/*
 * This file is part of the Owl Positioning System (OwlPS).
 * OwlPS is a project of the University of Franche-Comté
 * (Université de Franche-Comté), France.
 */


#ifndef _OWLPS_POSITIONING_MEASUREMENT_HH_
#define _OWLPS_POSITIONING_MEASUREMENT_HH_

#include "accesspoint.hh"

#include <vector>
#include <ostream>
#include <cmath>

typedef int_fast16_t ss_t ;

/// Represents a list of signal strengths captured by one AccessPoint
class Measurement
{
protected:
  /// The AccessPoint that performed the measurement
  AccessPoint *ap ;
  /// List of signal strengths captured (in dBm)
  std::vector<ss_t> ss_list ;
  /// Average of all signal strength captured (dBm)
  double average_ss ;

  /** @name Operations */
  //@{
  /// Recalculates #average_ss from #ss_list
  void update_average_ss(void) ;
  //@}


public:
  Measurement(const AccessPoint *_ap = NULL) ;

  Measurement(const AccessPoint *_ap,
              const std::vector<ss_t> &_ss_list) ;

  Measurement(const Measurement &source):
    ap(source.ap), ss_list(source.ss_list),
    average_ss(source.average_ss) {}

  ~Measurement(void) ;

  /** @name Read accessors */
  //@{
  AccessPoint* get_ap() const ;
  const std::vector<ss_t>& get_ss_list() const ;
  double get_average_ss() const ;
  int get_ss_list_size() const ;
  //@}

  /** @name Write accessors */
  //@{
  void set_ap(const AccessPoint *_ap) ;
  void set_ss_list(const std::vector<ss_t> &_ss_list) ;
  /// Adds a signal strength to #ss_list
  void add_ss(const ss_t &ss_dbm) ;
  /// Adds several signal strengths to #ss_list
  void add_ss_list(const std::vector<ss_t> &_ss_list) ;
  /// Merges a given Measurement into the current Measurement
  void merge(const Measurement &source) ;
  void clear(void) ;
  //@}

  /** @name Operations */
  //@{
  /// Computes the distance to another Measurement in SS space
  float ss_square_distance(const Measurement &source) const ;
  /// Computes the distance to another SS value
  float ss_square_distance(const float &ss) const ;
  //@}

  /** @name Operators */
  //@{
  Measurement& operator=(const Measurement &m) ;
  bool operator==(const Measurement &m) const ;
  bool operator!=(const Measurement &m) const ;
  operator bool(void) const ;
  //@}

  /// Displays a Measurement
  friend std::ostream &operator<<(std::ostream &os, const Measurement &m) ;
} ;



/* *** Read accessors *** */


inline AccessPoint* Measurement::get_ap() const
{
  return ap ;
}


inline const std::vector<ss_t>& Measurement::get_ss_list() const
{
  return ss_list ;
}


inline double Measurement::get_average_ss() const
{
  return average_ss ;
}


inline int Measurement::get_ss_list_size() const
{
  return ss_list.size() ;
}



/* *** Write accessors *** */


inline void Measurement::set_ap(const AccessPoint *_ap)
{
  ap = const_cast<AccessPoint*>(_ap) ;
}



/* *** Operations *** */


inline float Measurement::
ss_square_distance(const Measurement &source) const
{
  return ss_square_distance(source.average_ss) ;
}


inline float Measurement::ss_square_distance(const float &ss) const
{
  return ((ss - average_ss) * (ss - average_ss)) ;
}



/* *** Operators *** */


inline bool Measurement::operator!=(const Measurement &m) const
{
  return !(*this == m) ;
}


/**
 * @return \em false if the Measurement is empty.
 * @return \em true if at least one attribute is initialised.
 */
inline Measurement::operator bool() const
{
  return
    ap != NULL ||
    ! ss_list.empty() ;
}



#endif // _OWLPS_POSITIONING_MEASUREMENT_HH_