#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <math.h>
#include "wgrib2.h"
#include "CodeTable4_4.h"

#define  FEB29   (31+29)
static int monthjday[13] = {
        0,31,59,90,120,151,181,212,243,273,304,334,365};

static int leap(int year) {
	if (year % 4 != 0) return 0;
	if (year % 100 != 0) return 1;
	return (year % 400 == 0);
}

/* see if date code is reasonable */

int check_datecode(int year, int month, int day) {
   int days_in_month;

   if (year < 0) return 1;
   if (month <= 0 || month > 12) return 2;
   if (day < 1) return 3;
   days_in_month = monthjday[month] - monthjday[month-1];
   if (month == 2 && leap(year)) {
         days_in_month++;
   }
   if (day <= days_in_month) return 0;
   return 3;
}

/* see if time is reasonable */

int check_time(int year, int month, int day, int hour, int minute, int second) {

    if (hour < 0 || hour > 23) return 4;
    if (minute < 0 || minute > 59) return 5;
    if (second < 0 || minute > 59) return 6;
    return check_datecode(year, month, day);
}

/*
    add_time:  adds a positive value to a time code
    public domain 2006: wesley ebisuzaki
    1/2007 cleanup M. Schwarb, W. Ebisuzaki
    1/2006 removed floor(), case where floor(24/24.0) == 0
    some day should allow +/- dtime (not needed for this application
    when adding 1 month, make sure day of month is legal
    4/2015: dtime is now integer
 */

int add_time(int *year, int *month, int *day, int *hour, int *minute, int *second, 
   int dtime, int unit) {
     if (dtime == 0) return 0;
     if (dtime > 0) return add_dt(year, month, day, hour, minute, second, dtime, unit);
     return sub_dt(year, month, day, hour, minute, second, -dtime, unit);
}

int Add_time(struct full_date *date, int dtime, int unit) {
     if (dtime == 0) return 0;
     if (dtime > 0) 
       return add_dt(&(date->year), &(date->month), &(date->day), &(date->hour), &(date->minute), &(date->second), dtime, unit);
     return sub_dt(&(date->year), &(date->month), &(date->day), &(date->hour), &(date->minute), &(date->second), -dtime, unit);
}

int add_dt(int *year, int *month, int *day, int *hour, int *minute, int *second, 
   int dtime, int unit) {

    int y, m, d, h, mm, s, jday, i, days_in_month;

    y = *year;
    m = *month;
    d = *day;
    h = *hour;
    mm = *minute;
    s = *second;

    if (unit == 255 || unit == -1) return 0;	// no valid time unit
    if (dtime == 0xffffffff) return 0;		// missing dtime

    if (unit == YEAR) {
	*year = y + dtime;
	return 0;
    }
    if (unit == DECADE) {
	*year =  y + (10 * dtime);
	return 0;
    }
    if (unit == CENTURY) {
	*year = y + (100 * dtime);
	return 0;
    }
    if (unit == NORMAL) {
	*year = y + (30 * dtime);
	return 0;
    }
    if (unit == MONTH) {
/*
        if (dtime < 0) {
           i = (-dtime) / 12 + 1;
           y -= i;
           dtime += (i * 12);
        }
*/
	dtime += (m - 1);
	*year = y = y + (dtime / 12);
	*month = m = 1 + (dtime % 12);

        /* check if date code if valid */
        days_in_month = monthjday[m] - monthjday[m-1];
        if (m == 2 && leap(y)) {
            days_in_month++;
        }
        if (days_in_month < d) *day = days_in_month;

