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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
   *
   *     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.beam.examples.complete.kafkatopubsub.transforms;
  
  import java.nio.charset.StandardCharsets;
  import java.util.List;
  import java.util.Map;
  import org.apache.beam.examples.complete.kafkatopubsub.avro.AvroDataClass;
  import org.apache.beam.examples.complete.kafkatopubsub.avro.AvroDataClassKafkaAvroDeserializer;
  import org.apache.beam.examples.complete.kafkatopubsub.kafka.consumer.SslConsumerFactoryFn;
  import org.apache.beam.examples.complete.kafkatopubsub.options.KafkaToPubsubOptions;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.coders.NullableCoder;
  import org.apache.beam.sdk.coders.StringUtf8Coder;
  import org.apache.beam.sdk.extensions.avro.coders.AvroCoder;
  import org.apache.beam.sdk.io.gcp.pubsub.PubsubIO;
  import org.apache.beam.sdk.io.gcp.pubsub.PubsubMessage;
  import org.apache.beam.sdk.io.kafka.KafkaIO;
  import org.apache.beam.sdk.transforms.MapElements;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.values.KV;
  import org.apache.beam.sdk.values.PBegin;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PDone;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableMap;
  import org.apache.kafka.common.serialization.StringDeserializer;
  
  /** Different transformations over the processed data in the pipeline. */
  public class FormatTransform {
  
    public enum FORMAT {
      PUBSUB,
      AVRO
    }
  
    /**
     * Configures Kafka consumer.
     *
     * @param bootstrapServers Kafka servers to read from
     * @param topicsList Kafka topics to read from
     * @param kafkaConfig configuration for the Kafka consumer
     * @param sslConfig configuration for the SSL connection
     * @return configured reading from Kafka
     */
    public static PTransform<PBegin, PCollection<KV<String, String>>> readFromKafka(
        String bootstrapServers,
        List<String> topicsList,
        Map<String, Object> kafkaConfig,
        Map<String, String> sslConfig) {
      return KafkaIO.<String, String>read()
          .withBootstrapServers(bootstrapServers)
          .withTopics(topicsList)
          .withKeyDeserializerAndCoder(
              StringDeserializer.class, (Coder<String>) NullableCoder.of(StringUtf8Coder.of()))
          .withValueDeserializerAndCoder(
              StringDeserializer.class, (Coder<String>) NullableCoder.of(StringUtf8Coder.of()))
          .withConsumerConfigUpdates(kafkaConfig)
          .withConsumerFactoryFn(new SslConsumerFactoryFn(sslConfig))
          .withoutMetadata();
    }
  
    /**
     * Configures Kafka consumer to read avros to {@link AvroDataClass} format.
     *
     * @param bootstrapServers Kafka servers to read from
     * @param topicsList Kafka topics to read from
     * @param config configuration for the Kafka consumer
     * @return configured reading from Kafka
     */
    public static PTransform<PBegin, PCollection<KV<String, AvroDataClass>>> readAvrosFromKafka(
        String bootstrapServers,
        List<String> topicsList,
        Map<String, Object> config,
        Map<String, String> sslConfig) {
      return KafkaIO.<String, AvroDataClass>read()
          .withBootstrapServers(bootstrapServers)
          .withTopics(topicsList)
          .withKeyDeserializerAndCoder(
              StringDeserializer.class, (Coder<String>) NullableCoder.of(StringUtf8Coder.of()))
          .withValueDeserializerAndCoder(
              AvroDataClassKafkaAvroDeserializer.class, AvroCoder.of(AvroDataClass.class))
          .withConsumerConfigUpdates(config)
          .withConsumerFactoryFn(new SslConsumerFactoryFn(sslConfig))
          .withoutMetadata();
    }
  
    /**
     * The {@link FormatOutput} wraps a String serializable messages with the {@link PubsubMessage}
     * class.
     */
    public static class FormatOutput extends PTransform<PCollection<String>, PDone> {
  
      private final KafkaToPubsubOptions options;
  
      public FormatOutput(KafkaToPubsubOptions options) {
        this.options = options;
      }
  
      @Override
      public PDone expand(PCollection<String> input) {
        return input
            .apply(
                "convertMessagesToPubsubMessages",
                MapElements.into(TypeDescriptor.of(PubsubMessage.class))
                    .via(
                        (String json) ->
                            new PubsubMessage(
                                json.getBytes(StandardCharsets.UTF_8), ImmutableMap.of())))
            .apply(
                "writePubsubMessagesToPubSub", PubsubIO.writeMessages().to(options.getOutputTopic()));
      }
    }
  }
  