/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2016 Daniel Baston
 *
 * This is free software; you can redistribute and/or modify it under
 * the terms of the GNU Lesser General Public Licence as published
 * by the Free Software Foundation.
 * See the COPYING file for more information.
 *
 **********************************************************************
 *
 * Last port: index/strtree/BoundablePair.java (JTS-1.14)
 *
 **********************************************************************/

#ifndef GEOS_INDEX_STRTREE_BOUNDABLEPAIR_H
#define GEOS_INDEX_STRTREE_BOUNDABLEPAIR_H

#include <geos/index/strtree/Boundable.h>
#include <geos/index/strtree/ItemDistance.h>
#include <queue>

/**
 * A pair of {@link Boundable}s, whose leaf items
 * support a distance metric between them.
 * Used to compute the distance between the members,
 * and to expand a member relative to the other
 * in order to produce new branches of the
 * Branch-and-Bound evaluation tree.
 * Provides an ordering based on the distance between the members,
 * which allows building a priority queue by minimum distance.
 *
 * @author Martin Davis
 *
 */
namespace geos {
namespace index {
namespace strtree {

class BoundablePair {
	private:
		const Boundable* boundable1;
		const Boundable* boundable2;
		ItemDistance* itemDistance;
		double mDistance;

	public:
		struct BoundablePairQueueCompare {
			bool operator()(const BoundablePair* a, const BoundablePair* b) {
				return a->getDistance() > b->getDistance();
			}
		};

		typedef std::priority_queue<BoundablePair*, std::vector<BoundablePair*>, BoundablePairQueueCompare> BoundablePairQueue;
		BoundablePair(const Boundable* boundable1, const Boundable* boundable2, ItemDistance* itemDistance);

		/**
		 * Gets one of the member {@link Boundable}s in the pair
		 * (indexed by [0, 1]).
		 *
		 * @param i the index of the member to return (0 or 1)
		 * @return the chosen member
		 */
		const Boundable* getBoundable(int i) const;

		/**
		 * Computes the distance between the {@link Boundable}s in this pair.
		 * The boundables are either composites or leaves.
		 * If either is composite, the distance is computed as the minimum distance
		 * between the bounds.
		 * If both are leaves, the distance is computed by {@link #itemDistance(ItemBoundable, ItemBoundable)}.
		 *
		 * @return
		 */
		double distance() const;

		/**
		 * Gets the minimum possible distance between the Boundables in
		 * this pair.
		 * If the members are both items, this will be the
		 * exact distance between them.
		 * Otherwise, this distance will be a lower bound on
		 * the distances between the items in the members.
		 *
		 * @return the exact or lower bound distance for this pair
		 */
		double getDistance() const;

		/**
		 * Tests if both elements of the pair are leaf nodes
		 *
		 * @return true if both pair elements are leaf nodes
		 */
		bool isLeaves() const;

		static bool isComposite(const Boundable* item);

		static double area(const Boundable* b);

		void expandToQueue(BoundablePairQueue &, double minDistance);
		void expand(const Boundable* bndComposite, const Boundable* bndOther, BoundablePairQueue & priQ, double minDistance);
};
}
}
}

#endif

