/* BSD 3-Clause License
 *
 * Copyright © 2008-2022, Jice and the libtcod contributors.
 * All rights reserved.
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 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
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#ifndef TCOD_PATHFINDER_FRONTIER_H
#define TCOD_PATHFINDER_FRONTIER_H

#include <stdint.h>

#include "config.h"
#include "error.h"
#include "heapq.h"

#define TCOD_PATHFINDER_MAX_DIMENSIONS 4

struct TCOD_Frontier {
  int8_t ndim;
  int active_dist;
  int active_index[TCOD_PATHFINDER_MAX_DIMENSIONS];
  struct TCOD_Heap heap;
};
#ifdef __cplusplus
extern "C" {
#endif  // __cplusplus
/**
    Create a new pathfinder frontier.

    `ndim` is the number of dimensions.  Must be in the range `1 <= n <= 4`.
 */
TCOD_PUBLIC TCOD_NODISCARD struct TCOD_Frontier* TCOD_frontier_new(int ndim);
/**
    Delete a pathfinder frontier.
 */
TCOD_PUBLIC void TCOD_frontier_delete(struct TCOD_Frontier* frontier);
/**
    Pop the next node from this frontier.

    The popped node variables will placed in the `active_dist` and
    `active_index` attributes.
 */
TCOD_PUBLIC TCOD_Error TCOD_frontier_pop(struct TCOD_Frontier* frontier);
/**
    Add a node to this frontier.

    `index[frontier->ndim]` is the position of the node to add to the frontier.

    `dist` is the total distance of the node.  This should be a low number
    like 0, but can also be a negative number such as `INT_MIN`.
    When adding a node as an edge then `dist` is `frontier->active_dist` plus
    the cost of the edge.

    `heuristic` is the true priority of the node, used to affect node order.
    For Dijkstra-like algorithms this should be the same as `dist`.
    For A* this should be `dist` plus the maximum possible distance to the
    goal.
 */
TCOD_PUBLIC TCOD_Error
TCOD_frontier_push(struct TCOD_Frontier* __restrict frontier, const int* __restrict index, int dist, int heuristic);
/**
    Return the current number of nodes in this frontier.
 */
TCOD_PUBLIC TCOD_NODISCARD int TCOD_frontier_size(const struct TCOD_Frontier* frontier);
/**
    Remove all nodes from this frontier.
 */
TCOD_PUBLIC TCOD_Error TCOD_frontier_clear(struct TCOD_Frontier* frontier);
#ifdef __cplusplus
}  // extern "C"
#endif  // __cplusplus
#endif  // TCOD_PATHFINDER_FRONTIER_H
