/*
 * Copyright 2014-present Open Networking Foundation
 *
 * Licensed 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.onosproject.cluster;

import java.time.Instant;
import java.util.Optional;
import java.util.Set;

import org.joda.time.DateTime;
import org.onlab.util.Tools;
import org.onosproject.core.Version;
import org.onosproject.event.ListenerService;

/**
 * Service for obtaining information about the individual nodes within the controller cluster.
 */
public interface ClusterService extends ListenerService<ClusterEvent, ClusterEventListener> {

    /**
     * Returns the local controller node.
     *
     * @return local controller node
     */
    ControllerNode getLocalNode();

    /**
     * Returns the set of current cluster members.
     *
     * @return set of cluster members
     */
    Set<ControllerNode> getNodes();

    /**
     * Returns the set of consensus nodes.
     *
     * @return the set of consensus nodes
     */
    Set<Node> getConsensusNodes();

    /**
     * Returns the specified controller node.
     *
     * @param nodeId controller node identifier
     * @return controller node
     */
    ControllerNode getNode(NodeId nodeId);

    /**
     * Returns the availability state of the specified controller node. Note
     * that this does not imply that all the core and application components
     * have been fully activated; only that the node has joined the cluster.
     *
     * @param nodeId controller node identifier
     * @return availability state
     */
    ControllerNode.State getState(NodeId nodeId);

    /**
     * Returns the version of the given controller node.
     *
     * @param nodeId controller node identifier
     * @return controller version
     */
    Version getVersion(NodeId nodeId);

    /**
     * Returns the system time when the availability state was last updated.
     *
     * @param nodeId controller node identifier
     * @return system time when the availability state was last updated.
     */
    default Instant getLastUpdatedInstant(NodeId nodeId) {
        return Optional.ofNullable(getLastUpdated(nodeId))
                    .map(DateTime::getMillis)
                    .map(Instant::ofEpochMilli)
                    .orElse(null);
    }

    /**
     * Returns a human readable form of the system time when the availability state was last updated.
     *
     * @param nodeId controller node identifier
     * @return human readable string for system time when the availability state was last updated.
     */
    default String localStatus(NodeId nodeId) {
        Instant lastUpdated = getLastUpdatedInstant(nodeId);
        String timeAgo = "Never";
        if (lastUpdated != null) {
            timeAgo = Tools.timeAgo(lastUpdated.toEpochMilli());
        }
        return timeAgo;
    }

    /**
     * Returns the system time when the availability state was last updated.
     *
     * @param nodeId controller node identifier
     * @return system time when the availability state was last updated.
     *
     * @deprecated in 1.12.0
     */
    @Deprecated
    default DateTime getLastUpdated(NodeId nodeId) {
        return Optional.ofNullable(getLastUpdatedInstant(nodeId))
                .map(Instant::toEpochMilli)
                .map(DateTime::new)
                .orElse(null);
    }

}