/*
 * 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 samza.examples.avro;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import org.apache.avro.Schema;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.generic.GenericRecord;
import org.apache.avro.generic.IndexedRecord;
import org.apache.avro.io.BinaryDecoder;
import org.apache.avro.io.DatumWriter;
import org.apache.avro.io.DecoderFactory;
import org.apache.avro.io.Encoder;
import org.apache.avro.io.EncoderFactory;
import org.apache.samza.SamzaException;
import org.apache.samza.config.Config;
import org.apache.samza.serializers.Serde;
import org.apache.samza.serializers.SerdeFactory;


public class AvroSerDeFactory implements SerdeFactory {

  public static String CFG_AVRO_SCHEMA = "serializers.avro.schema";

  @Override
  public Serde getSerde(String name, Config config) {
    return new AvroSerDe(config);
  }

  private class AvroSerDe implements Serde {
    private final Schema schema;

    public AvroSerDe(Config config) {
      schema = Schema.parse(config.get(CFG_AVRO_SCHEMA));
    }

    @Override
    public Object fromBytes(byte[] bytes) {
      GenericRecord record;
      try {
        record = genericRecordFromBytes(bytes, schema);
      } catch (IOException e) {
        throw new SamzaException("Unable to deserialize the record", e);
      }
      return record;
    }

    @Override
    public byte[] toBytes(Object o) {
      GenericRecord record = (GenericRecord) o;
      try {
        return encodeAvroGenericRecord(schema, record);
      } catch (IOException e) {
        throw new SamzaException("Unable to serialize the record", e);
      }
    }
  }

  public byte[] encodeAvroGenericRecord(Schema schema, GenericRecord record) throws IOException {
    DatumWriter<IndexedRecord> msgDatumWriter = new GenericDatumWriter<>(schema);
    ByteArrayOutputStream os = new ByteArrayOutputStream();
    Encoder encoder = EncoderFactory.get().binaryEncoder(os, null);
    msgDatumWriter.write(record, encoder);
    encoder.flush();
    return os.toByteArray();
  }

  private static <T> T genericRecordFromBytes(byte[] bytes, Schema schema) throws IOException {
    BinaryDecoder binDecoder = DecoderFactory.defaultFactory().createBinaryDecoder(bytes, null);
    GenericDatumReader<T> reader = new GenericDatumReader<>(schema);
    return reader.read(null, binDecoder);
  }
}