/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 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/stat.h>
#include <sys/time.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

static void     stime_arg1(const char *, struct timespec *);
static void     stime_arg2(const char *, int, struct timespec *);
static void     stime_darg(const char *, struct timespec *);
static void     stime_file(const char *, struct timespec *);
static int      timeoffset(const char *);
static void     usage(const char *);

int
main(int argc, char *argv[])
{
        struct stat sb;
        struct timespec ts[2];
        int atflag;
        int Aflag, aflag, cflag, mflag, ch, fd, len, rval, timeset;
        char *p;
        char *myname;

        myname = basename(argv[0]);
        Aflag = aflag = cflag = mflag = timeset = 0;
        atflag = 0;
        ts[0].tv_sec = ts[1].tv_sec = 0;
        ts[0].tv_nsec = ts[1].tv_nsec = UTIME_NOW;

        while ((ch = getopt(argc, argv, "A:acd:fhmr:t:")) != -1)
                switch(ch) {
                case 'A':
                        Aflag = timeoffset(optarg);
                        break;
                case 'a':
                        aflag = 1;
                        break;
                case 'c':
                        cflag = 1;
                        break;
                case 'd':
                        timeset = 1;
                        stime_darg(optarg, ts);
                        break;
                case 'f':
                        /* No-op for compatibility. */
                        break;
                case 'h':
                        cflag = 1;
                        atflag = AT_SYMLINK_NOFOLLOW;
                        break;
                case 'm':
                        mflag = 1;
                        break;
                case 'r':
                        timeset = 1;
                        stime_file(optarg, ts);
                        break;
                case 't':
                        timeset = 1;
                        stime_arg1(optarg, ts);
                        break;
                default:
                        usage(myname);
                }
        argc -= optind;
        argv += optind;

        if (aflag == 0 && mflag == 0)
                aflag = mflag = 1;

        if (timeset) {
                if (Aflag) {
                        /*
                         * We're setting the time to an offset from a specified
                         * time.  God knows why, but it means that we can set
                         * that time once and for all here.
                         */
                        if (aflag)
                                ts[0].tv_sec += Aflag;
                        if (mflag)
                                ts[1].tv_sec += Aflag;
                        Aflag = 0;              /* done our job */
                }
        } else {
                /*
                 * If no -r or -t flag, at least two operands, the first of
                 * which is an 8 or 10 digit number, use the obsolete time
                 * specification, otherwise use the current time.
                 */
                if (argc > 1) {
                        strtol(argv[0], &p, 10);
                        len = p - argv[0];
                        if (*p == '\0' && (len == 8 || len == 10)) {
                                timeset = 1;
                                stime_arg2(*argv++, len == 10, ts);
                        }
                }
                /* Both times default to the same. */
                ts[1] = ts[0];
        }

        if (!aflag)
                ts[0].tv_nsec = UTIME_OMIT;
        if (!mflag)
                ts[1].tv_nsec = UTIME_OMIT;

        if (*argv == NULL)
                usage(myname);

        if (Aflag)
                cflag = 1;

        for (rval = 0; *argv; ++argv) {
                /* See if the file exists. */
                if (fstatat(AT_FDCWD, *argv, &sb, atflag) != 0) {
                        if (errno != ENOENT) {
                                rval = 1;
                                warn("%s", *argv);
                                continue;
                        }
                        if (!cflag) {
                                /* Create the file. */
                                fd = open(*argv,
                                    O_WRONLY | O_CREAT, DEFFILEMODE);
                                if (fd < 0 || fstat(fd, &sb) < 0) {
                                        rval = 1;
                                        warn("%s", *argv);
                                        if (fd >= 0)
                                                (void)close(fd);
                                        continue;
                                }
                                (void)close(fd);

                                /* If using the current time, we're done. */
                                if (!timeset)
                                        continue;
                        } else
                                continue;
                }

                /*
                 * We're adjusting the times based on the file times, not a
                 * specified time (that gets handled above).
                 */
                if (Aflag) {
                        if (aflag) {
                                ts[0] = sb.st_atim;
                                ts[0].tv_sec += Aflag;
                        }
                        if (mflag) {
                                ts[1] = sb.st_mtim;
                                ts[1].tv_sec += Aflag;
                        }
                }

                if (!utimensat(AT_FDCWD, *argv, ts, atflag))
                        continue;

                rval = 1;
                warn("%s", *argv);
        }
        exit(rval);
}

#define ATOI2(ar)       ((ar)[0] - '0') * 10 + ((ar)[1] - '0'); (ar) += 2;

static void
stime_arg1(const char *arg, struct timespec *tvp)
{
        time_t now;
        struct tm *t;
        int yearset;
        char *p;

        now = time(NULL);
        if ((t = localtime(&now)) == NULL)
                err(1, "localtime");
                                        /* [[CC]YY]MMDDhhmm[.SS] */
        if ((p = strchr(arg, '.')) == NULL)
                t->tm_sec = 0;          /* Seconds defaults to 0. */
        else {
                if (strlen(p + 1) != 2)
                        goto terr;
                *p++ = '\0';
                t->tm_sec = ATOI2(p);
        }

