AlignWaysGeomPoint.java

package com.tilusnet.josm.plugins.alignways.geometry;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;

import org.openstreetmap.josm.data.coor.EastNorth;

public class AlignWaysGeomPoint {
    double x;
    double y;

    public AlignWaysGeomPoint(double x, double y) {
        setX(x);
        setY(y);
    }

    public AlignWaysGeomPoint(EastNorth eastNorth) {
        this.x = eastNorth.getX();
        this.y = eastNorth.getY();
    }

    public double getX() {
        return x;
    }

    public double getY() {
        return y;
    }

    public void setX(double x) {
        this.x = x;
    }

    public void setY(double y) {
        this.y = y;
    }

    public static boolean isSetCollinear(ArrayList<AlignWaysGeomPoint> awPts) {
        if (awPts.size() <= 1)
            return false;
        
        if (awPts.size() == 2)
            return true;
        else {
            // at least 3 points
            // First create a line of the first two points in the set
            AlignWaysGeomLine line = new AlignWaysGeomLine(awPts.get(0), awPts.get(1));
            // ...then check the subsequent points whether they are on the line
            for (int i = 2; i < awPts.size(); i++) {
                if (!line.isPointOnLine(awPts.get(i))) {
                    return false;
                }
            }
            return true;
        }
    }

    /**
     * Determines which (EastNorth) point falls between the other two.
     * Ideally to be used with collinear points.
     * 
     * @return 1, 2 or 3 for pt1, pt2 and pt3, respectively. 
     * 0 if middle value cannot be determined (i.e. some values are equal). 
     */
    public static int getMiddleOf3(
            AlignWaysGeomPoint pt1, 
            AlignWaysGeomPoint pt2, 
            AlignWaysGeomPoint pt3) {
        
        int midPtXIdx = getMiddleOf3(pt1.x, pt2.x, pt3.x);
        int midPtYIdx = getMiddleOf3(pt1.y, pt2.y, pt3.y);
        
        if ((midPtXIdx == 0) && (midPtYIdx == 0))
            // All 3 points overlap: 
            // Design decision: return the middle point (could be any other or none)
            return 2;
        
        if (midPtXIdx == 0) return midPtYIdx; 
        if (midPtYIdx == 0) return midPtXIdx;
        
        // Both x and y middle points could be determined;
        // their indexes must coincide
        if (midPtXIdx == midPtYIdx)
            // Success
            return midPtXIdx; // (or midPtYIdx)
        else
            // Fail
            return 0;
        
    }

    /**
     * Determine which value, d1, d2 or d3 falls in the middle of the other two.
     * @return 1, 2 or 3 for d1, d2 and d3, respectively. 
     * 0 if middle value cannot be determined (i.e. some values are equal). 
     */
    private static int getMiddleOf3(double d1, double d2, double d3) {
        
        Double[] dValues = {d1, d2, d3};
        ArrayList<Double> alValues = new ArrayList<>(Arrays.asList(dValues));
        Collections.sort(alValues);
        
        if ((Math.abs(alValues.get(1) - alValues.get(0)) < 0.01) ||
            (Math.abs(alValues.get(1) - alValues.get(2)) < 0.01))
            // Cannot determine absolute middle value
            return 0;
        else {
            if (Math.abs(alValues.get(1) - d1) < 0.01) return 1;
            if (Math.abs(alValues.get(1) - d2) < 0.01) return 2;
            if (Math.abs(alValues.get(1) - d3) < 0.01) return 3;
        }
        
        // Should never happen
        return 0;
    }
}