/*  $OpenBSD: strptime.c,v 1.11 2005/08/08 08:05:38 espie Exp $ */
/*  $NetBSD: strptime.c,v 1.12 1998/01/20 21:39:40 mycroft Exp $    */

/*-
 * Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code was contributed to The NetBSD Foundation by Klaus Klein.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *        This product includes software developed by the NetBSD
 *        Foundation, Inc. and its contributors.
 * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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 <sys/localedef.h>
#include <ctype.h>
#include <locale.h>
#include <string.h>
#include <time.h>
#include "tzfile.h"

static const struct {
    const char *abday[7];
    const char *day[7];
    const char *abmon[12];
    const char *mon[12];
    const char *am_pm[2];
    const char *d_t_fmt;
    const char *d_fmt;
    const char *t_fmt;
    const char *t_fmt_ampm;
} _DefaultTimeLocale = {
    {
        "Sun","Mon","Tue","Wed","Thu","Fri","Sat",
    },
    {
        "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday",
        "Friday", "Saturday"
    },
    {
        "Jan", "Feb", "Mar", "Apr", "May", "Jun",
        "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
    },
    {
        "January", "February", "March", "April", "May", "June", "July",
        "August", "September", "October", "November", "December"
    },
    {
        "AM", "PM"
    },
    "%a %b %d %H:%M:%S %Y",
    "%m/%d/%y",
    "%H:%M:%S",
    "%I:%M:%S %p"
};

#define _ctloc(x) (_DefaultTimeLocale.x)

/*
 * We do not implement alternate representations. However, we always
 * check whether a given modifier is allowed for a certain conversion.
 */
#define _ALT_E          0x01
#define _ALT_O          0x02
#define _LEGAL_ALT(x)       { if (alt_format & ~(x)) return (0); }


struct century_relyear {
    int century;
    int relyear;
};
static  int _conv_num(const unsigned char **, int *, int, int);
static  unsigned char *_strptime(const unsigned char *, const char *, struct tm *,
        struct century_relyear *);


char *
strptime(const char *buf, const char *fmt, struct tm *tm)
{
    struct century_relyear cr;
    cr.century = TM_YEAR_BASE;
    cr.relyear = -1;
    return (char*)(_strptime((const unsigned char*)buf, fmt, tm, &cr));
}

static unsigned char *
_strptime(const unsigned char *buf, const char *fmt, struct tm *tm, struct century_relyear *cr)
{
    unsigned char c;
    const unsigned char *bp;
    size_t len = 0;
    int alt_format, i;

    bp = (unsigned char *)buf;
    while ((c = *fmt) != '\0') {
        /* Clear `alternate' modifier prior to new conversion. */
        alt_format = 0;

        /* Eat up white-space. */
        if (isspace(c)) {
            while (isspace(*bp))
                bp++;

            fmt++;
            continue;
        }
                
        if ((c = *fmt++) != '%')
            goto literal;


again:      switch (c = *fmt++) {
        case '%':   /* "%%" is converted to "%". */
literal:
        if (c != *bp++)
            return (NULL);

        break;

        /*
         * "Alternative" modifiers. Just set the appropriate flag
         * and start over again.
         */
        case 'E':   /* "%E?" alternative conversion modifier. */
            _LEGAL_ALT(0);
            alt_format |= _ALT_E;
            goto again;

        case 'O':   /* "%O?" alternative conversion modifier. */
            _LEGAL_ALT(0);
            alt_format |= _ALT_O;
            goto again;
            
