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package pl.allegro.tech.hermes.common.message.converter;

import java.io.ByteArrayInputStream;
import java.io.Closeable;
import java.io.InputStream;
import org.apache.avro.Schema;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.generic.GenericRecord;
import org.apache.avro.io.BinaryDecoder;
import org.apache.avro.io.DecoderFactory;
import org.apache.commons.lang3.exception.ExceptionUtils;
import tech.allegro.schema.json2avro.converter.AvroConversionException;

public class AvroBinaryDecoders {

  private static ThreadLocal threadLocalEmptyInputStream =
      ThreadLocal.withInitial(() -> new ByteArrayInputStream(new byte[0]));

  private static ThreadLocal threadLocalBinaryDecoder =
      ThreadLocal.withInitial(
          () -> DecoderFactory.get().binaryDecoder(threadLocalEmptyInputStream.get(), null));

  static GenericRecord decodeReusingThreadLocalBinaryDecoder(byte[] message, Schema schema) {
    try (FlushableBinaryDecoderHolder holder = new FlushableBinaryDecoderHolder()) {
      BinaryDecoder binaryDecoder =
          DecoderFactory.get().binaryDecoder(message, holder.getBinaryDecoder());
      return new GenericDatumReader(schema).read(null, binaryDecoder);
    } catch (Exception e) {
      String reason =
          e.getMessage() == null ? ExceptionUtils.getRootCauseMessage(e) : e.getMessage();
      throw new AvroConversionException(
          String.format(
              "Could not deserialize Avro message with provided schema, reason: %s", reason));
    }
  }

  static class FlushableBinaryDecoderHolder implements Closeable {

    final BinaryDecoder binaryDecoder = threadLocalBinaryDecoder.get();

    BinaryDecoder getBinaryDecoder() {
      return binaryDecoder;
    }

    @Override
    public void close() {
      DecoderFactory.get()
          .binaryDecoder(threadLocalEmptyInputStream.get(), threadLocalBinaryDecoder.get());
    }
  }
}