/*
 * SPDX-License-Identifier: BSD-4.3TAHOE
 *
 * Copyright (c) 1989 The Regents of the University of California.
 * 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 are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley. The name of the
 * University 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 WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#include "namespace.h"
#include "private.h"

#include "tzfile.h"
#include <fcntl.h>
#include <sys/stat.h>
#include <stdio.h>
#include "un-namespace.h"
#include "timelocal.h"

static char *   _add(const char *, char *, const char *);
static char *   _conv(int, const char *, char *, const char *, locale_t);
static char *   _fmt(const char *, const struct tm *, char *, const char *,
                        int *, locale_t);
static char *   _yconv(int, int, int, int, char *, const char *, locale_t);

extern char *   tzname[];

#ifndef YEAR_2000_NAME
#define YEAR_2000_NAME  "CHECK_STRFTIME_FORMATS_FOR_TWO_DIGIT_YEARS"
#endif /* !defined YEAR_2000_NAME */

#define IN_NONE 0
#define IN_SOME 1
#define IN_THIS 2
#define IN_ALL  3

#define PAD_DEFAULT     0
#define PAD_LESS        1
#define PAD_SPACE       2
#define PAD_ZERO        3

static const char fmt_padding[][4][5] = {
        /* DEFAULT,     LESS,   SPACE,  ZERO */
#define PAD_FMT_MONTHDAY        0
#define PAD_FMT_HMS             0
#define PAD_FMT_CENTURY         0
#define PAD_FMT_SHORTYEAR       0
#define PAD_FMT_MONTH           0
#define PAD_FMT_WEEKOFYEAR      0
#define PAD_FMT_DAYOFMONTH      0
        { "%02d",       "%d",   "%2d",  "%02d" },
#define PAD_FMT_SDAYOFMONTH     1
#define PAD_FMT_SHMS            1
        { "%2d",        "%d",   "%2d",  "%02d" },
#define PAD_FMT_DAYOFYEAR       2
        { "%03d",       "%d",   "%3d",  "%03d" },
#define PAD_FMT_YEAR            3
        { "%04d",       "%d",   "%4d",  "%04d" }
};

size_t
strftime_l(char * __restrict s, size_t maxsize, const char * __restrict format,
    const struct tm * __restrict t, locale_t loc)
{
        char *  p;
        int     warn;
        FIX_LOCALE(loc);

        tzset();
        warn = IN_NONE;
        p = _fmt(((format == NULL) ? "%c" : format), t, s, s + maxsize, &warn, loc);
#ifndef NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU
        if (warn != IN_NONE && getenv(YEAR_2000_NAME) != NULL) {
                (void) fprintf_l(stderr, loc, "\n");
                if (format == NULL)
                        (void) fputs("NULL strftime format ", stderr);
                else    (void) fprintf_l(stderr, loc, "strftime format \"%s\" ",
                                format);
                (void) fputs("yields only two digits of years in ", stderr);
                if (warn == IN_SOME)
                        (void) fputs("some locales", stderr);
                else if (warn == IN_THIS)
                        (void) fputs("the current locale", stderr);
                else    (void) fputs("all locales", stderr);
                (void) fputs("\n", stderr);
        }
#endif /* !defined NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU */
        if (p == s + maxsize)
                return (0);
        *p = '\0';
        return p - s;
}

size_t
strftime(char * __restrict s, size_t maxsize, const char * __restrict format,
    const struct tm * __restrict t)
{
        return strftime_l(s, maxsize, format, t, __get_locale());
}

static char *
_fmt(const char *format, const struct tm * const t, char *pt,
    const char * const ptlim, int *warnp, locale_t loc)
{
        int Ealternative, Oalternative, PadIndex;
        struct lc_time_T *tptr = __get_current_time_locale(loc);

