/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */

package org.elasticsearch.search.aggregations.bucket.terms;

import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.search.DocValueFormat;
import org.elasticsearch.search.aggregations.bucket.terms.heuristic.SignificanceHeuristic;
import org.elasticsearch.xcontent.XContentBuilder;

import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.function.Function;
import java.util.stream.Collectors;

public abstract class InternalMappedSignificantTerms<
    A extends InternalMappedSignificantTerms<A, B>,
    B extends InternalSignificantTerms.Bucket<B>> extends InternalSignificantTerms<A, B> {

    protected final DocValueFormat format;
    protected final long subsetSize;
    protected final long supersetSize;
    protected final SignificanceHeuristic significanceHeuristic;
    protected final List<B> buckets;
    protected Map<String, B> bucketMap;

    protected InternalMappedSignificantTerms(
        String name,
        int requiredSize,
        long minDocCount,
        Map<String, Object> metadata,
        DocValueFormat format,
        long subsetSize,
        long supersetSize,
        SignificanceHeuristic significanceHeuristic,
        List<B> buckets
    ) {
        super(name, requiredSize, minDocCount, metadata);
        this.format = format;
        this.buckets = buckets;
        this.subsetSize = subsetSize;
        this.supersetSize = supersetSize;
        this.significanceHeuristic = significanceHeuristic;
    }

    protected InternalMappedSignificantTerms(StreamInput in, Bucket.Reader<B> bucketReader) throws IOException {
        super(in);
        format = in.readNamedWriteable(DocValueFormat.class);
        subsetSize = in.readVLong();
        supersetSize = in.readVLong();
        significanceHeuristic = in.readNamedWriteable(SignificanceHeuristic.class);
        buckets = in.readList(stream -> bucketReader.read(stream, subsetSize, supersetSize, format));
    }

    @Override
    protected final void writeTermTypeInfoTo(StreamOutput out) throws IOException {
        out.writeNamedWriteable(format);
        out.writeVLong(subsetSize);
        out.writeVLong(supersetSize);
        out.writeNamedWriteable(significanceHeuristic);
        out.writeList(buckets);
    }

    @Override
    public Iterator<SignificantTerms.Bucket> iterator() {
        return buckets.stream().map(bucket -> (SignificantTerms.Bucket) bucket).toList().iterator();
    }

    @Override
    public List<B> getBuckets() {
        return buckets;
    }

    @Override
    public B getBucketByKey(String term) {
        if (bucketMap == null) {
            bucketMap = buckets.stream().collect(Collectors.toMap(InternalSignificantTerms.Bucket::getKeyAsString, Function.identity()));
        }
        return bucketMap.get(term);
    }

    @Override
    protected long getSubsetSize() {
        return subsetSize;
    }

    @Override
    protected long getSupersetSize() {
        return supersetSize;
    }

    @Override
    public SignificanceHeuristic getSignificanceHeuristic() {
        return significanceHeuristic;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        if (super.equals(obj) == false) return false;

        InternalMappedSignificantTerms<?, ?> that = (InternalMappedSignificantTerms<?, ?>) obj;
        return Objects.equals(format, that.format)
            && subsetSize == that.subsetSize
            && supersetSize == that.supersetSize
            && Objects.equals(significanceHeuristic, that.significanceHeuristic)
            && Objects.equals(buckets, that.buckets)
            && Objects.equals(bucketMap, that.bucketMap);
    }

    @Override
    public int hashCode() {
        return Objects.hash(super.hashCode(), format, subsetSize, supersetSize, significanceHeuristic, buckets, bucketMap);
    }

    @Override
    public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
        builder.field(CommonFields.DOC_COUNT.getPreferredName(), subsetSize);
        builder.field(BG_COUNT, supersetSize);
        builder.startArray(CommonFields.BUCKETS.getPreferredName());
        for (Bucket<?> bucket : buckets) {
            // There is a condition (presumably when only one shard has a bucket?) where reduce is not called
            // and I end up with buckets that contravene the user's min_doc_count criteria in my reducer
            if (bucket.subsetDf >= minDocCount) {
                bucket.toXContent(builder, params);
            }
        }
        builder.endArray();
        return builder;
    }
}
