/*-
 * Copyright (C) 1996
 *      David L. Nugent.  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.
 *
 * THIS SOFTWARE IS PROVIDED BY DAVID L. NUGENT 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 DAVID L. NUGENT 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.
 *
 * $FreeBSD: src/usr.sbin/pw/psdate.c,v 1.8 2004/06/17 14:07:16 robert Exp $
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#include "psdate.h"


static int
a2i(char const ** str)
{
        int             i = 0;
        char const     *s = *str;

        if (isdigit((unsigned char)*s)) {
                i = atoi(s);
                while (isdigit((unsigned char)*s))
                        ++s;
                *str = s;
        }
        return i;
}

static int
numerics(char const * str)
{
        int             rc = isdigit((unsigned char)*str);

        if (rc)
                while (isdigit((unsigned char)*str) || *str == 'x')
                        ++str;
        return rc && !*str;
}

static int
aindex(char const * arr[], char const ** str, int len)
{
        int             l, i;
        char            mystr[32];

        mystr[len] = '\0';
        l = strlen(strncpy(mystr, *str, len));
        for (i = 0; i < l; i++)
                mystr[i] = (char) tolower((unsigned char)mystr[i]);
        for (i = 0; arr[i] && strcmp(mystr, arr[i]) != 0; i++);
        if (arr[i] == NULL)
                i = -1;
        else {                  /* Skip past it */
                while (**str && isalpha((unsigned char)**str))
                        ++(*str);
                /* And any following whitespace */
                while (**str && (**str == ',' || isspace((unsigned char)**str)))
                        ++(*str);
        }                       /* Return index */
        return i;
}

static int
weekday(char const ** str)
{
        static char const *days[] =
        {"sun", "mon", "tue", "wed", "thu", "fri", "sat", NULL};

        return aindex(days, str, 3);
}

static int
month(char const ** str)
{
        static char const *months[] =
        {"jan", "feb", "mar", "apr", "may", "jun", "jul",
        "aug", "sep", "oct", "nov", "dec", NULL};

        return aindex(months, str, 3);
}

static void
parse_time(char const * str, int *hour, int *min, int *sec)
{
        *hour = a2i(&str);
        if ((str = strchr(str, ':')) == NULL)
                *min = *sec = 0;
        else {
                ++str;
                *min = a2i(&str);
                *sec = ((str = strchr(str, ':')) == NULL) ? 0 : atoi(++str);
        }
}


static void
parse_datesub(char const * str, int *day, int *mon, int *year)
{
        int             i;

        static char const nchrs[] = "0123456789 \t,/-.";

        if ((i = month(&str)) != -1) {
                *mon = i;
                if ((i = a2i(&str)) != 0)
                        *day = i;
        } else if ((i = a2i(&str)) != 0) {
                *day = i;
                while (*str && strchr(nchrs + 10, *str) != NULL)
                        ++str;
                if ((i = month(&str)) != -1)
                        *mon = i;
                else if ((i = a2i(&str)) != 0)
                        *mon = i - 1;
        } else
                return;

        while (*str && strchr(nchrs + 10, *str) != NULL)
                ++str;
        if (isdigit((unsigned char)*str)) {
                *year = atoi(str);
                if (*year > 1900)
                        *year -= 1900;
                else if (*year < 32)
                        *year += 100;
        }
}


/*-
 * Parse time must be flexible, it handles the following formats:
 * nnnnnnnnnnn          UNIX timestamp (all numeric), 0 = now
 * 0xnnnnnnnn           UNIX timestamp in hexadecimal
 * 0nnnnnnnnn           UNIX timestamp in octal
 * 0                    Given time
 * +nnnn[smhdwoy]       Given time + nnnn hours, mins, days, weeks, months or years
 * -nnnn[smhdwoy]       Given time - nnnn hours, mins, days, weeks, months or years
 * dd[ ./-]mmm[ ./-]yy  Date }
 * hh:mm:ss             Time } May be combined
 */

time_t
parse_date(time_t dt, char const * str)
{
        char           *p;
        int             i;
        long            val;
        struct tm      *T;

        if (dt == 0)
                dt = time(NULL);

        while (*str && isspace((unsigned char)*str))
                ++str;

        if (numerics(str)) {
                dt = strtol(str, &p, 0);
        } else if (*str == '+' || *str == '-') {
                val = strtol(str, &p, 0);
                switch (*p) {
                case 'h':
                case 'H':       /* hours */
                        dt += (val * 3600L);
                        break;
                case '\0':
                case 'm':
                case 'M':       /* minutes */
                        dt += (val * 60L);
                        break;
                case 's':
                case 'S':       /* seconds */
                        dt += val;
                        break;
                case 'd':
                case 'D':       /* days */
                        dt += (val * 86400L);
                        break;
                case 'w':
                case 'W':       /* weeks */
                        dt += (val * 604800L);
                        break;
                case 'o':
                case 'O':       /* months */
                        T = localtime(&dt);
                        T->tm_mon += (int) val;
                        i = T->tm_mday;
                        goto fixday;
                case 'y':
                case 'Y':       /* years */
                        T = localtime(&dt);
                        T->tm_year += (int) val;
                        i = T->tm_mday;
        fixday:
                        dt = mktime(T);
                        T = localtime(&dt);
                        if (T->tm_mday != i) {
                                T->tm_mday = 1;
                                dt = mktime(T);
                                dt -= (time_t) 86400L;
                        }
                default:        /* unknown */
                        break;  /* leave untouched */
                }
        } else {
                char           *q, tmp[64];

                /*
                 * Skip past any weekday prefix
                 */
                weekday(&str);
                strlcpy(tmp, str, sizeof(tmp));
                str = tmp;
                T = localtime(&dt);

                /*
                 * See if we can break off any timezone
                 */
                while ((q = strrchr(tmp, ' ')) != NULL) {
                        if (strchr("(+-", q[1]) != NULL)
                                *q = '\0';
                        else {
                                int             j = 1;

                                while (q[j] && isupper((unsigned char)q[j]))
                                        ++j;
                                if (q[j] == '\0')
                                        *q = '\0';
                                else
                                        break;
                        }
                }

                /*
                 * See if there is a time hh:mm[:ss]
                 */
                if ((p = strchr(tmp, ':')) == NULL) {

                        /*
                         * No time string involved
                         */
                        T->tm_hour = T->tm_min = T->tm_sec = 0;
                        parse_datesub(tmp, &T->tm_mday, &T->tm_mon, &T->tm_year);
                } else {
                        char            datestr[64], timestr[64];

                        /*
                         * Let's chip off the time string
                         */
                        if ((q = strpbrk(p, " \t")) != NULL) {  /* Time first? */
                                int             l = q - str;

                                strlcpy(timestr, str, l + 1);
                                strlcpy(datestr, q + 1, sizeof(datestr));
                                parse_time(timestr, &T->tm_hour, &T->tm_min, &T->tm_sec);
                                parse_datesub(datestr, &T->tm_mday, &T->tm_mon, &T->tm_year);
                        } else if ((q = strrchr(tmp, ' ')) != NULL) {   /* Time last */
                                int             l = q - tmp;

                                strlcpy(timestr, q + 1, sizeof(timestr));
                                strlcpy(datestr, tmp, l + 1);
                        } else  /* Bail out */
                                return dt;
                        parse_time(timestr, &T->tm_hour, &T->tm_min, &T->tm_sec);
                        parse_datesub(datestr, &T->tm_mday, &T->tm_mon, &T->tm_year);
                }
                dt = mktime(T);
        }
        return dt;
}