/*      $OpenBSD: strftime.c,v 1.34 2025/05/16 14:24:39 millert Exp $ */
/*
** Copyright (c) 1989, 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 <fcntl.h>
#include <stdio.h>

#include "private.h"
#include "tzfile.h"

struct lc_time_T {
        const char *    mon[MONSPERYEAR];
        const char *    month[MONSPERYEAR];
        const char *    wday[DAYSPERWEEK];
        const char *    weekday[DAYSPERWEEK];
        const char *    X_fmt;
        const char *    x_fmt;
        const char *    c_fmt;
        const char *    am;
        const char *    pm;
        const char *    date_fmt;
};

#define Locale  (&C_time_locale)
static const struct lc_time_T   C_time_locale = {
        {
                "Jan", "Feb", "Mar", "Apr", "May", "Jun",
                "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
        }, {
                "January", "February", "March", "April", "May", "June",
                "July", "August", "September", "October", "November", "December"
        }, {
                "Sun", "Mon", "Tue", "Wed",
                "Thu", "Fri", "Sat"
        }, {
                "Sunday", "Monday", "Tuesday", "Wednesday",
                "Thursday", "Friday", "Saturday"
        },

        /* X_fmt */
        "%H:%M:%S",

        /*
        ** x_fmt
        ** C99 requires this format.
        ** Using just numbers (as here) makes Quakers happier;
        ** it's also compatible with SVR4.
        */
        "%m/%d/%y",

        /*
        ** c_fmt
        ** C99 requires this format.
        ** Previously this code used "%D %X", but we now conform to C99.
        ** Note that
        **      "%a %b %d %H:%M:%S %Y"
        ** is used by Solaris 2.3.
        */
        "%a %b %e %T %Y",

        /* am */
        "AM",

        /* pm */
        "PM",

        /* date_fmt */
        "%a %b %e %H:%M:%S %Z %Y"
};

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

extern char *   tzname[];

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

size_t
strftime(char *s, size_t maxsize, const char *format, const struct tm *t)
{
        char *  p;
        int     warn;

        tzset();
        warn = IN_NONE;
        p = _fmt(((format == NULL) ? "%c" : format), t, s, s + maxsize, &warn);
        if (p == s + maxsize) {
                if (maxsize > 0)
                        s[maxsize - 1] = '\0';
                return 0;
        }
        *p = '\0';
        return p - s;
}
DEF_STRONG(strftime);

static char *
_fmt(const char *format, const struct tm *t, char *pt, const char *ptlim, int *warnp)
{
        for ( ; *format; ++format) {
                if (*format == '%') {
label:
                        switch (*++format) {
                        case '\0':
                                --format;
                                break;
                        case 'A':
                                pt = _add((t->tm_wday < 0 ||
                                        t->tm_wday >= DAYSPERWEEK) ?
                                        "?" : Locale->weekday[t->tm_wday],
                                        pt, ptlim);
                                continue;
                        case 'a':
                                pt = _add((t->tm_wday < 0 ||
                                        t->tm_wday >= DAYSPERWEEK) ?
                                        "?" : Locale->wday[t->tm_wday],
                                        pt, ptlim);
                                continue;
                        case 'B':
                                pt = _add((t->tm_mon < 0 ||
                                        t->tm_mon >= MONSPERYEAR) ?
                                        "?" : Locale->month[t->tm_mon],
                                        pt, ptlim);
                                continue;
                        case 'b':
                        case 'h':
                                pt = _add((t->tm_mon < 0 ||
                                        t->tm_mon >= MONSPERYEAR) ?
                                        "?" : Locale->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);
                                continue;
                        case 'c':
                                {
                                int warn2 = IN_SOME;

