/*
 * Approxidate, taken from git.
 *
 * Copyright (C) Linus Torvalds, 2005
 */

#include "approxidate.h"

#include <math.h>
#include <string.h>
#include <time.h>
#include <limits.h>
#include <stdlib.h>

/**
 * Maintains compatibility with the default struct tm,
 * but adds a field for usec.
 */
struct atm
{
    int tm_sec;
    int tm_min;
    int tm_hour;
    int tm_mday;
    int tm_mon;
    int tm_year;
    int tm_wday;
    int tm_yday;
    int tm_isdst;
    long tm_usec;
};

#define GIT_SPACE 0x01
#define GIT_DIGIT 0x02
#define GIT_ALPHA 0x04
#define GIT_GLOB_SPECIAL 0x08
#define GIT_REGEX_SPECIAL 0x10
#define GIT_PATHSPEC_MAGIC 0x20
#define GIT_CNTRL 0x40
#define GIT_PUNCT 0x80
#define sane_istest(x,mask) ((sane_ctype[(unsigned char)(x)] & (mask)) != 0)
#define isdigit(x) sane_istest(x,GIT_DIGIT)
#define isalpha(x) sane_istest(x,GIT_ALPHA)
#define isalnum(x) sane_istest(x,GIT_ALPHA | GIT_DIGIT)
#define toupper(x) sane_case((unsigned char)(x), 0)
#define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))

enum
{
    S = GIT_SPACE,
    A = GIT_ALPHA,
    D = GIT_DIGIT,
    G = GIT_GLOB_SPECIAL,	/* *, ?, [, \\ */
    R = GIT_REGEX_SPECIAL,	/* $, (, ), +, ., ^, {, | */
    P = GIT_PATHSPEC_MAGIC, /* other non-alnum, except for ] and } */
    X = GIT_CNTRL,
    U = GIT_PUNCT,
    Z = GIT_CNTRL | GIT_SPACE
};

const unsigned char sane_ctype[256] =
{
    X, X, X, X, X, X, X, X, X, Z, Z, X, X, Z, X, X,		/*   0.. 15 */
    X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,		/*  16.. 31 */
    S, P, P, P, R, P, P, P, R, R, G, R, P, P, R, P,		/*  32.. 47 */
    D, D, D, D, D, D, D, D, D, D, P, P, P, P, P, G,		/*  48.. 63 */
    P, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A,		/*  64.. 79 */
    A, A, A, A, A, A, A, A, A, A, A, G, G, U, R, P,		/*  80.. 95 */
    P, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A,		/*  96..111 */
    A, A, A, A, A, A, A, A, A, A, A, R, R, U, P, X,		/* 112..127 */
    /* Nothing in the 128.. range */
};

static inline int sane_case(int x, int high)
{
    if (sane_istest(x, GIT_ALPHA))
        x = (x & ~0x20) | high;

    return x;
}

/*
 * This is like mktime, but without normalization of tm_wday and tm_yday.
 */
static time_t tm_to_time_t(const struct atm *tm)
{
    static const int mdays[] =
    {
        0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
    };
    int year = tm->tm_year - 70;
    int month = tm->tm_mon;
    int day = tm->tm_mday;

    if (year < 0 || year > 129) /* algo only works for 1970-2099 */
        return -1;

    if (month < 0 || month > 11) /* array bounds */
        return -1;

    if (month < 2 || (year + 2) % 4)
        day--;

    if (tm->tm_hour < 0 || tm->tm_min < 0 || tm->tm_sec < 0)
        return -1;

    return (year * 365 + (year + 1) / 4 + mdays[month] + day) * 24 * 60 * 60UL +
           tm->tm_hour * 60 * 60 + tm->tm_min * 60 + tm->tm_sec;
}

static const char *month_names[] =
{
    "January", "February", "March", "April", "May", "June",
    "July", "August", "September", "October", "November", "December"
};

static const char *weekday_names[] =
{
    "Sundays", "Mondays", "Tuesdays", "Wednesdays", "Thursdays", "Fridays", "Saturdays"
};

