/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1985, 1987, 1988, 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/param.h>
#include <sys/time.h>
#include <sys/stat.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <inttypes.h>
#include <locale.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <utmpx.h>

#include "vary.h"

#ifndef TM_YEAR_BASE
#define TM_YEAR_BASE    1900
#endif

static void badformat(void);
static void iso8601_usage(const char *) __dead2;
static void multipleformats(void);
static void printdate(const char *);
static void printisodate(struct tm *, long, long);
static void setthetime(const char *, const char *, int, struct timespec *);
static size_t strftime_ns(char * __restrict, size_t, const char * __restrict,
    const struct tm * __restrict, long, long);
static void usage(void) __dead2;

static const struct iso8601_fmt {
        const char *refname;
        const char *format_string;
} iso8601_fmts[] = {
        { "date", "%Y-%m-%d" },
        { "hours", "T%H" },
        { "minutes", ":%M" },
        { "seconds", ":%S" },
        { "ns", ",%N" },
};
static const struct iso8601_fmt *iso8601_selected;

static const char *rfc2822_format = "%a, %d %b %Y %T %z";

int
main(int argc, char *argv[])
{
        struct timespec ts = { 0, 0 }, tres = { 0, 1 };
        int ch, rflag;
        bool Iflag, jflag, Rflag;
        const char *format;
        char buf[1024];
        char *end, *fmt, *outzone = NULL;
        struct vary *v;
        const struct vary *badv;
        struct tm *lt;
        struct stat sb;
        size_t i;
        intmax_t number;

        v = NULL;
        fmt = NULL;
        (void) setlocale(LC_TIME, "");
        rflag = 0;
        Iflag = jflag = Rflag = 0;
        while ((ch = getopt(argc, argv, "f:I::jnRr:uv:z:")) != -1)
                switch((char)ch) {
                case 'f':
                        fmt = optarg;
                        break;
                case 'I':
                        if (Rflag)
                                multipleformats();
                        Iflag = 1;
                        if (optarg == NULL) {
                                iso8601_selected = iso8601_fmts;
                                break;
                        }
                        for (i = 0; i < nitems(iso8601_fmts); i++)
                                if (strcmp(optarg, iso8601_fmts[i].refname) == 0)
                                        break;
                        if (i == nitems(iso8601_fmts))
                                iso8601_usage(optarg);

                        iso8601_selected = &iso8601_fmts[i];
                        break;
                case 'j':
                        jflag = 1;      /* don't set time */
                        break;
                case 'n':
                        break;
                case 'R':               /* RFC 2822 datetime format */
                        if (Iflag)
                                multipleformats();
                        Rflag = 1;
                        break;
                case 'r':               /* user specified seconds */
                        rflag = 1;
                        number = strtoimax(optarg, &end, 0);
                        if (end > optarg && *end == '\0') {
                                ts.tv_sec = number;
                                ts.tv_nsec = 0;
                        } else if (stat(optarg, &sb) == 0) {
                                ts.tv_sec = sb.st_mtim.tv_sec;
                                ts.tv_nsec = sb.st_mtim.tv_nsec;
                        } else {
                                usage();
                        }
                        break;
                case 'u':               /* do everything in UTC */
                        (void)setenv("TZ", "UTC0", 1);
                        break;
                case 'z':
                        outzone = optarg;
                        break;
                case 'v':
                        v = vary_append(v, optarg);
                        break;
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (!rflag) {
                if (clock_gettime(CLOCK_REALTIME, &ts) == -1)
                        err(1, "clock_gettime");
                if (clock_getres(CLOCK_REALTIME, &tres) == -1)
                        err(1, "clock_getres");
        }

        format = "%+";

        if (Rflag)
                format = rfc2822_format;

        /* allow the operands in any order */
        if (*argv && **argv == '+') {
                if (Iflag)
                        multipleformats();
                format = *argv + 1;
                ++argv;
        }

        if (*argv) {
                setthetime(fmt, *argv, jflag, &ts);
                ++argv;
        } else if (fmt != NULL)
                usage();

        if (*argv && **argv == '+') {
                if (Iflag)
                        multipleformats();
                format = *argv + 1;
        }

        if (outzone != NULL && setenv("TZ", outzone, 1) != 0)
                err(1, "setenv(TZ)");
        lt = localtime(&ts.tv_sec);
        if (lt == NULL)
                errx(1, "invalid time");
        badv = vary_apply(v, lt);
        if (badv) {
                fprintf(stderr, "%s: Cannot apply date adjustment\n",
                    badv->arg);
                vary_destroy(v);
                usage();
        }
        vary_destroy(v);

        if (Iflag)
                printisodate(lt, ts.tv_nsec, tres.tv_nsec);

        if (format == rfc2822_format)
                /*
                 * When using RFC 2822 datetime format, don't honor the
                 * locale.
                 */
                setlocale(LC_TIME, "C");


