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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.action.search;

import org.elasticsearch.action.OriginalIndices;
import org.elasticsearch.cluster.routing.PlainShardIterator;
import org.elasticsearch.cluster.routing.ShardIterator;
import org.elasticsearch.cluster.routing.ShardRouting;
import org.elasticsearch.common.Nullable;
import org.elasticsearch.index.shard.ShardId;
import org.elasticsearch.search.SearchShardTarget;

import java.util.List;
import java.util.Objects;

/**
 * Extension of {@link PlainShardIterator} used in the search api, which also holds the {@link OriginalIndices}
 * of the search request (useful especially with cross-cluster search, as each cluster has its own set of original indices) as well as
 * the cluster alias.
 * @see OriginalIndices
 */
public final class SearchShardIterator extends PlainShardIterator {

    private final OriginalIndices originalIndices;
    private final String clusterAlias;
    private boolean skip = false;

    /**
     * Creates a {@link PlainShardIterator} instance that iterates over a subset of the given shards
     * this the a given shardId.
     *
     * @param clusterAlias the alias of the cluster where the shard is located
     * @param shardId shard id of the group
     * @param shards  shards to iterate
     * @param originalIndices the indices that the search request originally related to (before any rewriting happened)
     */
    public SearchShardIterator(@Nullable String clusterAlias, ShardId shardId, List shards, OriginalIndices originalIndices) {
        super(shardId, shards);
        this.originalIndices = originalIndices;
        this.clusterAlias = clusterAlias;
    }

    /**
     * Returns the original indices associated with this shard iterator, specifically with the cluster that this shard belongs to.
     */
    public OriginalIndices getOriginalIndices() {
        return originalIndices;
    }

    /**
     * Returns the alias of the cluster where the shard is located.
     */
    @Nullable
    public String getClusterAlias() {
        return clusterAlias;
    }

    /**
     * Creates a new shard target from this iterator, pointing at the node identified by the provided identifier.
     * @see SearchShardTarget
     */
    SearchShardTarget newSearchShardTarget(String nodeId) {
        return new SearchShardTarget(nodeId, shardId(), clusterAlias, originalIndices);
    }

    /**
     * Reset the iterator and mark it as skippable
     * @see #skip()
     */
    void resetAndSkip() {
        reset();
        skip = true;
    }

    /**
     * Returns true if the search execution should skip this shard since it can not match any documents given the query.
     */
    boolean skip() {
        return skip;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        if (super.equals(o) == false) {
            return false;
        }
        SearchShardIterator that = (SearchShardIterator) o;
        return Objects.equals(clusterAlias, that.clusterAlias);
    }

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

    @Override
    public int compareTo(ShardIterator o) {
        int superCompareTo = super.compareTo(o);
        if (superCompareTo != 0 || (o instanceof SearchShardIterator == false)) {
            return superCompareTo;
        }
        SearchShardIterator searchShardIterator = (SearchShardIterator)o;
        if (clusterAlias == null && searchShardIterator.getClusterAlias() == null) {
            return 0;
        }
        if (clusterAlias == null) {
            return -1;
        }
        if (searchShardIterator.getClusterAlias() == null) {
            return 1;
        }
        return clusterAlias.compareTo(searchShardIterator.getClusterAlias());
    }
}