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 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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
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package org.elasticsearch.search.aggregations.metrics;

import org.apache.lucene.document.IntPoint;
import org.apache.lucene.document.NumericDocValuesField;
import org.apache.lucene.document.SortedNumericDocValuesField;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.RandomIndexWriter;
import org.apache.lucene.search.DocValuesFieldExistsQuery;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.MatchAllDocsQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.store.Directory;
import org.apache.lucene.util.NumericUtils;
import org.elasticsearch.common.CheckedConsumer;
import org.elasticsearch.index.mapper.MappedFieldType;
import org.elasticsearch.index.mapper.NumberFieldMapper;
import org.elasticsearch.search.aggregations.AggregatorTestCase;
import org.elasticsearch.search.aggregations.metrics.AvgAggregationBuilder;
import org.elasticsearch.search.aggregations.metrics.AvgAggregator;
import org.elasticsearch.search.aggregations.metrics.InternalAvg;

import java.io.IOException;
import java.util.Arrays;
import java.util.function.Consumer;

import static java.util.Collections.singleton;

public class AvgAggregatorTests extends AggregatorTestCase {

    public void testNoDocs() throws IOException {
        testCase(new MatchAllDocsQuery(), iw -> {
            // Intentionally not writing any docs
        }, avg -> {
            assertEquals(Double.NaN, avg.getValue(), 0);
        });
    }

    public void testNoMatchingField() throws IOException {
        testCase(new MatchAllDocsQuery(), iw -> {
            iw.addDocument(singleton(new SortedNumericDocValuesField("wrong_number", 7)));
            iw.addDocument(singleton(new SortedNumericDocValuesField("wrong_number", 3)));
        }, avg -> {
            assertEquals(Double.NaN, avg.getValue(), 0);
        });
    }

    public void testSomeMatchesSortedNumericDocValues() throws IOException {
        testCase(new DocValuesFieldExistsQuery("number"), iw -> {
            iw.addDocument(singleton(new SortedNumericDocValuesField("number", 7)));
            iw.addDocument(singleton(new SortedNumericDocValuesField("number", 2)));
            iw.addDocument(singleton(new SortedNumericDocValuesField("number", 3)));
        }, avg -> {
            assertEquals(4, avg.getValue(), 0);
        });
    }

    public void testSomeMatchesNumericDocValues() throws IOException {
        testCase(new DocValuesFieldExistsQuery("number"), iw -> {
            iw.addDocument(singleton(new NumericDocValuesField("number", 7)));
            iw.addDocument(singleton(new NumericDocValuesField("number", 2)));
            iw.addDocument(singleton(new NumericDocValuesField("number", 3)));
        }, avg -> {
            assertEquals(4, avg.getValue(), 0);
        });
    }

    public void testQueryFiltering() throws IOException {
        testCase(IntPoint.newRangeQuery("number", 0, 3), iw -> {
            iw.addDocument(Arrays.asList(new IntPoint("number", 7), new SortedNumericDocValuesField("number", 7)));
            iw.addDocument(Arrays.asList(new IntPoint("number", 1), new SortedNumericDocValuesField("number", 2)));
            iw.addDocument(Arrays.asList(new IntPoint("number", 3), new SortedNumericDocValuesField("number", 3)));
        }, avg -> {
            assertEquals(2.5, avg.getValue(), 0);
        });
    }

    public void testQueryFiltersAll() throws IOException {
        testCase(IntPoint.newRangeQuery("number", -1, 0), iw -> {
            iw.addDocument(Arrays.asList(new IntPoint("number", 7), new SortedNumericDocValuesField("number", 7)));
            iw.addDocument(Arrays.asList(new IntPoint("number", 1), new SortedNumericDocValuesField("number", 2)));
            iw.addDocument(Arrays.asList(new IntPoint("number", 3), new SortedNumericDocValuesField("number", 7)));
        }, avg -> {
            assertEquals(Double.NaN, avg.getValue(), 0);
        });
    }

    public void testSummationAccuracy() throws IOException {
        // Summing up a normal array and expect an accurate value
        double[] values = new double[]{0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.9, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7};
        verifyAvgOfDoubles(values, 0.9, 0d);

        // Summing up an array which contains NaN and infinities and expect a result same as naive summation
        int n = randomIntBetween(5, 10);
        values = new double[n];
        double sum = 0;
        for (int i = 0; i < n; i++) {
            values[i] = frequently()
                ? randomFrom(Double.NaN, Double.NEGATIVE_INFINITY, Double.POSITIVE_INFINITY)
                : randomDoubleBetween(Double.MIN_VALUE, Double.MAX_VALUE, true);
            sum += values[i];
        }
        verifyAvgOfDoubles(values, sum / n, 1e-10);

        // Summing up some big double values and expect infinity result
        n = randomIntBetween(5, 10);
        double[] largeValues = new double[n];
        for (int i = 0; i < n; i++) {
            largeValues[i] = Double.MAX_VALUE;
        }
        verifyAvgOfDoubles(largeValues, Double.POSITIVE_INFINITY, 0d);

        for (int i = 0; i < n; i++) {
            largeValues[i] = -Double.MAX_VALUE;
        }
        verifyAvgOfDoubles(largeValues, Double.NEGATIVE_INFINITY, 0d);
    }

    private void verifyAvgOfDoubles(double[] values, double expected, double delta) throws IOException {
        testCase(new MatchAllDocsQuery(),
            iw -> {
                for (double value : values) {
                    iw.addDocument(singleton(new NumericDocValuesField("number", NumericUtils.doubleToSortableLong(value))));
                }
            },
            avg -> assertEquals(expected, avg.getValue(), delta),
            NumberFieldMapper.NumberType.DOUBLE
        );
    }

    private void testCase(Query query,
                          CheckedConsumer<RandomIndexWriter, IOException> buildIndex,
                          Consumer<InternalAvg> verify) throws IOException {
        testCase(query, buildIndex, verify, NumberFieldMapper.NumberType.LONG);
    }

    private void testCase(Query query,
                          CheckedConsumer<RandomIndexWriter, IOException> buildIndex,
                          Consumer<InternalAvg> verify,
                          NumberFieldMapper.NumberType fieldNumberType) throws IOException {
        Directory directory = newDirectory();
        RandomIndexWriter indexWriter = new RandomIndexWriter(random(), directory);
        buildIndex.accept(indexWriter);
        indexWriter.close();

        IndexReader indexReader = DirectoryReader.open(directory);
        IndexSearcher indexSearcher = newSearcher(indexReader, true, true);

        AvgAggregationBuilder aggregationBuilder = new AvgAggregationBuilder("_name").field("number");
        MappedFieldType fieldType = new NumberFieldMapper.NumberFieldType(fieldNumberType);
        fieldType.setName("number");

        AvgAggregator aggregator = createAggregator(aggregationBuilder, indexSearcher, fieldType);
        aggregator.preCollection();
        indexSearcher.search(query, aggregator);
        aggregator.postCollection();
        verify.accept((InternalAvg) aggregator.buildAggregation(0L));

        indexReader.close();
        directory.close();
    }
}
