/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2014 Gary Mills
 * Copyright 2011, Nexenta Systems, Inc.  All rights reserved.
 * Copyright (c) 1994 Powerdog Industries.  All rights reserved.
 *
 * Copyright (c) 2011 The FreeBSD Foundation
 *
 * Portions of this software were developed by David Chisnall
 * under sponsorship from the FreeBSD Foundation.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY POWERDOG INDUSTRIES ``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 POWERDOG INDUSTRIES 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.
 *
 * The views and conclusions contained in the software and documentation
 * are those of the authors and should not be interpreted as representing
 * official policies, either expressed or implied, of Powerdog Industries.
 */

#include "namespace.h"
#include <time.h>
#include <ctype.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include "private.h"
#include "un-namespace.h"
#include "libc_private.h"
#include "timelocal.h"
#include "tzfile.h"

static char * _strptime(const char *, const char *, struct tm *, int *, locale_t);

#define asizeof(a)      (sizeof(a) / sizeof((a)[0]))

#define FLAG_NONE       (1 << 0)
#define FLAG_YEAR       (1 << 1)
#define FLAG_MONTH      (1 << 2)
#define FLAG_YDAY       (1 << 3)
#define FLAG_MDAY       (1 << 4)
#define FLAG_WDAY       (1 << 5)

/*
 * Gauss's algorithm for the day of the week of the first day of any year
 * in the Gregorian calendar.
 */
static int
first_wday_of(int year)
{
        return ((1 +
            5 * ((year - 1) % 4) +
            4 * ((year - 1) % 100) +
            6 * ((year - 1) % 400)) % 7);
}

static char *
_strptime(const char *buf, const char *fmt, struct tm *tm, int *GMTp,
                locale_t locale)
{
        char    c;
        const char *ptr;
        int     day_offset = -1, wday_offset;
        int week_offset;
        int     i, len;
        int flags;
        int Ealternative, Oalternative;
        int century, year;
        const struct lc_time_T *tptr = __get_current_time_locale(locale);
        static int start_of_month[2][13] = {
                {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},
                {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}
        };

        flags = FLAG_NONE;
        century = -1;
        year = -1;

        ptr = fmt;
        while (*ptr != 0) {
                c = *ptr++;

                if (c != '%') {
                        if (isspace_l((unsigned char)c, locale))
                                while (*buf != 0 && 
                                       isspace_l((unsigned char)*buf, locale))
                                        buf++;
                        else if (c != *buf++)
                                return (NULL);
                        continue;
                }

                Ealternative = 0;
                Oalternative = 0;
label:
                c = *ptr++;
                switch (c) {
                case '%':
                        if (*buf++ != '%')
                                return (NULL);
                        break;

                case '+':
                        buf = _strptime(buf, tptr->date_fmt, tm, GMTp, locale);
                        if (buf == NULL)
                                return (NULL);
                        flags |= FLAG_WDAY | FLAG_MONTH | FLAG_MDAY | FLAG_YEAR;
                        break;

                case 'C':
                        if (!isdigit_l((unsigned char)*buf, locale))
                                return (NULL);

                        /* XXX This will break for 3-digit centuries. */
                        len = 2;
                        for (i = 0; len && *buf != 0 &&
                             isdigit_l((unsigned char)*buf, locale); buf++) {
                                i *= 10;
                                i += *buf - '0';
                                len--;
                        }

                        century = i;
                        flags |= FLAG_YEAR;

