////////////////////////////////////////////////////////////////////////////////
/// @brief Write-ahead log garbage collection thread
///
/// @file
///
/// DISCLAIMER
///
/// Copyright 2004-2013 triAGENS GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///     http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is triAGENS GmbH, Cologne, Germany
///
/// @author Jan Steemann
/// @author Copyright 2011-2013, triAGENS GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

#include "CollectorThread.h"
#include "BasicsC/logging.h"
#include "Basics/ConditionLocker.h"
#include "Wal/Logfile.h"
#include "Wal/LogfileManager.h"

using namespace triagens::wal;

// -----------------------------------------------------------------------------
// --SECTION--                                             class CollectorThread
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief wait interval for the collector thread when idle
////////////////////////////////////////////////////////////////////////////////

const uint64_t CollectorThread::Interval = 1000000;

// -----------------------------------------------------------------------------
// --SECTION--                                      constructors and destructors
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief create the collector thread
////////////////////////////////////////////////////////////////////////////////

CollectorThread::CollectorThread (LogfileManager* logfileManager) 
  : Thread("WalCollector"),
    _logfileManager(logfileManager),
    _condition(),
    _stop(0) {
  
  allowAsynchronousCancelation();
}

////////////////////////////////////////////////////////////////////////////////
/// @brief destroy the collector thread
////////////////////////////////////////////////////////////////////////////////

CollectorThread::~CollectorThread () {
}

// -----------------------------------------------------------------------------
// --SECTION--                                                    public methods
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief stops the collector thread
////////////////////////////////////////////////////////////////////////////////

void CollectorThread::stop () {
  if (_stop > 0) {
    return;
  }

  _stop = 1;
  _condition.signal();

  while (_stop != 2) {
    usleep(1000);
  }
}

////////////////////////////////////////////////////////////////////////////////
/// @brief signal the thread that there is something to do
////////////////////////////////////////////////////////////////////////////////

void CollectorThread::signal () {
  CONDITION_LOCKER(guard, _condition);
  guard.signal();
}

// -----------------------------------------------------------------------------
// --SECTION--                                                    Thread methods
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief main loop
////////////////////////////////////////////////////////////////////////////////

void CollectorThread::run () {
  while (_stop == 0) {
    // collect a logfile if any qualifies
    bool worked = this->collectLogfiles();

    // delete a logfile if any qualifies
    worked |= this->removeLogfiles();
    
    CONDITION_LOCKER(guard, _condition);
    if (! worked) {
      // sleep only if there was nothing to do
      guard.wait(Interval);
    }
  }

  _stop = 2;
}

// -----------------------------------------------------------------------------
// --SECTION--                                                   private methods
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief perform collection of a logfile (if any)
////////////////////////////////////////////////////////////////////////////////

bool CollectorThread::collectLogfiles () {
  Logfile* logfile = _logfileManager->getCollectableLogfile();

  if (logfile == nullptr) {
    return false;
  }

  _logfileManager->setCollectionRequested(logfile);

  // TODO: implement the actual logfile collection
      
  LOG_TRACE("collecting logfile %llu", (unsigned long long) logfile->id());

  _logfileManager->setCollectionDone(logfile);
  return true;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief perform removal of a logfile (if any)
////////////////////////////////////////////////////////////////////////////////

bool CollectorThread::removeLogfiles () {
  Logfile* logfile = _logfileManager->getRemovableLogfile();

  if (logfile == nullptr) {
    return false;
  }

  _logfileManager->removeLogfile(logfile, true);
  return true;
}

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