/*
 * Copyright (C) 1997-2001 Id Software, Inc.
 *
 * 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.
 *
 * =======================================================================
 *
 * The player trail, used by monsters to locate the player.
 *
 * =======================================================================
 */

#include "../header/local.h"

/*
 * This is a circular list containing the a list of points of where
 * the player has been recently.  It is used by monsters for pursuit.
 *
 * .origin		the spot
 * .owner		forward link
 * .aiment		backward link
 */

#define TRAIL_LENGTH 8

#define NEXT(n) (((n) + 1) & (TRAIL_LENGTH - 1))
#define PREV(n) (((n) - 1) & (TRAIL_LENGTH - 1))

static edict_t *trail[TRAIL_LENGTH];
static int trail_head;
static qboolean trail_active = false;

void
PlayerTrail_Init(void)
{
	int n;

	if (deathmatch->value)
	{
		return;
	}

	for (n = 0; n < TRAIL_LENGTH; n++)
	{
		trail[n] = G_Spawn();
		trail[n]->classname = "player_trail";
	}

	trail_head = 0;
	trail_active = true;
}

void
PlayerTrail_Add(vec3_t spot)
{
	vec3_t temp;

	if (!trail_active)
	{
		return;
	}

	VectorCopy(spot, trail[trail_head]->s.origin);

	trail[trail_head]->timestamp = level.time;

	VectorSubtract(spot, trail[PREV(trail_head)]->s.origin, temp);
	trail[trail_head]->s.angles[1] = vectoyaw(temp);

	trail_head = NEXT(trail_head);
}

void
PlayerTrail_New(vec3_t spot)
{
	if (!trail_active)
	{
		return;
	}

	PlayerTrail_Init();
	PlayerTrail_Add(spot);
}

edict_t *
PlayerTrail_PickFirst(edict_t *self)
{
	int marker;
	int n;

	if (!self)
	{
		return NULL;
	}

	if (!trail_active)
	{
		return NULL;
	}

	for (marker = trail_head, n = TRAIL_LENGTH; n; n--)
	{
		if (trail[marker]->timestamp <= self->monsterinfo.trail_time)
		{
			marker = NEXT(marker);
		}
		else
		{
			break;
		}
	}

	if (visible(self, trail[marker]))
	{
		return trail[marker];
	}

	if (visible(self, trail[PREV(marker)]))
	{
		return trail[PREV(marker)];
	}

	return trail[marker];
}

edict_t *
PlayerTrail_PickNext(edict_t *self)
{
	int marker;
	int n;

	if (!self)
	{
		return NULL;
	}

	if (!trail_active)
	{
		return NULL;
	}

	for (marker = trail_head, n = TRAIL_LENGTH; n; n--)
	{
		if (trail[marker]->timestamp <= self->monsterinfo.trail_time)
		{
			marker = NEXT(marker);
		}
		else
		{
			break;
		}
	}

	return trail[marker];
}

edict_t *
PlayerTrail_LastSpot(void)
{
	return trail[PREV(trail_head)];
}