                        break;

                case 'c':
                        buf = _strptime(buf, tptr->c_fmt, tm, GMTp, locale);
                        if (buf == NULL)
                                return (NULL);
                        flags |= FLAG_WDAY | FLAG_MONTH | FLAG_MDAY | FLAG_YEAR;
                        break;

                case 'D':
                        buf = _strptime(buf, "%m/%d/%y", tm, GMTp, locale);
                        if (buf == NULL)
                                return (NULL);
                        flags |= FLAG_MONTH | FLAG_MDAY | FLAG_YEAR;
                        break;

                case 'E':
                        if (Ealternative || Oalternative)
                                break;
                        Ealternative++;
                        goto label;

                case 'O':
                        if (Ealternative || Oalternative)
                                break;
                        Oalternative++;
                        goto label;

                case 'F':
                        buf = _strptime(buf, "%Y-%m-%d", tm, GMTp, locale);
                        if (buf == NULL)
                                return (NULL);
                        flags |= FLAG_MONTH | FLAG_MDAY | FLAG_YEAR;
                        break;

                case 'R':
                        buf = _strptime(buf, "%H:%M", tm, GMTp, locale);
                        if (buf == NULL)
                                return (NULL);
                        break;

                case 'r':
                        buf = _strptime(buf, tptr->ampm_fmt, tm, GMTp, locale);
                        if (buf == NULL)
                                return (NULL);
                        break;

                case 'T':
                        buf = _strptime(buf, "%H:%M:%S", tm, GMTp, locale);
                        if (buf == NULL)
                                return (NULL);
                        break;

                case 'X':
                        buf = _strptime(buf, tptr->X_fmt, tm, GMTp, locale);
                        if (buf == NULL)
                                return (NULL);
                        break;

                case 'x':
                        buf = _strptime(buf, tptr->x_fmt, tm, GMTp, locale);
                        if (buf == NULL)
                                return (NULL);
                        flags |= FLAG_MONTH | FLAG_MDAY | FLAG_YEAR;
                        break;

                case 'j':
                        if (!isdigit_l((unsigned char)*buf, locale))
                                return (NULL);

                        len = 3;
                        for (i = 0; len && *buf != 0 &&
                             isdigit_l((unsigned char)*buf, locale); buf++){
                                i *= 10;
                                i += *buf - '0';
                                len--;
                        }
                        if (i < 1 || i > 366)
                                return (NULL);

                        tm->tm_yday = i - 1;
                        flags |= FLAG_YDAY;

                        break;

                case 'M':
                case 'S':
                        if (*buf == 0 ||
                                isspace_l((unsigned char)*buf, locale))
                                break;

                        if (!isdigit_l((unsigned char)*buf, locale))
                                return (NULL);

                        len = 2;
                        for (i = 0; len && *buf != 0 &&
                                isdigit_l((unsigned char)*buf, locale); buf++){
                                i *= 10;
                                i += *buf - '0';
                                len--;
                        }

                        if (c == 'M') {
                                if (i > 59)
                                        return (NULL);
                                tm->tm_min = i;
                        } else {
                                if (i > 60)
                                        return (NULL);
                                tm->tm_sec = i;
                        }

                        break;

                case 'H':
                case 'I':
                case 'k':
                case 'l':
                        /*
                         * %k and %l specifiers are documented as being
                         * blank-padded.  However, there is no harm in
                         * allowing zero-padding.
                         *
                         * XXX %k and %l specifiers may gobble one too many
                         * digits if used incorrectly.
                         */

                        len = 2;
                        if ((c == 'k' || c == 'l') &&
                            isblank_l((unsigned char)*buf, locale)) {
                                buf++;
                                len = 1;
                        }

                        if (!isdigit_l((unsigned char)*buf, locale))
                                return (NULL);

                        for (i = 0; len && *buf != 0 &&
                             isdigit_l((unsigned char)*buf, locale); buf++) {
                                i *= 10;
                                i += *buf - '0';
                                len--;
                        }
                        if (c == 'H' || c == 'k') {
                                if (i > 23)
                                        return (NULL);
                        } else if (i == 0 || i > 12)
                                return (NULL);

                        tm->tm_hour = i;

                        break;

                case 'p':
                        /*
                         * XXX This is bogus if parsed before hour-related
                         * specifiers.
                         */
                        if (tm->tm_hour > 12)
                                return (NULL);

