/*      $OpenBSD: wcsftime.c,v 1.7 2019/05/12 12:49:52 schwarze Exp $ */
/*
** Based on the UCB version with the ID appearing below.
** This is ANSIish only when "multibyte character == plain character".
**
** 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 <locale.h>
#include <wchar.h>

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

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

#define Locale  (&C_time_locale)

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

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

        /*
        ** x_fmt
        ** C99 requires this format.
        ** Using just numbers (as here) makes Quakers happier;
        ** it's also compatible with SVR4.
        */
        L"%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.
        */
        L"%a %b %e %T %Y",

        /* am */
        L"AM",

        /* pm */
        L"PM",

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

#define UNKNOWN L"?"
static wchar_t *        _add(const wchar_t *, wchar_t *, const wchar_t *);
static wchar_t *        _sadd(const char *, wchar_t *, const wchar_t *);
static wchar_t *        _conv(int, const wchar_t *, wchar_t *, const wchar_t *);
static wchar_t *        _fmt(const wchar_t *, const struct tm *, wchar_t *, const wchar_t *,
                        int *);
static wchar_t *        _yconv(int, int, int, int, wchar_t *, const wchar_t *);

extern char *   tzname[];

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

size_t
wcsftime(wchar_t *__restrict s, size_t maxsize, 
    const wchar_t *__restrict format, const struct tm *__restrict t)
{
        wchar_t *p;
        int     warn;

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

static wchar_t *
_fmt(const wchar_t *format, const struct tm *t, wchar_t *pt, 
    const wchar_t *ptlim, int *warnp)
{
        for ( ; *format; ++format) {
                if (*format != L'%') {
                        if (pt == ptlim)
                                break;
                        *pt++ = *format;
                        continue;
                }
label:
                switch (*++format) {
                case '\0':
                        --format;
                        break;
                case 'A':
                        pt = _add((t->tm_wday < 0 ||
                                t->tm_wday >= DAYSPERWEEK) ?
                                UNKNOWN : Locale->weekday[t->tm_wday],
                                pt, ptlim);
                        continue;
                case 'a':
                        pt = _add((t->tm_wday < 0 ||
                                t->tm_wday >= DAYSPERWEEK) ?
                                UNKNOWN : Locale->wday[t->tm_wday],
                                pt, ptlim);
                        continue;
                case 'B':
                        pt = _add((t->tm_mon < 0 ||
                                t->tm_mon >= MONSPERYEAR) ?
                                UNKNOWN : Locale->month[t->tm_mon],
                                pt, ptlim);
                        continue;
                case 'b':
                case 'h':
                        pt = _add((t->tm_mon < 0 ||
                                t->tm_mon >= MONSPERYEAR) ?
                                UNKNOWN : 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(L"%m/%d/%y", t, pt, ptlim, warnp);
                        continue;
                case 'd':
                        pt = _conv(t->tm_mday, L"%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, L"%2d", pt, ptlim);
                        continue;
                case 'F':
                        pt = _fmt(L"%Y-%m-%d", t, pt, ptlim, warnp);
                        continue;
                case 'H':
                        pt = _conv(t->tm_hour, L"%02d", pt, ptlim);
                        continue;
                case 'I':
                        pt = _conv((t->tm_hour % 12) ?
                                (t->tm_hour % 12) : 12,
                                L"%02d", pt, ptlim);
                        continue;
                case 'j':
                        pt = _conv(t->tm_yday + 1, L"%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, L"%2d", pt, ptlim);
                        continue;
                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,
                                L"%2d", pt, ptlim);
                        continue;
                case 'M':
                        pt = _conv(t->tm_min, L"%02d", pt, ptlim);
                        continue;
                case 'm':
                        pt = _conv(t->tm_mon + 1, L"%02d", pt, ptlim);
                        continue;
                case 'n':
                        pt = _add(L"\n", pt, ptlim);
                        continue;
                case 'p':
                        pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?
                                Locale->pm :
                                Locale->am,
                                pt, ptlim);
                        continue;
                case 'R':
                        pt = _fmt(L"%H:%M", t, pt, ptlim, warnp);
                        continue;
                case 'r':
                        pt = _fmt(L"%I:%M:%S %p", t, pt, ptlim, warnp);
                        continue;
                case 'S':
                        pt = _conv(t->tm_sec, L"%02d", pt, ptlim);
                        continue;
                case 's':
                        {
                                struct tm       tm;
                                wchar_t         buf[INT_STRLEN_MAXIMUM(
                                                        time_t) + 1];
                                time_t          mkt;

                                tm = *t;
                                mkt = mktime(&tm);
                                (void) swprintf(buf, 
                                    sizeof buf/sizeof buf[0],
                                    L"%ld", (long) mkt);
                                pt = _add(buf, pt, ptlim);
                        }
                        continue;
                case 'T':
                        pt = _fmt(L"%H:%M:%S", t, pt, ptlim, warnp);
                        continue;
                case 't':
                        pt = _add(L"\t", pt, ptlim);
                        continue;
                case 'U':
                        pt = _conv((t->tm_yday + DAYSPERWEEK -
                                t->tm_wday) / DAYSPERWEEK,
                                L"%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,
                                L"%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;
                        }
                        if ((w == 52 && t->tm_mon == TM_JANUARY) ||
                                (w == 1 && t->tm_mon == TM_DECEMBER))
                                        w = 53;
                        if (*format == 'V')
                                pt = _conv(w, L"%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(L"%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,
                                L"%02d", pt, ptlim);
                        continue;
                case 'w':
                        pt = _conv(t->tm_wday, L"%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 = _sadd(t->tm_zone, pt, ptlim);
                        else
                                if (t->tm_isdst >= 0)
                                        pt = _sadd(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;
                        wchar_t const * sign;

                        if (t->tm_isdst < 0)
                                continue;
                        diff = t->tm_gmtoff;
                        if (diff < 0) {
                                sign = L"-";
                                diff = -diff;
                        } else  
                                sign = L"+";
                        pt = _add(sign, pt, ptlim);
                        diff /= SECSPERMIN;
                        diff = (diff / MINSPERHOUR) * 100 +
                                (diff % MINSPERHOUR);
                        pt = _conv(diff, L"%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 wchar_t is
                ** undefined, behavior is undefined. Print out the
                ** character itself as printf(3) also does.
                */
                default:
                        if (pt != ptlim)
                                *pt++ = *format;
                        break;
                }
        }
        return pt;
}

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

        (void) swprintf(buf, sizeof buf/sizeof buf[0], format, n);
        return _add(buf, pt, ptlim);
}

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

static wchar_t *
_sadd(const char *str, wchar_t *pt, const wchar_t *ptlim)
{
        while (pt < ptlim && (*pt = btowc(*str++)) != L'\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 wchar_t *
_yconv(int a, int b, int convert_top, int convert_yy, wchar_t *pt, 
    const wchar_t *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(L"-0", pt, ptlim);
                else    pt = _conv(lead, L"%02d", pt, ptlim);
        }
        if (convert_yy)
                pt = _conv(((trail < 0) ? -trail : trail), L"%02d", pt, ptlim);
        return pt;
}