package de.intevation.flys.artifacts.geom;

import java.awt.Shape;
import java.awt.geom.Path2D;
import java.awt.geom.Point2D;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

import de.intevation.flys.artifacts.math.Linear;
import static de.intevation.flys.artifacts.geom.VectorUtils.EPSILON;
import static de.intevation.flys.artifacts.geom.VectorUtils.X;
import static de.intevation.flys.artifacts.geom.VectorUtils.Y;

public class Polygon2D
implements   Serializable
{
    public static final Comparator<Point2D> POINT_X_CMP =
        new Comparator<Point2D>() {
            public int compare(Point2D a, Point2D b) {
                double d = X(a) - X(b);
                if (d < 0d) return -1;
                return d > 0d ? + 1 : 0;
            }
        };

    public static final Comparator<Point2D []> FIRST_POINT_X =
        new Comparator<Point2D []>() {
            public int compare(Point2D [] a, Point2D [] b) {
                if (a.length == 0) return -1; // should not happen.
                if (b.length == 0) return +1; // should not happen.
                double d = X(a[0]) - Y(b[0]);
                if (d < 0d) return -1;
                return d > 0d ? + 1 : 0;
            }
        };

    protected List<Point2D> points;

    public Polygon2D() {
        points = new ArrayList<Point2D>();
    }

    public Polygon2D(List<Point2D> points) {
        this.points = points;
    }

    public void add(double x, double y) {
        points.add(new Point2D.Double(x, y));
    }

    protected static boolean addCheck(Point2D p, List<Point2D> points) {
        switch (points.size()) {
            case 0:
                points.add(p);
                return true;
            case 1:
                if (VectorUtils.epsilonEquals(points.get(0), p)) {
                    return false;
                }
                points.add(p);
                return true;
            default:
                int L = points.size()-1;
                Point2D last = points.get(L);
                if (VectorUtils.epsilonEquals(last, p)) {
                    return false;
                }
                Point2D before = points.get(L-1);
                if (VectorUtils.collinear(before, last, p)) {
                    points.set(L, p);
                }
                else {
                    points.add(p);
                }
                return true;
        }
    }

    public boolean addCheck(Point2D p) {
        return addCheck(p, points);
    }

    public void addReversed(List<Point2D> other) {
        for (int i = other.size()-1; i >= 0; --i) {
            addCheck(other.get(i));
        }
    }

    public double area() {
        double area = 0d;

        for (int i = 0, N = points.size(); i < N; ++i) {
            int j = (i + 1) % N;
            Point2D pi = points.get(i);
            Point2D pj = points.get(j);
            area += X(pi)*Y(pj);
            area -= X(pj)*Y(pi);
        }

        return 0.5d*area;
    }

    public Shape toShape() {
        Path2D.Double path = new Path2D.Double();

        int N = points.size();

        if (N > 0) {
            Point2D p = points.get(0);
            path.moveTo(X(p), Y(p));
            for (int i = 1; i < N; ++i) {
                p = points.get(i);
                path.lineTo(X(p), Y(p));
            }
            path.closePath();
        }

        return path;
    }

    protected static List<Point2D []> splitByNaNs(
        double [] xs,
        double [] ys
    ) {
        List<Point2D []> parts = new ArrayList<Point2D []>();

        List<Point2D> tmp = new ArrayList<Point2D>(xs.length);

        for (int i = 0; i < xs.length; ++i) {
            double x = xs[i];
            double y = ys[i];

            if (Double.isNaN(x) || Double.isNaN(y)) {
                if (!tmp.isEmpty()) {
                    Point2D [] part = new Point2D[tmp.size()];
                    parts.add(tmp.toArray(part));
                    tmp.clear();
                }
            }
            else {
                tmp.add(new Point2D.Double(x, y));
            }
        }

        if (!tmp.isEmpty()) {
            Point2D [] part = new Point2D[tmp.size()];
            parts.add(tmp.toArray(part));
        }

