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/*
 * Copyright © 2017 Cask Data, Inc.
 *
 * Licensed 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 co.cask.wrangler.codec;

import co.cask.wrangler.api.DecoderException;
import co.cask.wrangler.api.Record;
import com.google.gson.Gson;
import org.apache.avro.AvroTypeException;
import org.apache.avro.Schema;
import org.apache.avro.generic.GenericRecord;
import org.apache.avro.io.DecoderFactory;
import org.apache.avro.io.JsonDecoder;
import org.apache.avro.util.Utf8;

import java.io.ByteArrayInputStream;
import java.io.EOFException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * This class {@link JsonAvroDecoder} decodes a byte array of AVRO Json Records into the {@link Record} structure.
 */
public class JsonAvroDecoder extends AbstractAvroDecoder {
  private final Gson gson;

  public JsonAvroDecoder(Schema schema) {
    super(schema);
    this.gson = new Gson();
  }

  @Override
  public List decode(byte[] bytes) throws DecoderException {
    List records = new ArrayList<>();
    JsonDecoder decoder = null;
    ByteArrayInputStream in = new ByteArrayInputStream(bytes);
    try {
      decoder = DecoderFactory.get().jsonDecoder(getSchema(), in);
      while (true) {
        try {
          GenericRecord gRecord = getReader().read(null, decoder);
          List fields = getSchema().getFields();
          Record r = new Record();
          for (Schema.Field field : fields) {
            Object object = gRecord.get(field.name());
            if (object instanceof Utf8) {
              Utf8 o = (Utf8) object;
              object = o.toString();
            } else if (object instanceof Map || object instanceof List) {
              object = gson.toJson(object);
            }
            r.add(field.name(), object);
          }
          records.add(r);
        } catch (EOFException e) {
          break; // Reached end of buffer.
        }
      }
    } catch (AvroTypeException e) {
      throw new DecoderException(e.getMessage());
    } catch (IOException e) {
      throw new DecoderException("Issue create json decoder, verify the schema");
    } finally {
      try {
        in.close();
      } catch (IOException e) {
        // Can't do anything.
      }
    }
    return records;
  }
}