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 * 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.bucket.significant;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.PostingsEnum;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.BooleanClause.Occur;
import org.apache.lucene.search.BooleanQuery;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.util.BytesRef;
import org.elasticsearch.common.ParseField;
import org.elasticsearch.common.lease.Releasable;
import org.elasticsearch.common.lucene.index.FilterableTermsEnum;
import org.elasticsearch.common.lucene.index.FreqTermsEnum;
import org.elasticsearch.index.mapper.MappedFieldType;
import org.elasticsearch.index.query.QueryBuilder;
import org.elasticsearch.search.DocValueFormat;
import org.elasticsearch.search.aggregations.AggregationExecutionException;
import org.elasticsearch.search.aggregations.Aggregator;
import org.elasticsearch.search.aggregations.AggregatorFactories;
import org.elasticsearch.search.aggregations.AggregatorFactory;
import org.elasticsearch.search.aggregations.InternalAggregation;
import org.elasticsearch.search.aggregations.NonCollectingAggregator;
import org.elasticsearch.search.aggregations.bucket.BucketUtils;
import org.elasticsearch.search.aggregations.bucket.significant.heuristics.SignificanceHeuristic;
import org.elasticsearch.search.aggregations.bucket.terms.TermsAggregator;
import org.elasticsearch.search.aggregations.bucket.terms.TermsAggregator.BucketCountThresholds;
import org.elasticsearch.search.aggregations.bucket.terms.support.IncludeExclude;
import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
import org.elasticsearch.search.aggregations.support.ValuesSource;
import org.elasticsearch.search.aggregations.support.ValuesSourceAggregatorFactory;
import org.elasticsearch.search.aggregations.support.ValuesSourceConfig;
import org.elasticsearch.search.internal.SearchContext;

import java.io.IOException;
import java.util.List;
import java.util.Map;

public class SignificantTermsAggregatorFactory extends ValuesSourceAggregatorFactory<ValuesSource, SignificantTermsAggregatorFactory>
        implements Releasable {

    private final IncludeExclude includeExclude;
    private final String executionHint;
    private String indexedFieldName;
    private MappedFieldType fieldType;
    private FilterableTermsEnum termsEnum;
    private int numberOfAggregatorsCreated;
    final Query filter;
    private final int supersetNumDocs;
    private final TermsAggregator.BucketCountThresholds bucketCountThresholds;
    private final SignificanceHeuristic significanceHeuristic;

    public SignificantTermsAggregatorFactory(String name, ValuesSourceConfig<ValuesSource> config, IncludeExclude includeExclude,
            String executionHint, QueryBuilder filterBuilder, TermsAggregator.BucketCountThresholds bucketCountThresholds,
            SignificanceHeuristic significanceHeuristic, SearchContext context, AggregatorFactory<?> parent,
            AggregatorFactories.Builder subFactoriesBuilder, Map<String, Object> metaData) throws IOException {
        super(name, config, context, parent, subFactoriesBuilder, metaData);
        this.includeExclude = includeExclude;
        this.executionHint = executionHint;
        this.filter = filterBuilder == null
                ? null
                : filterBuilder.toFilter(context.getQueryShardContext());
        IndexSearcher searcher = context.searcher();
        this.supersetNumDocs = filter == null
                // Important - need to use the doc count that includes deleted docs
                // or we have this issue: https://github.com/elastic/elasticsearch/issues/7951
                ? searcher.getIndexReader().maxDoc()
                : searcher.count(filter);
        this.bucketCountThresholds = bucketCountThresholds;
        this.significanceHeuristic = significanceHeuristic;
        setFieldInfo(context);

    }

    private void setFieldInfo(SearchContext context) {
        if (!config.unmapped()) {
            this.indexedFieldName = config.fieldContext().field();
            fieldType = context.smartNameFieldType(indexedFieldName);
        }
    }

    /**
     * Get the number of docs in the superset.
     */
    public long getSupersetNumDocs() {
        return supersetNumDocs;
    }

    private FilterableTermsEnum getTermsEnum(String field) throws IOException {
        if (termsEnum != null) {
            return termsEnum;
        }
        IndexReader reader = context.searcher().getIndexReader();
        if (numberOfAggregatorsCreated > 1) {
            termsEnum = new FreqTermsEnum(reader, field, true, false, filter, context.bigArrays());
        } else {
            termsEnum = new FilterableTermsEnum(reader, indexedFieldName, PostingsEnum.NONE, filter);
        }
        return termsEnum;
    }

