/* undo.c: This file contains the undo routines for the ed line editor */
/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 1993 Andrew Moore, Talke Studio.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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>
#include "ed.h"


#define USIZE 100                               /* undo stack size */
static undo_t *ustack = NULL;                   /* undo stack */
static long usize = 0;                          /* stack size variable */
static long u_p = 0;                            /* undo stack pointer */

/* push_undo_stack: return pointer to initialized undo node */
undo_t *
push_undo_stack(int type, long from, long to)
{
        undo_t *t;

#if defined(sun) || defined(NO_REALLOC_NULL)
        if (ustack == NULL &&
            (ustack = (undo_t *) malloc((usize = USIZE) * sizeof(undo_t))) == NULL) {
                fprintf(stderr, "%s\n", strerror(errno));
                errmsg = "out of memory";
                return NULL;
        }
#endif
        t = ustack;
        if (u_p < usize ||
            (t = (undo_t *) realloc(ustack, (usize += USIZE) * sizeof(undo_t))) != NULL) {
                ustack = t;
                ustack[u_p].type = type;
                ustack[u_p].t = get_addressed_line_node(to);
                ustack[u_p].h = get_addressed_line_node(from);
                return ustack + u_p++;
        }
        /* out of memory - release undo stack */
        fprintf(stderr, "%s\n", strerror(errno));
        errmsg = "out of memory";
        clear_undo_stack();
        free(ustack);
        ustack = NULL;
        usize = 0;
        return NULL;
}


/* USWAP: swap undo nodes */
#define USWAP(x,y) { \
        undo_t utmp; \
        utmp = x, x = y, y = utmp; \
}


long u_current_addr = -1;       /* if >= 0, undo enabled */
long u_addr_last = -1;          /* if >= 0, undo enabled */

/* pop_undo_stack: undo last change to the editor buffer */
int
pop_undo_stack(void)
{
        long n;
        long o_current_addr = current_addr;
        long o_addr_last = addr_last;

        if (u_current_addr == -1 || u_addr_last == -1) {
                errmsg = "nothing to undo";
                return ERR;
        } else if (u_p)
                modified = 1;
        get_addressed_line_node(0);     /* this get_addressed_line_node last! */
        SPL1();
        for (n = u_p; n-- > 0;) {
                switch(ustack[n].type) {
                case UADD:
                        REQUE(ustack[n].h->q_back, ustack[n].t->q_forw);
                        break;
                case UDEL:
                        REQUE(ustack[n].h->q_back, ustack[n].h);
                        REQUE(ustack[n].t, ustack[n].t->q_forw);
                        break;
                case UMOV:
                case VMOV:
                        REQUE(ustack[n - 1].h, ustack[n].h->q_forw);
                        REQUE(ustack[n].t->q_back, ustack[n - 1].t);
                        REQUE(ustack[n].h, ustack[n].t);
                        n--;
                        break;
                default:
                        /*NOTREACHED*/
                        ;
                }
                ustack[n].type ^= 1;
        }
        /* reverse undo stack order */
        for (n = u_p; n-- > (u_p + 1)/ 2;)
                USWAP(ustack[n], ustack[u_p - 1 - n]);
        if (isglobal)
                clear_active_list();
        current_addr = u_current_addr, u_current_addr = o_current_addr;
        addr_last = u_addr_last, u_addr_last = o_addr_last;
        SPL0();
        return 0;
}


/* clear_undo_stack: clear the undo stack */
void
clear_undo_stack(void)
{
        line_t *lp, *ep, *tl;

        while (u_p--)
                if (ustack[u_p].type == UDEL) {
                        ep = ustack[u_p].t->q_forw;
                        for (lp = ustack[u_p].h; lp != ep; lp = tl) {
                                unmark_line_node(lp);
                                tl = lp->q_forw;
                                free(lp);
                        }
                }
        u_p = 0;
        u_current_addr = current_addr;
        u_addr_last = addr_last;
}