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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.terms;

import org.elasticsearch.common.xcontent.ToXContent;
import org.elasticsearch.search.aggregations.Aggregator;
import org.elasticsearch.search.aggregations.bucket.MultiBucketsAggregation;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;

/**
 * A {@code terms} aggregation. Defines multiple bucket, each associated with a unique term for a specific field.
 * All documents in a bucket has the bucket's term in that field.
 */
public interface Terms extends MultiBucketsAggregation {

    /**
     * A bucket that is associated with a single term
     */
    interface Bucket extends MultiBucketsAggregation.Bucket {

        Number getKeyAsNumber();

        int compareTerm(Terms.Bucket other);

        long getDocCountError();
    }

    /**
     * Return the sorted list of the buckets in this terms aggregation.
     */
    @Override
    List getBuckets();

    /**
     * Get the bucket for the given term, or null if there is no such bucket.
     */
    Bucket getBucketByKey(String term);

    /**
     * Get an upper bound of the error on document counts in this aggregation.
     */
    long getDocCountError();

    /**
     * Return the sum of the document counts of all buckets that did not make
     * it to the top buckets.
     */
    long getSumOfOtherDocCounts();

    /**
     * Determines the order by which the term buckets will be sorted
     */
    abstract class Order implements ToXContent {

        /**
         * @return a bucket ordering strategy that sorts buckets by their document counts (ascending or descending)
         */
        public static Order count(boolean asc) {
            return asc ? InternalOrder.COUNT_ASC : InternalOrder.COUNT_DESC;
        }

        /**
         * @return a bucket ordering strategy that sorts buckets by their terms (ascending or descending)
         */
        public static Order term(boolean asc) {
            return asc ? InternalOrder.TERM_ASC : InternalOrder.TERM_DESC;
        }

        /**
         * Creates a bucket ordering strategy which sorts buckets based on a single-valued calc get
         *
         * @param   path the name of the get
         * @param   asc             The direction of the order (ascending or descending)
         */
        public static Order aggregation(String path, boolean asc) {
            return new InternalOrder.Aggregation(path, asc);
        }

        /**
         * Creates a bucket ordering strategy which sorts buckets based on a multi-valued calc get
         *
         * @param   aggregationName the name of the get
         * @param   metricName       The name of the value of the multi-value get by which the sorting will be applied
         * @param   asc             The direction of the order (ascending or descending)
         */
        public static Order aggregation(String aggregationName, String metricName, boolean asc) {
            return new InternalOrder.Aggregation(aggregationName + "." + metricName, asc);
        }

        /**
         * Creates a bucket ordering strategy which sorts buckets based multiple criteria
         *
         * @param   orders a list of {@link Order} objects to sort on, in order of priority
         */
        public static Order compound(List orders) {
            return new InternalOrder.CompoundOrder(orders);
        }

        /**
         * Creates a bucket ordering strategy which sorts buckets based multiple criteria
         *
         * @param   orders a list of {@link Order} parameters to sort on, in order of priority
         */
        public static Order compound(Order... orders) {
            return compound(Arrays.asList(orders));
        }

        /**
         * @return  A comparator for the bucket based on the given terms aggregator. The comparator is used in two phases:
         *
         *          - aggregation phase, where each shard builds a list of term buckets to be sent to the coordinating node.
         *            In this phase, the passed in aggregator will be the terms aggregator that aggregates the buckets on the
         *            shard level.
         *
         *          - reduce phase, where the coordinating node gathers all the buckets from all the shards and reduces them
         *            to a final bucket list. In this case, the passed in aggregator will be {@code null}
         */
        protected abstract Comparator comparator(Aggregator aggregator);

        abstract byte id();

        @Override
        public abstract int hashCode();

        @Override
        public abstract boolean equals(Object obj);

    }
}