    private long getBackgroundFrequency(String value) throws IOException {
        Query query = fieldType.termQuery(value, context.getQueryShardContext());
        if (query instanceof TermQuery) {
            // for types that use the inverted index, we prefer using a caching terms
            // enum that will do a better job at reusing index inputs
            Term term = ((TermQuery) query).getTerm();
            FilterableTermsEnum termsEnum = getTermsEnum(term.field());
            if (termsEnum.seekExact(term.bytes())) {
                return termsEnum.docFreq();
            } else {
                return 0;
            }
        }
        // otherwise do it the naive way
        if (filter != null) {
            query = new BooleanQuery.Builder()
                    .add(query, Occur.FILTER)
                    .add(filter, Occur.FILTER)
                    .build();
        }
        return context.searcher().count(query);
    }

    public long getBackgroundFrequency(BytesRef termBytes) throws IOException {
        String value = config.format().format(termBytes);
        return getBackgroundFrequency(value);
    }

    public long getBackgroundFrequency(long termNum) throws IOException {
        String value = config.format().format(termNum);
        return getBackgroundFrequency(value);
    }

    @Override
    protected Aggregator createUnmapped(Aggregator parent, List<PipelineAggregator> pipelineAggregators, Map<String, Object> metaData)
            throws IOException {
        final InternalAggregation aggregation = new UnmappedSignificantTerms(name, bucketCountThresholds.getRequiredSize(),
                bucketCountThresholds.getMinDocCount(), pipelineAggregators, metaData);
        return new NonCollectingAggregator(name, context, parent, pipelineAggregators, metaData) {
            @Override
            public InternalAggregation buildEmptyAggregation() {
                return aggregation;
            }
        };
    }

    @Override
    protected Aggregator doCreateInternal(ValuesSource valuesSource, Aggregator parent, boolean collectsFromSingleBucket,
            List<PipelineAggregator> pipelineAggregators, Map<String, Object> metaData) throws IOException {
        if (collectsFromSingleBucket == false) {
            return asMultiBucketAggregator(this, context, parent);
        }

        numberOfAggregatorsCreated++;
        BucketCountThresholds bucketCountThresholds = new BucketCountThresholds(this.bucketCountThresholds);
        if (bucketCountThresholds.getShardSize() == SignificantTermsAggregationBuilder.DEFAULT_BUCKET_COUNT_THRESHOLDS.getShardSize()) {
            // The user has not made a shardSize selection .
            // Use default heuristic to avoid any wrong-ranking caused by
            // distributed counting
            // but request double the usual amount.
            // We typically need more than the number of "top" terms requested
            // by other aggregations
            // as the significance algorithm is in less of a position to
            // down-select at shard-level -
            // some of the things we want to find have only one occurrence on
            // each shard and as
            // such are impossible to differentiate from non-significant terms
            // at that early stage.
            bucketCountThresholds.setShardSize(2 * BucketUtils.suggestShardSideQueueSize(bucketCountThresholds.getRequiredSize(),
                    context.numberOfShards()));
        }

        if (valuesSource instanceof ValuesSource.Bytes) {
            ExecutionMode execution = null;
            if (executionHint != null) {
                execution = ExecutionMode.fromString(executionHint);
            }
            if (!(valuesSource instanceof ValuesSource.Bytes.WithOrdinals)) {
                execution = ExecutionMode.MAP;
            }
            if (execution == null) {
                if (Aggregator.descendsFromBucketAggregator(parent)) {
                    execution = ExecutionMode.GLOBAL_ORDINALS_HASH;
                } else {
                    execution = ExecutionMode.GLOBAL_ORDINALS;
                }
            }
            assert execution != null;

            DocValueFormat format = config.format();
            if ((includeExclude != null) && (includeExclude.isRegexBased()) && format != DocValueFormat.RAW) {
                throw new AggregationExecutionException("Aggregation [" + name + "] cannot support regular expression style include/exclude "
                        + "settings as they can only be applied to string fields. Use an array of values for include/exclude clauses");
            }

            return execution.create(name, factories, valuesSource, format, bucketCountThresholds, includeExclude, context, parent,
                    significanceHeuristic, this, pipelineAggregators, metaData);
        }

        if ((includeExclude != null) && (includeExclude.isRegexBased())) {
            throw new AggregationExecutionException("Aggregation [" + name + "] cannot support regular expression style include/exclude "
                    + "settings as they can only be applied to string fields. Use an array of numeric values for include/exclude clauses used to filter numeric fields");
        }

        if (valuesSource instanceof ValuesSource.Numeric) {

            if (((ValuesSource.Numeric) valuesSource).isFloatingPoint()) {
                throw new UnsupportedOperationException("No support for examining floating point numerics");
            }
            IncludeExclude.LongFilter longFilter = null;
            if (includeExclude != null) {
                longFilter = includeExclude.convertToLongFilter(config.format());
            }
            return new SignificantLongTermsAggregator(name, factories, (ValuesSource.Numeric) valuesSource, config.format(),
                    bucketCountThresholds, context, parent, significanceHeuristic, this, longFilter, pipelineAggregators,
                    metaData);
        }

