DateTime.h

//-*- C++ -*-
//-*- coding: utf-8 -*-
//
//
// Author: Piyush Agram
// Copyright 2017-2018

#pragma once

#include "forward.h"

#include <cassert>
#include <cmath>
#include <iostream>
#include <string>

class isce3::core::DateTime {
public:

    int year;
    int months;
    int days;
    int hours;
    int minutes;
    int seconds;
    double frac;

    DateTime() : DateTime(1970, 1, 1) {};

    DateTime(double ord);

    DateTime(int yy, int mm, int dd);

    DateTime(int yy, int mm, int dd, int hh, int mn, int ss);

    DateTime(int yy, int mm, int dd, int hh, int mn, double ss);

    DateTime(int yy, int mm, int dd, int hh, int mn, int ss, double ff);

    DateTime(const DateTime& ts);

    DateTime(const std::string &);

    void _init(int yy, int mm, int dd, int hh, int mn, int ss, double ff);
    void _normalize_time();
    void _normalize_date();
    void _normalize();

    explicit operator std::string() const { return isoformat(); }

    // Comparison operators
    bool operator<(const DateTime &ts) const;
    bool operator>(const DateTime &ts) const;
    bool operator<=(const DateTime &ts) const;
    bool operator>=(const DateTime &ts) const;
    bool operator==(const DateTime &ts) const;
    bool operator!=(const DateTime &ts) const;

    // Math operators
    DateTime& operator=(const DateTime& ts);
    DateTime& operator=(const std::string &);
    DateTime& operator+=(const TimeDelta& ts);
    DateTime& operator+=(const double& s);
    DateTime& operator-=(const TimeDelta& ts);
    DateTime& operator-=(const double& s);

    DateTime operator+(const TimeDelta& ts) const;
    DateTime operator+(const double& s) const;
    DateTime operator-(const TimeDelta& ts) const;
    DateTime operator-(const double& s) const;

    TimeDelta operator-(const DateTime& ts) const;

    bool isClose(const DateTime& ts) const;

    bool isClose(const DateTime& ts, const TimeDelta& errtol) const;

    int dayOfYear() const;

    double secondsOfDay() const;

    int dayOfWeek() const;

    double ordinal() const;

    double secondsSinceEpoch() const;

    double secondsSinceEpoch(const DateTime &) const;

    void secondsSinceEpoch(double);

    std::string isoformat() const;

    void strptime(const std::string &, const std::string & sep = "T");
};

// Some constants
namespace isce3 {
    namespace core {

        std::ostream & operator<<(std::ostream &, const DateTime &);

        // Constants for default constructors
        const DateTime MIN_DATE_TIME = DateTime(1970, 1, 1);
        const std::string UNINITIALIZED_STRING = "uninitialized";

        static const int DaysInMonths[] = {31,28,31,
                                       30,31,30,
                                       31,31,30,
                                       31,30,31};

        static const int DaysBeforeMonths[] = {0,31,59,
                                              90,120,151,
                                              181,212,243,
                                              273,304,334};
        static const int DAY_TO_YEAR = 365;
        static const int DAYSPER100  = 36524;
        static const int DAYSPER400  = 146097;
        static const int DAYSPER4    = 1461;
        static const int MAXORDINAL  = 3652059;

        static const double TOL_SECONDS = 1e-10;

        // Handful of utility functions
        bool _is_leap(int);
        int _days_in_month(int, int);
        int _days_before_year(int);
        int _days_before_month(int, int);
        int _ymd_to_ord(int, int, int);
        void _ord_to_ymd(int, int &, int &, int &);
    }
}