/*
 * 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.discovery;

import org.elasticsearch.ElasticsearchException;
import org.elasticsearch.cluster.ClusterChangedEvent;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.common.Nullable;
import org.elasticsearch.common.component.LifecycleComponent;
import org.elasticsearch.common.io.stream.StreamInput;

import java.io.IOException;

/**
 * A pluggable module allowing to implement discovery of other nodes, publishing of the cluster
 * state to all nodes, electing a master of the cluster that raises cluster state change
 * events.
 */
public interface Discovery extends LifecycleComponent {

    /**
     * Publish all the changes to the cluster from the master (can be called just by the master). The publish
     * process should apply this state to the master as well!
     *
     * The {@link AckListener} allows to keep track of the ack received from nodes, and verify whether
     * they updated their own cluster state or not.
     *
     * The method is guaranteed to throw a {@link FailedToCommitClusterStateException} if the change is not committed and should be rejected.
     * Any other exception signals the something wrong happened but the change is committed.
     */
    void publish(ClusterChangedEvent clusterChangedEvent, AckListener ackListener);

    interface AckListener {
        void onNodeAck(DiscoveryNode node, @Nullable Exception e);
        void onTimeout();
    }

    class FailedToCommitClusterStateException extends ElasticsearchException {

        public FailedToCommitClusterStateException(StreamInput in) throws IOException {
            super(in);
        }

        public FailedToCommitClusterStateException(String msg, Object... args) {
            super(msg, args);
        }

        public FailedToCommitClusterStateException(String msg, Throwable cause, Object... args) {
            super(msg, cause, args);
        }
    }

    /**
     * @return stats about the discovery
     */
    DiscoveryStats stats();

    /**
     * Triggers the first join cycle
     */
    void startInitialJoin();

}