/**
 * 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.pinot.queries;

import com.tdunning.math.stats.TDigest;
import it.unimi.dsi.fastutil.doubles.DoubleList;
import java.io.File;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Random;
import org.apache.commons.io.FileUtils;
import org.apache.pinot.common.response.broker.BrokerResponseNative;
import org.apache.pinot.core.operator.blocks.results.AggregationResultsBlock;
import org.apache.pinot.core.operator.blocks.results.GroupByResultsBlock;
import org.apache.pinot.core.operator.query.AggregationOperator;
import org.apache.pinot.core.operator.query.GroupByOperator;
import org.apache.pinot.core.query.aggregation.function.PercentileTDigestAggregationFunction;
import org.apache.pinot.core.query.aggregation.groupby.AggregationGroupByResult;
import org.apache.pinot.core.query.aggregation.groupby.GroupKeyGenerator;
import org.apache.pinot.segment.local.indexsegment.immutable.ImmutableSegmentLoader;
import org.apache.pinot.segment.local.segment.creator.impl.SegmentIndexCreationDriverImpl;
import org.apache.pinot.segment.local.segment.readers.GenericRowRecordReader;
import org.apache.pinot.segment.spi.ImmutableSegment;
import org.apache.pinot.segment.spi.IndexSegment;
import org.apache.pinot.segment.spi.creator.SegmentGeneratorConfig;
import org.apache.pinot.spi.config.table.TableConfig;
import org.apache.pinot.spi.config.table.TableType;
import org.apache.pinot.spi.data.DimensionFieldSpec;
import org.apache.pinot.spi.data.FieldSpec;
import org.apache.pinot.spi.data.MetricFieldSpec;
import org.apache.pinot.spi.data.Schema;
import org.apache.pinot.spi.data.readers.GenericRow;
import org.apache.pinot.spi.data.readers.RecordReader;
import org.apache.pinot.spi.utils.ReadMode;
import org.apache.pinot.spi.utils.builder.TableConfigBuilder;
import org.testng.annotations.AfterClass;
import org.testng.annotations.BeforeClass;
import org.testng.annotations.Test;

import static org.testng.Assert.assertEquals;
import static org.testng.Assert.assertNotNull;


/**
 * Tests for PERCENTILE_TDIGEST aggregation function.
 *
 * <ul>
 *   <li>Generates a segment with a double column, a TDigest column and a group-by column</li>
 *   <li>Runs aggregation and group-by queries on the generated segment</li>
 *   <li>
 *     Compares the results for PERCENTILE_TDIGEST on double column and TDigest column with results for PERCENTILE on
 *     double column
 *   </li>
 * </ul>
 */
public class PercentileTDigestQueriesTest extends BaseQueriesTest {
  protected static final File INDEX_DIR = new File(FileUtils.getTempDirectory(), "PercentileTDigestQueriesTest");
  protected static final String TABLE_NAME = "testTable";
  protected static final String SEGMENT_NAME = "testSegment";

  protected static final int NUM_ROWS = 1000;
  protected static final double VALUE_RANGE = Integer.MAX_VALUE;
  protected static final double DELTA = 0.05 * VALUE_RANGE; // Allow 5% quantile error
  protected static final String DOUBLE_COLUMN = "doubleColumn";
  protected static final String TDIGEST_COLUMN = "tDigestColumn";
  protected static final String GROUP_BY_COLUMN = "groupByColumn";
  protected static final String[] GROUPS = new String[]{"G1", "G2", "G3"};
  protected static final long RANDOM_SEED = System.nanoTime();
  protected static final Random RANDOM = new Random(RANDOM_SEED);
  protected static final String ERROR_MESSAGE = "Random seed: " + RANDOM_SEED;

  private IndexSegment _indexSegment;
  private List<IndexSegment> _indexSegments;

  @Override
  protected String getFilter() {
    return ""; // No filtering required for this test.
  }

  @Override
  protected IndexSegment getIndexSegment() {
    return _indexSegment;
  }

  @Override
  protected List<IndexSegment> getIndexSegments() {
    return _indexSegments;
  }

  @BeforeClass
  public void setUp()
      throws Exception {
    FileUtils.deleteQuietly(INDEX_DIR);

    buildSegment();
    ImmutableSegment immutableSegment = ImmutableSegmentLoader.load(new File(INDEX_DIR, SEGMENT_NAME), ReadMode.mmap);
    _indexSegment = immutableSegment;
    _indexSegments = Arrays.asList(immutableSegment, immutableSegment);
  }

  protected void buildSegment()
      throws Exception {
    List<GenericRow> rows = new ArrayList<>(NUM_ROWS);
    for (int i = 0; i < NUM_ROWS; i++) {
      GenericRow row = new GenericRow();

      double value = RANDOM.nextDouble() * VALUE_RANGE;
      row.putValue(DOUBLE_COLUMN, value);

