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/* Miscellaneous time-related utilities
 *
 * Copyright (C) 1998 The Free Software Foundation
 *
 * Authors: Federico Mena <federico@nuclecu.unam.mx>
 *          Miguel de Icaza <miguel@nuclecu.unam.mx>
 */

#include <libgnome/libgnome.h>
#include <string.h>
#include "timeutil.h"

#define digit_at(x,y) (x [y] - '0')
    
time_t
time_from_isodate (char *str)
{
    struct tm my_tm;
    time_t t;

    if (strlen (str) < 14)
        return -1;
    
    my_tm.tm_year = (digit_at (str, 0) * 1000 + digit_at (str, 1) * 100 +
        digit_at (str, 2) * 10 + digit_at (str, 3)) - 1900;

    my_tm.tm_mon  = digit_at (str, 4) * 10 + digit_at (str, 5) - 1;
    my_tm.tm_mday = digit_at (str, 6) * 10 + digit_at (str, 7);
    my_tm.tm_hour = digit_at (str, 9) * 10 + digit_at (str, 10);
    my_tm.tm_min  = digit_at (str, 11) * 10 + digit_at (str, 12);
    my_tm.tm_sec  = digit_at (str, 13) * 10 + digit_at (str, 14);
    my_tm.tm_isdst = -1;
    
    t = mktime (&my_tm);

    if (str [15] == 'Z')
        t -= timezone;
        
    return t;
}

void
print_time_t (time_t t)
{
    struct tm *tm = localtime (&t);
    
    printf ("TIEMPO: %d/%d/%d %d:%d:%d\n",
        tm->tm_mon+1, tm->tm_mday, tm->tm_year,
        tm->tm_hour, tm->tm_min, tm->tm_sec);
}

int
get_time_t_hour (time_t t)
{
    struct tm *tm;

    tm = localtime (&t);
    return tm->tm_hour;
}

char *
isodate_from_time_t (time_t t)
{
    struct tm *tm;
    static char isotime [40];

    tm = localtime (&t);
    strftime (isotime, sizeof (isotime)-1, "%Y%m%dT%H%M%S", tm);
    return isotime;
}

time_t
time_from_start_duration (time_t start, char *duration)
{
    printf ("Not yet implemented\n");
    return 0;
}

char *
format_simple_hour (int hour, int use_am_pm)
{
    static char buf[256];

    /* I don't know whether this is the best way to internationalize it.
     * Does any language use different conventions? - Federico
     */

    if (use_am_pm)
        sprintf (buf, "%d%s",
             (hour == 0) ? 12 : (hour > 12) ? (hour - 12) : hour,
             (hour < 12) ? _("am") : _("pm"));
    else
        sprintf (buf, "%02d%s", hour, _("h"));

    return buf;

}

time_t
time_add_minutes (time_t time, int minutes)
{
    struct tm *tm = localtime (&time);
    time_t new_time;

    tm->tm_min += minutes;
    if ((new_time = mktime (tm)) == -1){
        g_warning ("mktime could not handling adding a day with\n");
        print_time_t (time);
        return time;
    }
    return new_time;
}

time_t
time_add_day (time_t time, int days)
{
    struct tm *tm = localtime (&time);
    time_t new_time;
    int dst_flag = tm->tm_isdst;

    tm->tm_mday += days;

    if ((new_time = mktime (tm)) == -1){
        g_warning ("mktime could not handling adding a day with\n");
        print_time_t (time);
        return time;
    }

    if (dst_flag > tm->tm_isdst){
        tm->tm_hour++;
        new_time += 3600;
    } else if (dst_flag < tm->tm_isdst){
        tm->tm_hour--;
        new_time -= 3600;
    }

    return new_time;
}

time_t
time_add_week (time_t time, int weeks)
{
    return time_add_day (time, weeks * 7);
}

time_t
time_add_month (time_t time, int months)
{
    struct tm *tm = localtime (&time);
    time_t new_time;
    int mday;

    mday = tm->tm_mday;
    
    tm->tm_mon += months;
    tm->tm_isdst = -1;
    if ((new_time = mktime (tm)) == -1){
        g_warning ("mktime could not handling adding a month with\n");
        print_time_t (time);
        return time;
    }
    tm = localtime (&new_time);
    if (tm->tm_mday < mday){
        tm->tm_mon--;
        tm->tm_mday = time_days_in_month (tm->tm_year+1900, tm->tm_mon);
        return new_time = mktime (tm);
    }
    else
        return new_time;
}

time_t
time_add_year (time_t time, int years)
{
    struct tm *tm = localtime (&time);
    time_t new_time;
    
    tm->tm_year += years;
    if ((new_time = mktime (tm)) == -1){
        g_warning ("mktime could not handling adding a year with\n");
        print_time_t (time);
        return time;
    }
    return new_time;
}

time_t
time_day_hour (time_t t, int hour)
{
    struct tm tm;
    
    tm = *localtime (&t);
    tm.tm_hour = hour;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;

    return mktime (&tm);
}

/* Number of days in a month, for normal and leap years */
static const int days_in_month[2][12] = {
    { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
    { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
};

