/* The movement-related actions of Xconq.
   Copyright (C) 1987-1989, 1991-1998 Stanley T. Shebs.

Xconq 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, or (at your option)
any later version.  See the file COPYING.  */

#include "conq.h"
extern int carryable PARAMS ((int u));
extern int accelerable PARAMS ((int u));
extern int accelerator PARAMS ((int u1, int u2));
#include "kernel.h"
#include "kpublic.h"

enum {
    over_nothing = 0,
    over_own = 1,
    over_border = 2,
    over_all = 3
};

/* We can't declare all the action functions as static because some of them
   are in other files, but don't let them be visible to all files. */

#undef  DEF_ACTION
#define DEF_ACTION(name,code,args,prepfn,netprepfn,DOFN,checkfn,ARGDECL,doc)  \
  extern int DOFN PARAMS (ARGDECL);

#include "action.def"

extern int retreating;
extern int retreating_from;

/* Movement actions. */

/* Record a move action as the next to do. */

int
prep_move_action(unit, unit2, x, y, z)
Unit *unit, *unit2;
int x, y, z;
{
    if (unit == NULL || unit->act == NULL || unit2 == NULL)
      return FALSE;
    unit->act->nextaction.type = ACTION_MOVE;
    unit->act->nextaction.args[0] = x;
    unit->act->nextaction.args[1] = y;
    unit->act->nextaction.args[2] = z;
    unit->act->nextaction.actee = unit2->id;
    return TRUE;
}

int
net_prep_move_action(unit, unit2, x, y, z)
Unit *unit, *unit2;
int x, y, z;
{
    int rslt;

    rslt = prep_move_action(unit, unit2, x, y, z);
    broadcast_next_action(unit);
    return rslt;
}

/* The basic act of moving.  This attempts to move and maybe fails,
   but takes no corrective action.  Note that this requires space in
   the destination cell, will not board, attack, etc - all that is
   task- and plan-level behavior. */

int
do_move_action(unit, unit2, nx, ny, nz)
Unit *unit, *unit2;
int nx, ny, nz;
{
    int u, u2, nu2, t, rslt, speed, mpcost, acpcost, ox, oy, oz, ot, dist;
    int nummoves, dirs[NUMDIRS], numdirs, i, ix, iy, ndist;

    u = unit->type;  u2 = unit2->type;
    t = terrain_at(nx, ny);
    ox = unit2->x;  oy = unit2->y;  oz = unit2->z;
    ot = terrain_at(ox, oy);
    speed = 100;
    mpcost = 1;
    dist = distance(ox, oy, nx, ny);
    if (dist == 0) {
	/* Change of altitude within same cell and/or transport departure. */
	if (unit->transport != NULL && nz == unit->z) {
	    mpcost = move_unit(unit2, nx, ny);
	} else {
	    unit2->z = nz;
	    /* (should do more stuff - LOS view might have changed) */
	}
	acpcost = 1;
	nummoves = 1;
	rslt = A_ANY_DONE;
    } else if (dist == 1) {
	/* Movement to an adjacent cell. */
	if (!inside_area(nx, ny)) {
	    kill_unit(unit2, H_UNIT_LEFT_WORLD);
	    rslt = A_ANY_DONE;
	} else if (ut_vanishes_on(u2, t) && !can_move_via_conn(unit2, nx, ny)) {
	    kill_unit(unit2, H_UNIT_VANISHED);
	    rslt = A_MOVE_UNIT_GONE;
	} else if (ut_wrecks_on(u2, t) && !can_move_via_conn(unit2, nx, ny)) {
	    if (u_wrecked_type(u2) == NONUTYPE) {
		/* Occupants always die if the wrecked unit disappears. */
		kill_unit(unit, H_UNIT_WRECKED);
	    } else {
		/* Wreck the unit.  Note that we want to do the wrecking even
		   if the unit will vanish, so that occupants can escape if
		   allowed for. */
		if (!ut_vanishes_on(u_wrecked_type(u2), t)) {
		    speed = unit_speed(unit2, nx, ny);
		    mpcost = move_unit(unit2, nx, ny);
		}
		wreck_unit(unit2);
		/* Now make it go away, taking unlucky occupants with. */
		if (ut_vanishes_on(nu2, t)) {
		    kill_unit(unit2, H_UNIT_VANISHED);
		}
	    }
	    rslt = A_MOVE_UNIT_GONE;
	} else if (ut_vanishes_on(u2, ot)
		   && (unit->transport == NULL
		       || uu_ferry_on_leave(unit->transport->type, u2) < over_own)
		   && !can_move_via_conn(unit2, nx, ny)) {
	    /* This case is if the unit is already on a connection in
	       hostile terrain and tries to move to hospitable terrain
	       without using a bridge, or if it is in a transport that
	       won't ferry across hostile terrain. */
	    kill_unit(unit2, H_UNIT_VANISHED);
	    rslt = A_MOVE_UNIT_GONE;
	} else if (ut_wrecks_on(u2, ot)
		   && (unit->transport == NULL
		       || uu_ferry_on_leave(unit->transport->type, u2) < over_own)
		   && !can_move_via_conn(unit2, nx, ny)) {
	    if (u_wrecked_type(u2) == NONUTYPE) {
		/* Occupants always die if the wrecked unit disappears. */
		kill_unit(unit, H_UNIT_WRECKED);
	    } else {
		/* Wreck the unit.  Note that we want to do the wrecking even
		   if the unit will vanish, so that occupants can escape if
		   allowed for. */
		wreck_unit(unit2);
		/* Now make it go away, taking unlucky occupants with. */
		if (ut_vanishes_on(nu2, ot)) {
		    kill_unit(unit2, H_UNIT_VANISHED);
		}
	    }
	    rslt = A_MOVE_UNIT_GONE;
	} else {
	    speed = unit_speed(unit2, nx, ny);
	    mpcost = move_unit(unit2, nx, ny);
	    /* ZOC move cost is added after action is done. */
	    mpcost += zoc_move_cost(unit2, ox, oy, oz);
	    rslt = A_ANY_DONE;
	}
	if (alive(unit)) {
	    if (speed > 0) {
		acpcost = (mpcost * 100) / speed;
	    } else {
		acpcost = 1;
	    }
	}
	nummoves = 1;
    } else {
	/* Movement by a distance of at least 2.  This is similar to
	   the move-to task, but the unit uses up only mp and doesn't
	   get to contemplate directions. */
	mpcost = 0;
	acpcost = 0;
	nummoves = 0;
	while (dist > 0) {
	    numdirs = choose_move_dirs(unit2, nx, ny, TRUE,
				       plausible_move_dir, sort_directions, dirs);
	    if (numdirs == 0)
	      break;
	    for (i = 0; i < numdirs; ++i) {
		point_in_dir(unit->x, unit->y, dirs[i], &ix, &iy);
		if (1 /* would be successful */) {
		    ox = unit2->x;  oy = unit2->y;  oz = unit2->z;
		    speed = unit_speed(unit2, ix, iy);
		    mpcost += move_unit(unit2, ix, iy);
		    mpcost += zoc_move_cost(unit2, ox, oy, oz);
		    if (alive(unit)) {
			if (speed > 0) {
			    acpcost += (mpcost * 100 * 100) / speed;
			} else {
			    acpcost += 1;
			}
		    }
		    break;
		}
	    }
	    ndist = distance(unit2->x, unit2->y, nx, ny);
	    if (ndist >= dist)
	      break;
	    dist = ndist;
	    ++nummoves;
	}
	/* Scale accumulated cost back down. */
	acpcost /= 100;
    }
    if (alive(unit)) {
	acpcost = max(acpcost, u_acp_to_move(u2));
	if (acpcost < 1)
	  acpcost = 1;
	use_up_acp(unit, acpcost);
    }
    /* Count the unit as having actually moved. */
    if (alive(unit2) && unit2->act)
      unit2->act->actualmoves += nummoves;
    return rslt;
}

