/*
FLOOD_MAP.C

	Copyright (C) 1991-2001 and beyond by Bungie Studios, Inc.
	and the "Aleph One" developers.
 
	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 3 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.

	This license is contained in the file "COPYING",
	which is included with this source code; it is available online at
	http://www.gnu.org/licenses/gpl.html

Sunday, June 5, 1994 3:25:22 PM

Friday, July 15, 1994 12:54:35 PM
	added visited_polygon array for quickly determining whether we have visited a polygon yet.
Monday, September 5, 1994 2:31:12 PM
	static memory allocated is 512 bytes (visited polygons) and 4k (flood nodes).
Wednesday, October 26, 1994 3:18:59 PM (Jason)
	added _flagged_breadth_first.

Jan 30, 2000 (Loren Petrich):
	Did some typecasts

Feb. 4, 2000 (Loren Petrich):
	Changed halt() to assert(false) for better debugging
*/

/*
on very small maps, choose_random_flood_node() may not terminate
//for performance, maybe we should allow the caller to specify breadth-first instead of best-first.
*/

#include "cseries.h"
#include "map.h"
#include "flood_map.h"

#include <string.h>
#include <stdlib.h>
#include <limits.h>

/* ---------- constants */

#define MAXIMUM_FLOOD_NODES 255
#define UNVISITED NONE

/* ---------- structures */

#define NODE_IS_EXPANDED(n) ((n)->flags&(uint16)0x8000)
#define NODE_IS_UNEXPANDED(n) (!NODE_IS_EXPANDED(n))
#define MARK_NODE_AS_EXPANDED(n) ((n)->flags|=(uint16)0x8000)

struct node_data /* 16 bytes */
{
	uint16 flags;
	
	int16 parent_node_index; /* node index of the node we came from to get here; only used for backtracking */
	int16 polygon_index; /* index of this polygon */
	int32 cost; /* the cost to evaluate this entry */

	int16 depth;

	int32 user_flags;
};

/* ---------- globals */

static short node_count= 0, last_node_index_expanded= NONE;
static struct node_data *nodes = NULL;
static short *visited_polygons = NULL;

/* ---------- private prototypes */

static void add_node(short parent_node_index, short polygon_index, short depth, int32 cost, int32 user_flags);

/* ---------- code */

void allocate_flood_map_memory(
	void)
{
	// Made reentrant because this must be called every time a map is loaded
	if (nodes) delete []nodes;
	nodes= new node_data[MAXIMUM_FLOOD_NODES];
	if (visited_polygons) delete []visited_polygons;
	visited_polygons= new short[MAXIMUM_POLYGONS_PER_MAP];
	assert(nodes&&visited_polygons);
}

/* returns next polygon index or NONE if there are no more polygons left cheaper than maximum_cost */
short flood_map(
	short first_polygon_index,
	int32 maximum_cost,
	cost_proc_ptr cost_proc,
	short flood_mode,
	void *caller_data)
{
	short lowest_cost_node_index, node_index;
	struct node_data *node;
	short polygon_index;
	int32 lowest_cost;

	/* initialize ourselves if first_polygon_index!=NONE */
	if (first_polygon_index!=NONE)
	{
		/* clear the visited polygon array */
		objlist_set(visited_polygons, NONE, MAXIMUM_POLYGONS_PER_MAP);
		
		node_count= 0;
		last_node_index_expanded= NONE;
		add_node(NONE, first_polygon_index, 0, 0, (flood_mode==_flagged_breadth_first) ? *((int32*)caller_data) : 0);
	}
	
	switch (flood_mode)
	{
		case _best_first:
			/* find the unexpanded node with the lowest cost */
			lowest_cost= maximum_cost, lowest_cost_node_index= NONE;
			for (node= nodes, node_index= 0; node_index<node_count; ++node_index, ++node)
			{
				if (NODE_IS_UNEXPANDED(node)&&node->cost<lowest_cost)
				{
					lowest_cost_node_index= node_index;
					lowest_cost= node->cost;
				}
			}
			break;
		
		case _breadth_first:
		case _flagged_breadth_first:
			/* find the next unexpanded node in the list under maximum_cost */
			node_index= (last_node_index_expanded==NONE) ? 0 : (last_node_index_expanded+1);
			for (node= nodes+node_index; node_index<node_count; ++node_index, ++node)
			{
				if (node->cost<maximum_cost) break;
			}
			if (node_index==node_count)
			{
				lowest_cost_node_index= NONE;
				lowest_cost= maximum_cost;
			}
			else
			{
				lowest_cost_node_index= node_index;
				lowest_cost= node->cost;
			}
			break;
		
		case _depth_first:
			/* implementation left to the caller (c.f., zen() in fareast.c) */
			assert(false);
			break;
			
		default:
			assert(false);
			break;
	}

	/* if we found a node, mark it as expanded and add itÕs adjacent non-solid polygons to the search tree */
	if (lowest_cost_node_index!=NONE)
	{
		struct polygon_data *polygon;
		short i;
		
		/* for flood_depth() and reverse_flood_map(), remember which node we successfully expanded last */
		last_node_index_expanded= lowest_cost_node_index;