        return parts;
    }

    protected static boolean removeNoneIntersecting(
        List<Point2D []> As,
        List<Point2D []> Bs
    ) {
        int B = Bs.size()-1;
        OUTER: for (int i = 0; i < As.size();) {
            Point2D [] a = As.get(i);
            int lo = 0, hi = B;
            while (lo <= hi) {
                int mid = (lo + hi) >> 1;
                Point2D [] b = Bs.get(mid);
                     if (X(a[0]) > X(b[b.length-1])) lo = mid+1;
                else if (X(a[a.length-1]) < X(b[0])) hi = mid-1;
                else {
                    // found: keep
                    ++i;
                    continue OUTER;
                }
            }
            // not found: remove
            As.remove(i);
        }

        return As.isEmpty();
    }

    protected static void buildPolygons(
        Point2D []      as,
        Point2D []      bs,
        Point2D [][]    rest,
        List<Polygon2D> positives,
        List<Polygon2D> negatives
    ) {
        List<Point2D> apoints = new ArrayList<Point2D>();
        List<Point2D> bpoints = new ArrayList<Point2D>();

        double ax = X(as[0]);
        double bx = X(bs[0]);

        int ai = 1;
        int bi = 1;

        boolean intersect = false;

        if (ax == bx) {
            apoints.add(as[0]);
            bpoints.add(bs[0]);
        }
        else if (ax > bx) {
            apoints.add(as[0]);
            double bx1;
            while ((bx1 = X(bs[bi])) < ax) ++bi;
            if (bx1 == ax) {
                bpoints.add(bs[bi]);
            }
            else { // need to calculate start b point.
                intersect = true;
                double by1 = Linear.linear(
                    ax,
                    X(bs[bi-1]), bx1,
                    Y(bs[bi-1]), Y(bs[bi]));

                bpoints.add(new Point2D.Double(ax, by1));
            }
        }
        else { // bx > ax: Symmetric case
            bpoints.add(bs[0]);
            double ax1;
            while ((ax1 = X(as[ai])) < bx) ++ai;
            if (ax1 == bx) {
                apoints.add(as[ai]);
            }
            else { // need to calculate start b point.
                intersect = true;
                double ay1 = Linear.linear(
                    bx,
                    X(as[ai-1]), ax1,
                    Y(as[ai-1]), Y(as[ai]));

                apoints.add(new Point2D.Double(bx, ay1));
            }
        }

        // now we have a point in each list, decide if neg/pos.
        boolean neg = Y(bpoints.get(0)) > Y(apoints.get(0));

        // Continue with inner points

        Line line = new Line();

        while (ai < as.length && bi < bs.length) {
            double xan = X(as[ai]);
            double xbn = X(bs[bi]);
            if (xan == xbn) {
                double yan = Y(as[ai]);
                double ybn = Y(bs[ai]);