int
check_move_action(unit, unit2, nx, ny, nz)
Unit *unit, *unit2;
int nx, ny, nz;
{
    int u, u2, u3, ox, oy, oz, acp, acpavail, mpavail, totcost, m, speed;
    int maxmpavail;

    if (!in_play(unit))
      return A_ANY_ERROR;
    if (!in_play(unit2))
      return A_ANY_ERROR;
    /* Note that edge cell dests (used to leave the world) are allowed. */
    if (!in_area(nx, ny))
      return A_ANY_ERROR;
    u = unit->type;  u2 = unit2->type;
    ox = unit2->x;  oy = unit2->y;  oz = unit2->z;
    acp = u_acp_to_move(u2);
    if (acp < 1)
      return A_ANY_CANNOT_DO;
    acpavail = unit->act->acp;
    /* If this action is a part of retreating, add more acp to represent the
       motivational power of needing to run away... */
    if (retreating && unit == unit2) {
	if (retreating_from != NONUTYPE) {
	    acpavail += uu_acp_retreat(u2, retreating_from);
	}
	/* (should not have to modify the unit, but succeeding calls need this) */
	unit->act->acp = acpavail;
    }
    if (!can_have_enough_acp(unit, acp))
      return A_ANY_CANNOT_DO;
    if (!has_enough_acp(unit, acp))
      return A_ANY_NO_ACP;
    if (!has_supply_to_act(unit2))
      return A_ANY_NO_MATERIAL;
    /* Destination is outside the world and we're not allowed to leave. */
    if (!inside_area(nx, ny) && u_mp_to_leave_world(u2) < 0)
	return A_MOVE_CANNOT_LEAVE_WORLD;
    /* Check if the destination is within our move range. */
    /* (also check for and maybe allow border slides here) */
    if (distance(ox, oy, nx, ny) > u_move_range(u2))
      return A_ANY_TOO_FAR;
    if (nz > 0)
      return A_ANY_TOO_FAR;
    /* Check if the destination is in a blocking ZOC. */
    if (in_blocking_zoc(unit, nx, ny, nz))
      return A_ANY_ERROR;
    /* Now start looking at the move costs. */
    u3 = (unit2->transport ? unit2->transport->type : NONUTYPE);
    totcost = total_move_cost(u2, u3, ox, oy, oz, nx, ny, nz);
    speed = unit_speed(unit2, nx, ny);
    /* Check if unit can possibly have enough mp for the move. */
    maxmpavail =
      (((u_acp_max(u) > 0 ? u_acp_max(u) : u_acp(u)) - u_acp_min(u)) * speed)
      / 100
      + u_free_mp(u2);
    if (maxmpavail < totcost)
      return A_ANY_CANNOT_DO; /* (should have a move_cannot_do) */
    /* Now check if unit has enough mp this turn. */
    mpavail = (unit->act->acp * speed) / 100;
    /* take into account acp-min in computing mpavail; Massimo */
    if (u_acp_min(u) < 0)
      mpavail = ((unit->act->acp - u_acp_min(u)) * speed) / 100;
    /* Zero mp always disallows movement, unless intra-cell. */
    if (mpavail <= 0 && !(ox == nx && oy == ny && oz == nz))
      return A_MOVE_NO_MP;
    /* The free mp might get us enough moves, so add it before comparing. */
    if (mpavail + u_free_mp(u2) < totcost)
      return A_MOVE_NO_MP;
    /* If destination is too small or already full, we can't move into it. */
    if ((nz & 1) == 0) {
	if (!can_occupy_cell(unit2, nx, ny))
	  return A_MOVE_DEST_FULL;
    } else {
	if (!can_occupy_conn(unit2, nx, ny, nz))
	  return A_MOVE_DEST_FULL;
    }
    /* We have to have a minimum level of supply to be able to move. */
    for_all_material_types(m) {
	if (unit2->supply[m] < um_to_move(u2, m))
	  return A_ANY_NO_MATERIAL;
    }
    return A_ANY_OK;
}

