/* SQLite natural sort collation funtion
 * 
 * Natural sort of strings, ignoring case and leading spaces.
 * Alan Swanson <swanson@ukfsn.org> 2011
 *
 * strverscasecmp() function derived from uClibc 0.9.31 strverscmp() function
 * by Hai Zaar, Codefidence Ltd <haizaar@codefidence.com>
 * which in turn derived from from glibc 2.3.2 strverscmp() function
 * by Jean-François Bignolles <bignolle@ecoledoc.ibp.fr>
 * Copyright (C) 1997, 2002 Free Software Foundation, Inc.
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <string.h>
#include <ctype.h>
#include <stdint.h>

/* states: S_N: normal, S_I: comparing integral part, S_F: comparing
   fractional parts, S_Z: idem but with leading Zeroes only */
#define  S_N    0x0
#define  S_I    0x4
#define  S_F    0x8
#define  S_Z    0xC

/* result_type: CMP: return diff; LEN: compare using len_diff/diff */
#define  CMP    2
#define  LEN    3

/* using more efficient isdigit() */
#undef isdigit
#define isdigit(a) ((unsigned)((a) - '0') <= 9)

/* Compare S1 and S2 as strings holding indices/version numbers,
   returning less than, equal to or greater than zero if S1 is less than,
   equal to or greater than S2 (for more info, see the texinfo doc).
*/
static int strverscasecmp (const char *s1, const char *s2)
{
  const unsigned char *p1 = (const unsigned char *) s1;
  const unsigned char *p2 = (const unsigned char *) s2;
  unsigned char c1, c2;
  int state;
  int diff;

  /* Symbol(s)    0       [1-9]   others  (padding)
     Transition   (10) 0  (01) d  (00) x  (11) -   */
  static const uint8_t next_state[] =
  {
      /* state    x    d    0    - */
      /* S_N */  S_N, S_I, S_Z, S_N,
      /* S_I */  S_N, S_I, S_I, S_I,
      /* S_F */  S_N, S_F, S_F, S_F,
      /* S_Z */  S_N, S_F, S_Z, S_Z
  };

  static const int8_t result_type[] =
  {
      /* state   x/x  x/d  x/0  x/-  d/x  d/d  d/0  d/-
                 0/x  0/d  0/0  0/-  -/x  -/d  -/0  -/- */

      /* S_N */  CMP, CMP, CMP, CMP, CMP, LEN, CMP, CMP,
                 CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
      /* S_I */  CMP, -1,  -1,  CMP, +1,  LEN, LEN, CMP,
                 +1,  LEN, LEN, CMP, CMP, CMP, CMP, CMP,
      /* S_F */  CMP, CMP, CMP, CMP, CMP, LEN, CMP, CMP,
                 CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
      /* S_Z */  CMP, +1,  +1,  CMP, -1,  CMP, CMP, CMP,
                 -1,  CMP, CMP, CMP
  };

  if (p1 == p2)
    return 0;

  c1 = *p1;
  c2 = *p2;

  /* Skip leading spaces. */
  while (isspace(c1))
    c1 = *++p1;
  while (isspace(c2))
    c2 = *++p2;

  c1 = tolower(*p1++);
  c2 = tolower(*p2++);
  /* Hint: '0' is a digit too.  */
  state = S_N | ((c1 == '0') + (isdigit (c1) != 0));

  while ((diff = c1 - c2) == 0 && c1 != '\0')
    {
      state = next_state[state];
      c1 = tolower(*p1++);
      c2 = tolower(*p2++);
      state |= (c1 == '0') + (isdigit (c1) != 0);
    }

  state = result_type[state << 2 | (((c2 == '0') + (isdigit (c2) != 0)))];

  switch (state)
  {
    case CMP:
      return diff;

    case LEN:
      while (isdigit (*p1++))
	if (!isdigit (*p2++))
	  return 1;

      return isdigit (*p2) ? -1 : diff;

    default:
      return state;
  }
}

int
naturalsort(void *arg, int len1, const void *data1, int len2, const void *data2)
{
  return strverscasecmp((const char *)data1, (const char *)data2);
}