content: /*
   * 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.kafka.streams.examples.wordcount;
  
  import org.apache.kafka.clients.consumer.ConsumerConfig;
  import org.apache.kafka.common.serialization.Serdes;
  import org.apache.kafka.streams.KafkaStreams;
  import org.apache.kafka.streams.KeyValue;
  import org.apache.kafka.streams.StreamsBuilder;
  import org.apache.kafka.streams.StreamsConfig;
  import org.apache.kafka.streams.processor.PunctuationType;
  import org.apache.kafka.streams.processor.api.Processor;
  import org.apache.kafka.streams.processor.api.ProcessorContext;
  import org.apache.kafka.streams.processor.api.ProcessorSupplier;
  import org.apache.kafka.streams.processor.api.Record;
  import org.apache.kafka.streams.state.KeyValueIterator;
  import org.apache.kafka.streams.state.KeyValueStore;
  import org.apache.kafka.streams.state.StoreBuilder;
  import org.apache.kafka.streams.state.Stores;
  
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.time.Duration;
  import java.util.Collections;
  import java.util.Locale;
  import java.util.Properties;
  import java.util.Set;
  import java.util.concurrent.CountDownLatch;
  
  /**
   * Demonstrates, using a {@link Processor} implementing the low-level Processor APIs (replaces Transformer),
   * how to implement the WordCount program that computes a simple word occurrence histogram from an input text.
   * <p>
   * <strong>Note: This is simplified code that only works correctly for single partition input topics.
   * Check out {@link WordCountDemo} for a generic example.</strong>
   * <p>
   * In this example, the input stream reads from a topic named "streams-plaintext-input", where the values of messages
   * represent lines of text; and the histogram output is written to topic "streams-wordcount-processor-output" where each record
   * is an updated count of a single word.
   * <p>
   * This example differs from {@link WordCountProcessorDemo} in that it uses a {@link ProcessorSupplier} to attach the Processor with the
   * count logic to the Stream, and the topology is wired up through a {@link StreamsBuilder},
   * which more closely resembles the high-level DSL (compared to the Topology builder approach, with Source, Processor, Sink).
   * <p>
   * Before running this example you must create the input topic and the output topic (e.g. via
   * {@code bin/kafka-topics.sh --create ...}), and write some data to the input topic (e.g. via
   * {@code bin/kafka-console-producer.sh}). Otherwise you won't see any data arriving in the output topic.
   */
  public final class WordCountTransformerDemo {
  
      static class MyProcessorSupplier implements ProcessorSupplier<String, String, String, String> {
  
          @Override
          public Processor<String, String, String, String> get() {
              return new Processor<String, String, String, String>() {
                  private KeyValueStore<String, Integer> kvStore;
  
                  @Override
                  public void init(final ProcessorContext<String, String> context) {
                      context.schedule(Duration.ofSeconds(1), PunctuationType.STREAM_TIME, timestamp -> {
                          try (final KeyValueIterator<String, Integer> iter = kvStore.all()) {
                              System.out.println("----------- " + timestamp + " ----------- ");
  
                              while (iter.hasNext()) {
                                  final KeyValue<String, Integer> entry = iter.next();
  
                                  System.out.println("[" + entry.key + ", " + entry.value + "]");
                                  context.forward(new Record<>(entry.key, entry.value.toString(), timestamp));
                              }
                          }
                      });
                      this.kvStore = context.getStateStore("Counts");
                  }
  
                  @Override
                  public void process(final Record<String, String> record) {
                      final String[] words = record.value().toLowerCase(Locale.getDefault()).split("\\W+");
  
                      for (final String word : words) {
                          final Integer oldValue = this.kvStore.get(word);
  
                          if (oldValue == null) {
                              this.kvStore.put(word, 1);
                          } else {
                              this.kvStore.put(word, oldValue + 1);
                          }
                      }
                  }
              };
          }
  
          @Override
          public Set<StoreBuilder<?>> stores() {
              return Collections.singleton(Stores.keyValueStoreBuilder(
                  Stores.inMemoryKeyValueStore("Counts"),
                  Serdes.String(),
                  Serdes.Integer()));
          }
      }
  
      public static void main(final String[] args) throws IOException {
          final Properties props = new Properties();
          if (args != null && args.length > 0) {
              try (final FileInputStream fis = new FileInputStream(args[0])) {
                  props.load(fis);
              }
              if (args.length > 1) {
                  System.out.println("Warning: Some command line arguments were ignored. This demo only accepts an optional configuration file.");
              }
          }
          props.putIfAbsent(StreamsConfig.APPLICATION_ID_CONFIG, "streams-wordcount-transformer");
          props.putIfAbsent(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
          props.putIfAbsent(StreamsConfig.STATESTORE_CACHE_MAX_BYTES_CONFIG, 0);
          props.putIfAbsent(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.StringSerde.class);
          props.putIfAbsent(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.StringSerde.class);
  
          // setting offset reset to earliest so that we can re-run the demo code with the same pre-loaded data
          props.putIfAbsent(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
  
          final StreamsBuilder builder = new StreamsBuilder();
  
          builder.<String, String>stream("streams-plaintext-input")
                  .process(new MyProcessorSupplier())
                  .to("streams-wordcount-processor-output");
  
          final KafkaStreams streams = new KafkaStreams(builder.build(), props);
          final CountDownLatch latch = new CountDownLatch(1);
  
          // attach shutdown handler to catch control-c
          Runtime.getRuntime().addShutdownHook(new Thread("streams-wordcount-shutdown-hook") {
              @Override
              public void run() {
                  streams.close();
                  latch.countDown();
              }
          });
  
          try {
              streams.start();
              latch.await();
          } catch (final Throwable e) {
              System.exit(1);
          }
          System.exit(0);
      }
  }
  