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/*
 * 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
 *
 *     https://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.avro.mapred;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import org.apache.hadoop.io.serializer.Serialization;
import org.apache.hadoop.io.serializer.Deserializer;
import org.apache.hadoop.io.serializer.Serializer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;

import org.apache.avro.Schema;
import org.apache.avro.generic.GenericData;
import org.apache.avro.io.BinaryEncoder;
import org.apache.avro.io.BinaryDecoder;
import org.apache.avro.io.DecoderFactory;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.DatumWriter;
import org.apache.avro.io.EncoderFactory;

/** The {@link Serialization} used by jobs configured with {@link AvroJob}. */
public class AvroSerialization extends Configured implements Serialization> {

  @Override
  public boolean accept(Class c) {
    return AvroWrapper.class.isAssignableFrom(c);
  }

  /**
   * Returns the specified map output deserializer. Defaults to the final output
   * deserializer if no map output schema was specified.
   */
  @Override
  public Deserializer> getDeserializer(Class> c) {
    Configuration conf = getConf();
    boolean isKey = AvroKey.class.isAssignableFrom(c);
    Schema schema = isKey ? Pair.getKeySchema(AvroJob.getMapOutputSchema(conf))
        : Pair.getValueSchema(AvroJob.getMapOutputSchema(conf));
    GenericData dataModel = AvroJob.createMapOutputDataModel(conf);
    DatumReader datumReader = dataModel.createDatumReader(schema);
    return new AvroWrapperDeserializer(datumReader, isKey);
  }

  private static final DecoderFactory FACTORY = DecoderFactory.get();

  private class AvroWrapperDeserializer implements Deserializer> {

    private DatumReader reader;
    private BinaryDecoder decoder;
    private boolean isKey;

    public AvroWrapperDeserializer(DatumReader reader, boolean isKey) {
      this.reader = reader;
      this.isKey = isKey;
    }

    @Override
    public void open(InputStream in) {
      this.decoder = FACTORY.directBinaryDecoder(in, decoder);
    }

    @Override
    public AvroWrapper deserialize(AvroWrapper wrapper) throws IOException {
      T datum = reader.read(wrapper == null ? null : wrapper.datum(), decoder);
      if (wrapper == null) {
        wrapper = isKey ? new AvroKey<>(datum) : new AvroValue<>(datum);
      } else {
        wrapper.datum(datum);
      }
      return wrapper;
    }

    @Override
    public void close() throws IOException {
      decoder.inputStream().close();
    }

  }

  /** Returns the specified output serializer. */
  @Override
  public Serializer> getSerializer(Class> c) {
    // AvroWrapper used for final output, AvroKey or AvroValue for map output
    boolean isFinalOutput = c.equals(AvroWrapper.class);
    Configuration conf = getConf();
    Schema schema = isFinalOutput ? AvroJob.getOutputSchema(conf)
        : (AvroKey.class.isAssignableFrom(c) ? Pair.getKeySchema(AvroJob.getMapOutputSchema(conf))
            : Pair.getValueSchema(AvroJob.getMapOutputSchema(conf)));
    GenericData dataModel = AvroJob.createDataModel(conf);
    return new AvroWrapperSerializer(dataModel.createDatumWriter(schema));
  }

  private class AvroWrapperSerializer implements Serializer> {

    private DatumWriter writer;
    private OutputStream out;
    private BinaryEncoder encoder;

    public AvroWrapperSerializer(DatumWriter writer) {
      this.writer = writer;
    }

    @Override
    public void open(OutputStream out) {
      this.out = out;
      this.encoder = new EncoderFactory().binaryEncoder(out, null);
    }

    @Override
    public void serialize(AvroWrapper wrapper) throws IOException {
      writer.write(wrapper.datum(), encoder);
      // would be a lot faster if the Serializer interface had a flush()
      // method and the Hadoop framework called it when needed rather
      // than for every record.
      encoder.flush();
    }

    @Override
    public void close() throws IOException {
      out.close();
    }

  }

}