/*
 * 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.
 */

package org.elasticsearch.search.aggregations.pipeline;

import org.apache.lucene.document.Document;
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.IndexSearcher;
import org.apache.lucene.search.MatchAllDocsQuery;
import org.apache.lucene.search.MatchNoDocsQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.store.Directory;
import org.elasticsearch.common.CheckedConsumer;
import org.elasticsearch.index.mapper.DateFieldMapper;
import org.elasticsearch.index.mapper.MappedFieldType;
import org.elasticsearch.index.mapper.NumberFieldMapper;
import org.elasticsearch.search.aggregations.AggregationBuilder;
import org.elasticsearch.search.aggregations.AggregatorTestCase;
import org.elasticsearch.search.aggregations.InternalAggregation;
import org.elasticsearch.search.aggregations.bucket.histogram.DateHistogramAggregationBuilder;
import org.elasticsearch.search.aggregations.bucket.histogram.DateHistogramInterval;
import org.elasticsearch.search.aggregations.bucket.histogram.Histogram;
import org.elasticsearch.search.aggregations.bucket.histogram.HistogramAggregationBuilder;
import org.elasticsearch.search.aggregations.metrics.avg.AvgAggregationBuilder;
import org.elasticsearch.search.aggregations.metrics.avg.InternalAvg;
import org.elasticsearch.search.aggregations.metrics.sum.Sum;
import org.elasticsearch.search.aggregations.metrics.sum.SumAggregationBuilder;
import org.elasticsearch.search.aggregations.pipeline.cumulativesum.CumulativeSumPipelineAggregationBuilder;
import org.elasticsearch.search.aggregations.pipeline.derivative.DerivativePipelineAggregationBuilder;

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

import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.core.IsNull.notNullValue;

public class CumulativeSumAggregatorTests extends AggregatorTestCase {

    private static final String HISTO_FIELD = "histo";
    private static final String VALUE_FIELD = "value_field";

    private static final List<String> datasetTimes = Arrays.asList(
        "2017-01-01T01:07:45",
        "2017-01-02T03:43:34",
        "2017-01-03T04:11:00",
        "2017-01-04T05:11:31",
        "2017-01-05T08:24:05",
        "2017-01-06T13:09:32",
        "2017-01-07T13:47:43",
        "2017-01-08T16:14:34",
        "2017-01-09T17:09:50",
        "2017-01-10T22:55:46");

    private static final List<Integer> datasetValues = Arrays.asList(1,2,3,4,5,6,7,8,9,10);

    public void testSimple() throws IOException {
        Query query = new MatchAllDocsQuery();

        DateHistogramAggregationBuilder aggBuilder = new DateHistogramAggregationBuilder("histo");
        aggBuilder.dateHistogramInterval(DateHistogramInterval.DAY).field(HISTO_FIELD);
        aggBuilder.subAggregation(new AvgAggregationBuilder("the_avg").field(VALUE_FIELD));
        aggBuilder.subAggregation(new CumulativeSumPipelineAggregationBuilder("cusum", "the_avg"));

        executeTestCase(query, aggBuilder, histogram -> {
            assertEquals(10, ((Histogram)histogram).getBuckets().size());
            List<? extends Histogram.Bucket> buckets = ((Histogram)histogram).getBuckets();
            double sum = 0.0;
            for (Histogram.Bucket bucket : buckets) {
                sum += ((InternalAvg) (bucket.getAggregations().get("the_avg"))).value();
                assertThat(((InternalSimpleValue) (bucket.getAggregations().get("cusum"))).value(), equalTo(sum));
            }
        });
    }

    /**
     * First value from a derivative is null, so this makes sure the cusum can handle that
     */
    public void testDerivative() throws IOException {
        Query query = new MatchAllDocsQuery();

        DateHistogramAggregationBuilder aggBuilder = new DateHistogramAggregationBuilder("histo");
        aggBuilder.dateHistogramInterval(DateHistogramInterval.DAY).field(HISTO_FIELD);
        aggBuilder.subAggregation(new AvgAggregationBuilder("the_avg").field(VALUE_FIELD));
        aggBuilder.subAggregation(new DerivativePipelineAggregationBuilder("the_deriv", "the_avg"));
        aggBuilder.subAggregation(new CumulativeSumPipelineAggregationBuilder("cusum", "the_deriv"));

        executeTestCase(query, aggBuilder, histogram -> {
            assertEquals(10, ((Histogram)histogram).getBuckets().size());
            List<? extends Histogram.Bucket> buckets = ((Histogram)histogram).getBuckets();
            double sum = 0.0;
            for (int i = 0; i < buckets.size(); i++) {
                if (i == 0) {
                    assertThat(((InternalSimpleValue)(buckets.get(i).getAggregations().get("cusum"))).value(), equalTo(0.0));
                } else {
                    sum += 1.0;
                    assertThat(((InternalSimpleValue)(buckets.get(i).getAggregations().get("cusum"))).value(), equalTo(sum));
                }
            }
        });
    }

    public void testDocCount() throws IOException {
        Query query = new MatchAllDocsQuery();

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

        int minRandomValue = 0;
        int maxRandomValue = 20;

