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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.kafka.streams.state.internals;
  
  import org.apache.kafka.common.metrics.Metrics;
  import org.apache.kafka.common.serialization.Serdes;
  import org.apache.kafka.common.utils.Bytes;
  import org.apache.kafka.common.utils.LogContext;
  import org.apache.kafka.streams.KeyValue;
  import org.apache.kafka.streams.processor.internals.MockStreamsMetrics;
  import org.apache.kafka.streams.query.Position;
  import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
  import org.apache.kafka.test.InternalMockProcessorContext;
  import org.apache.kafka.test.MockRecordCollector;
  import org.apache.kafka.test.TestUtils;
  
  import org.junit.jupiter.api.AfterEach;
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  public class SegmentIteratorTest {
  
      private final RocksDBMetricsRecorder rocksDBMetricsRecorder =
          new RocksDBMetricsRecorder("metrics-scope", "store-name");
      private final KeyValueSegment segmentOne =
          new KeyValueSegment("one", "one", 0, Position.emptyPosition(), rocksDBMetricsRecorder);
      private final KeyValueSegment segmentTwo =
          new KeyValueSegment("two", "window", 1, Position.emptyPosition(), rocksDBMetricsRecorder);
      private final HasNextCondition hasNextCondition = Iterator::hasNext;
  
      private SegmentIterator<KeyValueSegment> iterator = null;
  
      @BeforeEach
      public void before() {
          final InternalMockProcessorContext<String, String> context = new InternalMockProcessorContext<>(
              TestUtils.tempDirectory(),
              Serdes.String(),
              Serdes.String(),
              new MockRecordCollector(),
              new ThreadCache(
                  new LogContext("testCache "),
                  0,
                  new MockStreamsMetrics(new Metrics())));
          segmentOne.init(context, segmentOne);
          segmentTwo.init(context, segmentTwo);
          segmentOne.put(Bytes.wrap("a".getBytes()), "1".getBytes());
          segmentOne.put(Bytes.wrap("b".getBytes()), "2".getBytes());
          segmentTwo.put(Bytes.wrap("c".getBytes()), "3".getBytes());
          segmentTwo.put(Bytes.wrap("d".getBytes()), "4".getBytes());
      }
  
      @AfterEach
      public void closeSegments() {
          if (iterator != null) {
              iterator.close();
              iterator = null;
          }
          segmentOne.close();
          segmentTwo.close();
      }
  
      @Test
      public void shouldIterateOverAllSegments() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentOne, segmentTwo).iterator(),
              hasNextCondition,
              Bytes.wrap("a".getBytes()),
              Bytes.wrap("z".getBytes()),
              true);
  
          assertTrue(iterator.hasNext());
          assertEquals("a", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("a", "1"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("b", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("b", "2"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("c", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("c", "3"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("d", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("d", "4"), toStringKeyValue(iterator.next()));
  
          assertFalse(iterator.hasNext());
      }
  
      @Test
      public void shouldIterateOverAllSegmentsWhenNullKeyFromKeyTo() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentOne, segmentTwo).iterator(),
              hasNextCondition,
              null,
              null,
              true);
  
          assertTrue(iterator.hasNext());
          assertEquals("a", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("a", "1"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("b", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("b", "2"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("c", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("c", "3"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("d", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("d", "4"), toStringKeyValue(iterator.next()));
  
          assertFalse(iterator.hasNext());
      }
  
      @Test
      public void shouldIterateBackwardOverAllSegments() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentTwo, segmentOne).iterator(), //store should pass the segments in the right order
              hasNextCondition,
              Bytes.wrap("a".getBytes()),
              Bytes.wrap("z".getBytes()),
              false);
  
          assertTrue(iterator.hasNext());
          assertEquals("d", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("d", "4"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("c", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("c", "3"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("b", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("b", "2"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("a", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("a", "1"), toStringKeyValue(iterator.next()));
  
          assertFalse(iterator.hasNext());
      }
  
      @Test
      public void shouldIterateBackwardOverAllSegmentsWhenNullKeyFromKeyTo() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentTwo, segmentOne).iterator(), //store should pass the segments in the right order
              hasNextCondition,
              null,
              null,
              false);
  
          assertTrue(iterator.hasNext());
          assertEquals("d", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("d", "4"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("c", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("c", "3"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("b", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("b", "2"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("a", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("a", "1"), toStringKeyValue(iterator.next()));
  
          assertFalse(iterator.hasNext());
      }
  
      @Test
      public void shouldNotThrowExceptionOnHasNextWhenStoreClosed() {
          iterator = new SegmentIterator<>(
              Collections.singletonList(segmentOne).iterator(),
              hasNextCondition,
              Bytes.wrap("a".getBytes()),
              Bytes.wrap("z".getBytes()),
              true);
  
          iterator.currentIterator = segmentOne.all();
          segmentOne.close();
          assertFalse(iterator.hasNext());
      }
  