/* Returns whether the specified year is a leap year */
static int
is_leap_year (int year)
{
    if (year <= 1752)
        return !(year % 4);
    else
        return (!(year % 4) && (year % 100)) || !(year % 400);
}

int
time_days_in_month (int year, int month)
{
    g_return_val_if_fail (year >= 1900, 0);
    g_return_val_if_fail ((month >= 0) && (month < 12), 0);

    return days_in_month [is_leap_year (year)][month];
}

time_t
time_from_day (int year, int month, int day)
{
    struct tm tm;

    memset (&tm, 0, sizeof (tm));
    tm.tm_year = year - 1900;
    tm.tm_mon = month;
    tm.tm_mday = day;

    return mktime (&tm);
}

time_t
time_year_begin (time_t t)
{
    struct tm tm;

    tm = *localtime (&t);
    tm.tm_hour = 0;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    tm.tm_mon  = 0;
    tm.tm_mday = 1;
    tm.tm_isdst = -1;

    return mktime (&tm);
}

time_t
time_year_end (time_t t)
{
    struct tm tm;

    tm = *localtime (&t);
    tm.tm_hour = 0;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    tm.tm_mon  = 0;
    tm.tm_mday = 1;
    tm.tm_year++;
    tm.tm_isdst = -1;

    return mktime (&tm);
}

time_t
time_month_begin (time_t t)
{
    struct tm tm;

    tm = *localtime (&t);
    tm.tm_hour = 0;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    tm.tm_mday = 1;
    tm.tm_isdst = -1;

    return mktime (&tm);
}

time_t
time_month_end (time_t t)
{
    struct tm tm;

    tm = *localtime (&t);
    tm.tm_hour = 0;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    tm.tm_mday = 1;
    tm.tm_mon++;
    tm.tm_isdst = -1;

    return mktime (&tm);
}

time_t
time_week_begin (time_t t)
{
    struct tm tm;

    /* FIXME: make it take week_starts_on_monday into account */

    tm = *localtime (&t);
    tm.tm_hour = 0;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    tm.tm_mday -= tm.tm_wday;

    return mktime (&tm);
}

time_t
time_week_end (time_t t)
{
    struct tm tm;

    /* FIXME: make it take week_starts_on_monday into account */

    tm = *localtime (&t);
    tm.tm_hour = 0;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    tm.tm_mday += 7 - tm.tm_wday;

    return mktime (&tm);
}

time_t
time_day_begin (time_t t)
{
    struct tm tm;
    time_t temp = t - 43200;
    int dstflag, dstflag2;
    
    tm = *localtime(&temp); /* one day */
    dstflag = tm.tm_isdst;

    tm = *localtime (&t);
    dstflag2 = tm.tm_isdst;

    if (dstflag < dstflag2)
        tm.tm_hour = 1;
    else
        tm.tm_hour = 0;

    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    
    temp = mktime(&tm);
    if (dstflag > dstflag2){
        temp += 3600; 
    }

    return temp;
}

time_t
time_day_end (time_t t)
{
    struct tm tm;
    time_t temp;
    int dstflag, dstflag2;

    t += 10800;
    temp = t - 86400;

    tm = *localtime(&temp); /* one day */
    dstflag = tm.tm_isdst;

    tm = *localtime (&t);
    dstflag2 = tm.tm_isdst;

    if (dstflag < dstflag2)
        tm.tm_hour = 23;
    else {
        tm.tm_mday++;
        tm.tm_hour = 0;
    }
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    
    temp = mktime(&tm);
    if(dstflag > dstflag2) {
    }
    return temp;
}

static char *
pcat (char *dest, int num, char key)
{
    int c;

    c = sprintf (dest, "%d%c", num, key);
    return dest + c;
}

/* Converts secs into the ISO difftime representation */
char *
isodiff_from_secs (int secs)
{
    static char buffer [60], *p;
    int years, months, weeks, days, hours, minutes;
    
    years = months = weeks = days = hours = minutes = 0;
    
    years    = secs / (365 * 86400);
    secs    %= (365 * 86400);
    months   = secs / (30 * 86400);
    secs    %= (30 * 86400);
    weeks    = secs / (7 * 86400);
    secs    %= (7 * 86400);
    days     = secs / 86400;
    secs    %= 86400;
    hours    = secs / 3600;
    secs    %= 3600;
    minutes  = secs / 60;
    secs    %= 60;

    strcpy (buffer, "P");
    p = buffer + 1;
    if (years)
        p = pcat (p, years, 'Y');
    if (months)
        p = pcat (p, months, 'M');
    if (weeks)
        p = pcat (p, weeks, 'W');
    if (days)
        p = pcat (p, days, 'D');
    if (hours || minutes || secs){
        *p++ = 'T';
        if (hours)
            p = pcat (p, hours, 'H');
        if (minutes)
            p = pcat (p, minutes, 'M');
        if (secs)
            p = pcat (p, secs, 'S');
    }
    
    return buffer;
}

int
isodiff_to_secs (char *str)
{
    int value, time;
    int years, months, weeks, days, hours, minutes, seconds;

    value = years = months = weeks = days = hours = minutes = time = seconds = 0;
    if (*str != 'P')
        return 0;

    str++;
    while (*str){
        switch (*str){
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
            value = value * 10 + (*str - '0');
            break;
        case 'Y':
            years = value; value = 0;
            break;
        case 'M':
            if (time)
                minutes = value;
            else
                months = value;
            value = 0;
            break;
        case 'W':
            weeks = value; value = 0;
            break;
        case 'D':
            days = value; value = 0;
            break;
        case 'T':
            value = 0; time = 1;
            break;
        case 'H':
            hours = value; value = 0;
            break;
        case 'S':
            seconds = value; value = 0;
            break;
        }
        str++;
    }
    return seconds + (minutes * 60) + (hours * 3600) +
           (days * 86400) + (weeks * 7 * 86400) +
           (months * 30 * 86400) + (years * 365 * 86400);
}