/*
 * 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;

import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.search.aggregations.support.AggregationContext;
import org.elasticsearch.xcontent.XContentBuilder;

import java.io.IOException;
import java.util.Collections;
import java.util.Map;
import java.util.Objects;

/**
 * Base implementation of a {@link AggregationBuilder}.
 */
public abstract class AbstractAggregationBuilder<AB extends AbstractAggregationBuilder<AB>> extends AggregationBuilder {

    protected Map<String, Object> metadata;

    /**
     * Constructs a new aggregation builder.
     *
     * @param name  The aggregation name
     */
    public AbstractAggregationBuilder(String name) {
        super(name);
    }

    protected AbstractAggregationBuilder(
        AbstractAggregationBuilder<AB> clone,
        AggregatorFactories.Builder factoriesBuilder,
        Map<String, Object> metadata
    ) {
        super(clone, factoriesBuilder);
        this.metadata = metadata;
    }

    /**
     * Read from a stream.
     */
    protected AbstractAggregationBuilder(StreamInput in) throws IOException {
        super(in.readString());
        factoriesBuilder = new AggregatorFactories.Builder(in);
        metadata = in.readMap();
    }

    @Override
    public final void writeTo(StreamOutput out) throws IOException {
        out.writeString(name);
        factoriesBuilder.writeTo(out);
        out.writeGenericMap(metadata);
        doWriteTo(out);
    }

    protected abstract void doWriteTo(StreamOutput out) throws IOException;

    @SuppressWarnings("unchecked")
    @Override
    public AB subAggregation(AggregationBuilder aggregation) {
        if (aggregation == null) {
            throw new IllegalArgumentException("[aggregation] must not be null: [" + name + "]");
        }
        factoriesBuilder.addAggregator(aggregation);
        return (AB) this;
    }

    /**
     * Add a sub aggregation to this aggregation.
     */
    @SuppressWarnings("unchecked")
    @Override
    public AB subAggregation(PipelineAggregationBuilder aggregation) {
        if (aggregation == null) {
            throw new IllegalArgumentException("[aggregation] must not be null: [" + name + "]");
        }
        factoriesBuilder.addPipelineAggregator(aggregation);
        return (AB) this;
    }

    /**
     * Registers sub-factories with this factory. The sub-factory will be
     * responsible for the creation of sub-aggregators under the aggregator
     * created by this factory.
     *
     * @param subFactories
     *            The sub-factories
     * @return this factory (fluent interface)
     */
    @SuppressWarnings("unchecked")
    @Override
    public AB subAggregations(AggregatorFactories.Builder subFactories) {
        if (subFactories == null) {
            throw new IllegalArgumentException("[subFactories] must not be null: [" + name + "]");
        }
        this.factoriesBuilder = subFactories;
        return (AB) this;
    }

    @SuppressWarnings("unchecked")
    @Override
    public AB setMetadata(Map<String, Object> metadata) {
        if (metadata == null) {
            throw new IllegalArgumentException("[metadata] must not be null: [" + name + "]");
        }
        this.metadata = metadata;
        return (AB) this;
    }

    @Override
    public Map<String, Object> getMetadata() {
        return metadata == null ? null : Collections.unmodifiableMap(metadata);
    }

    @Override
    public final String getWriteableName() {
        // We always use the type of the aggregation as the writeable name
        return getType();
    }

    @Override
    public final AggregatorFactory build(AggregationContext context, AggregatorFactory parent) throws IOException {
        AggregatorFactory factory = doBuild(context, parent, factoriesBuilder);
        context.getUsageService().incAggregationUsage(getType(), factory.getStatsSubtype());
        return factory;
    }

    protected abstract AggregatorFactory doBuild(
        AggregationContext context,
        AggregatorFactory parent,
        AggregatorFactories.Builder subfactoriesBuilder
    ) throws IOException;

    @Override
    public final XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
        builder.startObject(name);

        if (this.metadata != null) {
            builder.field("meta", this.metadata);
        }
        builder.field(getType());
        internalXContent(builder, params);

        if (factoriesBuilder != null && (factoriesBuilder.count()) > 0) {
            builder.field("aggregations");
            factoriesBuilder.toXContent(builder, params);
        }
        return builder.endObject();
    }

    protected abstract XContentBuilder internalXContent(XContentBuilder builder, Params params) throws IOException;

    @Override
    public int hashCode() {
        return Objects.hash(factoriesBuilder, metadata, name);
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        @SuppressWarnings("unchecked")
        AbstractAggregationBuilder<AB> other = (AbstractAggregationBuilder<AB>) obj;

        return Objects.equals(name, other.name)
            && Objects.equals(metadata, other.metadata)
            && Objects.equals(factoriesBuilder, other.factoriesBuilder);
    }
}
