#ifndef _utl_LeapSeconds_h_
#define _utl_LeapSeconds_h_

#include <string>
#include <map>
#include <ctime>
#include <utl/Singleton.h>


namespace utl {

  /**
    \class LeapSeconds LeapSeconds.h utl/LeapSeconds.h

    Quick definition: a <b>positive</b> leap second is a GPS second where the UTC second
    is exceptionally allowed to take the value of 60, i.e. the seconds run as
    58, 59, 60, 00, 01... A <b>negative</b> leap second is removed from the last second
    of a day preceding the midnight, i.e. the day runs only until second 58 and jumps
    directly to 00 of the next day.

    \image html utl_LeapSeconds.png

    \author Darko Veberic
    \date 16 Jul 2009
    \version $Id$
    \ingroup time
  */

  class LeapSeconds : public Singleton<LeapSeconds> {
  private:
    // pair contains leap and accumulated leaps
    typedef std::map<unsigned long, std::pair<int, int> > GPSToUnixMap;
    typedef GPSToUnixMap::const_iterator GPSToUnixIterator;

    typedef std::map<std::time_t, long> UnixToGPSMap;
    typedef UnixToGPSMap::const_iterator UnixToGPSIterator;

  public:
    LeapSeconds() : fTZ(0) { Init(); SetUTC(); }
    ~LeapSeconds() { UnsetUTC(); }

    /// returns true if the GPS second is an UTC leap second
    bool ConvertGPSToUnix(const unsigned long gpsSecond, time_t& unixSecond) const;

    void ConvertUnixToGPS(const time_t unixSecond, unsigned long& gpsSecond) const;

    void Dump() const;

  private:
    void Init();

    void SetUTC();

    void UnsetUTC();

    std::time_t fGPSEpochInUnixSeconds;

    GPSToUnixMap fGPSToUnixLeaps;
    UnixToGPSMap fUnixToGPSLeaps;
    std::string* fTZ;
  };

}


#endif