src/lib/subs/aircombat.c

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/*
 *  Empire - A multi-player, client/server Internet based war game.
 *  Copyright (C) 1986-2007, Dave Pare, Jeff Bailey, Thomas Ruschak,
 *                           Ken Stevens, Steve McClure
 *
 *  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
 *
 *  ---
 *
 *  See files README, COPYING and CREDITS in the root of the source
 *  tree for related information and legal notices.  It is expected
 *  that future projects/authors will amend these files as needed.
 *
 *  ---
 *
 *  aircombat.c: Deal with air to air combat
 * 
 *  Known contributors to this file:
 *     Dave Pare, 1986
 *     Thomas Ruschak, 1992
 *     Steve McClure, 1996
 *     Markus Armbruster, 2006
 */

#include <config.h>

#include "file.h"
#include "land.h"
#include "map.h"
#include "misc.h"
#include "nat.h"
#include "news.h"
#include "nsc.h"
#include "optlist.h"
#include "path.h"
#include "plane.h"
#include "player.h"
#include "prototypes.h"
#include "sect.h"
#include "ship.h"
#include "xy.h"

#define FLAK_GUN_MAX 14

static void ac_intercept(struct emp_qelem *, struct emp_qelem *,
                         struct emp_qelem *, natid, coord, coord);
static int all_missiles(struct emp_qelem *);
static void ac_dog(struct plist *, struct plist *);
static void ac_planedamage(struct plist *, natid, int, natid, int,
                           int, char *);
static void ac_doflak(struct emp_qelem *, struct sctstr *);
static void ac_landflak(struct emp_qelem *, coord, coord);
static void ac_shipflak(struct emp_qelem *, coord, coord);
static void ac_fireflak(struct emp_qelem *, natid, int);
static void getilist(struct emp_qelem *, natid,
                     struct emp_qelem *, struct emp_qelem *,
                     struct emp_qelem *, struct emp_qelem *);
static int do_evade(struct emp_qelem *, struct emp_qelem *);

void
ac_encounter(struct emp_qelem *bomb_list, struct emp_qelem *esc_list,
             coord x, coord y, char *path, int mission_flags,
             int no_air_defense, struct emp_qelem *obomb,
             struct emp_qelem *oesc)
{
    int val, non_missiles;
    int rel;
    int dir;
    int nats[MAXNOC];
    int lnats[MAXNOC];
    int gotilist[MAXNOC];
    int unfriendly[MAXNOC];
    int overfly[MAXNOC];
    struct emp_qelem ilist[MAXNOC], *qp;
    char mypath[1024];
    int myp;
    int civ, mil;
    natid plane_owner;
    struct sctstr sect;
    struct shpstr ship;
    struct lndstr land;
    struct nstr_item ni;
    natid cn;
    struct natstr *over, *mynatp;
    struct plist *plp;
    int evaded;
    struct shiplist *head = NULL;
    int changed = 0;
    int intown = 0;             /* Last owner to intercept */
/* We want to only intercept once per sector per owner.  So, if we overfly
   a sector, and then overfly some land units or ships, we don't want to
   potentially intercept 3 times. */

    plp = (struct plist *)bomb_list->q_forw;
    plane_owner = plp->plane.pln_own;

    strncpy(mypath, path, sizeof(mypath));
    myp = 0;

    memset(overfly, 0, sizeof(overfly));
    memset(gotilist, 0, sizeof(gotilist));
    memset(unfriendly, 0, sizeof(unfriendly));
    for (cn = 1; cn < MAXNOC; cn++) {
        if ((mynatp = getnatp(cn)) == 0)
            continue;
        rel = getrel(mynatp, plane_owner);
        if (rel > HOSTILE)
            continue;
        if (plane_owner == cn)
            continue;
        unfriendly[cn]++;
    }
    if (mission_flags & PM_R) {
        if (mission_flags & P_S) {
            PR(plane_owner, "\nSPY Plane report\n");
            PRdate(plane_owner);
            sathead();
        } else if (mission_flags & P_A) {
            PR(plane_owner, "\nAnti-Sub Patrol report\n");
        } else {
            PR(plane_owner, "\nReconnaissance report\n");
            PRdate(plane_owner);
        }
    }

    pln_removedupes(bomb_list, esc_list);
    while ((dir = mypath[myp++]) && !QEMPTY(bomb_list)) {
        if ((val = diridx(dir)) == DIR_STOP)
            break;
        /* XXX using xnorm is probably bad */
        x = xnorm(x + diroff[val][0]);
        y = ynorm(y + diroff[val][1]);
        getsect(x, y, &sect);
        over = getnatp(sect.sct_own);

