package de.intevation.gnv.math;

import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.Envelope;
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.geom.GeometryFactory;
import com.vividsolutions.jts.geom.LinearRing;
import com.vividsolutions.jts.geom.Point;
import com.vividsolutions.jts.geom.Polygon;

import com.vividsolutions.jts.index.ItemVisitor;

import java.io.Serializable;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.apache.log4j.Logger;

/**
 *  @author Sascha L. Teichmann (sascha.teichmann@intevation.de)
 */
public class GridCell
implements   Serializable
{
    private static Logger log = Logger.getLogger(GridCell.class);

    public static final class CellFinder
    implements                ItemVisitor
    {
        public    GridCell found;

        protected Point    point;

        public CellFinder() {
        }

        public void prepare(Coordinate center) {
            found = null;
            point = GEOMETRY_FACTORY.createPoint(center);
        }

        public void visitItem(Object item) {
            if (found == null) {
                GridCell cell = (GridCell)item;
                if (cell.contains(point)) {
                    found = cell;
                }
            }
        }
    } // class CellFinder

    public Point2d p1;
    public Point2d p2;
    public Point2d p3;
    public Point2d p4;

    protected Polygon polygon;

    public static final GeometryFactory GEOMETRY_FACTORY
        = new GeometryFactory();

    public GridCell() {
    }

    public GridCell(Point2d p1, Point2d p2, Point2d p3, Point2d p4) {
        this.p1 = p1;
        this.p2 = p2;
        this.p3 = p3;
        this.p4 = p4;
        createPolygon();
    }

    protected void createPolygon() {
        LinearRing shell = GEOMETRY_FACTORY
            .createLinearRing(new Coordinate [] { p1, p2, p3, p4, p1 });
        polygon = GEOMETRY_FACTORY.createPolygon(shell, null);
    }

    public Envelope getEnvelope() {
        return polygon.getEnvelopeInternal();
    }

    public boolean contains(Geometry coord) {
        return polygon.contains(coord);
    }

    public static List<GridCell> pointsToGridCells(
        List<? extends Point2d> points
    ) {
        return pointsToGridCells(points, null);
    }

    public static List<GridCell> pointsToGridCells(
        List<? extends Point2d> points,
        Envelope                relevantArea
    ) {
        int minI = Integer.MAX_VALUE;
        int maxI = Integer.MIN_VALUE;
        int minJ = Integer.MAX_VALUE;
        int maxJ = Integer.MIN_VALUE;

        HashMap<Integer, HashMap<Integer, Point2d>> rows =
            new HashMap<Integer, HashMap<Integer, Point2d>>();

        int culled = 0;

        for (Point2d p: points) {

            if (relevantArea != null && !relevantArea.contains(p.x, p.y)) {
                ++culled;
                continue;
            }

            if (p.i < minI) minI = p.i;
            if (p.i > maxI) maxI = p.i;
            if (p.j < minJ) minJ = p.j;
            if (p.j > maxJ) maxJ = p.j;

            HashMap<Integer, Point2d> row = rows.get(p.i);

            if (row == null) {
                rows.put(p.i, row = new HashMap<Integer, Point2d>());
            }

            row.put(p.j, p);
        }

        ArrayList<GridCell> cells = new ArrayList<GridCell>(points.size());

        for (int i = minI + 1; i <= maxI; ++i) {
            HashMap<Integer, Point2d> row1 = rows.get(i-1);
            HashMap<Integer, Point2d> row2 = rows.get(i);
            if (row1 != null && row2 != null) {
                for (int j = minJ + 1; j < maxJ; ++j) {
                    Point2d p1 = row1.get(j-1);
                    Point2d p2 = row1.get(j);
                    Point2d p3 = row2.get(j);
                    Point2d p4 = row2.get(j-1);

                    if (p1 != null && p2 != null &&  p3 != null && p4 != null) {
                        cells.add(new GridCell(p1, p2, p3, p4));
                    }
                } // for all columns in row
            }
        } // for all rows

        if (log.isDebugEnabled()) {
            log.debug("culled points: " + culled);
            log.debug("min/max i: " + minI + " / " + maxI);
            log.debug("min/max j: " + minJ + " / " + maxJ);
            log.debug("cells found: " + cells.size());
        }

        return cells;
    }
}
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