/*
 * Copyright 2013 Garrett D'Amore <garrett@damore.org>
 * Copyright 2010 Nexenta Systems, Inc.  All rights reserved.
 * Copyright (c) 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * 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 "lint.h"
#include "tzfile.h"
#include <fcntl.h>
#include <stdint.h>
#include <sys/stat.h>
#include <string.h>
#include <stdio.h>
#include <locale.h>
#include "timelocal.h"
#include "localeimpl.h"

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

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

static const char *fmt_padding[][4] = {
        /* 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" }
};

/*
 * If a caller (such as ascftime) passes in a very large maximum size,
 * the pointer addition here may overflow, wrap around the end of
 * memory, and, if used as-is, would cause subsequent range checks to fail
 * spuriously, resulting in corrupted output even if there is sufficent
 * room in the buffer for the requested format.
 *
 * To prevent this, we replace an overflowed result with the largest
 * possible pointer value.
 */
static char *
_ptlim(char *s, size_t maxsize)
{
        char *e = s + maxsize;

        if (e < s)
                e = (char *)(-sizeof (*e));

        return (e);
}

size_t
strftime_l(char *_RESTRICT_KYWD s, size_t maxsize,
    const char *_RESTRICT_KYWD format, const struct tm *_RESTRICT_KYWD t,
    locale_t loc)
{
        char *p;
        char *e = _ptlim(s, maxsize);

        tzset();
        p = _fmt(loc, ((format == NULL) ? "%c" : format), t, s, e);
        if (p == e)
                return (0);
        *p = '\0';
        return (p - s);
}

size_t
strftime(char *_RESTRICT_KYWD s, size_t maxsize,
    const char *_RESTRICT_KYWD format, const struct tm *_RESTRICT_KYWD t)
{
        return (strftime_l(s, maxsize, format, t, uselocale(NULL)));
}

static char *
_fmt(locale_t loc, const char *format, const struct tm *t, char *pt,
    const char * const ptlim)
{
        int Ealternative, Oalternative, PadIndex;
        const struct lc_time *tptr = loc->time;

#define PADDING(x)      fmt_padding[x][PadIndex]

        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) ?
                                    "?" : (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);
                                continue;
                        case 'c':
                                pt = _fmt(loc, tptr->c_fmt, t, pt, ptlim);
                                continue;
                        case 'D':
                                pt = _fmt(loc, "%m/%d/%y", t, pt, ptlim);
                                continue;
                        case 'd':
                                pt = _conv(t->tm_mday,
                                    PADDING(PAD_FMT_DAYOFMONTH), pt, ptlim);
                                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.
                                 */
                                if (Ealternative || Oalternative)
                                        break;
                                Oalternative++;
                                goto label;
                        case 'e':
                                pt = _conv(t->tm_mday,
                                    PADDING(PAD_FMT_SDAYOFMONTH), pt, ptlim);
                                continue;
                        case 'F':
                                pt = _fmt(loc, "%Y-%m-%d", t, pt, ptlim);
                                continue;
                        case 'H':
                                pt = _conv(t->tm_hour, PADDING(PAD_FMT_HMS),
                                    pt, ptlim);
                                continue;
                        case 'I':
                                pt = _conv((t->tm_hour % 12) ?
                                    (t->tm_hour % 12) : 12,
                                    PADDING(PAD_FMT_HMS), pt, ptlim);
                                continue;
                        case 'j':
                                pt = _conv(t->tm_yday + 1,
                                    PADDING(PAD_FMT_DAYOFYEAR), 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,
                                    PADDING(PAD_FMT_SHMS), 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,
                                    PADDING(PAD_FMT_SHMS), pt, ptlim);
                                continue;
                        case 'M':
                                pt = _conv(t->tm_min, PADDING(PAD_FMT_HMS),
                                    pt, ptlim);
                                continue;
                        case 'm':
                                pt = _conv(t->tm_mon + 1,
                                    PADDING(PAD_FMT_MONTH),
                                    pt, ptlim);
                                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(loc, "%H:%M", t, pt, ptlim);
                                continue;
                        case 'r':
                                pt = _fmt(loc, tptr->ampm_fmt, t, pt, ptlim);
                                continue;
                        case 'S':
                                pt = _conv(t->tm_sec, PADDING(PAD_FMT_HMS),
                                    pt, ptlim);
                                continue;

                        case 's':
                        {
                                struct tm tm;
                                char *buf;

                                tm = *t;
                                (void) asprintf(&buf, "%ld", mktime(&tm));
                                pt = _add(buf, pt, ptlim);
                                continue;
                        }

                        case 'T':
                                pt = _fmt(loc, "%H:%M:%S", t, pt, ptlim);
                                continue;
                        case 't':
                                pt = _add("\t", pt, ptlim);
                                continue;
                        case 'U':
                                pt = _conv((t->tm_yday + DAYSPERWEEK -
                                    t->tm_wday) / DAYSPERWEEK,
                                    PADDING(PAD_FMT_WEEKOFYEAR),
                                    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,
                                            PADDING(PAD_FMT_WEEKOFYEAR),
                                            pt, ptlim);
                                else if (*format == 'g') {
                                        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(loc, "%e-%b-%Y", t, pt, ptlim);
                                continue;
                        case 'W':
                                pt = _conv((t->tm_yday + DAYSPERWEEK -
                                    (t->tm_wday ?
                                    (t->tm_wday - 1) :
                                    (DAYSPERWEEK - 1))) / DAYSPERWEEK,
                                    PADDING(PAD_FMT_WEEKOFYEAR),
                                    pt, ptlim);
                                continue;
                        case 'w':
                                pt = _conv(t->tm_wday, "%d", pt, ptlim);
                                continue;
                        case 'X':
                                pt = _fmt(loc, tptr->X_fmt, t, pt, ptlim);
                                continue;
                        case 'x':
                                pt = _fmt(loc, tptr->x_fmt, t, pt, ptlim);
                                continue;
                        case 'y':
                                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_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;
                                /*
                                 * 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)
                                        diff = -timezone;
                                else
                                        diff = -altzone;
                                if (diff < 0) {
                                        sign = "-";
                                        diff = -diff;
                                } else
                                        sign = "+";
                                pt = _add(sign, pt, ptlim);
                                diff /= SECSPERMIN;
                                diff = (diff / MINSPERHOUR) * 100 +
                                    (diff % MINSPERHOUR);
                                pt = _conv(diff, PADDING(PAD_FMT_YEAR),
                                    pt, ptlim);
                                }
                                continue;
                        case '+':
                                pt = _fmt(loc, tptr->date_fmt, t, pt, ptlim);
                                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 *format, char *const pt,
    const char *const ptlim)
{
        char    buf[12];

        (void) sprintf(buf, 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)
{
        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);
        }
        if (convert_yy)
                pt = _conv(((trail < 0) ? -trail : trail), "%02d", pt, ptlim);
        return (pt);
}