/*
Copyright (C) 2001, 2006 United States Government
as represented by the Administrator of the
National Aeronautics and Space Administration.
All Rights Reserved.
*/
package gov.nasa.worldwind.layers;

import gov.nasa.worldwind.avlist.AVKey;
import gov.nasa.worldwind.avlist.AVList;
import gov.nasa.worldwind.avlist.AVListImpl;
import gov.nasa.worldwind.awt.WorldWindowGLCanvas;
import gov.nasa.worldwind.geom.Angle;
import gov.nasa.worldwind.geom.LatLon;
import gov.nasa.worldwind.geom.Sector;
import gov.nasa.worldwind.geom.Vec4;
import gov.nasa.worldwind.globes.Globe;
import gov.nasa.worldwind.util.LevelSet;

import java.awt.*;
import java.awt.image.BufferedImage;

/**
 * Procedural layer example
 * @author Patrick Murris
 * @version $Id:$
 */
public class ProceduralShadingLayer extends ProceduralTiledImageLayer
{
    public ProceduralShadingLayer()
    {
        super(makeLevels());
        this.setUseTransparentTextures(true);
    }

    private static LevelSet makeLevels()
    {
        AVList params = new AVListImpl();

        params.setValue(AVKey.TILE_WIDTH, 128);
        params.setValue(AVKey.TILE_HEIGHT, 128);
        params.setValue(AVKey.DATA_CACHE_NAME, "Tests/ProceduralShading");
        params.setValue(AVKey.SERVICE, "*");
        params.setValue(AVKey.DATASET_NAME, "*");
        params.setValue(AVKey.FORMAT_SUFFIX, ".png");
        params.setValue(AVKey.NUM_LEVELS, 10);
        params.setValue(AVKey.NUM_EMPTY_LEVELS, 4);
        params.setValue(AVKey.LEVEL_ZERO_TILE_DELTA, new LatLon(Angle.fromDegrees(36d), Angle.fromDegrees(36d)));
        params.setValue(AVKey.SECTOR, Sector.FULL_SPHERE);

        return new LevelSet(params);
    }

    private WorldWindowGLCanvas wwd;
    private Vec4 light = new Vec4(1, 1, -1).normalize3();  // Light direction (from South-East)
    private double ambiant = .3;              // Minimum lighting (0 - 1)

    public void setWwd(WorldWindowGLCanvas wwd)
    {
        this.wwd = wwd;
    }

    protected BufferedImage createTileImage(TextureTile tile, BufferedImage image)
    {
        int width = tile.getLevel().getTileWidth();
        int height = tile.getLevel().getTileHeight();
        Graphics2D g2 = image.createGraphics();
        if (this.wwd != null)
        {
            Globe globe = this.wwd.getModel().getGlobe();
            double latStep = tile.getSector().getDeltaLatDegrees() / height;
            double lonStep = tile.getSector().getDeltaLonDegrees() / width;

            // Compute shading for each pixel
            for (int x = 0; x < width; x++)
            {
                double lon = tile.getSector().getMinLongitude().degrees + lonStep * x + lonStep / 2;
                for (int y = 0; y < height; y++)
                {
                    double lat = tile.getSector().getMaxLatitude().degrees - latStep * y - latStep / 2;

                    Vec4 p0 = globe.computePointFromPosition(Angle.fromDegrees(lat), Angle.fromDegrees(lon), 0);
                    Vec4 px = globe.computePointFromPosition(Angle.fromDegrees(lat), Angle.fromDegrees(lon - lonStep / 2), 0);
                    Vec4 py = globe.computePointFromPosition(Angle.fromDegrees(lat + latStep / 2), Angle.fromDegrees(lon), 0);

                    double el0 = globe.getElevation(Angle.fromDegrees(lat), Angle.fromDegrees(lon));
                    double elx = globe.getElevation(Angle.fromDegrees(lat), Angle.fromDegrees(lon - lonStep / 2));
                    double ely = globe.getElevation(Angle.fromDegrees(lat + latStep / 2), Angle.fromDegrees(lon));

                    Vec4 vx = new Vec4(p0.distanceTo3(px), 0, elx - el0).normalize3();
                    Vec4 vy = new Vec4(0, p0.distanceTo3(py), ely - el0).normalize3();
                    Vec4 normal = vx.cross3(vy).normalize3();

                    double shade = 1d - Math.max(-light.dot3(normal), ambiant);

                    image.setRGB(x, y, new Color(0f, 0f, 0f, (float)shade).getRGB());
                }
            }
        }
        else
        {
            // Draw a red cross on white background
            g2.setPaint(Color.WHITE);
            g2.fillRect(0, 0, width, height);
            g2.setPaint(Color.RED);
            g2.drawLine(0, 0, width , height);
            g2.drawLine(0, height, width , 0);
        }
        return image;
    }

    @Override
    public String toString()
    {
        return "Procedural Shading";
    }
}