/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.refractions.net
 *
 * Copyright (C) 2006      Refractions Research Inc.
 *
 * 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: noding/SegmentPointComparator.java r320 (JTS-1.12)
 *
 **********************************************************************/

#ifndef GEOS_NODING_SEGMENTPOINTCOMPARATOR_H
#define GEOS_NODING_SEGMENTPOINTCOMPARATOR_H

#include <geos/export.h>
#include <geos/geom/Coordinate.h>
#include <cassert>

namespace geos {
namespace noding { // geos.noding

/**
 * Implements a robust method of comparing the relative position of two
 * points along the same segment.
 * The coordinates are assumed to lie "near" the segment.
 * This means that this algorithm will only return correct results
 * if the input coordinates
 * have the same precision and correspond to rounded values
 * of exact coordinates lying on the segment.
 *
 */
class GEOS_DLL SegmentPointComparator {

public:

	/**
	 * Compares two Coordinates for their relative position along a 
	 * segment lying in the specified Octant.
	 *
	 * @return -1 node0 occurs first
	 * @return 0 the two nodes are equal
	 * @return 1 node1 occurs first
	 */
	static int compare(int octant, const geom::Coordinate& p0,
			const geom::Coordinate& p1)
	{
		// nodes can only be equal if their coordinates are equal
		if (p0.equals2D(p1)) return 0;

		int xSign = relativeSign(p0.x, p1.x);
		int ySign = relativeSign(p0.y, p1.y);

		switch (octant) {
			case 0: return compareValue(xSign, ySign);
			case 1: return compareValue(ySign, xSign);
			case 2: return compareValue(ySign, -xSign);
			case 3: return compareValue(-xSign, ySign);
			case 4: return compareValue(-xSign, -ySign);
			case 5: return compareValue(-ySign, -xSign);
			case 6: return compareValue(-ySign, xSign);
			case 7: return compareValue(xSign, -ySign);
		}
		assert(0); // invalid octant value
		return 0;
	 
	}

	static int relativeSign(double x0, double x1)
	{
		if (x0 < x1) return -1;
		if (x0 > x1) return 1;
		return 0;
	}

	static int compareValue(int compareSign0, int compareSign1)
	{
		if (compareSign0 < 0) return -1;
		if (compareSign0 > 0) return 1;
		if (compareSign1 < 0) return -1;
		if (compareSign1 > 0) return 1;
		return 0;
	}
 
};

} // namespace geos.noding
} // namespace geos

#endif // GEOS_NODING_SEGMENTPOINTCOMPARATOR_H