                        len = strlen(tptr->am);
                        if (strncasecmp_l(buf, tptr->am, len, locale) == 0) {
                                if (tm->tm_hour == 12)
                                        tm->tm_hour = 0;
                                buf += len;
                                break;
                        }

                        len = strlen(tptr->pm);
                        if (strncasecmp_l(buf, tptr->pm, len, locale) == 0) {
                                if (tm->tm_hour != 12)
                                        tm->tm_hour += 12;
                                buf += len;
                                break;
                        }

                        return (NULL);

                case 'A':
                case 'a':
                        for (i = 0; i < asizeof(tptr->weekday); i++) {
                                len = strlen(tptr->weekday[i]);
                                if (strncasecmp_l(buf, tptr->weekday[i],
                                                len, locale) == 0)
                                        break;
                                len = strlen(tptr->wday[i]);
                                if (strncasecmp_l(buf, tptr->wday[i],
                                                len, locale) == 0)
                                        break;
                        }
                        if (i == asizeof(tptr->weekday))
                                return (NULL);

                        buf += len;
                        tm->tm_wday = i;
                        flags |= FLAG_WDAY;
                        break;

                case 'U':
                case 'W':
                        /*
                         * XXX This is bogus, as we can not assume any valid
                         * information present in the tm structure at this
                         * point to calculate a real value, so just check the
                         * range for now.
                         */
                        if (!isdigit_l((unsigned char)*buf, locale))
                                return (NULL);

                        len = 2;
                        for (i = 0; len && *buf != 0 &&
                             isdigit_l((unsigned char)*buf, locale); buf++) {
                                i *= 10;
                                i += *buf - '0';
                                len--;
                        }
                        if (i > 53)
                                return (NULL);

                        if (c == 'U')
                                day_offset = TM_SUNDAY;
                        else
                                day_offset = TM_MONDAY;


                        week_offset = i;

                        break;

                case 'u':
                case 'w':
                        if (!isdigit_l((unsigned char)*buf, locale))
                                return (NULL);

                        i = *buf++ - '0';
                        if (i < 0 || i > 7 || (c == 'u' && i < 1) ||
                            (c == 'w' && i > 6))
                                return (NULL);

                        tm->tm_wday = i % 7;
                        flags |= FLAG_WDAY;

                        break;

                case 'e':
                        /*
                         * With %e format, our strftime(3) adds a blank space
                         * before single digits.
                         */
                        if (*buf != 0 &&
                            isspace_l((unsigned char)*buf, locale))
                               buf++;
                        /* FALLTHROUGH */
                case 'd':
                        /*
                         * The %e specifier was once explicitly documented as
                         * not being zero-padded but was later changed to
                         * equivalent to %d.  There is no harm in allowing
                         * such padding.
                         *
                         * XXX The %e specifier may gobble one too many
                         * digits if used incorrectly.
                         */
                        if (!isdigit_l((unsigned char)*buf, locale))
                                return (NULL);

                        len = 2;
                        for (i = 0; len && *buf != 0 &&
                             isdigit_l((unsigned char)*buf, locale); buf++) {
                                i *= 10;
                                i += *buf - '0';
                                len--;
                        }
                        if (i == 0 || i > 31)
                                return (NULL);

                        tm->tm_mday = i;
                        flags |= FLAG_MDAY;

                        break;

                case 'B':
                case 'b':
                case 'h':
                        for (i = 0; i < asizeof(tptr->month); i++) {
                                if (Oalternative) {
                                        if (c == 'B') {
                                                len = strlen(tptr->alt_month[i]);
                                                if (strncasecmp_l(buf,
                                                                tptr->alt_month[i],
                                                                len, locale) == 0)
                                                        break;
                                        }
                                } else {
                                        len = strlen(tptr->month[i]);
                                        if (strncasecmp_l(buf, tptr->month[i],
                                                        len, locale) == 0)
                                                break;
                                }
                        }
                        /*
                         * Try the abbreviated month name if the full name
                         * wasn't found and Oalternative was not requested.
                         */
                        if (i == asizeof(tptr->month) && !Oalternative) {
                                for (i = 0; i < asizeof(tptr->month); i++) {
                                        len = strlen(tptr->mon[i]);
                                        if (strncasecmp_l(buf, tptr->mon[i],
                                                        len, locale) == 0)
                                                break;
                                }
                        }
                        if (i == asizeof(tptr->month))
                                return (NULL);