/*
 * Check these. And note how it doesn't do the summer-time conversion.
 *
 * In my world, it's always summer, and things are probably a bit off
 * in other ways too.
 */
static const struct
{
    const char *name;
    int offset;
    int dst;
} timezone_names[] =
{
    { "IDLW", -12, 0, },	/* International Date Line West */
    { "NT",   -11, 0, },	/* Nome */
    { "CAT",  -10, 0, },	/* Central Alaska */
    { "HST",  -10, 0, },	/* Hawaii Standard */
    { "HDT",  -10, 1, },	/* Hawaii Daylight */
    { "YST",   -9, 0, },	/* Yukon Standard */
    { "YDT",   -9, 1, },	/* Yukon Daylight */
    { "PST",   -8, 0, },	/* Pacific Standard */
    { "PDT",   -8, 1, },	/* Pacific Daylight */
    { "MST",   -7, 0, },	/* Mountain Standard */
    { "MDT",   -7, 1, },	/* Mountain Daylight */
    { "CST",   -6, 0, },	/* Central Standard */
    { "CDT",   -6, 1, },	/* Central Daylight */
    { "EST",   -5, 0, },	/* Eastern Standard */
    { "EDT",   -5, 1, },	/* Eastern Daylight */
    { "AST",   -3, 0, },	/* Atlantic Standard */
    { "ADT",   -3, 1, },	/* Atlantic Daylight */
    { "WAT",   -1, 0, },	/* West Africa */

    { "GMT",    0, 0, },	/* Greenwich Mean */
    { "UTC",    0, 0, },	/* Universal (Coordinated) */
    { "Z",      0, 0, },    /* Zulu, alias for UTC */

    { "WET",    0, 0, },	/* Western European */
    { "BST",    0, 1, },	/* British Summer */
    { "CET",   +1, 0, },	/* Central European */
    { "MET",   +1, 0, },	/* Middle European */
    { "MEWT",  +1, 0, },	/* Middle European Winter */
    { "MEST",  +1, 1, },	/* Middle European Summer */
    { "CEST",  +1, 1, },	/* Central European Summer */
    { "MESZ",  +1, 1, },	/* Middle European Summer */
    { "FWT",   +1, 0, },	/* French Winter */
    { "FST",   +1, 1, },	/* French Summer */
    { "EET",   +2, 0, },	/* Eastern Europe, USSR Zone 1 */
    { "EEST",  +2, 1, },	/* Eastern European Daylight */
    { "WAST",  +7, 0, },	/* West Australian Standard */
    { "WADT",  +7, 1, },	/* West Australian Daylight */
    { "CCT",   +8, 0, },	/* China Coast, USSR Zone 7 */
    { "JST",   +9, 0, },	/* Japan Standard, USSR Zone 8 */
    { "EAST", +10, 0, },	/* Eastern Australian Standard */
    { "EADT", +10, 1, },	/* Eastern Australian Daylight */
    { "GST",  +10, 0, },	/* Guam Standard, USSR Zone 9 */
    { "NZT",  +12, 0, },	/* New Zealand */
    { "NZST", +12, 0, },	/* New Zealand Standard */
    { "NZDT", +12, 1, },	/* New Zealand Daylight */
    { "IDLE", +12, 0, },	/* International Date Line East */
};

static int match_string(const char *date, const char *str)
{
    int i = 0;

    for (i = 0; *date; date++, str++, i++)
    {
        if (*date == *str)
            continue;

        if (toupper(*date) == toupper(*str))
            continue;

        if (!isalnum(*date))
            break;

        return 0;
    }

    return i;
}

static int skip_alpha(const char *date)
{
    int i = 0;

    do
    {
        i++;
    }
    while (isalpha(date[i]));

