/*
 * chase.c  -  Code for one object to chase another
 *
 * Advanced Rogue
 * Copyright (C) 1984, 1985, 1986 Michael Morgan, Ken Dalka and AT&T
 * All rights reserved.
 *
 * Based on "Rogue: Exploring the Dungeons of Doom"
 * Copyright (C) 1980, 1981 Michael Toy, Ken Arnold and Glenn Wichman
 * All rights reserved.
 *
 * See the file LICENSE.TXT for full copyright and licensing information.
 */

/*
 * Code for one object to chase another
 *
 */

#include <ctype.h>
#include <limits.h>
#include "curses.h"
#include "rogue.h"
#define	MAXINT	INT_MAX
#define	MININT	INT_MIN


/*
 * Canblink checks if the monster can teleport (blink).  If so, it will
 * try to blink the monster next to the player.
 */

bool
can_blink(tp)
register struct thing *tp;
{
    register int y, x, index=9;
    coord tryp;	/* To hold the coordinates for use in diag_ok */
    bool spots[9], found_one=FALSE;

    /*
     * First, can the monster even blink?  And if so, there is only a 50%
     * chance that it will do so.  And it won't blink if it is running or
     * held.
     */
    if (off(*tp, CANBLINK) || (on(*tp, ISHELD)) ||
	on(*tp, ISFLEE) ||
	tp->t_action == A_FREEZE ||
	(rnd(12) < 6)) return(FALSE);


    /* Initialize the spots as illegal */
    do {
	spots[--index] = FALSE;
    } while (index > 0);

    /* Find a suitable spot next to the player */
    for (y=hero.y-1; y<hero.y+2; y++)
	for (x=hero.x-1; x<hero.x+2; x++, index++) {
	    /* Make sure x coordinate is in range and that we are
	     * not at the player's position
	     */
	    if (x<0 || x >= cols || index == 4) continue;

	    /* Is it OK to move there? */
	    if (step_ok(y, x, NOMONST, tp) &&
		(!isatrap(mvwinch(cw, y, x)) ||
		  rnd(10) >= tp->t_stats.s_intel ||
		  on(*tp, ISFLY))) {
		/* OK, we can go here.  But don't go there if
		 * monster can't get at player from there
		 */
		tryp.y = y;
		tryp.x = x;
		if (diag_ok(&tryp, &hero, tp)) {
		    spots[index] = TRUE;
		    found_one = TRUE;
		}
	    }
	}

    /* If we found one, go to it */
    if (found_one) {
	char rch;	/* What's really where the creatures moves to */

	/* Find a legal spot */
	while (spots[index=rnd(9)] == FALSE) continue;

	/* Get the coordinates */
	y = hero.y + (index/3) - 1;
	x = hero.x + (index % 3) - 1;

	/* Move the monster from the old space */
	mvwaddch(cw, tp->t_pos.y, tp->t_pos.x, tp->t_oldch);

	/* Move it to the new space */
	tp->t_oldch = CCHAR( mvwinch(cw, y, x) );

	/* Display the creature if our hero can see it */
	if (cansee(y, x) &&
	    off(*tp, ISINWALL) &&
	    !invisible(tp))
	    mvwaddch(cw, y, x, tp->t_type);

	/* Fix the monster window */
	mvwaddch(mw, tp->t_pos.y, tp->t_pos.x, ' '); /* Clear old position */
	mvwaddch(mw, y, x, tp->t_type);

	/* Record the new position */
	tp->t_pos.y = y;
	tp->t_pos.x = x;

	/* If the monster is on a trap, trap it */
	rch = CCHAR( mvinch(y, x) );
	if (isatrap(rch)) {
	    if (cansee(y, x)) tp->t_oldch = rch;
	    be_trapped(tp, &(tp->t_pos));
	}
    }

    return(found_one);
}

/* 
 * Can_shoot determines if the monster (er) has a direct line of shot 
 * at the prey (ee).  If so, it returns the direction in which to shoot.
 */

coord *
can_shoot(er, ee)
register coord *er, *ee;
{
    static coord shoot_dir;

    /* 
     * They must be in the same room or very close (at door)
     */
    if (roomin(er) != roomin(ee) && DISTANCE(er->y,er->x,ee->y,ee->x) > 1)
	return(NULL);