        for ( ; *format; ++format) {
                if (*format == '%') {
                        Ealternative = 0;
                        Oalternative = 0;
                        PadIndex         = PAD_DEFAULT;
label:
                        switch (*++format) {
                        case '\0':
                                --format;
                                break;
                        case 'A':
                                pt = _add((t->tm_wday < 0 ||
                                        t->tm_wday >= DAYSPERWEEK) ?
                                        "?" : tptr->weekday[t->tm_wday],
                                        pt, ptlim);
                                continue;
                        case 'a':
                                pt = _add((t->tm_wday < 0 ||
                                        t->tm_wday >= DAYSPERWEEK) ?
                                        "?" : tptr->wday[t->tm_wday],
                                        pt, ptlim);
                                continue;
                        case 'B':
                                pt = _add((t->tm_mon < 0 ||
                                        t->tm_mon >= MONSPERYEAR) ?
                                        "?" : (Oalternative ? tptr->alt_month :
                                        tptr->month)[t->tm_mon],
                                        pt, ptlim);
                                continue;
                        case 'b':
                        case 'h':
                                pt = _add((t->tm_mon < 0 ||
                                        t->tm_mon >= MONSPERYEAR) ?
                                        "?" : tptr->mon[t->tm_mon],
                                        pt, ptlim);
                                continue;
                        case 'C':
                                /*
                                 * %C used to do a...
                                 *      _fmt("%a %b %e %X %Y", t);
                                 * ...whereas now POSIX 1003.2 calls for
                                 * something completely different.
                                 * (ado, 1993-05-24)
                                 */
                                pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 0,
                                        pt, ptlim, loc);
                                continue;
                        case 'c':
                                {
                                int warn2 = IN_SOME;

                                pt = _fmt(tptr->c_fmt, t, pt, ptlim, &warn2, loc);
                                if (warn2 == IN_ALL)
                                        warn2 = IN_THIS;
                                if (warn2 > *warnp)
                                        *warnp = warn2;
                                }
                                continue;
                        case 'D':
                                pt = _fmt("%m/%d/%y", t, pt, ptlim, warnp, loc);
                                continue;
                        case 'd':
                                pt = _conv(t->tm_mday,
                                        fmt_padding[PAD_FMT_DAYOFMONTH][PadIndex],
                                        pt, ptlim, loc);
                                continue;
                        case 'E':
                                if (Ealternative || Oalternative)
                                        break;
                                Ealternative++;
                                goto label;
                        case 'O':
                                /*
                                 * C99 locale modifiers.
                                 * The sequences
                                 *      %Ec %EC %Ex %EX %Ey %EY
                                 *      %Od %oe %OH %OI %Om %OM
                                 *      %OS %Ou %OU %OV %Ow %OW %Oy
                                 * are supposed to provide alternate
                                 * representations.
                                 *
                                 * FreeBSD extension
                                 *      %OB
                                 */
                                if (Ealternative || Oalternative)
                                        break;
                                Oalternative++;
                                goto label;
                        case 'e':
                                pt = _conv(t->tm_mday,
                                        fmt_padding[PAD_FMT_SDAYOFMONTH][PadIndex],
                                        pt, ptlim, loc);
                                continue;
                        case 'F':
                                pt = _fmt("%Y-%m-%d", t, pt, ptlim, warnp, loc);
                                continue;
                        case 'H':
                                pt = _conv(t->tm_hour, fmt_padding[PAD_FMT_HMS][PadIndex],
                                        pt, ptlim, loc);
                                continue;
                        case 'I':
                                pt = _conv((t->tm_hour % 12) ?
                                        (t->tm_hour % 12) : 12,
                                        fmt_padding[PAD_FMT_HMS][PadIndex],
                                        pt, ptlim, loc);
                                continue;
                        case 'j':
                                pt = _conv(t->tm_yday + 1,
                                        fmt_padding[PAD_FMT_DAYOFYEAR][PadIndex],
                                        pt, ptlim, loc);
                                continue;
                        case 'k':
                                /*
                                 * This used to be...
                                 *      _conv(t->tm_hour % 12 ?
                                 *              t->tm_hour % 12 : 12, 2, ' ');
                                 * ...and has been changed to the below to
                                 * match SunOS 4.1.1 and Arnold Robbins'
                                 * strftime version 3.0. That is, "%k" and
                                 * "%l" have been swapped.
                                 * (ado, 1993-05-24)
                                 */
                                pt = _conv(t->tm_hour, fmt_padding[PAD_FMT_SHMS][PadIndex],
                                        pt, ptlim, loc);
                                continue;
#ifdef KITCHEN_SINK
                        case 'K':
                                /*
                                ** After all this time, still unclaimed!
                                */
                                pt = _add("kitchen sink", pt, ptlim);
                                continue;
#endif /* defined KITCHEN_SINK */
                        case 'l':
                                /*
                                 * This used to be...
                                 *      _conv(t->tm_hour, 2, ' ');
                                 * ...and has been changed to the below to
                                 * match SunOS 4.1.1 and Arnold Robbin's
                                 * strftime version 3.0. That is, "%k" and
                                 * "%l" have been swapped.
                                 * (ado, 1993-05-24)
                                 */
                                pt = _conv((t->tm_hour % 12) ?
                                        (t->tm_hour % 12) : 12,
                                        fmt_padding[PAD_FMT_SHMS][PadIndex],
                                        pt, ptlim, loc);
                                continue;
                        case 'M':
                                pt = _conv(t->tm_min, fmt_padding[PAD_FMT_HMS][PadIndex],
                                        pt, ptlim, loc);
                                continue;
                        case 'm':
                                pt = _conv(t->tm_mon + 1,
                                        fmt_padding[PAD_FMT_MONTH][PadIndex],
                                        pt, ptlim, loc);
                                continue;
                        case 'n':
                                pt = _add("\n", pt, ptlim);
                                continue;
                        case 'p':
                                pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?
                                        tptr->pm : tptr->am,
                                        pt, ptlim);
                                continue;
                        case 'R':
                                pt = _fmt("%H:%M", t, pt, ptlim, warnp, loc);
                                continue;
                        case 'r':
                                pt = _fmt(tptr->ampm_fmt, t, pt, ptlim,
                                        warnp, loc);
                                continue;
                        case 'S':
                                pt = _conv(t->tm_sec, fmt_padding[PAD_FMT_HMS][PadIndex],
                                        pt, ptlim, loc);
                                continue;
                        case 's':
                                {
                                        struct tm       tm;
                                        char            buf[INT_STRLEN_MAXIMUM(
                                                                time_t) + 1];
                                        time_t          mkt;