int
can_move_via_conn(unit, nx, ny)
Unit *unit;
int nx, ny;
{
    int c, dir;

    if (numconntypes == 0)
      return FALSE;
    for_all_terrain_types(c) {
	    if (t_is_connection(c)
		&& aux_terrain_defined(c)
		&& (dir = closest_dir(nx - unit->x, ny - unit->y)) >= 0
		&& connection_at(unit->x, unit->y, dir, c)
		&& !ut_vanishes_on(unit->type, c)
		&& !ut_wrecks_on(unit->type, c)) {
		return TRUE;
	    }
    }
    return FALSE;
}

int
unit_speed(unit, nx, ny)
Unit *unit;
int nx, ny;
{
    int u = unit->type, speed, x = unit->x, y = unit->y, angle, windval;
    int occeff, totocceff, totoccdenom;
    Unit *occ;
    
    speed = u_speed(u);
    if (unit->hp < u_hp_max(u) && u_speed_damage_effect(u) != lispnil) {
	speed = damaged_value(unit, u_speed_damage_effect(u), speed);
    }
    if (winds_defined() && u_speed_wind_effect(u) != lispnil) {
	angle = angle_with(closest_dir(nx - x, nx - y), wind_dir_at(x, y));
	windval = wind_value(unit, angle, wind_force_at(x, y), u_speed_wind_effect(u), 10000);
	speed = (speed * windval) / 100;
    }
    if (unit->occupant /* and any occupant speed effects */) {
        totocceff = 100;
        totoccdenom = 100;
    	for_all_occupants(unit, occ) {
	    if (completed(occ)) {
		occeff = uu_speed_occ_effect(u, occ->type);
		if (occeff != 100) {
		    totocceff *= occeff;
		    totoccdenom *= 100;
		}
	    }
    	}
    	speed = (speed * totocceff) / totoccdenom;
    }
    /* Clip to limits. */
    speed = max(speed, u_speed_min(u));
    speed = min(speed, u_speed_max(u));
    return speed;
}

/* Compute and return value for a damaged unit, using a list of (hp val) pairs
   and interpolating between them. */

int
damaged_value(unit, effect, maxval)
Unit *unit;
Obj *effect;
int maxval;
{
    int u, err, rslt;

    u = unit->type;
    err = interpolate_in_list_ext(unit->hp, effect, 0, 0, 0, 0, u_hp(u), maxval, &rslt);
    if (err != 0) {
	run_warning("cannot get damaged speed for %s at hp %d, using 100",
		    u_type_name(u), unit->hp);
	rslt = 100;
    }
    return rslt;
}

/* Compute and return the wind's effect on a unit, using a list of lists
   and interpolating between them. */

int
wind_value(unit, angle, force, effect, maxval)
Unit *unit;
int angle, force, maxval;
Obj *effect;
{
    int err, rslt;
    Obj *rest, *head, *key, *val;

    for (rest = effect; rest != lispnil; rest = cdr(rest)) {
	head = car(rest);
	key = car(head);
	if ((numberp(key) && angle == c_number(key))
	    || (symbolp(key))
	    || (consp(key) && number_member(angle, key))) {
	    val = cadr(head);
	    if (numberp(val))
	      return c_number(val);
	    else {
		err = interpolate_in_list(force, val, &rslt);
		if (err == 0) {
		    return rslt;
		} else {
		    run_warning("no value for wind angle=%d force=%d", angle, force);
		    return maxval;
		}
	    }
	}
    }
    return maxval;
}

int
number_member(x, lis)
int x;
Obj *lis;
{
    Obj *rest;

    if (lis == lispnil) {
	return FALSE;
    } else if (!consp(lis)) {
	/* should probably be an error of some sort */
	return FALSE;
    }
    for (rest = lis; rest != lispnil; rest = cdr(rest)) {
	if (numberp(car(rest)) && x == c_number(car(rest)))
	  return TRUE;
    }
    return FALSE;
}