    return i;
}

/*
* Parse month, weekday, or timezone name
*/
static int match_alpha(const char *date, struct atm *tm, int *offset)
{
    int i;

    for (i = 0; i < 12; i++)
    {
        int match = match_string(date, month_names[i]);

        if (match >= 3)
        {
            tm->tm_mon = i;
            return match;
        }
    }

    for (i = 0; i < 7; i++)
    {
        int match = match_string(date, weekday_names[i]);

        if (match >= 3)
        {
            tm->tm_wday = i;
            return match;
        }
    }

    for (i = 0; i < (int)ARRAY_SIZE(timezone_names); i++)
    {
        int match = match_string(date, timezone_names[i].name);

        if (match >= 3 || match == (int)strlen(timezone_names[i].name))
        {
            int off = timezone_names[i].offset;

            /* This is bogus, but we like summer */
            off += timezone_names[i].dst;

            /* Only use the tz name offset if we don't have anything better */
            if (*offset == -1)
                *offset = 60 * off;

            return match;
        }
    }

    if (match_string(date, "PM") == 2)
    {
        tm->tm_hour = (tm->tm_hour % 12) + 12;
        return 2;
    }

    if (match_string(date, "AM") == 2)
    {
        tm->tm_hour = (tm->tm_hour % 12) + 0;
        return 2;
    }

    /* BAD CRAP */
    return skip_alpha(date);
}

static int is_date(int year, int month, int day, struct atm *now_tm, time_t now, struct atm *tm)
{
    if (month > 0 && month < 13 && day > 0 && day < 32)
    {
        struct atm check = *tm;
        struct atm *r = (now_tm ? &check : tm);

        r->tm_mon = month - 1;
        r->tm_mday = day;

        if (year == -1)
        {
            if (!now_tm)
                return 1;

            r->tm_year = now_tm->tm_year;
        }
        else if (year >= 1970 && year < 2100)
            r->tm_year = year - 1900;
        else if (year > 70 && year < 100)
            r->tm_year = year;
        else if (year < 38)
            r->tm_year = year + 100;
        else
            return 0;

        if (!now_tm)
            return 1;

        tm->tm_mon = r->tm_mon;
        tm->tm_mday = r->tm_mday;

        if (year != -1)
            tm->tm_year = r->tm_year;

        return 1;
    }

    return 0;
}

static int match_multi_number(unsigned long num, char c, const char *date,
                              char *end, struct atm *tm, time_t now)
{
    long num2, num3, num4;

    num2 = strtol(end + 1, &end, 10);
    num3 = -1;
    num4 = 0;

    if (*end == c && isdigit(end[1]))
    {
        num3 = strtol(end + 1, &end, 10);

        if (*end == '.')
        {
            char *start = end + 1;
            num4 = strtol(end + 1, &end, 10);

            if ((end - start) < 6)
            {
                num4 *= (long)pow(10, 6 - (end - start));
            }
        }
    }


    /* Time? Date? */
    switch (c)
    {
    case ':':
        if (num3 < 0)
            num3 = 0;

        if (num < 25 && num2 >= 0 && num2 < 60 && num3 >= 0 && num3 <= 60)
        {
            tm->tm_hour = num;
            tm->tm_min = num2;
            tm->tm_sec = num3;
            tm->tm_usec = num4;
            break;
        }

        return 0;

    case '-':
    case '/':
    case '.':
        if (!now)
            now = time(NULL);

        if (num > 70)
        {
            /* yyyy-mm-dd? */
            if (is_date(num, num2, num3, NULL, now, tm))
                break;

            /* yyyy-dd-mm? */
            if (is_date(num, num3, num2, NULL, now, tm))
                break;
        }

        /* Our eastern European friends say dd.mm.yy[yy]
         * is the norm there, so giving precedence to
         * mm/dd/yy[yy] form only when separator is not '.'
         */
        if (c != '.' &&
                is_date(num3, num, num2, NULL, now, tm))
            break;