    /* Do we have a straight shot? */
    if (!straight_shot(er->y, er->x, ee->y, ee->x, &shoot_dir)) return(NULL);
    else return(&shoot_dir);
}

/*
 * chase:
 *	Find the spot for the chaser(er) to move closer to the
 *	chasee(ee).  Rer is the room of the chaser, and ree is the
 *	room of the creature being chased (chasee).
 */

chase(tp, ee, rer, ree, flee)
register struct thing *tp;
register coord *ee;
register struct room *rer, *ree;
bool flee; /* True if destination (ee) is player and monster is running away
	    * or the player is in a wall and the monster can't get to it
	    */
{
    int dist, thisdist, monst_dist = MAXINT; 
    register coord *er = &tp->t_pos; 
    struct thing *prey;			/* What we are chasing */
    coord ch_ret;			/* Where chasing takes you */
    char ch, mch;
    bool next_player = FALSE;

    /* 
     * set the distance from the chas(er) to the chas(ee) here and then
     * we won't have to reset it unless the chas(er) moves (instead of shoots)
     */
    dist = DISTANCE(er->y, er->x, ee->y, ee->x);

    /*
     * See if our destination is a monster or player.  If so, make "prey" point
     * to it.
     */
    if (ce(hero, *ee)) prey = &player;	/* Is it the player? */
    else if (tp->t_dest && ce(*(tp->t_dest), *ee)) {	/* Is it a monster? */
	struct linked_list *item;

	/* What is the monster we're chasing? */
	item = find_mons(ee->y, ee->x);
	if (item != NULL) prey = THINGPTR(item);
	else prey = NULL;
    }
    else prey = NULL;

    /* We will use at least one movement period */
    tp->t_no_move = movement(tp);
    if (on(*tp, ISFLY)) /* If the creature is flying, speed it up */
	tp->t_no_move /= 2;

    /*
     * If the thing is confused or it can't see the player,
     * let it move randomly. 
     */
    if ((on(*tp, ISHUH) && rnd(10) < 8) ||
	(prey && on(*prey, ISINVIS) && off(*tp, CANSEE))) { /* invisible prey */
	/*
	 * get a valid random move
	 */
	tp->t_newpos = *rndmove(tp);
	dist = DISTANCE(tp->t_newpos.y, tp->t_newpos.x, ee->y, ee->x);
    }

    /*
     * Otherwise, find the empty spot next to the chaser that is
     * closest to the chasee.
     */
    else {
	register int ey, ex, x, y;
	int dist_to_old = MININT; /* Dist from goal to old position */

	/*
	 * This will eventually hold where we move to get closer
	 * If we can't find an empty spot, we stay where we are.
	 */
	dist = flee ? 0 : MAXINT;
	ch_ret = *er;

	/* Are we at our goal already? */
	if (!flee && ce(ch_ret, *ee)) {
	    turn_off(*tp, ISRUN);	/* So stop running! */
	    return;
	}

	ey = er->y + 1;
	ex = er->x + 1;

	/* Check all possible moves */
	for (x = er->x - 1; x <= ex; x++) {
	    if (x < 0 || x >= cols) /* Don't try off the board */
		continue;
	    for (y = er->y - 1; y <= ey; y++) {
		coord tryp;

		if ((y < 1) || (y >= lines - 2)) /* Don't try off the board */
		    continue;

		/* Don't try the player if not going after the player */
		if ((flee || !ce(hero, *ee) || on(*tp, ISFRIENDLY)) &&
		    x == hero.x && y == hero.y) {
		    next_player = TRUE;
		    continue;
		}

		tryp.x = x;
		tryp.y = y;

		/* Is there a monster on this spot closer to our goal?
		 * Don't look in our spot or where we were.
		 */
		if (!ce(tryp, *er) && !ce(tryp, tp->t_oldpos) &&
		    isalpha(mch = CCHAR( mvwinch(mw, y, x) ) )) {
		    int test_dist;

		    test_dist = DISTANCE(y, x, ee->y, ee->x);
		    if (test_dist <= 25 &&   /* Let's be fairly close */
			test_dist < monst_dist) {
			/* Could we really move there? */
			mvwaddch(mw, y, x, ' '); /* Temporarily blank monst */
			if (diag_ok(er, &tryp, tp)) monst_dist = test_dist;
			mvwaddch(mw, y, x, mch); /* Restore monster */
		    }
		}

