/*
 * 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
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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
 * under the License.
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/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.search.aggregations.pipeline;

import org.opensearch.action.index.IndexRequestBuilder;
import org.opensearch.action.search.SearchResponse;
import org.opensearch.search.aggregations.bucket.histogram.Histogram;
import org.opensearch.search.aggregations.bucket.histogram.Histogram.Bucket;
import org.opensearch.search.aggregations.bucket.terms.Terms;
import org.opensearch.search.aggregations.bucket.terms.IncludeExclude;
import org.opensearch.search.aggregations.metrics.Sum;
import org.opensearch.search.aggregations.pipeline.BucketHelpers.GapPolicy;
import org.opensearch.search.aggregations.BucketOrder;
import org.opensearch.test.OpenSearchIntegTestCase;

import java.util.ArrayList;
import java.util.List;

import static org.opensearch.common.xcontent.XContentFactory.jsonBuilder;
import static org.opensearch.search.aggregations.AggregationBuilders.histogram;
import static org.opensearch.search.aggregations.AggregationBuilders.sum;
import static org.opensearch.search.aggregations.AggregationBuilders.terms;
import static org.opensearch.search.aggregations.PipelineAggregatorBuilders.minBucket;
import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertAcked;
import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertSearchResponse;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.greaterThan;
import static org.hamcrest.core.IsNull.notNullValue;

@OpenSearchIntegTestCase.SuiteScopeTestCase
public class MinBucketIT extends OpenSearchIntegTestCase {

    private static final String SINGLE_VALUED_FIELD_NAME = "l_value";

    static int numDocs;
    static int interval;
    static int minRandomValue;
    static int maxRandomValue;
    static int numValueBuckets;
    static long[] valueCounts;

    @Override
    public void setupSuiteScopeCluster() throws Exception {
        assertAcked(client().admin().indices().prepareCreate("idx").setMapping("tag", "type=keyword").get());
        createIndex("idx_unmapped");

        numDocs = randomIntBetween(6, 20);
        interval = randomIntBetween(2, 5);

        minRandomValue = 0;
        maxRandomValue = 20;

        numValueBuckets = ((maxRandomValue - minRandomValue) / interval) + 1;
        valueCounts = new long[numValueBuckets];

        List<IndexRequestBuilder> builders = new ArrayList<>();

        for (int i = 0; i < numDocs; i++) {
            int fieldValue = randomIntBetween(minRandomValue, maxRandomValue);
            builders.add(
                client().prepareIndex("idx")
                    .setSource(
                        jsonBuilder().startObject()
                            .field(SINGLE_VALUED_FIELD_NAME, fieldValue)
                            .field("tag", "tag" + (i % interval))
                            .endObject()
                    )
            );
            final int bucket = (fieldValue / interval); // + (fieldValue < 0 ? -1 : 0) - (minRandomValue / interval - 1);
            valueCounts[bucket]++;
        }

        assertAcked(prepareCreate("empty_bucket_idx").setMapping(SINGLE_VALUED_FIELD_NAME, "type=integer"));
        for (int i = 0; i < 2; i++) {
            builders.add(
                client().prepareIndex("empty_bucket_idx")
                    .setId("" + i)
                    .setSource(jsonBuilder().startObject().field(SINGLE_VALUED_FIELD_NAME, i * 2).endObject())
            );
        }
        indexRandom(true, builders);
        ensureSearchable();
    }

    public void testDocCountTopLevel() throws Exception {
        SearchResponse response = client().prepareSearch("idx")
            .addAggregation(
                histogram("histo").field(SINGLE_VALUED_FIELD_NAME).interval(interval).extendedBounds(minRandomValue, maxRandomValue)
            )
            .addAggregation(minBucket("min_bucket", "histo>_count"))
            .get();

        assertSearchResponse(response);

        Histogram histo = response.getAggregations().get("histo");
        assertThat(histo, notNullValue());
        assertThat(histo.getName(), equalTo("histo"));
        List<? extends Bucket> buckets = histo.getBuckets();
        assertThat(buckets.size(), equalTo(numValueBuckets));

        List<String> minKeys = new ArrayList<>();
        double minValue = Double.POSITIVE_INFINITY;
        for (int i = 0; i < numValueBuckets; ++i) {
            Histogram.Bucket bucket = buckets.get(i);
            assertThat(bucket, notNullValue());
            assertThat(((Number) bucket.getKey()).longValue(), equalTo((long) i * interval));
            assertThat(bucket.getDocCount(), equalTo(valueCounts[i]));
            if (bucket.getDocCount() < minValue) {
                minValue = bucket.getDocCount();
                minKeys = new ArrayList<>();
                minKeys.add(bucket.getKeyAsString());
            } else if (bucket.getDocCount() == minValue) {
                minKeys.add(bucket.getKeyAsString());
            }
        }