/* Conduct the actual move (used in both normal moves and some
   combat).  Note that the new x,y may be the same as the old; this
   will happen if an occupant is getting off a transport but staying
   in the same cell. */

int
move_unit(unit, nx, ny)
Unit *unit;
int nx, ny;
{
    int u = unit->type, u3, ox = unit->x, oy = unit->y, oz = unit->z;
    int nz = oz;
    SideMask observers;

    u3 = (unit->transport ? unit->transport->type : NONUTYPE);
    maybe_lose_track(unit, nx, ny);
    /* Disappear from the old location and appear at the new one. */
    if (unit->transport == NULL /* should be unconditional, but bugs still */) {
	change_cell(unit, nx, ny);
    } else {
	leave_cell(unit);
	enter_cell(unit, nx, ny);
    }
    if (0 /* record movement */) {
	observers = add_side_to_set(unit->side, NOSIDES);
	/* (should let other watching sides see event also) */
	record_event(H_UNIT_MOVED, observers, unit->id, nx, ny);
    }
    maybe_track(unit);
    /* Movement may set off other people's alarms. */
    maybe_react_to_move(unit, ox, oy);
    /* Might have auto-detonations in response. */
    if (max_detonate_on_approach_range >= 0) {
	detonate_on_approach_around(unit);
	/* A detonation might have been fatal, get out now if so. */
	if (!alive(unit))
	  return 1;
    }
    /* The people at the new location may change sides immediately. */
    if (people_sides_defined()
	&& any_people_side_changes
	&& probability(people_surrender_chance(u, nx, ny))) {
	change_people_side_around(nx, ny, u, unit->side);
    }
    if (control_sides_defined()) {
	if (ut_control_range(u, terrain_at(nx, ny)) >= 0) {
	    change_control_side_around(nx, ny, u, unit->side);
	}
    }
    /* Use up supplies as directed. */
    consume_move_supplies(unit);
    /* a hack */
    update_cell_display(unit->side, ox, oy, TRUE);
    /* Always return the mp cost, even if the mover died. */
    return total_move_cost(u, u3, ox, oy, oz, nx, ny, nz);
}

void
change_control_side_around(x, y, u, side)
int x, y, u;
Side *side;
{
    int con = control_side_at(x, y), s = side_number(side), dir, x1, y1;
    Side *oldside, *side2;

    if (con != NOCONTROL
        && con != s
        && !trusted_side(side, side_n(con))) {
        oldside = side_n(con);
	set_control_side_at(x, y, s);
	if (side) {
	    for_all_sides(side2) {
		if (side == side2 || trusted_side(side, side2)) {
		    add_cover(side2, x, y, 1);
		}
	    }
	}
	update_cell_display_all_sides(x, y, TRUE);
	for_all_directions(dir) {
	    if (interior_point_in_dir(x, y, dir, &x1, &y1)) {
		update_cell_display_all_sides(x1, y1, TRUE);
	    }
	}
	/* Previous side(s) lose free coverage. */
	for_all_sides(side2) {
	    if (!trusted_side(side, side2)
		&& (oldside == side2 || trusted_side(oldside, side2))) {
		add_cover(side2, x, y, -1);
		/* Update coverage display. */
		update_cell_display(side2, x, y, 36);
	   }
	}
    }
    /* (should add ability to change adjacent cells also) */
}

int
can_move_at_all(unit)
Unit *unit;
{
    return u_speed(unit->type) > 0;
}

/* This is true if the given location is in a blocking zoc for the unit. */

static int tmprslt;

static void test_blocking_zoc PARAMS ((int x, int y));

int
in_blocking_zoc(unit, x, y, z)
Unit *unit;
int x, y, z;
{
    int u = unit->type, t = terrain_at(x, y), dir, x1, y1, u2, range;
    Unit *unit2;

    if (max_zoc_range < 0)
      return FALSE;
    if (max_zoc_range >= 0) {
	for_all_stack(x, y, unit2) {
	    u2 = unit2->type;
	    range = zoc_range(unit2, u);
	    if (range >= 0
		&& is_active(unit2)
		&& !trusted_side(unit->side, unit2->side) /* should make a better test */
		&& uu_mp_to_enter_own(unit->type, u2) < 0
		&& ut_zoc_into(u2, t)
		&& ut_zoc_from_terrain(u2, t) > 0)
	      return TRUE;
	}
    }
    if (max_zoc_range >= 1) {
	for_all_directions(dir) {
	    if (point_in_dir(x, y, dir, &x1, &y1)) {
		for_all_stack(x, y, unit2) {
		    u2 = unit2->type;
		    range = zoc_range(unit2, u);
		    if (range >= 1
			&& is_active(unit2)
			&& unit_blockable_by(unit, unit2)
			&& ut_zoc_into(u2, t)
			&& ut_zoc_from_terrain(u2, terrain_at(x1, y1)) > 0)
		      return TRUE;
		}
	    }
	}
    }
    if (max_zoc_range >= 2) {
	tmprslt = FALSE;
	tmpunit = unit;
	apply_to_ring(x, y, 2, max_zoc_range, test_blocking_zoc);
	return tmprslt;
    }
    return FALSE;
}

static void
test_blocking_zoc(x, y)
int x, y;
{
    int u = tmpunit->type, u2, t = terrain_at(x, y), range;
    Unit *unit2;

    for_all_stack(x, y, unit2) {
	u2 = unit2->type;
	range = zoc_range(unit2, u);
	if (range >= distance(x, y, tmpunit->x, tmpunit->y)
	    && is_active(unit2)
	    && unit_blockable_by(tmpunit, unit2)
	    && ut_zoc_into(u2, terrain_at(tmpunit->x, tmpunit->y))
	    && ut_zoc_from_terrain(u2, t) > 0)
          tmprslt = TRUE;
    }
}

/* This is true if unit2 wants to block unit from moving. */

int
unit_blockable_by(unit, unit2)
Unit *unit, *unit2;
{
    return (!trusted_side(unit->side, unit2->side) /* should make a better test */
	    && uu_mp_to_enter_zoc(unit->type, unit2->type) < 0);
}