        /* European dd.mm.yy[yy] or funny US dd/mm/yy[yy] */
        if (is_date(num3, num2, num, NULL, now, tm))
            break;

        /* Funny European mm.dd.yy */
        if (c == '.' &&
                is_date(num3, num, num2, NULL, now, tm))
            break;

        return 0;
    }

    return end - date;
}

/*
 * Have we filled in any part of the time/date yet?
 * We just do a binary 'and' to see if the sign bit
 * is set in all the values.
 */
static inline int nodate(struct tm *tm)
{
    return (tm->tm_year &
            tm->tm_mon &
            tm->tm_mday &
            tm->tm_hour &
            tm->tm_min &
            tm->tm_sec) < 0;
}

/*
 * We've seen a digit. Time? Year? Date?
 */
static int match_digit(const char *date, struct atm *tm, int *offset, int *tm_gmt)
{
    int n;
    char *end;
    unsigned long num;

    num = strtoul(date, &end, 10);

    /*
     * Seconds since 1970? We trigger on that for any numbers with
     * more than 8 digits. This is because we don't want to rule out
     * numbers like 20070606 as a YYYYMMDD date.
     */
    if (num >= 100000000 && nodate((struct tm*)tm))
    {
        time_t time = num;

        if (gmtime_r(&time, (struct tm*)tm))
        {
            *tm_gmt = 1;
            return end - date;
        }
    }

    /*
     * Check for special formats: num[-.:/]num[same]num[.secfracs]
     */
    switch (*end)
    {
    case ':':
    case '.':
    case '/':
    case '-':
        if (isdigit(end[1]))
        {
            int match = match_multi_number(num, *end, date, end, tm, 0);

            if (match)
                return match;
        }
    }

    /*
     * None of the special formats? Try to guess what
     * the number meant. We use the number of digits
     * to make a more educated guess..
     */
    n = 0;

    do
    {
        n++;
    }
    while (isdigit(date[n]));

    /* Four-digit year or a timezone? */
    if (n == 4)
    {
        if (num <= 1400 && *offset == -1)
        {
            unsigned int minutes = num % 100;
            unsigned int hours = num / 100;
            *offset = hours * 60 + minutes;
        }
        else if (num > 1900 && num < 2100)
            tm->tm_year = num - 1900;

        return n;
    }

    /*
     * Ignore lots of numerals. We took care of 4-digit years above.
     * Days or months must be one or two digits.
     */
    if (n > 2)
        return n;

    /*
     * NOTE! We will give precedence to day-of-month over month or
     * year numbers in the 1-12 range. So 05 is always "mday 5",
     * unless we already have a mday..
     *
     * IOW, 01 Apr 05 parses as "April 1st, 2005".
     */
    if (num > 0 && num < 32 && tm->tm_mday < 0)
    {
        tm->tm_mday = num;
        return n;
    }

    /* Two-digit year? */
    if (n == 2 && tm->tm_year < 0)
    {
        if (num < 10 && tm->tm_mday >= 0)
        {
            tm->tm_year = num + 100;
            return n;
        }

        if (num >= 70)
        {
            tm->tm_year = num;
            return n;
        }
    }

    if (num > 0 && num < 13 && tm->tm_mon < 0)
        tm->tm_mon = num - 1;

    return n;
}

static int match_tz(const char *date, int *offp)
{
    char *end;
    int hour = strtoul(date + 1, &end, 10);
    int n = end - (date + 1);
    int min = 0;

    if (n == 4)
    {
        /* hhmm */
        min = hour % 100;
        hour = hour / 100;
    }
    else if (n != 2)
    {
        min = 99; /* random crap */
    }
    else if (*end == ':')
    {
        /* hh:mm? */
        min = strtoul(end + 1, &end, 10);

        if (end - (date + 1) != 5)
            min = 99; /* random crap */
    } /* otherwise we parsed "hh" */

