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package io.dropwizard.elasticsearch.health;

import com.codahale.metrics.health.HealthCheck;
import com.google.common.collect.ImmutableList;
import org.elasticsearch.action.admin.indices.exists.indices.IndicesExistsResponse;
import org.elasticsearch.client.Client;

import java.util.List;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

/**
 * A {@link HealthCheck} which checks if one or more indices exist in Elasticsearch.
 *
 * @see Admin Indices Indices Exists
 */
public class EsIndexExistsHealthCheck extends HealthCheck {
    private final Client client;
    private final String[] indices;

    /**
     * Construct a new Elasticsearch index exists health check.
     *
     * @param client  an Elasticsearch {@link Client} instance connected to the cluster
     * @param indices a {@link List} of indices in Elasticsearch which should be checked
     * @throws IllegalArgumentException if {@code indices} was {@literal null} or empty
     */
    public EsIndexExistsHealthCheck(Client client, List indices) {
        checkArgument(!indices.isEmpty(), "At least one index must be given");

        this.client = checkNotNull(client);
        this.indices = checkNotNull(indices.toArray(new String[indices.size()]));
    }

    /**
     * Construct a new Elasticsearch index exists health check.
     *
     * @param client    an Elasticsearch {@link org.elasticsearch.client.Client} instance connected to the cluster
     * @param indexName the index in Elasticsearch which should be checked
     */
    public EsIndexExistsHealthCheck(Client client, String indexName) {
        this(client, ImmutableList.of(indexName));
    }

    /**
     * Perform a check of the number of documents in the Elasticsearch indices.
     *
     * @return if the Elasticsearch indices exist, a healthy {@link com.codahale.metrics.health.HealthCheck.Result};
     *         otherwise, an unhealthy {@link com.codahale.metrics.health.HealthCheck.Result} with a descriptive error
     *         message or exception
     * @throws Exception if there is an unhandled error during the health check; this will result in
     *                   a failed health check
     */
    @Override
    protected Result check() throws Exception {
        final IndicesExistsResponse indicesExistsResponse = client.admin().indices().prepareExists(indices).get();

        if (indicesExistsResponse.isExists()) {
            return Result.healthy();
        } else {
            return Result.unhealthy("One or more indices do not exist.");
        }
    }
}