/* Compute the number of move points that will be needed to do the given
   move. */

int
total_move_cost(u, u2, x1, y1, z1, x2, y2, z2)
int u, u2, x1, y1, z1, x2, y2, z2;
{
    int cost, ferry, b, c, conncost, dist, dir;

    if (z1 != 0 || z2 != 0) {
    	/* should write these calcs eventually */
    }
    dist = distance(x1, y1, x2, y2);
    if (dist == 0) {
	if (z2 != z1) {
	    /* (should have parms for up/down in same cell) */
	    return 1;
	} else {
    	    /* Unit is leaving a transport and moving into the open here;
    	       free of charge. */
    	    return 0;
    	}
    } else if (dist == 1) {
    	/* (fall through) */
    } else {
    	/* Border slide or multiple cell move. */
    	/* (should implement) */
    	return dist;
    }
    cost = 0;
    ferry = 0;
    if (u2 != NONUTYPE) {
	/* Charge for leaving the transport. */
    	cost += uu_mp_to_leave(u, u2);
    	/* See what type of ferrying we're going to get. */
    	ferry = uu_ferry_on_leave(u2, u);
    }
    if (ferry < over_own) {
    	cost += ut_mp_to_leave(u, terrain_at(x1, y1));
    }
    if (numbordtypes > 0 && ferry < over_border) {
	/* Add any necessary border crossing costs. */
	dir = closest_dir(x2 - x1, y2 - y1);
	if (dir >= 0) {
	    for_all_terrain_types(b) {
		if (t_is_border(b)
		    && aux_terrain_defined(b)
		    && border_at(x1, y1, dir, b)) {
		    cost += ut_mp_to_enter(u, b);
		}
	    }
	}
    }
    if (ferry < over_all) {
	cost += ut_mp_to_enter(u, terrain_at(x2, y2));
    }
    /* Use a connection traversal if it would be cheaper.  This is
       only automatic if the connection on/off costs are small enough,
       otherwise the unit has to do explicit actions to get on the
       connection and off again. */
    if (numconntypes > 0) {
	/* Try each connection type to see if it's better. */
	dir = closest_dir(x2 - x1, y2 - y1);
	if (dir >= 0) {
	    for_all_terrain_types(c) {
		if (t_is_connection(c)
		    && aux_terrain_defined(c)
		    && connection_at(x1, y1, dir, c)) {
		    conncost = ut_mp_to_enter(u, c)
		      + ut_mp_to_traverse(u, c)
			+ ut_mp_to_leave(u, c);
		    cost = min(cost, conncost);
		}
	    }
	}
    }
    /* The cost of leaving the world is always an addon. */
    if (!inside_area(x2, y2)) {
    	cost += u_mp_to_leave_world(u);
    }
    /* Any (inter-cell) movement must always cost at least 1 mp. */
    if (cost < 1)
      cost = 1;
    return cost;
}

int
zoc_range(unit, u2)
Unit *unit;
int u2;
{
    int u = unit->type;

    return (uu_zoc_range(u, u2)
	    * ut_zoc_from_terrain(u, terrain_at(unit->x, unit->y))) / 100;
}

static int tmpmpcost, tmpox, tmpoy;

static void zoc_cost_fn PARAMS ((int x, int y));

int
zoc_move_cost(unit, ox, oy, oz)
Unit *unit;
int ox, oy, oz;
{
    int u = unit->type, u2, t1, t2, cost, mpcost, x, y, dir, x1, y1, range;
    Unit *unit2;

    /* If this is negative, ZOCs are not part of this game. */
    if (max_zoc_range < 0)
      return 0;
    if (!in_play(unit))
      return 0;
    mpcost = 0;
    x = unit->x;  y = unit->y;
    t1 = terrain_at(ox, oy);
    t2 = terrain_at(x, y);
    if (max_zoc_range == 0 || max_zoc_range == 1) {
        /* ZOCs of units in old cell. */
	for_all_stack(ox, oy, unit2) {
	    u2 = unit2->type;
            range = zoc_range(unit2, u);
	    if (is_active(unit2)
		&& unit2->side != unit->side
		&& range >= 0
		&& ut_zoc_into(u2, t1)
		/* should account for from-terrain also */
		)
	      mpcost = max(mpcost, uu_mp_to_leave_zoc(u, u2));
	}
	/* ZOCs of units in new cell. */
	for_all_stack(x, y, unit2) {
	    u2 = unit2->type;
            range = zoc_range(unit2, u);
	    if (is_active(unit2)
		&& unit2->side != unit->side
		&& range >= 0
		&& ut_zoc_into(u2, t2))
	      mpcost = max(mpcost, uu_mp_to_enter_zoc(u, u2));
	}
    }
    if (max_zoc_range > 0) {
	if (max_zoc_range == 1) {
	    /* ZOCs may be into adjacent cells. */
	    /* Look for everybody that was exerting ZOC into the old
               location. */
	    /* (should calc with stacked units also) */
	    for_all_directions(dir) {
		if (point_in_dir(ox, oy, dir, &x1, &y1)) {
		    for_all_stack(x1, y1, unit2) {
			u2 = unit2->type;
			range = zoc_range(unit2, u);
			if (in_play(unit2) /* should be is_active? */
			    && unit2->side != unit->side  /* and unfriendly */
			    && range >= 1
			    && ut_zoc_into(u2, t1)) {
			    if (1 /* leaving zoc */) {
				cost = uu_mp_to_leave_zoc(u, u2);
			    } else {
				cost = uu_mp_to_traverse_zoc(u, u2);
			    }
			    mpcost = max(mpcost, cost);
			}
			/* (and occupants?) */
		    }
		}
	    }
	    /* Look for everybody that is now exerting ZOC into the
               new location. */
	    /* (should calc with stacked units also) */
	    for_all_directions(dir) {
		if (point_in_dir(x, y, dir, &x1, &y1)) {
		    for_all_stack(x1, y1, unit2) {
			u2 = unit2->type;
			range = zoc_range(unit2, u);
			if (is_active(unit2)
			    && unit2->side != unit->side  /* and unfriendly */
			    && range >= 1
			    && ut_zoc_into(u2, t2)) {
			    if (1 /* entering zoc */) {
				cost = uu_mp_to_enter_zoc(u, u2);
			    } else {
				cost = uu_mp_to_traverse_zoc(u, u2);
			    }
			    mpcost = max(mpcost, cost);
			}
			/* (and occupants?) */
		    }
		}
	    }
	} else {
	    tmpmpcost = mpcost;
	    tmpox = ox;  tmpoy = oy;
	    tmpunit = unit;
	    apply_to_area(ox, oy, max_zoc_range + distance(ox, oy, x, y),
			  zoc_cost_fn);
	    mpcost = tmpmpcost;
	}
    }
    return mpcost;
}

