package de.intevation.gnv.math;

import com.vividsolutions.jts.geom.Coordinate;

/**
 * Implements {@link de.intevation.gnv.math.Metrics}
 * for linear interpolations and distance measurements.
 * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a>
 */
public final class LinearMetrics
implements         Metrics
{
    /**
     * Instance to prevent needless creations of instances.
     */
    public static final Metrics INSTANCE =
        new LinearMetrics();

    /**
     * Implements the corresponding linear interpolator.
     */
    public static final class LinearInterpolator
    implements                Interpolator
    {
        private double mx;
        private double bx;
        private double my;
        private double by;

        /**
         * Constructor to create a linear interpolator between two
         * given points.
         * @param p1 The first point.
         * @param p2 The second point.
         */
        public LinearInterpolator(Coordinate p1, Coordinate p2) {

            /*
             I) p1.x = 0*m + bx
            II) p2.x = 1*m + bx

            bx = p1.x

            p2.x = m + p1.x

            mx = p2.x - p1.x
            */

            bx = p1.x;
            mx = p2.x - bx;

            by = p1.y;
            my = p2.y - by;
        }

        public void interpolate(double t, Coordinate v) {
            v.x = t*mx + bx;
            v.y = t*my + by;
        }
    } // class LinearInterpolator

    private LinearMetrics() {
    }

    public double distance(Coordinate p1, Coordinate p2) {
        return p1.distance(p2);
    }

    public Interpolator getInterpolator(Coordinate p1, Coordinate p2) {
        return new LinearInterpolator(p1, p2);
    }
}
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