/*      $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);
}