static int
allowed_in_zoc(unit, unit2)
Unit *unit, *unit2;
{
    /* should make a better test */
    return trusted_side(unit->side, unit2->side);
}

static void
zoc_cost_fn(x, y)
int x, y;
{
    int u, u2, x0, y0, dist, odist, range, cost;
    Unit *unit2;

    u = tmpunit->type;
    x0 = tmpunit->x;  y0 = tmpunit->y;
    dist = distance(x0, y0, x, y);
    odist = distance(tmpox, tmpoy, x, y);
    for_all_stack(x, y, unit2) {
	if (is_active(unit2)) {
	    u2 = unit2->type;
	    range = zoc_range(unit2, u);
	    if (dist <= range) {
		if (odist <= range) {
		    /* Traversing the unit2's ZOC. */
		    if (!allowed_in_zoc(tmpunit, unit2)
			&& ut_zoc_into(u2, terrain_at(x0, y0))) {
			cost = uu_mp_to_traverse_zoc(u, u2);
			tmpmpcost = max(tmpmpcost, cost);
		    }
		} else {
		    /* Entering the unit2's ZOC. */
		    if (!allowed_in_zoc(tmpunit, unit2)
			&& ut_zoc_into(u2, terrain_at(x0, y0))) {
			cost = uu_mp_to_enter_zoc(u, u2);
			tmpmpcost = max(tmpmpcost, cost);
		    }
		}
	    } else {
		if (odist <= range) {
		    /* Leaving the unit2's ZOC. */
		    if (!allowed_in_zoc(tmpunit, unit2)
			&& ut_zoc_into(u2, terrain_at(x0, y0))) {
			cost = uu_mp_to_leave_zoc(u, u2);
			tmpmpcost = max(tmpmpcost, cost);
		    }
		}
	    }
	}
    }
}

/* This is a hook to handle any reactions to the unit's successful move. */

int
maybe_react_to_move(unit, ox, oy)
Unit *unit;
int ox, oy;
{
    return 0;
}

static void
try_detonate_on_approach(x, y)
int x, y;
{
    int dist;
    Unit *unit;

    dist = distance(tmpunit->x, tmpunit->y, x, y);
    for_all_stack(x, y, unit) {
	if (unit->side != tmpunit->side
	    && dist <= uu_detonate_approach_range(unit->type, tmpunit->type)
	    /* (should make doctrine-based decision about whether to go off) */
	    && !was_detonated(unit)
	    ) {
	    detonate_unit(unit, unit->x, unit->y, unit->z);
	}
    }
}

void
detonate_on_approach_around(unit)
Unit *unit;
{
    int maxrange;

    tmpunit = unit;
    apply_to_area(unit->x, unit->y, max_detonate_on_approach_range, try_detonate_on_approach);
    maxrange = max(max_u_detonate_effect_range, max_t_detonate_effect_range) + max_detonate_on_approach_range;
    reckon_damage_around(unit->x, unit->y, maxrange);
}

/* Use up the supply consumed by a successful move.  Also, the move might
   have used up essentials and left the unit without its survival needs,
   so check for this case and maybe hit/kill the unit. */

void  
consume_move_supplies(unit)
Unit *unit;
{
    int u = unit->type, m, checkstarve = FALSE;
    
    for_all_material_types(m) {
	if (um_consumption_per_move(u, m) > 0) {
	    unit->supply[m] -= um_consumption_per_move(u, m);
	    /* Don't let supply go below zero. */
	    if (unit->supply[m] <= 0) {
		unit->supply[m] = 0;
		checkstarve = TRUE;
	    }
	}
    }
    if (checkstarve)
      maybe_starve(unit, FALSE);
    /* Trigger any supply alarms. */
    if (alive(unit)
    	&& unit->plan
    	&& !unit->plan->supply_is_low
    	&& past_halfway_point(unit)
    	) {
    	unit->plan->supply_is_low = TRUE;
    	update_unit_display(unit->side, unit, TRUE); 
    }
}

