParallelFetches && item != m_fetchList.end();
       item++) {
    if (item->IsActive()) {
      _LOG_DEBUG("Item is active");
      continue;
    }

    if (item->IsTimedWait()) {
      _LOG_DEBUG("Item is in timed-wait");
      continue;
    }

    if (currentTime < item->GetNextScheduledRetry()) {
      if (item->GetNextScheduledRetry() < nextSheduleCheck)
        nextSheduleCheck = item->GetNextScheduledRetry();

      _LOG_DEBUG("Item is delayed");
      continue;
    }

    _LOG_DEBUG("Start fetching of " << item->GetName());

    m_currentParallelFetches++;
    _LOG_TRACE("++++ RESTART PIPELINE: " << item->GetName());
    item->RestartPipeline();
  }

  m_scheduler->rescheduleTaskAt(m_scheduleFetchesTask,
                                (nextSheduleCheck - currentTime).total_seconds());
}

void
FetchManager::DidNoDataTimeout(Fetcher& fetcher)
{
  _LOG_DEBUG("No data timeout for " << fetcher.GetName() << " with forwarding hint: "
                                    << fetcher.GetForwardingHint());

  {
    unique_lock<mutex> lock(m_parellelFetchMutex);
    m_currentParallelFetches--;
    // no need to do anything with the m_fetchList
  }

  if (fetcher.GetForwardingHint().size() == 0) {
    // will be tried initially and again after empty forwarding hint

    /// @todo Handle potential exception
    Name forwardingHint;
    forwardingHint = m_mapping(fetcher.GetDeviceName());

    if (forwardingHint.size() == 0) {
      // make sure that we will try broadcast forwarding hint eventually
      fetcher.SetForwardingHint(m_broadcastHint);
    }
    else {
      fetcher.SetForwardingHint(forwardingHint);
    }
  }
  else if (fetcher.GetForwardingHint() == m_broadcastHint) {
    // will be tried after broadcast forwarding hint
    fetcher.SetForwardingHint(Name("/"));
  }
  else {
    // will be tried after normal forwarding hint
    fetcher.SetForwardingHint(m_broadcastHint);
  }

  double delay = fetcher.GetRetryPause();
  if (delay < 1) // first time
  {
    delay = 1;
  }
  else {
    delay = std::min(2 * delay, 300.0); // 5 minutes max
  }

  fetcher.SetRetryPause(delay);
  fetcher.SetNextScheduledRetry(date_time::second_clock<boost::posix_time::ptime>::universal_time() +
                                posix_time::seconds(delay));

  m_scheduler->rescheduleTaskAt(m_scheduleFetchesTask, 0);
}

void
FetchManager::DidFetchComplete(Fetcher& fetcher, const Name& deviceName, const Name& baseName)
{
  {
    unique_lock<mutex> lock(m_parellelFetchMutex);
    m_currentParallelFetches--;

    if (m_taskDb) {
      m_taskDb->deleteTask(deviceName, baseName);
    }
  }

  // like TCP timed-wait
  m_scheduler->scheduleOneTimeTask(m_scheduler, 10,
                                   boost::bind(&FetchManager::TimedWait, this, ref(fetcher)),
                                   boost::lexical_cast<string>(baseName));

  m_scheduler->rescheduleTaskAt(m_scheduleFetchesTask, 0);
}

void
FetchManager::TimedWait(Fetcher& fetcher)
{
  unique_lock<mutex> lock(m_parellelFetchMutex);
  _LOG_TRACE("+++++ removing fetcher: " << fetcher.GetName());
  m_fetchList.erase_and_dispose(FetchList::s_iterator_to(fetcher), fetcher_disposer());
}