        if (mission_flags & PM_R) {
            if (opt_HIDDEN)
                setcont(plane_owner, sect.sct_own, FOUND_FLY);
            if (sect.sct_type == SCT_WATER) {
                PR(plane_owner, "flying over %s at %s\n",
                   dchr[sect.sct_type].d_name, xyas(x, y, plane_owner));
                if (mission_flags & PM_S)
                    plane_sweep(bomb_list, x, y);
                if (mission_flags & P_A) {
                    plane_sona(bomb_list, x, y, &head);
                }
                changed += map_set(plane_owner,
                                   sect.sct_x, sect.sct_y,
                                   dchr[sect.sct_type].d_mnem, 0);
            } else if (mission_flags & P_S) {
                satdisp_sect(&sect, (mission_flags & P_I) ? 10 : 50);
            } else {
                /* This is borrowed from lookout */
                if (sect.sct_own == plane_owner)
                    PR(plane_owner, "Your ");
                else
                    PR(plane_owner, "%s (#%d) ",
                       cname(sect.sct_own), sect.sct_own);
                PR(plane_owner, "%s", dchr[sect.sct_type].d_name);
                changed += map_set(plane_owner,
                                   sect.sct_x, sect.sct_y,
                                   dchr[sect.sct_type].d_mnem, 0);
                PR(plane_owner, " %d%% efficient ",
                   (sect.sct_own == plane_owner) ?
                   sect.sct_effic : roundintby((int)sect.sct_effic, 25));
                civ = sect.sct_item[I_CIVIL];
                mil = sect.sct_item[I_MILIT];
                if (civ)
                    PR(plane_owner, "with %s%d civ ",
                       (sect.sct_own == plane_owner) ?
                       "" : "approx ",
                       (sect.sct_own == plane_owner) ?
                       civ : roundintby(civ, 25));
                if (mil)
                    PR(plane_owner, "with %s%d mil ",
                       (sect.sct_own == plane_owner) ?
                       "" : "approx ",
                       (sect.sct_own == plane_owner) ?
                       mil : roundintby(mil, 25));
                PR(plane_owner, "@ %s\n", xyas(x, y, plane_owner));
            }
            if (mission_flags & P_S)
                satdisp_units(sect.sct_x, sect.sct_y);
        } else {
            PR(plane_owner, "flying over %s at %s\n",
               dchr[sect.sct_type].d_name, xyas(x, y, plane_owner));
            changed += map_set(plane_owner, sect.sct_x, sect.sct_y,
                               dchr[sect.sct_type].d_mnem, 0);
        }
        if ((rel = getrel(over, plane_owner)) == ALLIED)
            continue;

        evaded = do_evade(bomb_list, esc_list);

        if (sect.sct_own != 0 && sect.sct_own != plane_owner && !evaded) {
            /* We only show planes overhead if they didn't
             * evade radar */
            overfly[sect.sct_own]++;
            PR(sect.sct_own, "%s planes spotted over %s\n",
               cname(plane_owner), xyas(x, y, sect.sct_own));
            if (opt_HIDDEN)
                setcont(cn, plane_owner, FOUND_FLY);
        }

        if (!evaded) {
            /* Fire flak */
            if (unfriendly[sect.sct_own])
                ac_doflak(bomb_list, &sect);
            /* If bombers left, fire flak from units and ships */
            if (!QEMPTY(bomb_list))
                ac_landflak(bomb_list, x, y);
            if (!QEMPTY(bomb_list))
                ac_shipflak(bomb_list, x, y);
        }
        /* mission planes aborted due to flak -- don't send escorts */
        if (QEMPTY(bomb_list))
            break;
        if (!no_air_defense && !evaded)
            air_defense(x, y, plane_owner, bomb_list, esc_list);

        if (sect.sct_own == 0 || sect.sct_own == plane_owner)
            continue;

        if (evaded)
            continue;

        non_missiles = 0;
        for (qp = bomb_list->q_forw; qp != bomb_list; qp = qp->q_forw) {
            struct plist *ip = (struct plist *)qp;
            if (!(plchr[(int)ip->plane.pln_type].pl_flags & P_M))
                non_missiles = 1;
        }

        if (!non_missiles)
            continue;

        if (unfriendly[sect.sct_own] && !gotilist[sect.sct_own]) {
            getilist(&ilist[sect.sct_own], sect.sct_own,
                     bomb_list, esc_list, obomb, oesc);
            gotilist[sect.sct_own]++;
        }
        if (rel > HOSTILE)
            continue;
        ac_intercept(bomb_list, esc_list, &ilist[sect.sct_own],
                     sect.sct_own, x, y);
        intown = sect.sct_own;
    }

