/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * 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
 * under the License.
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/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.search.aggregations.metrics;

import org.opensearch.common.Strings;
import org.opensearch.core.xcontent.ToXContent;
import org.opensearch.core.xcontent.XContentBuilder;
import org.opensearch.common.xcontent.json.JsonXContent;
import org.opensearch.search.DocValueFormat;
import org.opensearch.search.aggregations.Aggregation.CommonFields;
import org.opensearch.search.aggregations.InternalAggregation;
import org.opensearch.test.InternalAggregationTestCase;

import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.function.Predicate;
import java.util.stream.Stream;

import static java.util.stream.Collectors.toList;
import static org.hamcrest.Matchers.equalTo;

public abstract class AbstractPercentilesTestCase<T extends InternalAggregation & Iterable<Percentile>> extends InternalAggregationTestCase<
    T> {
    @Override
    protected T createTestInstance(String name, Map<String, Object> metadata) {
        return createTestInstance(name, metadata, randomBoolean(), randomNumericDocValueFormat(), randomPercents(false));
    }

    @Override
    protected List<T> randomResultsToReduce(String name, int size) {
        boolean keyed = randomBoolean();
        DocValueFormat format = randomNumericDocValueFormat();
        double[] percents = randomPercents(false);
        return Stream.generate(() -> createTestInstance(name, null, keyed, format, percents)).limit(size).collect(toList());
    }

    private T createTestInstance(String name, Map<String, Object> metadata, boolean keyed, DocValueFormat format, double[] percents) {
        int numValues = frequently() ? randomInt(100) : 0;
        double[] values = new double[numValues];
        for (int i = 0; i < numValues; ++i) {
            values[i] = randomDouble();
        }
        return createTestInstance(name, metadata, keyed, format, percents, values);
    }

    protected abstract T createTestInstance(
        String name,
        Map<String, Object> metadata,
        boolean keyed,
        DocValueFormat format,
        double[] percents,
        double[] values
    );

    protected abstract Class<? extends ParsedPercentiles> implementationClass();

    public void testPercentilesIterators() throws IOException {
        final T aggregation = createTestInstance();
        final Iterable<Percentile> parsedAggregation = parseAndAssert(aggregation, false, false);

        Iterator<Percentile> it = aggregation.iterator();
        Iterator<Percentile> parsedIt = parsedAggregation.iterator();
        while (it.hasNext()) {
            assertEquals(it.next(), parsedIt.next());
        }
    }

    public static double[] randomPercents(boolean sorted) {
        List<Double> randomCdfValues = randomSubsetOf(randomIntBetween(1, 7), 0.01d, 0.05d, 0.25d, 0.50d, 0.75d, 0.95d, 0.99d);
        double[] percents = new double[randomCdfValues.size()];
        for (int i = 0; i < randomCdfValues.size(); i++) {
            percents[i] = randomCdfValues.get(i);
        }
        if (sorted) {
            Arrays.sort(percents);
        }
        return percents;
    }

    @Override
    protected Predicate<String> excludePathsFromXContentInsertion() {
        return path -> path.endsWith(CommonFields.VALUES.getPreferredName());
    }

    protected abstract void assertPercentile(T agg, Double value);

    public void testEmptyRanksXContent() throws IOException {
        double[] percents = new double[] { 1, 2, 3 };
        boolean keyed = randomBoolean();
        DocValueFormat docValueFormat = randomNumericDocValueFormat();

        T agg = createTestInstance("test", Collections.emptyMap(), keyed, docValueFormat, percents, new double[0]);

        for (Percentile percentile : agg) {
            Double value = percentile.getValue();
            assertPercentile(agg, value);
        }

        XContentBuilder builder = JsonXContent.contentBuilder().prettyPrint();
        builder.startObject();
        agg.doXContentBody(builder, ToXContent.EMPTY_PARAMS);
        builder.endObject();
        String expected;
        if (keyed) {
            expected = "{\n"
                + "  \"values\" : {\n"
                + "    \"1.0\" : null,\n"
                + "    \"2.0\" : null,\n"
                + "    \"3.0\" : null\n"
                + "  }\n"
                + "}";
        } else {
            expected = "{\n"
                + "  \"values\" : [\n"
                + "    {\n"
                + "      \"key\" : 1.0,\n"
                + "      \"value\" : null\n"
                + "    },\n"
                + "    {\n"
                + "      \"key\" : 2.0,\n"
                + "      \"value\" : null\n"
                + "    },\n"
                + "    {\n"
                + "      \"key\" : 3.0,\n"
                + "      \"value\" : null\n"
                + "    }\n"
                + "  ]\n"
                + "}";
        }

        assertThat(Strings.toString(builder), equalTo(expected));
    }
}