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

        HistogramAggregationBuilder aggBuilder = new HistogramAggregationBuilder("histo")
            .field(VALUE_FIELD)
            .interval(interval)
            .extendedBounds(minRandomValue, maxRandomValue);
        aggBuilder.subAggregation(new CumulativeSumPipelineAggregationBuilder("cusum", "_count"));

        executeTestCase(query, aggBuilder, histogram -> {
            List<? extends Histogram.Bucket> buckets = ((Histogram)histogram).getBuckets();

            assertThat(buckets.size(), equalTo(numValueBuckets));

            double sum = 0;
            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]));
                sum += bucket.getDocCount();
                InternalSimpleValue cumulativeSumValue = bucket.getAggregations().get("cusum");
                assertThat(cumulativeSumValue, notNullValue());
                assertThat(cumulativeSumValue.getName(), equalTo("cusum"));
                assertThat(cumulativeSumValue.value(), equalTo(sum));
            }
        }, indexWriter -> {
            Document document = new Document();

            for (int i = 0; i < numDocs; i++) {
                int fieldValue = randomIntBetween(minRandomValue, maxRandomValue);
                document.add(new NumericDocValuesField(VALUE_FIELD, fieldValue));
                final int bucket = (fieldValue / interval);
                valueCounts[bucket]++;

                indexWriter.addDocument(document);
                document.clear();
            }
        });
    }

    public void testMetric() throws IOException {
        Query query = new MatchAllDocsQuery();

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

        int minRandomValue = 0;
        int maxRandomValue = 20;

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

        HistogramAggregationBuilder aggBuilder = new HistogramAggregationBuilder("histo")
            .field(VALUE_FIELD)
            .interval(interval)
            .extendedBounds(minRandomValue, maxRandomValue);
        aggBuilder.subAggregation(new SumAggregationBuilder("sum").field(VALUE_FIELD));
        aggBuilder.subAggregation(new CumulativeSumPipelineAggregationBuilder("cusum", "sum"));

        executeTestCase(query, aggBuilder, histogram -> {
            List<? extends Histogram.Bucket> buckets = ((Histogram)histogram).getBuckets();

            assertThat(buckets.size(), equalTo(numValueBuckets));

            double bucketSum = 0;
            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));
                Sum sum = bucket.getAggregations().get("sum");
                assertThat(sum, notNullValue());
                bucketSum += sum.value();

                InternalSimpleValue sumBucketValue = bucket.getAggregations().get("cusum");
                assertThat(sumBucketValue, notNullValue());
                assertThat(sumBucketValue.getName(), equalTo("cusum"));
                assertThat(sumBucketValue.value(), equalTo(bucketSum));
            }
        }, indexWriter -> {
            Document document = new Document();

            for (int i = 0; i < numDocs; i++) {
                int fieldValue = randomIntBetween(minRandomValue, maxRandomValue);
                document.add(new NumericDocValuesField(VALUE_FIELD, fieldValue));
                final int bucket = (fieldValue / interval);
                valueCounts[bucket]++;

                indexWriter.addDocument(document);
                document.clear();
            }
        });
    }

    public void testNoBuckets() throws IOException {
        int numDocs = randomIntBetween(6, 20);
        int interval = randomIntBetween(2, 5);

        int minRandomValue = 0;
        int maxRandomValue = 20;

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

        Query query = new MatchNoDocsQuery();

        HistogramAggregationBuilder aggBuilder = new HistogramAggregationBuilder("histo")
            .field(VALUE_FIELD)
            .interval(interval);
        aggBuilder.subAggregation(new SumAggregationBuilder("sum").field(VALUE_FIELD));
        aggBuilder.subAggregation(new CumulativeSumPipelineAggregationBuilder("cusum", "sum"));

        executeTestCase(query, aggBuilder, histogram -> {
            List<? extends Histogram.Bucket> buckets = ((Histogram)histogram).getBuckets();

            assertThat(buckets.size(), equalTo(0));

        }, indexWriter -> {
            Document document = new Document();

            for (int i = 0; i < numDocs; i++) {
                int fieldValue = randomIntBetween(minRandomValue, maxRandomValue);
                document.add(new NumericDocValuesField(VALUE_FIELD, fieldValue));
                final int bucket = (fieldValue / interval);
                valueCounts[bucket]++;

                indexWriter.addDocument(document);
                document.clear();
            }
        });
    }

    @SuppressWarnings("unchecked")
    private void executeTestCase(Query query, AggregationBuilder aggBuilder, Consumer<InternalAggregation> verify) throws IOException {
        executeTestCase(query, aggBuilder, verify, indexWriter -> {
            Document document = new Document();
            int counter = 0;
            for (String date : datasetTimes) {
                if (frequently()) {
                    indexWriter.commit();
                }

                long instant = asLong(date);
                document.add(new SortedNumericDocValuesField(HISTO_FIELD, instant));
                document.add(new NumericDocValuesField(VALUE_FIELD, datasetValues.get(counter)));
                indexWriter.addDocument(document);
                document.clear();
                counter += 1;
            }
        });
    }

    @SuppressWarnings("unchecked")
    private void executeTestCase(Query query, AggregationBuilder aggBuilder, Consumer<InternalAggregation> verify,
                                 CheckedConsumer<RandomIndexWriter, IOException> setup) throws IOException {

        try (Directory directory = newDirectory()) {
            try (RandomIndexWriter indexWriter = new RandomIndexWriter(random(), directory)) {
               setup.accept(indexWriter);
            }

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

                DateFieldMapper.Builder builder = new DateFieldMapper.Builder("_name");
                DateFieldMapper.DateFieldType fieldType = builder.fieldType();
                fieldType.setHasDocValues(true);
                fieldType.setName(HISTO_FIELD);

                MappedFieldType valueFieldType = new NumberFieldMapper.NumberFieldType(NumberFieldMapper.NumberType.LONG);
                valueFieldType.setHasDocValues(true);
                valueFieldType.setName("value_field");

                InternalAggregation histogram;
                histogram = searchAndReduce(indexSearcher, query, aggBuilder, new MappedFieldType[]{fieldType, valueFieldType});
                verify.accept(histogram);
            }
        }
    }

    private static long asLong(String dateTime) {
        return DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parser().parseDateTime(dateTime).getMillis();
    }
}