      @Test
      public void shouldOnlyIterateOverSegmentsInBackwardRange() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentOne, segmentTwo).iterator(),
              hasNextCondition,
              Bytes.wrap("a".getBytes()),
              Bytes.wrap("b".getBytes()),
              false);
  
          assertTrue(iterator.hasNext());
          assertEquals("b", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("b", "2"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("a", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("a", "1"), toStringKeyValue(iterator.next()));
  
          assertFalse(iterator.hasNext());
      }
  
      @Test
      public void shouldOnlyIterateOverSegmentsInBackwardRangeWhenNullKeyFrom() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentOne, segmentTwo).iterator(),
              hasNextCondition,
              null,
              Bytes.wrap("b".getBytes()),
              false);
  
          assertTrue(iterator.hasNext());
          assertEquals("b", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("b", "2"), toStringKeyValue(iterator.next()));
  
  
          assertTrue(iterator.hasNext());
          assertEquals("a", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("a", "1"), toStringKeyValue(iterator.next()));
  
          assertFalse(iterator.hasNext());
      }
  
      @Test
      public void shouldOnlyIterateOverSegmentsInBackwardRangeWhenNullKeyTo() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentOne, segmentTwo).iterator(),
              hasNextCondition,
              Bytes.wrap("c".getBytes()),
              null,
              false);
  
          assertTrue(iterator.hasNext());
          assertEquals("d", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("d", "4"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("c", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("c", "3"), toStringKeyValue(iterator.next()));
  
          assertFalse(iterator.hasNext());
      }
  
      @Test
      public void shouldOnlyIterateOverSegmentsInRange() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentOne, segmentTwo).iterator(),
              hasNextCondition,
              Bytes.wrap("a".getBytes()),
              Bytes.wrap("b".getBytes()),
              true);
  
          assertTrue(iterator.hasNext());
          assertEquals("a", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("a", "1"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("b", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("b", "2"), toStringKeyValue(iterator.next()));
  
          assertFalse(iterator.hasNext());
      }
  
      @Test
      public void shouldOnlyIterateOverSegmentsInRangeWhenNullKeyFrom() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentOne, segmentTwo).iterator(),
              hasNextCondition,
              null,
              Bytes.wrap("c".getBytes()),
              true);
  
          assertTrue(iterator.hasNext());
          assertEquals("a", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("a", "1"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("b", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("b", "2"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("c", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("c", "3"), toStringKeyValue(iterator.next()));
  
          assertFalse(iterator.hasNext());
      }
  
      @Test
      public void shouldOnlyIterateOverSegmentsInRangeWhenNullKeyTo() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentOne, segmentTwo).iterator(),
              hasNextCondition,
              Bytes.wrap("b".getBytes()),
              null,
              true);
  
          assertTrue(iterator.hasNext());
          assertEquals("b", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("b", "2"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("c", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("c", "3"), toStringKeyValue(iterator.next()));
  
          assertTrue(iterator.hasNext());
          assertEquals("d", new String(iterator.peekNextKey().get()));
          assertEquals(KeyValue.pair("d", "4"), toStringKeyValue(iterator.next()));
  
          assertFalse(iterator.hasNext());
      }
  
      @Test
      public void shouldThrowNoSuchElementOnPeekNextKeyIfNoNext() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentOne, segmentTwo).iterator(),
              hasNextCondition,
              Bytes.wrap("f".getBytes()),
              Bytes.wrap("h".getBytes()),
              true);
  
          assertThrows(NoSuchElementException.class, () -> iterator.peekNextKey());
      }
  
      @Test
      public void shouldThrowNoSuchElementOnNextIfNoNext() {
          iterator = new SegmentIterator<>(
              Arrays.asList(segmentOne, segmentTwo).iterator(),
              hasNextCondition,
              Bytes.wrap("f".getBytes()),
              Bytes.wrap("h".getBytes()),
              true);
  
          assertThrows(NoSuchElementException.class, () -> iterator.next());
      }
  
      private KeyValue<String, String> toStringKeyValue(final KeyValue<Bytes, byte[]> binaryKv) {
          return KeyValue.pair(new String(binaryKv.key.get()), new String(binaryKv.value));
      }
  }
  