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   * Licensed to the Apache Software Foundation (ASF) under one
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   * 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.
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  package org.apache.cassandra.io.sstable;
  
  import java.nio.ByteBuffer;
  import java.time.Duration;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.List;
  import java.util.Set;
  import java.util.concurrent.CopyOnWriteArraySet;
  import java.util.concurrent.CyclicBarrier;
  import java.util.concurrent.ThreadLocalRandom;
  import java.util.function.Supplier;
  import java.util.regex.Pattern;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import com.google.common.collect.Sets;
  import com.google.common.primitives.UnsignedBytes;
  import org.junit.Test;
  
  import org.apache.cassandra.concurrent.ExecutorPlus;
  import org.apache.cassandra.utils.TimeUUID;
  import org.awaitility.Awaitility;
  
  import static org.apache.cassandra.concurrent.ExecutorFactory.Global.executorFactory;
  import static org.assertj.core.api.Assertions.assertThat;
  import static org.quicktheories.QuickTheory.qt;
  import static org.quicktheories.generators.SourceDSL.longs;
  
  public class SSTableIdTest
  {
      @Test
      public void testSequenceBasedIdProperties()
      {
          testSSTableIdProperties(SequenceBasedSSTableId.Builder.instance);
      }
  
      @Test
      public void testUUIDBasedIdProperties()
      {
          testSSTableIdProperties(UUIDBasedSSTableId.Builder.instance);
      }
  
      private void testSSTableIdProperties(SSTableId.Builder<?> builder)
      {
          List<SSTableId> ids = Stream.generate(builder.generator(Stream.empty()))
                                      .limit(100).collect(Collectors.toList());
          assertThat(ids).isSorted();
          assertThat(Sets.newHashSet(ids)).hasSameSizeAs(ids);
  
          List<ByteBuffer> serIds = ids.stream().map(SSTableId::asBytes).collect(Collectors.toList());
          assertThat(serIds).isSortedAccordingTo((o1, o2) -> UnsignedBytes.lexicographicalComparator().compare(o1.array(), o2.array()));
  
          List<SSTableId> deserIds = serIds.stream().map(builder::fromBytes).collect(Collectors.toList());
          assertThat(deserIds).containsExactlyElementsOf(ids);
  
          List<String> stringifiedIds = ids.stream().map(SSTableId::toString).collect(Collectors.toList());
          if (!(builder instanceof SequenceBasedSSTableId.Builder))
          {
              // the legacy string representation is not sortable
              assertThat(stringifiedIds).isSorted();
          }
  
          List<SSTableId> destringifiedIds = stringifiedIds.stream().map(builder::fromString).collect(Collectors.toList());
          assertThat(destringifiedIds).containsExactlyElementsOf(ids);
  
          generatorFuzzTest(builder);
      }
  
      @Test
      public void testUUIDBytesSerDe()
      {
          qt().forAll(longs().all(), longs().all()).checkAssert((msb, lsb) -> {
              msb = (msb & ~0xf000) | 0x1000; // v1
              TimeUUID uuid = TimeUUID.fromBytes(msb, lsb);
              UUIDBasedSSTableId id = new UUIDBasedSSTableId(uuid);
  
              testBytesSerialization(id);
              testStringSerialization(id);
          });
      }
  
      private void testBytesSerialization(UUIDBasedSSTableId id)
      {
          ByteBuffer buf = id.asBytes();
          assertThat(buf.remaining()).isEqualTo(UUIDBasedSSTableId.BYTES_LEN);
          assertThat(UUIDBasedSSTableId.Builder.instance.isUniqueIdentifier(buf)).isTrue();
          assertThat(SequenceBasedSSTableId.Builder.instance.isUniqueIdentifier(buf)).isFalse();
          SSTableId fromBytes = SSTableIdFactory.instance.fromBytes(buf);
          assertThat(fromBytes).isEqualTo(id);
      }
  
      private void testStringSerialization(UUIDBasedSSTableId id)
      {
          String s = id.toString();
          assertThat(s).hasSize(UUIDBasedSSTableId.STRING_LEN);
          assertThat(s).matches(Pattern.compile("[0-9a-z]{4}_[0-9a-z]{4}_[0-9a-z]{18}"));
          assertThat(UUIDBasedSSTableId.Builder.instance.isUniqueIdentifier(s)).isTrue();
          assertThat(SequenceBasedSSTableId.Builder.instance.isUniqueIdentifier(s)).isFalse();
          SSTableId fromString = SSTableIdFactory.instance.fromString(s);
          assertThat(fromString).isEqualTo(id);
      }
  
      @Test
      public void testComparator()
      {
          List<SSTableId> ids = new ArrayList<>(Collections.nCopies(300, null));
          for (int i = 0; i < 100; i++)
          {
              ids.set(i + 100, new SequenceBasedSSTableId(ThreadLocalRandom.current().nextInt(1000000)));
              ids.set(i, new UUIDBasedSSTableId(TimeUUID.Generator.atUnixMillis(ThreadLocalRandom.current().nextLong(10000), 0)));
          }
  
          List<SSTableId> shuffledIds = new ArrayList<>(ids);
          Collections.shuffle(shuffledIds);
          assertThat(shuffledIds).isNotEqualTo(ids);
  
          List<SSTableId> sortedIds = new ArrayList<>(shuffledIds);
          sortedIds.sort(SSTableIdFactory.COMPARATOR);
          assertThat(sortedIds).isNotEqualTo(shuffledIds);
          assertThat(sortedIds).isSortedAccordingTo(SSTableIdFactory.COMPARATOR);
  
          assertThat(sortedIds.subList(0, 100)).containsOnlyNulls();
          assertThat(sortedIds.subList(100, 200)).allMatch(id -> id instanceof SequenceBasedSSTableId);
          assertThat(sortedIds.subList(200, 300)).allMatch(id -> id instanceof UUIDBasedSSTableId);
  
          assertThat(sortedIds.subList(100, 200)).isSortedAccordingTo(Comparator.comparing(o -> ((SequenceBasedSSTableId) o)));
          assertThat(sortedIds.subList(200, 300)).isSortedAccordingTo(Comparator.comparing(o -> ((UUIDBasedSSTableId) o)));
      }
  
      private static <T extends SSTableId> void generatorFuzzTest(SSTableId.Builder<T> builder)
      {
          final int NUM_THREADS = 10, IDS_PER_THREAD = 10;
          Set<SSTableId> ids = new CopyOnWriteArraySet<>();
          Supplier<T> generator = builder.generator(Stream.empty());
          ExecutorPlus service = executorFactory().pooled("test", NUM_THREADS);
          CyclicBarrier barrier = new CyclicBarrier(NUM_THREADS);
          for (int i = 0; i < NUM_THREADS; i++)
          {
              service.submit(() -> {
                  for (int k = 0; k < IDS_PER_THREAD; k++)
                  {
                      barrier.await();
                      ids.add(generator.get());
                  }
                  return null;
              });
          }
  
          Awaitility.await().atMost(Duration.ofSeconds(10)).untilAsserted(() -> assertThat(service.getCompletedTaskCount()).isEqualTo(NUM_THREADS));
          assertThat(ids).hasSize(NUM_THREADS * IDS_PER_THREAD);
      }
  }
  