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.kstream.internals;
  
  import org.apache.kafka.streams.kstream.Materialized;
  import org.apache.kafka.streams.processor.api.Processor;
  import org.apache.kafka.streams.processor.api.Record;
  import org.apache.kafka.streams.processor.internals.ProcessorNode;
  import org.apache.kafka.streams.state.TimestampedKeyValueStore;
  import org.apache.kafka.streams.state.ValueAndTimestamp;
  import org.apache.kafka.test.GenericInMemoryTimestampedKeyValueStore;
  import org.apache.kafka.test.InternalMockProcessorContext;
  
  import org.junit.jupiter.api.Test;
  
  import java.util.HashSet;
  import java.util.Set;
  
  import static java.util.Collections.emptySet;
  import static java.util.Collections.singleton;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertNotNull;
  
  public class KTableReduceTest {
  
      @Test
      public void shouldAddAndSubtract() {
          final InternalMockProcessorContext<String, Change<Set<String>>> context = new InternalMockProcessorContext<>();
  
          final Processor<String, Change<Set<String>>, String, Change<Set<String>>> reduceProcessor =
              new KTableReduce<String, Set<String>>(
                  new MaterializedInternal<>(Materialized.as("myStore")),
                  this::unionNotNullArgs,
                  this::differenceNotNullArgs
              ).get();
  
          final TimestampedKeyValueStore<String, Set<String>> myStore =
              new GenericInMemoryTimestampedKeyValueStore<>("myStore");
  
          context.register(myStore, null);
          reduceProcessor.init(context);
          context.setCurrentNode(new ProcessorNode<>("reduce", reduceProcessor, singleton("myStore")));
  
          reduceProcessor.process(new Record<>("A", new Change<>(singleton("a"), null), 10L));
          assertEquals(ValueAndTimestamp.make(singleton("a"), 10L), myStore.get("A"));
          reduceProcessor.process(new Record<>("A", new Change<>(singleton("b"), singleton("a")), 15L));
          assertEquals(ValueAndTimestamp.make(singleton("b"), 15L), myStore.get("A"));
          reduceProcessor.process(new Record<>("A", new Change<>(null, singleton("b")), 12L));
          assertEquals(ValueAndTimestamp.make(emptySet(), 15L), myStore.get("A"));
      }
  
      private Set<String> differenceNotNullArgs(final Set<String> left, final Set<String> right) {
          assertNotNull(left);
          assertNotNull(right);
  
          final HashSet<String> strings = new HashSet<>(left);
          strings.removeAll(right);
          return strings;
      }
  
      private Set<String> unionNotNullArgs(final Set<String> left, final Set<String> right) {
          assertNotNull(left);
          assertNotNull(right);
  
          final HashSet<String> strings = new HashSet<>();
          strings.addAll(left);
          strings.addAll(right);
          return strings;
      }
  }
  