/**
 * Copyright (C) 2014-2016 LinkedIn Corp. (pinot-core@linkedin.com)
 *
 * Licensed 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 com.linkedin.pinot.util;

import com.linkedin.pinot.common.utils.Pairs;
import com.linkedin.pinot.core.util.IntDoubleIndexedPriorityQueue;
import it.unimi.dsi.fastutil.ints.Int2DoubleMap;
import it.unimi.dsi.fastutil.ints.Int2DoubleOpenHashMap;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import org.testng.Assert;
import org.testng.annotations.Test;


/**
 * Unit test for {@link IntDoubleIndexedPriorityQueue} class
 */
public class IntDoubleIndexedPriorityQueueTest {
  private static final int NUM_RECORDS = 1000;

  /**
   * Test for max heap mode.
   */
  @Test
  public void testMax() {
    test(false /* minHeap */);
  }

  /**
   * Test for min heap mode.
   */
  @Test
  public void testMin() {
    test(true /* minHeap */);
  }

  /**
   * Helper method builds the priority queue, randomly updates elements and
   * then asserts the following:
   * <ul>
   *   <li> Elements are popped from the priority queue in the expected order. </li>
   *   <li> Size of the priority queue is as expected (after elements are updated). </li>
   * </ul>
   * @param minHeap Min or max mode
   */
  public void test(boolean minHeap) {
    Random random = new Random(0);

    IntDoubleIndexedPriorityQueue pq = new IntDoubleIndexedPriorityQueue(NUM_RECORDS, minHeap);
    Int2DoubleOpenHashMap map = new Int2DoubleOpenHashMap(NUM_RECORDS);

    // Initialize the priority queue.
    for (int i = 0; i < NUM_RECORDS; i++) {
      double value = random.nextDouble();
      pq.put(i, value);
      map.put(i, value);
    }

    // Update some records randomly
    for (int i = 0; i < NUM_RECORDS; i++) {
      int key = random.nextInt(NUM_RECORDS);
      double value = random.nextDouble();
      pq.put(key, value);
      map.put(key, value);
    }

    // Transfer the map into list so it can be sorted.
    List<Pairs.IntDoublePair> list = new ArrayList<>(NUM_RECORDS);
    for (Int2DoubleMap.Entry entry : map.int2DoubleEntrySet()) {
      list.add(new Pairs.IntDoublePair(entry.getKey(), entry.getValue()));
    }

    // Comparison for min heap is the same as that for ascending order.
    boolean descendingOrder = !minHeap;
    Collections.sort(list, new Pairs.IntDoubleComparator(descendingOrder));

    // Ensure that elements are popped from priority queue in the expected order.
    int i = 0;
    while (!pq.isEmpty()) {
      Pairs.IntDoublePair actual = pq.poll();
      Pairs.IntDoublePair expected = list.get(i++);

      Assert.assertEquals(actual.getIntValue(), expected.getIntValue());
      Assert.assertEquals(actual.getDoubleValue(), expected.getDoubleValue());
    }

    // Assert that priority queue had expected number of elements.
    Assert.assertEquals(i, list.size());
  }
}