/*

  * 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 org.apache.giraph.edge;

 import org.apache.giraph.graph.Vertex;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import java.util.Iterator;

 /**

  * Helper class to provide a mutable iterable over the edges when the chosen

  * {@link OutEdges} doesn't offer a specialized one.

  *

  * @param <I> Vertex id

  * @param <E> Edge value

  */

 public class MutableEdgesIterable<I extends WritableComparable,

     E extends Writable> implements Iterable<MutableEdge<I, E>> {

   /** Vertex that owns the out-edges. */

   private Vertex<I, ?, E> vertex;

   /**

    * Constructor.

    *

    * @param vertex Owning vertex

    */

   public MutableEdgesIterable(Vertex<I, ?, E> vertex) {

     this.vertex = vertex;

   }

   @Override

   public Iterator<MutableEdge<I, E>> iterator() {

     final MutableEdgesWrapper<I, E> mutableEdgesWrapper =

         MutableEdgesWrapper.wrap((OutEdges<I, E>) vertex.getEdges(),

             vertex.getConf());

     vertex.setEdges(mutableEdgesWrapper);

     return new Iterator<MutableEdge<I, E>>() {

       /** Iterator over the old edges. */

       private Iterator<Edge<I, E>> oldEdgesIterator =

           mutableEdgesWrapper.getOldEdgesIterator();

       /** New edges data structure. */

       private OutEdges<I, E> newEdges = mutableEdgesWrapper.getNewEdges();

       @Override

       public boolean hasNext() {

         // If the current edge is not null,

         // we need to add it to the new edges.

         Edge<I, E> currentEdge = mutableEdgesWrapper.getCurrentEdge();

         if (currentEdge != null) {

           newEdges.add(currentEdge);

           mutableEdgesWrapper.setCurrentEdge(null);

         }

         if (!oldEdgesIterator.hasNext()) {

           vertex.setEdges(newEdges);

           return false;

         } else {

           return true;

         }

       }

       @Override

       public MutableEdge<I, E> next() {

         // If the current edge is not null,

         // we need to add it to the new edges.

         MutableEdge<I, E> currentEdge =

             mutableEdgesWrapper.getCurrentEdge();

         if (currentEdge != null) {

           newEdges.add(currentEdge);

         }

         // Read the next edge and return it.

         currentEdge = (MutableEdge<I, E>) oldEdgesIterator.next();

         mutableEdgesWrapper.setCurrentEdge(currentEdge);

         return currentEdge;

       }

       @Override

       public void remove() {

         // Set the current edge to null, so that it's not added to the

         // new edges.

         mutableEdgesWrapper.setCurrentEdge(null);

         mutableEdgesWrapper.decrementEdges();

       }

     };

   }

 }