/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1987, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define TZ_MAX_CHARS 255

static char *_tztab(int, int);

/*
 * timezone --
 *      The arguments are the number of minutes of time you are westward
 *      from Greenwich and whether DST is in effect.  It returns a string
 *      giving the name of the local timezone.  Should be replaced, in the
 *      application code, by a call to localtime.
 */

static char     czone[TZ_MAX_CHARS];            /* space for zone name */

char *
__timezone_compat(int zone, int dst)
{
        char    *beg,
                        *end;

        if ( (beg = getenv("TZNAME")) ) {       /* set in environment */
                if ((end = strchr(beg, ','))) { /* "PST,PDT" */
                        if (dst)
                                return(++end);
                        *end = '\0';
                        (void)strncpy(czone,beg,sizeof(czone) - 1);
                        czone[sizeof(czone) - 1] = '\0';
                        *end = ',';
                        return(czone);
                }
                return(beg);
        }
        return(_tztab(zone,dst));       /* default: table or created zone */
}
__sym_compat(timezone, __timezone_compat, FBSD_1.0);

static struct zone {
        int     offset;
        char    *stdzone;
        char    *dlzone;
} zonetab[] = {
        {-1*60, "MET",  "MET DST"},     /* Middle European */
        {-2*60, "EET",  "EET DST"},     /* Eastern European */
        {4*60,  "AST",  "ADT"},         /* Atlantic */
        {5*60,  "EST",  "EDT"},         /* Eastern */
        {6*60,  "CST",  "CDT"},         /* Central */
        {7*60,  "MST",  "MDT"},         /* Mountain */
        {8*60,  "PST",  "PDT"},         /* Pacific */
#ifdef notdef
        /* there's no way to distinguish this from WET */
        {0,     "GMT",  0},             /* Greenwich */
#endif
        {0*60,  "WET",  "WET DST"},     /* Western European */
        {-10*60,"EST",  "EST"},         /* Aust: Eastern */
     {-10*60+30,"CST",  "CST"},         /* Aust: Central */
        {-8*60, "WST",  0},             /* Aust: Western */
        {-1}
};

/*
 * _tztab --
 *      check static tables or create a new zone name; broken out so that
 *      we can make a guess as to what the zone is if the standard tables
 *      aren't in place in /etc.  DO NOT USE THIS ROUTINE OUTSIDE OF THE
 *      STANDARD LIBRARY.
 */
static char *
_tztab(int zone, int dst)
{
        struct zone     *zp;
        char    sign;

        for (zp = zonetab; zp->offset != -1;++zp)       /* static tables */
                if (zp->offset == zone) {
                        if (dst && zp->dlzone)
                                return(zp->dlzone);
                        if (!dst && zp->stdzone)
                                return(zp->stdzone);
                }

        if (zone < 0) {                                 /* create one */
                zone = -zone;
                sign = '+';
        }
        else
                sign = '-';
        (void)snprintf(czone, sizeof(czone),
            "GMT%c%d:%02d",sign,zone / 60,zone % 60);
        return(czone);
}