                                        tm = *t;
                                        mkt = timeoff(&tm, t->tm_gmtoff);
                                        if (TYPE_SIGNED(time_t))
                                                (void) sprintf_l(buf, loc, "%ld",
                                                        (long) mkt);
                                        else    (void) sprintf_l(buf, loc, "%lu",
                                                        (unsigned long) mkt);
                                        pt = _add(buf, pt, ptlim);
                                }
                                continue;
                        case 'T':
                                pt = _fmt("%H:%M:%S", t, pt, ptlim, warnp, loc);
                                continue;
                        case 't':
                                pt = _add("\t", pt, ptlim);
                                continue;
                        case 'U':
                                pt = _conv((t->tm_yday + DAYSPERWEEK -
                                        t->tm_wday) / DAYSPERWEEK,
                                        fmt_padding[PAD_FMT_WEEKOFYEAR][PadIndex],
                                        pt, ptlim, loc);
                                continue;
                        case 'u':
                                /*
                                 * From Arnold Robbins' strftime version 3.0:
                                 * "ISO 8601: Weekday as a decimal number
                                 * [1 (Monday) - 7]"
                                 * (ado, 1993-05-24)
                                 */
                                pt = _conv((t->tm_wday == 0) ?
                                        DAYSPERWEEK : t->tm_wday,
                                        "%d", pt, ptlim, loc);
                                continue;
                        case 'V':       /* ISO 8601 week number */
                        case 'G':       /* ISO 8601 year (four digits) */
                        case 'g':       /* ISO 8601 year (two digits) */
/*
 * From Arnold Robbins' strftime version 3.0: "the week number of the
 * year (the first Monday as the first day of week 1) as a decimal number
 * (01-53)."
 * (ado, 1993-05-24)
 *
 * From "http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html" by Markus Kuhn:
 * "Week 01 of a year is per definition the first week which has the
 * Thursday in this year, which is equivalent to the week which contains
 * the fourth day of January. In other words, the first week of a new year
 * is the week which has the majority of its days in the new year. Week 01
 * might also contain days from the previous year and the week before week
 * 01 of a year is the last week (52 or 53) of the previous year even if
 * it contains days from the new year. A week starts with Monday (day 1)
 * and ends with Sunday (day 7). For example, the first week of the year
 * 1997 lasts from 1996-12-30 to 1997-01-05..."
 * (ado, 1996-01-02)
 */
                                {
                                        int     year;
                                        int     base;
                                        int     yday;
                                        int     wday;
                                        int     w;