        InternalBucketMetricValue minBucketValue = response.getAggregations().get("min_bucket");
        assertThat(minBucketValue, notNullValue());
        assertThat(minBucketValue.getName(), equalTo("min_bucket"));
        assertThat(minBucketValue.value(), equalTo(minValue));
        assertThat(minBucketValue.keys(), equalTo(minKeys.toArray(new String[0])));
    }

    public void testDocCountAsSubAgg() throws Exception {
        SearchResponse response = client().prepareSearch("idx")
            .addAggregation(
                terms("terms").field("tag")
                    .order(BucketOrder.key(true))
                    .subAggregation(
                        histogram("histo").field(SINGLE_VALUED_FIELD_NAME).interval(interval).extendedBounds(minRandomValue, maxRandomValue)
                    )
                    .subAggregation(minBucket("min_bucket", "histo>_count"))
            )
            .get();

        assertSearchResponse(response);

        Terms terms = response.getAggregations().get("terms");
        assertThat(terms, notNullValue());
        assertThat(terms.getName(), equalTo("terms"));
        List<? extends Terms.Bucket> termsBuckets = terms.getBuckets();
        assertThat(termsBuckets.size(), equalTo(interval));

        for (int i = 0; i < interval; ++i) {
            Terms.Bucket termsBucket = termsBuckets.get(i);
            assertThat(termsBucket, notNullValue());
            assertThat((String) termsBucket.getKey(), equalTo("tag" + (i % interval)));

            Histogram histo = termsBucket.getAggregations().get("histo");
            assertThat(histo, notNullValue());
            assertThat(histo.getName(), equalTo("histo"));
            List<? extends Bucket> buckets = histo.getBuckets();

            List<String> minKeys = new ArrayList<>();
            double minValue = Double.POSITIVE_INFINITY;
            for (int j = 0; j < numValueBuckets; ++j) {
                Histogram.Bucket bucket = buckets.get(j);
                assertThat(bucket, notNullValue());
                assertThat(((Number) bucket.getKey()).longValue(), equalTo((long) j * interval));
                if (bucket.getDocCount() < minValue) {
                    minValue = bucket.getDocCount();
                    minKeys = new ArrayList<>();
                    minKeys.add(bucket.getKeyAsString());
                } else if (bucket.getDocCount() == minValue) {
                    minKeys.add(bucket.getKeyAsString());
                }
            }

            InternalBucketMetricValue minBucketValue = termsBucket.getAggregations().get("min_bucket");
            assertThat(minBucketValue, notNullValue());
            assertThat(minBucketValue.getName(), equalTo("min_bucket"));
            assertThat(minBucketValue.value(), equalTo(minValue));
            assertThat(minBucketValue.keys(), equalTo(minKeys.toArray(new String[0])));
        }
    }

    public void testMetricTopLevel() throws Exception {
        SearchResponse response = client().prepareSearch("idx")
            .addAggregation(terms("terms").field("tag").subAggregation(sum("sum").field(SINGLE_VALUED_FIELD_NAME)))
            .addAggregation(minBucket("min_bucket", "terms>sum"))
            .get();

        assertSearchResponse(response);

        Terms terms = response.getAggregations().get("terms");
        assertThat(terms, notNullValue());
        assertThat(terms.getName(), equalTo("terms"));
        List<? extends Terms.Bucket> buckets = terms.getBuckets();
        assertThat(buckets.size(), equalTo(interval));

        List<String> minKeys = new ArrayList<>();
        double minValue = Double.POSITIVE_INFINITY;
        for (int i = 0; i < interval; ++i) {
            Terms.Bucket bucket = buckets.get(i);
            assertThat(bucket, notNullValue());
            assertThat((String) bucket.getKey(), equalTo("tag" + (i % interval)));
            assertThat(bucket.getDocCount(), greaterThan(0L));
            Sum sum = bucket.getAggregations().get("sum");
            assertThat(sum, notNullValue());
            if (sum.value() < minValue) {
                minValue = sum.value();
                minKeys = new ArrayList<>();
                minKeys.add(bucket.getKeyAsString());
            } else if (sum.value() == minValue) {
                minKeys.add(bucket.getKeyAsString());
            }
        }

        InternalBucketMetricValue minBucketValue = response.getAggregations().get("min_bucket");
        assertThat(minBucketValue, notNullValue());
        assertThat(minBucketValue.getName(), equalTo("min_bucket"));
        assertThat(minBucketValue.value(), equalTo(minValue));
        assertThat(minBucketValue.keys(), equalTo(minKeys.toArray(new String[0])));
    }

    public void testMetricAsSubAgg() throws Exception {
        SearchResponse response = client().prepareSearch("idx")
            .addAggregation(
                terms("terms").field("tag")
                    .order(BucketOrder.key(true))
                    .subAggregation(
                        histogram("histo").field(SINGLE_VALUED_FIELD_NAME)
                            .interval(interval)
                            .extendedBounds(minRandomValue, maxRandomValue)
                            .subAggregation(sum("sum").field(SINGLE_VALUED_FIELD_NAME))
                    )
                    .subAggregation(minBucket("min_bucket", "histo>sum"))
            )
            .get();

        assertSearchResponse(response);