        yearset = 0;
        switch (strlen(arg)) {
        case 12:                        /* CCYYMMDDhhmm */
                t->tm_year = ATOI2(arg);
                t->tm_year *= 100;
                yearset = 1;
                /* FALLTHROUGH */
        case 10:                        /* YYMMDDhhmm */
                if (yearset) {
                        yearset = ATOI2(arg);
                        t->tm_year += yearset;
                } else {
                        yearset = ATOI2(arg);
                        if (yearset < 69)
                                t->tm_year = yearset + 2000;
                        else
                                t->tm_year = yearset + 1900;
                }
                t->tm_year -= 1900;     /* Convert to UNIX time. */
                /* FALLTHROUGH */
        case 8:                         /* MMDDhhmm */
                t->tm_mon = ATOI2(arg);
                --t->tm_mon;            /* Convert from 01-12 to 00-11 */
                t->tm_mday = ATOI2(arg);
                t->tm_hour = ATOI2(arg);
                t->tm_min = ATOI2(arg);
                break;
        default:
                goto terr;
        }

        t->tm_isdst = -1;               /* Figure out DST. */
        t->tm_yday = -1;
        tvp[0].tv_sec = tvp[1].tv_sec = mktime(t);
        if (t->tm_yday == -1)
                goto terr;

        tvp[0].tv_nsec = tvp[1].tv_nsec = 0;
        return;

terr:
        errx(1, "out of range or illegal time specification: "
            "[[CC]YY]MMDDhhmm[.SS]");
}

static void
stime_arg2(const char *arg, int year, struct timespec *tvp)
{
        time_t now;
        struct tm *t;

        now = time(NULL);
        if ((t = localtime(&now)) == NULL)
                err(1, "localtime");

        t->tm_mon = ATOI2(arg);         /* MMDDhhmm[yy] */
        --t->tm_mon;                    /* Convert from 01-12 to 00-11 */
        t->tm_mday = ATOI2(arg);
        t->tm_hour = ATOI2(arg);
        t->tm_min = ATOI2(arg);
        if (year) {
                t->tm_year = ATOI2(arg);
                if (t->tm_year < 39)    /* support 2000-2038 not 1902-1969 */
                        t->tm_year += 100;
        }

        t->tm_isdst = -1;               /* Figure out DST. */
        t->tm_yday = -1;
        tvp[0].tv_sec = tvp[1].tv_sec = mktime(t);
        if (t->tm_yday == -1)
                errx(1, "out of range or illegal time specification: "
                    "MMDDhhmm[yy]");

        tvp[0].tv_nsec = tvp[1].tv_nsec = 0;
}

static void
stime_darg(const char *arg, struct timespec *tvp)
{
        struct tm t = { .tm_sec = 0 };
        const char *fmt, *colon;
        char *p;
        int val, isutc = 0;

        tvp[0].tv_nsec = 0;
        t.tm_isdst = -1;
        colon = strchr(arg, ':');
        if (colon == NULL || strchr(colon + 1, ':') == NULL)
                goto bad;
        fmt = strchr(arg, 'T') != NULL ? "%Y-%m-%dT%H:%M:%S" :
            "%Y-%m-%d %H:%M:%S";
        p = strptime(arg, fmt, &t);
        if (p == NULL)
                goto bad;
        /* POSIX: must have at least one digit after dot */
        if ((*p == '.' || *p == ',') && isdigit((unsigned char)p[1])) {
                p++;
                val = 100000000;
                while (isdigit((unsigned char)*p)) {
                        tvp[0].tv_nsec += val * (*p - '0');
                        p++;
                        val /= 10;
                }
        }
        if (*p == 'Z') {
                isutc = 1;
                p++;
        }
        if (*p != '\0')
                goto bad;

        t.tm_yday = -1;
        tvp[0].tv_sec = isutc ? timegm(&t) : mktime(&t);
        if (t.tm_yday == -1)
                goto bad;

        tvp[1] = tvp[0];
        return;

bad:
        errx(1, "out of range or illegal time specification: "
            "YYYY-MM-DDThh:mm:SS[.frac][tz]");
}

/* Calculate a time offset in seconds, given an arg of the format [-]HHMMSS. */
int
timeoffset(const char *arg)
{
        int offset;
        int isneg;

        offset = 0;
        isneg = *arg == '-';
        if (isneg)
                arg++;
        switch (strlen(arg)) {
        default:                                /* invalid */
                errx(1, "Invalid offset spec, must be [-][[HH]MM]SS");

        case 6:                                 /* HHMMSS */
                offset = ATOI2(arg);
                /* FALLTHROUGH */
        case 4:                                 /* MMSS */
                offset = offset * 60 + ATOI2(arg);
                /* FALLTHROUGH */
        case 2:                                 /* SS */
                offset = offset * 60 + ATOI2(arg);
        }
        if (isneg)
                return (-offset);
        else
                return (offset);
}

static void
stime_file(const char *fname, struct timespec *tsp)
{
        struct stat sb;

        if (stat(fname, &sb))
                err(1, "%s", fname);
        tsp[0] = sb.st_atim;
        tsp[1] = sb.st_mtim;
}

static void
usage(const char *myname)
{
        fprintf(stderr, "usage: %s [-A [-][[hh]mm]SS] [-achm] [-r file] "
                "[-t [[CC]YY]MMDDhhmm[.SS]]\n"
                "       [-d YYYY-MM-DDThh:mm:SS[.frac][tz]] "
                "file ...\n", myname);
        exit(1);
}