/*
 * 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.nested;

import org.elasticsearch.TransportVersion;
import org.elasticsearch.common.ParsingException;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.index.mapper.NestedObjectMapper;
import org.elasticsearch.search.aggregations.AbstractAggregationBuilder;
import org.elasticsearch.search.aggregations.AggregationBuilder;
import org.elasticsearch.search.aggregations.AggregatorFactories.Builder;
import org.elasticsearch.search.aggregations.AggregatorFactory;
import org.elasticsearch.search.aggregations.support.AggregationContext;
import org.elasticsearch.xcontent.XContentBuilder;
import org.elasticsearch.xcontent.XContentParser;

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

public class NestedAggregationBuilder extends AbstractAggregationBuilder<NestedAggregationBuilder> {
    public static final String NAME = "nested";

    private final String path;

    /**
     * @param name
     *            the name of this aggregation
     * @param path
     *            the path to use for this nested aggregation. The path must
     *            match the path to a nested object in the mappings.
     */
    public NestedAggregationBuilder(String name, String path) {
        super(name);
        if (path == null) {
            throw new IllegalArgumentException("[path] must not be null: [" + name + "]");
        }
        this.path = path;
    }

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

    @Override
    protected AggregationBuilder shallowCopy(Builder factoriesBuilder, Map<String, Object> metadata) {
        return new NestedAggregationBuilder(this, factoriesBuilder, metadata);
    }

    /**
     * Read from a stream.
     */
    public NestedAggregationBuilder(StreamInput in) throws IOException {
        super(in);
        path = in.readString();
    }

    @Override
    protected void doWriteTo(StreamOutput out) throws IOException {
        out.writeString(path);
    }

    /**
     * Get the path to use for this nested aggregation.
     */
    public String path() {
        return path;
    }

    @Override
    public BucketCardinality bucketCardinality() {
        return BucketCardinality.ONE;
    }

    @Override
    public boolean supportsConcurrentExecution() {
        return false;
    }

    @Override
    protected AggregatorFactory doBuild(AggregationContext context, AggregatorFactory parent, Builder subFactoriesBuilder)
        throws IOException {
        NestedObjectMapper nestedMapper = context.nestedLookup().getNestedMappers().get(path);
        if (nestedMapper == null) {
            // in case the path has been unmapped:
            return new NestedAggregatorFactory(name, null, null, context, parent, subFactoriesBuilder, metadata);
        }

        try {
            NestedObjectMapper parentObjectMapper = context.nestedScope().nextLevel(nestedMapper);
            return new NestedAggregatorFactory(name, parentObjectMapper, nestedMapper, context, parent, subFactoriesBuilder, metadata);
        } finally {
            context.nestedScope().previousLevel();
        }
    }

    @Override
    protected XContentBuilder internalXContent(XContentBuilder builder, Params params) throws IOException {
        builder.startObject();
        builder.field(NestedAggregator.PATH_FIELD.getPreferredName(), path);
        builder.endObject();
        return builder;
    }

    public static NestedAggregationBuilder parse(String aggregationName, XContentParser parser) throws IOException {
        String path = null;

        XContentParser.Token token;
        String currentFieldName = null;
        while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
            if (token == XContentParser.Token.FIELD_NAME) {
                currentFieldName = parser.currentName();
            } else if (token == XContentParser.Token.VALUE_STRING) {
                if (NestedAggregator.PATH_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                    path = parser.text();
                } else {
                    throw new ParsingException(
                        parser.getTokenLocation(),
                        "Unknown key for a " + token + " in [" + aggregationName + "]: [" + currentFieldName + "]."
                    );
                }
            } else {
                throw new ParsingException(parser.getTokenLocation(), "Unexpected token " + token + " in [" + aggregationName + "].");
            }
        }

        if (path == null) {
            // "field" doesn't exist, so we fall back to the context of the ancestors
            throw new ParsingException(parser.getTokenLocation(), "Missing [path] field for nested aggregation [" + aggregationName + "]");
        }

        return new NestedAggregationBuilder(aggregationName, path);
    }

    @Override
    public int hashCode() {
        return Objects.hash(super.hashCode(), path);
    }

    @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;
        NestedAggregationBuilder other = (NestedAggregationBuilder) obj;
        return Objects.equals(path, other.path);
    }

    @Override
    public String getType() {
        return NAME;
    }

    @Override
    public TransportVersion getMinimalSupportedVersion() {
        return TransportVersion.ZERO;
    }
}
