/*
    * 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 org.apache.giraph.io.VertexValueInputFormat;
  import org.apache.giraph.io.VertexValueReader;
  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;
  
  import java.io.IOException;
  import java.util.List;
  
  /**
   * HCatalog {@link VertexValueInputFormat} for reading vertex values from
   * Hive/Pig.
   *
   * @param <I> Vertex id
   * @param <V> Vertex value
   */
  public abstract class HCatalogVertexValueInputFormat<I extends
      WritableComparable, V extends Writable>
      extends VertexValueInputFormat<I, V> {
    /**
     * HCatalog input format.
     */
    private GiraphHCatInputFormat hCatInputFormat = new GiraphHCatInputFormat();
  
    @Override
    public List<InputSplit> getSplits(JobContext context, int minSplitCountHint)
      throws IOException, InterruptedException {
      return hCatInputFormat.getVertexSplits(context);
    }
  
    /**
     * {@link VertexValueReader} for {@link HCatalogVertexValueInputFormat}.
     */
    protected abstract class HCatalogVertexValueReader
        extends VertexValueReader<I, V> {
      /** Internal {@link RecordReader}. */
      private RecordReader<WritableComparable, HCatRecord> hCatRecordReader;
      /** Context passed to initialize. */
      private TaskAttemptContext context;
  
      @Override
      public final void initialize(InputSplit inputSplit,
                                   TaskAttemptContext context)
        throws IOException, InterruptedException {
        super.initialize(inputSplit, context);
        hCatRecordReader =
            hCatInputFormat.createVertexRecordReader(inputSplit, context);
        hCatRecordReader.initialize(inputSplit, context);
        this.context = context;
      }
  
      @Override
      public boolean nextVertex() 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 VertexValueReader}.
 
    * @return {@link HCatalogVertexValueReader} instance.
    */
   protected abstract HCatalogVertexValueReader createVertexValueReader();
 
   @Override
   public final VertexValueReader<I, V>
   createVertexValueReader(InputSplit split, TaskAttemptContext context)
     throws IOException {
     try {
       HCatalogVertexValueReader reader = createVertexValueReader();
       reader.initialize(split, context);
       return reader;
     } catch (InterruptedException e) {
       throw new IllegalStateException(
           "createVertexValueReader: Interrupted creating reader.", e);
     }
   }
 
   /**
    * {@link HCatalogVertexValueReader} for tables holding a complete vertex
    * value in each row.
    */
   protected abstract class SingleRowHCatalogVertexValueReader
       extends HCatalogVertexValueReader {
     /**
      * Get vertex id from a record.
      *
      * @param record Input record
      * @return I Vertex id
      */
     protected abstract I getVertexId(HCatRecord record);
 
     /**
      * Get vertex value from a record.
      *
      * @param record Input record
      * @return V Vertex value
      */
     protected abstract V getVertexValue(HCatRecord record);
 
     @Override
     public final I getCurrentVertexId() throws IOException,
         InterruptedException {
       return getVertexId(getRecordReader().getCurrentValue());
     }
 
     @Override
     public final V getCurrentVertexValue() throws IOException,
         InterruptedException {
       return getVertexValue(getRecordReader().getCurrentValue());
     }
   }
 }