        (void)strftime_ns(buf, sizeof(buf), format, lt,
            ts.tv_nsec, tres.tv_nsec);
        printdate(buf);
}

static void
printdate(const char *buf)
{
        (void)printf("%s\n", buf);
        if (fflush(stdout))
                err(1, "stdout");
        exit(EXIT_SUCCESS);
}

static void
printisodate(struct tm *lt, long nsec, long res)
{
        const struct iso8601_fmt *it;
        char fmtbuf[64], buf[64], tzbuf[8];

        fmtbuf[0] = 0;
        for (it = iso8601_fmts; it <= iso8601_selected; it++)
                strlcat(fmtbuf, it->format_string, sizeof(fmtbuf));

        (void)strftime_ns(buf, sizeof(buf), fmtbuf, lt, nsec, res);

        if (iso8601_selected > iso8601_fmts) {
                (void)strftime_ns(tzbuf, sizeof(tzbuf), "%z", lt, nsec, res);
                memmove(&tzbuf[4], &tzbuf[3], 3);
                tzbuf[3] = ':';
                strlcat(buf, tzbuf, sizeof(buf));
        }

        printdate(buf);
}

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

static void
setthetime(const char *fmt, const char *p, int jflag, struct timespec *ts)
{
        struct utmpx utx;
        struct tm *lt;
        const char *dot, *t;
        int century;

        lt = localtime(&ts->tv_sec);
        if (lt == NULL)
                errx(1, "invalid time");
        lt->tm_isdst = -1;              /* divine correct DST */

        if (fmt != NULL) {
                t = strptime(p, fmt, lt);
                if (t == NULL) {
                        fprintf(stderr, "Failed conversion of ``%s''"
                                " using format ``%s''\n", p, fmt);
                        badformat();
                } else if (*t != '\0')
                        fprintf(stderr, "Warning: Ignoring %ld extraneous"
                                " characters in date string (%s)\n",
                                (long) strlen(t), t);
        } else {
                for (t = p, dot = NULL; *t; ++t) {
                        if (isdigit(*t))
                                continue;
                        if (*t == '.' && dot == NULL) {
                                dot = t;
                                continue;
                        }
                        badformat();
                }

                if (dot != NULL) {                      /* .ss */
                        dot++; /* *dot++ = '\0'; */
                        if (strlen(dot) != 2)
                                badformat();
                        lt->tm_sec = ATOI2(dot);
                        if (lt->tm_sec > 61)
                                badformat();
                } else
                        lt->tm_sec = 0;

                century = 0;
                /* if p has a ".ss" field then let's pretend it's not there */
                switch (strlen(p) - ((dot != NULL) ? 3 : 0)) {
                case 12:                                /* cc */
                        lt->tm_year = ATOI2(p) * 100 - TM_YEAR_BASE;
                        century = 1;
                        /* FALLTHROUGH */
                case 10:                                /* yy */
                        if (century)
                                lt->tm_year += ATOI2(p);
                        else {
                                lt->tm_year = ATOI2(p);
                                if (lt->tm_year < 69)   /* hack for 2000 ;-} */
                                        lt->tm_year += 2000 - TM_YEAR_BASE;
                                else
                                        lt->tm_year += 1900 - TM_YEAR_BASE;
                        }
                        /* FALLTHROUGH */
                case 8:                                 /* mm */
                        lt->tm_mon = ATOI2(p);
                        if (lt->tm_mon > 12)
                                badformat();
                        --lt->tm_mon;           /* time struct is 0 - 11 */
                        /* FALLTHROUGH */
                case 6:                                 /* dd */
                        lt->tm_mday = ATOI2(p);
                        if (lt->tm_mday > 31)
                                badformat();
                        /* FALLTHROUGH */
                case 4:                                 /* HH */
                        lt->tm_hour = ATOI2(p);
                        if (lt->tm_hour > 23)
                                badformat();
                        /* FALLTHROUGH */
                case 2:                                 /* MM */
                        lt->tm_min = ATOI2(p);
                        if (lt->tm_min > 59)
                                badformat();
                        break;
                default:
                        badformat();
                }
        }

        /* convert broken-down time to GMT clock time */
        lt->tm_yday = -1;
        ts->tv_sec = mktime(lt);
        if (lt->tm_yday == -1)
                errx(1, "nonexistent time");
        ts->tv_nsec = 0;

        if (!jflag) {
                utx.ut_type = OLD_TIME;
                memset(utx.ut_id, 0, sizeof(utx.ut_id));
                (void)gettimeofday(&utx.ut_tv, NULL);
                pututxline(&utx);
                if (clock_settime(CLOCK_REALTIME, ts) != 0)
                        err(1, "clock_settime");
                utx.ut_type = NEW_TIME;
                (void)gettimeofday(&utx.ut_tv, NULL);
                pututxline(&utx);

                if ((p = getlogin()) == NULL)
                        p = "???";
                syslog(LOG_AUTH | LOG_NOTICE, "date set by %s", p);
        }
}