        /*
         * "Complex" conversion rules, implemented through recursion.
         */
        case 'c':   /* Date and time, using the locale's format. */
            _LEGAL_ALT(_ALT_E);
            if (!(bp = _strptime(bp, _ctloc(d_t_fmt), tm, cr)))
                return (NULL);
            break;

        case 'D':   /* The date as "%m/%d/%y". */
            _LEGAL_ALT(0);
            if (!(bp = _strptime(bp, "%m/%d/%y", tm, cr)))
                return (NULL);
            break;
    
        case 'R':   /* The time as "%H:%M". */
            _LEGAL_ALT(0);
            if (!(bp = _strptime(bp, "%H:%M", tm, cr)))
                return (NULL);
            break;

        case 'r':   /* The time as "%I:%M:%S %p". */
            _LEGAL_ALT(0);
            if (!(bp = _strptime(bp, "%I:%M:%S %p", tm, cr)))
                return (NULL);
            break;

        case 'T':   /* The time as "%H:%M:%S". */
            _LEGAL_ALT(0);
            if (!(bp = _strptime(bp, "%H:%M:%S", tm, cr)))
                return (NULL);
            break;

        case 'X':   /* The time, using the locale's format. */
            _LEGAL_ALT(_ALT_E);
            if (!(bp = _strptime(bp, _ctloc(t_fmt), tm, cr)))
                return (NULL);
            break;

        case 'x':   /* The date, using the locale's format. */
            _LEGAL_ALT(_ALT_E);
            if (!(bp = _strptime(bp, _ctloc(d_fmt), tm, cr)))
                return (NULL);
            break;

        /*
         * "Elementary" conversion rules.
         */
        case 'A':   /* The day of week, using the locale's form. */
        case 'a':
            _LEGAL_ALT(0);
            for (i = 0; i < 7; i++) {
                /* Full name. */
                len = strlen(_ctloc(day[i]));
                if (strncasecmp(_ctloc(day[i]), (const char*)bp, len) == 0)
                    break;

                /* Abbreviated name. */
                len = strlen(_ctloc(abday[i]));
                if (strncasecmp(_ctloc(abday[i]), (const char*)bp, len) == 0)
                    break;
            }

            /* Nothing matched. */
            if (i == 7)
                return (NULL);

            tm->tm_wday = i;
            bp += len;
            break;

        case 'B':   /* The month, using the locale's form. */
        case 'b':
        case 'h':
            _LEGAL_ALT(0);
            for (i = 0; i < 12; i++) {
                /* Full name. */
                len = strlen(_ctloc(mon[i]));
                if (strncasecmp(_ctloc(mon[i]), (const char*)bp, len) == 0)
                    break;

                /* Abbreviated name. */
                len = strlen(_ctloc(abmon[i]));
                if (strncasecmp(_ctloc(abmon[i]), (const char*)bp, len) == 0)
                    break;
            }

            /* Nothing matched. */
            if (i == 12)
                return (NULL);

            tm->tm_mon = i;
            bp += len;
            break;

        case 'C':   /* The century number. */
            _LEGAL_ALT(_ALT_E);
            if (!(_conv_num(&bp, &i, 0, 99)))
                return (NULL);

            cr->century = i * 100;
            break;

        case 'd':   /* The day of month. */
        case 'e':
            _LEGAL_ALT(_ALT_O);
            if (!(_conv_num(&bp, &tm->tm_mday, 1, 31)))
                return (NULL);
            break;

        case 'k':   /* The hour (24-hour clock representation). */
            _LEGAL_ALT(0);
            /* FALLTHROUGH */
        case 'H':
            _LEGAL_ALT(_ALT_O);
            if (!(_conv_num(&bp, &tm->tm_hour, 0, 23)))
                return (NULL);
            break;

        case 'l':   /* The hour (12-hour clock representation). */
            _LEGAL_ALT(0);
            /* FALLTHROUGH */
        case 'I':
            _LEGAL_ALT(_ALT_O);
            if (!(_conv_num(&bp, &tm->tm_hour, 1, 12)))
                return (NULL);
            break;

        case 'j':   /* The day of year. */
            _LEGAL_ALT(0);
            if (!(_conv_num(&bp, &tm->tm_yday, 1, 366)))
                return (NULL);
            tm->tm_yday--;
            break;

        case 'M':   /* The minute. */
            _LEGAL_ALT(_ALT_O);
            if (!(_conv_num(&bp, &tm->tm_min, 0, 59)))
                return (NULL);
            break;