    /* Let's report all of the overflights even if aborted */
    for (cn = 1; cn < MAXNOC; cn++) {
        if (plane_owner == cn)
            continue;
        if (overfly[cn] > 0)
            nreport(plane_owner, N_OVFLY_SECT, cn, overfly[cn]);
    }
    /* If the map changed, update it */
    if (changed)
        writemap(player->cnum);
    /* Now, if the bomber and escort lists are empty, we are done */
    if (QEMPTY(bomb_list) && QEMPTY(esc_list)) {
        if (mission_flags & P_A)
            free_shiplist(&head);
        return;
    }

    /* Something made it through */
    /* Go figure out if there are ships in this sector, and who's they are */
    memset(nats, 0, sizeof(nats));
    snxtitem_xy(&ni, EF_SHIP, x, y);
    while (nxtitem(&ni, &ship)) {
        if (mchr[(int)ship.shp_type].m_flags & M_SUB)
            continue;
        nats[ship.shp_own]++;
    }
    /* Go figure out if there are units in this sector, and who's they are */
    memset(lnats, 0, sizeof(lnats));
    snxtitem_xy(&ni, EF_LAND, x, y);
    while (nxtitem(&ni, &land)) {
        if (land.lnd_ship >= 0 || land.lnd_land >= 0)
            continue;
        lnats[land.lnd_own]++;
    }

    /* Now, let's make life a little rougher. */
    for (cn = 1; cn < MAXNOC && !QEMPTY(bomb_list); cn++) {
        if (plane_owner == cn)
            continue;
        intown = -1;
        /* Are there ships owned by this country? */
        if (nats[cn] != 0) {
            /* Yes. */
            if (cn != 0) {
                PR(cn, "%s planes spotted over ships in %s\n",
                   cname(plane_owner), xyas(x, y, cn));
                if (opt_HIDDEN)
                    setcont(cn, plane_owner, FOUND_FLY);
            }
            if (unfriendly[cn]) {
                /* They are unfriendly too */
                if (!gotilist[cn]) {
                    getilist(&ilist[cn], cn, bomb_list, esc_list, obomb,
                             oesc);
                    gotilist[cn]++;
                }
                PR(plane_owner, "Flying over %s ships in %s\n",
                   cname(cn), xyas(x, y, plane_owner));
                /* This makes going for ships in harbors tough */
                if (!evaded) {
                    /* We already fired flak up above.  Now we intercept again if we haven't already */
                    /* Flag that we intercepted */
                    intown = 1;
                    /* And now intercept again */
                    ac_intercept(bomb_list, esc_list, &ilist[cn],
                                 cn, x, y);
                }
            }
        }
        /* Are there units owned by this country? */
        if (lnats[cn] != 0) {
            /* Yes. */
            if (cn != 0) {
                PR(cn, "%s planes spotted over land units in %s\n",
                   cname(plane_owner), xyas(x, y, cn));
                if (opt_HIDDEN)
                    setcont(cn, plane_owner, FOUND_FLY);
            }
            if (unfriendly[cn]) {
                /* They are unfriendly too */
                if (!gotilist[cn]) {
                    getilist(&ilist[cn], cn, bomb_list, esc_list, obomb,
                             oesc);
                    gotilist[cn]++;
                }
                PR(plane_owner, "Flying over %s land units in %s\n",
                   cname(cn), xyas(x, y, plane_owner));
                if (!evaded) {
                    if (intown == -1) {
                        /* We haven't intercepted yet, so intercept */
                        ac_intercept(bomb_list, esc_list, &ilist[cn],
                                     cn, x, y);
                    }
                }
            }
        }
    }
    if (mission_flags & P_A)
        free_shiplist(&head);
}

static int
count_non_missiles(struct emp_qelem *list)
{
    struct emp_qelem *qp;
    struct plist *plp;
    int att_count = 0;

    /* don't intercept missiles */
    for (qp = list->q_forw; qp != list; qp = qp->q_forw) {
        plp = (struct plist *)qp;
        if (!(plp->pcp->pl_flags & P_M))
            att_count++;
    }
    return att_count;
}

void
sam_intercept(struct emp_qelem *att_list, struct emp_qelem *def_list,
              natid def_own, natid plane_owner, coord x, coord y,
              int delete_missiles)
{
    struct emp_qelem *aqp;
    struct emp_qelem *anext;
    struct emp_qelem *dqp;
    struct emp_qelem *dnext;
    struct plist *aplp;
    struct plist *dplp;
    int first = 1;

