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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.db.tries;
  
  import java.nio.ByteBuffer;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  import java.util.Random;
  import java.util.SortedMap;
  import java.util.TreeMap;
  
  import com.google.common.collect.ImmutableList;
  import org.junit.Assert;
  import org.junit.Test;
  
  import org.apache.cassandra.utils.bytecomparable.ByteComparable;
  
  import static org.apache.cassandra.db.tries.InMemoryTrieTestBase.*;
  import static org.apache.cassandra.db.tries.MergeTrieTest.removeDuplicates;
  
  public class CollectionMergeTrieTest
  {
      private static final int COUNT = 15000;
      private static final Random rand = new Random();
  
      @Test
      public void testDirect()
      {
          ByteComparable[] src1 = generateKeys(rand, COUNT);
          ByteComparable[] src2 = generateKeys(rand, COUNT);
          SortedMap<ByteComparable, ByteBuffer> content1 = new TreeMap<>(FORWARD_COMPARATOR);
          SortedMap<ByteComparable, ByteBuffer> content2 = new TreeMap<>(FORWARD_COMPARATOR);
  
          InMemoryTrie<ByteBuffer> trie1 = makeInMemoryTrie(src1, content1, true);
          InMemoryTrie<ByteBuffer> trie2 = makeInMemoryTrie(src2, content2, true);
  
          content1.putAll(content2);
          // construct directly, trie.merge() will defer to mergeWith on two sources
          Trie<ByteBuffer> union = new CollectionMergeTrie<>(ImmutableList.of(trie1, trie2), x -> x.iterator().next());
  
          assertSameContent(union, content1);
      }
  
      @Test
      public void testWithDuplicates()
      {
          ByteComparable[] src1 = generateKeys(rand, COUNT);
          ByteComparable[] src2 = generateKeys(rand, COUNT);
          SortedMap<ByteComparable, ByteBuffer> content1 = new TreeMap<>(FORWARD_COMPARATOR);
          SortedMap<ByteComparable, ByteBuffer> content2 = new TreeMap<>(FORWARD_COMPARATOR);
  
          InMemoryTrie<ByteBuffer> trie1 = makeInMemoryTrie(src1, content1, true);
          InMemoryTrie<ByteBuffer> trie2 = makeInMemoryTrie(src2, content2, true);
  
          addToInMemoryTrie(generateKeys(new Random(5), COUNT), content1, trie1, true);
          addToInMemoryTrie(generateKeys(new Random(5), COUNT), content2, trie2, true);
  
          content1.putAll(content2);
          Trie<ByteBuffer> union = new CollectionMergeTrie<>(ImmutableList.of(trie1, trie2), x -> x.iterator().next());
  
          assertSameContent(union, content1);
      }
  
      @Test
      public void testDistinct()
      {
          ByteComparable[] src1 = generateKeys(rand, COUNT);
          SortedMap<ByteComparable, ByteBuffer> content1 = new TreeMap<>(FORWARD_COMPARATOR);
          InMemoryTrie<ByteBuffer> trie1 = makeInMemoryTrie(src1, content1, true);
  
          ByteComparable[] src2 = generateKeys(rand, COUNT);
          src2 = removeDuplicates(src2, content1);
          SortedMap<ByteComparable, ByteBuffer> content2 = new TreeMap<>(FORWARD_COMPARATOR);
          InMemoryTrie<ByteBuffer> trie2 = makeInMemoryTrie(src2, content2, true);
  
          content1.putAll(content2);
          Trie<ByteBuffer> union = new CollectionMergeTrie.Distinct<>(ImmutableList.of(trie1, trie2));
  
          assertSameContent(union, content1);
      }
  
      @Test
      public void testMultiple()
      {
          for (int i = 0; i < 10; ++i)
          {
              testMultiple(rand.nextInt(10) + 5, COUNT / 10);
          }
      }
  
      @Test
      public void testMerge1()
      {
          testMultiple(1, COUNT / 10);
      }
  
      @Test
      public void testMerge2()
      {
          testMultiple(2, COUNT / 10);
      }
  
      @Test
      public void testMerge3()
      {
          testMultiple(3, COUNT / 10);
      }
  
      @Test
      public void testMerge5()
      {
          testMultiple(5, COUNT / 10);
      }
  
      @Test
      public void testMerge0()
      {
          testMultiple(0, COUNT / 10);
      }
  
      public void testMultiple(int mergeCount, int count)
      {
          testMultipleDistinct(mergeCount, count);
          testMultipleWithDuplicates(mergeCount, count);
      }
  
      public void testMultipleDistinct(int mergeCount, int count)
      {
          List<Trie<ByteBuffer>> tries = new ArrayList<>(mergeCount);
          SortedMap<ByteComparable, ByteBuffer> content = new TreeMap<>(FORWARD_COMPARATOR);
  
          for (int i = 0; i < mergeCount; ++i)
          {
              ByteComparable[] src = removeDuplicates(generateKeys(rand, count), content);
              Trie<ByteBuffer> trie = makeInMemoryTrie(src, content, true);
              tries.add(trie);
          }
  
          Trie<ByteBuffer> union = Trie.mergeDistinct(tries);
          assertSameContent(union, content);
      }
  
      public void testMultipleWithDuplicates(int mergeCount, int count)
      {
          List<Trie<ByteBuffer>> tries = new ArrayList<>(mergeCount);
          SortedMap<ByteComparable, ByteBuffer> content = new TreeMap<>(FORWARD_COMPARATOR);
          ByteComparable[][] keys = new ByteComparable[count][];
          for (int i = 0; i < mergeCount; ++i)
              keys[i] = generateKeys(rand, count);
  
          for (int i = 0; i < mergeCount; ++i)
          {
              ByteComparable[] src = Arrays.copyOf(keys[i], count + count / 10);
              // add duplicates from other tries
              if (mergeCount > 1)
              {
                  for (int j = count; j < src.length; ++j)
                      src[j] = keys[randomButNot(rand, mergeCount, i)][rand.nextInt(count)];
              }
  
              Trie<ByteBuffer> trie = makeInMemoryTrie(keys[i], content, true);
              tries.add(trie);
          }
  
          Trie<ByteBuffer> union = Trie.merge(tries, x -> x.iterator().next());
          assertSameContent(union, content);
  
          try
          {
              union = Trie.mergeDistinct(tries);
              assertSameContent(union, content);
              Assert.fail("Expected assertion error for duplicate keys.");
          }
          catch (AssertionError e)
          {
              // correct path
          }
      }
  
      private int randomButNot(Random rand, int bound, int avoid)
      {
          int r;
          do
          {
              r = rand.nextInt(bound);
          }
          while (r == avoid);
          return r;
      }
  }
  