        case 'm':   /* The month. */
            _LEGAL_ALT(_ALT_O);
            if (!(_conv_num(&bp, &tm->tm_mon, 1, 12)))
                return (NULL);
            tm->tm_mon--;
            break;

        case 'p':   /* The locale's equivalent of AM/PM. */
            _LEGAL_ALT(0);
            /* AM? */
            len = strlen(_ctloc(am_pm[0]));
            if (strncasecmp(_ctloc(am_pm[0]), (const char*)bp, len) == 0) {
                if (tm->tm_hour > 12)   /* i.e., 13:00 AM ?! */
                    return (NULL);
                else if (tm->tm_hour == 12)
                    tm->tm_hour = 0;

                bp += len;
                break;
            }
            /* PM? */
            len = strlen(_ctloc(am_pm[1]));
            if (strncasecmp(_ctloc(am_pm[1]), (const char*)bp, len) == 0) {
                if (tm->tm_hour > 12)   /* i.e., 13:00 PM ?! */
                    return (NULL);
                else if (tm->tm_hour < 12)
                    tm->tm_hour += 12;

                bp += len;
                break;
            }

            /* Nothing matched. */
            return (NULL);

        case 'S':   /* The seconds. */
            _LEGAL_ALT(_ALT_O);
            if (!(_conv_num(&bp, &tm->tm_sec, 0, 61)))
                return (NULL);
            break;

        case 'U':   /* The week of year, beginning on sunday. */
        case 'W':   /* The week of year, beginning on monday. */
            _LEGAL_ALT(_ALT_O);
            /*
             * XXX This is bogus, as we can not assume any valid
             * information present in the tm structure at this
             * point to calculate a real value, so just check the
             * range for now.
             */
             if (!(_conv_num(&bp, &i, 0, 53)))
                return (NULL);
             break;

        case 'w':   /* The day of week, beginning on sunday. */
            _LEGAL_ALT(_ALT_O);
            if (!(_conv_num(&bp, &tm->tm_wday, 0, 6)))
                return (NULL);
            break;

        case 'Y':   /* The year. */
            _LEGAL_ALT(_ALT_E);
            if (!(_conv_num(&bp, &i, 0, 9999)))
                return (NULL);

            cr->relyear = -1;
            tm->tm_year = i - TM_YEAR_BASE;
            break;

        case 'y':   /* The year within the century (2 digits). */
            _LEGAL_ALT(_ALT_E | _ALT_O);
            if (!(_conv_num(&bp, &cr->relyear, 0, 99)))
                return (NULL);
            break;

        /*
         * Miscellaneous conversions.
         */
        case 'n':   /* Any kind of white-space. */
        case 't':
            _LEGAL_ALT(0);
            while (isspace(*bp))
                bp++;
            break;


        default:    /* Unknown/unsupported conversion. */
            return (NULL);
        }


    }

    /*
     * We need to evaluate the two digit year spec (%y)
     * last as we can get a century spec (%C) at any time.
     */
    if (cr->relyear != -1) {
        if (cr->century == TM_YEAR_BASE) {
            if (cr->relyear <= 68)
                tm->tm_year = cr->relyear + 2000 - TM_YEAR_BASE;
            else
                tm->tm_year = cr->relyear + 1900 - TM_YEAR_BASE;
        } else {
            tm->tm_year = cr->relyear + cr->century - TM_YEAR_BASE;
        }
    }

    return (unsigned char*)bp;
}


static int
_conv_num(const unsigned char **buf, int *dest, int llim, int ulim)
{
    int result = 0;
    int rulim = ulim;

    if (**buf < '0' || **buf > '9')
        return (0);

    /* we use rulim to break out of the loop when we run out of digits */
    do {
        result *= 10;
        result += *(*buf)++ - '0';
        rulim /= 10;
    } while ((result * 10 <= ulim) && rulim && **buf >= '0' && **buf <= '9');

    if (result < llim || result > ulim)
        return (0);

    *dest = result;
    return (1);
}