/*

  * 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.io.hcatalog;

 import java.io.IOException;

 import java.util.List;

 import org.apache.giraph.edge.Edge;

 import org.apache.giraph.edge.EdgeFactory;

 import org.apache.giraph.io.EdgeInputFormat;

 import org.apache.giraph.io.EdgeReader;

 import org.apache.hadoop.io.NullWritable;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import org.apache.hadoop.mapreduce.InputSplit;

 import org.apache.hadoop.mapreduce.JobContext;

 import org.apache.hadoop.mapreduce.RecordReader;

 import org.apache.hadoop.mapreduce.TaskAttemptContext;

 import org.apache.hcatalog.data.HCatRecord;

 /**

  * HCatalog {@link EdgeInputFormat} for reading edges from Hive/Pig.

  *

  * @param <I> Vertex id

  * @param <E> Edge value

  */

 public abstract class HCatalogEdgeInputFormat<

     I extends WritableComparable,

     E extends Writable>

     extends EdgeInputFormat<I, E> {

   /**

    * HCatalog input format.

    */

   private GiraphHCatInputFormat hCatInputFormat = new GiraphHCatInputFormat();

   @Override

   public final List<InputSplit> getSplits(JobContext context,

                                           int minSplitCountHint)

     throws IOException, InterruptedException {

     return hCatInputFormat.getEdgeSplits(context);

   }

   /**

    * Get underlying HCatalog input format. Used for creating readers.

    *

    * @return GiraphHCatInputFormat stored.

    */

   protected GiraphHCatInputFormat getHCatInputFormat() {

     return hCatInputFormat;

   }

   /**

    * {@link EdgeReader} for {@link HCatalogEdgeInputFormat}.

    */

   protected abstract static class HCatalogEdgeReader<

       I extends WritableComparable, E extends Writable>

       extends EdgeReader<I, E> {

     /** HCatalog input format to use */

     private final GiraphHCatInputFormat hCatInputFormat;

     /** Internal {@link RecordReader}. */

     private RecordReader<WritableComparable, HCatRecord> hCatRecordReader;

     /** Context passed to initialize. */

     private TaskAttemptContext context;

     /**

      * Constructor taking hcat input format to use.

      *

      * @param hCatInputFormat HCatalog input format

      */

     public HCatalogEdgeReader(GiraphHCatInputFormat hCatInputFormat) {

       this.hCatInputFormat = hCatInputFormat;

     }

     @Override

     public final void initialize(InputSplit inputSplit,

                                  TaskAttemptContext context)

       throws IOException, InterruptedException {

       hCatRecordReader =

           hCatInputFormat.createEdgeRecordReader(inputSplit, context);

       hCatRecordReader.initialize(inputSplit, context);

       this.context = context;

     }

     @Override

     public boolean nextEdge() throws IOException, InterruptedException {

       return hCatRecordReader.nextKeyValue();

     }

     @Override

     public final void close() throws IOException {

       hCatRecordReader.close();

     }

     @Override

     public final float getProgress() throws IOException, InterruptedException {

       return hCatRecordReader.getProgress();

     }

     /**

      * Get the record reader.

      *

      * @return Record reader to be used for reading.

      */

     protected final RecordReader<WritableComparable, HCatRecord>

     getRecordReader() {

       return hCatRecordReader;

     }

     /**

      * Get the context.

      *

      * @return Context passed to initialize.

      */

     protected final TaskAttemptContext getContext() {

       return context;

     }

   }

   /**

    * Create {@link EdgeReader}.

    *

    * @return {@link HCatalogEdgeReader} instance.

    */

   protected abstract HCatalogEdgeReader<I, E> createEdgeReader();

   @Override

   public EdgeReader<I, E>

   createEdgeReader(InputSplit split, TaskAttemptContext context)

     throws IOException {

     try {

       HCatalogEdgeReader reader = createEdgeReader();

       reader.initialize(split, context);

       return reader;

     } catch (InterruptedException e) {

       throw new IllegalStateException(

           "createEdgeReader: Interrupted creating reader.", e);

     }

   }

   /**

    * {@link HCatalogEdgeReader} for tables holding a complete edge

    * in each row.

    */

   protected abstract static class SingleRowHCatalogEdgeReader<

       I extends WritableComparable, E extends Writable>

       extends HCatalogEdgeReader<I, E> {

     /**

      * Constructor

      * @param hCatInputFormat giraph input format to use

      */

     public SingleRowHCatalogEdgeReader(GiraphHCatInputFormat hCatInputFormat) {

       super(hCatInputFormat);

     }

     /**

      * Get source vertex id from a record.

      *

      * @param record Input record

      * @return I Source vertex id

      */

     protected abstract I getSourceVertexId(HCatRecord record);

     /**

      * Get target vertex id from a record.

      *

      * @param record Input record

      * @return I Target vertex id

      */

     protected abstract I getTargetVertexId(HCatRecord record);

     /**

      * Get edge value from a record.

      *

      * @param record Input record

      * @return E Edge value

      */

     protected abstract E getEdgeValue(HCatRecord record);

     @Override

     public I getCurrentSourceId() throws IOException, InterruptedException {

       HCatRecord record = getRecordReader().getCurrentValue();

       return getSourceVertexId(record);

     }

     @Override

     public Edge<I, E> getCurrentEdge() throws IOException,

         InterruptedException {

       HCatRecord record = getRecordReader().getCurrentValue();

       return EdgeFactory.create(getTargetVertexId(record),

           getEdgeValue(record));

     }

   }

   /**

    * {@link HCatalogEdgeReader} for tables holding a complete edge

    * in each row where the edges contain no data other than IDs they point to.

    */

   protected abstract static class SingleRowHCatalogEdgeNoValueReader<

       I extends WritableComparable>

       extends HCatalogEdgeReader<I, NullWritable> {

     /**

      * Constructor

      * @param hCatInputFormat giraph input format to use

      */

     public SingleRowHCatalogEdgeNoValueReader(

         GiraphHCatInputFormat hCatInputFormat) {

       super(hCatInputFormat);

     }

     /**

      * Get source vertex id from a record.

      *

      * @param record Input record

      * @return I Source vertex id

      */

     protected abstract I getSourceVertexId(HCatRecord record);

     /**

      * Get target vertex id from a record.

      *

      * @param record Input record

      * @return I Target vertex id

      */

     protected abstract I getTargetVertexId(HCatRecord record);

     @Override

     public I getCurrentSourceId() throws IOException, InterruptedException {

       HCatRecord record = getRecordReader().getCurrentValue();

       return getSourceVertexId(record);

     }

     @Override

     public Edge<I, NullWritable> getCurrentEdge() throws IOException,

         InterruptedException {

       HCatRecord record = getRecordReader().getCurrentValue();

       return EdgeFactory.create(getTargetVertexId(record));

     }

   }

 }