/*
 * The strftime_ns function is a wrapper around strftime(3), which adds support
 * for features absent from strftime(3). Currently, the only extra feature is
 * support for %N, the nanosecond conversion specification.
 *
 * The functions scans the format string for the non-standard conversion
 * specifications and replaces them with the date and time values before
 * passing the format string to strftime(3). The handling of the non-standard
 * conversion specifications happens before the call to strftime(3) to handle
 * cases like "%%N" correctly ("%%N" should yield "%N" instead of nanoseconds).
 */
static size_t
strftime_ns(char * __restrict s, size_t maxsize, const char * __restrict format,
    const struct tm * __restrict t, long nsec, long res)
{
        size_t ret;
        char *newformat;
        char *oldformat;
        const char *prefix;
        const char *suffix;
        const char *tok;
        long number;
        int i, len, prefixlen, width, zeroes;
        bool seen_percent, seen_dash, seen_width;

        seen_percent = false;
        if ((newformat = strdup(format)) == NULL)
                err(1, "strdup");
        tok = newformat;
        for (tok = newformat; *tok != '\0'; tok++) {
                switch (*tok) {
                case '%':
                        /*
                         * If the previous token was a percent sign,
                         * then there are two percent tokens in a row.
                         */
                        if (seen_percent) {
                                seen_percent = false;
                        } else {
                                seen_percent = true;
                                seen_dash = seen_width = false;
                                prefixlen = tok - newformat;
                                width = 0;
                        }
                        break;
                case 'N':
                        if (!seen_percent)
                                break;
                        oldformat = newformat;
                        prefix = oldformat;
                        suffix = tok + 1;
                        /*
                         * Prepare the number we are about to print.  If
                         * the requested width is less than 9, we need to
                         * cut off the least significant digits.  If it is
                         * more than 9, we will have to append zeroes.
                         */
                        if (seen_dash) {
                                /*
                                 * Calculate number of singificant digits
                                 * based on res which is the clock's
                                 * resolution in nanoseconds.
                                 */
                                for (width = 9, number = res;
                                     width > 0 && number > 0;
                                     width--, number /= 10)
                                        /* nothing */;
                        }
                        number = nsec;
                        zeroes = 0;
                        if (width == 0) {
                                width = 9;
                        } else if (width > 9) {
                                zeroes = width - 9;
                                width = 9;
                        } else {
                                for (i = 0; i < 9 - width; i++)
                                        number /= 10;
                        }
                        /*
                         * Construct a new format string from the prefix
                         * (i.e., the part of the old format from its
                         * beginning to the currently handled "%N"
                         * conversion specification), the nanoseconds, and
                         * the suffix (i.e., the part of the old format
                         * from the next token to the end).
                         */
                        asprintf(&newformat, "%.*s%.*ld%.*d%n%s", prefixlen,
                            prefix, width, number, zeroes, 0, &len, suffix);
                        if (newformat == NULL)
                                err(1, "asprintf");
                        free(oldformat);
                        tok = newformat + len - 1;
                        seen_percent = false;
                        break;
                case '-':
                        if (seen_percent) {
                                if (seen_dash || seen_width) {
                                        seen_percent = false;
                                        break;
                                }
                                seen_dash = true;
                        }
                        break;
                case '0': case '1': case '2': case '3': case '4':
                case '5': case '6': case '7': case '8': case '9':
                        if (seen_percent) {
                                if (seen_dash) {
                                        seen_percent = false;
                                        break;
                                }
                                width = width * 10 + *tok - '0';
                                seen_width = true;
                        }
                        break;
                default:
                        seen_percent = false;
                        break;
                }
        }

        ret = strftime(s, maxsize, newformat, t);
        free(newformat);
        return (ret);
}

static void
badformat(void)
{
        warnx("illegal time format");
        usage();
}

static void
iso8601_usage(const char *badarg)
{
        errx(1, "invalid argument '%s' for -I", badarg);
}

static void
multipleformats(void)
{
        errx(1, "multiple output formats specified");
}

static void
usage(void)
{
        (void)fprintf(stderr, "%s\n%s\n%s\n",
            "usage: date [-jnRu] [-I[date|hours|minutes|seconds|ns]] [-f input_fmt]",
            "            "
            "[ -z output_zone ] [-r filename|seconds] [-v[+|-]val[y|m|w|d|H|M|S]]",
            "            "
            "[[[[[[cc]yy]mm]dd]HH]MM[.SS] | new_date] [+output_fmt]"
            );
        exit(1);
}