    /*
     * Don't accept any random crap. Even though some places have
     * offset larger than 12 hours (e.g. Pacific/Kiritimati is at
     * UTC+14), there is something wrong if hour part is much
     * larger than that. We might also want to check that the
     * minutes are divisible by 15 or something too. (Offset of
     * Kathmandu, Nepal is UTC+5:45)
     */
    if (min < 60 && hour < 24)
    {
        int offset = hour * 60 + min;

        if (*date == '-')
            offset = -offset;

        *offp = offset;
    }

    return end - date;
}

/*
 * Parse a string like "0 +0000" as ancient timestamp near epoch, but
 * only when it appears not as part of any other string.
 */
static int match_object_header_date(const char *date, struct timeval *tv, int *offset)
{
    char *end;
    unsigned long stamp;
    int ofs;

    if (*date < '0' || '9' < *date)
        return -1;

    stamp = strtoul(date, &end, 10);

    if (*end != ' ' || stamp == ULONG_MAX || (end[1] != '+' && end[1] != '-'))
        return -1;

    date = end + 2;
    ofs = strtol(date, &end, 10);

    if ((*end != '\0' && (*end != '\n')) || end != date + 4)
        return -1;

    ofs = (ofs / 100) * 60 + (ofs % 100);

    if (date[-1] == '-')
        ofs = -ofs;

    tv->tv_sec = stamp;
    *offset = ofs;
    return 0;
}

/* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
   (i.e. English) day/month names, and it doesn't work correctly with %z. */
int parse_date_basic(const char *date, struct timeval *tv, int *offset)
{
    struct atm tm;
    int tm_gmt;
    int dummy_offset;

    if (!offset)
        offset = &dummy_offset;

    memset(&tm, 0, sizeof(tm));
    tm.tm_year = -1;
    tm.tm_mon = -1;
    tm.tm_mday = -1;
    tm.tm_isdst = -1;
    tm.tm_hour = -1;
    tm.tm_min = -1;
    tm.tm_sec = -1;
    tm.tm_usec = 0;
    *offset = -1;
    tm_gmt = 0;

    if (*date == '@' &&
            !match_object_header_date(date + 1, tv, offset))
        return 0; /* success */

    for (;;)
    {
        int match = 0;
        unsigned char c = *date;

        /* Stop at end of string or newline */
        if (!c || c == '\n')
            break;

        if (isalpha(c))
            match = match_alpha(date, &tm, offset);
        else if (isdigit(c))
            match = match_digit(date, &tm, offset, &tm_gmt);
        else if ((c == '-' || c == '+') && isdigit(date[1]))
            match = match_tz(date, offset);

        if (!match)
        {
            /* BAD CRAP */
            match = 1;
        }

        date += match;
    }

    tv->tv_usec = tm.tm_usec;

    /* mktime uses local timezone */
    tv->tv_sec = tm_to_time_t(&tm);

    if (*offset == -1)
    {
        time_t temp_time = mktime((struct tm*)&tm);

        if (tv->tv_sec > temp_time)
        {
            *offset = (tv->tv_sec - temp_time) / 60;
        }
        else
        {
            *offset = -(int)((temp_time - tv->tv_sec) / 60);
        }
    }

    if (*offset == -1)
        *offset = (((time_t)tv->tv_sec) - mktime((struct tm*)&tm)) / 60;

    if (tv->tv_sec == -1)
        return -1;

    if (!tm_gmt)
        tv->tv_sec -= *offset * 60;

    return 0; /* success */
}

/*
 * Relative time update (eg "2 days ago").  If we haven't set the time
 * yet, we need to set it from current time.
 */
static unsigned long update_tm(struct atm *tm, struct atm *now, unsigned long sec)
{
    time_t n;

    if (tm->tm_mday < 0)
        tm->tm_mday = now->tm_mday;

    if (tm->tm_mon < 0)
        tm->tm_mon = now->tm_mon;