		/* get pointer to lowest cost node */
		assert(lowest_cost_node_index>=0&&lowest_cost_node_index<node_count);
		node= nodes+lowest_cost_node_index;

		polygon= get_polygon_data(node->polygon_index);
		assert(!POLYGON_IS_DETACHED(polygon));

		/* mark node as expanded */
		MARK_NODE_AS_EXPANDED(node);

		for (i= 0; i<polygon->vertex_count; ++i)		
		{
			short destination_polygon_index= polygon->adjacent_polygon_indexes[i];
			
			if (destination_polygon_index!=NONE &&
				(maximum_cost!=INT32_MAX || visited_polygons[destination_polygon_index]==UNVISITED))
			{
				int32 new_user_flags= node->user_flags;
				int32 cost= cost_proc ? cost_proc(node->polygon_index, polygon->line_indexes[i], destination_polygon_index, (flood_mode==_flagged_breadth_first) ? &new_user_flags : caller_data) : polygon->area;
				
				/* polygons with zero or negative costs are not added to the node list */
				if (cost>0) add_node(lowest_cost_node_index, destination_polygon_index, node->depth+1, lowest_cost+cost, new_user_flags);
			}
		}
		
		polygon_index= node->polygon_index;
		if (flood_mode==_flagged_breadth_first) *((int32*)caller_data)= node->user_flags;
	}
	else
	{
		polygon_index= NONE;
	}
	
	return polygon_index;
}

/* walks backwards from the last node expanded, returning polygons as it goes; returns NONE
	when there are no more polygons to return.  this is useful for pathfinding: when
	flood_map() returns the destination polygon index, calling reverse_flood_map() will return
	the polygons traversed to reach the destination) */
short reverse_flood_map(
	void)
{
	short polygon_index= NONE;
	
	if (last_node_index_expanded!=NONE)
	{
		struct node_data *node;
		
		assert(last_node_index_expanded>=0&&last_node_index_expanded<node_count);
		node= nodes+last_node_index_expanded;

		last_node_index_expanded= node->parent_node_index;
		polygon_index= node->polygon_index;
	}
	
	return polygon_index;
}

/* returns depth (in polygons) at last_node_index_expanded */
short flood_depth(
	void)
{
	assert(last_node_index_expanded>=0&&last_node_index_expanded<node_count);

	return last_node_index_expanded==NONE ? 0 : nodes[last_node_index_expanded].depth;
}

#define MAXIMUM_BIASED_RETRIES 10

/* when looking for a random path, always choose a random node.  if bias is not NULL, then try
	and choose a destination in that direction */
void choose_random_flood_node(
	world_vector2d *bias)
{
	world_point2d origin;
	
	assert(node_count>=1);
	find_center_of_polygon(nodes[0].polygon_index, &origin);
	
	if (node_count>1)
	{
		bool suitable;
		short retries= MAXIMUM_BIASED_RETRIES;
		
		do
		{
			do
			{
				last_node_index_expanded= global_random()%node_count;
			}
			while (NODE_IS_UNEXPANDED(nodes+last_node_index_expanded));

			/* if we have no bias, this node is automatically suitable if it has been expanded;
				if we have a bias, this node is only suitable if it is in the same general
				direction (by sign of dot product) as the bias */
			suitable= true;
			if (bias && (retries-= 1)>=0)
			{
				struct node_data *node= nodes+last_node_index_expanded;
				world_point2d destination;
				
				find_center_of_polygon(node->polygon_index, &destination);
				if (bias->i*(destination.x-origin.x) + bias->j*(destination.y-origin.y)<0) suitable= false;
			}
		}
		while (!suitable);
	}
}

/* ---------- private code */

/* checks to see if the given node is already in the node list */
static void add_node(
	short parent_node_index,
	short polygon_index,
	short depth,
	int32 cost,
	int32 user_flags)
{
	if (node_count<MAXIMUM_FLOOD_NODES)
	{
		struct node_data *node;
		short node_index;
		
		/* see if this polygon already exists in the node list anywhere */
		assert(polygon_index>=0&&polygon_index<dynamic_world->polygon_count);
		if ((node_index= visited_polygons[polygon_index])!=UNVISITED)
		{
			/* there is already a node referencing this polygon; if it has a higher cost
				than the cost we are attempting to add, replace it (because we are doing
				a best-first search, we are guarenteed never to find a better path to an
				expanded node, and in fact if we find a path to a node we have already
				expanded weÕre backtracking and can ignore the node) */
			assert(node_index>=0&&node_index<node_count);
			node= nodes+node_index;
			if (NODE_IS_EXPANDED(node)||node->cost<=cost) node= (struct node_data *) NULL;
		}
		else
		{
			node_index= node_count;
			node= nodes + node_index;
		}
		
		if (node)
		{
			if (node_index==node_count)
			{
				node_count+= 1;
			}
			
			node->flags= 0;
			node->parent_node_index= parent_node_index;
			node->polygon_index= polygon_index;
			node->depth= depth;
			node->cost= cost;
			node->user_flags= user_flags;
			
			assert(polygon_index>=0&&polygon_index<dynamic_world->polygon_count);
			visited_polygons[polygon_index]= node_index;
			
//			dprintf("added polygon #%d to node #%d (nodes=%p,visited=%p)", polygon_index, node_index, nodes, visited_polygons);
		}
	}
}
