//------------------------------------------------------------------------------
// Copyright (c) 2013 by European Organization for Nuclear Research (CERN)
// Author: Lukasz Janyst <ljanyst@cern.ch>
//------------------------------------------------------------------------------
// XRootD is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// XRootD 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 Lesser General Public License
// along with XRootD.  If not, see <http://www.gnu.org/licenses/>.
//------------------------------------------------------------------------------

#ifndef __XRD_CL_SYNC_QUEUE_HH__
#define __XRD_CL_SYNC_QUEUE_HH__

#include "FuseException.hh"

#include <queue>

#include <XrdSys/XrdSysPthread.hh>

//----------------------------------------------------------------------------
//! A synchronized queue
//----------------------------------------------------------------------------

template <typename Item>
class SyncQueue
{
public:
  //------------------------------------------------------------------------
  //! Constructor
  //------------------------------------------------------------------------

  SyncQueue()
  {
    if (sem_init(&sem, 0, 0)) {
      throw FuseException(errno);
    }
  };

  //------------------------------------------------------------------------
  //! Destructor
  //------------------------------------------------------------------------

  ~SyncQueue()
  {
    sem_destroy(&sem);

    while (!items.empty()) {
      Item* i = items.front();
      items.pop();
      delete i;
    }
  }

  //------------------------------------------------------------------------
  //! Put the item in the queue
  //------------------------------------------------------------------------

  void Put(Item* item)
  {
    XrdSysMutexHelper scopedLock(mutex);
    items.push(item);

    if (sem_post(&sem)) {
      throw FuseException(errno);
    }
  }

  //------------------------------------------------------------------------
  //! Get the item from the front of the queue
  //------------------------------------------------------------------------

  bool Get(Item*& i, time_t timeout = 5 * 60)
  {
    timespec ts;
    ts.tv_nsec = 0;
    ts.tv_sec = ::time(0) + timeout;

    if (sem_timedwait(&sem, &ts)) {
      if (errno == ETIMEDOUT) {
        return false;
      }

      throw FuseException(errno);
    }

    XrdSysMutexHelper scopedLock(mutex);

    // this is not possible, so when it happens we commit a suicide
    if (items.empty()) {
      throw FuseException(ENOENT);
    }

    i = items.front();
    items.pop();
    return true;
  }

private:

  std::queue<Item*> items;
  mutable XrdSysMutex mutex;
  sem_t sem;
};


#endif // __XRD_CL_ANY_OBJECT_HH__