                        tm->tm_mon = i;
                        buf += len;
                        flags |= FLAG_MONTH;

                        break;

                case 'm':
                        if (!isdigit_l((unsigned char)*buf, locale))
                                return (NULL);

                        len = 2;
                        for (i = 0; len && *buf != 0 &&
                             isdigit_l((unsigned char)*buf, locale); buf++) {
                                i *= 10;
                                i += *buf - '0';
                                len--;
                        }
                        if (i < 1 || i > 12)
                                return (NULL);

                        tm->tm_mon = i - 1;
                        flags |= FLAG_MONTH;

                        break;

                case 's':
                        {
                        char *cp;
                        int sverrno;
                        long n;
                        time_t t;

                        sverrno = errno;
                        errno = 0;
                        n = strtol_l(buf, &cp, 10, locale);
                        if (errno == ERANGE || (long)(t = n) != n) {
                                errno = sverrno;
                                return (NULL);
                        }
                        errno = sverrno;
                        buf = cp;
                        if (gmtime_r(&t, tm) == NULL)
                                return (NULL);
                        *GMTp = 1;
                        flags |= FLAG_YDAY | FLAG_WDAY | FLAG_MONTH |
                            FLAG_MDAY | FLAG_YEAR;
                        }
                        break;

                case 'Y':
                case 'y':
                        if (*buf == 0 ||
                            isspace_l((unsigned char)*buf, locale))
                                break;

                        if (!isdigit_l((unsigned char)*buf, locale))
                                return (NULL);

                        len = (c == 'Y') ? 4 : 2;
                        for (i = 0; len && *buf != 0 &&
                             isdigit_l((unsigned char)*buf, locale); buf++) {
                                i *= 10;
                                i += *buf - '0';
                                len--;
                        }
                        if (c == 'Y')
                                century = i / 100;
                        year = i % 100;

                        flags |= FLAG_YEAR;

                        break;

                case 'Z':
                        {
                        const char *cp;
                        char *zonestr;

                        for (cp = buf; *cp &&
                             isupper_l((unsigned char)*cp, locale); ++cp) {
                                /*empty*/}
                        if (cp - buf) {
                                zonestr = alloca(cp - buf + 1);
                                strncpy(zonestr, buf, cp - buf);
                                zonestr[cp - buf] = '\0';
                                tzset();
                                if (0 == strcmp(zonestr, "GMT") ||
                                    0 == strcmp(zonestr, "UTC") ||
                                    0 == strcmp(zonestr, "Z")) {
                                    *GMTp = 1;
                                } else if (0 == strcmp(zonestr, tzname[0])) {
                                    tm->tm_isdst = 0;
                                } else if (0 == strcmp(zonestr, tzname[1])) {
                                    tm->tm_isdst = 1;
                                } else {
                                    return (NULL);
                                }
                                buf += cp - buf;
                        }
                        }
                        break;

                case 'z':
                        {
                        int sign = 1;

                        if (*buf != '+') {
                                if (*buf == '-')
                                        sign = -1;
                                else
                                        return (NULL);
                        }

                        buf++;
                        i = 0;
                        for (len = 4; len > 0; len--) {
                                if (isdigit_l((unsigned char)*buf, locale)) {
                                        i *= 10;
                                        i += *buf - '0';
                                        buf++;
                                } else if (len == 2) {
                                        i *= 100;
                                        break;
                                } else
                                        return (NULL);
                        }

