/*
 * Copyright (C) 1995.  Bill Brown <brown@gis.uiuc.edu> & Michael Shapiro
 *
 * This program is free software under the GPL (>=v2)
 * Read the file GPL.TXT coming with GRASS for details.
 */
#include <time.h>
#include <grass/datetime.h>

extern struct tm *localtime();
extern struct tm *gmtime();

/* 
** NOTE:  the extern variable "timezone" seems to be treated
** differently by different OS, and the tm_zone element of struct tm
** is missing in some OS (IRIX), so we're converting localtime() and
** gmtime() structures to datetimes, then doing a difference to get the
** timezone offset.  -Bill Brown 5/31/95 
*/


/*!
 * \brief 
 *
 * Returns:
 * 0 OK  
 * -1 local timezone info not available 
 *
 *  \param minutes
 *  \return int
 */

int 
datetime_get_local_timezone (int *minutes)
{
    struct tm *local, *gm;
    time_t clock;
    DateTime dtl, dtg, dtdiff;

    time(&clock);

    local = localtime(&clock);

    datetime_set_type (&dtl,DATETIME_ABSOLUTE,DATETIME_YEAR,DATETIME_SECOND,0);

/* now put current {year,month,day,hour,minute,second} into local */
    datetime_set_year (&dtl, (int)local->tm_year + 1900);
    datetime_set_month (&dtl, (int)local->tm_mon + 1);
    datetime_set_day (&dtl, (int)local->tm_mday);
    datetime_set_hour (&dtl, (int)local->tm_hour);
    datetime_set_minute (&dtl, (int)local->tm_min);
    datetime_set_second (&dtl, (double)local->tm_sec);

    gm = gmtime(&clock);

    datetime_set_type (&dtg,DATETIME_ABSOLUTE,DATETIME_YEAR,DATETIME_SECOND,0);

/* now put current {year,month,day,hour,minute,second} into gmt */
    datetime_set_year (&dtg, (int)gm->tm_year + 1900);
    datetime_set_month (&dtg, (int)gm->tm_mon + 1);
    datetime_set_day (&dtg, (int)gm->tm_mday);
    datetime_set_hour (&dtg, (int)gm->tm_hour);
    datetime_set_minute (&dtg, (int)gm->tm_min);
    datetime_set_second (&dtg, (double)gm->tm_sec);

    datetime_set_type (&dtdiff,DATETIME_RELATIVE,
		    DATETIME_DAY,DATETIME_SECOND,0);
    datetime_difference (&dtl, &dtg, &dtdiff);
    datetime_change_from_to(&dtdiff, DATETIME_MINUTE, DATETIME_MINUTE, 0);

    *minutes = dtdiff.positive? dtdiff.minute: -dtdiff.minute;
    return 0;
}


/*!
 * \brief 
 *
 * set mode/from/to ABSOLUTE/YEAR/SECOND  
 * set the local time into 'dt'  does not set timezone.  
 *
 *  \param dt
 *  \return void
 */

void
datetime_get_local_time (DateTime *dt)

{
    long clock;
    struct tm *local;

/* first set dt to absolute full date */
    datetime_set_type (dt,DATETIME_ABSOLUTE,DATETIME_YEAR,DATETIME_SECOND,0);

/* get the current date/time */
    time(&clock);
    local = localtime(&clock);

/* now put current {year,month,day,hour,minute,second} into dt */
    datetime_set_year (dt, (int)local->tm_year + 1900);
    datetime_set_month (dt, (int)local->tm_mon + 1);
    datetime_set_day (dt, (int)local->tm_mday);
    datetime_set_hour (dt, (int)local->tm_hour);
    datetime_set_minute (dt, (int)local->tm_min);
    datetime_set_second (dt, (double)local->tm_sec);
}