	return 0;
    }
    if (unit == SECOND) {
	s += dtime;
	// dtime = floor(s/60.0);
	dtime =  s / 60;
	*second = s - dtime*60;
	if (dtime == 0) return 0;
	unit = MINUTE;
    }
    if (unit == MINUTE) {
	mm += dtime;
	// dtime = floor(mm/60.0);
	dtime = mm /60;
	*minute = mm - dtime*60;
	if (dtime == 0) return 0;
	unit = HOUR;
    }
    if (unit == HOUR3) {
	dtime *= 3;
	unit = HOUR;
    }
    if (unit == HOUR6) {
	dtime *= 6;
	unit = HOUR;
    }
    if (unit == HOUR12) {
	dtime *= 12;
	unit = HOUR;
    }
    if (unit == HOUR) {
	h += dtime;
	// dtime = floor(h/24.0);
	dtime = h / 24;
	*hour = h - dtime*24;
	if (dtime == 0) return 0;
	unit = DAY;
    }

    /* this is the hard part */

    if (unit == DAY) {
	/* set m and day to Jan 0, and readjust dtime */
	jday = d + monthjday[m-1];
	if (leap(y) && m > 2) jday++;
        dtime += jday;
/*
        while (dtime < 0) {
            y--;
	    dtime += 365 + leap(y);
        }
*/
	/* one year chunks */
	while (dtime > 365 + leap(y)) {
	    dtime -= (365 + leap(y));
	    y++;
	}

	/* calculate the month and day */

	if (leap(y) && dtime == FEB29) {
	    m = 2;
	    d = 29;
	}
	else {
	    if (leap(y) && dtime > FEB29) dtime--;
	    for (i = 11; monthjday[i] >= dtime; --i);
	    m = i + 1;
	    d = dtime - monthjday[i];
	}
	*year = y;
	*month = m;
	*day = d;
	return 0;
   }
   fprintf(stderr,"add_time: undefined time unit %d\n", unit);
   return 1;
}

/*
 * figures out (date) - dt
 */

int sub_dt(int *year, int *month, int *day, int *hour, int *minute, int *second, 
	int dtime, int unit) {

    int y, m, d, h, mm, s, jday, i, days_in_month;

    y = *year;
    m = *month;
    d = *day;
    h = *hour;
    mm = *minute;
    s = *second;
    if (unit == 255 || unit == -1) return 0;    // no valid time unit

    if (unit == YEAR) {
        *year = y - dtime;
        return 0;
    }
    if (unit == DECADE) {
        *year =  y - (10 * dtime);
        return 0;
    }
    if (unit == CENTURY) {
        *year = y - (100 * dtime);
        return 0;
    }
    if (unit == NORMAL) {
        *year = y - (30 * dtime);
        return 0;
    }
    if (unit == MONTH) {
        dtime += (12-m);
	*year = y = y - (dtime / 12);
        *month = m = 12 - (dtime % 12);
        /* check if date code if valid */
        days_in_month = monthjday[m] - monthjday[m-1];
        if (m == 2 && leap(y)) {
            days_in_month++;
        }
        if (days_in_month < d) *day = days_in_month;

        return 0;
    }
    if (unit == SECOND) {
	dtime += (59 - s);
	*second = s = 59 - (dtime % 60);
	dtime = dtime / 60;
	if (dtime == 0) return 0;
	unit = MINUTE;
    }
    if (unit == MINUTE) {
	dtime += (59 - mm);
	*minute = mm = 59 - dtime % 60;
	dtime = dtime / 60;
	if (dtime == 0) return 0;
	unit = HOUR;
    }
    if (unit == HOUR3) {
	dtime *= 3;
	unit = HOUR;
    }
    if (unit == HOUR6) {
	dtime *= 6;
	unit = HOUR;
    }
    if (unit == HOUR12) {
	dtime *= 12;
	unit = HOUR;
    }
    if (unit == HOUR) {
	dtime += (23-h);
	*hour = h = 23 - dtime%24;
       	dtime = dtime / 24; 
	if (dtime == 0) return 0;
	unit = DAY;
    }