                                        year = t->tm_year;
                                        base = TM_YEAR_BASE;
                                        yday = t->tm_yday;
                                        wday = t->tm_wday;
                                        for ( ; ; ) {
                                                int     len;
                                                int     bot;
                                                int     top;

                                                len = isleap_sum(year, base) ?
                                                        DAYSPERLYEAR :
                                                        DAYSPERNYEAR;
                                                /*
                                                 * What yday (-3 ... 3) does
                                                 * the ISO year begin on?
                                                 */
                                                bot = ((yday + 11 - wday) %
                                                        DAYSPERWEEK) - 3;
                                                /*
                                                 * What yday does the NEXT
                                                 * ISO year begin on?
                                                 */
                                                top = bot -
                                                        (len % DAYSPERWEEK);
                                                if (top < -3)
                                                        top += DAYSPERWEEK;
                                                top += len;
                                                if (yday >= top) {
                                                        ++base;
                                                        w = 1;
                                                        break;
                                                }
                                                if (yday >= bot) {
                                                        w = 1 + ((yday - bot) /
                                                                DAYSPERWEEK);
                                                        break;
                                                }
                                                --base;
                                                yday += isleap_sum(year, base) ?
                                                        DAYSPERLYEAR :
                                                        DAYSPERNYEAR;
                                        }
#ifdef XPG4_1994_04_09
                                        if ((w == 52 &&
                                                t->tm_mon == TM_JANUARY) ||
                                                (w == 1 &&
                                                t->tm_mon == TM_DECEMBER))
                                                        w = 53;
#endif /* defined XPG4_1994_04_09 */
                                        if (*format == 'V')
                                                pt = _conv(w, fmt_padding[PAD_FMT_WEEKOFYEAR][PadIndex],
                                                        pt, ptlim, loc);
                                        else if (*format == 'g') {
                                                *warnp = IN_ALL;
                                                pt = _yconv(year, base, 0, 1,
                                                        pt, ptlim, loc);
                                        } else  pt = _yconv(year, base, 1, 1,
                                                        pt, ptlim, loc);
                                }
                                continue;
                        case 'v':
                                /*
                                 * From Arnold Robbins' strftime version 3.0:
                                 * "date as dd-bbb-YYYY"
                                 * (ado, 1993-05-24)
                                 */
                                pt = _fmt("%e-%b-%Y", t, pt, ptlim, warnp, loc);
                                continue;
                        case 'W':
                                pt = _conv((t->tm_yday + DAYSPERWEEK -
                                        (t->tm_wday ?
                                        (t->tm_wday - 1) :
                                        (DAYSPERWEEK - 1))) / DAYSPERWEEK,
                                        fmt_padding[PAD_FMT_WEEKOFYEAR][PadIndex],
                                        pt, ptlim, loc);
                                continue;
                        case 'w':
                                pt = _conv(t->tm_wday, "%d", pt, ptlim, loc);
                                continue;
                        case 'X':
                                pt = _fmt(tptr->X_fmt, t, pt, ptlim, warnp, loc);
                                continue;
                        case 'x':
                                {
                                int     warn2 = IN_SOME;

                                pt = _fmt(tptr->x_fmt, t, pt, ptlim, &warn2, loc);
                                if (warn2 == IN_ALL)
                                        warn2 = IN_THIS;
                                if (warn2 > *warnp)
                                        *warnp = warn2;
                                }
                                continue;
                        case 'y':
                                *warnp = IN_ALL;
                                pt = _yconv(t->tm_year, TM_YEAR_BASE, 0, 1,
                                        pt, ptlim, loc);
                                continue;
                        case 'Y':
                                pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 1,
                                        pt, ptlim, loc);
                                continue;
                        case 'Z':
#ifdef TM_ZONE
                                if (t->TM_ZONE != NULL)
                                        pt = _add(t->TM_ZONE, pt, ptlim);
                                else
#endif /* defined TM_ZONE */
                                if (t->tm_isdst >= 0)
                                        pt = _add(tzname[t->tm_isdst != 0],
                                                pt, ptlim);
                                /*
                                 * C99 says that %Z must be replaced by the
                                 * empty string if the time zone is not
                                 * determinable.
                                 */
                                continue;
                        case 'z':
                                {
                                int             diff;
                                char const *    sign;