    for (aqp = att_list->q_forw,
         dqp = def_list->q_forw;
         aqp != att_list && dqp != def_list; aqp = anext) {
        anext = aqp->q_forw;
        aplp = (struct plist *)aqp;
        if (aplp->pcp->pl_flags & P_M)
            continue;
        if (aplp->pcp->pl_cost < 1000)
            continue;
        for (; dqp != def_list; dqp = dnext) {
            dnext = dqp->q_forw;
            dplp = (struct plist *)dqp;
            if (!(dplp->pcp->pl_flags & P_M))
                continue;

            if (dplp->plane.pln_range <
                mapdist(x, y, dplp->plane.pln_x, dplp->plane.pln_y)) {
                emp_remque(dqp);
                free(dqp);
                continue;
            }
            if (mission_pln_equip(dplp, 0, P_F, 0) < 0) {
                emp_remque(dqp);
                free(dqp);
                continue;
            }
            if (first) {
                first = 0;
                PR(plane_owner, "%s launches SAMs!\n", cname(def_own));
                PR(def_own, "Launching SAMs at %s planes!\n",
                   cname(plane_owner));
                ac_combat_headers(plane_owner, def_own);
            }
            ac_dog(aplp, dplp);
            dqp = dnext;
            break;
        }
    }
    if (!first) {
        PR(plane_owner, "\n");
        PR(def_own, "\n");
    }
    if (delete_missiles) {
        for (; dqp != def_list; dqp = dnext) {
            dnext = dqp->q_forw;
            dplp = (struct plist *)dqp;
            if (!(dplp->pcp->pl_flags & P_M))
                continue;
            emp_remque(dqp);
            free(dqp);
            continue;
        }
    }
}

static void
ac_intercept(struct emp_qelem *bomb_list, struct emp_qelem *esc_list,
             struct emp_qelem *def_list, natid def_own, coord x, coord y)
{
    struct plnstr *pp;
    struct plist *plp;
    int icount;
    struct emp_qelem *next;
    struct emp_qelem *qp;
    struct emp_qelem int_list;
    int att_count;
    natid plane_owner;
    int dist;

    plp = (struct plist *)bomb_list->q_forw;
    plane_owner = plp->plane.pln_own;

    icount = 0;

    sam_intercept(bomb_list, def_list, def_own, plane_owner, x, y, 0);
    sam_intercept(esc_list, def_list, def_own, plane_owner, x, y, 1);
    if (!(att_count = count_non_missiles(bomb_list) +
          count_non_missiles(esc_list)))
        return;

    emp_initque(&int_list);
    for (qp = def_list->q_forw; qp != def_list; qp = next) {
        next = qp->q_forw;
        plp = (struct plist *)qp;
        pp = &plp->plane;
        /* SAMs interdict separately */
        if (plp->pcp->pl_flags & P_M)
            continue;
        dist = mapdist(x, y, pp->pln_x, pp->pln_y) * 2;
        if (pp->pln_range < dist)
            continue;
        if (mission_pln_equip(plp, 0, P_F, 0) < 0) {
            emp_remque(qp);
            free(qp);
            continue;
        }
        /* got one; delete from def_list, add to int_list */
        emp_remque(qp);
        emp_insque(qp, &int_list);
        pp->pln_mobil -= pln_mobcost(dist, pp, P_F);
        putplane(pp->pln_uid, pp);
        icount++;
        if (icount > att_count)
            break;
    }
    if (icount == 0)
        return;
    PR(plane_owner, "%d %s fighter%s rising to intercept!\n",
       icount, cname(def_own), icount == 1 ? " is" : "s are");
    PR(def_own, "%d fighter%s intercepting %s planes!\n",
       icount, icount == 1 ? " is" : "s are", cname(plane_owner));
    ac_combat_headers(plane_owner, def_own);
    ac_airtoair(esc_list, &int_list);
    ac_airtoair(bomb_list, &int_list);
    PR(plane_owner, "\n");
    PR(def_own, "\n");
}

void
ac_combat_headers(natid plane_owner, natid def_own)
{
    PR(plane_owner,
       " %-10.10s %-10.10s  strength int odds  damage           results\n",
       cname(plane_owner), cname(def_own));
    PR(def_own,
       " %-10.10s %-10.10s  strength int odds  damage           results\n",
       cname(def_own), cname(plane_owner));
}

/*
 * air-to-air combat.
 */
void
ac_airtoair(struct emp_qelem *att_list, struct emp_qelem *int_list)
{
    struct plist *attacker;
    struct plist *interceptor;
    struct emp_qelem *att;
    struct emp_qelem *in;
    int nplanes;
    int more_att;
    int more_int;
    struct emp_qelem *att_next;
    struct emp_qelem *in_next;

    att = att_list->q_forw;
    in = int_list->q_forw;
    more_att = 1;
    more_int = 1;
    if (QEMPTY(att_list) || QEMPTY(int_list)) {
        more_att = 0;
        more_int = 0;
    }
    while (more_att || more_int) {
        in_next = in->q_forw;
        att_next = att->q_forw;
        attacker = (struct plist *)att;