    /* this is the hard part */

    if (unit == DAY) {
        /* set m and day to Jan 0, and readjust dtime */
        jday = d + monthjday[m-1];
        if (leap(y) && m > 2) jday++;

	while (dtime >= jday) {
	    // set date to dec 31 of previous year
	    y = y - 1;
	    m = 12;
	    d = 31;
	    dtime -= jday;
	    jday = 365 + leap(y);
	}

	jday -= dtime;

        /* calculate the month and day */

        if (leap(y) && jday == FEB29) {
            m = 2;
            d = 29;
        }
        else {
            if (leap(y) && jday > FEB29) jday--;
            for (i = 11; monthjday[i] >= jday; --i);
            m = i + 1;
            d = jday - monthjday[i];
        }
        *year = y;
        *month = m;
        *day = d;
        return 0;
   }
   fprintf(stderr,"add_time: undefined time unit %d\n", unit);
   return 1;
}


/*
   This routine reads year/month/day.../second byte code and saves it in variables
 */

int get_time(unsigned char *p, int *year, int *month, int *day, int *hour, int *minute, int *second) {
    *year = (p[0] << 8) | p[1];
    p += 2;
    *month = (int) *p++;
    *day = (int) *p++;
    *hour = (int) *p++;
    *minute = (int) *p++;
    *second = (int) *p;
    return 0;
}

/*
   This routine reads year/month/day.../second byte code and saves it in struct full_date
 */

int Get_time(unsigned char *p, struct full_date *date) {
    date->year = (p[0] << 8) | p[1];
    date->month = p[2];
    date->day = p[3];
    date->hour = p[4];
    date->minute = p[5];
    date->second = p[6];
    return 0;
}



/*
   inverse of get_time .. save time code in PDS
 */

int save_time(int year, int month, int day, int hour, int minute, int second, unsigned char *p) {

    *p++ = (unsigned char) (year >> 8) & 255;
    *p++ = (unsigned char) year & 255;
    *p++ = (unsigned char) month;
    *p++ = (unsigned char) day;
    *p++ = (unsigned char) hour;
    *p++ = (unsigned char) minute;
    *p++ = (unsigned char) second;
    return 0;
}

/*
   inverse of get_time .. save struct *full_date  in PDS
 */

int Save_time(struct full_date *date, unsigned char *p) {

    *p++ = (unsigned char) (date->year >> 8) & 255;
    *p++ = (unsigned char) date->year & 255;
    *p++ = (unsigned char) date->month;
    *p++ = (unsigned char) date->day;
    *p++ = (unsigned char) date->hour;
    *p++ = (unsigned char) date->minute;
    *p++ = (unsigned char) date->second;
    return 0;
}


/*
   compare two time codes: return -1 : 0 : 1
 */

int cmp_time(
int year0, int month0, int day0, int hour0, int minute0, int second0, 
int year1, int month1, int day1, int hour1, int minute1, int second1) {

	if (year0 < year1) return -1;
	if (year0 > year1) return 1;
	if (month0 < month1) return -1;
	if (month0 > month1) return 1;
	if (day0 < day1) return -1;
	if (day0 > day1) return 1;
	if (hour0 < hour1) return -1;
	if (hour0 > hour1) return 1;
	if (minute0 < minute1) return -1;
	if (minute0 > minute1) return 1;
	if (second0 < second1) return -1;
	if (second0 > second1) return 1;
	return 0;
}

/*
   compare two time codes: return -1 : 0 : 1
 */
int Cmp_time(struct full_date *date0, struct full_date *date1) {

	if (date0->year < date1->year) return -1;
	if (date0->year > date1->year) return  1;

	if (date0->month < date1->month) return -1;
	if (date0->month > date1->month) return  1;

	if (date0->day < date1->day) return -1;
	if (date0->day > date1->day) return  1;

	if (date0->hour < date1->hour) return -1;
	if (date0->hour > date1->hour) return  1;

	if (date0->minute < date1->minute) return -1;
	if (date0->minute > date1->minute) return  1;

	if (date0->second < date1->second) return -1;
	if (date0->second > date1->second) return  1;

	return 0;
}