////////////////////////////////////////////////////////////////////////////////
/// @brief abstract base class for tasks
///
/// @file
/// Tasks are handled by the scheduler. The scheduler calls the task callback
/// as soon as a specific event occurs.
///
/// DISCLAIMER
///
/// Copyright 2014 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 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 ArangoDB GmbH, Cologne, Germany
///
/// @author Dr. Frank Celler
/// @author Achim Brandt
/// @author Copyright 2014, ArangoDB GmbH, Cologne, Germany
/// @author Copyright 2008-2013, triAGENS GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

#ifndef ARANGODB_SCHEDULER_TASK_H
#define ARANGODB_SCHEDULER_TASK_H 1

#include "Basics/Common.h"
#include "Scheduler/events.h"

struct TRI_json_t;

namespace triagens {
  namespace rest {
    class Scheduler;

////////////////////////////////////////////////////////////////////////////////
/// @brief abstract base class for tasks
////////////////////////////////////////////////////////////////////////////////

    class Task {

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

      friend class TaskManager;
      Task (Task const&) = delete;
      Task& operator= (Task const&) = delete;

      public:

////////////////////////////////////////////////////////////////////////////////
/// @brief constructs a new task
///
/// Note that the constructor has no access to the event loop. The connection
/// is provided in the method setup and any setup with regards to the event
/// loop must be done there. It is not possible to simply delete a tasks. You
/// must use the method destroy to cleanup the task, remove it from the event
/// loop and delete it. The method cleanup itself will not delete task but
/// remove it from the event loop. It is possible to use setup again to reuse
/// the task.
////////////////////////////////////////////////////////////////////////////////

        Task (std::string const& id,
              std::string const& name);

////////////////////////////////////////////////////////////////////////////////
/// @brief constructs a new task
////////////////////////////////////////////////////////////////////////////////

        explicit Task (std::string const& name);

      protected:

////////////////////////////////////////////////////////////////////////////////
/// @brief deletes a task
///
/// The method will only be called from after the task has been cleaned by
/// the method cleanup.
////////////////////////////////////////////////////////////////////////////////

        virtual ~Task ();

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

      public:

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the task name for debugging
////////////////////////////////////////////////////////////////////////////////

        std::string const& name () const {
          return _name;
        }

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the task id
////////////////////////////////////////////////////////////////////////////////

        std::string id () const {
          return _id;
        }

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the internal task identifier
////////////////////////////////////////////////////////////////////////////////

        uint64_t taskId () const {
          return _taskId;
        }

////////////////////////////////////////////////////////////////////////////////
/// @brief get a JSON representation of the task
////////////////////////////////////////////////////////////////////////////////

        struct TRI_json_t* toJson () const;

////////////////////////////////////////////////////////////////////////////////
/// @brief whether or not the task is a user task
////////////////////////////////////////////////////////////////////////////////

        virtual bool isUserDefined () const;

////////////////////////////////////////////////////////////////////////////////
/// @brief allow thread to run on slave event loop
////////////////////////////////////////////////////////////////////////////////

        virtual bool needsMainEventLoop () const;

////////////////////////////////////////////////////////////////////////////////
/// @brief called by scheduler to indicate an event
///
/// The method will only be called from within the scheduler thread, which
/// belongs to the loop parameter.
////////////////////////////////////////////////////////////////////////////////

        virtual bool handleEvent (EventToken token, EventType event) = 0;

// -----------------------------------------------------------------------------
// --SECTION--                                                 protected methods
// -----------------------------------------------------------------------------

      protected:

////////////////////////////////////////////////////////////////////////////////
/// @brief get a task specific description in JSON format
////////////////////////////////////////////////////////////////////////////////

        virtual void getDescription (struct TRI_json_t*) const;

////////////////////////////////////////////////////////////////////////////////
/// @brief called to set up the callback information
///
/// The method will only be called from within the scheduler thread, which
/// belongs to the loop parameter.
////////////////////////////////////////////////////////////////////////////////

        virtual bool setup (Scheduler*, EventLoop) = 0;

////////////////////////////////////////////////////////////////////////////////
/// @brief called to clear the callback information
///
/// The method will only be called from within the scheduler thread, which
/// belongs to the loop parameter.
////////////////////////////////////////////////////////////////////////////////

        virtual void cleanup () = 0;

// -----------------------------------------------------------------------------
// --SECTION--                                               protected variables
// -----------------------------------------------------------------------------

      protected:

////////////////////////////////////////////////////////////////////////////////
/// @brief scheduler
////////////////////////////////////////////////////////////////////////////////

        Scheduler* _scheduler;

////////////////////////////////////////////////////////////////////////////////
/// @brief event loop identifier
////////////////////////////////////////////////////////////////////////////////

        EventLoop _loop;

////////////////////////////////////////////////////////////////////////////////
/// @brief task id
////////////////////////////////////////////////////////////////////////////////

        uint64_t const _taskId;

// -----------------------------------------------------------------------------
// --SECTION--                                                 private variables
// -----------------------------------------------------------------------------

      private:

////////////////////////////////////////////////////////////////////////////////
/// @brief task id
////////////////////////////////////////////////////////////////////////////////

        std::string const _id;

////////////////////////////////////////////////////////////////////////////////
/// @brief task name
////////////////////////////////////////////////////////////////////////////////

        std::string const _name;

    };
  }
}

#endif
// -----------------------------------------------------------------------------
// --SECTION--                                                       END-OF-FILE
// -----------------------------------------------------------------------------

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