/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.github.dexecutor.core.graph;
  
  import java.io.IOException;
  import java.io.Writer;
  import java.util.ArrayList;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Queue;
  import java.util.Set;
  
  import com.github.dexecutor.core.graph.Node;
  
  /**
   * A Traversar which does level order traversal of the given graph
   * 
   * @author Nadeem Mohammad
   *
   * @param <T> Type of Node/Task ID
   * @param <R> Type of Node/Task result
   */
  public class LevelOrderTraversar<T extends Comparable<T>, R> implements Traversar<T, R> {
  	
  	private List<Node<T, R>> processed = new ArrayList<Node<T, R>>();
  	
  	public void traverse(final Dag<T, R> graph, final Writer writer) {
  		List<List<List<Node<T, R>>>> levelOrderOfGraphs = traverseLevelOrder(graph);
  		int i = 0;
  		for (List<List<Node<T, R>>> levelOrderOfGraph : levelOrderOfGraphs) {
  			try {
  				writer.write("Path #" + (i++) + "\n");
  				printGraph(levelOrderOfGraph, writer);
  				writer.write("\n");
  			} catch (IOException e) {
  				e.printStackTrace();
  			}
  		}
  	}
  
  	private List<List<List<Node<T, R>>>> traverseLevelOrder(final Dag<T, R> graph) {
  		List<List<List<Node<T, R>>>> result = new ArrayList<List<List<Node<T, R>>>>();
  		Set<Node<T, R>> initialNodes = graph.getInitialNodes();
  		for (Node<T, R> iNode : initialNodes) {
  			List<List<Node<T, R>>> iresult = new ArrayList<List<Node<T, R>>>();
  			doTraverse(iresult, iNode);
  			result.add(iresult);
  		}
  		return result;
  	}
  
  	private void doTraverse(final List<List<Node<T, R>>> result, final Node<T, R> iNode) {
  		Queue<Node<T, R>> queue = new LinkedList<Node<T, R>>();
  		queue.offer(iNode);
  		while (!queue.isEmpty()) {
  			List<Node<T, R>> level = new ArrayList<Node<T, R>>();
  			int size = queue.size();
  			for (int i = 0; i < size; i++) {
  				Node<T, R> node = queue.poll();
  				if (!this.processed.contains(node)) {
  					if (!level.contains(node)) {
  						level.add(node);
  					}
  					this.processed.add(node);
  					for (Node<T, R> ogn : node.getOutGoingNodes()) {
  						if (ogn != null && !this.processed.contains(ogn)) {
  							queue.offer(ogn);
  						}
  					}
  				}
  				
  			}
  			result.add(level);
  		}
  	}
  
  	private void printGraph(final List<List<Node<T, R>>> list, final Writer writer) {
  		for (List<Node<T, R>> nodes : list) {
  			try {
  				for (Node<T, R> node : nodes) {
  					writer.write(node + "" + node.getInComingNodes() + " ");
  				}
  				writer.write("\n");
  			} catch (IOException e) {
 				e.printStackTrace();
 			}
 		}
 	}
 }