        Terms terms = response.getAggregations().get("terms");
        assertThat(terms, notNullValue());
        assertThat(terms.getName(), equalTo("terms"));
        List<? extends Terms.Bucket> termsBuckets = terms.getBuckets();
        assertThat(termsBuckets.size(), equalTo(interval));

        for (int i = 0; i < interval; ++i) {
            Terms.Bucket termsBucket = termsBuckets.get(i);
            assertThat(termsBucket, notNullValue());
            assertThat((String) termsBucket.getKey(), equalTo("tag" + (i % interval)));

            Histogram histo = termsBucket.getAggregations().get("histo");
            assertThat(histo, notNullValue());
            assertThat(histo.getName(), equalTo("histo"));
            List<? extends Bucket> buckets = histo.getBuckets();

            List<String> minKeys = new ArrayList<>();
            double minValue = Double.POSITIVE_INFINITY;
            for (int j = 0; j < numValueBuckets; ++j) {
                Histogram.Bucket bucket = buckets.get(j);
                assertThat(bucket, notNullValue());
                assertThat(((Number) bucket.getKey()).longValue(), equalTo((long) j * interval));
                if (bucket.getDocCount() != 0) {
                    Sum sum = bucket.getAggregations().get("sum");
                    assertThat(sum, notNullValue());
                    if (sum.value() < minValue) {
                        minValue = sum.value();
                        minKeys = new ArrayList<>();
                        minKeys.add(bucket.getKeyAsString());
                    } else if (sum.value() == minValue) {
                        minKeys.add(bucket.getKeyAsString());
                    }
                }
            }

            InternalBucketMetricValue minBucketValue = termsBucket.getAggregations().get("min_bucket");
            assertThat(minBucketValue, notNullValue());
            assertThat(minBucketValue.getName(), equalTo("min_bucket"));
            assertThat(minBucketValue.value(), equalTo(minValue));
            assertThat(minBucketValue.keys(), equalTo(minKeys.toArray(new String[0])));
        }
    }

    public void testMetricAsSubAggWithInsertZeros() throws Exception {
        SearchResponse response = client().prepareSearch("idx")
            .addAggregation(
                terms("terms").field("tag")
                    .order(BucketOrder.key(true))
                    .subAggregation(
                        histogram("histo").field(SINGLE_VALUED_FIELD_NAME)
                            .interval(interval)
                            .extendedBounds(minRandomValue, maxRandomValue)
                            .subAggregation(sum("sum").field(SINGLE_VALUED_FIELD_NAME))
                    )
                    .subAggregation(minBucket("min_bucket", "histo>sum").gapPolicy(GapPolicy.INSERT_ZEROS))
            )
            .get();

        assertSearchResponse(response);

        Terms terms = response.getAggregations().get("terms");
        assertThat(terms, notNullValue());
        assertThat(terms.getName(), equalTo("terms"));
        List<? extends Terms.Bucket> termsBuckets = terms.getBuckets();
        assertThat(termsBuckets.size(), equalTo(interval));

        for (int i = 0; i < interval; ++i) {
            Terms.Bucket termsBucket = termsBuckets.get(i);
            assertThat(termsBucket, notNullValue());
            assertThat((String) termsBucket.getKey(), equalTo("tag" + (i % interval)));

            Histogram histo = termsBucket.getAggregations().get("histo");
            assertThat(histo, notNullValue());
            assertThat(histo.getName(), equalTo("histo"));
            List<? extends Bucket> buckets = histo.getBuckets();

            List<String> minKeys = new ArrayList<>();
            double minValue = Double.POSITIVE_INFINITY;
            for (int j = 0; j < numValueBuckets; ++j) {
                Histogram.Bucket bucket = buckets.get(j);
                assertThat(bucket, notNullValue());
                assertThat(((Number) bucket.getKey()).longValue(), equalTo((long) j * interval));
                Sum sum = bucket.getAggregations().get("sum");
                assertThat(sum, notNullValue());
                if (sum.value() < minValue) {
                    minValue = sum.value();
                    minKeys = new ArrayList<>();
                    minKeys.add(bucket.getKeyAsString());
                } else if (sum.value() == minValue) {
                    minKeys.add(bucket.getKeyAsString());
                }
            }

