/*      @(#)wwupdate.c  8.1 (Berkeley) 6/6/93   */
/*      $NetBSD: wwupdate.c,v 1.6 2003/08/07 11:17:46 agc Exp $ */

/*
 * Copyright (c) 1983, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Edward Wang at The University of California, Berkeley.
 *
 * 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 "ww.h"
#include "tt.h"
#include "xx.h"

void
wwupdate1(int top, int bot)
{
        int i;
        int j;
        char *touched;
        struct ww_update *upd;
        char check_clreos = 0;
        int scan_top, scan_bot;

        wwnupdate++;
        {
                char *t1 = wwtouched + top, *t2 = wwtouched + bot;
                int n;

                while (!*t1++)
                        if (t1 == t2)
                                return;
                while (!*--t2)
                        ;
                scan_top = top = t1 - wwtouched - 1;
                scan_bot = bot = t2 - wwtouched + 1;
                if (scan_bot - scan_top > 1 &&
                    (tt.tt_clreos != 0 || tt.tt_clear != 0)) {
                        int st = tt.tt_clreos != 0 ? scan_top : 0;

                        /*
                         * t1 is one past the first touched row,
                         * t2 is on the last touched row.
                         */
                        for (t1--, n = 1; t1 < t2;)
                                if (*t1++)
                                        n++;
                        /*
                         * If we can't clreos then we try for clearing
                         * the whole screen.
                         */
                        if ((check_clreos = n * 10 > (wwnrow - st) * 9)) {
                                scan_top = st;
                                scan_bot = wwnrow;
                        }
                }
        }
        if (tt.tt_clreol == 0 && !check_clreos)
                goto simple;
        for (i = scan_top, touched = &wwtouched[i], upd = &wwupd[i];
             i < scan_bot;
             i++, touched++, upd++) {
                int gain = 0;
                int best_gain = 0;
                int best_col = 0;
                union ww_char *ns, *os;

                if (wwinterrupt())
                        return;
                if (!check_clreos && !*touched)
                        continue;
                wwnupdscan++;
                j = wwncol;
                ns = &wwns[i][j];
                os = &wwos[i][j];
                while (--j >= 0) {
                        /*
                         * The cost of clearing is:
                         *      ncol - nblank + X
                         * The cost of straight update is, more or less:
                         *      ncol - nsame
                         * We clear if  nblank - nsame > X
                         * X is the clreol overhead.
                         * So we make gain = nblank - nsame.
                         */
                        if ((--ns)->c_w == (--os)->c_w)
                                gain--;
                        else
                                best_gain--;
                        if (ns->c_w == ' ')
                                gain++;
                        if (gain > best_gain) {
                                best_col = j;
                                best_gain = gain;
                        }
                }
                upd->best_gain = best_gain;
                upd->best_col = best_col;
                upd->gain = gain;
        }
        if (check_clreos) {
                struct ww_update *u;
                int gain = 0;
                int best_gain = 0;
                int best_row = 0;
                int simple_gain = 0;
                char didit = 0;

                /*
                 * gain is the advantage of clearing all the lines.
                 * best_gain is the advantage of clearing to eos
                 * at best_row and u->best_col.
                 * simple_gain is the advantage of using only clreol.
                 * We use g > best_gain because u->best_col can be
                 * undefined when u->best_gain is 0 so we can't use it.
                 */
                for (j = scan_bot - 1, u = wwupd + j; j >= top; j--, u--) {
                        int g = gain + u->best_gain;

                        if (g > best_gain) {
                                best_gain = g;
                                best_row = j;
                        }
                        gain += u->gain;
                        if (tt.tt_clreol != 0 && u->best_gain > 4)
                                simple_gain += u->best_gain - 4;
                }
                if (tt.tt_clreos == 0) {
                        if (gain > simple_gain && gain > 4) {
                                xxclear();
                                i = top = scan_top;
                                bot = scan_bot;
                                j = 0;
                                didit = 1;
                        }
                } else
                        if (best_gain > simple_gain && best_gain > 4) {
                                i = best_row;
                                xxclreos(i, j = wwupd[i].best_col);
                                bot = scan_bot;
                                didit = 1;
                        }
                if (didit) {
                        wwnupdclreos++;
                        wwnupdclreosline += wwnrow - i;
                        u = wwupd + i;
                        while (i < scan_bot) {
                                union ww_char *os = &wwos[i][j];

                                for (j = wwncol - j; --j >= 0;)
                                        os++->c_w = ' ';
                                wwtouched[i++] |= WWU_TOUCHED;
                                u++->best_gain = 0;
                                j = 0;
                        }
                } else
                        wwnupdclreosmiss++;
        }
simple:
        for (i = top, touched = &wwtouched[i], upd = &wwupd[i]; i < bot;
             i++, touched++, upd++) {
                union ww_char *os, *ns;
                char didit;

                if (!*touched)
                        continue;
                *touched = 0;
                wwnupdline++;
                didit = 0;
                if (tt.tt_clreol != 0 && upd->best_gain > 4) {
                        wwnupdclreol++;
                        xxclreol(i, j = upd->best_col);
                        for (os = &wwos[i][j], j = wwncol - j; --j >= 0;)
                                os++->c_w = ' ';
                        didit = 1;
                }
                ns = wwns[i];
                os = wwos[i];
                for (j = 0; j < wwncol;) {
                        char *p, *q;
                        char m;
                        int c;
                        int n;
                        char buf[512];                  /* > wwncol */
                        union ww_char lastc;

                        for (; j++ < wwncol && ns++->c_w == os++->c_w;)
                                ;
                        if (j > wwncol)
                                break;
                        p = buf;
                        m = ns[-1].c_m;
                        c = j - 1;
                        os[-1] = ns[-1];
                        *p++ = ns[-1].c_c;
                        n = 5;
                        q = p;
                        while (j < wwncol && ns->c_m == m) {
                                *p++ = ns->c_c;
                                if (ns->c_w == os->c_w) {
                                        if (--n <= 0)
                                                break;
                                        os++;
                                        ns++;
                                } else {
                                        n = 5;
                                        q = p;
                                        lastc = *os;
                                        *os++ = *ns++;
                                }
                                j++;
                        }
                        n = q - buf;
                        if (!wwwrap || i != wwnrow - 1 || c + n != wwncol)
                                xxwrite(i, c, buf, n, m);
                        else if (tt.tt_inschar || tt.tt_insspace) {
                                if (n > 1) {
                                        q[-2] = q[-1];
                                        n--;
                                } else
                                        c--;
                                xxwrite(i, c, buf, n, m);
                                c += n - 1;
                                if (tt.tt_inschar)
                                        xxinschar(i, c, ns[-2].c_c,
                                                ns[-2].c_m);
                                else {
                                        xxinsspace(i, c);
                                        xxwrite(i, c, &ns[-2].c_c, 1,
                                                ns[-2].c_m);
                                }
                        } else {
                                if (--n)
                                        xxwrite(i, c, buf, n, m);
                                os[-1] = lastc;
                                *touched = WWU_TOUCHED;
                        }
                        didit = 1;
                }
                if (!didit)
                        wwnupdmiss++;
        }
}