// Time.h

#ifndef dset__Time_H
#define dset__Time_H

// Class to hold time and time interval.

#include <string>
#include <iosfwd>

class TimeInterval;

// Absolute time.

class Time {

public:  // static methods

  // Reuturn the current time.
  static Time now();

private:  // data

  unsigned long m_time;

public:  // methods

  // Constructor.
  // Default is invalid.
  explicit Time(unsigned long tim =0);

  // Set the time to now.
  Time& set();

  // Add a time interval.
  Time& operator+=(TimeInterval dtim);

  // Subtract a time interval.
  Time& operator-=(TimeInterval dtim);

  // Is this a valid time (nonzero).
  bool is_valid() const;

  // Unix time (seconds since 1970).
  unsigned long unix_time() const;

  // Formatted UTC.
  // e.g. 2005 Jun 21 16:45:33
  std::string to_string() const;

};

// Time interval.

class TimeInterval {

private:  // data

  long m_dtime;

public:  // methods

  // Constructor from interval in seconds.
  explicit TimeInterval(long dtime =0);

  // Constructor from start and stop times.
  TimeInterval(Time start, Time stop);

  // Add a time interval.
  TimeInterval& operator+=(TimeInterval dtim);

  // Subtract a time interval.
  TimeInterval& operator-=(TimeInterval dtim);

  // Time interval in seconds.
  long seconds() const;

  // Formatted dys:hrs:min:sec.
  // E.g. 3:05:35:22
  std::string to_string() const;

};
  
// Time output stream.
std::ostream& operator<<(std::ostream& lhs, const Time& rhs);

// TimeInterval output stream.
std::ostream& operator<<(std::ostream& lhs, const TimeInterval& rhs);

#endif