/*
 * Copyright (c) 1999 - 2002 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * 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 KTH 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 KTH AND ITS 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 KTH OR ITS 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 <config.h>
#include "roken.h"
#ifdef TEST_STRPFTIME
#include "strpftime-test.h"
#endif

static const char *abb_weekdays[] = {
    "Sun",
    "Mon",
    "Tue",
    "Wed",
    "Thu",
    "Fri",
    "Sat",
};

static const char *full_weekdays[] = {
    "Sunday",
    "Monday",
    "Tuesday",
    "Wednesday",
    "Thursday",
    "Friday",
    "Saturday",
};

static const char *abb_month[] = {
    "Jan",
    "Feb",
    "Mar",
    "Apr",
    "May",
    "Jun",
    "Jul",
    "Aug",
    "Sep",
    "Oct",
    "Nov",
    "Dec"
};

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

static const char *ampm[] = {
    "AM",
    "PM"
};

/*
 * Convert hour in [0, 24] to [12 1 - 11 12 1 - 11 12]
 */

static int
hour_24to12 (int hour)
{
    int ret = hour % 12;

    if (ret == 0)
        ret = 12;
    return ret;
}

/*
 * Return AM or PM for `hour'
 */

static const char *
hour_to_ampm (int hour)
{
    return ampm[hour / 12];
}

/*
 * Return the week number of `tm' (Sunday being the first day of the week)
 * as [0, 53]
 */

static int
week_number_sun (const struct tm *tm)
{
    return (tm->tm_yday + 7 - (tm->tm_yday % 7 - tm->tm_wday + 7) % 7) / 7;
}

/*
 * Return the week number of `tm' (Monday being the first day of the week)
 * as [0, 53]
 */

static int
week_number_mon (const struct tm *tm)
{
    int wday = (tm->tm_wday + 6) % 7;

    return (tm->tm_yday + 7 - (tm->tm_yday % 7 - wday + 7) % 7) / 7;
}

/*
 * Return the week number of `tm' (Monday being the first day of the
 * week) as [01, 53].  Week number one is the one that has four or more
 * days in that year.
 */

static int
week_number_mon4 (const struct tm *tm)
{
    int wday  = (tm->tm_wday + 6) % 7;
    int w1day = (wday - tm->tm_yday % 7 + 7) % 7;
    int ret;

    ret = (tm->tm_yday + w1day) / 7;
    if (w1day >= 4)
        --ret;
    if (ret == -1)
        ret = 53;
    else
        ++ret;
    return ret;
}

/*
 *
 */

ROKEN_LIB_FUNCTION size_t ROKEN_LIB_CALL
strftime (char *buf, size_t maxsize, const char *format,
          const struct tm *tm)
{
    size_t n = 0;
    int ret;

