/*      $NetBSD: allow.c,v 1.9 2024/08/22 20:46:40 rillig Exp $ */

/*
* Copyright (c) 1980, 1993
*      The Regents of the University of California.  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 the University 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 THE REGENTS 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 REGENTS 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.
*/

#include <sys/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)allow.c     8.1 (Berkeley) 5/31/93";
#else
__RCSID("$NetBSD: allow.c,v 1.9 2024/08/22 20:46:40 rillig Exp $");
#endif
#endif /* not lint */

#include "back.h"

int
movallow(struct move *mm)
{
       int     i, m, iold;

       if (mm->d0)
               mswap(mm);
       m = (mm->D0 == mm->D1 ? 4 : 2);
       for (i = 0; i < 4; i++)
               mm->p[i] = bar;
       i = iold = 0;
       while (i < m) {
               if (*offptr == 15)
                       break;
               mm->h[i] = 0;
               if (board[bar]) {
                       if (i == 1 || m == 4)
                               mm->g[i] = bar + cturn * mm->D1;
                       else
                               mm->g[i] = bar + cturn * mm->D0;
                       if (makmove(mm, i) != 0) {
                               if (mm->d0 || m == 4)
                                       break;
                               mswap(mm);
                               movback(mm, i);
                               if (i > iold)
                                       iold = i;
                               for (i = 0; i < 4; i++)
                                       mm->p[i] = bar;
                               i = 0;
                       } else
                               i++;
                       continue;
               }
               if ((mm->p[i] += cturn) == home) {
                       if (i > iold)
                               iold = i;
                       if (m == 2 && i) {
                               movback(mm, i);
                               mm->p[i--] = bar;
                               if (mm->p[i] != bar)
                                       continue;
                               else
                                       break;
                       }
                       if (mm->d0 || m == 4)
                               break;
                       mswap(mm);
                       movback(mm, i);
                       for (i = 0; i < 4; i++)
                               mm->p[i] = bar;
                       i = 0;
                       continue;
               }
               if (i == 1 || m == 4)
                       mm->g[i] = mm->p[i] + cturn * mm->D1;
               else
                       mm->g[i] = mm->p[i] + cturn * mm->D0;
               if (mm->g[i] * cturn > home) {
                       if (*offptr >= 0)
                               mm->g[i] = home;
                       else
                               continue;
               }
               if (board[mm->p[i]] * cturn > 0 && makmove(mm, i) == 0)
                       i++;
       }
       movback(mm, i);
       return (iold > i ? iold : i);
}