Spatial_Quadtree.h

/*
 * Gamedev Framework (gf)
 * Copyright (C) 2016-2021 Julien Bernard
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */
#ifndef GF_SPATIAL_QUAD_TREE_H
#define GF_SPATIAL_QUAD_TREE_H

#include <cassert>
#include <vector>

#include "BlockAllocator.h"
#include "CoreApi.h"
#include "Handle.h"
#include "Rect.h"
#include "SpatialTypes.h"

namespace gf {
#ifndef DOXYGEN_SHOULD_SKIP_THIS
inline namespace v1 {
#endif

  class GF_CORE_API Quadtree {
  public:
    Quadtree(const RectF& bounds);

    SpatialId insert(Handle handle, const RectF& bounds);

    void modify(SpatialId id, RectF bounds);

    std::size_t query(const RectF& bounds, SpatialQueryCallback callback, SpatialQuery kind = SpatialQuery::Intersect);

    void remove(SpatialId id);

    void clear();

    Handle operator[](SpatialId id);

  private:
    std::size_t allocateEntry();
    void disposeEntry(std::size_t index);

    std::size_t allocateNode();
    void disposeNode(std::size_t index);

    bool doInsert(std::size_t entryIndex, std::size_t nodeIndex);
    std::size_t doQuery(std::size_t nodeIndex, const RectF& bounds, SpatialQueryCallback callback, SpatialQuery kind);
    void doRemove(std::size_t entryIndex);

    void subdivide(std::size_t nodeIndex);
    void sanitize(std::size_t nodeIndex);

  private:
    static constexpr std::size_t Size = 16;
    static constexpr std::size_t Null = static_cast<std::size_t>(-1);

    struct Entry {
      Handle handle;
      RectF bounds;
      std::size_t node;
    };

    BlockAllocator<Entry> m_entries;

    struct Node {
      RectF bounds;
      std::vector<std::size_t> entries;
      std::size_t parent;
      std::size_t children[4];

      bool isLeaf() {
        return children[0] == Null;
      }
    };

    BlockAllocator<Node> m_nodes;

    std::size_t m_root;
  };

#ifndef DOXYGEN_SHOULD_SKIP_THIS
}
#endif
}

#endif // GF_SPATIAL_QUAD_TREE_H