        throw new AggregationExecutionException("significant_terms aggregation cannot be applied to field ["
                + config.fieldContext().field() + "]. It can only be applied to numeric or string fields.");
    }

    public enum ExecutionMode {

        MAP(new ParseField("map")) {

            @Override
            Aggregator create(String name, AggregatorFactories factories, ValuesSource valuesSource, DocValueFormat format,
                    TermsAggregator.BucketCountThresholds bucketCountThresholds, IncludeExclude includeExclude,
                    SearchContext aggregationContext, Aggregator parent, SignificanceHeuristic significanceHeuristic,
                    SignificantTermsAggregatorFactory termsAggregatorFactory, List<PipelineAggregator> pipelineAggregators,
                    Map<String, Object> metaData) throws IOException {
                final IncludeExclude.StringFilter filter = includeExclude == null ? null : includeExclude.convertToStringFilter(format);
                return new SignificantStringTermsAggregator(name, factories, valuesSource, format, bucketCountThresholds, filter,
                        aggregationContext, parent, significanceHeuristic, termsAggregatorFactory, pipelineAggregators, metaData);
            }

        },
        GLOBAL_ORDINALS(new ParseField("global_ordinals")) {

            @Override
            Aggregator create(String name, AggregatorFactories factories, ValuesSource valuesSource, DocValueFormat format,
                    TermsAggregator.BucketCountThresholds bucketCountThresholds, IncludeExclude includeExclude,
                    SearchContext aggregationContext, Aggregator parent, SignificanceHeuristic significanceHeuristic,
                    SignificantTermsAggregatorFactory termsAggregatorFactory, List<PipelineAggregator> pipelineAggregators,
                    Map<String, Object> metaData) throws IOException {
                final IncludeExclude.OrdinalsFilter filter = includeExclude == null ? null : includeExclude.convertToOrdinalsFilter(format);
                return new GlobalOrdinalsSignificantTermsAggregator(name, factories,
                        (ValuesSource.Bytes.WithOrdinals.FieldData) valuesSource, format, bucketCountThresholds, filter,
                        aggregationContext, parent, significanceHeuristic, termsAggregatorFactory, pipelineAggregators, metaData);
            }

        },
        GLOBAL_ORDINALS_HASH(new ParseField("global_ordinals_hash")) {

            @Override
            Aggregator create(String name, AggregatorFactories factories, ValuesSource valuesSource, DocValueFormat format,
                    TermsAggregator.BucketCountThresholds bucketCountThresholds, IncludeExclude includeExclude,
                    SearchContext aggregationContext, Aggregator parent, SignificanceHeuristic significanceHeuristic,
                    SignificantTermsAggregatorFactory termsAggregatorFactory, List<PipelineAggregator> pipelineAggregators,
                    Map<String, Object> metaData) throws IOException {
                final IncludeExclude.OrdinalsFilter filter = includeExclude == null ? null : includeExclude.convertToOrdinalsFilter(format);
                return new GlobalOrdinalsSignificantTermsAggregator.WithHash(name, factories,
                        (ValuesSource.Bytes.WithOrdinals.FieldData) valuesSource, format, bucketCountThresholds, filter,
                        aggregationContext, parent, significanceHeuristic, termsAggregatorFactory, pipelineAggregators, metaData);
            }
        };

        public static ExecutionMode fromString(String value) {
            for (ExecutionMode mode : values()) {
                if (mode.parseField.match(value)) {
                    return mode;
                }
            }
            throw new IllegalArgumentException("Unknown `execution_hint`: [" + value + "], expected any of " + values());
        }

        private final ParseField parseField;

        ExecutionMode(ParseField parseField) {
            this.parseField = parseField;
        }

        abstract Aggregator create(String name, AggregatorFactories factories, ValuesSource valuesSource,  DocValueFormat format,
                TermsAggregator.BucketCountThresholds bucketCountThresholds, IncludeExclude includeExclude,
                SearchContext aggregationContext, Aggregator parent, SignificanceHeuristic significanceHeuristic,
                SignificantTermsAggregatorFactory termsAggregatorFactory, List<PipelineAggregator> pipelineAggregators,
                Map<String, Object> metaData) throws IOException;

        @Override
        public String toString() {
            return parseField.getPreferredName();
        }
    }

    @Override
    public void close() {
        try {
            if (termsEnum instanceof Releasable) {
                ((Releasable) termsEnum).close();
            }
        } finally {
            termsEnum = null;
        }
    }
}