      TDigest tDigest = TDigest.createMergingDigest(PercentileTDigestAggregationFunction.DEFAULT_TDIGEST_COMPRESSION);
      tDigest.add(value);
      ByteBuffer byteBuffer = ByteBuffer.allocate(tDigest.byteSize());
      tDigest.asBytes(byteBuffer);
      row.putValue(TDIGEST_COLUMN, byteBuffer.array());

      String group = GROUPS[RANDOM.nextInt(GROUPS.length)];
      row.putValue(GROUP_BY_COLUMN, group);

      rows.add(row);
    }

    Schema schema = new Schema();
    schema.addField(new MetricFieldSpec(DOUBLE_COLUMN, FieldSpec.DataType.DOUBLE));
    schema.addField(new MetricFieldSpec(TDIGEST_COLUMN, FieldSpec.DataType.BYTES));
    schema.addField(new DimensionFieldSpec(GROUP_BY_COLUMN, FieldSpec.DataType.STRING, true));
    TableConfig tableConfig = new TableConfigBuilder(TableType.OFFLINE).setTableName(TABLE_NAME).build();

    SegmentGeneratorConfig config = new SegmentGeneratorConfig(tableConfig, schema);
    config.setOutDir(INDEX_DIR.getPath());
    config.setTableName(TABLE_NAME);
    config.setSegmentName(SEGMENT_NAME);
    config.setRawIndexCreationColumns(Collections.singletonList(TDIGEST_COLUMN));

    SegmentIndexCreationDriverImpl driver = new SegmentIndexCreationDriverImpl();
    try (RecordReader recordReader = new GenericRowRecordReader(rows)) {
      driver.init(config, recordReader);
      driver.build();
    }
  }

  @Test
  public void testInnerSegmentAggregation() {
    // For inner segment case, percentile does not affect the intermediate result
    AggregationOperator aggregationOperator = getOperator(getAggregationQuery(0));
    AggregationResultsBlock resultsBlock = aggregationOperator.nextBlock();
    List<Object> aggregationResult = resultsBlock.getResults();
    assertNotNull(aggregationResult);
    assertEquals(aggregationResult.size(), 6);
    DoubleList doubleList0 = (DoubleList) aggregationResult.get(0);
    Collections.sort(doubleList0);
    assertTDigest((TDigest) aggregationResult.get(1), doubleList0);
    assertTDigest((TDigest) aggregationResult.get(2), doubleList0);

    DoubleList doubleList3 = (DoubleList) aggregationResult.get(3);
    Collections.sort(doubleList3);
    assertEquals(doubleList3, doubleList0);
    assertTDigest((TDigest) aggregationResult.get(4), doubleList0);
    assertTDigest((TDigest) aggregationResult.get(5), doubleList0);
  }

  @Test
  public void testInterSegmentAggregation() {
    for (int percentile = 0; percentile <= 100; percentile++) {
      BrokerResponseNative brokerResponse = getBrokerResponse(getAggregationQuery(percentile));
      Object[] results = brokerResponse.getResultTable().getRows().get(0);
      assertEquals(results.length, 6);
      double expectedResult = (Double) results[0];
      for (int i = 1; i < 6; i++) {
        assertEquals((Double) results[i], expectedResult, DELTA, ERROR_MESSAGE);
      }
    }
  }

  @Test
  public void testInnerSegmentGroupBy() {
    // For inner segment case, percentile does not affect the intermediate result
    GroupByOperator groupByOperator = getOperator(getGroupByQuery(0));
    GroupByResultsBlock resultsBlock = groupByOperator.nextBlock();
    AggregationGroupByResult groupByResult = resultsBlock.getAggregationGroupByResult();
    assertNotNull(groupByResult);
    Iterator<GroupKeyGenerator.GroupKey> groupKeyIterator = groupByResult.getGroupKeyIterator();
    while (groupKeyIterator.hasNext()) {
      int groupId = groupKeyIterator.next()._groupId;
      DoubleList doubleList0 = (DoubleList) groupByResult.getResultForGroupId(0, groupId);
      Collections.sort(doubleList0);
      assertTDigest((TDigest) groupByResult.getResultForGroupId(1, groupId), doubleList0);
      assertTDigest((TDigest) groupByResult.getResultForGroupId(2, groupId), doubleList0);