            InternalBucketMetricValue minBucketValue = termsBucket.getAggregations().get("min_bucket");
            assertThat(minBucketValue, notNullValue());
            assertThat(minBucketValue.getName(), equalTo("min_bucket"));
            assertThat(minBucketValue.value(), equalTo(minValue));
            assertThat(minBucketValue.keys(), equalTo(minKeys.toArray(new String[0])));
        }
    }

    public void testNoBuckets() throws Exception {
        SearchResponse response = client().prepareSearch("idx")
            .addAggregation(
                terms("terms").field("tag")
                    .includeExclude(new IncludeExclude(null, "tag.*"))
                    .subAggregation(sum("sum").field(SINGLE_VALUED_FIELD_NAME))
            )
            .addAggregation(minBucket("min_bucket", "terms>sum"))
            .get();

        assertSearchResponse(response);

        Terms terms = response.getAggregations().get("terms");
        assertThat(terms, notNullValue());
        assertThat(terms.getName(), equalTo("terms"));
        List<? extends Terms.Bucket> buckets = terms.getBuckets();
        assertThat(buckets.size(), equalTo(0));

        InternalBucketMetricValue minBucketValue = response.getAggregations().get("min_bucket");
        assertThat(minBucketValue, notNullValue());
        assertThat(minBucketValue.getName(), equalTo("min_bucket"));
        assertThat(minBucketValue.value(), equalTo(Double.POSITIVE_INFINITY));
        assertThat(minBucketValue.keys(), equalTo(new String[0]));
    }

    public void testNested() throws Exception {
        SearchResponse response = client().prepareSearch("idx")
            .addAggregation(
                terms("terms").field("tag")
                    .order(BucketOrder.key(true))
                    .subAggregation(
                        histogram("histo").field(SINGLE_VALUED_FIELD_NAME).interval(interval).extendedBounds(minRandomValue, maxRandomValue)
                    )
                    .subAggregation(minBucket("min_histo_bucket", "histo>_count"))
            )
            .addAggregation(minBucket("min_terms_bucket", "terms>min_histo_bucket"))
            .get();

        assertSearchResponse(response);

        Terms terms = response.getAggregations().get("terms");
        assertThat(terms, notNullValue());
        assertThat(terms.getName(), equalTo("terms"));
        List<? extends Terms.Bucket> termsBuckets = terms.getBuckets();
        assertThat(termsBuckets.size(), equalTo(interval));

        List<String> minTermsKeys = new ArrayList<>();
        double minTermsValue = Double.POSITIVE_INFINITY;
        for (int i = 0; i < interval; ++i) {
            Terms.Bucket termsBucket = termsBuckets.get(i);
            assertThat(termsBucket, notNullValue());
            assertThat((String) termsBucket.getKey(), equalTo("tag" + (i % interval)));

            Histogram histo = termsBucket.getAggregations().get("histo");
            assertThat(histo, notNullValue());
            assertThat(histo.getName(), equalTo("histo"));
            List<? extends Bucket> buckets = histo.getBuckets();

            List<String> minHistoKeys = new ArrayList<>();
            double minHistoValue = Double.POSITIVE_INFINITY;
            for (int j = 0; j < numValueBuckets; ++j) {
                Histogram.Bucket bucket = buckets.get(j);
                assertThat(bucket, notNullValue());
                assertThat(((Number) bucket.getKey()).longValue(), equalTo((long) j * interval));
                if (bucket.getDocCount() < minHistoValue) {
                    minHistoValue = bucket.getDocCount();
                    minHistoKeys = new ArrayList<>();
                    minHistoKeys.add(bucket.getKeyAsString());
                } else if (bucket.getDocCount() == minHistoValue) {
                    minHistoKeys.add(bucket.getKeyAsString());
                }
            }

            InternalBucketMetricValue minBucketValue = termsBucket.getAggregations().get("min_histo_bucket");
            assertThat(minBucketValue, notNullValue());
            assertThat(minBucketValue.getName(), equalTo("min_histo_bucket"));
            assertThat(minBucketValue.value(), equalTo(minHistoValue));
            assertThat(minBucketValue.keys(), equalTo(minHistoKeys.toArray(new String[0])));
            if (minHistoValue < minTermsValue) {
                minTermsValue = minHistoValue;
                minTermsKeys = new ArrayList<>();
                minTermsKeys.add(termsBucket.getKeyAsString());
            } else if (minHistoValue == minTermsValue) {
                minTermsKeys.add(termsBucket.getKeyAsString());
            }
        }

        InternalBucketMetricValue minBucketValue = response.getAggregations().get("min_terms_bucket");
        assertThat(minBucketValue, notNullValue());
        assertThat(minBucketValue.getName(), equalTo("min_terms_bucket"));
        assertThat(minBucketValue.value(), equalTo(minTermsValue));
        assertThat(minBucketValue.keys(), equalTo(minTermsKeys.toArray(new String[0])));
    }
}