/* Movement into another unit. */

/* Record an enter action as the next to do. */

int
prep_enter_action(unit, unit2, unit3)
Unit *unit, *unit2, *unit3;
{
    if (unit == NULL || unit->act == NULL || unit2 == NULL || unit3 == NULL)
      return FALSE;
    unit->act->nextaction.type = ACTION_ENTER;
    unit->act->nextaction.args[0] = unit3->id;
    unit->act->nextaction.actee = unit2->id;
    return TRUE;
}

int
net_prep_enter_action(unit, unit2, unit3)
Unit *unit, *unit2, *unit3;
{
    int rslt;

    rslt = prep_enter_action(unit, unit2, unit3);
    broadcast_next_action(unit);
    return rslt;
}

int
do_enter_action(unit, unit2, unit3)
Unit *unit, *unit2, *unit3;
{
    int u2, u3, u4, ox, oy, oz, ot, nx, ny, nz, nu2, speed, acpcost, mpcost, rslt;

    u2 = unit2->type;
    ox = unit2->x;  oy = unit2->y;  oz = unit2->z;
    ot = terrain_at(ox, oy);
    u3 = unit3->type;
    nx = unit3->x;  ny = unit3->y;  nz = unit3->z;
    mpcost = 1;
    if (ut_vanishes_on(u2, ot)
	&& (unit->transport == NULL
	    || uu_ferry_on_leave(unit->transport->type, u2) < over_own)
	&& !can_move_via_conn(unit2, nx, ny)) {
	/* This case is if the unit is already on a connection in hostile terrain
	   and tries to enter without using a bridge, or if it is on a transport
	   in hostile terrain that doesn't ferry. */
	kill_unit(unit2, H_UNIT_VANISHED);
	rslt = A_MOVE_UNIT_GONE;
    } else if (ut_wrecks_on(u2, ot)
	       && (unit->transport == NULL
		   || uu_ferry_on_leave(unit->transport->type, u2) < over_own)
	       && !can_move_via_conn(unit2, nx, ny)) {
	if (u_wrecked_type(u2) == NONUTYPE) {
	    /* Occupants always die if the wrecked unit disappears. */
	    kill_unit(unit, H_UNIT_WRECKED);
	} else {
	    /* Wreck the unit.  Note that we want to do the wrecking even
	       if the unit will vanish, so that occupants can escape if
	       allowed for. */
	    wreck_unit(unit);
	    /* Now make it go away, taking unlucky occupants with. */
	    if (ut_vanishes_on(nu2, ot)) {
		kill_unit(unit2, H_UNIT_VANISHED);
	    }
	}
	rslt = A_MOVE_UNIT_GONE;
    } else {
	/* Change the unit's position. */
	leave_cell(unit2);
	enter_transport(unit2, unit3);
	/* Calculate how much acp has been used up. */
	u4 = (unit2->transport ? unit2->transport->type : NONUTYPE);
	mpcost = total_entry_cost(u2, u4, ox, oy, oz, u3, nx, ny, nz);
	rslt = A_ANY_DONE;
    }
    if (alive(unit)) {
	speed = u_speed(u2);
	if (speed > 0) {
	    acpcost = (mpcost * 100) / speed;
	} else {
	    acpcost = 1;
	}
	use_up_acp(unit, acpcost + uu_acp_to_enter(u2, u3));
    }
    return rslt;
}

int
check_enter_action(unit, unit2, unit3)
Unit *unit, *unit2, *unit3;
{
    int u, u2, u3, u4, u2x, u2y, u3x, u3y, totcost, speed, mpavail, m;
    int ox, oy, oz, nx, ny, nz;

    if (!in_play(unit))
      return A_ANY_ERROR;
    if (!in_play(unit2))
      return A_ANY_ERROR;
    if (!in_play(unit3))
      return A_ANY_ERROR;
    u = unit->type;  u2 = unit2->type;  u3 = unit3->type;
    if (uu_acp_to_enter(u2, u3) < 1)
      return A_ANY_CANNOT_DO;
    if (!can_have_enough_acp(unit, uu_acp_to_enter(u2, u3)))
      return A_ANY_CANNOT_DO;
    /* Can't enter self. */
    if (unit2 == unit3)
      return A_ANY_ERROR;
    u2x = unit2->x;  u2y = unit2->y;
    u3x = unit3->x;  u3y = unit3->y;
    ox = unit2->x;  oy = unit2->y;  oz = unit2->z;
    nx = unit3->x;  ny = unit3->y;  nz = unit3->z;
    if (!between(0, distance(ox, oy, nx, ny), 1))
      return A_ANY_ERROR;
    if (!sides_allow_entry(unit2, unit3))
      return A_ANY_ERROR;
    if (!can_occupy(unit2, unit3))
      return A_ANY_ERROR;
    if (!has_enough_acp(unit, uu_acp_to_enter(u2, u3)))
      return A_ANY_NO_ACP;
    u4 = (unit2->transport ? unit2->transport->type : NONUTYPE);
    totcost = total_entry_cost(u2, u4, ox, oy, oz, u3, nx, ny, nz);
    speed = u_speed(u2);
    /* (should generalize!) */
    if (winds_defined() && u_speed_wind_effect(u2) != lispnil) {
	speed *= wind_force_at(u3x, u3y);
    }
    if (speed > 0 && unit->act) {
	mpavail = (unit->act->acp * speed) / 100;
    } else {
	mpavail = 0;
    }
    /* If transport picks up the unit itself, no need to check mp. */
    if (uu_ferry_on_enter(u3, u2) < over_all) {
	/* Zero mp always disallows movement. */
	if (mpavail <= 0)
	  return A_MOVE_NO_MP;
	/* The free mp might get us enough moves, so add it before comparing. */
	if (mpavail + u_free_mp(u2) < totcost)
	  return A_MOVE_NO_MP;
    }
    /* We have to have a minimum level of supply to be able to move. */
    for_all_material_types(m) {
	if (unit2->supply[m] < um_to_move(u2, m))
	  return A_ANY_NO_MATERIAL;
    }
    return A_ANY_OK;
}

