/* -*-  Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2010 Network Security Lab, University of Washington, Seattle.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program 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 General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Authors: Sidharth Nabar <snabar@uw.edu>, He Wu <mdzz@u.washington.edu>
 */

#ifndef RV_BATTERY_MODEL_H
#define RV_BATTERY_MODEL_H

#include "ns3/traced-value.h"
#include "ns3/nstime.h"
#include "ns3/event-id.h"
#include "energy-source.h"

namespace ns3 {

/**
 * \brief Rakhmatov Vrudhula non-linear battery model.
 *
 * This (energy source) model implements an analytical non-linear battery model.
 * It is capable of capturing load capacity and recovery effects of batteries.
 * Batteries are characterized by 2 parameters, alpha and beta, which can both
 * be obtained from the discharge curve of the batteries.
 *
 * The model is developed by Daler Rakhmatov & Sarma Vrudhula in: "Battery
 * Lifetime Prediction for Energy-Aware Computing" and "An Analytical High-Level
 * Battery Model for Use in Energy Management of Portable Electronic Systems".
 *
 * The real-time algorithm is developed by Matthias Handy & Dirk Timmermann in:
 * "Simulation of Mobile Wireless Networks with Accurate Modeling of non-linear
 * battery effects". The real-time algorithm is modified by the authors of this
 * code for improved accuracy and reduced computation (sampling) overhead.
 */
class RvBatteryModel : public EnergySource
{
public:
  static TypeId GetTypeId (void);
  RvBatteryModel ();
  virtual ~RvBatteryModel ();

  /**
   * \return Initial energy stored (theoretical capacity) in the battery.
   *
   * Implements GetInitialEnergy.
   */
  virtual double GetInitialEnergy (void) const;

  /**
   * \returns Supply voltage at the energy source.
   *
   * Implements GetSupplyVoltage.
   */
  virtual double GetSupplyVoltage (void) const;

  /**
   * \return Remaining energy in energy source, in Joules
   *
   * Implements GetRemainingEnergy.
   */
  virtual double GetRemainingEnergy (void);

  /**
   * \returns Energy fraction.
   *
   * Implements GetEnergyFraction. For the RV battery model, energy fraction is
   * equivalent to battery level.
   */
  virtual double GetEnergyFraction (void);

  /**
   * Implements UpdateEnergySource. This function samples the total load (total
   * current) from all devices to discharge the battery.
   */
  virtual void UpdateEnergySource (void);

  /**
   * \param interval Energy update interval.
   *
   * This function sets the interval between each energy update.
   */
  void SetSamplingInterval (Time interval);

  /**
   * \returns The interval between each energy update.
   */
  Time GetSamplingInterval (void) const;

  /**
   * \brief Sets open circuit voltage of battery.
   *
   * \param voltage Open circuit voltage.
   */
  void SetOpenCircuitVoltage (double voltage);

  /**
   * \return Open circuit voltage of battery.
   */
  double GetOpenCircuitVoltage (void) const;

  /**
   * \brief Sets cutoff voltage of battery.
   *
   * \param voltage Cutoff voltage.
   */
  void SetCutoffVoltage (double voltage);

  /**
   * \returns Cutoff voltage of battery.
   */
  double GetCutoffVoltage (void) const;

  /**
   * \brief Sets the alpha value for the battery model.
   *
   * \param alpha Alpha.
   */
  void SetAlpha (double alpha);

  /**
   * \returns The alpha value used by the battery model.
   */
  double GetAlpha (void) const;

  /**
   * \brief Sets the beta value for the battery model.
   *
   * \param beta Beta.
   */
  void SetBeta (double beta);

  /**
   * \returns The beta value used by the battery model.
   */
  double GetBeta (void) const;

  /**
   * \returns Battery level [0, 1].
   */
  double GetBatteryLevel (void);

  /**
   * \returns Lifetime of the battery.
   */
  Time GetLifetime (void) const;

  /**
   * \brief Sets the number of terms of the infinite sum for estimating battery
   * level.
   *
   * \param num Number of terms.
   */
  void SetNumOfTerms (int num);

  /**
   * \returns The number of terms of the infinite sum for estimating battery
   * level.
   */
  int GetNumOfTerms (void) const;

private:
  /// Defined in ns3::Object
  virtual void DoStart (void);

  /// Defined in ns3::Object
  virtual void DoDispose (void);

  /**
   * Handles the remaining energy going to zero event. This function notifies
   * all the energy models aggregated to the node about the energy being
   * depleted. Each energy model is then responsible for its own handler.
   */
  void HandleEnergyDrainedEvent (void);

  /**
   * \brief Discharges the battery.
   *
   * \param load Load value (total current form devices, in mA).
   * \param t Time stamp of the load value.
   * \returns Calculated alpha value.
   *
   * Discharge function calculates a value which is then compared to the alpha
   * value to determine if the battery is dead. It will also update the battery
   * level.
   *
   * Note that the load value passed to Discharge has to be in mA.
   */
  double Discharge (double load, Time t);

  /**
   * \brief RV model A function.
   *
   * \param t Current time.
   * \param sk Time stamp in array position k
   * \param sk_1 Time stamp in array position k-1
   * \param beta Beta value used by the battery model.
   * \returns Result of A function.
   *
   * This function computes alpha value using the recorded load profile.
   */
  double RvModelAFunction (Time t, Time sk, Time sk_1, double beta);

private:
  double m_openCircuitVoltage;
  double m_cutoffVoltage;
  double m_alpha; // alpha value of RV model, in Coulomb
  double m_beta;  // beta value of RV model, in second^-1

  double m_previousLoad;  // load value (total current) of previous sampling
  std::vector<double> m_load;     // load profile
  std::vector<Time> m_timeStamps; // time stamps of load profile
  Time m_lastSampleTime;
  uint64_t m_counter;

  int m_numOfTerms; // # of terms for infinite sum in battery level estimation

  /**
   * Battery level is defined as: output of Discharge function / alpha value
   *
   * The output of Discharge function is an estimated charge consumption of the
   * battery.
   *
   * The alpha value is the amount of charges stored in the battery, or battery
   * capacity (in Coulomb).
   *
   * When the battery is fully charged (no charge is consumed from the battery)
   * the battery level is 1. When the battery is fully discharged, the battery
   * level is 0.
   *
   * NOTE Note that the definition in Timmermann's paper is the inverse of this
   * definition. In the paper, battery level = 1 when the battery is drained.
   */
  TracedValue<double> m_batteryLevel;

  /**
   * (1 / sampling interval) = sampling frequency
   */
  Time m_samplingInterval;
  EventId m_currentSampleEvent;

  TracedValue<Time> m_lifetime;   // time of death of the battery
};

} // namespace ns3

#endif  /* RV_BATTERY_MODEL_H */