		/* Can we move onto the spot? */	
		if (!diag_ok(er, &tryp, tp)) continue;

		ch = CCHAR( mvwinch(cw, y, x) );	/* Screen character */

		/*
		 * Stepping on player is NOT okay if we are fleeing.
		 * If we are friendly to the player and there is a monster
		 * in the way that is not of our race, it is okay to move
		 * there.
		 */
		if (step_ok(y, x, FIGHTOK, tp) &&
		    (off(*tp, ISFLEE) || ch != PLAYER))
		{
		    /*
		     * If it is a trap, an intelligent monster may not
		     * step on it (unless our hero is on top!)
		     */
		    if ((isatrap(ch))			&& 
			(rnd(10) < tp->t_stats.s_intel) &&
			(!on(*tp, ISFLY))		&&
			(y != hero.y || x != hero.x)) 
			    continue;

		    /*
		     * OK -- this place counts
		     */
		    thisdist = DISTANCE(y, x, ee->y, ee->x);

		    /* Adjust distance if we are being shot at */
		    if (tp->t_wasshot && tp->t_stats.s_intel > 5 &&
			prey != NULL) {
			/* Move out of line of sight */
			if (straight_shot(tryp.y, tryp.x, ee->y, ee->x, NULL)) {
			    if (flee) thisdist -= SHOTPENALTY;
			    else thisdist += SHOTPENALTY;
			}

			/* But do we want to leave the room? */
			else if (rer && rer == ree && ch == DOOR)
			    thisdist += DOORPENALTY;
		    }

		    /* Don't move to the last position if we can help it
		     * (unless out prey just moved there)
		     */
		    if (ce(tryp, tp->t_oldpos) && (flee || !ce(tryp, hero)))
			dist_to_old = thisdist;

		    else if ((flee && (thisdist > dist)) ||
			(!flee && (thisdist < dist)))
		    {
			ch_ret = tryp;
			dist = thisdist;
		    }
		}
	    }
	}

	/* If we aren't trying to get the player, but he is in our way,
	 * hit him (unless we have been turned or are friendly).  next_player
	 * being TRUE -> we are next to the player but don't want to hit him.
	 *
	 * If we are friendly to the player, following him, and standing next
	 * to him, we will try to help him out in battle.
	 */
	if (next_player && off(*tp, WASTURNED)) {
	    if (off(*tp, ISFRIENDLY) &&
		((flee && ce(ch_ret, *er)) ||
		 (!flee && DISTANCE(er->y, er->x, ee->y, ee->x) < dist)) &&
		step_ok(tp->t_dest->y, tp->t_dest->x, NOMONST, tp)) {
		/* Okay to hit player */
		debug("Switching to hero.");
		tp->t_newpos = hero;
		tp->t_action = A_MOVE;
		return;
	    }
	    else if (on(*tp, ISFRIENDLY) && !flee && ce(*ee, hero)) {
		/*
		 * Look all around the player.  If there is a fightable
		 * creature next to both of us, hit it.  Otherwise, if
		 * there is a fightable creature next to the player, try
		 * to move next to it.
		 */
		dist = MAXINT;
		for (x = hero.x - 1; x <= hero.x + 1; x++) {
		    if (x < 0 || x >= cols) /* Don't try off the board */
			continue;
		    for (y = hero.y - 1; y <= hero.y + 1; y++) {
			if ((y < 1) || (y >= lines - 2)) /* Stay on the board */
			    continue;

			/* Is there a fightable monster here? */
			if (isalpha(mvwinch(mw, y, x)) &&
			    step_ok(y, x, FIGHTOK, tp) &&
			    off(*tp, ISSTONE)) {
			    thisdist = DISTANCE(er->y, er->x, y, x);
			    if (thisdist < dist) {
				dist = thisdist;
				ch_ret.y = y;
				ch_ret.x = x;
			    }
			}
		    }
		}

		/* Are we next to a bad guy? */
		if (dist <= 2) {	/* Get him! */
		    tp->t_newpos = ch_ret;
		    tp->t_action = A_MOVE;
		}

		/* Try to move to the bad guy */
		else if (dist < MAXINT)
		    chase(tp, &ch_ret,
			  roomin(&tp->t_pos), roomin(&ch_ret), FALSE);

		else tp->t_action = A_NIL;

		return;
	    }
	}