/*

  * 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.utils.VertexIdEdges;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import java.io.DataInput;

 import java.io.DataOutput;

 import java.io.IOException;

 /**

  * Collects incoming edges for vertices owned by this worker.

  *

  * @param <I> Vertex id

  * @param <V> Vertex value

  * @param <E> Edge value

  */

 public interface EdgeStore<I extends WritableComparable,

    V extends Writable, E extends Writable> {

   /**

    * Add edges belonging to a given partition on this worker.

    * Note: This method is thread-safe.

    *

    * @param partitionId Partition id for the incoming edges.

    * @param edges Incoming edges

    */

   void addPartitionEdges(int partitionId, VertexIdEdges<I, E> edges);

   /**

    * Move all edges from temporary storage to their source vertices.

    * Note: this method is not thread-safe and is called once all vertices and

    * edges are read in INPUT_SUPERSTEP.

    */

   void moveEdgesToVertices();

   /**

    * Deserialize the edges of a given partition, and removes the associated data

    * from the store.

    * Note: This method is not thread-safe (i.e. should not be called for the

    * same partition at the same time).

    *

    * @param partitionId Id of partition to deserialize

    * @param output Output to write the edge store to

    */

   void writePartitionEdgeStore(int partitionId, DataOutput output)

       throws IOException;

   /**

    * Serialize the edges of a given partition, and adds it to the partition

    * store (assumes that the edge store does not have any edge from the

    * partition already).

    * Note: This method is not thread-safe (i.e. should not be called for the

    * same partition at the same time).

    *

    * @param partitionId Id of partition to serialize

    * @param input Input to read the partition from

    */

   void readPartitionEdgeStore(int partitionId, DataInput input)

       throws IOException;

   /**

    * Check if edge store has edge for a given partition

    *

    * @param partitionId Id of partition

    * @return True iff edge store have messages for the given partition

    */

   boolean hasEdgesForPartition(int partitionId);

 }