        /* skip missiles. If only missiles left, we're done */
        if (plchr[(int)attacker->plane.pln_type].pl_flags & P_M) {
            att = att_next;
            if (att == att_list) {
                more_att = 0;
                if (QEMPTY(att_list))
                    more_int = 0;
                else
                    att = att->q_forw;
            }
            if (all_missiles(att_list))
                more_att = 0;
            continue;
        }
        interceptor = (struct plist *)in;
        nplanes = attacker->plane.pln_effic;
        if (nplanes > interceptor->plane.pln_effic)
            nplanes = interceptor->plane.pln_effic;
        ac_dog(attacker, interceptor);
        in = in_next;
        att = att_next;
        if (att == att_list) {
            more_att = 0;
            if (QEMPTY(att_list))
                more_int = 0;
            else
                att = att->q_forw;
        }
        if (in == int_list) {
            more_int = 0;
            if (QEMPTY(int_list))
                more_att = 0;
            else
                in = in->q_forw;
        }
    }
}

static int
all_missiles(struct emp_qelem *att_list)
{
    struct emp_qelem *qp;
    struct plist *p;

    qp = att_list->q_forw;
    while (qp != att_list) {
        p = (struct plist *)qp;
        if (!(plchr[(int)p->plane.pln_type].pl_flags & P_M))
            return 0;

        qp = qp->q_forw;
    }
    return 1;
}

static void
ac_dog(struct plist *ap, struct plist *dp)
{
    int att, def;
    double odds;
    int intensity;
    natid att_own, def_own;
    int adam, ddam;
    char mesg[1024];
    char temp[14];

    att_own = ap->plane.pln_own;
    def_own = dp->plane.pln_own;

    PR(att_own, " %3.3s #%-4d  %3.3s #%-4d",
       ap->pcp->pl_name,
       ap->plane.pln_uid, dp->pcp->pl_name, dp->plane.pln_uid);
    if (def_own)
        PR(def_own, " %3.3s #%-4d  %3.3s #%-4d",
           dp->pcp->pl_name,
           dp->plane.pln_uid, ap->pcp->pl_name, ap->plane.pln_uid);
    if (ap->plane.pln_att == 0) {
        att = ap->plane.pln_def * ap->plane.pln_effic / 100;
        att = MAX(att, ap->pcp->pl_def / 2);
    } else {
        att = ap->plane.pln_att * ap->plane.pln_effic / 100;
        att = MAX(att, ap->pcp->pl_att / 2);
    }

    def = dp->plane.pln_def * dp->plane.pln_effic / 100;
    def = MAX(def, dp->pcp->pl_def / 2);

    if ((ap->pcp->pl_flags & P_F) && ap->bombs != 0)
        att -= 2;
    if ((dp->pcp->pl_flags & P_F) && dp->bombs != 0)
        def -= 2;
    att += ap->pcp->pl_stealth / 25.0;
    def += dp->pcp->pl_stealth / 25.0;
    if (att < 1) {
        def += 1 - att;
        att = 1;
    }
    if (def < 1) {
        att += 1 - def;
        def = 1;
    }
    odds = ((double)att / ((double)def + (double)att));
    if (odds <= 0.05)
        odds = 0.05;
    intensity = roll(20) + roll(20) + roll(20) + roll(20) + 1;

    PR(att_own, "   %3d/%-3d %3d  %3.2f  ", att, def, intensity, odds);
    PR(def_own, "   %3d/%-3d %3d  %3.2f  ", def, att, intensity, odds);

    adam = 0;
    ddam = 0;
    while ((intensity--) > 0) {

        if (chance(odds)) {
            ddam += 1;
            if ((dp->plane.pln_effic - ddam) < PLANE_MINEFF)
                intensity = 0;
        } else {
            adam += 1;
            if ((ap->plane.pln_effic - adam) < PLANE_MINEFF)
                intensity = 0;
        }
    }

    if (dp->pcp->pl_flags & P_M)
        ddam = 100;

    PR(att_own, "%3d/%-3d", adam, ddam);
    PR(def_own, "%3d/%-3d", ddam, adam);
    ac_planedamage(ap, def_own, adam, def_own, 1, 0, mesg);
    strncpy(temp, mesg, 14);
    ac_planedamage(dp, att_own, ddam, att_own, 1, 0, mesg);
    PR(att_own, "%-13.13s %-13.13s\n", temp, mesg);
    PR(def_own, "%-13.13s %-13.13s\n", mesg, temp);

    if (opt_HIDDEN) {
        setcont(att_own, def_own, FOUND_FLY);
        setcont(def_own, att_own, FOUND_FLY);
    }
}

