/*
 * Copyright (c) 1998-2001 Sendmail, Inc. and its suppliers.
 *      All rights reserved.
 * Copyright (c) 1983, 1995-1997 Eric P. Allman.  All rights reserved.
 * Copyright (c) 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * By using this file, you agree to the terms and conditions set
 * forth in the LICENSE file which can be found at the top level of
 * the sendmail distribution.
 *
 */

#include <sendmail.h>

SM_RCSID("@(#)$Id: arpadate.c,v 8.31 2006/08/15 23:24:55 ca Exp $")

/*
**  ARPADATE -- Create date in ARPANET format
**
**      Parameters:
**              ud -- unix style date string.  if NULL, one is created.
**
**      Returns:
**              pointer to an ARPANET date field
**
**      Side Effects:
**              none
**
**      WARNING:
**              date is stored in a local buffer -- subsequent
**              calls will overwrite.
**
**      Bugs:
**              Timezone is computed from local time, rather than
**              from wherever (and whenever) the message was sent.
**              To do better is very hard.
**
**              Some sites are now inserting the timezone into the
**              local date.  This routine should figure out what
**              the format is and work appropriately.
*/

#ifndef TZNAME_MAX
# define TZNAME_MAX     50      /* max size of timezone */
#endif /* ! TZNAME_MAX */

/* values for TZ_TYPE */
#define TZ_NONE         0       /* no character timezone support */
#define TZ_TM_NAME      1       /* use tm->tm_name */
#define TZ_TM_ZONE      2       /* use tm->tm_zone */
#define TZ_TZNAME       3       /* use tzname[] */
#define TZ_TIMEZONE     4       /* use timezone() */

char *
arpadate(ud)
        register char *ud;
{
        register char *p;
        register char *q;
        register int off;
        register int i;
        register struct tm *lt;
        time_t t;
        struct tm gmt;
        char *tz;
        static char b[43 + TZNAME_MAX];

        /*
        **  Get current time.
        **      This will be used if a null argument is passed and
        **      to resolve the timezone.
        */

        /* SM_REQUIRE(ud == NULL || strlen(ud) >= 23); */
        t = curtime();
        if (ud == NULL)
                ud = ctime(&t);

        /*
        **  Crack the UNIX date line in a singularly unoriginal way.
        */

        q = b;

        p = &ud[0];             /* Mon */
        *q++ = *p++;
        *q++ = *p++;
        *q++ = *p++;
        *q++ = ',';
        *q++ = ' ';

        p = &ud[8];             /* 16 */
        if (*p == ' ')
                p++;
        else
                *q++ = *p++;
        *q++ = *p++;
        *q++ = ' ';

        p = &ud[4];             /* Sep */
        *q++ = *p++;
        *q++ = *p++;
        *q++ = *p++;
        *q++ = ' ';

        p = &ud[20];            /* 1979 */
        *q++ = *p++;
        *q++ = *p++;
        *q++ = *p++;
        *q++ = *p++;
        *q++ = ' ';

        p = &ud[11];            /* 01:03:52 */
        for (i = 8; i > 0; i--)
                *q++ = *p++;

        /*
        **  should really get the timezone from the time in "ud" (which
        **  is only different if a non-null arg was passed which is different
        **  from the current time), but for all practical purposes, returning
        **  the current local zone will do (its all that is ever needed).
        */

        gmt = *gmtime(&t);
        lt = localtime(&t);

        off = (lt->tm_hour - gmt.tm_hour) * 60 + lt->tm_min - gmt.tm_min;

        /* assume that offset isn't more than a day ... */
        if (lt->tm_year < gmt.tm_year)
                off -= 24 * 60;
        else if (lt->tm_year > gmt.tm_year)
                off += 24 * 60;
        else if (lt->tm_yday < gmt.tm_yday)
                off -= 24 * 60;
        else if (lt->tm_yday > gmt.tm_yday)
                off += 24 * 60;

        *q++ = ' ';
        if (off == 0)
        {
                *q++ = 'G';
                *q++ = 'M';
                *q++ = 'T';
        }
        else
        {
                tz = NULL;
#if TZ_TYPE == TZ_TM_NAME
                tz = lt->tm_name;
#endif /* TZ_TYPE == TZ_TM_NAME */
#if TZ_TYPE == TZ_TM_ZONE
                tz = lt->tm_zone;
#endif /* TZ_TYPE == TZ_TM_ZONE */
#if TZ_TYPE == TZ_TZNAME
                {
                        extern char *tzname[];

                        if (lt->tm_isdst > 0)
                                tz = tzname[1];
                        else if (lt->tm_isdst == 0)
                                tz = tzname[0];
                        else
                                tz = NULL;
                }
#endif /* TZ_TYPE == TZ_TZNAME */
#if TZ_TYPE == TZ_TIMEZONE
                {
                        extern char *timezone();

                        tz = timezone(off, lt->tm_isdst);
                }
#endif /* TZ_TYPE == TZ_TIMEZONE */
                if (off < 0)
                {
                        off = -off;
                        *q++ = '-';
                }
                else
                        *q++ = '+';

                if (off >= 24*60)               /* should be impossible */
                        off = 23*60+59;         /* if not, insert silly value */

                *q++ = (off / 600) + '0';
                *q++ = (off / 60) % 10 + '0';
                off %= 60;
                *q++ = (off / 10) + '0';
                *q++ = (off % 10) + '0';
                if (tz != NULL && *tz != '\0')
                {
                        *q++ = ' ';
                        *q++ = '(';
                        while (*tz != '\0' && q < &b[sizeof(b) - 3])
                                *q++ = *tz++;
                        *q++ = ')';
                }
        }
        *q = '\0';

        return b;
}