/*
    * Copyright (c) 2005, The JUNG Authors
    * All rights reserved.
    *
    * This software is open-source under the BSD license; see either "license.txt"
    * or https://github.com/jrtom/jung/blob/master/LICENSE for a description.
    *
    * Created on Aug 23, 2005
    */
  
  package edu.uci.ics.jung.visualization.layout;
  
  import java.awt.geom.Point2D;
  
  import com.google.common.base.Function;
  import com.google.common.base.Functions;
  import com.google.common.cache.CacheBuilder;
  import com.google.common.cache.CacheLoader;
  import com.google.common.cache.LoadingCache;
  
  import edu.uci.ics.jung.algorithms.layout.Layout;
  import edu.uci.ics.jung.algorithms.layout.LayoutDecorator;
  import edu.uci.ics.jung.graph.Graph;
  import edu.uci.ics.jung.visualization.util.Caching;
  
  /**
   * A LayoutDecorator that caches locations in a clearable Map. This can be used to ensure that
   * edge endpoints are always the same as vertex locations when they are drawn in the render loop 
   * during the time that the layout's relaxer thread is changing the locations.
   * 
   * @see LayoutDecorator
   * @author Tom Nelson 
   *
   */
  public class CachingLayout<V, E> extends LayoutDecorator<V,E> implements Caching {
      
      protected LoadingCache<V, Point2D> locations;
  
      public CachingLayout(Layout<V, E> delegate) {
      	super(delegate);
      	Function<V, Point2D> chain = Functions.<V,Point2D,Point2D>compose(
      		new Function<Point2D,Point2D>() {
      			public Point2D apply(Point2D p) {
      				return (Point2D)p.clone();
      		}}, 
      		delegate);
      	this.locations = CacheBuilder.newBuilder().build(CacheLoader.from(chain));
      }
      
      @Override
      public void setGraph(Graph<V, E> graph) {
          delegate.setGraph(graph);
      }
  
  	public void clear() {
  	    this.locations = CacheBuilder.newBuilder().build(new CacheLoader<V, Point2D>() {
  	    	public Point2D load(V vertex) {
  	    		return new Point2D.Double();
  	    	}
  	    });
  	}
  
  	public void init() {
  	}
  
  	public Point2D apply(V v) {
  		return locations.getUnchecked(v);
  	}
  }