/*
 * zap plane associated with plp.
 * Damaging country is "from", damage is "dam".
 * def_own is the country on the other side of the conflict from the plane
 * owner. The only time def_own != from is when the interceptor is getting
 * damaged.
 *
 * NOTE: This routine removes the appropriate plane element from the
 * queue if it gets destroyed.  That means that the caller must assume
 * that the current queue pointer is invalid on return from the ac_planedamage
 * call.  (this has caused bugs in the past)
 */
static void
ac_planedamage(struct plist *plp, natid from, int dam, natid other,
               int checkabort, int show, char *mesg)
{
    struct plnstr *pp;
    int disp;
    char dmess[255];
    int eff;
    struct shpstr ship;
    struct lndstr land;
    natid plane_owner;

    disp = 0;
    pp = &plp->plane;
    plane_owner = pp->pln_own;
    eff = pp->pln_effic;
    sprintf(dmess, " no damage");
    if (dam <= 0) {
        strcpy(mesg, dmess);
        return;
    }
    memset(dmess, 0, sizeof(dmess));
    eff -= dam;
    if (eff < 0)
        eff = 0;
    if (eff < PLANE_MINEFF) {
        sprintf(dmess, " shot down");
        disp = 1;
    } else if (eff < 80 && chance((80 - eff) / 100.0) && checkabort) {
        sprintf(dmess, " aborted @%2d%%", eff);
        disp = 2;
    } else if (show == 0) {
        sprintf(dmess, " cleared");
    }

    if ((plp->pcp->pl_flags & P_M) == 0) {
        if (show) {
            PR(plane_owner, "    %s %s takes %d%s.\n",
               cname(pp->pln_own), prplane(pp), dam, dmess);
            if (other)
                PR(other, "    %s %s takes %d%s.\n",
                   cname(pp->pln_own), prplane(pp), dam, dmess);
        }
    }
    if (show && checkabort == 1) {
        PR(plane_owner, "\n");
        if (other)
            PR(other, "\n");
    }

    pp->pln_effic = eff;
    pp->pln_mobil -= MIN(32 + pp->pln_mobil, dam / 2);
    if (disp == 1) {
        if (from != 0 && (plp->pcp->pl_flags & P_M) == 0)
            nreport(from, N_DOWN_PLANE, pp->pln_own, 1);
        if (pp->pln_ship >= 0) {
            getship(pp->pln_ship, &ship);
            take_plane_off_ship(pp, &ship);
        }
        if (pp->pln_land >= 0) {
            getland(pp->pln_land, &land);
            take_plane_off_land(pp, &land);
        }
        pp->pln_effic = 0;
        putplane(pp->pln_uid, pp);
        emp_remque(&plp->queue);
        free(plp);
    } else if (disp == 2) {
        putplane(pp->pln_uid, pp);
        emp_remque(&plp->queue);
        free(plp);
    } else
        putplane(pp->pln_uid, pp);
    strcpy(mesg, dmess);
}

static void
ac_doflak(struct emp_qelem *list, struct sctstr *from)
{
    int shell;
    int gun;
    natid plane_owner;
    struct plist *plp;

    plp = (struct plist *)list->q_forw;
    plane_owner = plp->plane.pln_own;

    gun = MIN(FLAK_GUN_MAX, from->sct_item[I_GUN]);
    shell = from->sct_item[I_SHELL];
    if (gun > shell * 2) {
        shell += supply_commod(from->sct_own, from->sct_x, from->sct_y,
                               I_SHELL, (gun + 1) / 2 - shell);
        from->sct_item[I_SHELL] = shell;
        putsect(from);
    }
    if (gun > shell * 2)
        gun = shell * 2;

    gun = roundavg(tfact(from->sct_own, 2.0 * gun));
    if (gun > 0) {
        PR(plane_owner, "firing %d flak guns in %s...\n",
           gun, xyas(from->sct_x, from->sct_y, plane_owner));
        if (from->sct_own != 0)
            PR(from->sct_own, "firing %d flak guns in %s...\n",
               gun, xyas(from->sct_x, from->sct_y, from->sct_own));
        ac_fireflak(list, from->sct_own, gun);
    }
}

static void
ac_shipflak(struct emp_qelem *list, coord x, coord y)
{
    struct nstr_item ni;
    struct shpstr ship;
    struct mchrstr *mcp;
    double flak, total, ngun;
    int gun, shell;
    int rel;
    struct plist *plp;
    natid plane_owner;
    natid from;
    int nats[MAXNOC];