      DoubleList doubleList3 = (DoubleList) groupByResult.getResultForGroupId(3, groupId);
      Collections.sort(doubleList3);
      assertEquals(doubleList3, doubleList0);
      assertTDigest((TDigest) groupByResult.getResultForGroupId(4, groupId), doubleList0);
      assertTDigest((TDigest) groupByResult.getResultForGroupId(5, groupId), doubleList0);
    }
  }

  @Test
  public void testInterSegmentGroupBy() {
    for (int percentile = 0; percentile <= 100; percentile++) {
      BrokerResponseNative brokerResponse = getBrokerResponse(getGroupByQuery(percentile));
      List<Object[]> rows = brokerResponse.getResultTable().getRows();
      assertEquals(rows.size(), 3);
      for (Object[] row : rows) {
        assertEquals(row.length, 6);
        double expectedResult = (Double) row[0];
        for (int i = 1; i < 6; i++) {
          assertEquals((Double) row[i], expectedResult, DELTA, ERROR_MESSAGE);
        }
      }
    }
  }

  protected String getAggregationQuery(int percentile) {
    return String.format("SELECT PERCENTILE%1$d(%2$s), PERCENTILETDIGEST%1$d(%2$s), PERCENTILETDIGEST%1$d(%3$s), "
            + "PERCENTILE(%2$s, %1$d), PERCENTILETDIGEST(%2$s, %1$d), PERCENTILETDIGEST(%3$s, %1$d) FROM %4$s",
        percentile,
        DOUBLE_COLUMN, TDIGEST_COLUMN, TABLE_NAME);
  }

  private String getGroupByQuery(int percentile) {
    return String.format("%s GROUP BY %s", getAggregationQuery(percentile), GROUP_BY_COLUMN);
  }

  private void assertTDigest(TDigest tDigest, DoubleList doubleList) {
    for (int percentile = 0; percentile <= 100; percentile++) {
      double expected;
      if (percentile == 100) {
        expected = doubleList.getDouble(doubleList.size() - 1);
      } else {
        expected = doubleList.getDouble(doubleList.size() * percentile / 100);
      }
      assertEquals(tDigest.quantile(percentile / 100.0), expected, DELTA, ERROR_MESSAGE);
    }
  }

  @Test
  public void testSmartTDigest() {
    // Inner segment
    // For inner segment case, percentile does not affect the intermediate result
    AggregationOperator aggregationOperator = getOperator(getSmartTDigestQuery(0));
    AggregationResultsBlock resultsBlock = aggregationOperator.nextBlock();
    List<Object> aggregationResult = resultsBlock.getResults();
    assertNotNull(aggregationResult);
    assertEquals(aggregationResult.size(), 4);
    DoubleList doubleList0 = (DoubleList) aggregationResult.get(0);
    Collections.sort(doubleList0);
    DoubleList doubleList1 = (DoubleList) aggregationResult.get(1);
    Collections.sort(doubleList1);
    assertEquals(doubleList1, doubleList0);
    TDigest tDigest2 = (TDigest) aggregationResult.get(2);
    TDigest tDigest3 = (TDigest) aggregationResult.get(3);
    assertTDigest(tDigest2, doubleList0);
    assertTDigest(tDigest3, doubleList0);

    // Inter segments
    for (int percentile = 0; percentile <= 100; percentile++) {
      BrokerResponseNative brokerResponse = getBrokerResponse(getSmartTDigestQuery(percentile));
      Object[] results = brokerResponse.getResultTable().getRows().get(0);
      assertEquals(results.length, 4);
      double expectedResult = (double) results[0];
      assertEquals(results[1], expectedResult);
      assertEquals((double) results[2], expectedResult, DELTA, ERROR_MESSAGE);
      assertEquals((double) results[3], expectedResult, DELTA, ERROR_MESSAGE);
    }
  }

  protected String getSmartTDigestQuery(int percentile) {
    return String.format("SELECT PERCENTILE(%2$s, %1$d), PERCENTILESMARTTDIGEST(%2$s, %1$d), "
            + "PERCENTILETDIGEST(%2$s, %1$d), PERCENTILESMARTTDIGEST(%2$s, %1$d, 'threshold=10') FROM %3$s", percentile,
        DOUBLE_COLUMN, TABLE_NAME);
  }

  @AfterClass
  public void tearDown() {
    _indexSegment.destroy();
    FileUtils.deleteQuietly(INDEX_DIR);
  }
}