/* This tests whether the relationship between the sides of a unit
   and a prospective transport allows for entry of the unit. */

int
sides_allow_entry(unit, transport)
Unit *unit, *transport;
{
    if (unit->side == NULL) {
    	if (transport->side == NULL) {
    	    return TRUE;
    	} else {
	    /* (should fix this - table does not apply to indeps entering?) */
    	    return uu_can_enter_indep(unit->type, transport->type);
    	}
    } else {
    	if (transport->side == NULL) {
    	    return uu_can_enter_indep(unit->type, transport->type);
    	} else {
	    /* Note that because this is for an explicit action, the unit
	       must trust the transport, so the only test is whether the
	       transports trusts the unit enough to have it as an occupant. */
    	    return unit_trusts_unit(transport, unit);
    	}
    }
}

/* This computes the total mp cost of entering a transport. */

int
total_entry_cost(u1, u3, x1, y1, z1, u2, x2, y2, z2)
int u1, u3, x1, y1, z1, u2, x2, y2, z2;
{
    int cost = 0, ferryout, ferryin, t1, t2, b, dir, conncost, c;

    ferryout = over_nothing;
    ferryin = uu_ferry_on_enter(u2, u1);
    if (u3 != NONUTYPE) {
	/* Charge for leaving the transport. */
    	cost += uu_mp_to_leave(u1, u3);
    	ferryout = uu_ferry_on_leave(u3, u1);
    }
    /* (should include possibility of using conn to cross terrain) */
    /* Maybe add cost to leave terrain of own cell. */
    if (ferryout < over_own && ferryin < over_all) {
	t1 = terrain_at(x1, y1);
    	cost += ut_mp_to_leave(u1, t1);
    }
    /* Maybe add cost to cross one (or more) borders. */
    if (numbordtypes > 0 && ferryout < over_border && ferryin < over_border) {
	dir = closest_dir(x2 - x1, y2 - y1);
	if (dir >= 0) {
	    for_all_terrain_types(b) {
		if (t_is_border(b)
		    && aux_terrain_defined(b)
		    && border_at(x1, y1, dir, b)) {
		    cost += ut_mp_to_enter(u1, b);
		}
	    }
	}
    }
    /* Maybe even have to pay cost of crossing destination's terrain. */
    if (ferryout < over_all && ferryin < over_own) {
	t2 = terrain_at(x2, y2);
    	cost += ut_mp_to_enter(u1, t2);
    }
    /* Use a connection traversal if it would be cheaper.  This is
       only automatic if the connection on/off costs are small enough,
       otherwise the unit has to do explicit actions to get on the
       connection and off again. */
    if (numconntypes > 0) {
	/* Try each connection type to see if it's better. */
	dir = closest_dir(x2 - x1, y2 - y1);
	if (dir >= 0) {
	    for_all_terrain_types(c) {
		if (t_is_connection(c)
		    && aux_terrain_defined(c)
		    && connection_at(x1, y1, dir, c)) {
		    conncost = ut_mp_to_enter(u1, c)
		      + ut_mp_to_traverse(u1, c)
			+ ut_mp_to_leave(u1, c);
		    cost = min(cost, conncost);
		}
	    }
	}
    }
    /* Add the actual cost of entry. */
    cost += uu_mp_to_enter(u1, u2);
    /* Movement must always cost at least 1 mp. */
    if (cost < 1)
      cost = 1;
    return cost;
}

/* Note the recursion - should precalc this property. */

int
carryable(u)
int u;
{
    int u2;
	
    for_all_unit_types(u2) {
	if (could_carry(u2, u)
	    && (mobile(u2) /* || carryable(u2) */ ))
	  return TRUE;
    }
    return FALSE;
}

static short *accelerables = NULL;

int
accelerable(u)
int u;
{
    int u1, u2;

    if (accelerables == NULL) {
	accelerables = (short *) xmalloc(numutypes * sizeof(int));
	for_all_unit_types(u1) {	
	    for_all_unit_types(u2) {
		if (accelerator(u1, u2)) {
		    accelerables[u2] = TRUE;
		    break;
		}
	    }
	}
    }
    return accelerables[u];
}

/* True if u1 is a type that can move u2 faster by transporting it. */

int
accelerator(u1, u2)
int u1, u2;
{
    int t;

    if (could_carry(u1, u2)
	&& mobile(u1)) {
	if (u_acp(u1) * u_speed(u1) > u_acp(u2) * u_speed(u2)) {
	    /* The transport must be able to move on any type of terrain
	       accessible to the transportee. */
	    for_all_terrain_types(t) {
		if (terrain_always_impassable(u1, t)
		    && !terrain_always_impassable(u2, t)) {
		    return FALSE;
		}
	    }
	}
	return TRUE;
    }
    return FALSE;
}

int
terrain_always_impassable(u, t)
int u, t;
{
    if (ut_vanishes_on(u, t))
      return TRUE;
    if (ut_wrecks_on(u, t))
      return TRUE;
    /* (should account for speed effect) */
    if (ut_mp_to_enter(u, t) > u_acp(u))
      return TRUE;
    return FALSE;
}