/*      $OpenBSD: rcstime.c,v 1.7 2025/09/15 19:37:35 millert Exp $     */
/*
 * Copyright (c) 2006 Joris Vink <joris@openbsd.org>
 * 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. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED ``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 AUTHOR 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 <err.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include "rcs.h"

void
rcs_set_tz(char *tz, struct rcs_delta *rdp, struct tm *tb)
{
        int tzone;
        int pos;
        char *h, *m;
        const char *errstr;
        struct tm *ltb;
        time_t now;

        if (!strcmp(tz, "LT")) {
                /* rd_date is stored in UTC, convert to local time. */
                now = timegm(&rdp->rd_date);
                ltb = localtime(&now);
                memcpy(tb, ltb, sizeof(*tb));
        } else {
                pos = 0;
                switch (*tz) {
                case '-':
                        break;
                case '+':
                        pos = 1;
                        break;
                default:
                        errx(1, "%s: not a known time zone", tz);
                }

                h = (tz + 1);
                if ((m = strrchr(tz, ':')) != NULL)
                        *(m++) = '\0';

                memcpy(tb, &rdp->rd_date, sizeof(*tb));

                tzone = strtonum(h, -23, 23, &errstr);
                if (errstr)
                        errx(1, "%s: not a known time zone", tz);

                if (pos) {
                        tb->tm_hour += tzone;
                        tb->tm_gmtoff += (tzone * 3600);
                } else {
                        tb->tm_hour -= tzone;
                        tb->tm_gmtoff -= (tzone * 3600);
                }

                if ((tb->tm_hour >= 24) || (tb->tm_hour <= -24))
                        tb->tm_hour = 0;

                if (m != NULL) {
                        tzone = strtonum(m, 0, 59, &errstr);
                        if (errstr)
                                errx(1, "%s: not a known minute", m);

                        if ((tb->tm_min + tzone) >= 60) {
                                tb->tm_hour++;
                                tb->tm_min -= (60 - tzone);
                        } else
                                tb->tm_min += tzone;

                        tb->tm_gmtoff += (tzone*60);
                }
        }
}