/* -*-  Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */

#include "ns3/nstime.h"

#include "ns3/event-id.h"

#include <vector>

namespace ns3 {

class MacParameters;

class DcfState

{

public:

  DcfState ();

  virtual ~DcfState ();

  void SetAifsn (uint32_t aifsn);

  void SetCwBounds (uint32_t minCw, uint32_t maxCw);

  void ResetCw (void);

  void UpdateFailedCw (void);

  void StartBackoffNow (uint32_t nSlots);

  uint32_t GetCw (void) const;

private:

  friend class DcfManager;

  uint32_t GetAifsn (void) const;

  uint32_t GetBackoffSlots (void) const;

  Time GetBackoffStart (void) const;

  void UpdateBackoffSlotsNow (uint32_t nSlots, Time backoffUpdateBound);

  uint32_t m_aifsn;

  uint32_t m_backoffSlots;

  // the backoffStart variable is used to keep track of the

  // time at which a backoff was started or the time at which

  // the backoff counter was last updated.

  Time m_backoffStart;

  uint32_t m_cwMin;

  uint32_t m_cwMax;

  uint32_t m_cw;

};

class DcfManager

{

public:

  DcfManager ();

  void SetSlotTime (Time slotTime);

  void SetSifs (Time sifs);

  // at the lowest mandatory rate.

  // used for EIFS calculation.

  void SetAckTxDuration (Time ackTxDuration);

  void Add (DcfState *dcf);

  void RequestAccess (DcfState *state);

  /**

   * \param duration expected duration of reception

   *

   * Notify the DCF that a packet reception started 

   * for the expected duration.

   */

  void NotifyRxStartNow (Time duration);

  /**

   * Notify the DCF that a packet reception was just

   * completed successfully.

   */

  void NotifyRxEndOkNow (void);

  /**

   * Notify the DCF that a packet reception was just

   * completed unsuccessfully.

   */

  void NotifyRxEndErrorNow (void);

  /**

   * \param duration expected duration of transmission

   *

   * Notify the DCF that a packet transmission was

   * just started and is expected to last for the specified

   * duration.

   */

  void NotifyTxStartNow (Time duration);

  /**

   * \param duration expected duration of cca busy period

   *

   * Notify the DCF that a CCA busy period has just started.

   */

  void NotifyCcaBusyStartNow (Time duration);

  /**

   * \param duration the value of the received NAV.

   *

   * Called at end of rx

   */

  void NotifyNavResetNow (Time duration);

  /**

   * \param duration the value of the received NAV.

   *

   * Called at end of rx

   */

  void NotifyNavStartNow (Time duration);

private:

  void UpdateBackoff (void);

  Time MostRecent (Time a, Time b) const;

  Time MostRecent (Time a, Time b, Time c) const;

  Time MostRecent (Time a, Time b, Time c, Time d) const;

  /**

   * Access will never be granted to the medium _before_

   * the time returned by this method.

   * 

   * \returns the absolute time at which access could start to 

   * be granted

   */

  Time GetAccessGrantStart (void) const;

  Time GetBackoffStartFor (DcfState *state);

  Time GetBackoffEndFor (DcfState *state);

  void DoRestartAccessTimeoutIfNeeded (void);

  void AccessTimeout (void);

  void DoGrantAccess (void);

  bool IsBusy (void) const;

  typedef std::vector<DcfState *> States;

  States m_states;

  Time m_lastNavStart;

  Time m_lastNavDuration;

  Time m_lastRxStart;

  Time m_lastRxDuration;

  bool m_lastRxReceivedOk;

  Time m_lastRxEnd;

  Time m_lastTxStart;

  Time m_lastTxDuration;

  Time m_lastBusyStart;

  Time m_lastBusyDuration;

  bool m_rxing;

  bool m_sleeping;

  Time m_ackTxTime;

  EventId m_accessTimeout;

  Time m_slotTime;

  Time m_sifs;

};

} // namespace ns3