    plp = (struct plist *)list->q_forw;
    plane_owner = plp->plane.pln_own;

    memset(nats, 0, sizeof(nats));
    total = ngun = 0;
    snxtitem_xy(&ni, EF_SHIP, x, y);
    while (!QEMPTY(list) && nxtitem(&ni, &ship)) {
        if (ship.shp_own == 0 || ship.shp_own == plane_owner)
            continue;
        mcp = &mchr[(int)ship.shp_type];
        if (mcp->m_flags & M_SUB)
            continue;
        rel = getrel(getnatp(ship.shp_own), plane_owner);
        if (rel > HOSTILE)
            continue;
        shell = gun = 0;
        gun = MIN(ship.shp_item[I_GUN], ship.shp_glim);
        if (gun) {
            shell = ship.shp_item[I_SHELL];
            if (shell <= 0) {
                shell = supply_commod(ship.shp_own, ship.shp_x, ship.shp_y,
                                      I_SHELL, 1);
                ship.shp_item[I_SHELL] = shell;
                putship(ship.shp_uid, &ship);
            }
        }
        if (gun == 0 || shell == 0)
            continue;
        flak = gun * (ship.shp_effic / 100.0);
        ngun += flak;
        total += techfact(ship.shp_tech, flak * 2.0);

        if (!nats[ship.shp_own]) {
            /* First time here, print the message */
            PR(ship.shp_own, "%s planes spotted over ships in %s\n",
               cname(plane_owner), xyas(x, y, ship.shp_own));
            PR(plane_owner, "Flying over %s ships in %s\n",
               cname(ship.shp_own), xyas(x, y, plane_owner));
            nats[ship.shp_own] = 1;
        }
        PR(ship.shp_own, "firing %.0f flak guns from %s...\n",
           flak, prship(&ship));
        from = ship.shp_own;
    }

    /* Limit to FLAK_GUN_MAX guns of average tech factor */
    if (ngun > FLAK_GUN_MAX)
        total *= FLAK_GUN_MAX / ngun;

    gun = roundavg(total);
    if (gun > 0) {
        PR(plane_owner, "Flak!  Ships firing %d flak guns...\n", gun);
        ac_fireflak(list, from, gun);
    }
}

static void
ac_landflak(struct emp_qelem *list, coord x, coord y)
{
    struct nstr_item ni;
    struct lndstr land;
    struct lchrstr *lcp;
    double flak, total, ngun;
    int gun;
    int rel;
    struct plist *plp;
    natid plane_owner;
    natid from;
    int nats[MAXNOC];

    plp = (struct plist *)list->q_forw;
    plane_owner = plp->plane.pln_own;

    memset(nats, 0, sizeof(nats));
    total = ngun = 0;
    snxtitem_xy(&ni, EF_LAND, x, y);
    while (!QEMPTY(list) && nxtitem(&ni, &land)) {
        if (land.lnd_own == 0 || land.lnd_own == plane_owner)
            continue;
        lcp = &lchr[(int)land.lnd_type];
        if ((lcp->l_flags & L_FLAK) == 0 || land.lnd_aaf == 0)
            continue;
        if (land.lnd_ship >= 0 || land.lnd_land >= 0)
            continue;
        rel = getrel(getnatp(land.lnd_own), plane_owner);
        if (rel > HOSTILE)
            continue;
        flak = land.lnd_aaf * 1.5 * land.lnd_effic / 100.0;
        ngun += flak;
        total += techfact(land.lnd_tech, flak * 2.0);

        if (!nats[land.lnd_own]) {
            /* First time here, print the message */
            PR(land.lnd_own, "%s planes spotted over land units in %s\n",
               cname(plane_owner), xyas(x, y, land.lnd_own));
            PR(plane_owner, "Flying over %s land units in %s\n",
               cname(land.lnd_own), xyas(x, y, plane_owner));
            nats[land.lnd_own] = 1;
        }
        PR(land.lnd_own, "firing flak guns from unit %s (aa rating %d)\n",
           prland(&land), land.lnd_aaf);
        from = land.lnd_own;
    }

    /* Limit to FLAK_GUN_MAX guns of average tech factor */
    if (ngun > FLAK_GUN_MAX)
        total *= FLAK_GUN_MAX / ngun;

    gun = roundavg(total);
    if (gun > 0) {
        PR(plane_owner, "Flak!  Land units firing %d flak guns...\n", gun);
        ac_fireflak(list, from, gun);
    }
}