                                if (t->tm_isdst < 0)
                                        continue;
#ifdef TM_GMTOFF
                                diff = t->TM_GMTOFF;
#else /* !defined TM_GMTOFF */
                                /*
                                 * C99 says that the UTC offset must
                                 * be computed by looking only at
                                 * tm_isdst. This requirement is
                                 * incorrect, since it means the code
                                 * must rely on magic (in this case
                                 * altzone and timezone), and the
                                 * magic might not have the correct
                                 * offset. Doing things correctly is
                                 * tricky and requires disobeying C99;
                                 * see GNU C strftime for details.
                                 * For now, punt and conform to the
                                 * standard, even though it's incorrect.
                                 *
                                 * C99 says that %z must be replaced by the
                                 * empty string if the time zone is not
                                 * determinable, so output nothing if the
                                 * appropriate variables are not available.
                                 */
                                if (t->tm_isdst == 0)
#ifdef USG_COMPAT
                                        diff = -timezone;
#else /* !defined USG_COMPAT */
                                        continue;
#endif /* !defined USG_COMPAT */
                                else
#ifdef ALTZONE
                                        diff = -altzone;
#else /* !defined ALTZONE */
                                        continue;
#endif /* !defined ALTZONE */
#endif /* !defined TM_GMTOFF */
                                if (diff < 0) {
                                        sign = "-";
                                        diff = -diff;
                                } else
                                        sign = "+";
                                pt = _add(sign, pt, ptlim);
                                diff /= SECSPERMIN;
                                diff = (diff / MINSPERHOUR) * 100 +
                                        (diff % MINSPERHOUR);
                                pt = _conv(diff,
                                        fmt_padding[PAD_FMT_YEAR][PadIndex],
                                        pt, ptlim, loc);
                                }
                                continue;
                        case '+':
                                pt = _fmt(tptr->date_fmt, t, pt, ptlim,
                                        warnp, loc);
                                continue;
                        case '-':
                                if (PadIndex != PAD_DEFAULT)
                                        break;
                                PadIndex = PAD_LESS;
                                goto label;
                        case '_':
                                if (PadIndex != PAD_DEFAULT)
                                        break;
                                PadIndex = PAD_SPACE;
                                goto label;
                        case '0':
                                if (PadIndex != PAD_DEFAULT)
                                        break;
                                PadIndex = PAD_ZERO;
                                goto label;
                        case '%':
                        /*
                         * X311J/88-090 (4.12.3.5): if conversion char is
                         * undefined, behavior is undefined. Print out the
                         * character itself as printf(3) also does.
                         */
                        default:
                                break;
                        }
                }
                if (pt == ptlim)
                        break;
                *pt++ = *format;
        }
        return (pt);
}

static char *
_conv(const int n, const char * const format, char * const pt,
    const char * const ptlim, locale_t  loc)
{
        char    buf[INT_STRLEN_MAXIMUM(int) + 1];

        (void) sprintf_l(buf, loc, format, n);
        return _add(buf, pt, ptlim);
}

static char *
_add(const char *str, char *pt, const char * const ptlim)
{
        while (pt < ptlim && (*pt = *str++) != '\0')
                ++pt;
        return (pt);
}

/*
 * POSIX and the C Standard are unclear or inconsistent about
 * what %C and %y do if the year is negative or exceeds 9999.
 * Use the convention that %C concatenated with %y yields the
 * same output as %Y, and that %Y contains at least 4 bytes,
 * with more only if necessary.
 */

static char *
_yconv(const int a, const int b, const int convert_top, const int convert_yy,
    char *pt, const char * const ptlim, locale_t  loc)
{
        register int    lead;
        register int    trail;

#define DIVISOR 100
        trail = a % DIVISOR + b % DIVISOR;
        lead = a / DIVISOR + b / DIVISOR + trail / DIVISOR;
        trail %= DIVISOR;
        if (trail < 0 && lead > 0) {
                trail += DIVISOR;
                --lead;
        } else if (lead < 0 && trail > 0) {
                trail -= DIVISOR;
                ++lead;
        }
        if (convert_top) {
                if (lead == 0 && trail < 0)
                        pt = _add("-0", pt, ptlim);
                else    pt = _conv(lead, "%02d", pt, ptlim, loc);
        }
        if (convert_yy)
                pt = _conv(((trail < 0) ? -trail : trail), "%02d", pt,
                     ptlim, loc);
        return (pt);
}