/*******************************************************************************
 * Copyright (c) 2011 Ziver Koc
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 ******************************************************************************/
package zutil.algo.path;

import java.util.HashSet;
import java.util.LinkedList;
import java.util.Queue;

/**
 * A class that uses BFS to find a path
 * 
 * @author Ziver
 */
public class BreadthFirstSearch implements PathFinder{

	/**
	 * Returns the first path to the destination
	 * 
	 * @param start is the start Node
	 * @param stop is the goal Node
	 * @return A list with the path
	 */
	public LinkedList<PathNode> find(PathNode start, PathNode stop){
		Queue<PathNode> queue = new LinkedList<PathNode>();
		HashSet<PathNode> visited = new HashSet<PathNode>();
		
		queue.add(start);
		visited.add( start );
		
		PathNode tmp;
		while(!queue.isEmpty()){
			tmp = queue.poll();	
			
			for(PathNode next : tmp.getNeighbors()){				
				if(!visited.contains( next ) && tmp.getNeighborCost(next) > 0){
					queue.add(next);
					visited.add( next );
					next.setParentNeighbor(tmp);
					
					if(next.equals(stop)){
						return stop.traversTo(start);
					}
				}
			}
		}
		
		return new LinkedList<PathNode>();
	}
}