/*
 * Called from shipflak, landflak, and doflak.
 */
static void
ac_fireflak(struct emp_qelem *list, natid from, int guns)
{
    struct plist *plp;
    int n;
    struct emp_qelem *qp;
    struct emp_qelem *next;
    char msg[255];

    plp = (struct plist *)list->q_forw;

    for (qp = list->q_forw; qp != list; qp = next) {
        next = qp->q_forw;
        plp = (struct plist *)qp;
        n = ac_flak_dam(guns, plp->plane.pln_def, plp->pcp->pl_flags);
        ac_planedamage(plp, from, n, 0, 2, 1, msg);
    }
}

/*
 * Calculate flak damage
 */
int
ac_flak_dam(int guns, int def, int pl_flags)
{
    int flak, dam;
    float mult;
    /*                             <-7      -7     -6     -5     -4 */
    static float flaktable[18] = { 0.132f, 0.20f, 0.20f, 0.25f, 0.30f,
    /*    -3     -2     -1      0     +1     +2     +3     +4 */
         0.35f, 0.40f, 0.45f, 0.50f, 0.50f, 0.55f, 0.60f, 0.65f,
    /*    +5    +6     +7     +8    >+8 */
         0.70f,0.75f, 0.80f, 0.85f, 1.1305f };
    enum { FLAK_MAX = sizeof(flaktable)/sizeof(flaktable[0]) - 1 };

    flak = guns - def;
    if ((pl_flags & P_T) == 0)
        flak--;
    if (pl_flags & P_X)
        flak -= 2;
    if (pl_flags & P_H)
        flak -= 1;

    if (flak > 8)
        mult = flaktable[FLAK_MAX];
    else if (flak < -7)
        mult = flaktable[0];
    else {
        flak += 8;
        mult = flaktable[flak];
    }
    mult *= flakscale;
    dam = (int)((roll(8) + 2) * mult);
    if (dam > 100)
        dam = 100;
    return dam;
}

/*
 * See if this plane is flying in this list
 */
int
ac_isflying(struct plnstr *plane, struct emp_qelem *list)
{
    struct emp_qelem *qp;
    struct emp_qelem *next;
    struct plnstr *pp;
    struct plist *plp;

    if (!list)
        return 0;
    for (qp = list->q_forw; qp != list; qp = next) {
        next = qp->q_forw;
        plp = (struct plist *)qp;
        pp = &plp->plane;
        if (plane->pln_uid == pp->pln_uid)
            return 1;
    }
    return 0;
}


/*
 * Get a list of planes available for interception duties.
 */
static void
getilist(struct emp_qelem *list, natid own, struct emp_qelem *a,
         struct emp_qelem *b, struct emp_qelem *c, struct emp_qelem *d)
{
    struct plchrstr *pcp;
    struct plnstr plane;
    struct nstr_item ni;
    struct plist *ip;

    emp_initque(list);
    snxtitem_all(&ni, EF_PLANE);
    while (nxtitem(&ni, &plane)) {
        if (plane.pln_own != own)
            continue;
        pcp = &plchr[(int)plane.pln_type];
        if ((pcp->pl_flags & P_F) == 0)
            continue;
        if (plane.pln_mission != 0)
            continue;
        if (plane.pln_mobil <= 0)
            continue;
        if (plane.pln_effic < 40)
            continue;
        if (!pln_airbase_ok(&plane, 0, 0))
            continue;
        /* Finally, is it in the list of planes already in
           flight? */
        if (ac_isflying(&plane, a))
            continue;
        if (ac_isflying(&plane, b))
            continue;
        if (ac_isflying(&plane, c))
            continue;
        if (ac_isflying(&plane, d))
            continue;
        /* got one! */
        ip = malloc(sizeof(*ip));
        ip->bombs = 0;
        ip->misc = 0;
        ip->pcp = &plchr[(int)plane.pln_type];
        ip->plane = plane;
        emp_insque(&ip->queue, list);
    }
}

static int
do_evade(struct emp_qelem *bomb_list, struct emp_qelem *esc_list)
{
    struct emp_qelem *qp;
    double evade;
    struct plist *plp;

    evade = 100.0;
    for (qp = bomb_list->q_forw; qp != bomb_list; qp = qp->q_forw) {
        plp = (struct plist *)qp;
        if (evade > plp->pcp->pl_stealth / 100.0)
            evade = plp->pcp->pl_stealth / 100.0;
    }
    for (qp = esc_list->q_forw; qp != esc_list; qp = qp->q_forw) {
        plp = (struct plist *)qp;
        if (evade > plp->pcp->pl_stealth / 100.0)
            evade = plp->pcp->pl_stealth / 100.0;
    }

    if (chance(evade))
        return 1;

    return 0;
}

---