    if (tm->tm_year < 0)
    {
        tm->tm_year = now->tm_year;

        if (tm->tm_mon > now->tm_mon)
            tm->tm_year--;
    }

    n = mktime((struct tm*)tm) - sec;
    localtime_r(&n, (struct tm*)tm);
    return n;
}

static void date_now(struct atm *tm, struct atm *now, int *num)
{
    update_tm(tm, now, 0);
}

static void date_yesterday(struct atm *tm, struct atm *now, int *num)
{
    update_tm(tm, now, 24 * 60 * 60);
}

static void date_time(struct atm *tm, struct atm *now, int hour)
{
    if (tm->tm_hour < hour)
        date_yesterday(tm, now, NULL);

    tm->tm_hour = hour;
    tm->tm_min = 0;
    tm->tm_sec = 0;
}

static void date_midnight(struct atm *tm, struct atm *now, int *num)
{
    date_time(tm, now, 0);
}

static void date_noon(struct atm *tm, struct atm *now, int *num)
{
    date_time(tm, now, 12);
}

static void date_tea(struct atm *tm, struct atm *now, int *num)
{
    date_time(tm, now, 17);
}

static void date_pm(struct atm *tm, struct atm *now, int *num)
{
    int hour, n = *num;
    *num = 0;

    hour = tm->tm_hour;

    if (n)
    {
        hour = n;
        tm->tm_min = 0;
        tm->tm_sec = 0;
    }

    tm->tm_hour = (hour % 12) + 12;
}

static void date_am(struct atm *tm, struct atm *now, int *num)
{
    int hour, n = *num;
    *num = 0;

    hour = tm->tm_hour;

    if (n)
    {
        hour = n;
        tm->tm_min = 0;
        tm->tm_sec = 0;
    }

    tm->tm_hour = (hour % 12);
}

static void date_never(struct atm *tm, struct atm *now, int *num)
{
    time_t n = 0;
    localtime_r(&n, (struct tm*)tm);
}

static const struct special
{
    const char *name;
    void (*fn)(struct atm *, struct atm *, int *);
} special[] =
{
    { "yesterday", date_yesterday },
    { "noon", date_noon },
    { "midnight", date_midnight },
    { "tea", date_tea },
    { "PM", date_pm },
    { "AM", date_am },
    { "never", date_never },
    { "now", date_now },
    { NULL }
};

static const char *number_name[] =
{
    "zero", "one", "two", "three", "four",
    "five", "six", "seven", "eight", "nine", "ten",
};

static const struct typelen
{
    const char *type;
    int length;
} typelen[] =
{
    { "seconds", 1 },
    { "minutes", 60 },
    { "hours", 60 * 60 },
    { "days", 24 * 60 * 60 },
    { "weeks", 7 * 24 * 60 * 60 },
    { NULL }
};

static const char *approxidate_alpha(const char *date, struct atm *tm, struct atm *now, int *num, int *touched)
{
    const struct typelen *tl;
    const struct special *s;
    const char *end = date;
    int i;

    while (isalpha(*++end))
        ;

    for (i = 0; i < 12; i++)
    {
        int match = match_string(date, month_names[i]);

        if (match >= 3)
        {
            tm->tm_mon = i;
            *touched = 1;
            return end;
        }
    }

    for (s = special; s->name; s++)
    {
        int len = strlen(s->name);

        if (match_string(date, s->name) == len)
        {
            s->fn(tm, now, num);
            *touched = 1;
            return end;
        }
    }

    if (!*num)
    {
        for (i = 1; i < 11; i++)
        {
            int len = strlen(number_name[i]);

            if (match_string(date, number_name[i]) == len)
            {
                *num = i;
                *touched = 1;
                return end;
            }
        }

        if (match_string(date, "last") == 4)
        {
            *num = 1;
            *touched = 1;
        }

        return end;
    }

    tl = typelen;

    while (tl->type)
    {
        int len = strlen(tl->type);

