/*
 * Copyright (c) 2017 Cisco and/or its affiliates.
 * 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.
 */

#ifndef __VOM_OBJECT_H__
#define __VOM_OBJECT_H__

#include <memory>
#include <string>

#include "vom/types.hpp"

namespace VOM {
/**
 * A base class for all object_base in the VPP object_base-Model.
 *  provides the abstract interface.
 */
class object_base
{
public:
  /**
   * convert to string format for debug purposes
   */
  virtual std::string to_string() const = 0;

  /**
   * Sweep/reap the object if still stale
   */
  virtual void sweep(void) = 0;

  /**
   * replay the object to create it in hardware
   */
  virtual void replay(void) = 0;

protected:
  /**
   * Constructable by derived classes only
   */
  object_base() = default;
  /**
   * Destructor
   */
  virtual ~object_base() = default;

private:
  /**
   * note we are not maintaining dependencies back to the
   * keys. i.e. this object does not know all the keys that
   * refer to it.
   */
};

/**
 * object state
 */
enum obj_state_t
{
  OBJECT_STATE_NONE = 0,
  /**
   * indicates the object is stale. This flag is set
   * when a new epoch is declared. the flag is cleared
   * when the object is updated in the new epoch. If the
   * flag is still set after convergence is declared then
   * the object is deleted
   */
  OBJECT_STATE_STALE,
};

/**
 * A represenation of a reference to a VPP object.
 *  the reference counting is held through the use of shared pointers.
 * We also maintain the state of the object ready for mark n' sweep.
 */
class object_ref
{
public:
  /**
   * Constructor
   */
  object_ref(std::shared_ptr<object_base> obj);

  /**
   * less than operator
   */
  bool operator<(const object_ref& other) const;

  /**
   * Return the shared pointer
   */
  std::shared_ptr<object_base> obj() const;

  /**
   * Mark the reference object as stale
   */
  void mark() const;

  /**
   * Clear the stale flag on the object
   */
  void clear() const;

  /**
   * Query if the object is stale
   */
  bool stale() const;

private:
  /**
   * The reference object
   */
  std::shared_ptr<object_base> m_obj;

  /**
   * Not part of the key (in the set) so we can change it
   * whilst iterating
   */
  mutable obj_state_t m_state;
};

/**
 * ostream print of a VPP Obect
 */
std::ostream& operator<<(std::ostream& os, const object_base& o);
};

/*
 * fd.io coding-style-patch-verification: ON
 *
 * Local Variables:
 * eval: (c-set-style "mozilla")
 * End:
 */

#endif