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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;

import com.google.common.collect.ImmutableMap;
import org.elasticsearch.common.collect.MapBuilder;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.xcontent.XContentParser;
import org.elasticsearch.search.SearchParseException;
import org.elasticsearch.search.internal.SearchContext;

import java.io.IOException;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * A registry for all the aggregator parser, also servers as the main parser for the aggregations module
 */
public class AggregatorParsers {

    public static final Pattern VALID_AGG_NAME = Pattern.compile("[^\\[\\]>]+");
    private final ImmutableMap parsers;


    /**
     * Constructs the AggregatorParsers out of all the given parsers
     *
     * @param parsers The available aggregator parsers (dynamically injected by the {@link org.elasticsearch.search.aggregations.AggregationModule}).
     */
    @Inject
    public AggregatorParsers(Set parsers) {
        MapBuilder builder = MapBuilder.newMapBuilder();
        for (Aggregator.Parser parser : parsers) {
            builder.put(parser.type(), parser);
        }
        this.parsers = builder.immutableMap();
    }

    /**
     * Returns the parser that is registered under the given aggregation type.
     *
     * @param type  The aggregation type
     * @return      The parser associated with the given aggregation type.
     */
    public Aggregator.Parser parser(String type) {
        return parsers.get(type);
    }

    /**
     * Parses the aggregation request recursively generating aggregator factories in turn.
     *
     * @param parser    The input xcontent that will be parsed.
     * @param context   The search context.
     *
     * @return          The parsed aggregator factories.
     *
     * @throws IOException When parsing fails for unknown reasons.
     */
    public AggregatorFactories parseAggregators(XContentParser parser, SearchContext context) throws IOException {
        return parseAggregators(parser, context, 0);
    }


    private AggregatorFactories parseAggregators(XContentParser parser, SearchContext context, int level) throws IOException {
        Matcher validAggMatcher = VALID_AGG_NAME.matcher("");
        AggregatorFactories.Builder factories = new AggregatorFactories.Builder();

        XContentParser.Token token = null;
        while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
            if (token != XContentParser.Token.FIELD_NAME) {
                throw new SearchParseException(context, "Unexpected token " + token + " in [aggs]: aggregations definitions must start with the name of the aggregation.");
            }
            final String aggregationName = parser.currentName();
            if (!validAggMatcher.reset(aggregationName).matches()) {
                throw new SearchParseException(context, "Invalid aggregation name [" + aggregationName + "]. Aggregation names must be alpha-numeric and can only contain '_' and '-'");
            }

            token = parser.nextToken();
            if (token != XContentParser.Token.START_OBJECT) {
                throw new SearchParseException(context, "Aggregation definition for [" + aggregationName + " starts with a [" + token + "], expected a [" + XContentParser.Token.START_OBJECT + "].");
            }

            AggregatorFactory factory = null;
            AggregatorFactories subFactories = null;

            while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
                if (token != XContentParser.Token.FIELD_NAME) {
                    throw new SearchParseException(context, "Expected [" + XContentParser.Token.FIELD_NAME + "] under a [" + XContentParser.Token.START_OBJECT + "], but got a [" + token + "] in [" + aggregationName + "]");
                }
                final String fieldName = parser.currentName();

                token = parser.nextToken();
                if (token != XContentParser.Token.START_OBJECT) {
                    throw new SearchParseException(context, "Expected [" + XContentParser.Token.START_OBJECT + "] under [" + fieldName + "], but got a [" + token + "] in [" + aggregationName + "]");
                }

                switch (fieldName) {
                    case "aggregations":
                    case "aggs":
                        if (subFactories != null) {
                            throw new SearchParseException(context, "Found two sub aggregation definitions under [" + aggregationName + "]");
                        }
                        subFactories = parseAggregators(parser, context, level+1);
                        break;
                    default:
                        if (factory != null) {
                            throw new SearchParseException(context, "Found two aggregation type definitions in [" + aggregationName + "]: [" + factory.type + "] and [" + fieldName + "]");
                        }
                        Aggregator.Parser aggregatorParser = parser(fieldName);
                        if (aggregatorParser == null) {
                            throw new SearchParseException(context, "Could not find aggregator type [" + fieldName + "] in [" + aggregationName + "]");
                        }
                        factory = aggregatorParser.parse(aggregationName, parser, context);
                }
            }

            if (factory == null) {
                throw new SearchParseException(context, "Missing definition for aggregation [" + aggregationName + "]");
            }

            if (subFactories != null) {
                factory.subFactories(subFactories);
            }

            if (level == 0) {
                factory.validate();
            }

            factories.add(factory);
        }

        return factories.build();
    }

}