/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2014 Blender Foundation.
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): Bastien Montagne.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#ifndef __BLI_ASTAR_H__
#define __BLI_ASTAR_H__

/** \file BLI_astar.h
 *  \ingroup bli
 *  \brief An implementation of the A* (AStar) algorithm to solve shortest path problem.
 */

#include "BLI_utildefines.h"

#include "BLI_bitmap.h"

/* -------------------------------------------------------------------- */

typedef struct BLI_AStarGNLink {
	int nodes[2];
	float cost;

	void *custom_data;
} BLI_AStarGNLink;

typedef struct BLI_AStarGNode {
	struct ListBase neighbor_links;

	void *custom_data;
} BLI_AStarGNode;

typedef struct BLI_AStarSolution {
	/* Final 'most useful' data. */
	int steps;  /* Number of steps (i.e. walked links) in path (nodes num, including start and end, is steps + 1). */
	int *prev_nodes;  /* Store the path, in reversed order (from destination to source node), as indices. */
	BLI_AStarGNLink **prev_links;  /* Indices are nodes' ones, as prev_nodes, but they map to relevant link. */

	void *custom_data;

	/* Mostly runtime data. */
	BLI_bitmap *done_nodes;
	float *g_costs;
	int *g_steps;

	struct MemArena *mem;  /* Memory arena. */
} BLI_AStarSolution;

typedef struct BLI_AStarGraph {
	int node_num;
	BLI_AStarGNode *nodes;

	void *custom_data;

	struct MemArena *mem;  /* Memory arena. */
} BLI_AStarGraph;

void BLI_astar_node_init(BLI_AStarGraph *as_graph, const int node_index, void *custom_data);
void BLI_astar_node_link_add(
        BLI_AStarGraph *as_graph, const int node1_index, const int node2_index, const float cost, void *custom_data);
int BLI_astar_node_link_other_node(BLI_AStarGNLink *lnk, const int idx);

void BLI_astar_solution_init(BLI_AStarGraph *as_graph, BLI_AStarSolution *as_solution, void *custom_data);
void BLI_astar_solution_clear(BLI_AStarSolution *as_solution);
void BLI_astar_solution_free(BLI_AStarSolution *as_solution);

/**
 * Callback computing the current cost (distance) to next node, and the estimated overall cost to destination node
 * (A* expects this estimation to always be less or equal than actual shortest path from next node to destination one).
 *
 * \param link the graph link between current node and next one.
 * \param node_idx_curr current node index.
 * \param node_idx_next next node index.
 * \param node_idx_dst destination node index.
 */
typedef float (*astar_f_cost)(BLI_AStarGraph *as_graph, BLI_AStarSolution *as_solution, BLI_AStarGNLink *link,
                              const int node_idx_curr, const int node_idx_next, const int node_idx_dst);

void BLI_astar_graph_init(BLI_AStarGraph *as_graph, const int node_num, void *custom_data);
void BLI_astar_graph_free(BLI_AStarGraph *as_graph);
bool BLI_astar_graph_solve(
        BLI_AStarGraph *as_graph, const int node_index_src, const int node_index_dst, astar_f_cost f_cost_cb,
        BLI_AStarSolution *r_solution, const int max_steps);

#endif  /* __BLI_ASTAR_H__ */