                                pt = _fmt(Locale->c_fmt, t, pt, ptlim, &warn2);
                                if (warn2 == IN_ALL)
                                        warn2 = IN_THIS;
                                if (warn2 > *warnp)
                                        *warnp = warn2;
                                }
                                continue;
                        case 'D':
                                pt = _fmt("%m/%d/%y", t, pt, ptlim, warnp);
                                continue;
                        case 'd':
                                pt = _conv(t->tm_mday, "%02d", pt, ptlim);
                                continue;
                        case 'E':
                        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.
                                */
                                goto label;
                        case 'e':
                                pt = _conv(t->tm_mday, "%2d", pt, ptlim);
                                continue;
                        case 'F':
                                pt = _fmt("%Y-%m-%d", t, pt, ptlim, warnp);
                                continue;
                        case 'H':
                                pt = _conv(t->tm_hour, "%02d", pt, ptlim);
                                continue;
                        case 'I':
                                pt = _conv((t->tm_hour % 12) ?
                                        (t->tm_hour % 12) : 12,
                                        "%02d", pt, ptlim);
                                continue;
                        case 'j':
                                pt = _conv(t->tm_yday + 1, "%03d", pt, ptlim);
                                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, "%2d", pt, ptlim);
                                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,
                                        "%2d", pt, ptlim);
                                continue;
                        case 'M':
                                pt = _conv(t->tm_min, "%02d", pt, ptlim);
                                continue;
                        case 'm':
                                pt = _conv(t->tm_mon + 1, "%02d", pt, ptlim);
                                continue;
                        case 'n':
                                pt = _add("\n", pt, ptlim);
                                continue;
                        case 'p':
                                pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?
                                        Locale->pm :
                                        Locale->am,
                                        pt, ptlim);
                                continue;
                        case 'R':
                                pt = _fmt("%H:%M", t, pt, ptlim, warnp);
                                continue;
                        case 'r':
                                pt = _fmt("%I:%M:%S %p", t, pt, ptlim, warnp);
                                continue;
                        case 'S':
                                pt = _conv(t->tm_sec, "%02d", pt, ptlim);
                                continue;
                        case 's':
                                {
                                        struct tm       tm;
                                        char            buf[INT_STRLEN_MAXIMUM(
                                                                time_t) + 1];
                                        time_t          mkt;

                                        tm = *t;
                                        mkt = mktime(&tm);
                                        (void) snprintf(buf, sizeof buf,
                                            "%lld", mkt);
                                        pt = _add(buf, pt, ptlim);
                                }
                                continue;
                        case 'T':
                                pt = _fmt("%H:%M:%S", t, pt, ptlim, warnp);
                                continue;
                        case 't':
                                pt = _add("\t", pt, ptlim);
                                continue;
                        case 'U':
                                pt = _conv((t->tm_yday + DAYSPERWEEK -
                                        t->tm_wday) / DAYSPERWEEK,
                                        "%02d", pt, ptlim);
                                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);
                                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, "%02d",
                                                        pt, ptlim);
                                        else if (*format == 'g') {
                                                *warnp = IN_ALL;
                                                pt = _yconv(year, base, 0, 1,
                                                        pt, ptlim);
                                        } else  pt = _yconv(year, base, 1, 1,
                                                        pt, ptlim);
                                }
                                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);
                                continue;
                        case 'W':
                                pt = _conv((t->tm_yday + DAYSPERWEEK -
                                        (t->tm_wday ?
                                        (t->tm_wday - 1) :
                                        (DAYSPERWEEK - 1))) / DAYSPERWEEK,
                                        "%02d", pt, ptlim);
                                continue;
                        case 'w':
                                pt = _conv(t->tm_wday, "%d", pt, ptlim);
                                continue;
                        case 'X':
                                pt = _fmt(Locale->X_fmt, t, pt, ptlim, warnp);
                                continue;
                        case 'x':
                                {
                                int     warn2 = IN_SOME;

                                pt = _fmt(Locale->x_fmt, t, pt, ptlim, &warn2);
                                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);
                                continue;
                        case 'Y':
                                pt = _yconv(t->tm_year, TM_YEAR_BASE, 1, 1,
                                        pt, ptlim);
                                continue;
                        case 'Z':
                                if (t->tm_zone != NULL)
                                        pt = _add(t->tm_zone, pt, ptlim);
                                else 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;
                                diff = t->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, "%04d", pt, ptlim);
                                }
                                continue;
                        case '+':
                                pt = _fmt(Locale->date_fmt, t, pt, ptlim,
                                        warnp);
                                continue;
                        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(int n, const char *format, char *pt, const char *ptlim)
{
        char    buf[INT_STRLEN_MAXIMUM(int) + 1];

        (void) snprintf(buf, sizeof buf, format, n);
        return _add(buf, pt, ptlim);
}

static char *
_add(const char *str, char *pt, const char *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(int a, int b, int convert_top, int convert_yy, char *pt, const char *ptlim)
{
        int     lead;
        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);
        }
        if (convert_yy)
                pt = _conv(((trail < 0) ? -trail : trail), "%02d", pt, ptlim);
        return pt;
}