                if (neg) {
                    if (yan > ybn) { // intersection
                        Point2D ip = VectorUtils.intersection(
                            apoints.get(apoints.size()-1), as[ai],
                            bpoints.get(bpoints.size()-1), bs[bi]);
                        addCheck(ip, apoints);
                        addCheck(ip, bpoints);
                        Polygon2D p = new Polygon2D(
                            new ArrayList<Point2D>(apoints));
                        p.addReversed(bpoints);
                        negatives.add(p);
                        apoints.clear();
                        bpoints.clear();
                        apoints.add(ip);
                        bpoints.add(ip);
                        neg = !neg;
                    }
                    else { // no intersection
                        addCheck(as[ai], apoints);
                        addCheck(bs[bi], bpoints);
                    }
                }
                else { // not neg
                    if (ybn > yan) { // intersection
                        Point2D ip = VectorUtils.intersection(
                            apoints.get(apoints.size()-1), as[ai],
                            bpoints.get(bpoints.size()-1), bs[bi]);
                        addCheck(ip, apoints);
                        addCheck(ip, bpoints);
                        Polygon2D p = new Polygon2D(
                            new ArrayList<Point2D>(apoints));
                        p.addReversed(bpoints);
                        positives.add(p);
                        apoints.clear();
                        bpoints.clear();
                        apoints.add(ip);
                        bpoints.add(ip);
                        neg = !neg;
                    }
                    else { // no intersection
                        addCheck(as[ai], apoints);
                        addCheck(bs[bi], bpoints);
                    }
                }
                ++ai;
                ++bi;
            }
            else if (xan > xbn) {
                line.set(apoints.get(apoints.size()-1), as[ai]);
                double dir = neg ? -1d: 1d; // XXX: correct sign?
                while  (bi < bs.length
                    && X(bs[bi]) < xan
                    && line.eval(bs[bi])*dir > EPSILON)
                    ++bi;
                if (bi == bs.length) {
                    // b run out of points
                    // calculate Y(last_a, as[ai]) for X(bs[bi-1])
                    double ay1 = Linear.linear(
                        X(bs[bi-1]),
                        X(apoints.get(apoints.size()-1)), X(as[ai]),
                        Y(apoints.get(apoints.size()-1)), Y(as[ai]));
                    addCheck(new Point2D.Double(X(bs[bi-1]), ay1), apoints);
                    addCheck(bs[bi-1], bpoints);
                    Polygon2D p = new Polygon2D(
                        new ArrayList<Point2D>(apoints));
                    p.addReversed(bpoints);
                    apoints.clear();
                    bpoints.clear();
                    (neg ? negatives : positives).add(p);
                    break;
                }
                else {
                    // TODO: intersect line and/or X(bs[bi]) >= xan?
                }
            }
            else { // xbn > xan
                line.set(bpoints.get(bpoints.size()-1), bs[bi]);
                // TODO: continue symmetric
            }
        }

        // TODO: Continue with closing segment
    }

    public static final class Line {

        private double a;
        private double b;
        private double c;

        public Line() {
        }

        public Line(Point2D p1, Point2D p2) {
            set(p1, p2);
        }

        public void set(Point2D p1, Point2D p2) {
            Point2D p3 =
                VectorUtils.normalize(
                VectorUtils.sub(p1, p2));

            Point2D n = VectorUtils.ortho(p3);

            a = X(n);
            b = Y(n);

            // a*x + b*y + c = 0
            // c = -a*x -b*y

            c = -a*X(p1) - b*Y(p1);
        }

        public double eval(Point2D p) {
            return a*X(p) + b*Y(p) + c;
        }
    }

    public static void createPolygons(
        double [] xAs, double [] yAs,
        double [] xBs, double [] yBs,
        List<Polygon2D> positives,
        List<Polygon2D> negatives
    ) {
        if (xAs.length == 0 || xBs.length == 0) {
            return;
        }

        List<Point2D []> splAs = splitByNaNs(xAs, yAs);
        List<Point2D []> splBs = splitByNaNs(xBs, yBs);

        // They feeded us with NaNs only.
        if (splAs.isEmpty() || splBs.isEmpty()) {
            return;
        }

        // Sort each part by x to ensure that the first
        // is the smallest.
        for (Point2D [] splA: splAs) {
            Arrays.sort(splA, POINT_X_CMP);
        }

        for (Point2D [] splB: splBs) {
            Arrays.sort(splB, POINT_X_CMP);
        }

        // Now sort all parts by there first elements.
        // Should be good enough to find overlapping regions.
        Collections.sort(splAs, FIRST_POINT_X);
        Collections.sort(splBs, FIRST_POINT_X);

        // Check if the two series intersect at all.
        // If no then there will be no area between them.

        Point2D [] p1 = splAs.get(0);
        Point2D [] p2 = splBs.get(splBs.size()-1);

        // Sort out the ranges that are not intersecting
        // the ranges in the other series.
        // We are going to merge them anyway
        // so this is not strictly required.
        // Keep it to recude cases.
        if (removeNoneIntersecting(splAs, splBs)
        ||  removeNoneIntersecting(splBs, splAs)
        ) {
            // They do not intersect at all.
            return;
        }

        // TODO: Intersect/split the two series parts.
    }
}
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