/*
 * Copyright (c) 2010 by Intevation GmbH
 *
 * This program is free software under the LGPL (>=v2.1)
 * Read the file LGPL.txt coming with the software for details
 * or visit http://www.gnu.org/licenses/ if it does not exist.
 */

package de.intevation.gnv.math;

import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.Envelope;

import java.util.Comparator;

import org.apache.log4j.Logger;

/**
 * Point which besides the x, y, z coodinates has an index i, j pair
 * to model neighborhood.
 * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a>
 */
public class Point2d
extends      Coordinate
{
    private static Logger log = Logger.getLogger(Point2d.class);

    /**
     * Numerical tolerance epsilon: {@value}
     */
    public static final double EPSILON = 1e-3d;

    /**
     * Compares two Point2ds by their x coordinates
     */
    public static final Comparator X_COMPARATOR = new Comparator() {
        public int compare(Object a, Object b) {
            double xa = ((Coordinate)a).x;
            double xb = ((Coordinate)b).x;
            if (xa < xb) return -1;
            if (xa > xb) return +1;
            return 0;
        }
    };

    /**
     * Compares two Point2ds by their y coordinates.
     */
    public static final Comparator Y_COMPARATOR = new Comparator() {
        public int compare(Object a, Object b) {
            double ya = ((Coordinate)a).y;
            double yb = ((Coordinate)b).y;
            if (ya < yb) return -1;
            if (ya > yb) return +1;
            return 0;
        }
    };

    /**
     * The i index of this Point2d.
     */
    public int i;
    /**
     * The j index of this Point2d.
     */
    public int j;

    /**
     * Default constructor.
     */
    public Point2d() {
    }

    /**
     * Constructor setting x and y coordinate.
     * @param x The x coordinate.
     * @param y The y coordinate.
     */
    public Point2d(double x, double y) {
        super(x, y);
    }

    /**
     * Constructor setting x, y and i, j.
     * @param x The x coordinate.
     * @param y The y coordinate.
     * @param i The i index.
     * @param j The j index.
     */
    public Point2d(double x, double y, int i, int j) {
        super(x, y);
        this.i = i;
        this.j = j;
    }

    /**
     * Constructor setting x, y, z and i, j.
     * @param x The x coordinate.
     * @param y The y coordinate.
     * @param z The z coordinate.
     * @param i The i index.
     * @param j The j index.
     */
    public Point2d(double x, double y, double z, int i, int j) {
        super(x, y, z);
        this.i = i;
        this.j = j;
    }

    /**
     * Calculates the L1 distance to another Point2d.
     * @param other The other Point2d.
     * @return The L1 distance.
     */
    public double L1(Point2d other) {
        return L1Comparator.L1(this, other);
    }

    /**
     * Creates an envelope around this Point2d with
     * the numerical tolerance of {@link #EPSILON}.
     * @return The envelope.
     */
    public Envelope envelope() {
        return envelope(EPSILON);
    }

    /**
     *Creates an envelope around this Point2d with
     * a given tolerance.
     * @param epsilon The tolerance in all directions.
     * @return The envelope.
     */
    public Envelope envelope(double epsilon) {
        return new Envelope(
            x-epsilon, x+epsilon,
            y-epsilon, y+epsilon);
    }

    /**
     * Given this and another Point2d it looks if there is
     * a gap between the in points in i index direction.
     * @param other The other Point2d.
     * @return true if there is is a gap, else false.
     */
    public boolean hasIGap(Point2d other) {
        return Math.abs(i - other.i) > 1;
    }

    /**
     * Given this and another Point2d it looks if there is
     * a gap between the in points in j index direction.
     * @param other The other Point2d.
     * @return true if there is is a gap, else false.
     */
    public boolean hasJGap(Point2d other) {
        return Math.abs(j - other.j) > 1;
    }

    /**
     * Given this and another Point2d a new Point2d is
     * created via {@link #newPoint() }. The x, y coordinate
     * of the new point is on the line of this and the other
     * given point at a given scaling point.
     * @param t The scaling factor.
     * @param other The other point.
     * @return The new Point2d.
     */
    public Point2d extrapolate(double t, Point2d other) {
        if (other == null) {
            return null;
        }
        Point2d p = newPoint();
        p.x = t*(other.x - x) + x;
        p.y = t*(other.y - y) + y;
        return p;
    }

    /**
     * Creates a new Point2d or an instance of a subclass.
     * Override this in subclasses.
     * @return The new Point2d.
     */
    public Point2d newPoint() {
        return new Point2d(0d, 0d);
    }

    /**
     * Creates a new Point2d or an instance of a subclass
     * at a given coordinate.
     * Override this in subclasses.
     * @param x The x coordinate.
     * @param y The y coordinate.
     * @return The new point.
     */
    public Point2d newPoint(double x, double y) {
        return new Point2d(x, y);
    }

    /**
     * Sets the z value to the inverse distance weighting (IDW) value
     * of the z values of a set of given points.
     * @param ps The points from wich the z values are taken
     * to calculate the IDW.
     */
    public void inverseDistanceWeighting(Point2d [] ps) {

        double sum = 0d;

        double [] d = new double[ps.length];

        for (int i = 0; i < ps.length; ++i) {
            Point2d p = ps[i];
            if (p != null) {
                double di = distance(p);
                if (di < 1e-5d) { z = p.z; return; }
                di = 1d/di;
                d[i] = di;
                sum += di;
            }
        }

        if (sum == 0d) {
            return;
        }

        double v = 0d;

        for (int i = 0; i < ps.length; ++i) {
            Point2d p = ps[i];
            if (p != null) {
                v += p.z*d[i];
            }
        }
        z = v/sum;
    }

    /**
     * Creates a new point via {@link #newPoint() } with the
     * x,y coordinates of the center of a given set of
     * coordinates.
     * @param ps The points from which the x,y coordinates are
     * taken to calculate the center.
     * @return The new center point.
     */
    public static Point2d average(Point2d [] ps) {

        Point2d p = null;
        int count = 0;

        for (int i = 0; i < ps.length; ++i) {
            Point2d t = ps[i];
            if (t != null) {
                ++count;
                if (p == null) {
                    p = t.newPoint(t.x, t.y);
                }
                else {
                    p.x += t.x;
                    p.y += t.y;
                }
            }
        }

        if (p != null) {
            double s = 1d/count;
            p.x *= s;
            p.y *= s;
        }

        return p;
    }

    /**
     * Checks if this Point2d is near to at least one point
     * out of a given set of points. Near is defined by an
     * euclidian distance small than {@link #EPSILON}.
     * @param ps The set of points to be tested.
     * @return true if this Point2d is near to one of the given
     * points, else false.
     */
    public boolean near(Point2d [] ps) {

        for (int i = 0; i < ps.length; ++i) {
            Point2d p = ps[i];
            if (p != null && distance(p) > EPSILON) {
                return false;
            }
        }

        return true;
    }
}
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