    while (*format != '\0' && n < maxsize) {
        if (*format == '%') {
            ++format;
            if(*format == 'E' || *format == 'O')
                ++format;
            switch (*format) {
            case 'a' :
                ret = snprintf (buf, maxsize - n,
                                "%s", abb_weekdays[tm->tm_wday]);
                break;
            case 'A' :
                ret = snprintf (buf, maxsize - n,
                                "%s", full_weekdays[tm->tm_wday]);
                break;
            case 'h' :
            case 'b' :
                ret = snprintf (buf, maxsize - n,
                                "%s", abb_month[tm->tm_mon]);
                break;
            case 'B' :
                ret = snprintf (buf, maxsize - n,
                                "%s", full_month[tm->tm_mon]);
                break;
            case 'c' :
                ret = snprintf (buf, maxsize - n,
                                "%d:%02d:%02d %02d:%02d:%02d",
                                tm->tm_year,
                                tm->tm_mon + 1,
                                tm->tm_mday,
                                tm->tm_hour,
                                tm->tm_min,
                                tm->tm_sec);
                break;
            case 'C' :
                ret = snprintf (buf, maxsize - n,
                                "%02d", (tm->tm_year + 1900) / 100);
                break;
            case 'd' :
                ret = snprintf (buf, maxsize - n,
                                "%02d", tm->tm_mday);
                break;
            case 'D' :
                ret = snprintf (buf, maxsize - n,
                                "%02d/%02d/%02d",
                                tm->tm_mon + 1,
                                tm->tm_mday,
                                (tm->tm_year + 1900) % 100);
                break;
            case 'e' :
                ret = snprintf (buf, maxsize - n,
                                "%2d", tm->tm_mday);
                break;
            case 'F':
                ret = snprintf (buf, maxsize - n,
                                "%04d-%02d-%02d", tm->tm_year + 1900,
                                tm->tm_mon + 1, tm->tm_mday);
                break;
            case 'g':
                /* last two digits of week-based year */
                abort();
            case 'G':
                /* week-based year */
                abort();
            case 'H' :
                ret = snprintf (buf, maxsize - n,
                                "%02d", tm->tm_hour);
                break;
            case 'I' :
                ret = snprintf (buf, maxsize - n,
                                "%02d",
                                hour_24to12 (tm->tm_hour));
                break;
            case 'j' :
                ret = snprintf (buf, maxsize - n,
                                "%03d", tm->tm_yday + 1);
                break;
            case 'k' :
                ret = snprintf (buf, maxsize - n,
                                "%2d", tm->tm_hour);
                break;
            case 'l' :
                ret = snprintf (buf, maxsize - n,
                                "%2d",
                                hour_24to12 (tm->tm_hour));
                break;
            case 'm' :
                ret = snprintf (buf, maxsize - n,
                                "%02d", tm->tm_mon + 1);
                break;
            case 'M' :
                ret = snprintf (buf, maxsize - n,
                                "%02d", tm->tm_min);
                break;
            case 'n' :
                ret = snprintf (buf, maxsize - n, "\n");
                break;
            case 'p' :
                ret = snprintf (buf, maxsize - n, "%s",
                                hour_to_ampm (tm->tm_hour));
                break;
            case 'r' :
                ret = snprintf (buf, maxsize - n,
                                "%02d:%02d:%02d %s",
                                hour_24to12 (tm->tm_hour),
                                tm->tm_min,
                                tm->tm_sec,
                                hour_to_ampm (tm->tm_hour));
                break;
            case 'R' :
                ret = snprintf (buf, maxsize - n,
                                "%02d:%02d",
                                tm->tm_hour,
                                tm->tm_min);
                break;
            case 's' :
                ret = snprintf (buf, maxsize - n,
                                "%d", (int)mktime(rk_UNCONST(tm)));
                break;
            case 'S' :
                ret = snprintf (buf, maxsize - n,
                                "%02d", tm->tm_sec);
                break;
            case 't' :
                ret = snprintf (buf, maxsize - n, "\t");
                break;
            case 'T' :
            case 'X' :
                ret = snprintf (buf, maxsize - n,
                                "%02d:%02d:%02d",
                                tm->tm_hour,
                                tm->tm_min,
                                tm->tm_sec);
                break;
            case 'u' :
                ret = snprintf (buf, maxsize - n,
                                "%d", (tm->tm_wday == 0) ? 7 : tm->tm_wday);
                break;
            case 'U' :
                ret = snprintf (buf, maxsize - n,
                                "%02d", week_number_sun (tm));
                break;
            case 'V' :
                ret = snprintf (buf, maxsize - n,
                                "%02d", week_number_mon4 (tm));
                break;
            case 'w' :
                ret = snprintf (buf, maxsize - n,
                                "%d", tm->tm_wday);
                break;
            case 'W' :
                ret = snprintf (buf, maxsize - n,
                                "%02d", week_number_mon (tm));
                break;
            case 'x' :
                ret = snprintf (buf, maxsize - n,
                                "%d:%02d:%02d",
                                tm->tm_year,
                                tm->tm_mon + 1,
                                tm->tm_mday);
                break;
            case 'y' :
                ret = snprintf (buf, maxsize - n,
                                "%02d", (tm->tm_year + 1900) % 100);
                break;
            case 'Y' :
                ret = snprintf (buf, maxsize - n,
                                "%d", tm->tm_year + 1900);
                break;
            case 'z':
                ret = snprintf (buf, maxsize - n,
                                "%ld",
#if defined(HAVE_STRUCT_TM_TM_GMTOFF)
                                (long)tm->tm_gmtoff
#elif defined(HAVE_TIMEZONE)
#ifdef HAVE_ALTZONE
                                tm->tm_isdst ?
                                (long)altzone :
#endif
                                (long)timezone
#else
#error Where in timezone chaos are you?
#endif
                                );
                break;
            case 'Z' :
                ret = snprintf (buf, maxsize - n,
                                "%s",

#if defined(HAVE_STRUCT_TM_TM_ZONE)
                                tm->tm_zone
#elif defined(HAVE_TIMEZONE)
                                tzname[tm->tm_isdst]
#else
#error what?
#endif
                    );
                break;
            case '\0' :
                --format;
                /* FALLTHROUGH */
            case '%' :
                ret = snprintf (buf, maxsize - n,
                                "%%");
                break;
            default :
                ret = snprintf (buf, maxsize - n,
                                "%%%c", *format);
                break;
            }
            if (ret < 0 || ret >= (int)(maxsize - n))
                return 0;
            n   += ret;
            buf += ret;
            ++format;
        } else {
            *buf++ = *format++;
            ++n;
        }
    }
    *buf = '\0';
    return n;
}