/*-
 * Copyright (c) 1997, 1998, 2005, 2008 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code was contributed to The NetBSD Foundation by Klaus Klein.
 * Heavily optimised by David Laight
 *
 * 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 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.
 */

/*
 * Inclusion in node-odbc note:
 *
 * This code was found here: http://social.msdn.microsoft.com/forums/en-US/vcgeneral/thread/25a654f9-b6b6-490a-8f36-c87483bb36b7
 * One user posted what looks to be a scaled down version of the NetBSD code
 * but did not include any header with their work. Since it seems pretty obvious
 * that the user took much of the code from NetBSD, that is why the NetBSD header 
 * is displayed above.
 */

#include "strptime.h"

static int conv_num(const char **, int *, int, int);
static int strncasecmp(char *s1, char *s2, size_t n);

char * strptime(const char *buf, const char *fmt, struct tm *tm)
{
  char c;
  const char *bp;
  size_t len = 0;
  int alt_format, i, split_year = 0;

  bp = 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 (0);
          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, "%x %X", tm)))
          return (0);
        break;

      case 'D': /* The date as "%m/%d/%y". */
        LEGAL_ALT(0);
        if (!(bp = strptime(bp, "%m/%d/%y", tm)))
          return (0);
        break;

      case 'R': /* The time as "%H:%M". */
        LEGAL_ALT(0);
        if (!(bp = strptime(bp, "%H:%M", tm)))
          return (0);
        break;

      case 'r': /* The time in 12-hour clock representation. */
        LEGAL_ALT(0);
        if (!(bp = strptime(bp, "%I:%M:%S %p", tm)))
          return (0);
        break;

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

      case 'X': /* The time, using the locale's format. */
        LEGAL_ALT(ALT_E);
        if (!(bp = strptime(bp, "%H:%M:%S", tm)))
          return (0);
        break;

      case 'x': /* The date, using the locale's format. */
        LEGAL_ALT(ALT_E);
        if (!(bp = strptime(bp, "%m/%d/%y", tm)))
          return (0);
        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(day[i]);
          if (strncasecmp((char *)(day[i]), (char *)bp, len) == 0)
            break;

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

        /* Nothing matched. */
        if (i == 7)
          return (0);

        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(mon[i]);
          if (strncasecmp((char *)(mon[i]), (char *)bp, len) == 0)
            break;

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

        /* Nothing matched. */
        if (i == 12)
          return (0);

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

      case 'C': /* The century number. */
        LEGAL_ALT(ALT_E);
        if (!(conv_num(&bp, &i, 0, 99)))
          return (0);

        if (split_year)
        {
          tm->tm_year = (tm->tm_year % 100) + (i * 100);
        } else {
          tm->tm_year = i * 100;
          split_year = 1;
        }
        break;

      case 'd': /* The day of month. */
      case 'e':
        LEGAL_ALT(ALT_O);
        if (!(conv_num(&bp, &tm->tm_mday, 1, 31)))
          return (0);
        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 (0);
        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 (0);
        if (tm->tm_hour == 12)
          tm->tm_hour = 0;
        break;

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

      case 'M': /* The minute. */
        LEGAL_ALT(ALT_O);
        if (!(conv_num(&bp, &tm->tm_min, 0, 59)))
          return (0);
        break;

      case 'm': /* The month. */
        LEGAL_ALT(ALT_O);
        if (!(conv_num(&bp, &i, 1, 12)))
          return (0);
        tm->tm_mon = i - 1;
        break;

//      case 'p': /* The locale's equivalent of AM/PM. */
//        LEGAL_ALT(0);
//        /* AM? */
//        if (strcasecmp(am_pm[0], bp) == 0)
//        {
//          if (tm->tm_hour > 11)
//            return (0);
//
//          bp += strlen(am_pm[0]);
//          break;
//        }
//        /* PM? */
//        else if (strcasecmp(am_pm[1], bp) == 0)
//        {
//          if (tm->tm_hour > 11)
//            return (0);
//
//          tm->tm_hour += 12;
//          bp += strlen(am_pm[1]);
//          break;
//        }
//
//        /* Nothing matched. */
//        return (0);

      case 'S': /* The seconds. */
        LEGAL_ALT(ALT_O);
        if (!(conv_num(&bp, &tm->tm_sec, 0, 61)))
          return (0);
        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 (0);
        break;

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

      case 'Y': /* The year. */
        LEGAL_ALT(ALT_E);
        if (!(conv_num(&bp, &i, 0, 9999)))
          return (0);

        tm->tm_year = i - TM_YEAR_BASE;
        break;

      case 'y': /* The year within 100 years of the epoch. */
        LEGAL_ALT(ALT_E | ALT_O);
        if (!(conv_num(&bp, &i, 0, 99)))
          return (0);

        if (split_year)
        {
          tm->tm_year = ((tm->tm_year / 100) * 100) + i;
          break;
        }
        split_year = 1;
        if (i <= 68)
          tm->tm_year = i + 2000 - TM_YEAR_BASE;
        else
          tm->tm_year = i + 1900 - TM_YEAR_BASE;
        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 (0);
    }


  }

  /* LINTED functional specification */
  return ((char *)bp);
}


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

  /* The limit also determines the number of valid digits. */
  int rulim = ulim;

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

  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);
}

int strncasecmp(char *s1, char *s2, size_t n)
{
  if (n == 0)
    return 0;

  while (n-- != 0 && tolower(*s1) == tolower(*s2))
  {
    if (n == 0 || *s1 == '\0' || *s2 == '\0')
      break;
    s1++;
    s2++;
  }

  return tolower(*(unsigned char *) s1) - tolower(*(unsigned char *) s2);
}