sgp4/Julian.h

#ifndef JULIAN_H_
#define JULIAN_H_

#include "Globals.h"
#include "Timespan.h"

#include <ctime>
#include <iostream>

class Julian {
public:
    Julian();
    Julian(const Julian& jul);
    Julian(const time_t t);
    Julian(int year, double day);
    Julian(int year, int mon, int day, int hour, int min, double sec);

    ~Julian() {
    };

    /*
     * comparison operators
     */
    bool operator==(const Julian &date) const;
    bool operator!=(const Julian &date) const;
    bool operator>(const Julian &date) const;
    bool operator<(const Julian &date) const;
    bool operator>=(const Julian &date) const;
    bool operator<=(const Julian &date) const;

    Julian & operator=(const Julian& b);
    Julian & operator=(const double b);
    Julian operator+(const Timespan& b) const;
    Julian operator-(const Timespan& b) const;

    Timespan operator-(const Julian& b) const;

    friend std::ostream & operator<<(std::ostream& stream, const Julian& julian);

    struct DateTimeComponents {
        int years;
        int months;
        int days;
        int hours;
        int minutes;
        double seconds;
    };

    void ToGregorian(struct DateTimeComponents* datetime) const;

    time_t ToTime() const;
    double ToGreenwichSiderealTime() const;
    double ToLocalMeanSiderealTime(const double& lon) const;

    double FromJan1_00h_1900() const {
        return date_ - kEPOCH_JAN1_00H_1900;
    }

    double FromJan1_12h_1900() const {
        return date_ - kEPOCH_JAN1_12H_1900;
    }

    double FromJan1_12h_2000() const {
        return date_ - kEPOCH_JAN1_12H_2000;
    }

    double GetDate() const {
        return date_;
    }

    void AddDay(double day) {
        date_ += day;
    }

    void AddHour(double hr) {
        date_ += (hr / kHOURS_PER_DAY);
    }

    void AddMin(double min) {
        date_ += (min / kMINUTES_PER_DAY);
    }

    void AddSec(double sec) {
        date_ += (sec / kSECONDS_PER_DAY);
    }

    double SpanDay(const Julian& b) const {
        return date_ - b.date_;
    }

    double SpanHour(const Julian& b) const {
        return SpanDay(b) * kHOURS_PER_DAY;
    }

    double SpanMin(const Julian& b) const {
        return SpanDay(b) * kMINUTES_PER_DAY;
    }

    double SpanSec(const Julian& b) const {
        return SpanDay(b) * kSECONDS_PER_DAY;
    }

    static bool IsLeapYear(int y) {
        return (y % 4 == 0 && y % 100 != 0) || (y % 400 == 0);
    }

protected:
    void Initialize(int year, double day);
    void Initialize(int year, int mon, int day, int hour, int min, double sec);

    /*
     * the stored julian date
     */
    double date_;
};

#endif