/*

  * 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.jython;

 import org.apache.giraph.conf.DefaultImmutableClassesGiraphConfigurable;

 import org.apache.giraph.edge.Edge;

 import org.apache.giraph.edge.OutEdges;

 import org.apache.giraph.graph.GraphType;

 import org.apache.giraph.graph.Vertex;

 import org.apache.giraph.worker.WorkerContext;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import org.apache.hadoop.mapreduce.Mapper;

 import java.io.IOException;

 import java.util.Iterator;

 /**

  * Base class for writing computations in Jython.

  *

  * Note that this class DOES NOT implement

  * {@link org.apache.giraph.graph.Computation}.

  * This is because we want to support passing in pure Jython types,

  * and implementing the {@link org.apache.giraph.graph.Computation}

  * requires passing in {@link Writable}s.

  * Calling such methods from Jython would throw errors. So, instead,

  * we have recreated the methods with the same name here. In each method

  * we check if the type is a pure Jython value, and if so wrap it in

  * the necessary

  * {@link org.apache.giraph.jython.wrappers.JythonWritableWrapper}.

  *

  * This class works together with {@link JythonGiraphComputation} which takes

  * care of the {@link org.apache.giraph.graph.Computation}

  * Giraph infrastructure side of things.

  */

 public abstract class JythonComputation extends

     DefaultImmutableClassesGiraphConfigurable {

   /** The computation to callback to */

   private JythonGiraphComputation giraphCompute;

   public void setGiraphCompute(JythonGiraphComputation giraphCompute) {

     this.giraphCompute = giraphCompute;

   }

   /**

    * User's computation function

    *

    * @param vertex the Vertex to compute on

    * @param messages iterable of messages

    */

   public abstract void compute(Object vertex, Iterable messages);

   /**

    * Prepare for computation. This method is executed exactly once prior to

    * {@link #compute(Object, Iterable)} being called for any of the vertices

    * in the partition.

    */

   public void preSuperstep() { }

   /**

    * Finish computation. This method is executed exactly once after computation

    * for all vertices in the partition is complete.

    */

   public void postSuperstep() { }

   /**

    * Retrieves the current superstep.

    *

    * @return Current superstep

    */

   public long getSuperstep() {

     return giraphCompute.getSuperstep();

   }

   /**

    * Get the total (all workers) number of vertices that

    * existed in the previous superstep.

    *

    * @return Total number of vertices (-1 if first superstep)

    */

   public long getTotalNumVertices() {

     return giraphCompute.getTotalNumVertices();

   }

   /**

    * Get the total (all workers) number of edges that

    * existed in the previous superstep.

    *

    * @return Total number of edges (-1 if first superstep)

    */

   public long getTotalNumEdges() {

     return giraphCompute.getTotalNumEdges();

   }

   /**

    * Send a message to a vertex id.

    *

    * @param id Vertex id to send the message to

    * @param message Message data to send

    */

   public void sendMessage(Object id, Object message) {

     WritableComparable wrappedId = giraphCompute.wrapIdIfNecessary(id);

     Writable wrappedMessage = giraphCompute.wrapIfNecessary(message,

         GraphType.OUTGOING_MESSAGE_VALUE);

     giraphCompute.sendMessage(wrappedId, wrappedMessage);

   }

   /**

    * Send a message to all edges.

    *

    * @param vertex Vertex whose edges to send the message to.

    * @param message Message sent to all edges.

    */

   public void sendMessageToAllEdges(Vertex vertex, Object message) {

     Writable wrappedMessage = giraphCompute.wrapIfNecessary(message,

         GraphType.OUTGOING_MESSAGE_VALUE);

     giraphCompute.sendMessageToAllEdges(vertex, wrappedMessage);

   }

   /**

    * Send a message to multiple target vertex ids in the iterator.

    *

    * @param vertexIdIterator An iterator to multiple target vertex ids.

    * @param message Message sent to all targets in the iterator.

    */

   public void sendMessageToMultipleEdges(Iterator vertexIdIterator,

       Object message) {

     Writable wrappedMessage = giraphCompute.wrapIfNecessary(message,

         GraphType.OUTGOING_MESSAGE_VALUE);

     giraphCompute.sendMessageToMultipleEdges(vertexIdIterator, wrappedMessage);

   }

   /**

    * Sends a request to create a vertex that will be available during the

    * next superstep.

    *

    * @param id Vertex id

    * @param vertexValue Vertex value

    * @param edges Initial edges

    */

   public void addVertexRequest(Object id, Object vertexValue,

       OutEdges edges) throws IOException {

     WritableComparable wrappedId = giraphCompute.wrapIdIfNecessary(id);

     Writable wrappedValue = giraphCompute.wrapIfNecessary(vertexValue,

         GraphType.VERTEX_VALUE);

     giraphCompute.addVertexRequest(wrappedId, wrappedValue, edges);

   }

   /**

    * Sends a request to create a vertex that will be available during the

    * next superstep.

    *

    * @param id Vertex id

    * @param vertexValue Vertex value

    */

   public void addVertexRequest(Object id, Object vertexValue)

     throws IOException {

     WritableComparable wrappedId = giraphCompute.wrapIdIfNecessary(id);

     Writable wrappedVertexValue = giraphCompute.wrapIfNecessary(vertexValue,

         GraphType.VERTEX_VALUE);

     giraphCompute.addVertexRequest(wrappedId, wrappedVertexValue);

   }

   /**

    * Request to remove a vertex from the graph

    * (applied just prior to the next superstep).

    *

    * @param id Id of the vertex to be removed.

    */

   public void removeVertexRequest(Object id) throws IOException {

     WritableComparable wrappedId = giraphCompute.wrapIdIfNecessary(id);

     giraphCompute.removeVertexRequest(wrappedId);

   }

   /**

    * Request to add an edge of a vertex in the graph

    * (processed just prior to the next superstep)

    *

    * @param sourceVertexId Source vertex id of edge

    * @param edge Edge to add

    */

   public void addEdgeRequest(Object sourceVertexId, Edge edge)

     throws IOException {

     WritableComparable wrappedSourceId =

         giraphCompute.wrapIdIfNecessary(sourceVertexId);

     giraphCompute.addEdgeRequest(wrappedSourceId, edge);

   }

   /**

    * Request to remove all edges from a given source vertex to a given target

    * vertex (processed just prior to the next superstep).

    *

    * @param sourceVertexId Source vertex id

    * @param targetVertexId Target vertex id

    */

   public void removeEdgesRequest(Object sourceVertexId, Object targetVertexId)

     throws IOException {

     WritableComparable wrappedSourceVertexId =

         giraphCompute.wrapIdIfNecessary(sourceVertexId);

     WritableComparable wrappedTargetVertexId =

         giraphCompute.wrapIdIfNecessary(targetVertexId);

     giraphCompute.removeEdgesRequest(wrappedSourceVertexId,

         wrappedTargetVertexId);

   }

   /**

    * Get the mapper context

    *

    * @return Mapper context

    */

   public Mapper.Context getContext() {

     return giraphCompute.getContext();

   }

   /**

    * Get the worker context

    *

    * @param <W> WorkerContext class

    * @return WorkerContext context

    */

   @SuppressWarnings("unchecked")

   public <W extends WorkerContext> W getWorkerContext() {

     return (W) giraphCompute.getWorkerContext();

   }

 }