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.arrow.algorithm.sort;
  
  import static org.junit.jupiter.api.Assertions.assertArrayEquals;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  import java.nio.charset.StandardCharsets;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Comparator;
  import java.util.List;
  import java.util.function.Function;
  import java.util.stream.Stream;
  import org.apache.arrow.memory.BufferAllocator;
  import org.apache.arrow.memory.RootAllocator;
  import org.apache.arrow.vector.BaseVariableWidthVector;
  import org.apache.arrow.vector.ValueVector;
  import org.apache.arrow.vector.VarCharVector;
  import org.apache.arrow.vector.util.Text;
  import org.junit.jupiter.api.AfterEach;
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.params.ParameterizedTest;
  import org.junit.jupiter.params.provider.Arguments;
  import org.junit.jupiter.params.provider.MethodSource;
  
  /** Test sorting variable width vectors with random data. */
  public class TestVariableWidthSorting<V extends BaseVariableWidthVector, U extends Comparable<U>> {
  
    static final int[] VECTOR_LENGTHS = new int[] {2, 5, 10, 50, 100, 1000, 3000};
  
    static final double[] NULL_FRACTIONS = {0, 0.1, 0.3, 0.5, 0.7, 0.9, 1};
  
    private BufferAllocator allocator;
  
    @BeforeEach
    public void prepare() {
      allocator = new RootAllocator(Integer.MAX_VALUE);
    }
  
    @AfterEach
    public void shutdown() {
      allocator.close();
    }
  
    @ParameterizedTest
    @MethodSource("getParameters")
    public void testSort(
        int length,
        double nullFraction,
        Function<BufferAllocator, V> vectorGenerator,
        TestSortingUtil.DataGenerator<V, U> dataGenerator) {
      sortOutOfPlace(length, nullFraction, vectorGenerator, dataGenerator);
    }
  
    void sortOutOfPlace(
        int length,
        double nullFraction,
        Function<BufferAllocator, V> vectorGenerator,
        TestSortingUtil.DataGenerator<V, U> dataGenerator) {
      try (V vector = vectorGenerator.apply(allocator)) {
        U[] array = dataGenerator.populate(vector, length, nullFraction);
        Arrays.sort(array, (Comparator<? super U>) new StringComparator());
  
        // sort the vector
        VariableWidthOutOfPlaceVectorSorter sorter = new VariableWidthOutOfPlaceVectorSorter();
        VectorValueComparator<V> comparator =
            DefaultVectorComparators.createDefaultComparator(vector);
  
        try (V sortedVec =
            (V) vector.getField().getFieldType().createNewSingleVector("", allocator, null)) {
          int dataSize = vector.getOffsetBuffer().getInt(vector.getValueCount() * 4L);
          sortedVec.allocateNew(dataSize, vector.getValueCount());
          sortedVec.setValueCount(vector.getValueCount());
  
          sorter.sortOutOfPlace(vector, sortedVec, comparator);
  
          // verify results
          verifyResults(sortedVec, (String[]) array);
        }
      }
    }
  
    public static Stream<Arguments> getParameters() {
      List<Arguments> params = new ArrayList<>();
      for (int length : VECTOR_LENGTHS) {
        for (double nullFrac : NULL_FRACTIONS) {
          params.add(
              Arguments.of(
                  length,
                  nullFrac,
                  (Function<BufferAllocator, VarCharVector>)
                      allocator -> new VarCharVector("vector", allocator),
                  TestSortingUtil.STRING_GENERATOR));
        }
      }
      return params.stream();
    }
  
    /** Verify results as byte arrays. */
    public static <V extends ValueVector> void verifyResults(V vector, String[] expected) {
      assertEquals(vector.getValueCount(), expected.length);
      for (int i = 0; i < expected.length; i++) {
        if (expected[i] == null) {
          assertTrue(vector.isNull(i));
        } else {
          assertArrayEquals(
              ((Text) vector.getObject(i)).getBytes(), expected[i].getBytes(StandardCharsets.UTF_8));
        }
      }
    }
  
    /**
     * String comparator with the same behavior as that of {@link
     * DefaultVectorComparators.VariableWidthComparator}.
     */
    static class StringComparator implements Comparator<String> {
  
      @Override
      public int compare(String str1, String str2) {
        if (str1 == null || str2 == null) {
          if (str1 == null && str2 == null) {
            return 0;
          }
  
          return str1 == null ? -1 : 1;
        }
  
        byte[] bytes1 = str1.getBytes(StandardCharsets.UTF_8);
        byte[] bytes2 = str2.getBytes(StandardCharsets.UTF_8);
  
        for (int i = 0; i < bytes1.length && i < bytes2.length; i++) {
          if (bytes1[i] != bytes2[i]) {
            return (bytes1[i] & 0xff) < (bytes2[i] & 0xff) ? -1 : 1;
          }
        }
        return bytes1.length - bytes2.length;
      }
    }
  }
  