                        if (i > 1400 || (sign == -1 && i > 1200) ||
                            (i % 100) >= 60)
                                return (NULL);
                        tm->tm_hour -= sign * (i / 100);
                        tm->tm_min  -= sign * (i % 100);
                        *GMTp = 1;
                        }
                        break;

                case 'n':
                case 't':
                        while (isspace_l((unsigned char)*buf, locale))
                                buf++;
                        break;

                default:
                        return (NULL);
                }
        }

        if (century != -1 || year != -1) {
                if (year == -1)
                        year = 0;
                if (century == -1) {
                        if (year < 69)
                                year += 100;
                } else
                        year += century * 100 - TM_YEAR_BASE;
                tm->tm_year = year;
        }

        if (!(flags & FLAG_YDAY) && (flags & FLAG_YEAR)) {
                if ((flags & (FLAG_MONTH | FLAG_MDAY)) ==
                    (FLAG_MONTH | FLAG_MDAY)) {
                        tm->tm_yday = start_of_month[isleap(tm->tm_year +
                            TM_YEAR_BASE)][tm->tm_mon] + (tm->tm_mday - 1);
                        flags |= FLAG_YDAY;
                } else if (day_offset != -1) {
                        int tmpwday, tmpyday, fwo;

                        fwo = first_wday_of(tm->tm_year + TM_YEAR_BASE);
                        /* No incomplete week (week 0). */
                        if (week_offset == 0 && fwo == day_offset)
                                return (NULL);

                        /* Set the date to the first Sunday (or Monday)
                         * of the specified week of the year.
                         */
                        tmpwday = (flags & FLAG_WDAY) ? tm->tm_wday :
                            day_offset;
                        tmpyday = (7 - fwo + day_offset) % 7 +
                            (week_offset - 1) * 7 +
                            (tmpwday - day_offset + 7) % 7;
                        /* Impossible yday for incomplete week (week 0). */
                        if (tmpyday < 0) {
                                if (flags & FLAG_WDAY)
                                        return (NULL);
                                tmpyday = 0;
                        }
                        tm->tm_yday = tmpyday;
                        flags |= FLAG_YDAY;
                }
        }

        if ((flags & (FLAG_YEAR | FLAG_YDAY)) == (FLAG_YEAR | FLAG_YDAY)) {
                if (!(flags & FLAG_MONTH)) {
                        i = 0;
                        while (tm->tm_yday >=
                            start_of_month[isleap(tm->tm_year +
                            TM_YEAR_BASE)][i])
                                i++;
                        if (i > 12) {
                                i = 1;
                                tm->tm_yday -=
                                    start_of_month[isleap(tm->tm_year +
                                    TM_YEAR_BASE)][12];
                                tm->tm_year++;
                        }
                        tm->tm_mon = i - 1;
                        flags |= FLAG_MONTH;
                }
                if (!(flags & FLAG_MDAY)) {
                        tm->tm_mday = tm->tm_yday -
                            start_of_month[isleap(tm->tm_year + TM_YEAR_BASE)]
                            [tm->tm_mon] + 1;
                        flags |= FLAG_MDAY;
                }
                if (!(flags & FLAG_WDAY)) {
                        wday_offset = first_wday_of(tm->tm_year + TM_YEAR_BASE);
                        tm->tm_wday = (wday_offset + tm->tm_yday) % 7;
                        flags |= FLAG_WDAY;
                }
        }

        return ((char *)buf);
}

char *
strptime_l(const char * __restrict buf, const char * __restrict fmt,
    struct tm * __restrict tm, locale_t loc)
{
        char *ret;
        int gmt;
        FIX_LOCALE(loc);

        gmt = 0;
        ret = _strptime(buf, fmt, tm, &gmt, loc);
        if (ret && gmt) {
                time_t t = timegm(tm);

                localtime_r(&t, tm);
        }

        return (ret);
}

char *
strptime(const char * __restrict buf, const char * __restrict fmt,
    struct tm * __restrict tm)
{
        return strptime_l(buf, fmt, tm, __get_locale());
}