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Algorithms for the JUNG project
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/*
 * Copyright (c) 2005, the JUNG Project and the Regents of the University of
 * California All rights reserved.
 *
 * This software is open-source under the BSD license; see either "license.txt"
 * or http://jung.sourceforge.net/license.txt for a description.
 *
 * Created on Jul 9, 2005
 */

package edu.uci.ics.jung.algorithms.layout;
import java.awt.Dimension;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.collections15.Transformer;
import org.apache.commons.collections15.map.LazyMap;

import edu.uci.ics.jung.graph.Forest;
import edu.uci.ics.jung.graph.util.TreeUtils;

/**
 * A {@code Layout} implementation that assigns positions to {@code Tree} or 
 * {@code Forest} vertices using associations with nested circles ("balloons").  
 * A balloon is nested inside another balloon if the first balloon's subtree
 * is a subtree of the second balloon's subtree.
 * 
 * @author Tom Nelson 
 *  
 */
public class BalloonLayout extends TreeLayout {

    protected Map polarLocations =
    	LazyMap.decorate(new HashMap(),
    			new Transformer() {
					public PolarPoint transform(V arg0) {
						return new PolarPoint();
					}});
    
    protected Map radii = new HashMap();
    
    /**
     * Creates an instance based on the input forest.
     */
    public BalloonLayout(Forest g) 
    {
        super(g);
    }
    
    protected void setRootPolars() 
    {
        List roots = TreeUtils.getRoots(graph);
        if(roots.size() == 1) {
    		// its a Tree
    		V root = roots.get(0);
    		setRootPolar(root);
            setPolars(new ArrayList(graph.getChildren(root)),
                    getCenter(), getSize().width/2);
    	} else if (roots.size() > 1) {
    		// its a Forest
    		setPolars(roots, getCenter(), getSize().width/2);
    	}
    }
    
    protected void setRootPolar(V root) {
    	PolarPoint pp = new PolarPoint(0,0);
    	Point2D p = getCenter();
    	polarLocations.put(root, pp);
    	locations.put(root, p);
    }
    

    protected void setPolars(List kids, Point2D parentLocation, double parentRadius) {

    	int childCount = kids.size();
    	if(childCount == 0) return;
    	// handle the 1-child case with 0 limit on angle.
    	double angle = Math.max(0, Math.PI / 2 * (1 - 2.0/childCount));
    	double childRadius = parentRadius*Math.cos(angle) / (1 + Math.cos(angle));
    	double radius = parentRadius - childRadius;

    	double rand = Math.random();

    	for(int i=0; i< childCount; i++) {
    		V child = kids.get(i);
    		double theta = i* 2*Math.PI/childCount + rand;
    		radii.put(child, childRadius);
    		
    		PolarPoint pp = new PolarPoint(theta, radius);
    		polarLocations.put(child, pp);
    		
    		Point2D p = PolarPoint.polarToCartesian(pp);
    		p.setLocation(p.getX()+parentLocation.getX(), p.getY()+parentLocation.getY());
    		locations.put(child, p);
    		setPolars(new ArrayList(graph.getChildren(child)), p, childRadius);
    	}
    }

    @Override
    public void setSize(Dimension size) {
    	this.size = size;
    	setRootPolars();
    }

	/**
	 * Returns the coordinates of {@code v}'s parent, or the
	 * center of this layout's area if it's a root.
	 */
	public Point2D getCenter(V v) {
		V parent = graph.getParent(v);
		if(parent == null) {
			return getCenter();
		}
		return locations.get(parent);
	}

	@Override
    public void setLocation(V v, Point2D location) {
		Point2D c = getCenter(v);
		Point2D pv = new Point2D.Double(location.getX()-c.getX(),location.getY()-c.getY());
		PolarPoint newLocation = PolarPoint.cartesianToPolar(pv);
		polarLocations.get(v).setLocation(newLocation);
		
		Point2D center = getCenter(v);
		pv.setLocation(pv.getX()+center.getX(), pv.getY()+center.getY());
		locations.put(v, pv);
	}

	@Override
    public Point2D transform(V v) {
		return locations.get(v);
	}

	/**
	 * @return the radii
	 */
	public Map getRadii() {
		return radii;
	}
}