        if (match_string(date, tl->type) >= len - 1)
        {
            update_tm(tm, now, tl->length **num);
            *num = 0;
            *touched = 1;
            return end;
        }

        tl++;
    }

    for (i = 0; i < 7; i++)
    {
        int match = match_string(date, weekday_names[i]);

        if (match >= 3)
        {
            int diff, n = *num - 1;
            *num = 0;

            diff = tm->tm_wday - i;

            if (diff <= 0)
                n++;

            diff += 7 * n;

            update_tm(tm, now, diff * 24 * 60 * 60);
            *touched = 1;
            return end;
        }
    }

    if (match_string(date, "months") >= 5)
    {
        int n;
        update_tm(tm, now, 0); /* fill in date fields if needed */
        n = tm->tm_mon - *num;
        *num = 0;

        while (n < 0)
        {
            n += 12;
            tm->tm_year--;
        }

        tm->tm_mon = n;
        *touched = 1;
        return end;
    }

    if (match_string(date, "years") >= 4)
    {
        update_tm(tm, now, 0); /* fill in date fields if needed */
        tm->tm_year -= *num;
        *num = 0;
        *touched = 1;
        return end;
    }

    return end;
}

static const char *approxidate_digit(const char *date, struct atm *tm, int *num,
                                     time_t now)
{
    char *end;
    unsigned long number = strtoul(date, &end, 10);

    switch (*end)
    {
    case ':':
    case '.':
    case '/':
    case '-':
        if (isdigit(end[1]))
        {
            int match = match_multi_number(number, *end, date, end,
                                           tm, now);

            if (match)
                return date + match;
        }
    }

    /* Accept zero-padding only for small numbers ("Dec 02", never "Dec 0002") */
    if (date[0] != '0' || end - date <= 2)
        *num = number;

    return end;
}

/*
 * Do we have a pending number at the end, or when
 * we see a new one? Let's assume it's a month day,
 * as in "Dec 6, 1992"
 */
static void pending_number(struct atm *tm, int *num)
{
    int number = *num;

    if (number)
    {
        *num = 0;

        if (tm->tm_mday < 0 && number < 32)
            tm->tm_mday = number;
        else if (tm->tm_mon < 0 && number < 13)
            tm->tm_mon = number - 1;
        else if (tm->tm_year < 0)
        {
            if (number > 1969 && number < 2100)
                tm->tm_year = number - 1900;
            else if (number > 69 && number < 100)
                tm->tm_year = number;
            else if (number < 38)
                tm->tm_year = 100 + number;

            /* We screw up for number = 00 ? */
        }
    }
}

static int approxidate_str(const char *date, struct timeval *tv)
{
    int number = 0;
    int touched = 0;
    struct atm tm, now;
    time_t time_sec;

    time_sec = tv->tv_sec;
    localtime_r(&time_sec, (struct tm*)&tm);
    now = tm;

    tm.tm_year = -1;
    tm.tm_mon = -1;
    tm.tm_mday = -1;
    tm.tm_usec = tv->tv_usec;

    for (;;)
    {
        unsigned char c = *date;

        if (!c)
            break;

        date++;

        if (isdigit(c))
        {
            pending_number(&tm, &number);
            date = approxidate_digit(date - 1, &tm, &number, time_sec);
            touched = 1;
            continue;
        }

        if (isalpha(c))
            date = approxidate_alpha(date - 1, &tm, &now, &number, &touched);
    }

    pending_number(&tm, &number);

    if (!touched)
        return -1;

    tv->tv_usec = tm.tm_usec;
    tv->tv_sec = update_tm(&tm, &now, 0);

    return 0;
}

int approxidate(const char *date, struct timeval *tv)
{
    int offset;

    if (!parse_date_basic(date, tv, &offset))
    {
        return 0;
    }

    gettimeofday(tv, NULL);

    if (!approxidate_str(date, tv))
    {
        return 0;
    }

    return -1;
}
